How Much Subwoofer Is Enough?

[Chromatischism]

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.

I listen at -20, sometimes -25. I'll run a fun blast at -10 but I turn it down right after.

-20 should be 85 dB average
-30 should be 75 dB average

Varies by movie, of course.

The LFE channel is offset by +10.

And this assumes you calibrated your AVR such that 0 MV = 75 dB using a -30 dB test tone (how Audyssey works by default).

Source:

THX reference level explained

What is ‘THX Reference Level’? Reference level is a calibrated volume setting used for both movie production (in dubbing stages and post production houses) and reproduction (in screening rooms and theaters). The human hearing system is non-linear, especially in the bass, so having a consistent...

acousticfrontiers.com

 

[Bugal1998]

I listen at -20, sometimes -25. I'll run a fun blast at -10 but I turn it down right after.

-20 should be 85 dB average
-30 should be 75 dB average

Varies by movie, of course.

The LFE channel is offset by +10.

And this assumes you calibrated your AVR such that 0 MV = 75 dB using a -30 dB test tone (how Audyssey works by default).

Source:

THX reference level explained

What is ‘THX Reference Level’? Reference level is a calibrated volume setting used for both movie production (in dubbing stages and post production houses) and reproduction (in screening rooms and theaters). The human hearing system is non-linear, especially in the bass, so having a consistent...

acousticfrontiers.com

Not sure I followed your post, but calibrating a -30db tone to 75db, means setting your AVR volume level to 0db should result in an average movie playback level of 85db, and setting your AVR to -10db should result in an average level of 75db (assuming the movie is mixed to the relevant standards).

Edit: I interpreted both references to "-20" in your post as your AVR volume setting, but upon rereading I don't think think that was your intent.

 

[Bugal1998]

What ends up happening is that even though there isn't much content down there, what is there demands a lot of power to reproduce. If you don't do so, music and movies both end up sounding a little less impressive.

Agreed! Some people will say it's just random rumbles, etc., but rumbles or not, I miss that low frequency content when it isn't reproduced.

Edit: typo

 

[Fredygump]

I think it has to do with human hearing. Sensitivity to absolute levels of low frequencies is much lower. Interestingly, or ability to discern differences in bass levels (difference between 40, 50, 60 Hz) is high.

I don't know what your point is. Yes, this chart gets thrown around a lot, but what does it mean to you?

THX reference level is 115dB for the subwoofer(s?), and 105dB for the rest of the speakers. This number represents dynamic peaks, not dBa (average). These numbers are enough to achieve the intended audio listening experience, and they reflect the amount of dynamic range the audio has. So if you calibrate your system for a flat response, and your components meet reference level, you will experience the movie as it was intended. The sound track was mastered on a reference system that is calibrated for a flat frequency response, so it is recommended that you set up your system the same way.

So I don't know what this chart means to you. In my mind, it might matter if you were an engineer developing the THX standard, or an audio engineer creating the sound track?

 

[Chromatischism]

I don't know what your point is. Yes, this chart gets thrown around a lot, but what does it mean to you?

THX reference level is 115dB for the subwoofer(s?), and 105dB for the rest of the speakers. This number represents dynamic peaks, not dBa (average). These numbers are enough to achieve the intended audio listening experience, and they reflect the amount of dynamic range the audio has. So if you calibrate your system for a flat response, and your components meet reference level, you will experience the movie as it was intended. The sound track was mastered on a reference system that is calibrated for a flat frequency response, so it is recommended that you set up your system the same way.

So I don't know what this chart means to you. In my mind, it might matter if you were an engineer developing the THX standard, or an audio engineer creating the sound track?

Yes, I knew this would come up. Click my post again as I edited it to add more detail. Jack Sparrow must be rubbing off on me. Side note, we've been watching Pirates for the first time in several years. Playing these pre-immersive movies in Uncompressed PCM then upmixing with Neural:X gives the biggest, most dramatic sound here, appropriate for these movies.

 

[mj30250]

However, I don't experience quite what you describe. I've been in stupidly loud cars and know the kind of bass you're talking about. The kind that rattles your ribcage. But, that could be because I'm running a different overall curve. If I listen to music with what you describe, it doesn't sound balanced. But this does. Subs only in a small room:

View attachment 367578
The integration with the main speakers is seamless.

I have also found that a flat bass response can often result in boominess / too much obvious sub involvement with music. With the new PSA subs, I've left them flat up to the crossover region and am enjoying the sound without feeling the need to attenuate the bass. I don't have an explanation for why they are performing differently than prior subs in this area, but it's nice to not feel compelled to flip between "music" and "HT" presets.

My favorite test is the Blade Runner 2049 opening scene up to the point where he lands the police car at the farm. The whole room gets involved.

At high volumes, this sequence is legitimately uncomfortable in my room. The sensation of pressure building is wild and everything in the house that isn't completely secured is rattling/shaking/clanking/flexing like crazy. I haven't been able to get through it at my normal spirited volume levels. Perhaps I'm not as much of a basshead as I thought. Or maybe I'm just getting old.

 

[Purité Audio]

Have you tried measuring with REW and implementing the suggested filters?
Keith

 

[mj30250]

Have you tried measuring with REW and implementing the suggested filters?
Keith

Measuring, yes. So far I'm pleased with the results after using Audyssey XT32 and haven't played with any additional filters. FR, subs only:

 

[HalSF]

I’d love to learn about the history of the two-subwoofers prescription in home audio. It’s absolutely triumphed as the default recommendation and dominant configuration discussion topic in subwoofer discourse. When did it emerge as an accepted and preferred thing? Is there a decisive objective case for the sonic superiority of doubling up, and an objective case for the inferiority of a single subwoofer in music systems?

I’m *never* going to add a second subwoofer in my 11’ x 17’ listening room, to disclose my bias.

 

[Chromatischism]

I’m *never* going to add a second subwoofer in my 11’ x 17’ listening room, to disclose my bias.

You don't know what you're missing

 

[Audio Science Pal]

So far I'm pleased with the results...

Nice system you have there!

 

[HalSF]

You don't know what you're missing

That’s what I’m talking about! This evangelizing fervor.

I already know this proselytizing exists, it’s the history of this belief and the objective merits of its alleged advantages that I’m trying to understand. And why the contribution of my single SVS subwoofer, which already sounds great to me, is inadequate and begging for enhancement.

 

[NTK]

I’d love to learn about the history of the two-subwoofers prescription in home audio. It’s absolutely triumphed as the default recommendation and dominant configuration discussion topic in subwoofer discourse. When did it emerge as an accepted and preferred thing? Is there a decisive objective case for the sonic superiority of doubling up, and an objective case for the inferiority of a single subwoofer in music systems?

I’m *never* going to add a second subwoofer in my 11’ x 17’ listening room, to disclose my bias.

This is where it got started.

https://www.harman.com/documents/multsubs_0.pdf

 

[Oddball]

That’s what I’m talking about! This evangelizing fervor.

I already know this proselytizing exists, it’s the history of this belief and the objective merits of its alleged advantages that I’m trying to understand. And why the contribution of my single SVS subwoofer, which already sounds great to me, is inadequate and begging for enhancement.

Your room is not to large, and looks like you are happy - which is great. I did have smaller rooms in the past where by pure luck of favourable positioning and some light EQ, one big sub was actually enough for SPL and frequency response. But I added another one just because the pressure from that one was leading to unwanted spatial clues. For people that don't push the bass too far out this might not apply.

In the big rooms, you simply need more subs to create the pressure levels, and especially in irregular ones to even out the frequency response. Not to mention that headroom is a good thing to have and lowers distortion levels that are pretty high in last 2 octaves even with the best of subs. I don't think that anyone is necessarily pushing multiple subs, but in ideal circumstances where money is no object, multiple subs will help in pretty much every system.

 

[HalSF]

This is where it got started.

https://www.harman.com/documents/multsubs_0.pdf

Thanks! Will read.

 

[HalSF]

Your room is not to large, and looks like you are happy - which is great. I did have smaller rooms in the past where by pure luck of favourable positioning and some light EQ, one big sub was actually enough for SPL and frequency response. But I added another one just because the pressure from that one was leading to unwanted spatial clues. For people that don't push the bass too far out this might not apply.

In the big rooms, you simply need more subs to create the pressure levels, and especially in irregular ones to even out the frequency response. Not to mention that headroom is a good thing to have and lowers distortion levels that are pretty high in last 2 octaves even with the best of subs. I don't think that anyone is necessarily pushing multiple subs, but in ideal circumstances where money is no object, multiple subs will help in pretty much every system.

That’s helpful. I don’t *think* I’m getting any unwanted spatial cues from the subwoofer but I’ll keep an ear on that….

 

[Chromatischism]

There is no need to evangelize something that is factually in line with physics . It's just extremely unlikely that someone gets a bass response like this with only 1 sub.

 

[Great Sun Jester]

I’ll keep an ear on that….

A microphone and REW will get you 90% of the way there.

 

[mj30250]

There is no frequency range more dependent on the environment than bass. Rooms can readily enhance or corrupt bass fidelity and output, often both at once, and sometimes dramatically. Not only does the geometry and size of a room matter, but even the type of floor (floating or slab) can significantly alter the perception of how bass sounds and feels from a tactile sense. There is often no better way to address these variables than by utilizing multiple bass sources, properly positioned and equalized. In doing so you also gain the benefits of reduced localization as well as increased headroom.

As has already been mentioned, if your bass output desires are rather modest, your room is small, and you're fortunate to be able to position a single sub for a smooth response, yes, it's possible to get "lucky" and reach contentment without loading up your room with multiple boxes. For me, doubling up on subs has always resulted in a more enjoyable experience.

 

[nathan]

I’d love to learn about the history of the two-subwoofers prescription in home audio. It’s absolutely triumphed as the default recommendation and dominant configuration discussion topic in subwoofer discourse. When did it emerge as an accepted and preferred thing? Is there a decisive objective case for the sonic superiority of doubling up, and an objective case for the inferiority of a single subwoofer in music systems?

I’m *never* going to add a second subwoofer in my 11’ x 17’ listening room, to disclose my bias.

Todd Welti published the research about 20 years ago. Using multiple subwoofers can reduce (sometimes eliminate) room modes in the subwoofer range.

But MOST importantly multiple subwoofers can create consistent seat to seat subwoofer response, which means you can EQ for one seat and solve response in the other seats, at the same time with the same EQ choices -- something that is impossible in domestic rooms with a single subwoofer.

(Note that I didn’t mention anything about increased output. Welti did measure that as well but multiple subs is typically an inefficient way to increase output.)

E-library page - AES

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Low-Frequency Optimization Using Multiple Subwoofers​

At low frequencies the listening environment has a significant impact on the sound quality of an audio system. Standing waves within the room cause large frequency-response variations at the listening locations. Furthermore, the frequency response changes significantly from one listening location to another; therefore the system cannot be equalized effectively. However, through the use of multiple subwoofers the seat-to-seat variation in the frequency response can be reduced significantly, allowing subsequent equalization to be more effective. Three methods to reduce seat-to-seat variation are described, including a novel approach based on simple signal processing. The desired result in each case is to allow the system to be equalized over a seating area rather than just one seat. Results are shown for several listening rooms.

Author (s): Welti, Todd; Devantier, Allan
Affiliation: Harman International Industries, Inc., Northridge, CA, USA (See document for exact affiliation information.)
Publication Date: 2006-05-06 Import into BibTeX
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E-library page - AES

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