Subwoofer Placement & Integration

[Satanica]

15 minutes ago, Pieface said:

Can you sweep each subwoofer individually? Physically switch one off if needs be and mute the outputs to the big red bass units.

 

I think it is key to get the two subwoofers integrated with each other first then integrate the subs as a single entity to the big Red bass units.

 

You need to understand the output of each individual sub and then you can get their summed behaviour headed to where you want it to go.

 

Thanks for your response. Yes I can but I'm not sure that helps me really. As far as time alignment is concerned both subs are equal distance from the listening position. They are physically time aligned.

 

EDIT: Unless you're suggesting I move one or both to different positions and not equal distance from the listening position?

Edited September 15, 2017 by Satanica

[Pieface]

 

This is as good as I ever got my dual subs to behave together as I had no capacity to delay them relative to each other, only the phase adjustment. The brown trace is the summed response with one sub at 180* phase.  I can't find the picture from them in phase but my recollection is that the response was a lot more ragged and they died in the arse completely under about 40Hz due to cancellation. 

 

Seeing the subs individually gives you a chance to understand where the second sub can "fill in" the gaps of the other subs response. 

 

I think it is hazardous to assume the  response of the subs will be identical to each other due to equidistance. If you have any non symettrical windows, doorways, furnishings etc they may vary more than you think. My subs were also equidistant from my measurement point but admittedly my room is not the preferred rectangle.

 

[Satanica]

6 minutes ago, Pieface said:

 

This is as good as I ever got my dual subs to behave together as I had no capacity to delay them relative to each other, only the phase adjustment. The brown trace is the summed response with one sub at 180* phase.  I can't find the picture from them in phase but my recollection is that the response was a lot more ragged and they died in the arse completely under about 40Hz due to cancellation. 

 

Seeing the subs individually gives you a chance to understand where the second sub can "fill in" the gaps of the other subs response. 

 

I think it is hazardous to assume the  response of the subs will be identical to each other due to equidistance. If you have any non symettrical windows, doorways, furnishings etc they may vary more than you think. My subs were also equidistant from my measurement point but admittedly my room is not the preferred rectangle.

 

Technical issue so I can't see your measurements.

Yes the response will not and is not identical between the two subs.

But in the time domain the first impulse arrives at the listening position at the same time.

When I do the final in room measurement with DEQX the Left and Right "bass" will have both subs operating at the same time.

My system is sounding the best it ever has right now, but I know there is more improvement to be had.

The MiniDSP you recommended has been a great addition.

[Guest]

13 hours ago, Satanica said:

Hmmm, is it?

https://churchtecharts.org/home/2014/8/10/whats-the-difference-polarity-vs-phase

Yea, I get your point but "electrically speaking 180 degrees phase shift can be construed as reverse polarity. one is in time, as where the other electrical polarity

both have same outcome.

In essence what I was getting to is, polarity.

 

Enjoy, I'm home now with can in hand and vibes rolling,,,,,,,,,,,,,,ahhhhhhhhh Friday

[Guest]

my settings on output display in miniDSP 2 x 8, invert low woofers 

 

Ignore what the old analogue 3rd octave real time analizer is showing, is pretty playing music   

 

All this phase shifting. inverting. reversing is making me thirsty

[Pieface]

3 minutes ago, Satanica said:

Technical issue so I can't see your measurements.

Yes the response will not and is not identical between the two subs.

But in the time domain the first impulse arrives at the listening position at the same time.

When I do the final in room measurement with DEQX the Left and Right "bass" will have both subs operating at the same time.

My system is sounding the best it ever has right now, but I know there is more improvement to be had.

The MiniDSP you recommended has been a great addition.

 

I don't have the technical nous to explain this clearly (or possibly accurately) but if you can acknowledge that the summed response of the subwoofers can be varied by adjusting the control on one of the subs...

 

The phase control varies the phase of the signal at the crossover point you have set (as I understand it) and this phase change is not identical as frequency changes. By making an adjustment in the time domain with delay you adjust phase/wave launch/timing/??? equally across all the frequencies. If you could see my picture you can see that the summed FR is much better than either sub individually but there are still areas in the FR where the subs are cancelling eachother (out of phase) and summing with increased SPL (in phase). I believe with delay adjustment rather than a phase adjustment it is possible to get more (all?) constructive summing across the frequency band of the subs.

 

I think 

 

Hopefully someone who understands things better can either clarify my point or shoot me full of holes.

[Satanica]

2 minutes ago, Pieface said:

 

I don't have the technical nous to explain this clearly (or possibly accurately) but if you can acknowledge that the summed response of the subwoofers can be varied by adjusting the control on one of the subs...

 

The phase control varies the phase of the signal at the crossover point you have set (as I understand it) and this phase change is not identical as frequency changes. By making an adjustment in the time domain with delay you adjust phase/wave launch/timing/??? equally across all the frequencies. If you could see my picture you can see that the summed FR is much better than either sub individually but there are still areas in the FR where the subs are cancelling eachother (out of phase) and summing with increased SPL (in phase). I believe with delay adjustment rather than a phase adjustment it is possible to get more (all?) constructive summing across the frequency band of the subs.

 

I think 

 

Hopefully someone who understands things better can either clarify my point or shoot me full of holes.

Yes, but I think I have this covered.

I'm not using any direct phase adjustment, only the crossover (indirect phase adjustment).

I measured the bass units and subs independently from one another using DEQX first.

I switched off each individual unit and measured them independently.

That's how I worked out to delay the bass units by 9.35ms in the MiniDSP so the subs would have time to could "catch up".

[Guest]

Is a dark art this room EQ thing 

I feel we are on the right track @Pieface  

use the catch up theory myself like Santanica.

sounds good when the music is playing

[Pieface]

27 minutes ago, Satanica said:

Yes, but I think I have this covered.

I'm not using any direct phase adjustment, only the crossover (indirect phase adjustment).

I measured the bass units and subs independently from one another using DEQX first.

I switched off each individual unit and measured them independently.

That's how I worked out to delay the bass units by 9.35ms in the MiniDSP so the subs would have time to could "catch up".

Do you have these graphs?

 

The point of running dual subs with a mono signal is to provide smoothing of the FR. To get this smoothing you may need to physically move them, make adjustments to time and/or phase relationships. If you aren't worried about trying to smooth the FR you may as well turn one of the subs back into cash.

 

Imagine that the summed FR of your mono subs improves with a 7ms delay on one of your subs. In your MiniDSP you will simply have that sub at (7+9.35) 16.35ms and the other sub at 9.35ms delay to you big red bass units. Stuffed that up sorry. Just have to work out the correct delay chain now I have conuised myself lol.

 

 

 

 

I am glad that things are sounding good and I also agree there is room for improvement  You shouldn't have to suck up that 16dB null with the gear you have. If one of the subs, in a suitable location, doesn't display the 38Hz null...that performance is there for the taking with all the DSP you have at your fingertips. 

 

Must be beer-o-clock for sure!

Edited September 15, 2017 by Pieface
I am daft

[Satanica]

2 minutes ago, Pieface said:

Do you have these graphs?

 

The point of running dual subs with a mono signal is to provide smoothing of the FR. To get this smoothing you may need to physically move them, make adjustments to time and/or phase relationships. If you aren't worried about trying to smooth the FR you may as well turn one of the subs back into cash.

 

Imagine that the summed FR of your mono subs improves with a 7ms delay on one of your subs. In your MiniDSP you will simply have that sub at (7+9.35) 16.35ms and the other sub at 9.35ms delay to you big red bass units.

 

I am glad that things are sounding good and I also agree there is room for improvement  You shouldn't have to suck up that 16dB null with the gear you have. If one of the subs, in a suitable location, doesn't display the 38Hz null...that performance is there for the taking with all the DSP you have at your fingertips. 

 

Must be beer-o-clock for sure!

Yes I do have them.

 

I know what the point of having dual subs is. I think I understand what you're saying but I don't know how I would work out that my FR improves with a 7ms delay other than trial and error. But I did suggest to myself in this thread that maybe I should try running at least one of the subs out of phase (90, 180, 270, 360?). This is basically the same idea you're talking about, I think.

 

[Pieface]

I don't know how you would find out the required delay without trial and error. I would probably attempt some bracketed measurements and see if I could hone in from there. How long in ms is a 30Hz wavelength? ~33ms? 6 or 7 measurements at 5ms intervals should paint a picture as you go through 360* of phase shift.

 

(Totally spitballing here : ) )

 

You DEQX gave you calculated delays for bass to midrange...can you trick it into doing this calculation on the subs? I know the impulse response is very indistinct on subs...needs the high frequencies to make it nice and pointy so maybe it wont work or the DEQX uses bandpassed signals for the test?

 

 

Edit:

 

If you have the individual measurements of the subs and one sub has good output where you have a null in the summed response. That is the frequency you should examine with your trial and error.

 

Edited September 15, 2017 by Pieface

[Satanica]

5 minutes ago, Pieface said:

Your DEQX gave you calculated delays for bass to midrange...can you trick it into doing this calculation on the subs? I know the impulse response is very indistinct on subs...needs the high frequencies to make it nice and pointy so maybe it wont work or the DEQX uses bandpassed signals for the test?

No, a DEQX is only a 3 way system so I can't use it to time align what is effectively a 3.1 way system. But that's where the MinDSP comes into it.

I've done two phases of time alignment, first the bass units to the subs in MiniDSP.

Then the "bass" (bass units and subs running together) to the top units.

[Satanica]

I'm quietly confident if I placed one of the subs at the back of the room the large 38Hz large dip could be filled in.

[Pieface]

If you got the DEQX to give you a delay between the active big red section and the subwoofers...what would happen if you plugged in one sub so the DEQX "saw" it as the big red active section and the other sub as normal? This is what I meant by trick it.

 

It would purely be to get the delay number (if any) as a shortcut to use in the minidsp. You wire everything back to normal after that.

 

You could well fill in the 38Hz dip moving one of the subs. My experience from shuffling subs all around the room is that you change the FR a lot. Being able to say that I had improved the FR was a a lot harder as previously good areas suddenly had nulls or big peaks. 

 

If you have a nice rectangular room, have you tried the multisub optimiser from down the page? I haven't looked at it closely but it may even be able to suggest delays as well as locations on each sub IIRC from a skim read of it.

 

Anyway you probably think I am FOS at this point  I just think it would be possible to get more even bass with all the gear you have now. Good luck

 

[Satanica]

18 minutes ago, Pieface said:

If you got the DEQX to give you a delay between the active big red section and the subwoofers...what would happen if you plugged in one sub so the DEQX "saw" it as the big red active section and the other sub as normal? This is what I meant by trick it.

 

It would purely be to get the delay number (if any) as a shortcut to use in the minidsp. You wire everything back to normal after that.

 

Anyway you probably think I am FOS at this point  I just think it would be possible to get more even bass with all the gear you have now. Good luck

 

My method was similar to the subwoofer time alignment in the DEQX manual. DEQX didn't give me the measurement delay between the bass units and the subs. I simply measured each one individually (using DEQX) after applying the 80Hz-48db crossover split to each one. As kinda expected, the subs first impulse was behind the bass units. So I put that amount into MiniDSP to slow down the bass units. I don't really understand what you're suggesting (sounds complicated) so I don't know how it might help. I'll have to think about what you're suggesting.

 

I believe I have the correct delay number in use in the MiniDSP now.

 

No no, not at all mate. You pushed me towards the MiniDSP and mono subwoofering, I'm grateful. But between work and this my head is spinning, time for a . And yes I haven't given up just yet at getting some more better bass.

Edited September 15, 2017 by Satanica

[Pieface]

OK...My lack of experience with the DEQX is not helping the conversation - sorry!

 

The DEQX must have some sort of timing reference within itself...which makes sense if you are supposed to be able to time align speaker drivers with it.

 

If you overlay the impulse responses of the individual subwoofer sweeps you made, are they identical or offset in time like they were with the big red bass unit?

 

 

[Satanica]

17 minutes ago, Pieface said:

If you overlay the impulse responses of the individual subwoofer sweeps you made, are they identical or offset in time like they were with the big red bass unit?

Good question! They are not identical but the first impulse peak time is.

Edited September 15, 2017 by Satanica

[Pieface]

OK Cool so the timing looks pretty good given that.

 

So if you post the FR graphs we will see if there is a complementary nature to the individual responses ie where one has a null the other sub has good output. I am suspecting not but I have been known to be wrong before. 

 

I have tried to attach that danged image again so hopefully it comes up this time. From the individual responses i knew I could get a pretty decent summed response if I could get them timed well together. Within the limitations of the adjustments I had available I would say it was pretty successful (brown is summed response)

 

[almikel]

 

 

On 9/14/2017 at 5:13 PM, almikel said:

Have you considered using the mini dsp for the top end xover instead?


Sent from my iPhone using Tapatalk

 

On 9/14/2017 at 5:17 PM, Satanica said:

Not at all.

something to consider...

...for some reason everyone (me included) seeks to split the low end when going 4 way with a single DEQX unit - I don't know why?

 

It makes more sense to split the high end, that way you have a single interface (DEQX) to manage EQ and time alignment where you need it most - the bottom end...

 

...take a typical scenario, where you need to delay mains more than subs - if your Mini DSP is daisy chained on the analog L1/R1 output of the DEQX - you need to manage time alignment in DEQX and MiniDSP.

 

Much easier to use the MiniDSP on the high end (preferably connected to DEQX digitally to avoid another ADC/DAC conversion). DEQX can still do speaker correction over the top of the Xover driving tweeter and mid.

 

That will allow simpler setup/config of bass to sub Xover with only DEQX involved. The Sub channels can be mono'd, and 2 subs can be managed individually delay wise.

DEQX Room EQ will be easier without an extra device in the middle.

Just my 2c - having been in your position prior to going double DEQX.

 

cheers,

Mke

 

[Satanica]

55 minutes ago, almikel said:

 

 

 

something to consider...

...for some reason everyone (me included) seeks to split the low end when going 4 way with a single DEQX unit - I don't know why?

 

It makes more sense to split the high end, that way you have a single interface (DEQX) to manage EQ and time alignment where you need it most - the bottom end...

 

...take a typical scenario, where you need to delay mains more than subs - if your Mini DSP is daisy chained on the analog L1/R1 output of the DEQX - you need to manage time alignment in DEQX and MiniDSP.

 

Much easier to use the MiniDSP on the high end (preferably connected to DEQX digitally to avoid another ADC/DAC conversion). DEQX can still do speaker correction over the top of the Xover driving tweeter and mid.

 

That will allow simpler setup/config of bass to sub Xover with only DEQX involved. The Sub channels can be mono'd, and 2 subs can be managed individually delay wise.

DEQX Room EQ will be easier without an extra device in the middle.

Just my 2c - having been in your position prior to going double DEQX.

 

cheers,

Mke

 

Hi, here's my bunch if excuses not to.

 

I don't have any digital outputs on my DEQX so that rules out avoiding a ADC. I have mono'd the subs with the minDSP 2x4 HD, it quite simply facilitates this. I can and have managed the delay of each sub individually, once again the miniDSP 2x4 HD provides such functionality. And I really don't want to do a speaker measurement and correction because I think my brain might pop. 

 

Cheers. 

[almikel]

23 minutes ago, Satanica said:

Hi, here's my bunch if excuses not to.

 

I don't have any digital outputs on my DEQX so that rules out avoiding a ADC. I have mono'd the subs with the minDSP 2x4 HD, it quite simply facilitates this. I can and have managed the delay of each sub individually, once again the miniDSP 2x4 HD provides such functionality. And I really don't want to do a speaker measurement and correction because I think my brain might pop. 

 

Cheers. 

fair enough