How much subwoofer output capability do you need in your system?

Mr Wolf

Well-known Member
Hi, this is a thread I've been planning on creating for a while now.

The table below lists CEA-2010 output rated subwoofers in order of their estimated ability to support user listening levels (relative to 85dB reference) in rooms of varying sizes. Unsurprisingly, the new Monoprice Monolith THX 16" 2000W ported sub tops the list.

For some it may be self-explanatory but if you would like to know how to use the table and how and why I created it then take a quick look at it and keep reading further down below where hopefully all is explained.

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What’s this thread all about?

Estimating how much subwoofer SPL output capability you need in your AV system in your room and whether or not you currently have it is fundamentally important yet many people (understandably) struggle with this. This thread is all about helping you do this.

THX and Audioholics room size ratings

A home cinema system's subwoofer output requirement is, to a greater extent, a function of listening level, room volume and the low frequency content of the movies being played. Two information sources currently exist that advise on a specific subwoofer model's suitability for particular room sizes. These are THX and Audioholics.

THX has its Select and Ultra programmes under which it tests and certifies subs as being capable of achieving cinema reference level in 2,000Ft3 and 3,000Ft3 rooms respectively. THX’s certification method isn’t published but a requirement is that frequency response must be flat to 20Hz so, to be THX certified, a sub must be able to hit 115dB peaks with minimal distortion at 20Hz. Very few manufacturers choose to participate in this programme these days so unfortunately very few THX certified subwoofers exist.

In contrast, Audioholics (“AH”) assigns room size ratings to the many subs it reviews and measures based on its estimate of their ability to hit 115dB at 31.5Hz (and 109dB at 25Hz) in rooms of different volumes. This is a significantly easier performance target to hit than THX’s as most subs have far more output capability at 31.5Hz than they do at 20Hz. AH’s rating method is simply to add 9dB to CEA-2010 [email protected] output at 31.5Hz and adjust this result by +/-6dB per halving/doubling of room volume from a 3,000Ft3 baseline due to a change in sound pressure, e.g. 1,500Ft3/6000Ft3 rooms add/subtract 6dB from the result due to doubling/halving of volume.

My maximum listening level ratings

The main limitation of the THX/AH subwoofer ratings is the fact that almost nobody listens at cinema reference level in their homes. As listening between 10dB and 20dB below reference level can require only 1% to 10% of the amplifier power, the THX/AH ratings can lead to seriously over-specifying the subwoofer output needs of some systems.

In order to address this, using THX’s tougher 20Hz frequency hurdle and AH’s CEA-2010 to in-room output adjustment method, I’ve estimated various subwoofers’ abilities to support different listening levels (relative to reference) in room sizes from 1,250Ft3 to 5,000Ft3. The maximum listening level capability is calculated simply by subtracting 115dB from the subwoofer’s estimated in-room output at 20Hz and these are the figures that are shown in the table.

Apparently, due to psycho-acoustics in smaller spaces, -10dB sounds about as loud as cinema reference level (i.e. 0dB) does in large commercial cinemas. This is why I have referred to the yellow highlighted >-10dB ratings as "home reference level".

Why I used a 20Hz low frequency hurdle and not 31.5Hz like AH

AH’s rating system is based on 31.5Hz output due to the bass content of >90% of movies being >30Hz. While this is probably correct, I chose to use THX’s more challenging 20Hz standard for the following reasons:
  • 20Hz is the frequency at which subwoofers can produce the least output in their typical 20-120Hz audible range of operation in a home cinema system. A sub’s maximum clean SPL output at 20Hz is therefore the limiting factor on maximum volume capability if a flat, undistorted, response down to 20Hz is desired on dynamic peaks.
  • A 31.5Hz hurdle is likely to be too high for movies with very low frequency content. As 20Hz is the lowest audible frequency, if a soundtrack contains 20Hz content, then distortion might be audible if a sub lacks sufficient output capability here. Also, <31.5Hz content is not just reserved for weird sci-fi movies as even naturally occurring deep bass sound effects (e.g. thunder) can be as low as 20Hz.
  • THX uses 20Hz for its certification programme so this method, in effect, provides THX style ratings that are adjusted for different room sizes and listening levels. This also provides a useful source of validation by looking at THX rated subs for which CEA-2010 output data is available.
If you feel a 20Hz output hurdle is too harsh for your system (some subs cannot even reach 20Hz) and you want to know the higher listening level capability that would have been derived under AH’s method then simply add the dB uplift from 20Hz to 31.5Hz shown in the table for a particular sub. For sealed subs with a relatively low output at 20Hz this uplift will be significant and, if your movies have no content <31.5Hz, the uplifted maximum listening level capability at 31.5Hz would be appropriate.

How to use the ratings table

First, determine the maximum listening level, relative to cinema reference, that your subwoofers need to support in your system. Provided your AVR/processor is calibrated to 0dB volume being 85dB reference level (not all are), this will be the lowest volume setting you use to generate the same maximum level of loudness at which you listen. As Blu-rays and DVDs are normally mastered higher than streaming sources, this is likely to be the volume setting that you use with these. For most people the level seems to be in the -10dB to -20dB range.

Now you know your listening level requirement, scan down the column that’s closest to your room size until you get to this number. Every sub at or above this row in the table should be capable of meeting your output needs.

Sub output typically increases by 4-5dB for every doubling of the number of subs if they are not co-located. So, for dual sub systems, increase the table’s maximum listening levels by 4dB. For four subs, increase it by 8dB.

Example: If you listen at -15dB in a 3,000Ft3 room then every subwoofer in the table above an SVS SB-1000 Pro [only -18db capable in a 3,000Ft3 room] should provide enough output. Note that dual SB-1000 Pros would be capable as they should support a -14dB listening level.

Accuracy of the ratings table

CEA-2010 output is objectively measured so the accuracy essentially depends on the reliability of AH’s adjustment method to arrive at an in-room output figure. As they’ve stuck with it for over 10 years now I suspect it's fairly reliable and it appears to be in-line with THX's own ratings which I explain further below. Be aware though that AH's 9dB boundary gain adjustment assumes corner placement to maximise in-room output so if yours is not then you may need to reduce the figures by a few dB to be conservative.

Reassuringly, the table shows Monoprice’s Monolith THX 10” and 12” subs to be 0dB and +1dB capable in 2,000Ft3 and 3,000Ft3 rooms respectively which corresponds perfectly with their respective THX Select and THX Ultra certifications. So it seems that the great minds at THX and AH might think alike.

As these two THX rated subs only just creep into their certification bands, if anything I suspect the table's ratings may understate subwoofer capability slightly. This would be particularly so in smaller rooms that might benefit from a significant amount of room gain at 20Hz which has not been factored into the calculations. In small, well sealed listening spaces room gain at 20Hz could add up to 8dB or more to a sub's output and its existence would add dynamic headroom to the figures shown.

At the end of the day, these ratings are still estimates and it would do no harm to add a few dB headroom to your listening level requirements to be conservative.

Going forward

There’s far more to subwoofer performance and sound quality than maximum output at 20Hz and these ratings. And don’t let any of this stop you from buying more powerful subs either as there's much to be gained by having a considerable amount of output headroom as it can help add a more explosive delivery quality to a system.

Hopefully though, this thread will help members make more informed choices when specifying the minimum subwoofer requirement for their systems.

I consider the ratings table a “work in progress” so would welcome any ideas on how to improve it as well as any CEA-2010 output data for subs not currently listed. Obviously, if you spot any errors or omissions then please let me know. I'm also sure this thread will stimulate a reasonable amount of debate which would be great.

If the thread proves popular, I’ll update it whenever new CEA-2010 test data is published.

Mr W.

References:
Brent Butterworth: CEA-2010 - A Better Way to Measure Subwoofers
Audioholics: Subwoofer room size rating protocol
THX: Room size certifications
 
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Dobbyisfree

Well-known Member
Thank you for all of the effort that you've put into this. I feel this will be an awesome tool for AVF and appears to be the best level of complexity to give members a great starting point in their decision marking processes.

As you've pointed out, there are many different reasons (as explained by thousands of posts and an entire thread for subwoofers at AVF!) on which subwoofer to choose and why. But, in order to quantify, using the 20Hz in your chart in addition to the adjustment factors covers a substantial percentage of "how good is a subwoofer's performance". On that basis, I wanted to make the comment about the price column. Very interesting. I think we can safely say that it doesn't show a clear correlation!
 

Dobbyisfree

Well-known Member
@AndreNewman I am sure you will be very interested in this!
 

rccarguy2

Well-known Member
My room is 7.14m X 3.66m X 2.7m so that's about 70 m
Take away a few meter cubed for furniture bookshelves etc I'd say I mostly listen at -10db
 

Mr Wolf

Well-known Member
My room is 7.14m X 3.66m X 2.7m so that's about 70 m
Take away a few meter cubed for furniture bookshelves etc I'd say I mostly listen at -10db
You’re OK as the table shows your SB-13U is -7dB capable in a 71m3 room so at -10dB you have circa 3dB of dynamic headroom.
 

AndreNewman

Active Member
Interesting, I can't find any CEA 2010-A numbers for my subs or the loan one I'm comparing.

I have a BK Monolith & a BK Monolith+ and a loaner PSA S1500, does anyone have meaningful numbers for any of those?

For duals, just add 3dB, or 6dB? Edit: 4dB I read it again, more properly.

The 31.5Hz numbers will be meaningless in my room as the length node is 31.3Hz, huge boost.
 

Jase

Distinguished Member
Interesting, I can't find any CEA 2010-A numbers for my subs or the loan one I'm comparing.

I have a BK Monolith & a BK Monolith+ and a loaner PSA S1500, does anyone have meaningful numbers for any of those?

For duals, just add 3dB, or 6dB? Edit: 4dB I read it again, more properly.

The 31.5Hz numbers will be meaningless in my room as the length node is 31.3Hz, huge boost.

Click below, scroll down the page and select the Performance tab for the S1500 figures:-


Edit. Here they are.

16Hz - 25Hz:109.7 dB
31Hz - 50Hz:122.1 dB
63Hz - 100Hz:126.6 dB
16Hz - 100Hz:121.8 dB
 

rccarguy2

Well-known Member
Room size is part of it but what about distance to the sub? I'm not 7m away
 

Jase

Distinguished Member
@Mr Wolf

The PSA S1500 figures are posted/linked above but here are the PSA S1811 figures:-


16Hz - 25Hz:113.5 dB
31Hz - 50Hz:126.6 dB
63Hz - 100Hz:128.6 dB
16Hz - 100Hz:125.2 dB
 

AndreNewman

Active Member
Click below, scroll down the page and select the Performance tab for the S1500 figures:-


Edit. Here they are.

16Hz - 25Hz:109.7 dB
31Hz - 50Hz:122.1 dB
63Hz - 100Hz:126.6 dB
16Hz - 100Hz:121.8 dB
Thanks.

So for 5.4m x 4.4m x 2.54m a single PSA S1500 should be plenty, we usually listen around -20 to -15 depending on the movie.

Trouble is I seem to need three subs minimum to deal with all the room issues, does mean I could probably buy 3 lower powered sealed subs, if I decide to go sealed.

Useful.
 

Jase

Distinguished Member
Thanks.

So for 5.4m x 4.4m x 2.54m a single PSA S1500 should be plenty, we usually listen around -20 to -15 depending on the movie.

Trouble is I seem to need three subs minimum to deal with all the room issues, does mean I could probably buy 3 lower powered sealed subs, if I decide to go sealed.

Useful.

Three S1500's (or equivalents) would be my personal choice as I tend to lean towards having plenty of headroom should I ever feel the need to push it to reference level. I generally listen at around -7db for most stuff. -15db for any discs that have been mastered on the hot side.

I have dual PSA S1811's in a room smaller than yours (approx 38m³).
 

AndreNewman

Active Member
I don't think I've felt any need to push to reference level and my wife would need earplugs, she finds -30 plenty loud enough, -15 is really pushing it for her.

I think the chart will be really useful but... It only has huge subs in there, I see some value in people with smaller subs being able to see what they need to add to get a comfortable (to them) headroom. In which case it needs some wimpy subs, and lifestyle woofers to make the point, give a reference point.

It's like those GPU benchmarks that only have GPUs less than 2 years old, how does someone with a 6 or 7 year old GPU know what improvement they will get? Edit: it means the chart is mostly useful to those who probably already know the answer.

But are there available CEA 2010-A measurements for those sort of subs?
 

Jase

Distinguished Member
I don't think I've felt any need to push to reference level and my wife would need earplugs, she finds -30 plenty loud enough, -15 is really pushing it for her.

I think the chart will be really useful but... It only has huge subs in there, I see some value in people with smaller subs being able to see what they need to add to get a comfortable (to them) headroom. In which case it needs some wimpy subs, and lifestyle woofers to make the point, give a reference point.

It's like those GPU benchmarks that only have GPUs less than 2 years old, how does someone with a 6 or 7 year old GPU know what improvement they will get? Edit: it means the chart is mostly useful to those who probably already know the answer.

But are there available CEA 2010-A measurements for those sort of subs?

For domestic bliss reference level isn't advised...:rotfl:

I don't think all manufacturers give CEA measurements even though it would be useful. Having said that, PSA seemed to have stopped publishing them as well for some reason.

If looking at multiple smaller sealed subs then SVS or Arendal would be where my money would go.
 

ashenfie

Well-known Member
Not sure I really believe the chart seams to be all over the place, like 23rd a SVS SB 16 Ultra barely able to make reference in most rooms?
 

Dobbyisfree

Well-known Member
Not sure I really believe the chart seams to be all over the place, like 23rd a SVS SB 16 Ultra barely able to make reference in most rooms?

No doubt an awesome sub.

I don't know if you've read Mr Wolf's explanation of why he has used 20Hz. In my opinion, it's very logical. He gives various reasons. But, if you have the SVS Ultra it could be incredible at 35Hz but as soon as (at the same MV) a 20Hz sound appears it distorts.

I.e. it is almost a fact that every sub on the market can achieve higher output at 30Hz than it can at 20Hz. But, as far as I'm aware, no subwoofer works the other way round.

And, bare in mind that I'm speaking from the point of view of someone who has two subs with a port tune that means at 30Hz they massively exceed their 20Hz output. I've noted the max MV I can have based on my subs 20Hz performance (which seems consistently to be -10dB if dynamic EQ is off and no adjustment to sub level post Audyssey).

[Added with edit] - you can see from the 31.5Hz column for uplift how some subs that clearly aren't tuned as much for 20Hz versus 30Hz look out of place with a really high boost figure!
 
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Mr Wolf

Well-known Member
Not sure I really believe the chart seams to be all over the place, like 23rd a SVS SB 16 Ultra barely able to make reference in most rooms?
Interesting comment. What is it that makes you think it should be classed as a reference capable sub? Also, why do you think the chart seems “all over the place” - it seems extremely logical to me.

It’s really quite simple. THX‘s reference requirement is 115dB down to 20Hz and the SB16–U only outputs 100dB at 20Hz under CEA-2010 testing at 2 metres. Uplifting this by 9dB for boundary gain in a 3,000Ft3 room still leaves it short by some margin. These maths are Audioholics’, not mine, and they appear to agree with THX‘s subwoofer certifications.

That said, in practice that sub should be enough for anyone as home cinema reference level is closer to -10dB (i.e. 105dB peaks) as I explained plus buyers of subs of this quality usually go for a pair so will have at least an extra 4dB on hand. Add in a little more for room gain and you’re probably at 115dB cinema reference in most rooms.
 

Mr Wolf

Well-known Member
@Mr Wolf

The PSA S1500 figures are posted/linked above but here are the PSA S1811 figures:-


16Hz - 25Hz:113.5 dB
31Hz - 50Hz:126.6 dB
63Hz - 100Hz:128.6 dB
16Hz - 100Hz:125.2 dB
Thanks for this Jase, it would be great to add PSA's subs to the table as they're absolute beasts and, as 20Hz is the limiting factor here, anything with an extremely large driver and lots of power to back it up is likely to rank very highly.

About the output numbers on their website, we need to know if they're RMS or peak and at what measurement distance they were taken. Also, as they're grouped (e.g. 16-25Hz) what does that actually mean? Minimum, maximum or average of the three?

To be reliable and comparable we really need [email protected] figures for 20Hz and 31.5Hz - anyone fancy asking Tom nicely for them?
 

Jase

Distinguished Member
Thanks for this Jase, it would be great to add PSA's subs to the table as they're absolute beasts and, as 20Hz is the limiting factor here, anything with an extremely large driver and lots of power to back it up is likely to rank very highly.

About the output numbers on their website, we need to know if they're RMS or peak and at what measurement distance they were taken. Also, as they're grouped (e.g. 16-25Hz) what does that actually mean? Minimum, maximum or average of the three?

To be reliable and comparable we really need [email protected] figures for 20Hz and 31.5Hz - anyone fancy asking Tom nicely for them?

I'll tag @Tom @ PSA and hopefully he'll be able to answer those questions. In the meantime I'll do some digging and see what I can find out. :thumbsup:
 

Mr Wolf

Well-known Member
Room size is part of it but what about distance to the sub? I'm not 7m away
Don't know where you get 7m from but I expected someone to raise the distance to sub(s) issue.

I'm sure there will be some exceptions but my research into this subject has led to me to conclude that, unless you're sitting extremely close to the subs, then sub to MLP distance is not a very important factor. I know that in my (single sub) living room system that the loudest bass is found at the furthest point away from the sub in the opposite corner of the room.

That said, Audioholics' 9dB boundary gain adjustment assumes a sub to MLP distance of 4 metres in a 3,000Ft3 room. And you could argue that its room volume +/-6dB per whole space adjustment takes some account of the fact that you are likely to be sitting closer to a sub in a smaller room.

I have an open mind on this and if anyone can present a scientifically valid way of incorporating it into the calculations then please let me know.
 

Mr Wolf

Well-known Member
But are there available CEA 2010-A measurements for those sort of subs?
Unfortunately not but frankly there's really no excuse for proper subwoofer manufacturers like BK not to publish these figures.

All I can suggest is that you try and find the closest CEA-2010 rated sub to a non-rated one you're considering and go from there but you need to be careful.

Logically, you might expect something like a BK Monolith to be comparable to a SVS PB-1000 - both 12", ported and with 300W-325W amps but specs can be very misleading e.g. at what impedance load is the amp's power rated at? And what is the sensitivity of the driver?

The BK uses a Class A/B amp with a commercially available driver whereas the SVS uses a Class D amp with a bespoke driver and uses DSP to help keep things under control. In practice their outputs might vary considerably.

My research has also lead to me to conclude that specs can be a very poor indicator of real world performance.

Value of subwoofer amplifier power ratings?
 

Gasp3621

Distinguished Member
About the output numbers on their website, we need to know if they're RMS or peak and at what measurement distance they were taken. Also, as they're grouped (e.g. 16-25Hz) what does that actually mean? Minimum, maximum or average of the three?

To be reliable and comparable we really need [email protected] figures for 20Hz and 31.5Hz - anyone fancy asking Tom nicely for them?
I'll tag @Tom @ PSA and hopefully he'll be able to answer those questions. In the meantime I'll do some digging and see what I can find out. :thumbsup:

You won´t get anything from Tom. He doesn´t even respond emails anymore and we have asked here from him about the performance difference between old and new, but rounded answers with attacking attitude. I don´t know what happened to him. He was different person few years ago.

Those figures posted are 1M Peak. CEA-2010 1M Peak is 9 dB higher than traditional 2M RMS.

Also those figure posted are averages of three frequencies. You can´t put them in the chart without knowing each frequency and Tom haven`t ever told them. He doesn´t even send their subs for third party to be measured, quite many are asking that to happen in US, but i wonder does he have something to hide with these new pro drivers? Luckily there is other manufacturers that aren´t afraid to do that.

Here is XS15SE measured by DataBass in 2014. This is within 1db to S1500 so @Mr Wolf could perhaps add it to that chart. S1500 is very similar performing to SB13U, see 2nd chart. Would really help if Tom would look the chart for XS15 and compare it to new S1512 and tell us how much more headroom it has roughly, but no...



820a3f40-d890-11e8-8e33-8dd117062f2a.png


imageuploadedbyavforums1440273852-268763-jpg.617963
 

Gasp3621

Distinguished Member
Interesting, I can't find any CEA 2010-A numbers for my subs or the loan one I'm comparing.

I have a BK Monolith & a BK Monolith+ and a loaner PSA S1500, does anyone have meaningful numbers for any of those?

For duals, just add 3dB, or 6dB? Edit: 4dB I read it again, more properly.

The 31.5Hz numbers will be meaningless in my room as the length node is 31.3Hz, huge boost.

BK Monolith has been measured in Hometheatershack, but the forum doesn´t show graphs anymore. Tons of data lost, horrible! It hit 99,7db at 20hz and higher up in the mid-bass region about 105db what i remember. Deep down it can compete with new similar 12" models, but higher up the new designs like PB1000 Pro are good amount ahead. Mono Plus driver is not much different spec wise to Mono 300w when we compared those, the amp power 300w -> 500w is biggest change on paper. M+ came 2010, hopefully they will update it at some point. :)
 

AndreNewman

Active Member
BK Monolith has been measured in Hometheatershack, but the forum doesn´t show graphs anymore. Tons of data lost, horrible! It hit 99,7db at 20hz and higher up in the mid-bass region about 105db what i remember. Deep down it can compete with new similar 12" models, but higher up the new designs like PB1000 Pro are good amount ahead. Mono Plus driver is not much different spec wise to Mono 300w when we compared those, the amp power 300w -> 500w is biggest change on paper. M+ came 2010, hopefully they will update it at some point. :)
Thanks, very useful.

I seem to need at least 2 or 3 subs to get a good response in this room, so no benefit in one huge sub.

I must say there doesn't seem a huge difference between the Mono & the Mono+ but there's a huge difference in the secondhand prices.

I did some sweeps alternating the two in the same locations and there's a little more low extension with the Mono+, probably mostly differences in filter design. I didn't think to do compression tests at the time but 300w to 500w isn't that much difference. The Lab12 driver in the Mono+ does make horrible noises if it bottoms out, the Mono hasn't ever made nasty noises.
 

rccarguy2

Well-known Member
Also depends on usage. Just playing music on the system set to -10db (Spotify Bluetooth to at-300)

Then I boosted subwoofer to +10db

No problem at all.
 

Gasp3621

Distinguished Member
Thanks, very useful.

I seem to need at least 2 or 3 subs to get a good response in this room, so no benefit in one huge sub.

I must say there doesn't seem a huge difference between the Mono & the Mono+ but there's a huge difference in the secondhand prices.

I did some sweeps alternating the two in the same locations and there's a little more low extension with the Mono+, probably mostly differences in filter design. I didn't think to do compression tests at the time but 300w to 500w isn't that much difference. The Lab12 driver in the Mono+ does make horrible noises if it bottoms out, the Mono hasn't ever made nasty noises.

Kenshington is selling Mono+ and John24ssj also but the finish was bit special (mahogany). Naturally best to stick with three Monos than mix S1500. @Ultrasonic bought the PSA S1500 after Mono and it was quite bit better in many ways, not sure what you think of it. However it would be very hard to find few extra S1500 as they rarely come available used, unless @Topmetom 2 decides to upgrade.
 

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