Comments

Info & Answers
Acoustics Matter: Easy Home Theater Audio Tweaks
image
March 13, 2013 | by .(JavaScript must be enabled to view this email address)
7 Tips to Improve Your Home Theater’s Sound
View this entire articleView this entire article
Back to top
10 Comments (displaying chronologically) Post a comment
Posted by Tim  on  02/25  at  01:04 PM

Why on earth would you put two subs on opposite walls?  Comb filtering anyone?  If you’re using two, you want to couple them, which means putting them close together (actually within 2/3 of the wavelength of the sub LPF).  So sure, that could work in a small room on opposite walls, but then why do you need two subs?

Posted by Lance Fletcher  on  02/25  at  01:31 PM

Sorry to disagree with you, but I’ve always found corner placement of sub-woofers to be problematic, as bass frequencies load up in corners, creating more “muddy” bass with to much “boomy” mid-bass and not enough tight, clean deep bass. Also, asymmetrical placement along the front wall (not in corners) is preferred to help even out bass performance throughout the room. In what situations have you found corner placement beneficial?

Posted by Nyal Mellor  on  02/25  at  02:03 PM

Tim / Lance

Actually multiple subwoofers can smooth bass response. The famous paper by Todd Welti shows how different combinations of subwoofers (two vs four; placement mid wall vs placement in corners) can reduce seat to seat variability in bass response - see this article for more details and a link to the original paper: http://blog.acousticfrontiers.com/whats-new/2010/10/29/using-multiple-subwoofers-to-improve-bass-the-welti-devantie.html

You can also use multiple subwoofers to cancel room modes by placing them in opposite polarity ‘lobes’ of the mode in question http://blog.acousticfrontiers.com/whats-new/2010/10/26/using-subwoofers-to-improve-sound-quality-part-2-room-modes.html

Nyal - Acoustic Frontiers

Posted by Greg Robinson  on  02/25  at  03:08 PM

You can always count on subwoofer placement recommendations to get folks riled up.  :-)  As Nyal correctly states, using multiple subwoofers does tend to even out your bass response, and it was in fact the white paper from Harman’s Tom Welti I was referring to when I said, “There have been studies…” (Read it here: http://tinyurl.com/5spmjhg

Lance, as to your question, all I can say is that EVERY room is different and you owe it to yourself to experiment to find what works best in YOUR space.  The photo at the bottom of the above article (with Casino Royale on the screen) is actually a shot of my basement theater. That was taken when I only had one 12-inch sub in the front-right corner (hidden in this photo). Since this photo shoot, I’ve experimented and had great results with a second sub in the front left corner.  Friends and visitors agree, telling me the bass sounds much improved since the change. As with everything home theater - your mileage may vary.

Thanks for reading, guys.

Posted by Chuck  on  02/25  at  03:53 PM

And so often, two subs in opposite corners cancel each other out. I had a client once who did this and thought their subs were broken; no out put at all. But then when they looked at the woofers (drivers) and they were moving a lot! We told them to place the second sub closer to the first, problem solved.

Posted by Grant Clauser  on  02/25  at  04:20 PM

I think the lesson here (regarding subwoofers) is to try multiple placements. You may need to move things around a couple of times before you find best solution for your room.

Posted by Lance Fletcher  on  02/26  at  09:11 AM

Greg,

Your assertion that all rooms are different has nothing to do with the fact that corner sub-woofer placement in ANY room is not ideal and creates problems. While corner placement will give you more apparent bass, certain frequencies load up in the corners - so please don’t confuse the slightly increased volume this creates as a sound improvement, which is what I suspect happened to you with your corner placement.

2 stereo subs on the front wall asymmetrically placed (away from corners) is still the most desired layout - NO MATTER WHAT THE ROOM IS LIKE! I’ve been in this industry for over 30 years and have helped thousands of customers with their room acoustics and have never found a situation where corner placement of sub-woofers improved the bass - it only provided more apparent bass output, which also tended to be less accurate bass. Maybe you should try moving your subs in from the corners, as I contend that you will have tighter, cleaner and more accurate bass response by doing so - plus more even bass dispersion throughout the room with the asymmetrically placed stereo subs closer to each other in the front of the room.

Posted by Greg Robinson  on  02/26  at  09:36 AM

Lance, let me make one final clarification before moving on here. My two subs are not slammed into my front corners. One is about a foot from the side wall, whereas the other is about two feet from its side wall. Each is about one foot off of the front wall.  I will experiment further by moving them inwards/closer to each other and let you know if it makes further improvement. And I am not confusing increased volume with sound improvement, but I do appreciate your concern.

Posted by Allan Sonac  on  02/28  at  09:28 PM

Yes, I agree regarding the information about the 2 subs cancelling each other out…this is called “standing waves”. Bass frequencies are very long sinusoidal waves that can sometimes be several feet in length. The best way to ensure that your 2 subs are not cancelling each other out is by: A. Moving the subs to different areas of the room…even front to back.
    B. Most good subs have a “phase” knob that allows you adjust the wave form and thereby find a sweet spot so that bass is not cancelled by up to 180 degrees.

A sub can even cancel out the bass that is inherent with in the main or surround speakers too…so proper subwoofer placement is really a trial and error installation frequently requiring a second person (friend) that will move the sub and play with the phase setting while the other person uses his ears and possible an SPL meter

If you are using an SPL meter like the one I have from Radio Shack, you should use a tripod and the setting on the meter should set to…C weighted and also set to slow response. This gives you a better average. I use a disc with different test tones while calibrating the output set at 80 dbs.

Posted by Allan Sonac  on  02/28  at  09:39 PM

Also one other comment. The newest receivers from Pioneer Elite series Yamaha and other brands have Advanced MCAA speaker calibration software and a microphone. In fact the Pioneer receivers have an auto-detection mode that when you plug in the microphone it is detected by the receiver sending in to calibration mode. I have used both methods to calibrate surround sound systems and I must say that the software provided by Pioneer is one of the best I have ever seen. You can even download the software from their web site and install it on a laptop which you can then connect to your receiver to make even the most minute and custom adjustments…then save them to the receiver and also to your laptop. The Pioneer Elites (and possibly other brands) even let you save more than one setting! I suppose that’s useful if you prefer a personal “sweet spot” setting when you’re alone and a wider area setting. I find this just incredible and amazing. You can even download apps for the Apple iphone that allow you to control your receiver!

Page 1 of 1 pages


Commenting is not available in this weblog entry.