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Article Request: Subwoofer Shootout

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Article Request: Subwoofer Shootout

Postby Suntower » Sat Oct 24, 2020 7:03 am

I have been talking to several engineers I respect recently who all -swear- by using a subwoofer as the -only- credible way to get accurate bass response in typical home studios... where the room simply isn't long enough to deal with modal dips--no matter how much you treat it.

OK, fine. So... what are the options? I read your recent article on the Amphions, looked at the price and yumpin' yoyzus that ain't happenin'.

My suggestion: an article on low-priced (but decent) subs that can be added onto typical < $1,000 stereo monitors.
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Re: Article Request: Subwoofer Shootout

Postby ef37a » Sat Oct 24, 2020 8:49 am

Unless you know of a new law of physics/acoustics Suntower I cannot see how any sub woofer* is going to give you a more even bass response in a small room (define "small" please) .

The benefits of a sub are the ability to get greater LF extension and level in a system with small main speakers because cost and/or space makes them LF light. There is also the situation where a pair of very high quality monitors are used to get the all important mid-range and imaging accurately but cost again precludes getting those qualities at 40Hz with the power to endanger windows.
However, SOS pages have often told of the difficulties of integrating a sub in a monitoring situation and Hugh only recently warned of the poor quality, mainly distortion, often produced by 'budget' subs.

*The exception it would seem is a 'cardioid polar response at LF but the few examples I know about are scarily expensive and designed for high levels in biggish rooms?
What would be lovely is if someone would make a small, 2X 6" say cardioid sub of modest SPL and cost but with low distortion. Not likely commercially viable tho'but.


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Re: Article Request: Subwoofer Shootout

Postby Hugh Robjohns » Sat Oct 24, 2020 11:41 am

Suntower wrote:My suggestion: an article on low-priced (but decent) subs that can be added onto typical < $1,000 stereo monitors.

It would be a very short article! There are cheap subwoofers, and there are good subwoofers, but there aren't any cheap, good subwoofers -- at least, none I've come across so far!

And the reason is simply that making a subwoofer that has a flat frequency response over a wide range with plenty of headroom and very low distortion is very difficult, and thus inherently expensive.

It's say to make a 'boom box' that shakes the room when the cars crash, the Trex does a tango, the volcano explodes, and Jedi blow up the death star.... But building a sub that plays tuneful, balanced bass notes over a couple of octaves, without adding five octaves of harmonic distortion to smear all across the delicate midrange of your main speakers... That's tricky!

And although I'd agree that one (or more) subwoofer(s) can be used to good effect in small studios, it takes a lot of skill and patience to properly optimise the setup, and even then it won't be 'accurate' in the true sense of that word. In my experience, subs do considerably more harm than good in the hands of most people!
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Re: Article Request: Subwoofer Shootout

Postby blinddrew » Sat Oct 24, 2020 12:49 pm

Out of curiosity* Hugh, how well do apps like the Neumann one mitigate that harm?


* I have quite enough uncontrolled bass in my room and the styles of music i work with don't require crazy low end. :)
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Re: Article Request: Subwoofer Shootout

Postby ef37a » Sat Oct 24, 2020 12:54 pm

Hi Hugh, just about what I thought you might say!

Two things come to mind?
'Motional' feedback to combat distortion or perhaps a 'pre-distortion' system a la Nagra tape machines many moons ago.

Anyone working in those fields for sub woofers that you know of?

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Re: Article Request: Subwoofer Shootout

Postby Suntower » Sun Oct 25, 2020 7:30 am

Thanks for the reply. I treated my 8' x 12' deep space about a decade ago and it's 'fine' except for a massive 85hz dip that I gave up on.

I was taught that such was the fate of all such small rooms.

I've learned to live with it. I know what to do to work around it.

But I keep hearing from credible people that... no... if you have the dosh, you -can- do better... with a sub.

But apparently, that too requires a ton of money.

I'm not looking to do earthquakes. Just fill in that one dip. If it's still not within reach, that's fine.








Hugh Robjohns wrote:
Suntower wrote:My suggestion: an article on low-priced (but decent) subs that can be added onto typical < $1,000 stereo monitors.

It would be a very short article! There are cheap subwoofers, and there are good subwoofers, but there aren't any cheap, good subwoofers -- at least, none I've come across so far!

And the reason is simply that making a subwoofer that has a flat frequency response over a wide range with plenty of headroom and very low distortion is very difficult, and thus inherently expensive.

It's say to make a 'boom box' that shakes the room when the cars crash, the Trex does a tango, the volcano explodes, and Jedi blow up the death star.... But building a sub that plays tuneful, balanced bass notes over a couple of octaves, without adding five octaves of harmonic distortion to smear all across the delicate midrange of your main speakers... That's tricky!

And although I'd agree that one (or more) subwoofer(s) can be used to good effect in small studios, it takes a lot of skill and patience to properly optimise the setup, and even then it won't be 'accurate' in the true sense of that word. In my experience, subs do considerably more harm than good in the hands of most people!
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Re: Article Request: Subwoofer Shootout

Postby James Perrett » Sun Oct 25, 2020 1:28 pm

ef37a wrote:'Motional' feedback to combat distortion or perhaps a 'pre-distortion' system a la Nagra tape machines many moons ago.

Anyone working in those fields for sub woofers that you know of?

Didn't Phil Ward review something in the magazine that used a similar principle to motional feedback a few months ago?
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Re: Article Request: Subwoofer Shootout

Postby The Korff » Mon Oct 26, 2020 1:08 pm

It was a retrospective piece about the Philips RH544:

https://www.soundonsound.com/music-busi ... lips-rh544
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Re: Article Request: Subwoofer Shootout

Postby Hugh Robjohns » Mon Oct 26, 2020 1:39 pm

ef37a wrote:Two things come to mind?
'Motional' feedback to combat distortion or perhaps a 'pre-distortion' system a la Nagra tape machines many moons ago.

Anyone working in those fields for sub woofers that you know of?

Not as far as I know. Meyer built a big monitoring speaker called the X10 with motional feedback in the mid-2000s, but it was hugely expensive and the only one around at the time. I don't know of anyone using motional feedback in any current speaker designs... although the PSI Audio AVAA active bass traps use a kind of related idea working backwards!

In developing the X10, Meyer managed to get distortion from the bass driver below 3% at 130dB SPL, and below 0.5% at levels under 90dBSPL -- which is extraordinarily impressive. However, it wasn't just the motional feedback that achieved that -- it also involved designing a very precise bass driver capable of a large excursion with the voice coil remaining well within the linear portion of the magnetic field -- and to do that they required 4x the flux level of conventional drivers... which means expensive and heavy!

The feedback control system was built upon some horrendously complicated modern maths techniques which accommodates 'uncertainty' within a complex 'model' of the speaker system -- it's a line of development which is employed in keeping aerodynamically unstable (fighter) aircraft in the skies, amongst many other applications! It took Meyer over a year to design the 'model' and then optimise the implementation.

So while it could be done... it would be even more expensive than the existing 'passive' subwoofers which rely on expensive precision bass drivers.

I suspect the pre-distortion idea would be hugely complicated because of the very non-linear way in which distortion is generated in a loudspeaker driver, and possibly also because I imagine driver distortion varies between drive units -- especially where hand-doping is involved...
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Re: Article Request: Subwoofer Shootout

Postby The Red Bladder » Mon Oct 26, 2020 4:17 pm

I only use studios with subs in them and our main control room and our post room both have subs (M&K and Genelec).

A few things to remember -

More and more punters are using subs, as soundbars are becoming more popular.

BEFORE treating a room and BEFORE placing a sub, it is important that the room is measured and the optimum placing for bass trapping and the sub(s) is found. The best subs in the world are of F-all use if placed incorrectly or if there are null-points in the room.

The positioning of the sub should be done BEFORE the room is furnished and BEFORE trapping is placed. Be warned, it can take one eight-hour day to find that special spot for the sub!

Bass traps should be in the corners of a room and will be where bass hot-spots are measured. Nearly always, these will be the entire length of the ceiling/wall corners, as well as the wall/wall corners. Foam traps are not anywhere nearly as effective as limp-membrane traps.
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