Home Theater Multiple Subwoofer Set-Up & Calibration Guide

[admin]

The goal of a serious home theater playback system should be even bass, plenty of dynamic range and smooth natural frequency response across all of the listening area for the most seamless blend. The best way of achieving good bass is by reducing the modal peaks and nodal dips by utilizing multiple subs, proper speaker/subwoofer and seating placements and setup, active equalization and passive room treatments. The key is proper subwoofer placement and setup to reduce the guess work and minimize chasing your tail to find the best settings that yield the most optimal measurable performance. This article discusses methods of proper placement, setup and measurements to help achieve the best measurable and audible results for your entire listening area, NOT just the money seat!


Discuss "Home Theater Multiple Subwoofer Set-Up & Calibration Guide" here. Read the article.

[nickboros]

Gene,

Very nice article. I only have one sub now, but I'm hoping in the near future to upgrade to two or four subs.

You don't mention what the phase should be set at for the subs in the three optimal locations. For example in the four subs in corner placement are all the subs set with the same phase? In the midwall placement, with two subs, should the subs be out of phase with one another? In the 1/4 width placement on the front wall, with two subs, should the subs be out of phase?

Thanks,

Nick

[gene]

Gene,

You don't mention what the phase should be set at for the subs in the three optimal locations. For example in the four subs in corner placement are all the subs set with the same phase? In the midwall placement, with two subs, should the subs be out of phase with one another? In the 1/4 width placement on the front wall, with two subs, should the subs be out of phase?

Thanks,

Nick

Phase should almost always be set to zero for all subs. It should only be altered if its beneficial which is usually not the case. I did mention this in the article under Advanced Calibration tips.

[BMXTRIX]

I didn't read the article, but just counted the words. 5,999... You are slacking!

[skers_54]

Fantastic article Gene. I've been trying to integrate two different subs into my system and this really helps. I had actually been using a similar overall method but yours is much more comprehensive and helped me figure out some stuff I've been doing wrong or wasting time with.

Do any of the recommendations change if you have the system setup width-wise rather than length-wise (besides rearrange it )?

[gene]

I didn't read the article, but just counted the words. 5,999... You are slacking!

Actually its more like 8400 words in the word document. should be the same online.

[SnowmaNick]

Gene, great article, thank you.

I have a question on the level matching process if you don't mind?

You mention that when measuring that you should use an equidistant measurement for all subs and that the measurement location may not necessarily be the primary listening position. Where/how exactly should one measure then? I am trying to determine if you mean measure the two/four subs and measure in the center of them, where all the subs are equidistant from the mic and you do not have to try to account for differences in mic placement. Or do you mean choose a distance from a sub to the mic and measure each sub at that distance IE: measure sub one with the mic 36" from the sub, then go to sub 2 and set up the mic 36" from that sub (lather, rinse and repeat as needed).

If the former, what if that equidistant location is the middle of two parallel walls? Won't the walls being equidistant create some null/node/cancellation at that spot but not necessarily at the primary LP causing you to crank one or more subs erroneously?

If the latter, is it best to measure from the sub into the room? This makes the most sense to me but I am unsure how room cancellation and distance may interact with multi subs and may be misunderstanding your advice.

I have a couple of days off to relax next week and am looking forward to trying this methodology out. Thank you in advance and again, great article.

[gene]

Gene, great article, thank you.

I have a question on the level matching process if you don't mind?

You mention that when measuring that you should use an equidistant measurement for all subs and that the measurement location may not necessarily be the primary listening position. Where/how exactly should one measure then? I am trying to determine if you mean measure the two/four subs and measure in the center of them, where all the subs are equidistant from the mic and you do not have to try to account for differences in mic placement. Or do you mean choose a distance from a sub to the mic and measure each sub at that distance IE: measure sub one with the mic 36" from the sub, then go to sub 2 and set up the mic 36" from that sub (lather, rinse and repeat as needed).

If the former, what if that equidistant location is the middle of two parallel walls? Won't the walls being equidistant create some null/node/cancellation at that spot but not necessarily at the primary LP causing you to crank one or more subs erroneously?

If the latter, is it best to measure from the sub into the room? This makes the most sense to me but I am unsure how room cancellation and distance may interact with multi subs and may be misunderstanding your advice.

I have a couple of days off to relax next week and am looking forward to trying this methodology out. Thank you in advance and again, great article.

Good question. For years, I always measured at the listening area for each sub. It was a pain to match levels that way. Then it occurred to me when reading Dr. Floyd Toole's book that what matters is how the subs balance with respect to the room NOT the listening area. Remember in order to take full advantage of standing wave reduction, all subs must:

• be level matched with respect to each other
• be properly placed
• play exact same mono signal (LFE + all speakers set small)

The easiest way to measure each sub is to place the mic on the floor nearfield to the sub (within a few inches). If all your subs are single driver, then you can measure the SPL at the cone for each. You don't need to turn off the other subs if you do a nearfield measurement b/c the sound from that sub will dominate all others.

After you level match each sub, then go to the listening area and level match the main channels to the combined sub output. Once you flatten the bass of the subs, you can even boost their combined output a few dB over the main channels if you like.

Alternatively you can pick an equadistant point from all subs to measure their SPL individually but that can be difficult if they aren't all symmetrically placed in the room.

[gdsk39a]

Good question. For years, I always measured at the listening area for each sub. It was a pain to match levels that way. Then it occurred to me when reading Dr. Floyd Toole's book that what matters is how the subs balance with respect to the room NOT the listening area. Remember in order to take full advantage of standing wave reduction, all subs must:

• be level matched with respect to each other
• be properly placed
• play exact same mono signal (LFE + all speakers set small)

The easiest way to measure each sub is to place the mic on the floor nearfield to the sub (within a few inches). If all your subs are single driver, then you can measure the SPL at the cone for each. You don't need to turn off the other subs if you do a nearfield measurement b/c the sound from that sub will dominate all others.

After you level match each sub, then go to the listening area and level match the main channels to the combined sub output. Once you flatten the bass of the subs, you can even boost their combined output a few dB over the main channels if you like.

Alternatively you can pick an equadistant point from all subs to measure their SPL individually but that can be difficult if they aren't all symmetrically placed in the room.

I have some questions. I have a rectangular room that is enclosed. I have the following subwoofers in each corner: ED A7-450, EPIK Tower, Sunfire True Signature, and 2 Def Technologies Reference stacked. The 2 Def Techs and Sunfire are hooked up to the Velodyne SMS-1. After calibration I pretty much have a smooth frequency response. I am running the subwoofers a bit hot for impact. The smooth response also includes having my front speakers set to large. They are massive Polk SDA SRS 1.2's.

Concerning phase settings I notice that changing the phase with the Velodyne SMS-1 does affect the frequency distibution. I had to mess with the SMS-1 phase setting to get the perfect frequency response graph for my total setup including fronts set to large.

My question is this. How do you know that you are listening to perfect bass? It sounds great to me, but could my ears be deceiving me as I have nothing to use as a reference. I can tell you the bass impact is phenomenal. All the Bass appears to be coming from my main front speaker stage. It doesn't sound bloated or distorted. Just a bit on the hot side.

Your thoughts.

[xWARHOUNDx]

Or just buy the SVS ASEQ-1

I have two SVS subs and this was the best money I ever spent! I literally had a flat response in 25 minutes...would have been shorter but I wanted to do it again because I "THOUGHT" I had done something wrong because it was so easy. It is expensive but the end results are awesome and you don't have to do all the steps above!