Monopole vs Dipole bass in small room - The battle continues - Wavelets to the rescue - diyAudio
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Old 23rd May 2011, 04:59 PM   #1
Elias is offline Elias  Finland
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Default Monopole vs Dipole bass in small room - The battle continues - Wavelets to the rescue

Hello !

The comparison analysis between dipole and monopole bass loudspeakers in a small listening room continues !

I give emphasis on temporal fidelity of the reproduced signal. Real music signal contains time domain energy variations that must be reproduced accourately before high fidelity is achieved. This is also true for bass.

Temporal variations are best seen in the time varying envelope. I created modulated wavelet for this purpose. (Inspired by Linkwitz Dipole vs Monopole woofer)

Click the image to open in full size.

In the time-frequency domain it looks like this for ideal impulse response (20Hz-100Hz, 40dB scale):
Click the image to open in full size.


Then I measured monopole and dipole bass loudspeakers in a small room at the listening position. Here are the results.

Monopole (normalised, 40dB scale):
Click the image to open in full size.


Dipole (normalised, 40dB scale):
Click the image to open in full size.


Ideal impulse response (10dB scale):
Click the image to open in full size.


Monopole (normalised, 10dB scale):
Click the image to open in full size.


Dipole (normalised, 10dB scale):
Click the image to open in full size.


It appears that in a small room a dipole is superior over a monopole in it's ability to reproduce temporal finesse at bass frequencies.

Full report:
http://dl.dropbox.com/u/2400456/html...onen/main.html


- Elias
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Old 23rd May 2011, 06:45 PM   #2
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When you say "monopole" are you factoring in

- enclosure (was it sealed? transmission line? vented? horn?)
- cabinet bracing (what kind of bracing, cabinet construction etc)
- driver damping (what is the QTC of the speaker?)
- multiple (2 simultaneous) monopoles (as is recommended by toole et al)

You're calling it a monopole, but you haven't really described it. Surely I could take a driver poorly suited to OB, shove it in a bad location,g and get poor impulse results in the same way.

Not arguing with your results, but they just seem to be pushing an agenda without clarification of variables.
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Old 23rd May 2011, 06:56 PM   #3
SL08 is offline SL08  United States
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Very nice work.

You should present this at an AES Convention and write an AES paper about constant Q periodic wavelets.

Your data displays and measurements could also illustrate the Modulation Transfer Function of multiple monopole woofers in an acoustically small room. A wider understanding of what contributes to accurate bass reproduction is badly needed.

SL
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Old 23rd May 2011, 09:27 PM   #4
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Wonderful analysis Elias.

Did you try other frequencies as well and were they consistent?
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Old 23rd May 2011, 09:56 PM   #5
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Hello Elias,

very interesting results, thank you for posting.

Cheers
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Last edited by LineArray; 23rd May 2011 at 10:22 PM.
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Old 23rd May 2011, 10:24 PM   #6
Rudolf is offline Rudolf  Germany
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Elias,

I see results that look detailed and convincing - as usually . But I don't yet understand the reasons behind. Differences really start just below 40 Hz. What significance has that frequency for the room (or the speakers)? And I am wondering if rotating the dipole 90 would have led to another diagram. Did you have a chance to test that too?

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Old 23rd May 2011, 10:35 PM   #7
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My question would be "do these have any perceptual relevance?"

I'd be interested in others thoughts on this preferably with some pertinent data.

Dan
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Old 23rd May 2011, 10:46 PM   #8
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Oh noes! I see no images!
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Old 23rd May 2011, 11:06 PM   #9
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Quote:
Originally Posted by dantheman View Post
My question would be "do these have any perceptual relevance?"

...
Dan
I can see you are providing some information in your blog ...

audio blog: Hearing Beyond Haas

Human hearing has poor time resolution for artificial modes etc. ...

So do you think, time resolution below 100Hz is irrelevant ?

What about masking effects possibly caused by LF "burst smearing",
which could be detrimental for the perception of detail from upper
bass to lower midrange ?

Cheers
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Old 23rd May 2011, 11:44 PM   #10
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Good job Elias (and damned good tools !) , but the subject is so wide that this is only the top of the iceberg.

The measured differences of dipole vs monopole would be more explicit when using the same drivers, because here we dunno what part of this difference can be imputed to the dipole radiation pattern or to the dynamic characteristics of each driver, the dampening from the sealed load and so and on...

A very subjective POV : I was happy with my dipoles subs, but now I use an Infinite Baffle line array.
This very primitive load is absolutely a great option to consider for those who have enough space.
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