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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
geoffkait's avatar
geoffkait
23,365 posts
 
Car systems are cool. Battery power and pneumatic isolation. Nothing wrong with them apples.

willemj
1,036 posts
 
I have tried to imagine what is meant by fast or slow bass. It cannot be the speakers themselves for reasons that have been explained. My hypothesis is that what people are referring to is really the delay that is visible in waterfall graphs of bass response in real rooms: the reflected sound of room modes lingers on.
When I added a B&W PV1d subwofer to my Quad 2805 electrostats I was disappointed at first, even though the room is large. The bass did indeed sound slow and woolly - not at all like the bass that was coming out of the stats. When I added an Antimode 8033 dsp room equalizer the problem was gone, and over a pretty wide area. So it was not the speaker that as slow, but the sound.
My take home lesson has been that room modes can indeed be a big problem. In a small room it is not a good idea to even try to reproduce deep bass. In a bigger room, with room modes at lower frequencies, the problem is less (the Schroeder frequency is lower), and equalization is easier and effective over a wider area. The second lesson is that dual subs are advisable, and preferably combined with a room eq system such as the Antimode 8033.
audiokinesis
2,737 posts
 

Willemj wrote: "I have tried to imagine what is meant by fast or slow bass. It cannot be the speakers themselves for reasons that have been explained. My hypothesis is that what people are referring to is really the delay that is visible in waterfall graphs of bass response in real rooms: the reflected sound of room modes lingers on."

Yes!!

What the ear interprets as "slow" is all happening on the trailing end of the notes. It is ALSO showing up as a frequency response peak, as you are about to see (and, this is the key to the in-room bass puzzle):

Speakers + room = a "minimum phase" system at low frequencies, and what this means is, the time-domain response tracks the frequency response, and vice-versa! In other words, where you see a slow-decaying ridge of energy in a waterfall plot is also where the system has a frequency response peak!

It gets even better: If we fix the one, we have SIMULTANEOUSLY fixed the other! So if we improve the decay time via bass trapping, we have simultaneously improved the in-room frequency response. And if we improve the in-room frequency response via EQ or distributed multisubs or whatever, we have simultaneously improved the decay time!

So any talk about the bass "speed" of a small woofer vs a large woofer is coming from an incorrect paradigm. The correct paradigm is, the in-room frequency response is marching in lock-step with the in-room decay times. THAT is the only "speed" that matters in the bass region, and we can fix it by fixing the frequency response!

* * * *

In these internet forum discussions it can be hard for observers to discern which posts contain accurate information. I don’t open up my trophy case very often, but given the myth-busting theme Eric envisioned for this thread, I think it may be relevant: A subwoofer system I designed using the principles I’ve posted about in this thread received a "Product of the Year" award from a major magazine (The Absolute Sound, 2015). This doesn’t definitively prove that the principles I’ve described are correct, but it does raise the possibility.   If so, then credit to my teacher, Earl Geddes. 

Duke

dealer/manufacturer

wolf_garcia
6,696 posts
 
Soundsrealaudio…I actually considered the RMAF this year since I haven't been to one of those things since around 1987 (NYC Stereophile show). Hmmm…also, although I am very kind at all times (well…sometimes I take a break from extreme kindness to punish someone for disagreeing with me), I wasn't kind to you at all 6 years ago simply because I wasn't there. Don't mistake other people for me as many have simply stolen my look and style to get free drinks or the chance to be the new James Bond.
willemj
1,036 posts
 
Duke,
Your Swarm system is indeed interesting and sounds like the theoretically correct solution, even if one with rather a lot of boxes in the room. In my case, I think I will continue to save for a second PV1d, used with the Antimode, as a domestically acceptable compromise (the big stats have already been pushing the boundaries). Did you ever compare (and measure) your Swarm used with room equalization?
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