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Why is good, deep bass so difficult? - Myths and their Busters

This is a theme that goes round and round and round on Audiogon. While looking for good sources, I found a consultancy (Acoustic Frontiers) offering a book and links:

http://www.acousticfrontiers.com/guide-to-bass-optimization/?utm_source=CTA

Interestingly: AF is in Fairfax, CA, home to Fritz Speakers. I really have to go visit Fairfax!

And a link to two great articles over at sound and vision:

https://www.soundandvision.com/content/schroeder-frequency-show-and-tell-part-1
https://www.soundandvision.com/content/schroeder-frequency-show-and-tell-part-2

Every audiophile who is dissatisfied with the bass in their room should read these free resources.

Let me state unequivocally, deep bass is difficult for the average consumer. Most audiophiles are better off with bass limited speakers, or satellite/subwoofer systems. The former limits the danger you can get into. The latter has the most chance of success IF PROPERLY IMPLEMENTED.

The idea that large drivers/subs are slow is a complete and utter myth. Same for bass reflex. The issue is not the speed of the drivers. The issue is usually that the deeper a speaker goes the more it excites room modes, which the audiophile is then loathe to address.

Anyway, please read away. I look forward to reading comments.
erik_squires
randy-11
1,913 posts
 
see also Fig. 11-21 in Handbook of Acoustics...
kosst_amojan
2,095 posts
 
@shadorne 
I think you have a feeble grasp on the physics of the problem. One note? Hump? JM Labs? How long has it been since they were called that? I've looked at a bunch of cumulative response plots for a variety of speakers and there's very rarely this hump you speak of unless the speaker is just very poorly designed. The hump in the port response is the minimum motion point of the driver which means it's radiating very little sound. All you have to do is look up the measurements for speakers in Stereophile to see this mythical hump you speak of doesn't exist. 
dlcockrum's avatar
dlcockrum
2,105 posts
 
http://www.eminent-tech.com/main.html

Click on TRW-17 pic. Looks like a fan. Then "output comparison".

Dave


shadorne's avatar
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shadorne
7,333 posts
 
@kost_amojan. 
 
Well it should be easy for you to show me a link to a Stereophile or other measurement plot of a JM Labs high end speaker that does not have a bass boost, bass bump or hump?

You should be looking for a flat response that gently rolls off in the bass with no increase in response below 120 Hz at all. I feel sure you can find this as you are extremely confident.
erik_squires OP
5,268 posts
 
I have seen a couple of takes on the fan as a woofer idea.

Just FYI, as Dr. Leach was fond of saying, 0 Hz isn’t a sound, it is wind.

Another was kind of a corkscrew in a tube. Seems to be long disontinued, the Phoenix Gold Cyclone by BNIB.

Another way to use a rotating motor is converting the rotation to linear travel with a flapper, like the Devialet.

Neither method really resolves room mode issues and trades motor strength for effective surface area. As a signal drops an octave, displacement must increase by a factor of 10 for any given driver, so 1mm at 40 Hz becomes 10mm at 20 Hz, and so on.

Fans, assuming they can spin fast enough, eliminate the excursion issue. No idea about distortion figures. I can say that with a Hsu VTF 15 I can get monstrous output in room at 16 Hz, so not really a problem I need to solve.
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