Series 2 Bose Stereo Improvement Build Thread - RX8Club.com



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Old 05-31-2013, 12:26 PM   #1
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Series 2 Bose Stereo Improvement Build Thread

[EDIT]

I am editing the OP to start with lessons learned to help readers get to the point without having to read the entire thread. The original first post is at the end of this edited portion.

-- If I had it to do over again, all I would do is limited sound dampening, add the subwoofer and amp to the trunk, and swap the front tweeters for the Alpine SPS-110TW I ended up with. --

LESSONS LEARNED

0. Consider that the RX-8 cabin size and shape (and leather if you have it) conspire to create a challenging audio environment. Add the road noise and exhaust drone (and Fletcher-Munson curve) to the mix, and things get very challenging. You need to resign yourself to the fact that things will not sound so great above 30mph no matter what you do unless you commit to serious quiet treatment of the car, which will be very expensive and add quite a lot of weight.

1. Sound dampening. If you are 'blessed' with the Bose stereo and don't want to rip the whole thing out, the first thing you should consider is dropping $50 to $150 on Damplifier Pro or Dynamat Extreme. These products absorb vibration energy, which helps diminish noise and create a better, more inert enclosure for each speaker. Treatment of the front doors to deaden the resonant frequencies of the sheet metal improves the sound of the Bose woofers. They will sound deeper, tighter, more focused, punchier, and louder. They will not sound awesome, and it is hard to quantify how much better they will sound, but they will sound better. Treatment of the rear deck for the same deadening effect as well as plugging all the holes not used for fasteners or ventilation will similarly improve the sound of the rear speakers. It is a royal pain in the butt, but start here and do a good job of it. You may find you need to do nothing else. I used 20 square feet of Damplifer and 4 square feet of Dynamat in my installation, but you could get away with less if you ignore the trunk and back seat pans. Buy 20 square feet, treat the front doors and rear deck first, then use any leftovers elsewhere in the car.

2. Many people replace the front tweeters to obtain some high frequency clarity. This is not a bad idea, but you need to be aware of some things. The main thing to consider is the Bose tweeters use a 22uF bass blocking capacitor, which sets the crossover frequency at around 1800Hz with a 6dB slope. That is low for a tweeter, which means the 'twidler' is actually handling a good deal of the mids. If you replace it with the wrong aftermarket tweeter, you will end up with a hole in your midrange in the front soundstage. That may be OK if you can fill that hole from the rear, but mids are directional, which may make things sound strange--or more specifically, cause you to feel your ears are being pulled to the back of the car. I initially chose the Infinity 10.9t, which has a fairly high published crossover point of 3500Hz. So I decided to live with a sizable midrange hole between 1800 and 3500Hz. This turned out to be a mistake on my part, which cost me the price of a new set of tweeters and a new set of sail panels in the end. I eventually installed a pair of Alpine S Series SPS-110TW tweeters in my car to replace the Infinity 10.9t tweeters, and they completely solved my midrange hole problem. The Alpine tweeters feature an unusually low crossover point of 1000Hz with a 12dB slope. A 6dB slope would blend better, but 12 works.

3. The rear speakers represent an interesting case. They sound pretty bad without treating the rear deck as described above. But they do improve after treating the deck. You may not need to replace them. If you should decide to do that, there are obviously some considerations. You may be tempted to impedance match the factory speakers (2 Ohms) with your replacements. Don't do it. The Bose speakers are quite inefficient (no one knows the actual specs), which means they are not very loud per Watt of signal fed to them. Aftermarket 2 Ohm speakers are very efficient. The prominent contenders are Infinity Kappa and some Infinity Reference models. They run a very respectable 95ish dB sensitivity. That means they are at least twice as loud (more like 4x) as the factory speakers, and they will swamp the volume of the front speakers. Further, they tend to need more power than the Bose amp can deliver to get their cones moving, and there is the matter of the strange EQ curve the Bose amp sends them. They will sound bright, brash, and loud back there. And the Bose amp will run hotter than before for some reason. Instead, choose 4 Ohm speakers with a sensitivity of no more than 90dB. If I could choose, I would go for 87dB. To my ears, that sensitivity rating would provide a perfect volume match to the front speakers. As an added bonus, the Bose amp will run much cooler. You may also be tempted to chase speakers with very low bass extension, but this is not necessary and not worth the money, as the Bose amp sends a signal with shelved bass to the rear fills, because they seem to consider the fronts to be the bass drivers. I ended up using Alpine SPE-6090 coaxials, which have near the aforementioned specs and provide an excellent factory fit. I tried 3 other sets of speakers (read below) before finding these Alpines on blowout at my local Best Buy. They are actually dirt cheap on the Net. And they sound great as rear fills. I would not use them for my primary listening position, but I have no complaints about using them back there. Even with these speakers, I tend to fade between 1 and 3 clicks to the front depending on the music.

4. Bass. The Bose system does not have it in spite of having a pair of 9" woofers in the doors. You can improve the bass response of the system by applying Damplifier Pro or Dynamat Extreme as described above. You may not need to do anything beyond that, so do it first. If you do decide to improve upon things in this area, you have a lot of options. I can't go through all of them here. What I can say is that I decided to go to my standby, which is a JL Audio sub in a sealed enclosure with at least 300W of continuous power from a mid-grade amp. Even though I went for a cheaper model sub than I usually do (I normally buy their higher model and build my own enclosure), I cannot find a reason to complain about what I have done. It really kicks for the music I like (classic rock, rock, blues, jazz, modern country, pop (in that order)).

In short, you may be able to meet your goals my simply treating the car to make a better environment for audio, which improves the sound of the Bose drivers. If that is not enough, start by replacing the front tweeters with Alpine soft domes from the S or R series. From there, consider adding some bass with one of the many available options. If you are still unsatisfied, consider replacing the rear fills with Alpine E or S series 6x9s.

Cost of my build:

Alpine tweeters $50
Alpine 6x9s $60
JL Audio sub $150
Alpine amp $150
Damplifier $75
Dynamat Ext $40
Install parts $30

Total $555 plus shipping and taxes

[ORIGINAL POST]

Hi All! Long time lurker but short time poster here. I found a 2011 Grand Touring with a 6SMT with only 9K miles last fall and have been enjoying the heck out of it since then.

The time always comes in the life of a Bose owner to do something about the dreadful audio. I have actually almost finished improving the Bose system, but I will write this thread as a narrative as if I am starting from scratch to make it more beneficial to the community. I will also break the thread up into several posts, where each will deal with a single topic or subject matter. It will take me a day or two to finish it since I have other work to do. Perhaps a mod will move this thread to the Series 2 Audio section.

I spent a great deal of time reading this forum (especially the S1 information since there is not much S2 info out there) and collecting information on how to improve the factory system without replacing it. The decision to not replace it was made with resale value and cost being the primary drivers.

Like most of you, I recognize the signature Bose sound and do not like it. The audio spectrum is clearly missing detailed high frequencies and clear, tight, punchy low frequencies. Highs and lows are the first things to address. Having a good deal of experience working with car audio in the past, I have some natural concerns about achieving good sound in a cabin this size and shape, and with leather seats. I am also afraid Bose may have built in a smiley face EQ curve somewhere to compensate for their overly midrangey speakers. These two concerns could add up to be a recipe for disaster. We shall see.

[to be continued after my afternoon meetings]

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Old 05-31-2013, 07:21 PM   #2
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First things first. Here is the patient.





Other than the obvious goal of dramatically improving the sound quality of the factory stereo, my other overarching goal is to preserve the factory look of the system. I don't want anyone to know anything was done unless they look under the rear deck and read the labels on the speaker magnets. Nothing should show. And any subwoofer I might use should be removable and not leave a trace.

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Old 05-31-2013, 07:25 PM   #3
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Now to talk specifics about the audio work.

The first order of business is to address the lack of high frequency extension and the lack of detail and clarity in the upper registers. My approach to that--like many before me--is to replace the tweeters in the front door sails.

There are some considerations here. First, the Bose tweeters are advertised to be 2" in diameter. Second, they run at 4 Ohms. Third, they are apparently wired in parallel with a 0.5 Ohm mid-bass driver, which presents 0.44 Ohms to the theoretical amp. But there are individual amps in the doors with unknown qualities. Fourth, Bose calls this a mid-high frequency driver, which means it must carry a good deal of the midrange spectrum. That latter consideration is not necessarily a bad thing since the upper mids and high frequencies do the most to set the sound stage. They should be closer to the listener's ear. Fifth, we do not know how high into the mids the 9" drivers go since Bose never publishes any specs about their products.

I decided to try to find a high quality tweeter from a manufacturer I like, that is larger than the common 1" offerings, that runs at 4 Ohms, and that reaches lower than most. The closest thing I could find to that tweeter is the 10.9t from Infinity. It meets all my criteria except that is runs at 2 Ohms. Two Ohms should be OK since it only drops the total load down to 0.4 Ohms (assuming the speaker loads are in parallel, which I bet they are not. I am willing to bet the front woofer amps merely tap the speaker level signal and amplify it further.). It may make the tweeter a little louder, but that is hard to say since we do not know the sensitivity rating on the Bose tweeter. The 10.9t's sensitivity is 93dB, and its frequency response is 3.5 to 35KHz. The 3.5K lower limit is lower than most, but may not be low enough to blend with the Bose 9" driver without leaving a hole in the mids. The high sensitivity makes it a relatively loud speaker. Hmmm...



I'm going for it.

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Old 05-31-2013, 08:03 PM   #4
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Fifty dollars and one week later, I had my tweeters. The sail panels came out of the doors easily. One just firmly grasps and pulls straight back. The factory tweeters had 22uF capacitors (oddly attached to the negative terminal), which sets the crossover point at about 1800Hz--quite a bit lower than the replacement tweeters. Uh oh.

Here is what the stock tweeters look like (mounting screws already removed).



Test fitting the new tweeter. It happens that the plastic body of the tweeter fits flush with the cup in the sail panel. One thing I did not account for was the massive crossover unit. I assumed this would be like most and just include a capacitor. I should have known better with Kappas. I could have just scrapped the crossover and pulled an appropriate cap from my inventory, but there is a reason they used an inductor coil (second order crossover), and I decided Infinity's engineers are smarter than I am. I should try to use their crossover if at all possible.



Here is the crossover removed from its housing. It is big, but not unmanageable. I think. I hope.



My approach to mounting the tweeter was to notch its plastic housing with a Dremel cutting wheel and slide #6 stainless washers into the notches. That made a good mechanical mount. I also glued it in with a small bead of Welder glue, which is great for higher temperature applications like car interiors.

I desoldered the speaker terminals from the crossover boards and soldered speaker wire directly to them to further reduce the size of the crossovers. With that done, they just fit into the sail panels. I glued them down with the same glue and waited 24 hours for the glue to dry.

One thing I did not like about these tweeters is the method for attaching wires. There is a tiny Allen wrench included for use in turning tiny Allen head set screws to hold the wires. The wrench and screw heads all strip easily--preventing a tight connection. I did the best I could and glued the wires in from the back for good measure.



They look factory.



Then I soldered them in.



I don't have a picture of it, but I also wedged a little acoustic foam into each sail panel before popping it back in to hold things in place in case the glue decides to give at some point. It might keep things from rattling should that ever happen.

Wire colors for the Series 2 tweeters are:

Left
Blue/White+ Blue/Black-

Right
Yellow/White+ Yellow/Black-

Sound results. I was a little discouraged on the way to work the first day. They new tweeters were extremely bright and almost brash sounding. I thought I had chosen poorly. But I also knew speakers take time to break in, and things should improve. Things did improve. By day 3, they had calmed down and were sounding very good.

There is a noticeable hole in the midrange just like I thought there might be. But the rear fills can fix that right? Right?! RIGHT?!

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Old 05-31-2013, 08:28 PM   #5
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Now for the rear fills. Considerations here are the factory speakers are 2 Ohms and appear to run in parallel with 4 Ohm tweeters for a total of 1.3 Ohms seen by the amp. And there is limited room under the factory deck panels for speaker mounting height. Two Ohm speakers should work fine here, as I do not plan to use the rear tweeter. Close enough. And maybe the slightly higher impedance will help tame the high sensitivity rating of the new speakers to help them volume-blend with the front.

I read that people were successfully using Infinity Kappa 69x.7i speakers in the rear deck with a factory look. They run at 2 Ohms and have a sensitivity rating of 95dB, which is very high. These should be very efficient speakers and should sound very good. There is some worry they will swamp the front speakers with this level of efficiency. Worth a try anyway considering what they cost now.

I found a pair of new old stock 693.7is for $80 on eBay and bought them. Upon taking them out of the package, I found the mid/tweeter tower to be extremely tall and worried about how they would fit behind the factory panels. As it turns out, they seem to fit fine. I think the towers are touching the grills, but do not seem to be pushing them up. [EDIT: They were touching the grills and vibrating against them.]

To install them, I followed instructions I found here for removing the back seats and rear deck panels. I taped around the speaker openings with weather stripping tape and screwed the new speakers into the old factory holes. I needed to hog out one screw hole in each speaker with a round file to get the holes to line up with the factory holes. I left the factory tweeters in place to plug the holes in the rear deck lids, but disconnected them and taped up their wires to keep them from rattling.

Here are some top photos.





The next problem was to find a place to mount the huge crossovers. Upon removing the trunk lining from each side, I found the rear shock towers to be ideal for crossover mounting with wire ties.



Once wired up and soldered in, the final result looks like this.





How do they sound? Strange at first. Having leaned my lesson from the front tweeters, I waited a week to pass judgement. Still strange.

After 1 week, the front tweeters settled down and left a sizable hole in the midrange. My ears tell me there is a dip between roughly 1K and 4K. The front tweeters had 22uF capacitors, which set their crossover point at about 1800Hz. The new tweeters have a crossover point of 3500Hz. That fits pretty well with what I hear. I was afraid I might be a victim of the leather interior since almost nothing is absorbed (and high frequencies are absorbed first), but things turned out OK up here except for the midrange hole (which I am still hoping will be helped by the rear fills at the risk of anchoring vocals to the back of the car).

The rear speakers also calmed down and started to sound better. There is also a hole in the midrange back there. This dip is lower and lives roughly between 500Hz and 2K. I don't know if this is because of some kind of Bose EQ thing, or because the Bose amp is too weak to adequately power these speakers, or a combination of both. Interestingly, the factory rear tweeter capacitors were 47uF, which means they were rolling off at about 800Hz. So the tweeters were carrying some mid-bass, almost all of the mids, and all of the "highs". But that should not make any difference back there since the Bose tweeters are now disconnected, and the replacement speakers are 3-way with their own dedicated crossovers. Back to the Bose EQ idea and/or the too weak amp idea.

The rear speakers are also much louder than the Bose speakers were and do not blend well with the fronts. This was predicted as a possibility, but I thought it would be OK because of their slightly higher total load. I can compensate for that to some degree by setting the fader 4 to 6 clicks toward the front and turning the volume up 2 clicks.

The Bose amp runs hotter than it did before. Will that be a problem in the long term? I almost hope it will.

Hmmm...

I wonder how things will sound with the sub installed? Prediction: pretty much the same with more oomph.

Rear speaker wire colors are:

Left
+Purple -Pink

Right
+Blue/White -Blue/Black

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Old 05-31-2013, 09:43 PM   #6
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I have had good luck with JL Audio subs since the mid 90s. They are rugged, sound great, and are designed to fit into small sealed enclosures. Sealed boxes are ideal for my needs, as I like fast, accurate, musical bass. I'll take kick over slam any day. I also prefer 10s over 12s, because I find them faster and tighter sounding. I normally build my own sub boxes, but I found this inexpensive JL sub setup (CS110-WXv2) on sale at Crutchfield with no sales tax and free shipping. I measured my trunk space, found it to fit, and ordered it.



Alpine has never disappointed me, and I particularly like their amps for mid-level car audio applications. Crutchfield had the MRP-M500 amp on sale, so I added that to my order too. It will push this sub with 300W RMS at 4 Ohms.



Test fitting the sub enclosure (before I installed the Infinity rears).



The first thing to do was run the 8ga power wire from the battery to the trunk. After some reading here, I decided to run it through the main wiring bundle grommet like many others have done. So I did that, then ran it along the raceway under the door threshold, under the back seat, and into the trunk.













After reinstalling the engine cover, one can only see a little wire peeking out the right side. Otherwise, it is completely stealth.

I did not show this, but I installed a fuse holder at the battery terminal for accident protection. You should always do that to prevent a fire in the unfortunate case of a bad accident or any other possible cause of a short.

The wire I used was 20' of 8ga AudioPipe in black I bought from a local surplus electronics store for 40 cents per foot. This was enough for both the power and ground leads.

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Old 05-31-2013, 09:58 PM   #7
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There is a good ground point under the left side trunk lining. I grounded my amp there while I had it apart to install the 6x9 crossovers.



I don't have photos of it, but I mounted the amp to the back of the sub enclosure and loomed the wiring to make things look neat.

The next thing to do was to tap into the rear preamp inputs to the Bose amp and tap into its turn-on lead. I soldered a 20ga wire into the pink/black wire for the remote and soldered an RCA patch cable into the other appropriate wires to hijack the rear signals for the sub amp. I had debated using an LOC to do this, but my research found all the inexpensive ones to use transformers with limited low end frequency response (~60Hz), which makes them unsuitable for subwoofer use. I could have used an LC2i or LOCB.2 (and still could in the future), but my oscilloscope readings convinced me it would be OK to tap the signals directly. However, I cannot know what that might do to the head unit or Bose amp, because I do not know what additional load the Alpine amp will put on the signal. And the Bose system is rumored to utilize differential inputs to the Bose amp, which are not compatible with all aftermarket amps. My Alpine amp does not advertise compatibility, but seems to work well so far. I am willing to risk my components, but I am not willing to risk yours. Do not do this just because I did it.

I did not take good pictures of the wire tapping process, but I soldered all connections and taped them well. Here is how the finished job looks.



The new wires were taped together and run through the deck to be dropped through a hole in the back left of the trunk. They are completely out of sight. I finished wiring the amp, cleaned things up, and fired up the sub. This pic was taken before the aforementioned tidying.



The signal coming from the Bose HU is very weak. I measured a mean of 50mV, where 2 to 5 Volts are common. That means I had to set the amp gain to 75% to get a good blend. The crossover is currently set to about 75Hz, and the bass boost is set to 0.

How does it sound? Exactly the same with more oomph.

Yesterday, I turned the sub around to fire into the back seat. I get more kick that way and like it better. Unfortunately, it does not look as neat.

Right now, the sub enclosure is simply held in place by friction. I rolled up a black towel and shoved it very tightly between the box and the rear deck. It has not moved a millimeter in the past week or so. I think it is good until I make up my mind about some things and mount it more rigidly (no idea how yet).

Preamp wire colors are:

Left Rear
+ Green/Orange
- Blue/Orange

Right Rear
+ Gray/Red
- Brown/Red

Remote Turn On
+ Pink/Black

More to come...

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Old 05-31-2013, 10:44 PM   #8
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[Ain't got no highs. Ain't got no lows. Must be Bose!]

So here we are.

The highs and lows sound much better. But the mids are basically gone. Can it get more ironic than that?

Some music sounds stellar with what I have done. Norah Jones sounds transcendent. Marc Cohn sounds incredible. Some music sounds meh. Keith Urban and Stevie Ray fit that bill. Some music sounds terrible. Pretty much all 80s metal is awful. Think Bon Jovi sounded bad through boom boxes back in the day? I can top it. Much guitar and the middle spectrum of piano music is greatly diminished. The first two artists I mentioned can overcome that with their vocals and overall musicianship. But artists who rely on guitar music sound completely lost. Van Halen is a total no-go.

What to do?

Options:

1. Assume the rears sound the way they do because of lack of power. Spend $150 to purchase an Alpine 50Wx4 amp to replace the Bose. That will solve the lack of power problem in the rear and the front to rear balance problem. Some tapping and splicing and a custom bracket later, and we have liftoff. Or do we? No. We need new Infinity drivers in the doors to go with the tweeters. Might as well add some Dynamat while we are in there. Let's call this the $300 solution that may or may not work. Now we have liftoff. Right? RIGHT?! If the problem actually lies withe the Bose HU, well, WRONG!

2. Assume the rears sound the way they do because of some unknown as of yet possible Bose EQ thing in the HU. Remove the rear Kappas and reinstall the Bose setup back there. Let the new front tweeters take care of the highs and the new sub take care of the lows. The mids aren't exactly clear, but they are better than nothing, and should more or less blend with the fronts. Sell the Kappas and try to recover $50.

3. Cut all the preamp wires in the trunk and add an EQ between the HU and Bose amp to flatten out the response curve. Nah. Just kidding. Wait. JBL MS-8 anyone?

4. Swear off all music except some jazz performed by hot piano playing chicks and some blues performed by whiskey-voiced piano playing dudes.

How much power does that Bose amp have anyway? They advertise it as a 300W system. If we assume all 300W are in that amp (how many Watts are in the door amps?) and divide by 5 channels, we get 60W per channel. We have to assume that is peak and decrease it by 2/3 to estimate RMS, so it might be 20W RMS per channel. We can also assume it is not high current and is probably made with cheap components, so those 20W are probably on the weak side. Should we call it a good solid 10W RMS per channel amp?

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Old 05-31-2013, 10:56 PM   #9
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I think I just want to look at my car some more while I ponder things.



Pondering... Pondering... Pondering...
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Old 06-01-2013, 06:11 PM   #10
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Here are some photos of the installation thus far. Still not sure what I want to do about the rear 6x9s or the front midrange hole.

















Note the bath towel mounting method in the last 4 shots.

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Old 06-01-2013, 11:32 PM   #11
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One minor update...

I had some time to spend sitting in the car with the sub unplugged and a bunch of reference CDs to play through the stereo. Upon repeatedly fading front to back, I discovered the rear 6x9s are all very loud highs and upper mids with no lows or lower mids. Upon further investigation, I found the speaker cones to barely move no matter what was playing. I think I have found my problem back there, and I should have known better, having used Kappas in the distant past. They just like high power, and the Bose system does not have it. With my memory jogged of my last successful use of Kappas including 75W RMS per channel, I have decided to abandon them in this application.

Honestly, I am a little embarrassed to have typed all this without having had time to do a proper system tuning and listening test. But I am very busy with work and home, and well, I simply have not had time until today.

My solution is to order a pair of Infinity Reference 9632cf speakers and a pair of Alpine SPS-619 speakers to see which set works better. Both are supposed to be made to work well with factory radios. I prefer to use the Infinity speakers since they will more or less timbre match with the Infinity tweeters I have in the door sails, but I had good luck with an older version of the Alpines in my Acura TSX with its factory HU.

But my thinking goes beyond brand and prior experience. The Infinity speakers will be another 2 Ohm attempt with a high sensitivity rating (94dB). That may be fine if more of the SPL originates from the bass and mid-bass regions, which are missing in the Kappas. That possibility is why I chose the 2 way version instead of the 3 way version. The Alpine speakers run at 4 Ohms with a fairly high sensitivity of 90dB. No doubt they will be quieter than the Infinity option, but they may give me just the recipe I need. Since we know that doubling the impedance roughly halves power, and that every 3dB SPL lost roughly halves volume, it may turn out the Alpines are a quarter as loud as the Infinitys. But probably not since volume is not exactly linear, and there are other factors at play. They will probably be roughly half as loud in the real world.

If neither of these options work, I may try a cheap-o pair of JBLs. Last resort is to reinstall the factory Bose setup back there and just live with it along with the improvements I have made with the front tweeters and the sub.

Stay tuned...

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Old 06-07-2013, 10:19 AM   #12
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No pictures to show right now, but I have made some progress on this.

My Infinity Reference and Alpine speakers came in. I installed the Infinity speakers first. They sounded similar to the Kappas--predictably bright and loud. There was no additional bass or lower midrange added to the mix by them. I knew those speakers were a long shot.

The Alpines went in next. They sounded smoother to my ears, but still lacked bass and lower mids. They were also quieter (as they should be) and blended well with the fronts with the fader set to center.

I left one Alpine speaker on the left and reinstalled the Bose setup on the right. I faded to the back and panned left and right and listened to what is going on back there. The Alpine speaker sounded better and slightly louder than the Bose pair, but I was left with the impression that it does not much matter what is used for rear fills as long as the speakers blend well with the front. There simply is not going to be any improvement in the lower registers via speaker replacement. If I had it to do over again, I would probably just leave the Bose speakers back there.

That spawned the next test, which was to use the RCAs I tapped for the subwoofer with a 2 channel 200W stereo receiver to see where the funky Bose EQ thing is happening. The speakers sounded freaking awesome with the Bose amp bypassed, therefore the EQ is happening in the Bose amp, which is a really strange place to add all these filters. I confirmed this by playing the same song through the receiver using my phone as the source. Without replacing the amp, there is nothing that can be done for the rear speakers to improve the low frequencies short of an outboard EQ or DSP of some sort. It's a shame, because the speakers really came alive with my home receiver. The problem with the Kappas was not so much lack of power from the Bose amp, but the EQ curve of the signal sent from the amp. Bose clearly believes the fronts are the bass drivers. The non-Bose RX-8ers out there don't know how good they have it.

The plan now is to exchange the Alpine S series speakers for Alpine E series speakers. The reason is the height of the tweeter towers on the S series. They touch the grills like the Kappas did, and there is some audible vibration happening between them. The E series are Alpine's cheapest speakers, but I no longer think it matters. They will sound similar to the S series, and the tweeter tower should be low enough to fit without touching. Good enough.

The rest of the audio improvements will come from Damplifier. I finished the top of the rear deck last night. I will hit the bottom of the deck, some strategic areas in the trunk, the rear seat pans, and whatever other metal I can easily treat back there. From there, I plan to pay a lot of attention to the front doors. My hope is that Damplifier can dramatically improve the sound of the 9" Bose drivers in the front. I bought 20 square feet of Damplifier, which is 10 1'x2' sheets. I am reserving 4 sheets for the front doors, and using the rest anywhere I can find exposed metal that is easy to get at. That will add only 7lbs of extra weight to the car. I screwed up somehow when I placed my order and did not get Damplifier Pro, so I may have to double up in some areas. Seriously bummed about that.

Last edited by Steve Dallas; 10-18-2013 at 07:17 AM.
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Old 06-07-2013, 03:00 PM   #13
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I saw you posted in the MS-8 thread, but it does seem like that would be a nice solution (being able to compensate for any eq the head unit is doing)... I have ordered a set of replacement speakers for a base (non-bose) system. Will report back on this forum once I have them installed how it sounds. MS-8 will be the next step for me if the speakers alone are not enough of an improvement.
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Old 06-07-2013, 03:36 PM   #14
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Hope it all works out hope to hear some clips in the future when its all done
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Old 06-09-2013, 09:23 AM   #15
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Alpine SPE-6090 speakers are now installed. As it turns out, the E series is the same as the S series except for the magnet material (ferrite vs. strontium) and the crossover capacitor (electrolytic vs. polyester film). I could replace the capacitors with some better ones from my stash, but these measure close to each other, so I won't bother. The E series speakers sound basically the same as the S series back there, and the E series speaker is a better drop-in replacement for this car.

I lined the 6x9 holes with the smallest weather stripping I could get at Home Depot. I also drilled out the mounting holes and used #8 stainless screws, washers, and lock nuts to achieve a more secure fit. Then I applied Damplifier to the rear deck. The deck is filled with useless holes, and I covered any of them that are not used for fasteners or ventilation to try to cut down on the Swiss cheese effect (really bummed about the giant hole where the Bose amp mounts).

These speakers are the perfect solution to my problem. They are almost the correct loudness to achieve center fade with just the right amount of rear fill (I still fade 1 or 2 clicks to the front). And they sound much better than the factory Bose crap. As an added bonus, their 4 Ohm load puts less stress on the Bose amp, which now runs much cooler than it did with the Kappas. Four Ohms and 90dB seem to be near the right combination. 87dB would be better, but let's not get greedy.







The Damplier made a huge difference. Obviously, I conducted before and after listening tests, and Damplifier treatment dramatically improved the tightness and focus of the sound. I can even hear some bass and lower mids back there now.

More Damplifier went into the back seat pans. Note my high quality and expensive application tool.





I also treated the rear fender panels from the trunk access (no photos), the trunk lid, and any hidden areas inside the trunk.



The passenger door is almost complete. I used up the 2 sheets of Damplifier reserved for that door before I achieved enough coverage, so I am waiting for Best Buy to open to buy an 18x32" sheet of Dynamat Extreme to finish it and have enough for the other door. Here are some almost finished pics. A lot of the Damplier is applied to the back side of the inner panel where you can't see it in the photos. I need to finish the crash bars and add more to the speaker area and the inside overlap panels.







Final thoughts on the Damplifier installation. I really wish I had not screwed up and ordered the standard product. I wanted Damplifier Pro and do not know how I hit the wrong 'Add to Cart' button. So much for multitasking. I am generally a believer in 25 to 33% coverage with these types of products (I have only used Dynamat Extreme in the past). I have found in other installations that one runs into the law of diminishing returns after that. But either this car or this product is different. It needs more like 80% coverage to really be effective.

One thing I love about the Damplifier product is the fact that it is black. I do not want to be able to look through speaker grills and old tweeter holes and see bright shiny aluminum. Damplifier's dull black color is much more pleasing to the eye. I'm sure the Pro product yields better results and is every bit as good as Dynamat Extreme. I will try it on the next car.

Last edited by Steve Dallas; 07-12-2013 at 11:14 PM.
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Old 06-09-2013, 09:31 AM   #16
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These odd ducks deserve their own post. Strangely, they are light as a feather. Neo or AlNiCo magnets? There is what appears to be a passive radiator on the back. The front is not a cone, but a covering over a perforated metal frame. The cone is behind that. And of course, we all know about the weird little amp thing. The magnet appears to be just under the amp on the 'front' of the speaker where the dust cap normally resides. Bose sure when to a lot of trouble to create an inferior sounding woofer. Hopefully the Damplifier / Dynamat treatment will help it sound like it should.




Last edited by Steve Dallas; 06-10-2013 at 08:26 PM.
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Old 06-10-2013, 10:40 AM   #17
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Nice work. It is great to have all the pics for reference.

I have now replaced the rear 6x9 speakers in my base (non-bose) system. No noise deadening for me, although I did put some foam tape over a few of the holes around the rear speakers. The speakers I used are JBL P639. I also have some JBL GTO8608C on order for the fronts. I tested briefly and decided to use the -3dB tweeter attenuation setting (they have 0 or -3dB settings).

I had to drill out two of the holes on the new speakers to line them up with the existing holes in the rear deck. The two central (metal) clips on the rear speaker covers were a bit of a pain for me. They stayed in the deck lid and one on each side split the plastic cover when I took them off. I did then extract them from the rear deck lid and put them into the cover prior to re-installation.

As for the sound. Well it is a massive improvement over the stock base rear speakers. The stock speakers are 1-way, no tweeter, so have no highs and basically just fill the rear with some blurry mush. Now if I pan to the rear, it sounds better than if I pan to the front! Of course the front still dominates the overall sound, so we'll see how the whole system sounds when I upgrade those.

The only downside so far; well I probably tripled the weight of each rear speaker. Being an active member of the "racing" section of this forum I really should have weighed them, but I would guess I added 1-2 pounds per side, so 2-4 pounds in total. I'm consoling myself with the fact that it is almost directly over the rear wheels :-)

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Old 06-10-2013, 08:42 PM   #18
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The driver side door is now finished. I applied Damplifier as before and supplemented with Dynamat Extreme. Most of the Dynamat is behind the inner steel panel, so that panel has Damplifier on the front and Dynamat on the back, as it really tends to resonate. I also put squares of Dynamat on top of the Damplifier right behind the speaker. The crash bars also have a tendency to wildly resonate, so they received some Dynamat over the top of the Damplifier. I did not take more photos of the passenger door, but it is similarly treated.







Thoughts on Damplifier vs. Dynamat Extreme...

I cannot provide a true vs. comparison since I used standard Damplifier and Dynamat Extreme, but I can provide some contrast information.

Damplifier. This product has a rubberized layer that seems to be covered in adhesive. The aluminum layer is roughly twice as thick as Dynamat's aluminim layer. It is more rigid and holds its shape better. I found it to be much easier with which to work. The rubber and adhesive layers also hold their shape and are not messy. It cuts easily with tin snips and does not tend to cover them in gunk. It is easier to apply in my opinion. The flat black color is more pleasing to the eye. It does not perform as well in terms of vibration absorption, but that is to be expected since I failed to order the Pro version. Assuming the Pro version of Damplifier performs as well as the Extreme version of Dynamat, I prefer this product.

Dynamat Extreme. I have used this product many times in the past, and I always dread the application process. It's rubberized layer is more like tar than rubber. It is extremely messy. It clings to knives and tin snips, which require repeated cleaning during the process. I hate the shiny sheen on the aluminum, because it is harder to use in stealth applications. And it always looks like the skin of an old lady's butt once applied (at least in terms of wrinkles). Having said that, the stuff definitely works. I have used it on 7 cars now, and it has never failed me.

Thoughts on the value of this treatment now that the car is finished...

As usual, applying this type of product provides the advertised results. The bass and lower mid frequencies are much tighter, more focused, and louder. The rear deck speakers went from being all highs and upper mids to partially overcoming the Bose amp's EQ curve and sounding decent in the bass and lower midrange registers. The Bose woofers in the front were quite improved by the door treatments. They are still not great sounding speakers, but they are now more than passable.

Overall, I am very pleased with my work on this car, and I hope to enjoy it for years to come. It sounds a million times better than before even if it does still have a hole in the front mids. And I did achieve what I was hoping. The installation is almost completely stealth (just don't look at the rear magnets), and the sub is removable and reusable.

Last edited by Steve Dallas; 05-04-2014 at 08:23 AM.
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Old 06-11-2013, 08:28 PM   #19
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Here are some pics to document the factory Bose speakers in the S2 cars.

Front tweeter on top, rear tweeter on bottom. Note how much bigger the rear tweeter magnet is. That fits with the relative crossover points.


Front tweeters on left and rear tweeters on right. The sun is brutal to the rears.


Rear woofers.




Now off to eBay with the lot of them.
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Old 06-11-2013, 08:55 PM   #20
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Here are the final, final pics of my stereo improvement build. Yes. The bath towel is going to stay awhile.















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Old 06-13-2013, 12:55 PM   #21
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^Nice, and I like the idea of using the tire repair kit strap to also secure a bottle of oil.
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Old 06-16-2013, 08:32 AM   #22
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I am still struggling with the midrange hole in the front soundstage.

I thought I could get used to it, but I can't. My first approach to fixing it is to work with the Infinity tweeter to see what more I can get out of it. There is some risk of damaging it by going too low, but I am fine with that. I think I need to get down to 1800Hz to achieve the correct overlap with the 9" driver. I can't be sure of what I am doing without dragging the spectrum analyzer down from my studio, which would be a giant PIA, so I will try to do it by ear instead.

The crossover schematic looks like a 2nd order high pass, but Infinity's published specs list the slope as 18dB/Octave, which points to a 3rd order. Either way, the use of a 6.8uF capacitor means its crossover point is set very high--upwards of 8 - 10K--unless there is something else at play here (other components inside the plastic body of the tweeter?). In some literature, it is listed at 3.5K, on other literature, it is listed at 2.5K, and in still other places, it is listed at 2.8K. So I don't know what it really is. I don't have an inductance meter, so I don't know the value of the coil.

Last night, I soldered a 2.2uF film cap in parallel with the 6.8uF film cap to give me a total of 9uF. That definitely opened up the mids some, but not really enough. And I can't know how that capacitance interacts with the coil since I don't know its value. It may be time to just bypass the Infinity crossover and try a simple 22uF capacitor in series with the positive lead and see what happens. I don't think this UHF tweeter is designed to handle 1800Hz with a 6dB slope, but who knows? It is all guess work at this point anyway.

------------------------------------

I don't know how I missed these, but they supposedly go down to 1000Hz. And they would be more or less timbre matched to the new rears. I wonder if I can even remove the old ones now that they are glued in? Buy used sail panels off eBay for a test run? Hmmm... I'm leaving on vacation for 10 days tomorrow, so I won't be able to do anything before then, but I think a pair of these are getting a test run when I get back. I think I will just use double sided tape to stick them to the door metal without sail panels and listen to them for a week...


Last edited by Steve Dallas; 06-18-2013 at 09:45 AM.
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Old 07-08-2013, 04:46 PM   #23
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This should be the last update to this thread. I did purchase a set of Alpine SPS-110TW tweeters to see how they sound. They are similar to the ones pictured above, but with an inline crossover, which I thought might be smaller and easier to mount. They are supposed to have a crossover point of 1000Hz, which should work well with the Bose drivers. I also found a set of sail panels on eBay for about $50.

A few washers, a little glue, and some elbow grease later, and they were mounted.



I was able to use the included plastic spider to mount them without having to make a custom bracket. Two of the holes lined up almost perfectly with the factory holes. I did need to put 2 #6 stainless washers under one side and 4 #6 washers under the other side to achieve a good solid fit. Be careful here, because the tabs break off very (too) easily. Fortunately, I did not have any trouble, but I can see what some of the reviewers on Crutchfield and Amazon are complaining about. I did not trust the tabs alone, so I added some glue here and there to help support the new tweeters.

The results are very nice. They are timbre matched to the rear fills, which is great. They also fill the midrange hole nicely. I am pleased with these tweeters, and wish I had found them in the beginning. I'm still scratching my head as to how I missed them.

I am finally considering this stereo build finished. I had some false starts and wasted some money here and there, but the results are very good. The overall cost is reasonable, and I was able to keep a completely factory appearance.

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Old 07-08-2013, 04:50 PM   #24
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keep up the good work. love S2 DIYs no matter the subject when they have nice pics like this one
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Old 10-02-2013, 10:00 PM   #25
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stvnscott - Any chance you'll break down and bring that spectrum analizer home to find out once and for all what Bose broke with this setup so we can un-#uck it?

I've been dabbling with my Bose system since my car is not drivable atm. I made a small 8" sub for it and have been sitting in the drivers seat listening while I look over schematics.

I also tapped the rear channel input to the Bose amp. Whatever Bose's rear channel high-pass is set to (if any), it must be above what my sub plays. The sub sounds pretty linear. I can't see what they were thinking if they limited the bass output of the 6x9's.

Has anyone else noticed the HU's bass control is a band pass not a high pass? It seems to only roll off base down to maybe 80hz. Anything below that still gets through even with the bass control at it's minimum.

Edit - I've been looking more into this HU's "characteristics" to figure out what exactly Bose screwed up engineered. It seems as if the following is happening...

1 - The bass control is a notch filter not a shelf filter. It boosts/cuts frequencies roughly between 150 to 400hz. This may make it appear that the speakers are high-passed if the bass control is above 0.
2 - The bass control does not boost or cut frequencies below 150hz. (nifty trick to avoid distortion at high volume levels)
3 - The fader control doesn't effect frequencies below the notch filter's lower cut-off of say 150hz. Anything below that is unaffected by the fader.
4 - There is an auto-loudness present on the volume control that boosts high frequencies (at least) around the middle of the volume position. 15-20 on the display.
5 - Tapping the audio signal at the amplifier (for adding a sub amp) causes a subwoofer to follow the above rules.
6 - The system has subsonic filtering applied at the HU.
7 - The FM tuner has EQ'ing that destroys the frequency responce of the radio.
8 - The center channel, in my opinion, is ruining the stereo imaging.
9 - This HU is making it a disaster to tune this system with any aftermarket components.

Also, the signal lines to the amp are likely a balanced set (XLR). It has two conductors within a shield. They each happen to have 4vdc on them (referenced to vehicle ground). If you simpley connect an RCA plug to these two wires, you may damage the head unit IF your amp's RCA input is grounded because it'll short one of them to ground. Adding one capacitor to each of the two signal wires would decouple them and you'll be safer. I'm not sure what value to suggest because I don't know a sub amplifier's input impedence. 100uf 16v is probably plenty.

EDIT #2 - I swapped out my front tweeters with some kevlar domes and 10uf caps and what a difference that made. HIGHLY recomended. I now have highs with the trebble set to 0 vs. having it at 6 all the time. The door speakers are still muddy and the midrange hole is even wider due to the 10uf cap, but, I noticed something. When full frequency audio is played through a woofer there will be very little trebble but if you listen closly right in front of the cone you will hear that higher frequencies are there, just very diminished. Trapped may be a better word. If you listen closly to the door speaker you don't hear trebble at all. Not even mids. No speaker is so well designed that it rolls off frequencies that quickly, but a crossover can. This leads me to believe that the amplifier on the door speaker may have a low-pass crossover built into it. If so, that filtering isn't being done by the HU or the trunk amp because the door tweeters are fed from the trunk amp and there's definitly high end there, just not on the 9".

Tomorrow I'm going to try and find time to pull the door speaker's amp and trace the PCB to find out if there's a low-pass in there and what components would effect the frequency. It may be as simple as replacing one capor resistor on the amp to shift the door speakers' frequency higher into the midrange. I don't have the equipment to electrically test what the frequency is but once the filter components are isolated, and their values read, the frequency can be calculated as well as what values to replace them with.

I'm also going to try out the Morel MDT 12 tweeter. It's a 1.125" soft dome. 89 dB, 1,800-25,000 Hz, Fs 1000hz, 80w. This should allow the crossover to be brought down with a trade off of slightly less power handling. Morel MDT 12 1-1/8" Neodymium Tweeter 277-060 and the Pyle PBW8S midbass woofer. 3 ohm, 96 dB, 95 to 5,000 Hz, Fs108hz, 280w. Pyle PBW8S 8" Midbass 292-2532


Edit #3 - No low-pass on the door speakers. They're just THAT bad. I replaced them (until I get the pyles) with some 6" Bose speakers from a GM. Much better but I'll have to set that project aside for another day. Back to my engine swap...

Edit #4 - I got my Pyles installed and was disappointed, at first. They were VERY strong in the midrange and sounded like a cardboard box. They didn't look THAT bad on paper so I thought maybe they needed to be broken in. Since the Bose system has a subsonic filter, I couldn't play my 5hz test track (for breaking in speakers) and needed to play that track somehow. The door amps are used to boost power to the Bose 9" because it's a .5 ohm speaker and the trunk amp is designed for 4 ohm loads. I decided to eliminate the door amps completely since the Pyles are 3 ohm. The trunk amp can handle that just fine. With the door amps bypassed, I have access to the speaker connections via the trunk harness. This allowed me to connect a home stereo reciever to my new Pyles and break them in. Before breaking them in I decided to play some music using the home reciever and I was shocked to hear my door speakers playing quite nicely. Bose has programed some SERIOUS midbass boost into the factory HU. I'm not sure if it's on all channels or just the fronts but I will find out.

I'm a tube amp nut so to further entertain myself I dropped my 12w/ch tube amp into the trunk. I was completely blown away by the sound. That little 12w/ch amp sounded more like 50w/ch and the sound stage was incredible. It's actually the best sounding automotive front stage I've ever heard. So good that my friend and I are designing a 4ch tube amplifier for automotive use.

The solution to the Bose disaster is a $300 JL Cleensweep.

This video explains what it does.


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