Stereo subwoofer setup strategy

[Boomzilla]

New subs are coming. My room dictates placement of the two subs along the "speaker wall." My initial intent is to place the two subs equidistant from their respective side walls.

To set level, I'll put a SPL meter at the listening position & then play an 80 Hz. tone through the speaker only (one side at a time and with no sub). Once I know that "reference" level, I'll turn off the speaker's amp and turn on the sub. I'll then play the same tone and adjust the sub's gain until the level matches the speaker. This gives me equal output from both the speaker and the sub.

To adjust phase, I plan to play a repeating test tone at the crossover frequency (80 Hz.?) I'll place a SPL meter halfway between the speaker & the sub, but with the speaker wires in inverse phase. I'll then adjust the sub delay to achieve the lowest SPL I can get (maximum cancellation) at the SPL meter. Once that delay is determined, I'll then reverse the leads on the speaker, and the speaker-to-sub phase will be optimized.

To adjust room frequency response, I'll put the UMIK-1 microphone at the listening position and play a sweep through the sub. Any peaks in response are due to resonance (that will be different for the two subs). I'll use jRiver's digital signal processing to apply parametric equalization for each channel until I have the flattest response (no boost - just reduction of peaks). This should equalize each sub to the room.

Next, I'll turn both subs on and with the UMIK-1 at the listening position, I'll play a stereo sweep through both subs simultaneously. Any peaks created are resonances between the two subs themselves. Again, I'll use jRiver's digital signal processing to apply more cuts where needed. This should optimize the pair of subs responses in the room.

Finally, I'll turn on the speakers AND the subs and with the UMIK-1 still at the listening position, measure the crossover area. Any peaks can again be added to the DSP profile for maximum smoothness at the crossover frequency.

Did I miss anything?

Thanks, Boom.

[DYohn]

My advice: do not set equidistant from side walls to avoid reinforcing reflected waves. A foot or two difference generally yields better results.

[Boomzilla]

Thanks, David - you're right! I was thinking of visual symmetry, and I should have been thinking of room reflections.

[donh50]

Can you put one in a back corner? That can help with room modes... The Harman website has a nice article and spreadsheet you can use to help, and REW has a placement tool for rectangular rooms.

[Boomzilla]

Typical "rectangular room" placements have tended NOT to work for me because my room is vented at all four corners. The "subwoofer crawl" would do the trick, but to date, I've been too lazy to make it.

[novisnick]

Oct 12, 2018 18:07:14 GMT -5 Boomzilla said:

Typical "rectangular room" placements have tended NOT to work for me because my room is vented at all four corners. The "subwoofer crawl" would do the trick, but to date, I've been too lazy to make it.

Great sound requires great effort!,,,,,,,,,,,,,,,,well, it sounded good!

Now go get er done! 😁🎶🎶🎶🎶🎶🎶🎶🎶🎶

[donh50]

If you're willing to make the effort, REW could help... Free SW, buy an inexpensive (<$100) USB mic (UMIK-1) from miniDSP (or calibrated version from CSL), then you can tweak and measure. Might have to get over the laziness, though...

Equidistant may work but it very much depends upon the room and how (and where) the modes line up. My subs are in two pairs, with each sub in the pair symmetric with its mate, but the two pairs are spaced differently so as to minimize a couple of room modes and compensate a null at the main listening position (MLP). The front pair is a couple of feet in front of the front wall, and the rear against the rear wall, to provide the best sound and work with the placement options I have in my room.

[Boomzilla]

Hi donh50 -

Thank you. Yes, I have a calibrated UMIK-1 microphone and REW. So far, I've properly phased each sub to its satellite. Not-surprisingly, the "zero phase" setting for the subwoofers was NOT the best setting for matching even when the sub was relatively close to the satellite.

My subs are different distances from the side walls, although they're still equidistant from the wall behind them. This may be a necessity lest they become tripping hazards. Today, I may set up the microphone again and measure each sub's "in room" response from the listening position (phasing was done relatively near-field and at the specific intended crossover frequency). Once each sub's in-room response is flattened with DSP, then I can run a combined sub + satellite in-room response to finely match levels.

The "subwoofer crawl" just isn't in the near future due to furniture, etc.

[DYohn]

Oct 13, 2018 5:07:51 GMT -5 Boomzilla said:

Hi donh50 -

Thank you. Yes, I have a calibrated UMIK-1 microphone and REW. So far, I've properly phased each sub to its satellite. Not-surprisingly, the "zero phase" setting for the subwoofers was NOT the best setting for matching even when the sub was relatively close to the satellite.

My subs are different distances from the side walls, although they're still equidistant from the wall behind them. This may be a necessity lest they become tripping hazards. Today, I may set up the microphone again and measure each sub's "in room" response from the listening position (phasing was done relatively near-field and at the specific intended crossover frequency). Once each sub's in-room response is flattened with DSP, then I can run a combined sub + satellite in-room response to finely match levels.

The "subwoofer crawl" just isn't in the near future due to furniture, etc.

My suggestion:
First, just listen to the setup. Put on a variety of music you know and like and sit and listen for a while. If you hear anything obviously "wrong" make a note of it (on paper helps) and then change the track and listen a little more. If it's a dual use system watch some TV or a movie and make more notes. If it sounds OK to you live with it a while as-is and then make more notes again tomorrow.

Then, break out the measurement gear and take a set of bass sweep readings at your primary listening location. Don't worry about the raw data, smooth the graph and use A weighting to view what your ears likely hear, and switch it over to C weighting if you can to look at relative bass loudness. Look for peaks or nulls at +/- 10db from the average. Refer to any notes you made about issues and see if the FR reveals any likely suspects. Before you start adding filters or EQ or worrying about room treatments look for any obvious room modes, again focusing on 10db changes not 3 or 4. Think about alternative placement for ONE of the subs and if you can, move it. Depending on the frequency of the issue sometimes moving only a few feet can make a huge difference. Since your new systems are down-firing (I believe you said) then rotating them will not help. If you have big peaks at one of the fundamental reverberation frequencies of your room geometry, then corner bass traps might help. And remember that the wall-to-ceiling interface is the least considered "corner" in most home listening environments.


But mostly, seek enjoyment not a perfect FR curve. If it sounds good to you then that is what matters. My room has several measurement-related issues that I could attack if I had OCD, but I think it sounds good so why bother? To make it "better?" Maybe. Maybe not. Your measurement mic can "hear" far better than your human ears can.

[simpleman68]

Oct 13, 2018 10:29:11 GMT -5 DYohn said:

Oct 13, 2018 5:07:51 GMT -5 Boomzilla said:

Hi donh50 -

Thank you. Yes, I have a calibrated UMIK-1 microphone and REW. So far, I've properly phased each sub to its satellite. Not-surprisingly, the "zero phase" setting for the subwoofers was NOT the best setting for matching even when the sub was relatively close to the satellite.

My subs are different distances from the side walls, although they're still equidistant from the wall behind them. This may be a necessity lest they become tripping hazards. Today, I may set up the microphone again and measure each sub's "in room" response from the listening position (phasing was done relatively near-field and at the specific intended crossover frequency). Once each sub's in-room response is flattened with DSP, then I can run a combined sub + satellite in-room response to finely match levels.

The "subwoofer crawl" just isn't in the near future due to furniture, etc.

My suggestion:
First, just listen to the setup. Put on a variety of music you know and like and sit and listen for a while. If you hear anything obviously "wrong" make a note of it (on paper helps) and then change the track and listen a little more. If it's a dual use system watch some TV or a movie and make more notes. If it sounds OK to you live with it a while as-is and then make more notes again tomorrow.

Then, break out the measurement gear and take a set of bass sweep readings at your primary listening location. Don't worry about the raw data, smooth the graph and use A weighting to view what your ears likely hear, and switch it over to C weighting if you can to look at relative bass loudness. Look for peaks or nulls at +/- 10db from the average. Refer to any notes you made about issues and see if the FR reveals any likely suspects. Before you start adding filters or EQ or worrying about room treatments look for any obvious room modes, again focusing on 10db changes not 3 or 4. Think about alternative placement for ONE of the subs and if you can, move it. Depending on the frequency of the issue sometimes moving only a few feet can make a huge difference. Since your new systems are down-firing (I believe you said) then rotating them will not help. If you have big peaks at one of the fundamental reverberation frequencies of your room geometry, then corner bass traps might help. And remember that the wall-to-ceiling interface is the least considered "corner" in most home listening environments.


But mostly, seek enjoyment not a perfect FR curve. If it sounds good to you then that is what matters. My room has several measurement-related issues that I could attack if I had OCD, but I think it sounds good so why bother? To make it "better?" Maybe. Maybe not. Your measurement mic can "hear" far better than your human ears can.

This is good to hear since I don't have much experience with sub tweaking/placement and tend to overthink things.

I have everything I need to run REW but haven't gotten around to it yet.

Really been wanting to do this in the theater but for now I'm running just the 1 sub as the other one winds up cancelling out the other.

Funny how some folks think more is better and that somehow you can magically pressurize a room by adding gobs of subs.

I've actually gotten incredible response from 1 sub by moving it to the sidewall about 1/3 of the way from the rear of the theater.

Time to make some time to do the crawl. Just need to figure out how to do it most effectively with 2 subs. I guess do the crawl with 1 sub first and then

do it again with the 2nd while the 1st sub is active?

Scott

[donh50]

Oct 13, 2018 5:07:51 GMT -5 Boomzilla said:

Hi donh50 -

Thank you. Yes, I have a calibrated UMIK-1 microphone and REW. So far, I've properly phased each sub to its satellite. Not-surprisingly, the "zero phase" setting for the subwoofers was NOT the best setting for matching even when the sub was relatively close to the satellite.

My subs are different distances from the side walls, although they're still equidistant from the wall behind them. This may be a necessity lest they become tripping hazards. Today, I may set up the microphone again and measure each sub's "in room" response from the listening position (phasing was done relatively near-field and at the specific intended crossover frequency). Once each sub's in-room response is flattened with DSP, then I can run a combined sub + satellite in-room response to finely match levels.

The "subwoofer crawl" just isn't in the near future due to furniture, etc.

Sounds like you're good to go!

Agree completely with "non-zero" phase being more likely. Crossovers (in the speaker and in the electronics) induce a lot of phase shift, then you have the effects of speaker ports, electrical delay through the electronics (usually small but not always, especially when DSP is involved), etc.

I wouldn't worry too much about placement if you are constrained by other things unless things are really bad. We all have to live in the room, and that includes not tripping over a sub in an open doorway because that's where the response measured best (yes, have seen that, hmph -- anal/OCD indeed). Subs at 1/3 spots along the wall work well if you can do it, or even at 1/4 and 3/4 points. Check out the Harman tool or one of the other placement helpers -- you can get an idea even if the room is more open.

I am not a personal believer in the "crawl" except maybe as a last resort. Too limited in what it provides and too easy to fool yourself without actual measurements. But do realize we are not that sensitive to narrow dips so don;t kill yourself seeking perfection. Getting subs and mains in phase at the MLP (or properly phased to compensate the room and everything else) at the crossover frequency is usually most important. Above and below the crossover, subs/mains contribute less so integration becomes less important.

[DYohn]

Oct 13, 2018 10:39:02 GMT -5 simpleman68 said:

This is good to hear since I don't have much experience with sub tweaking/placement and tend to overthink things. have everything I need to run REW but haven't gotten around to it yet.

Really been wanting to do this in the theater but for now I'm running just the 1 sub as the other one winds up cancelling out the other.
Funny how some folks think more is better and that somehow you can magically pressurize a room by adding gobs of subs.

I've actually gotten incredible response from 1 sub by moving it to the sidewall about 1/3 of the way from the rear of the theater.

Time to make some time to do the crawl. Just need to figure out how to do it most effectively with 2 subs. I guess do the crawl with 1 sub first and then

do it again with the 2nd while the 1st sub is active?
Scot

If it's just loudness you need and not room response, try stacking the subs. Do the "crawl" if you like with one, then set the second on directly on top of the first to add approx. +6db.

[novisnick]

Thinking of “The crawl” I realize my head and ears aren’t in my butt! Why whould I listen at that height anyway? 🤔 Move the sub and sit in a folding chair to listen for response would be more accurate and much easier on my bod! Close enough I’m sure! 😁😋

[DYohn]

Oct 13, 2018 11:35:35 GMT -5 novisnick said:

Thinking of “The crawl” I realize my head and ears are in my butt! Why whould I listen at that height anyway? 🤔 Move the sub and sit in a folding chair to listen for response would be more accurate and much easier on my bod! Close enough I’m sure! 😁😋

Well you do want to measure and listen at normal seated position ear-height, so whatever that means for you.

[novisnick]

Oct 13, 2018 11:37:42 GMT -5 DYohn said:

Oct 13, 2018 11:35:35 GMT -5 novisnick said:

Thinking of “The crawl” I realize my head and ears are in my butt! Why whould I listen at that height anyway? 🤔 Move the sub and sit in a folding chair to listen for response would be more accurate and much easier on my bod! Close enough I’m sure! 😁😋

Well you do want to measure and listen at normal seated position ear-height, so whatever that means for you.

Exactly! 😏

[musicfan]

You crawl because that is where the sub will be. On the floor

[Boomzilla]

Oct 13, 2018 12:05:30 GMT -5 musicfan said:

You crawl because that is where the sub will be. On the floor

But only if you place the sub where your head will normally be listening from!

[musicfan]

Oct 13, 2018 12:22:24 GMT -5 Boomzilla said:

Oct 13, 2018 12:05:30 GMT -5 musicfan said:

You crawl because that is where the sub will be. On the floor

But only if you place the sub where your head will normally be listening from!

Your overthinking this.

[Boomzilla]

LOL - It's my nature...

[donh50]

As I've said, I do not like "the crawl". But remember that the wavelength at 100 Hz is about 11.27 feet, double that at 50 Hz (22.54 feet), and so forth. A foot or two is not going to make much difference when you are going (crawling) for just a gross idea where it should best be placed.

Since you have REW and only limited places to put the sub, I would set up the measurement mic normally (yes, at ear level, on a mic stand ), then check the response with one sub in the two or three places available and use the spot with the fewest dips. You could move them both around, but for starters I would put one in a good spot in the front, measure and move it a little if it helps, then find a spot for the other elsewhere in the room to optimize the frequency response.

FWIWFM - Don