Integrating Four Subwoofers Using REW + MiniDSP

[anjunadeep]

Hello, I have some questions about subwoofer time-alignment and using REW to integrate four identical subwoofers in an odd-shaped room.

I have taken one subwoofer and moved it around to each potential location in my room and taken a measurement with the mic in the MLP. I can place one subwoofer (of four, two which I have already, I'm waiting for the other two to arrive) in these locations. The rear locations require a wireless transmitter (I'm going to use the Outlaw unit).

To integrate these subwoofers, I've been using the Alignment Tool. The alignment tool can handle two measured responses at once, therefore it seems my best bet is to integrate two subwoofers, then use that combined integration to add the third in, and then the same for the forth. Is this the correct process?

The placement combination that, in the end, seems to work the best is as follows:

I first summed subwoofers 1 and 2, and ended up with this:

I added no delay, they are the same distance from my seat as well (plus they're close enough where I think they're pretty much acting as one subwoofer for the longer wavelengths)

Then I added in the third subwoofer in the corner. This third subwoofer, perhaps because it is a bit further from my MLP, caused me to need to add a bit of delay to the first pair for the best response:

I was a bit surprised by the delay needed, but it could be because of the long cable (which I was using to make it so I could move subs around easily) or maybe just the placement. Either way, the best result needed some delay when they combined. So now I figure when I add the rear subwoofer, I'll need to further delay the front subs?

So I added in the fourth sub by taking the aligned 3x subwoofers and using the alignment tool with the fourth (rear) sub:

The fourth sub will eventually be added wirelessly, but for complexity-sake I wanted to tinker with this wired with a temporary wire. Using the Alignment tool I found that the rear sub, which is close to me, would need to be delayed by 16.49ms compared to the front three.

The resultant response of all four subs looks like this (same as above in red, but, repeated for clarity):

This response seems like something that could be EQ'd very lightly to give me a good response (or at least better than I had with two subs).

Questions!
1) After trying multiple placements and tons of combinations, this asymmetrical layout in my odd-shaped open room seems to be best. Is there any downside to this other than aesthetics?
2) When I time-align these in the miniDSP, how would I do that? First 3.19ms was added to both the front right and left subwoofer to combine the front three subwoofers, then the rear subwoofer needed 16.49ms of delay added to combine with the front properly. So do I just type those values in for the delay in miniDSP? S1 (front right) = 3.19, S2 (front left) = 3.19, S3 (right corner) = 0, S4 (rear sub)=16.49
3) When I switch the forth sub to wireless, what's my best way to figure it's delay? The same way I would wired? I remember reading a long time ago about summing all the wired subs as a unit and then letting Audyssey determine the wireless subs distance (I have two sub outputs).
4) At each location I measure, I have a dip between ~8-15Hz... some are worse than others, but every location has this. Is this something related to my ceiling height? I seem to be getting the rest of my response pretty good old to have this problem in the subsonic stuff.

I attached the mdat file in case anyone wants to tinker. Any help appreciated!

 

[jtalden]

Questions!
1) After trying multiple placements and tons of combinations, this asymmetrical layout in my odd-shaped open room seems to be best. Is there any downside to this other than aesthetics?

An asymmetrical SW layout is often advantageous.

2) When I time-align these in the miniDSP, how would I do that? First 3.19ms was added to both the front right and left subwoofer to combine the front three subwoofers, then the rear subwoofer needed 16.49ms of delay added to combine with the front properly. So do I just type those values in for the delay in miniDSP? S1 (front right) = 3.19, S2 (front left) = 3.19, S3 (right corner) = 0, S4 (rear sub)=16.49

That works.

3) When I switch the forth sub to wireless, what's my best way to figure it's delay? The same way I would wired? I remember reading a long time ago about summing all the wired subs as a unit and then letting Audyssey determine the wireless subs distance (I have two sub outputs).

Your method worked well here and should work well again with the wireless SW.

4) At each location I measure, I have a dip between ~8-15Hz... some are worse than others, but every location has this. Is this something related to my ceiling height? I seem to be getting the rest of my response pretty good old to have this problem in the subsonic stuff.

Room or SW related, but that response is very good. If you are sure the SWs are capable that low and want to get there you need to try more SW positions. If it is ceiling related then changing the SW height would likely be needed.

I tried a couple of optional timings. One provided SPL that was roughly the same as yours. The other was a little worse. I don't think the SPL can be improved significantly from your settings.

Multi-Sub Optimizer (MSO) is a more sophisticated automated program. You could look into that if you want investigate further. I haven't used it so I don't know how easy it to use.

 

[anjunadeep]

An asymmetrical SW layout is often advantageous.

That works.

Your method worked well here and should work well again with the wireless SW.

Room or SW related, but that response is very good. If you are sure the SWs are capable that low and want to get there you need to try more SW positions. If it is ceiling related then changing the SW height would likely be needed.

I tried a couple of optional timings. One provided SPL that was roughly the same as yours. The other was a little worse. I don't think the SPL can be improved significantly from your settings.

Multi-Sub Optimizer (MSO) is a more sophisticated automated program. You could look into that if you want investigate further. I haven't used it so I don't know how easy it to use.

Thank you! This helps confirm I'm pointed in the right direction.

Yes, the subwoofers are capable that low - the raw measurements are from the actual subwoofers. How much content is down there? Not much lol. As far as raising the subwoofer higher, I'm kind of out of luck there. I guess I could get some flyware like a nightclub lol.

With the log scale that area between 5-20Hz is huge. Is that how we perceive sound, or am I focusing on an area that is probably not that big of a difference? I mean the same blip at 60Hz would be so much smaller on a graph I'd probably ignore it. Am I overthinking this?

Thanks again for the thoughtful response.

 

[jtalden]

I have no personal experience that low.

 

[Usher99]

Don’t forget about the latency induced by the transmitter. Will need to be redone. It is sometimes worth trying to invert the subs behind you and playing with the delay. Takes a sec with that cool alignment tool to assess if it is better or to be avoided.

 

[Usher99]

3) When I switch the forth sub to wireless, what's my best way to figure it's delay? The same way I would wired? I remember reading a long time ago about summing all the wired subs as a unit and then letting Audyssey determine the wireless subs distance (I have two sub outputs).

Some sub outputs on AVR's are not truly independent. Anyway all tutorials I have watched always recommended aligning all the subs first into one virtual sub and then it is OK to have Audyssey set the delay (distance) to align the virtual sub with the mains. (Can check with alignment tool on REW and empirically check other distances to be sure it is correct) I would not trust your wired 4th sub settings for wireless. For example, the SVS soundpath wireless adapter has a latency of 14ms. I am relatively new at this, but those are my 2c.