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Discussion Starter #1
We're working on integrating some after market amps, speakers and subs to an 06 Infiniti M35x with Bose Audio/Video/Nav... The head unit cannot, and will not be replaced, it has to stay.

We're using line level sourced just before the Bose amp in the trunk to supply voltage to the aftermarket amps we installed.

Our issue is this, aside from the fact that Bose sucks the big one, is that the head unit will reduce bass output relative to volume, and it will do so drastically before a desired volume level is reached. So, we thought maybe a line driver of some sort could help, since we could bump up the line voltage going to the amps and get more output from them, so desired volume levels will be reached before the head unit starts to filter out the bass frequencies. Does this make sense?

An option we have locally is a Phoenix Gold EQ215, this unit could help as the car will need some EQ and it has a line driver built in. Is this a good choice?

We're trying to stay away from products like the ReQ and Cleansweep, as those are speaker level, and we're dealing with line level. Is there a better product out there, that's affordable, that accepts line level inputs, that will "fix" the issue we're having?

Thanks in advance, wise ones.
 

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What type of amps are you using? Possibly they don't accept a balanced differential input? You could use a Rockford BLD to change the signal to a standard signal.

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Discussion Starter #4
Hmmm, I have never seen a HU out of a Infiniti that EQ's the signal. Its always at the bose amp it does that. I do not see why the M would be any different. My G35 and FX35 dont.
If you really think it does, throw a MS-8 on it and let that get you a flat signal again. A standard EQ wont work well.
It absolutely does. At just past 1/2 way on volume it starts to drop off, at around 3/4 there is practically no bass at all. It makes it extremely diffcult to tune the system as the frequency output changes dramatically with volume from the head unit.

I understand the MS8 can auto tune, or manually tune a system to a near flat frequency response at the desired seating position, but does it auto adjust on the fly? It would need to self adjust every time the volume is adjusted up or down on the HU.

What type of amps are you using? Possibly they don't accept a balanced differential input? You could use a Rockford BLD to change the signal to a standard signal.

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The amps are...
(1) Alpine PDX-M6 driving an Alpine Type R 10".
(1) JL (can't remember model right now) older 4 ch, I think 100x4 driving Polk components.

I believe at this time the line signal from the HU goes into the JL, from the JL line out into the Alpine.

There is really no issue with output or noise on either amp/speakers. It's quiet, virtually no hiss or whine or any kind of noise at all. Output at anything up to half way on the head unit results are good, it starts getting plenty loud but then go just a bit beyond and the mids/highs keep increasing but the bass starts decreasing.
 

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Still having a hard time believing the M is any different than any other Infiniti.

Here is Manville from JL chiming in on the subject from another forum

"If it has a Bose system you don't need LOC's or a CleanSweep. Just splice a 4 channel RCA cable to the head unit outputs (or the amp input wires) and plug it into the amplifier (assuming the amp has differential-balanced inputs, like a JL).

The head unit output with the Bose system is flat (all the EQ is in the amp).

The LOC's degrade performance and are unnecessary in that system."

Everything on the net points to the EQ in the amp. It has been discussed many times over.

So I have no clue. I have tapped into the signal before the amps with no problem. I know Bing on here has done it several times also with no problems in SQ cars.
 

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Discussion Starter #6
Still having a hard time believing the M is any different than any other Infiniti.

Here is Manville from JL chiming in on the subject from another forum

"If it has a Bose system you don't need LOC's or a CleanSweep. Just splice a 4 channel RCA cable to the head unit outputs (or the amp input wires) and plug it into the amplifier (assuming the amp has differential-balanced inputs, like a JL).

The head unit output with the Bose system is flat (all the EQ is in the amp).
OK. Let's just assume, for arguments sake, that it's not the HU. There is a definite loss of bass in the system the louder the volume is set. With the equipment installed, what can cause this?

The thread from Manville that you are referring to, is that regarding the Bose sytem in the same brand/model/year of car as what we're dealing with? I'd like to read it, please post a link.
 

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This is the thread I looked at, and the link to his post in in the first post of that thread. His post is from 2007.

Bose head unit output is flat (EQ is in the amp) - FreshAlloy.com Forums


I currently have a 08 FX35 and the signal is flat from the HU (which should be the exact same unit), my 03 G35 coupe is also flat from the HU. Are you 100% positive you are pulling the signal from the HU and not the amp? You might have your ins and outs of the amp mixed up.
 

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I would just check to make sure you grabbed the right connections too. You gotta meter em out if you didn't already. I had the service manual for my 07 g35 sedan with the wiring diagram for the stereo. I decided to meter them out any way and found out that the service manual wiring diagram is totally different from what was installed in the car. Wire colors were different.
 

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I understand the MS8 can auto tune, or manually tune a system to a near flat frequency response at the desired seating position, but does it auto adjust on the fly? It would need to self adjust every time the volume is adjusted up or down on the HU.
It does not adjust on the fly, but you can set the factory radio volume to a specific number and eq off of that. Then use the volume control of the MS8 only to turn the volume up or down. As long as the volume on the factory head unit is not messed with, it should always be a flat signal.
 

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Discussion Starter #10
This is the thread I looked at, and the link to his post in in the first post of that thread. His post is from 2007.

Bose head unit output is flat (EQ is in the amp) - FreshAlloy.com Forums



I currently have a 08 FX35 and the signal is flat from the HU (which should be the exact same unit), my 03 G35 coupe is also flat from the HU. Are you 100% positive you are pulling the signal from the HU and not the amp? You might have your ins and outs of the amp mixed up.
I think we're talking apples and oranges here. The EQ you're referring to, and the thread you linked to, discusses the stationary EQ curve placed into the system by Bose/Infiniti to shape the overall sound in the vehicle. Many manufacturers do this, they even have different EQ curves for cars with either cloth or leather interiors, as the sound would change slightly due to the fabric absobing more sound than leather. What I am referring to is in addition to that EQ curve that is staionary and does not change with volume output. Some factory systems reduce bass as the volume increases, and this is sometimes done in the HU, and sometimes in the factory amp. In this situation, I believe it's happening in the HU.

That question is discussed in posts #6 and 7 in the thread you linked, but not answered.


Well, mistakes are possible, so maybe... why would the amp have a line level output?

According to the factory service manual for that car/system, we tapped into the correct lines.

Believe it or not, the Bose systems in different models differ a good deal, for whatever reason.
 

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Discussion Starter #11
I would just check to make sure you grabbed the right connections too. You gotta meter em out if you didn't already. I had the service manual for my 07 g35 sedan with the wiring diagram for the stereo. I decided to meter them out any way and found out that the service manual wiring diagram is totally different from what was installed in the car. Wire colors were different.
We did use a meter and verified that the output voltage increased and decreased as a whole with volume up and down on the HU. Although it was a rather low voltage, it is still enough to drive the amps adequately for this install. As far as we could tell, the service manual we have matched our pin configurations exactly.

It does not adjust on the fly, but you can set the factory radio volume to a specific number and eq off of that. Then use the volume control of the MS8 only to turn the volume up or down. As long as the volume on the factory head unit is not messed with, it should always be a flat signal.
The MS8 is probably a great product that could do good things here, but it's a bit pricy.

Is a line driver not a good solution here? If we can increase the line voltage from the HU, so that we reach a higher output/volume from the amps/speakers before we get into the HU's "bass reduction zone", shouldn't that basically fix our problem?

That brings me back to the PG EQ215. EQ and line driver in one.
 

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A line driver only amplifies input voltage, so if the voltage on low frequency drops, so will the line driver's output. You might want to look into an LC2i from audio control with their AccuBass correction.

wait wait...nevermind. not sure if it will try and step down your line-level.
 

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Discussion Starter #13
This is the thread I looked at, and the link to his post in in the first post of that thread. His post is from 2007.

Bose head unit output is flat (EQ is in the amp) - FreshAlloy.com Forums
The discussion you are referring to, the link within the link you posted containg the Manville quote, post #18 by Norm, Super Moderator, states "A cleansweep will not replace bass attenuated by the head unit. The attenuation is done by the head unit before the factory amp."
 

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Have you put the car's headunit outputs on an RTA to verify your findings??
 

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Discussion Starter #15
A line driver only amplifies input voltage, so if the voltage on low frequency drops, so will the line driver's output. You might want to look into an LC2i from audio control with their AccuBass correction.
Yes, but by bumping up the line voltage, means increased output from the amps, does it not?
In turn, that should mean that we will have increased volume at the same volume setting on the HU then we would without the line driver, should we not?
So, if we can achieve our desired volume output from the speakers before we reach the half way point on HU volume control, which is where the bass reduction really starts happening, wouldn't that work?

If only the LC2i or the LCQ1 accepted line level inputs, we might have a winner with the AccuBass feature. However, we don't want to use speaker level and are trying to bypass the factory amp.
 

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I am so confused here. I have a sub hooked up to mine, it does not cut or boost the bass at all. I tapped into the signal going to the bose sub amp. I can not find any info on the net, other than acouple speculations that the HU is "cutting" the bass, or actually boosting it at lower volumes. Does not make sense that the HU would not do both the bass cutting/boosting and EQ, if it was doing anything at all.

When the weather warms back up, I will be adding my MS-8 to the rest of the stereo. I will get my RTA back from my buddy and verify the HU is or isnt boosting anything. But that will not be for alittle.
 

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Everything I have read that is actually objective measurement says that the Bose HU does not do any EQ shift with volume. The non-Bose head unit DOES though, so maybe that is where the confusion is coming from?
 

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Discussion Starter #19
I am so confused here. I have a sub hooked up to mine, it does not cut or boost the bass at all. I tapped into the signal going to the bose sub amp. I can not find any info on the net, other than acouple speculations that the HU is "cutting" the bass, or actually boosting it at lower volumes. Does not make sense that the HU would not do both the bass cutting/boosting and EQ, if it was doing anything at all.
It varies from one car to another, even from the same manufacturer. What your car does doesn't mean a different year/model will be the same even if they are both Infinitis.
Everything I have read that is actually objective measurement says that the Bose HU does not do any EQ shift with volume. The non-Bose head unit DOES though, so maybe that is where the confusion is coming from?
What does "objective measurement" mean?

There is no confusion here, the system is an Infiniti, M35x, 2006, Bose, Nav, DVD, Surround Sound, RSE... all the bells and whistles as far as entertainment goes for that model and year. The HU DOES filter out bass at higher volumes.
 

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He is referring to actually being measured and not just assumptions that it does this or that. There are not any measurements taken that say the HU cuts or boosts anything. On another note, I would think its boosting at low levels like the "loudness" function on some older HU's, not cutting, but that is neither here nor there.
 
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