How Much Subwoofer Is Enough?

[mj30250]

Well, seems you have hit your bass Nirvana - which is great. Don't think that you can do much more on that front. While more subs will always tend to add a bit more, you don't really seem to need it either in frequency response or SPL. Decay time is a different matter, but as long as it sounds reasonably tight, would not really bother.

Perhaps time to upgrade the bed channels to full towers and try how that works? Also, did you thing of the upcoming Dirac ART?

Agreed, I'm good. Perhaps at some future point I'll add a couple nearfield subs, more for additional tactile response / envelopment than anything, but that would likely be frivolous and then there are the additional challenges that this introduces to the integration process.

I do use towers left and right and a big 3-way center. The plots above are subs-only. They keep up quite well when the volume gets pushed. I tend to get good results from Audyssey (when used with the companion app), so I've not given much thought to Dirac.

 

[wwenze]

 

[StigErik]

Here's my decay
A little messy around 15 Hz though .....

 

[Oddball]

Agreed, I'm good. Perhaps at some future point I'll add a couple nearfield subs, more for additional tactile response / envelopment than anything, but that would likely be frivolous and then there are the additional challenges that this introduces to the integration process.

I do use towers left and right and a big 3-way center. The plots above are subs-only. They keep up quite well when the volume gets pushed. I tend to get good results from Audyssey (when used with the companion app), so I've not given much thought to Dirac.

Don't think it would be frivolous to go for more, but good to set a direction of travel.

Are you using the Audyssey/D&M LFE+Main setting for your LCR or even perhaps LFE distribution? These are potentially enhancements you could get for fee.

 

[Fredygump]

Below are compression sweeps that I ran when the Monolith 15s were in use. The mic was positioned at the MLP, which is about 11ft distant from the subs.

This is a nice amount of headroom and perhaps enough for my needs. I still had to satisfy my curiosity, though. With the PSAs, I'm finding more qualitative differences than quantitative ones. What's most telling is that with the Monoliths tuned hot for loud movie watching, I'd often feel it necessary to reduce the sub signal when switching to music, as bass could become intrusive and overpowering. With the PSAs, I haven't felt the need to do that. It's almost like going from good speakers to great ones - great speakers often don't sound very loud even if they're cranking out the same amount of output as lesser speakers that do. As a result, they (and these PSAs) are less fatiguing and more enjoyable to listen to, particularly over long stretches.

You are hitting THX reference levels down to 20hz, so you have already reached the promised land.

I don't know what equalizer options you have, but I would try to get rid of the +5dB peak at 70hz. I would strive for a flat or slightly downward curve, with 20hz being the loudest.

Not long ago I watched a version of a movie where the mix was boosted from 70-100hz. It didn't sound good. (The same movie, played from different sources, had audio that was mixed differently.) I think eliminating this peak will give you a more transparent low frequencies. I'm just working this out as I type, but I believe boosting the bass frequencies has an effect similar to adding harmonic distortion to the sub frequencies.

(Every natural sound has overtones, and harmonic distortion is overtones made by the speaker that are unwanted/ not in the original sound. So a 35hz sound will have an octave at 70hz...and if the speaker is louder at 70hz than it is at 35hz, the 70hz overtone in the recording will be louder than it should be....so it is similar to if the sub driver with a flat EQ was producing 2nd order harmonic distortion (i.e. 70hz). I think I just figured this out, the why a downward sloping response curve sounds best. But if anyone out there disagrees, I'd be curious what you think.)

 

[Fredygump]

Here's my decay
A little messy around 15 Hz though .....

View attachment 364099

It's a pretty chart, but you really need to show us down to -40dB from the average SPL.

 

[mj30250]

You are hitting THX reference levels down to 20hz, so you have already reached the promised land.

I don't know what equalizer options you have, but I would try to get rid of the +5dB peak at 70hz. I would strive for a flat or slightly downward curve, with 20hz being the loudest.

Not that it matters since those subs are no longer in play, but the compression sweeps were done with the crossover disabled, hence the 70Hz bump. The normal sub response was as shown in the first post.

 

[StigErik]

It's a pretty chart, but you really need to show us down to -40dB from the average SPL.

Sure. Here's at 90 dB SPL. I think that represents the maximum SPL I get when listening to music. Most of the decay below 30 Hz will fall below 0 phon and thus be inaudible at this SPL. There's still some clutter around 60 Hz that I want to get rid of, just to make the graphs look more impressing

 

[Andysu]

i not been in the THX cinema for few days , i may do the REW sub again

 

[My adventures in stereo]

Very nice bass response
Was surprised to see that you are calibrating for around 100db SPL
THX levels are 85db , right ?
I have been adjusting my gain levels to reach around 85 db, for calibration
Also at higher SPL levels, as you noted, the ream creaks, booms etc, which is not ideal

 

[StigErik]

I find 85dB too loud at home, mostly because movies on DVD/Bluray are mastered too hot. I usually set my volume somewhere between-12 and -8 dB.

 

[Bugal1998]

Very nice bass response
Was surprised to see that you are calibrating for around 100db SPL
THX levels are 85db , right ?
I have been adjusting my gain levels to reach around 85 db, for calibration
Also at higher SPL levels, as you noted, the ream creaks, booms etc, which is not ideal

Target Reference level depends on room size. Commercial cinemas (I.E. auditorium sized rooms) target 85db with a -20db signal. Hometheater sized rooms should target 76-79db depending on their size, with the smallest rooms targeting 76 on up to 79 for larger home theaters (~5000 cubic ft.).

 

[StigErik]

Why would the reference level depend on the room size? Related to room decay, or what?

 

[SSS]

Zero if the stereo speakers are good enough.

 

[Bugal1998]

Why would the reference level depend on the room size? Related to room decay, or what?

I'm not entirely clear why, but your hypothesis is as good as any I've seen.

See pg. 36, table 10.2 in the ATSC pdf linked here:

https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.atsc.org/wp-content/uploads/2015/03/Techniques-for-establishing-and-maintaining-audio-loudness.pdf&ved=2ahUKEwiyzYGO79qFAxUJD1kFHWbfBWEQFnoECBoQAQ&usg=AOvVaw1ec2MJTNnBJQzgdYAgiTbu