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Old 17th February 2010, 09:41 AM   #21
graaf is offline graaf  Poland
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Simple and straight question -
from the perspective of "a nonlinear spring" problem is 30 cm^3 of volume displacement too much for a 10 dm^3 box volume?
Would it create any audible distortions?
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Old 17th February 2010, 11:20 AM   #22
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Some unsorted ideas from my own experience:

Every damping material is different. I had good
experience e.g. with long fiber sheep wool.

Some foam materials used for lining the cabinet
walls sound "strange" to me when the cabinet is
filled extensively.

I had good experience in bringing a portion of
the material near the driver (as near to the cone as possible).
There is often a "cleaning" effect up to the midrange of the
driver. A lightweight underdamped cone will participate
from that more than a highly damped cone.

Fixing the material where you want it to be
is advantageous (using cords or nets e.g.)

Sound from inside a box radiated through the
cone is a problem. Unwanted midrange sound
from inside the Box radiated through a BR Port
of a 2 way system might be even a bigger Problem.
Could result IMO in the only real advantage of a
passive radiator: If constructed properly, there is
less unwanted sound going from inside to outside.

Also Compound ("isobaric") Systems may have
better isolation from inside to outside.

This is independent from the reqirement that
cabinet walls should be of low Q and high mass.

I prefer ommitting cabinets ...
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Old 17th February 2010, 11:37 AM   #23
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Quote:
Originally Posted by graaf View Post
Simple and straight question -
from the perspective of "a nonlinear spring" problem is 30 cm^3 of volume displacement too much for a 10 dm^3 box volume?
Would it create any audible distortions?
I have an Excel spread sheet that will let you play around with this. Just run it with the suspension nonlinearity turned off (suspension is just a simple model). For the most part the nonlinearity of the air spring is not a big deal unless the enclosure is small and swept volume is large. Distortion is HD.
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Old 17th February 2010, 11:59 AM   #24
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If i were to choose between two versions of a BR Box
both having about the same alignment but

A) having a lower Q driver with undamped
cabinet and

B) having a higher Q Driver but damped cabinet
i would prefer B without worrying.

Even if the box under Question is a subwoofer.
Even if the price to pay is a lower efficiency.

This is because i expect B) to play cleaner at
least from upper bass to midrange and to have
less audible box resonances.

One can build a cabinet wedge shaped, pyramid shaped
whatever you like, there will be some improvement
over a rectangular box, but it will remain "hollow"
sounding if undamped.

Sorry if this is a little off topic, because focus is on
nonlinearity introduced by damping material.

But there is always the question what you pay
and what you get.

Kind Regards
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Last edited by LineArray; 17th February 2010 at 12:01 PM.
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Old 17th February 2010, 12:18 PM   #25
graaf is offline graaf  Poland
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Quote:
Originally Posted by john k... View Post
I have an Excel spread sheet that will let you play around with this. Just run it with the suspension nonlinearity turned off (suspension is just a simple model). For the most part the nonlinearity of the air spring is not a big deal unless the enclosure is small and swept volume is large. Distortion is HD.
thank You very much!
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Old 17th February 2010, 08:30 PM   #26
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Usually, when somebody says "stuffing/damping the inside of a box kills resonances but also live and energy in the music" ask him if he did tweak/tune the x-over at the same time...If not, he doesn't know about this matter; if yes, I guess he added to much stuffing and/or isn't able to fine tune a speaker.
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Old 17th February 2010, 08:47 PM   #27
ScottG is offline ScottG  United States
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Quote:
Originally Posted by crazyhub View Post
Usually, when somebody says "stuffing/damping the inside of a box kills resonances but also live and energy in the music" ask him if he did tweak/tune the x-over at the same time...If not, he doesn't know about this matter; if yes, I guess he added to much stuffing and/or isn't able to fine tune a speaker.
This is because most aren't modifying the chamber of the tweeter.

i.e. extend the response of the tweeter lower in freq., (either by lowering the freq. for the highpass or making the crossover a lower order), and "all of a sudden" some of the "life" returns. (..assuming we are adding stuffing to the mid/bass driver.)
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Old 17th February 2010, 09:09 PM   #28
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Quote:
Originally Posted by ScottG View Post
This is because most aren't modifying the chamber of the tweeter.

i.e. extend the response of the tweeter lower in freq., (either by lowering the freq. for the highpass or making the crossover a lower order), and "all of a sudden" some of the "life" returns. (..assuming we are adding stuffing to the mid/bass driver.)
yes, or generally simply re-balancing the global response (usually because stuffing eat more bass than mids_unlinearity of the dampening_return to the thread subject, funny, lol)
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Old 17th February 2010, 10:00 PM   #29
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Thanks John for the link to the Excel sheet, had a bit of play with it.
Actually I just recall from my memory that the humans ears are very insensitive to distortion in bass frequency region so a couple of % won't be very noticeable.

Over-damping of loudspeaker boxes need a capable element to compensate for the loss, eg. weak motor and high Qt will create just thin and boomy bass at the higher bass frequencies and no damping material can compensate for that and these types of elements starts to require very big enclosures (Like the Dynaudio 30W-100, actually all Dynaudio with VC on the outside are very bad performers as a true bass element.), in general Qt over 0.45 starts to get a bit far from the optimal Qt for BR but depends to some extent on some other parameters too.
Just a couple of my c.

Cheers Michael
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