Adding a sub to car without DSP; more harm than good?

[gabrielb]

My car has 4 channel Pioneer 8704 amplifier, but I'm only using 2 channels to feed my front speakers (Infinity 603CF).
I can bridge the 2 unused channels and get 300W RMS to push a sub.
The AMP has LPF/HPF for the front channels pair and for the back channels pair, but no way to mange delay.
Will the SUB be any good without DSP to manage the delay or that I the delay between SUB and front speaker will do more harm than good?

 

[Doodski]

My car has 4 channel Pioneer 8704 amplifier, but I'm only using 2 channels to feed my front speakers (Infinity 603CF).
I can bridge the 2 unused channels and get 300W RMS to push a sub.
The AMP has LPF/HPF for the front channels pair and for the back channels pair, but no way to mange delay.
Will the SUB be any good without DSP to manage the delay or that I the delay between SUB and front speaker will do more harm than good?

For many years subs where used without DSP and many happy people enjoyed that. What model of vehicle is it?

 

[gabrielb]

For many years subs where used without DSP and many happy people enjoyed that. What model of vehicle is it?

It is mini SUV - Peugeot 2008, the plan is to put the SUB in the trunk

 

[Doodski]

It is mini SUV - Peugeot 2008, the plan is to put the SUB in the trunk

OK... I see what you have in mind. That rear of vehicle sub location will work very well. If your vehicle has a cover for the rear area you may use that and it should not affect the sub output. I'm more the 4 speakers kind of guy but subs work so well for so many people.

 

[Keith_W]

In home audio, DSP is needed to tie subs in because (1) listening rooms form peaks and dips so some kind of amplitude control is needed, and (2) time and phase alignment is needed.

In a car, the volume is so small that the Schroder frequency is very high. This means that virtually the whole of the car is in pressure mode, so there are much fewer peaks and dips. Time alignment is not needed since the subs are very close to the main speakers. About the only thing that needs to be done is phase alignment to avoid cancellation at the XO frequency.

That said, DSP is still needed for the upper frequencies. DSP is less needed for subs.

 

[gabrielb]

In home audio, DSP is needed to tie subs in because (1) listening rooms form peaks and dips so some kind of amplitude control is needed, and (2) time and phase alignment is needed.

In a car, the volume is so small that the Schroder frequency is very high. This means that virtually the whole of the car is in pressure mode, so there are much fewer peaks and dips. Time alignment is not needed since the subs are very close to the main speakers. About the only thing that needs to be done is phase alignment to avoid cancellation at the XO frequency.

That said, DSP is still needed for the upper frequencies. DSP is less needed for subs.

Thanks!
How do you do phase alignment in a car without a DSP?

 

[Keith_W]

Thanks!
How do you do phase alignment in a car without a DSP?

Short answer: I don't think you can.

 

[Sokel]

Short answer: I don't think you can.

Lag all pass filter,like for decades.
Distance is so small that can be very-very simple.

 

[Keith_W]

Lag all pass filter,like for decades.
Distance is so small that can be very-very simple.

You're right of course. The AP filter would have to be placed for the upper frequencies, because subs are usually delayed.

 

[Hayabusa]

distances in a car are in general less of a problem with bass phase alignment

 

[gabrielb]

Short answer: I don't think you can.

Will the system benefit from a SUB without phase alignment?

 

[gabrielb]

You're right of course. The AP filter would have to be placed for the upper frequencies, because subs are usually delayed.

What is AP filter?
Is there anything I could about it without a DSP (only LPF/HPF and relative gain can be adjusted )

 

[gabrielb]

Lag all pass filter,like for decades.
Distance is so small that can be very-very simple.

what does it mean to "Lag all pass filter" ?

 

[Keith_W]

Will the system benefit from a SUB without phase alignment?

It depends on whether your woofers can produce bass frequencies or not. If they don't, then of course a subwoofer is beneficial, even without phase alignment. Even in the worst case scenario (the sub is 180 degrees out of phase with the woofer), the cancellation will only occur in the overlap range between the sub and the woofer.

What is AP filter?
Is there anything I could about it without a DSP (only LPF/HPF and relative gain can be adjusted )

AP filter = all pass filter. This passes the amplitude response unmodified, but rotates the phase. It is a possible solution, but it requires measurement of the time lag and then you need to design and build the filter.

All time alignment depends on delay (because you can not send signals into the future). Subwoofers are typically delayed compared to tweeters for many reasons. One reason is that your subwoofer is in the boot, but your tweeters are in front of you - so there is a time lag between sound arriving from the tweeter compared to the sub. Also, bass frequencies are by their very nature, always delayed. A 20kHz sound takes 1/20,000 seconds (0.05ms) to exit the tweeter. A 20Hz sound takes 1/20 seconds (50ms) to come out the subwoofer.

This means that if you design an AP filter, it needs to be applied to all frequencies from the woofer upwards to delay the entire frequency range to match the subwoofer.

A separate question is whether delayed bass frequencies are even audible. I would argue that they are not audible in most typical car installations. I can give you links to psychoacoustic research if you are interested. So I would advise you NOT to bother with subwoofer time alignment. It produces pretty graphs, yes. But I think it is an example of audiophile navel gazing.

So in summary: amplitude correction - yes. Phase alignment - yes. Time alignment - no.

 

[terryforsythe]

My car has 4 channel Pioneer 8704 amplifier, but I'm only using 2 channels to feed my front speakers (Infinity 603CF).
I can bridge the 2 unused channels and get 300W RMS to push a sub.
The AMP has LPF/HPF for the front channels pair and for the back channels pair, but no way to mange delay.
Will the SUB be any good without DSP to manage the delay or that I the delay between SUB and front speaker will do more harm than good?

I'm dating myself, but I used subwoofers in my cars long before DSP was availble to the general consumer. Yes, they definitely helped and my car audio systems sounded significantly better than they did without the subwoofers.

That being said, with the low cost of DSP now days, I definitely recommend using it. DSP makes subwoofer integration much better and easier to tune. It takes subwoofer integration to the next level.

 

[terryforsythe]

Will the system benefit from a SUB without phase alignment?

Yes.

But, phase alignment makes it even better.

I would add the subwoofer. If you are satisfied with it, then you are good to go. If you are not fully satisfied, you can add DSP sometime down the road.