Accurate subwoofer levels - Page 10 - Home Theater Forum and Systems -

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post #91 of 116 Old 10-13-08, 04:39 AM Thread Starter
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Re: Accurate subwoofer levels

I couldn't believe how much my walls were shaking with FOTR "The bridge" scene even at -14 from reference. This entire time nothing was really happening and it's all because of the gain being set too low. Thing is, I would never have suspected this before as my target calibration SPL was accurate.

Would I expect to see any gains over and above 40% for gain ? I mean, before I had the gain set to below 20% to reach the same SPL level. I do have two subwoofers so that would mean that my gain levels would need to be set lower to maintain the same SPL level. Would I run into any problems again or should it be fine ?

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post #92 of 116 Old 10-13-08, 06:16 AM
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Re: Accurate subwoofer levels

I experienced something similar when I started using the bypass input on my sub - now I control the LFE level through the preamp instead of the knobs on the back of the sub and it is much more impactful.
post #93 of 116 Old 10-13-08, 06:29 AM Thread Starter
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Re: Accurate subwoofer levels

I think I might sell the second MFW-15 now. I mean, there simply is no need. Calibrating flat and Eq'ing flat has it's advantages, like huge headroom increases. I don't think I will run out of steam running my system this way at reference.

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post #94 of 116 Old 10-25-08, 11:59 PM
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Re: Accurate subwoofer levels

The Wire-Steven,
Did you say that your subs are stacked in an earlier posting? I would not recommend this. The reflected frequencies from the floor will be different from each driver. If space allows you may want to try placing both side by side, cabinet to cabinet and away from sidewalls.

Last edited by Synthsayer; 10-26-08 at 12:13 AM. Reason: Identify to whom reply intended for
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post #95 of 116 Old 10-26-08, 12:39 AM
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Re: Accurate subwoofer levels

I think a worst room contest would be humorous and helpful. I always thought I had the worst room. Now I know others feel the same. It will drive you nuts with setting up your home theater system, especially the sub. My room is similar in that it does not have doors nor parallel walls of equal length. If I stand in one part of the room, I hear one dominant frequency, standing in another part, the same thing. The speaker that worked the best is an old, old, Electr-Voice Aristocrat Corner horn that has a really flimsy baffle board and no place to mount plate sub amp.
As I have said in other threads, I use the O-Audio 500W BASH sub amp with Harman Kardon AVR 154. Sub amp has a very nice EQ and low boost, plus variable phase. This helps the user to integrate the sub very well even in the worst of rooms.
If you have the Thiele-Small info of your sub and even better, the woofers in your front and rear speakers you can use several free programs to model their approx response. One of these is Jeff Bagby's Woofer Box and Circuit Designer the other is WinISD Beta from LinearTeam Both of these will give you the phase per given frequency. I just started working with Woofer Box and Circuit designer but was able to see exactly howthe Paramtric EQ and Crossover settings affected the sub. This gave me a reasonable starting point as well as the info from WinIsd Beta that showed both the woofers in the fronts and the sub driver had a phase plot of about 43 degrees at 80Hz.
I still had too much of a room mode around 40 Hz and quickly adjusted EQ and variable Q to clear it up.
For people that say subwoofer frequencies are omni-directional, don't believe it for a minute when it comes to an irregularly shaped room.

Last edited by Synthsayer; 10-26-08 at 12:42 AM. Reason: typos - its late
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post #96 of 116 Old 10-26-08, 03:38 AM
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Re: Accurate subwoofer levels

Synthsayer wrote: View Post
The Wire-Steven,
Did you say that your subs are stacked in an earlier posting? I would not recommend this. The reflected frequencies from the floor will be different from each driver. If space allows you may want to try placing both side by side, cabinet to cabinet and away from sidewalls.
That's interesting. I wonder if this is the problem I hear when stacking them. There is no absorption on my floor. What happens when I stack them in the corners together (that was just an experiment with the front) was not very clear with audible testing, but they did in fact measure very different as you point out. I found that having two stacked in my front left corner, and two stacked in the back right corner had some good LFE, but I had trouble with the high frequencies of the sub woofers. I had written it off as a problem with transients as one side of the room would seem to have a different speed and distance to the higher sounds. It very well could be related to the floor. For some reason I had smoother response at the seats on the other side of the room closest to the subs when they were stacked. My four sub woofers are currently sitting on my stage in a horizontal position/ horizontal array. I'm not sure what effect having them raised would have on the response as it only seemed to effect the 50Hz - 180Hz area, with some variance in the ringing down low. I think I have enough absorption in my stage but I have thought about adding some heavy material over it. I will have to test that sometime but with REW but listening test are good. The ports are only inches away from my front wall, but I have had zero problems. I still have more room treatments in the plans, and in fact I had the same problem with the door slamming around since adding some newer treatments, similar to when I had them stacked, only it was a sound that subsonic doing it I discovered. I had to rig up an extra set of weatherstripping on the door. There are two strips that if I use the door needs to be pulled very hard before turning the door knob, so those two are reserved for the movies with lots of bass.
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post #97 of 116 Old 03-06-09, 09:54 PM
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Re: Accurate subwoofer levels


I'll just give my .02 as to what I have my subs set to. I originally had a PB12-NSD which was great, the I bought a 13Ultra....massive improvement! I then bought a second 13Ultra. With the NSD and single Ultra I found that the sub calibrated to 72-73db on the RS meter was not nearly enough for my tastes and what I think the movie should sound like. A movie for example like Transformers with an Ultra, in a 110sq ft room should pound but it does not. when calibrated to 72-73db but sounds much more alive when calibrated to approximately 8db higher. Now with my dual Ultras (collectively set to 83-84db taking into consideration the lower reading on the RS meter) it sounds quite good.

So TonyVb I agree with you, the LFE set higher than the mains sounds substantially better.

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post #98 of 116 Old 03-07-09, 10:59 PM
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Re: Accurate subwoofer levels

Thanks for the tips Synthsayer (only took me three months to get around to reading them). I think worse room response competition is a great idea. How about a prize for the best corrected/eq'ed room?

Anyway, I've since shifted houses and guess what? I'm now in another bl**dy L-shaped room (replete with hole in the wall to outer corridor). I'm cursed

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post #99 of 116 Old 04-14-09, 02:15 AM
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Re: Accurate subwoofer levels

Hello people. I still need a few more posts to hit 5 so another 2 cents worth here:

I find that a flat frequency response is very much a desirable thing for listening to good music recordings. IMO a pair of big stereo speakers is much better than a pair of satellites and a monaural sub due to loss of LF stereo positioning. A good demonstration of left and right bass is on the Telarc Tchaikovsky Nutcracker Soundtrack CD (Mackerras LSO) which has contrived cannon shots left then right which sound like they are spread somewhat around the 40 Hz mark. The directional effect would be lost with a single mono sub.

For movies mono subs are fine, but I see the discussion of flat reponse a bit silly since all of the LF detail on the recording is contrived anyway. I see no need to strive for super flat subwoofer response as it will in most cases be ruined by room effects which are in some cases impossible to correct even with a multi-band subwoofer equaliser. I have toyed with the idea of building a dual driver (push-pull) bandpass sub having a slight RISE in output with diminishing frequencies in the pass band. So long as it crossed over reasonably well to the other speakers (say around 80 Hz or so), a gradual rise down to say 25 or so Hz could be very desirable. I have modelled a pair of 18 inch JBL drivers with WinISD and it looked very interesting indeed as a HT sub. Group delay considerations (almost as bad as ported) and a rollercoaster cone excurson curve had me do something else with the drivers, but food for thought.
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post #100 of 116 Old 04-14-09, 05:29 AM
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Re: Accurate subwoofer levels

If you build a subwoofer with very little distortion (harmonics), and lopass it at 80Hz with mains taking over, and do a good transition, I'd say you have ears like an wolf if you can localize the subwoofer. It's not the <80 you localize it's the higher frequency distortion.
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