Steve Dallas

Interesting info, KickerFox. I am not inclined to bring the spectrum analyzer down, since that would require bringing the main DAW computer and half the studio's outboard gear along. How about, instead of recording studio precision, we settle for home theater precision? I can do that in about an hour with a laptop. I'll try to squeeze it in today.

How did you install your new speakers in the doors? Did you bypass the door speaker amps, find a way to use them, or do something else?

Steve Dallas

Well, that was enlightening.

I did not have time to do everything I want to do, such as play with the bass and treble controls to determine how they behave, but I might have time to do that tonight.

The short story is the HU sends a flat signal to the rear. If there is any frequency tailoring, it is done in the amp.

I sent a sweep from 0 to 20K Hz to the entire system with all HU controls centered and measured the response at the rear signal by using the tap I made for my sub earlier. Here are the results:




Let's zoom in on the bass frequencies:



The -3dB point appears to be at 40Hz. Honestly, I don't know if that shelving is from my tone generator, the limitations of my laptop's sound card, or something the HU is doing. Still, it's not that bad--especially considering the slope.

I set the sweep to repeat to allow me to use my ears at various listening locations. In the front, I heard the signal at about 50Hz and was able to hear it transfer from the Bose woofers to the Alpine tweeters without a noticeably dramatic dip in the midrange. I will slow the sweep down and use my SPL meter to try to detect anything there in measurable terms, but it appears for now I more or less solved the hole in the mids problem with the Alpine tweeters, and the fronts are playing back the full spectrum of sound fairly flatly.

Then I climbed into the back seat. Different story there. I could barely detect the signal with my ears at around 150Hz, and the signal level seemed to peak around 2500Hz. So there is something going on back there with bass limiting and upper mids hyping (<-- good grammar over there). I am interested to slow the sweep and try the SPL meter back there, too.

Hopefully tonight.

kickerfox

I didn't see the thread has moved on to page 2. I had been editing the last post on page 1.

At first I had them powered by the door amps but have sinced removed the amps. At the moment they are powered off the trunk amp. I'm working on installing a 4ch Alpine and testing things along the way to see what has what effect.


If all the shaping is done in the trunk amp that's GREAT news. I hadn't made it that far yet. I got distracted last night listing to a tube amp in the car.

There's a lot of phase problems in an any automotive environment. It'll never have proper imaging everywhere.

Steve Dallas

OK. I had some time to run some additional profiles. I ran the HU rear preamp out flat and with tone controls in various places. I also ran the amp output flat.

The preamp signal looks pretty normal to me. The bass and tone controls are peaking / notch filters, which is pretty common. The bass boost / cut is centered around 60Hz. The treble boost / cut frequency is centered around 12KHz. Both are common frequency centers. The Q of both is a little wider than I am used to seeing, but is not out of bounds.

The power amp output is just bizarre. I used an inexpensive Metra interface to capture it, so that may explain some of it--especially the slope of the bass cutoff, although I suspect Bose did this on purpose to prevent distortion. But it certainly does not explain all of it. This plot both contradicts what I was hearing with my ears in some cases (low bass) and confirms what I was hearing in other cases (lack of lower mids, hyped upper mids and highs). Scooping around 200-250Hz is an old trick to remove mud, but the Q is usually narrower, and the cut is usually smaller. It also explains why the rear speakers sounded so much better with a home audio receiver subbed for the Bose amp. It further explains why the Infinity speakers sounded so piercing. In any case, it is very strange and far from flat.



In case you can't make out what the colors in the legend are:

Dark green: HU preamp flat
Dark blue: HU preamp bass 6 treble 6
Goldish: HU preamp bass 3 treble 3
Light green: HU preamp treble 6
Purpleish: HU preamp bass 6
Magenta: power amp flat


This really makes me wonder what the front amplified signal looks like...

kickerfox

Thank you for your efforts thus far. It should help.

That low end roll off (hu flat) isn't a bad thing for us doing custom amp/speakers IF we're running a sub. It's known that line output convertors suck out some lows so it could be attributed to that if that's what you used to tap the amp outputs.

It's the front I've been playing with the whole time. Those are what I'm worried about. That's where the sound stage comes from. To my ears your plotted mineshaft at 250hz is the complete opposite on the front channel. I bet you find a mountain at 250hz on the fronts coming from the Bose amp. They may have done that to bring a "fuller" sound to the doors.

Tonight I installed some Pioneer 6x9s in the rear. Playing the tube amp through them almost gives me a stereo image from back there with the right channel being a little strong. That's perfect because my fronts are a little strong on the left. It may balance out perfectly.

I'm VERY happy with how the Pyles sound. If I move my head between the seats the speakers vanish and an orchestra appears in the windshield. The only way to shift that to the drivers seat will be with a DSP that has phase control. I can't wait to hear the finished system. So far I'm liking the acoustics of this car.

I would love to see a plot of the fronts.

Tonight I'm wiring up an older Alpine 4ch. I have had this amp a long time. I'm going to see how these preamp signals work and if a capacitor-coupled to RCA option works. There is a DC voltage present in them.

Steve Dallas

Some have referred to the preamp outs as differential. Others have referred to them as balanced. I have not heavily investigated, but I thought they might be balanced while I was working with them. Most quality amps will have a decoupling cap on each input to block DC, so external caps may not be necessary. That seems to be the case with my sub amp.

This is far from definitive, but my SPL meter showed my my fronts are fairly flat the way they are currently configured. There is still a midrange valley, but it seems to only be about 3dB. I would sweep the fronts too, but I don't want to dig into the wiring harness again. And, I am off to autocross here in a few minutes.

Funny you should mention tube amps. Until the recession hit, I owned a guitar amplifier manufacturing company. We specialized in building tube amps.

Steve Dallas

I was curious about the signal going to the fronts this afternoon, so I pulled the sail panel off the driver's door and profiled the signal going to the tweeter. It is just as interesting as what is going to the rear 6x9s.



This makes me want to find a definitive wiring diagram for this system. I had read on this site that the tweeters are simply run in parallel with the front woofers, but this does not seem to be the case considering the obvious high pass filter applied to the signal. And, if there is already a filter in play, why the bass blocking caps on the factory tweeters? What about the rear setup?

Now I'm curious about what is being sent to the door woofers, but not curious enough to take a door panel off again or tap back into the wiring harness, so that one will have to remain a mystery.

Exit thought: I think I found my midrange hole in the front.

kickerfox

Facts I know...

The output from the trunk amp is split in the door.
The tweeter is powered off the rear amp.
The input to the door amp is parallel with the tweeter.
The door amp only powers the 9".
The door amp is switched mode (class-d)

averyrm

The Series 2 has one line going to the amp on the package tray and then separate wiring from the amp to the tweeters and woofers in the front door.

https://docs.google.com/file/d/0B4M7...thkey=CKHv6MML

Starting on page 240. Pinout for amp on page 259 and 260

Steve Dallas

So the rear woofers and tweeters really are in parallel, but each of the front door woofers and tweeters receives its own filtered signal from the rear amp. That falls into line with my subjective measurements.



Now that we know it is a 7 channel amp:

300W / 7 = 43W Peak

43W / 3 = 14W RMS per channel.

Seems about right. I wonder if all the channels are equal output?

Thanks!

kickerfox

stvnscott - Autozone has the schematics. First one shows the door amps.

http://repairguide.autozone.com/znet...3f80252199.gif

http://repairguide.autozone.com/znet...3f80252197.gif

averyrm

Those look to be Series 1 schematics. In the 2009+ the only amp in the door is built into the main woofer.

kickerfox

Yeh I think I've seen that. I have an '04.

Steve Dallas

I find myself in a place where I am beginning to care less about the resale value of keeping most of the Bose system intact, and more about good sound. I am seriously considering pulling the Bose amp and replacing it with a 4 channel Alpine, then replacing the door woofers with a nice pair of Alpine 6.5s. My only hesitation is that the front center channel will no longer work, and anyone testing the factory HU might notice.

I probably won't do it since I don't use my car as a daily driver, but it sure is tempting.

kickerfox

I was in the same boat but I got so fed up fighting things that I just said screw it and dropped in a 4ch. If it's done right buyers generally don't care as long as it's a clean install and everything is hidden.

ASH8

Nice job OP...Damplifier is a good product, one of those where actually less use (of it) is more.
Got some of it over from US for use on my MX-5 vibrating trunk floor...not for car sound system.

Real sound has to be analog,

Like my Linn Sondek LP12, 6 x Naim power amps, simple Naim pre amp, Linn Isobarik speakers, Nakamichi 1000ZXL.

Steve Dallas

It is more than a little embarrassing, that for all my reading and planning in the beginning, I never profiled the system to see if what has been reported about it is actually true. I suppose the reason I failed to do this is that I was boxed into thinking about spectrum analysis taking place in the studio with very expensive and precise tools, and not in the garage. Moving all that equipment to the garage would be a royal PITA. It did not occur to me until last week to KISS and use a laptop with a tool like Room EQ Wizard (normally used for profiling rooms) to do it on the cheap. Live and learn. Seems obvious now. Dang.

Steve Dallas

Hmmm...



SNL and THD aren't very good, but probably at least as good as Bose. Hmmm...

ASH8

....the more you add into any system the more you actually take away...Trying to find some 'holy grail' of deliverance is futile.

Always improve from the source first, then work back wards..(speakers are the very last 'upgrade').

In the end you want to hear how it was 'meant to be', don't you?, adding a multi track into a car (anywhere for that matter) and a thousand amps and speakers only confuses the ears and the operator...it is a distraction.

I am certainly no expert, but, over my many, many years 'in playing', buying, swapping, testing, the penny dropped very early on that not everything is equal, less is more, Db (volume) is not the be all and end all.

Frankly there are too many other 'electronics' in cars which interfere with 'quality' let alone the vibrating physical environment of a car, it's panels, trims, dash......

Like many things you can over analyze...in the end 'how' does it sound?, does it please your ears?, is it harsh and or does it shriek at you? (digital), or do the "instruments" roll and the sound, the music,... real? (analog).

KISS...indeed.

kickerfox

I started with the door speakers since those are the most important part.

ASH8

Umm NO, in any sound system the most ''important part'' is the 'source', the very beginning, first 'a' stable power supply with it's own independent circuit (of heavy wiring), then what is the media (software player) MP3, tape, 8 track, vinyl, whatever, next are your amps, next pre-amp (if applicable), wiring from amps to speakers, the very last are your speakers....any other way and you are putting the cart before the horse.

In other words you can install the (best) for car speakers available in the world, but, if the head amp or player or input (signal source)
is of poor quality then it does not matter what speakers you use the sound quality will always be poor, you are amplifying a poor signal...
The "Bose" system (hardware) Mazda use is very average to poor to cheap, I certainly would not call it 'quality'.

Spend your $$$'s at the front end of any system, never the rear end first.

BTW: my personal preference are for speakers without any mini amps or main amps attached to speaker.

averyrm

Any source, aside from FM/AM, you play in the RX8 will be digital.

The "best bang for the buck" improvement is speakers, however.

You must have an amp, regardless. Be it internal or external the signal is amplified.

ASH8

Really...

Carbon8

iTrader: (4)

I laughed a lot

averyrm

Explain how any of that is incorrect?