Rotary Rasp

iTrader: (2)

What is the efficiency of the Bose 6x9's? The Infinity's are 90 dB, so IF the Boses speakers were 87dB, wouldn't that mean they would ultimately equal out to the same out put?

Rotary Rasp

iTrader: (2)

I have another question. As of now I am using a Hi/Lo line converter after the bose amp. Should I replace it with this Soundgate (http://www.logjamelectronics.com/sounlocbosli.html) bose converter since it takes the differental signal before it is amped. Will I notice any difference with subs or is this made for mid range/ tweeters?

MrWigggles

Rotary,

That looks like the best thing to use. Transformers in most line output converters usually create some distortion usually in the sub bass region. How bad is the distortion? That is a tough question. Very few companies spec distortion. Rane makes a quality unit http://www.rane.com/pdf/lt22dat.pdf and you can be sure that it is top notch given their pro audio lineage.

Active converters are rare but are the best way to go and the smartest way to do things. I was actually thinking about making my own if I couldn't find a good aftermarket version. (They are not that difficult to design and are found internally on virtually any amplifier that has speaker level inputs.) The Soundgate unit sounds promissing and I will likely go that route. If it doesn't work well, then I will make my own. One thing I would like to do is create a turn-on lead in the process. If the BOSE is a differential system then there should be a DC offset voltage whenever the system is turned on. That voltage can be amplified to create a 12 volt trigger.

Good luck.

-Mr. Wigggles

Ps. I don't know what the effieciency of the Bose speakers are. My guess is that you will be fine using 4 ohm speakers, but it depends on how much output you are looking at getting from the system.

Rotary Rasp

iTrader: (2)

Thank you Mr. Wiggles. I noticed something on my amp today. I seems that it has the capability of using the low level (RCA) inputs as high level inputs. Look at the switch to the left of the RCA inputs. Would using this better then the line converter I am using now? Is it active? -Thanx

MrWigggles

Rasp,

Yes and no.

Wether you tap into the signals before they reach the Bose amp (line level differential) or after the Bose amp (speaker level differential) the signal is going to be differential. You can not plug either signal directly into your amp in a conventional way.

However, you might be able to hook up the signals in an unconventional way. When you make the RCA cable to go from the Bose amp to the Polk, connect the "L+" and "R+" wires to the center conductors of the RCAs as usual, but DO NOT connect the "L-" and "R-" signals from the Bose to anything. Instead connect normal ground to the shields of the RCA's.

This will work but it may either be noisey or exhibit power on/off thumps when you turn your system on/off.

It is free if you want to try it and give it a shot.

-Mr. Wigggles

Rotary Rasp

iTrader: (2)

wait, are you saying that the high level lines going to the speakers are differential? I didn't know this was possible. Will this cause problems? i know that other people have been burning up their head unit by tapping in before the bose amp. am i going to have this problem? Also what does my line converter have that allows me to tap into the speakers, that my polk amp wouldn't have?

MrWigggles

99% of all speaker level signal from factory radios/amplifiers are differential. This is called a BTL radio and is able to get peak to peak voltages onto the speaker of about 28.8 volts without having to use a transformer. This is why the max rms power you can get out of a radio is almost always 25 watts (i.e. (14.4 volts peak X .707)^2 / 4 ohms = 25 watts rms)

The reason as I see it why people are burning out there headunits is because they are shorting the R- and L- signals together and attaching them to ground. In a balanced system there is voltage on both the positive and negative signals. Shorting them together is the same thing as hooking the output of one cd player into the output of another CD player. You are creating a collision and it is a bad practice. If the equipment isn't fool proof you can short something out real easilly.

In your case you shouldn't have a problem. You are terminating the signals into a high impedance load the preamp inputs of your amp.

-Mr. Wigggles

Rotary Rasp

iTrader: (2)

If differential signals are so clear, why doesn't the aftermarket audio stuff use it?

MrWigggles

Differential leads itself very well to unshielded wires. The noise cancels out. Most factory wiring harnesses use unshielded wires so differential is the way to go.

Shielded wire (i.e. good ol' coax) don't really need to be differential so headunits don't use them. You can easilly get 90dB+ signal to noise with moderate voltage RCA so why bother with the expense of differential?

When you need to go long distance and get 100dB+ differential is the key (i.e. XLR connectors), but for most listening enviroments that is completely uneccessary.

-Mr. Wigggles

Rotary Rasp

iTrader: (2)

Ok, so I have decided to buy the LOCB.2 (http://www.logjamelectronics.com/sounlocbosli.html) because it will give me a flat signal before the bose amp has a chance to equalize it. If anyone has it installed already let us know how it works.

irfan

I built a double box for my subs, but i had to make them face forward (i'll get a pic).. but I love your setup there. I have the exact same speakers but I didnts think they would fit like that. Ive only had this box for 3 weeks but I really want to do your idea now. Would you mind sharing plans and dimensions? I always build with 3/4" MDF so if you ised 3/4" ply then it should work well. I know what you mean about not being able to screw in speakers in the same holes.. and with infinitys tiny lip you cant really get room for tnuts either. I'm going to turn mine and face them backwards and give em a test, if they sound great think id want to try your method. im using a 600W jbl amp

care to share plans?

thanks. my email is 'khan(dot)95-at-osu(dot)edu' --
replace (dot) with a ".", -at- wih @

hopefully spiders wont pick up on that address

irfan

Rotary Rasp

iTrader: (2)

Ok lets see if I can remember off the top of my head. (i'm at work)

The external dimensions are as follows:
Bottom 13 x 12 (13 deep, 12 wide)
Top 9 x 12 (9 deep, 12 wide)
Sides 13 - 9 (60 degree slope on one side) x 12
Front 12 x 12 with a 45 degree cut in one side (Cut measured 3 inches down from top and 3 inches over from top)
Back 12 x 15 (sloped, so its longer)

Total internal volume is aprox .61 cubic feet

I have much better pictures at home, i'll post them later. I have a feeling this is only going to confuse you more.

P.S. My polk amp was tested at 595 watts rms by polk, you got at least 600 with you there. You're going to rattle your muffler baffles like me! I just placed a order for 70 square feet of rattle trap sound deadening (dynamat knock off), I plan on doing the entire car.

irfan

thank you very much... regarding the outboard side, do you still haev the dimensions/angles for the notch you have in the top corner? i see that there are 2 piece involced, a vertical wall and an angled piece, if you have those numbers that would be very helpful.

Rotary Rasp

iTrader: (2)

Today I replaced my line output converter with the Soundgate LOCB.2. I installed it right behind the stereo because this unit it also a line driver. I must say, the results were impressive. The bass is even throughout the entire volume range. Before the bass would be too loud at low volumes. Also it is a much cleaner sound with less distortion and more bass.

MrWigggles

That's good to hear Rasp.

I will be placing mine at the back next to the Bose Amp. I think the noise will still be small.

It is going to be a month before I finish installing my system - the line converter was one thing that was still up in the air.

Thanks,

-Mr. Wigggles

DAZ-13B

Any chance of giving us some measurements of your boxes!! they are a work of art !
ps I only know metric !!

Regards Daz

Rotary Rasp

iTrader: (2)

The two side boards are 7 1/2 inches wide and are cut on a 45 degree angle. They are also sloped to match the back of the box. I don't know if that helps any, but without removing the boxes from my car, I can't get anymore measurements.

Follow this inorder to convert to metric:

Centimeters to inches: cm x 0.39
Inches to centimeters: in x 2.54

DAZ-13B

Thanks Rotary Rasp! woops must have missed the measurement post .....now who has my Circular saw???

Regards Daz

Jedi54

iTrader: (7)

Holy Thread Ressurection BATMAN!!! haha.

Great install Rasp, you've got me counting the days down until I can install something very similar.

JPotta

Hey I made some similar boxes a few months ago they are a little different but I really wanted to keep the pass through open so Im glad to see im not the only one who know how to do it right. I took my boxes out recently due to the fact that my voltage was droping to around 8!!!