How low do does a subwoofer really need to go?

[BMXTRIX]

While there are lots of 'bass' lovers out there, I like to point out that my 'Oh damn!' moment came when watching Hitchhikers Guide to the Galaxy and they walked onto the bridge and there was a sub 20Hz piece of audio that played back. My entire room shook, but I couldn't hear a darn thing. I played it back just to be sure it was what I thought it was, and made my wife pay attention. Sure enough, the pictures on the walls rattled and the whole room shook, neither of us (in our twenties) could hear a thing.

Bass, especially good bass, is not about volume, it is about presence, and only a good subwoofer can deliver on that. Smaller speakers can be noisy, they may sound decent, but they just can't deliver the way a serious subwoofer is capable of delivering. To this day, I still swear by the crazy pricey sealed Velodyne subs. Yes, a 18" sub may sound like overkill, but really, I just want a few more if you don't mind.

 

[Verdinut]

While there are lots of 'bass' lovers out there, I like to point out that my 'Oh damn!' moment came when watching Hitchhikers Guide to the Galaxy and they walked onto the bridge and there was a sub 20Hz piece of audio that played back. My entire room shook, but I couldn't hear a darn thing. I played it back just to be sure it was what I thought it was, and made my wife pay attention. Sure enough, the pictures on the walls rattled and the whole room shook, neither of us (in our twenties) could hear a thing.

Bass, especially good bass, is not about volume, it is about presence, and only a good subwoofer can deliver on that. Smaller speakers can be noisy, they may sound decent, but they just can't deliver the way a serious subwoofer is capable of delivering. To this day, I still swear by the crazy pricey sealed Velodyne subs. Yes, a 18" sub may sound like overkill, but really, I just want a few more if you don't mind.

Smaller speakers cannot reproduce those low frequencies, and what you hear are distorted harmonics of the fundamental vibration.

 

[mattlach]

My opinion is if you have a good sub, the value of buying a tower over bookshelf speakers becomes dubious.
Certainly given a normal HT with sub(s) if you only had $1000 to spend on your R&L you would be far better off to buy a pair of Ultra Bookshelf speakers than the Prime towers (Both are $1000/pr).
Many people like the looks of towers, and I get that. Towers are also typically a little more stable, so if you have rambunctious kids or dogs they may be a better choice. The Ultra Towers are $2000/pr. and most of that money is going into getting a FR down to 28Hz (-3dB); however, once you add dual (or more) subs and tune the system, you will probably end up with your crossover around 80Hz which the Ultra Bookshelf will do without a sweat!

Mostly agreed, but thing is, quality speaker stands are so expensive that you might as well spring for the towers, as they cost about the same as bookshelves + stands

 

[lovinthehd]

Mostly agreed, but thing is, quality speaker stands are so expensive that you might as well spring for the towers, as they cost about the same as bookshelves + stands

Can build your own fairly inexpensively....and the Ultras by most reports are better than the Primes so there's that, too.

 

[snakeeyes]

Then the opposite justification is a pair of ultra towers reaching 28hz at full range might let you get away with a single 20hz capable LFE sub rather than duals. Depends on which pill you swallow...

 

[yepimonfire]

Then the opposite justification is a pair of ultra towers reaching 28hz at full range might let you get away with a single 20hz capable LFE sub rather than duals. Depends on which pill you swallow...

Not really, especially when you are talking home theater. The subwoofer needs to have 10dB greater dynamic range capability than the speakers, or 115dB at reference level. With the mains running full range, they'd need to be capable of 105dB down to about 35hz, most towers would easily exceed xmax at that level.

This also ignored the fact that bass quality will vary considerably from speaker to speaker, whereas offloading it to a properly placed sub can solve that issue.

The only way I'd ever consider a speaker truly full range for home theater is if I were using pro cinema speakers with 12-15" bass drivers.

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[snakeeyes]

Not really, especially when you are talking home theater. The subwoofer needs to have 10dB greater dynamic range capability than the speakers, or 115dB at reference level. With the mains running full range, they'd need to be capable of 105dB down to about 35hz, most towers would easily exceed xmax at that level.

This also ignored the fact that bass quality will vary considerably from speaker to speaker, whereas offloading it to a properly placed sub can solve that issue.

The only way I'd ever consider a speaker truly full range for home theater is if I were using pro cinema speakers with 12-15" bass drivers.

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Agreed, but towers just have that cool factor. Hard to buy towers if you are going to just neuter them at 80hz.

 

[sterling shoote]

My JBL Charge 3 gives me the impression of bass at close range. There's not enough energy from it however to disturb neighbors. So, if ya want an impression of bass in a condo or apartment, just consider a small unit which does not have the sort of energy to shake up anything.

 

[yepimonfire]

Agreed, but towers just have that cool factor. Hard to buy towers if you are going to just neuter them at 80hz.

There are other benefits to towers such as a three way design or greater sensitivity/dynamic range, which becomes important as room size or spl requirements go up, even with an 80hz xover.

A bookshelf speaker with a single 5.25" driver crossed at 80hz will still struggle to reproduce 80hz at reference levels and would require a theoretical xmax of 10mm, which almost no midbass woofer has. That's ignoring the fact you'd also be some distance from the speaker causing an spl drop. Add a couple of 8" drivers in a tower and now you're down to 2mm of xmax at 80hz 105dB. Add a midrange and cross the tweeter higher at 4khz instead of 2khz and now you've increased the headroom of the tweeter because it no longer has to cover the upper mids. Etc etc.



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[snakeeyes]

There are other benefits to towers such as a three way design or greater sensitivity/dynamic range, which becomes important as room size or spl requirements go up, even with an 80hz xover.

A bookshelf speaker with a single 5.25" driver crossed at 80hz will still struggle to reproduce 80hz at reference levels and would require a theoretical xmax of 10mm, which almost no midbass woofer has. That's ignoring the fact you'd also be some distance from the speaker causing an spl drop. Add a couple of 8" drivers in a tower and now you're down to 2mm of xmax at 80hz 105dB. Add a midrange and cross the tweeter higher at 4khz instead of 2khz and now you've increased the headroom of the tweeter because it no longer has to cover the upper mids. Etc etc.



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Ok, what are your thoughts on the center channel and using a bookshelf speaker? Or do you solve any lobing effect with a concentric driver like Kef uses?

 

[mattlach]

Ok, what are your thoughts on the center channel and using a bookshelf speaker? Or do you solve any lobing effect with a concentric driver like Kef uses?

I probably wouldn't use a bookshelf speaker for a center, if for no other reason than that it would be difficult to fit everything right. I think yepimonfires thoughts regarding the benefit of towers at the 80hz crossover point is accurate but probably not very noticeable, as while we call them mains, in HT use the right and left channels are mostly satellites. Most real bass goes over the LFE (sub channel, the .1) anyway. The Satellites rarely get signals down at 80hz, unless they are set to "large" and run in a configuration without a sub, so the LFE is played over them.

The center is the most important of your channels in a HT setup, as it seems the most and most complex audio for film watching.

I'd definitely get a quality speaker designed to be a center.

Some people worry about getting different speakers for their center and their mains. They want to make sure they match the "timbre" of these channels. If this is something that worries you, you can always get three centers, and use two of them, standing on end for the left and right channels.

Some speaker companies even sell their center channel speakers as "LCR's" for this very reason.

 

[William Lemmerhirt]

Agreed, but towers just have that cool factor. Hard to buy towers if you are going to just neuter them at 80hz.

I agree that towers look much better than BS on stands. They’re just more elegant(usually.) And although I do normally agree with your thoughts, I have to basically reiterate what yep said. I don’t find it hard to justify towers at all.(just have to budget longer) I have 3 way towers with 12” woofs as mains that are good to the mid 30’s. They’re 14’ away. Even crossed(neutered if you will) at 80, they deliver larger more realistic sounds, in an effortless manner. Especially as the volume goes up. As mentioned, the center carries the burden of majority, but there is a LOT of stuff off screen that carries a lot of weight, and powerful midrange that and IMO, BS speakers, especially those with single/small drivers can’t punch like those with larger/more/more sensitive drivers can. Now quiet movie watching in an apartment(would suck) wouldn’t require/allow the same thing and bang for the buck would give the edge to the BS.

 

[snakeeyes]

Thanks William! Dual subs and towers and a true center.... . The older Kef Reference series might be an option I’ll look into. I see they are discounted a bit.

 

[sterling shoote]

Too, many words have been written here to describe the impact of a sub for music listening pleasure for what can be understood simply by listening to Stevie Ray Vaughan's Tin Pan Alley (AKA Roughest Place In Town).

 

[William Lemmerhirt]

Thanks William! Dual subs and towers and a true center.... . The older Kef Reference series might be an option I’ll look into. I see they are discounted a bit.

If I could do 3 towers across the front...yep. I would. I’ve been looking at the kef R and Q series on A4L. Meee likey!!!!!

 

[Verdinut]

Not really, especially when you are talking home theater. The subwoofer needs to have 10dB greater dynamic range capability than the speakers, or 115dB at reference level. With the mains running full range, they'd need to be capable of 105dB down to about 35hz, most towers would easily exceed xmax at that level.

This also ignored the fact that bass quality will vary considerably from speaker to speaker, whereas offloading it to a properly placed sub can solve that issue.

The only way I'd ever consider a speaker truly full range for home theater is if I were using pro cinema speakers with 12-15" bass drivers.

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If you were to use pro cinema speakers even with 18" subwoofers, I strongly think that you would be disappointed with the results:

Published Response: JBL 5628 ( 2 X 18") : - 3dB @ 24 Hz and -10dB @ 18Hz

Danley TH50 (1 X 15") : - 3dB @ 21 Hz and - 10dB @ 18Hz

QSC SB-7118 (1 X 18"): -6dB @ 22Hz and - 10dB @ 19Hz

Now imagine how much power you would need to get one of those to a flat response at 18Hz. Those pro subwoofers are very sensitive and that sensitivity is at the expense of low frequency efficiency. No professional subwoofer on the market can provide the low frequency performance of a good home subwoofer.

Altec Lansing and JBL speakers were used in theaters worldwide. They used 15" woofers and their low frequency response was limited to about 40Hz @ -6dB or more. I know them very well as I had up to recently 3 Altec A7 Voice of the Theater components in my three front speaker cabinets. I replaced everything and installed Dayton RSS Series 15" subs in the same enclosures to replace the Altec 416-8A woofers.

My HT: https://forums.audioholics.com/forums/threads/my-7-channel-system.111234/

 

[yepimonfire]

Ok, what are your thoughts on the center channel and using a bookshelf speaker? Or do you solve any lobing effect with a concentric driver like Kef uses?

Obviously the best center channel is matching LCRs, most of the time though, unless you've got seats greater than 30 degrees of axis an mtm isn't that big of an issue.

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[yepimonfire]

If you were to use pro cinema speakers even with 18" subwoofers, I strongly think that you would be disappointed with the results:

Published Response: JBL 5628 ( 2 X 18") : - 3dB @ 24 Hz and -10dB @ 18Hz

Danley TH50 (1 X 15") : - 3dB @ 21 Hz and - 10dB @ 18Hz

QSC SB-7118 (1 X 18"): -6dB @ 22Hz and - 10dB @ 19Hz

Now imagine how much power you would need to get one of those to a flat response at 18Hz. Those pro subwoofers are very sensitive and that sensitivity is at the expense of low frequency efficiency. No professional subwoofer on the market can provide the low frequency performance of a good home subwoofer.

Altec Lansing and JBL speakers were used in theaters worldwide. They used 15" woofers and their low frequency response was limited to about 40Hz @ -6dB or more. I know them very well as I had up to recently 3 Altec A7 Voice of the Theater components in my three front speaker cabinets. I replaced everything and installed Dayton RSS Series 15" subs in the same enclosures to replace the Altec 416-8A woofers.

My HT: https://forums.audioholics.com/forums/threads/my-7-channel-system.111234/

The amount of extra headroom available in those subs would allow one to EQ it lower. Most pro cinema screen speakers are full range to about 40hz.

I'm not arguing that pro cinema subs are better for HT, they aren't especially if sub 20hz output is desired, I'm arguing very few consumer speakers are capable of handling full range bass in movies without a sub.

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[Verdinut]

If someone uses pro audio woofers or subwoofers in his HT, he needs to actively biamp each box since pro drivers are more sensitive than audiophile speakers. It's not practical to put resistors in series with a more efficient woofer.

 

[panteragstk]

After using 3 LCR towers behind my screen I'll never go back to a horizontal center under my display (unless it's outside the theater). I haven't heard a center that can sound like a tower with a tweeter at ear level behind a screen.

When it comes to subs my two 12" subs (soon to be 4) sound fantastic. I've got a measurement mic now and am very curious to see how the theater measures. It sounds great to me, but I know that at the MLP for me there is a room mode at 40hz. Mostly not all that noticeable, but the low hum in Pink Floyd's "Welcome to the Machine" must be around that frequency because it is pretty much gone at MLP, but can easily be heard in other parts of the theater.

So, while I agree that having a good sub is important, placement and combating room modes is just as important. You can have the best sub on the market and put it in a bad room or in the wrong place and it won't be working to it's full potential.