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Help with choosing sub-woofers please

Having survived more than 30 years using full-range electrostatics @clearthinker has finally decided to get sub-woofer(s).  Previously he was put off by the well-known difficulty in setting the cross-over to allow a seamless integration.  Modern sub design and electronic aids seem to have fixed that.

@clearthinker is pretty knowledgeable and experienced in most aspects of two channel audio. He has spent some hours researching sub-woofers but he's having trouble evaluating the benefits of differing design and application approaches.  Such matters are not dealt with qualitatively or comparatively in most postings and videos.  He has yet to listen to any and will be trying contenders in his system.  But it needs to be narrowed down as he can't try them all.

His Martin Logan CLX Anniversaries are -3dB at 56dB and driven by vintage Krell 200 KRS References.  The room is 23 x 15.5 x 8.5 feet, carpeted, plaster ceiling, All walls are deadened with French style fabric covering and 25mm of wool behind.  Symmetrical, no windows.  No furnishing save equipment, two chairs and a small side table.  Subs will be spiked to concrete floor.  @clearthinker  listens to two channel stereo all genres, no theatre in this room.  Cost is not the most critical issue.

Some of the issues that need evaluating (in no particular order) are:

*  Benefit of subs using two opposing drivers to reduce vibration, rock and roll

*  Floor firing vs. side firing

*  How much does size matter?  Small is better if all things are not too unequal

*  Benefit of two subs to create stereo image.  Many say bass isn't very directional below about 50Hz.  But bass heard above that on the MLs is certainly directional

*  To what extent will the sound deadening deal with room modes?  Some say bass waves go straight through wall treatments back to the hard surface behind and bounce right out again

*  Benefit of two subs (or more?) optimally arranged to cancel room modes.  The unlamented Miller who was rude but knew a fair bit about audio used to mention six and eight.  There is freedom to locate.

*  Taking unit price into consideration, is it better to have one hi-end sub, two decent ones or multiple smaller cheaper subs to deal with room modes?

*  Do wireless feeds work well or is good old wire better?  How much does wire  choice matter in feeding subs (that may be a long way from the amp.  Incidentally the Audio Research Ref 6 is fully balanced.

*  Is the KEFKc62 too good to be true?

*  Does it make sense to keep it simple and just to use ML subs and digital set up systems with ML main speakers?  If so, is it worth spending more to get the Balanced Force series?

*  What about REL?

*  Anyone else?

 

Thanks in advance for all your posts.  I'm hoping a discussion of qualitative and comparitive issues  will help others get to the bottom of optimal sub-woofer applications.

 

128x128clearthinker

Showing 2 responses by atmasphere

atmasphere's avatar
atmasphere
11,615 posts
 

The 14 foot wave takes 12 milliseconds to pass my ear.  Is that fast or slow?  My MLs are flat at 80Hz and the bass there is pretty tight, not an unrecognisable reverberating mush.

@clearthinker 

Don't worry about the speed- that has nothing to do with it.

You don't hear reverberant bass as mush! In fact it might sound quite taut, like you are already hearing at 80Hz (that's reverberant as well)!

You'll have to ask Duke why he did it the way he did. But having played with a few subs I find that if you want them super small if they go down to 20Hz they won't be capable of much dynamic range, or they simply won't go anywhere near 20Hz!

atmasphere's avatar
atmasphere
11,615 posts
 

Many say bass isn’t very directional below about 50Hz. But bass heard above that on the MLs is certainly directional

* To what extent will the sound deadening deal with room modes? Some say bass waves go straight through wall treatments back to the hard surface behind and bounce right out again

At 80Hz the waveform is 14 feet long.

The ear cannot know the sound is there until the entire waveform has gone past it.

It cannot sort out the frequency until 2-3 more iterations. By this time the waveform has bounced off of the rear wall (unless you have an enormous room!) and is making its way back- and has probably already passed the listening chair by the time you can even tell what the bass note is.

So in most rooms anything below 80Hz is entirely reverberant. So its not directional at all at 80 Hz, let alone 50Hz.

The other takeaway: if you have a room with the wall in front being roughly parallel with the wall behind you, there will be standing waves no ifs ands or buts. This is why there can be good bass everywhere in the room but the listening position, and this cannot be treated with room treatment or room correction.

If a standing wave is cancelling bass at the listening position, you could put 10,000 watts worth of correction at that frequency and it would still cancel.

This is why multiple subs (Distributed Bass Array) works. If properly placed (asymmetrically in the room) they will break up standing waves, resulting in evenly distributed bass throughout the room.

Audiokinesis http://www.audiokinesis.com makes a subwoofer system called the Swarm that is 4 subs meant for this purpose. Unlike most subs, they are designed to sit directly against the wall, taking advantage of the room boundary effect. This allows them to be more compact and easier to place, especially if space is limited. I have Swarm subs in my system- they work a treat!

The trick is to keep their output below 80Hz so they don’t attract attention to themselves. Stupidly easy to set up too.

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