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Old 1st April 2010, 07:25 PM   #1
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Default Level-dependend Sound Quality by certainly Bass Drivers - very bad sound at low level

Over the years I observe always very bad sound in the low level sonic aera by certaily material of the surround - mostly certainly kind of rubber material. All this loudspeakers have in most (not in all) cases a low value of mechanical quality (parameter: Qms).

If I measure the parameters, I observe also level independend so as temperature independend Thiele Small parameter variation for Fres, Qms, Qes and Vas, except in such cases, where the low QMS value caused only through aluminium shortening ring on the voice coil and copper capped pole piece.

For my subwoofer and loudspeaker projects I use therefore mostly cloth surrounds or foam surrounds. Here I haven't above mentioned unwanted effects. There are very few rubber surounds with level and temperature independend behaviour. The KEF B110A-SP1003 or the various types of PHL's B17 series are good examples. Bad examples through the selected rubber material for surround are certainly models of the Dynaudio drivers (at least that types from the Contour series, that I know).

The parameter Qms and thus Rms consists of a nonlinear (level-dependent) component and a linear (level independent and temperature independend) component.

The linear component causes through aluminium shortening ring so as copper capped pole piece - e. g. Peerless HDS182 about
http://www.d-s-t.com.au/data/Peerless/850467.pdf

And the non linear (level-dependent) component causes through the rubber material of surround or - if cloth material used - the material of impregnation and its behavior at different strains und different temperatures (by the spider only the material of impregnation and its behavior).

Which measuring methods exist today for loudspeaker chassis TSP measurement, to determine isolated these two influence factors for the parameter Qms resp. Rms?

Thank you for your comments

Last edited by tiefbassuebertr; 1st April 2010 at 07:29 PM.
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Old 23rd September 2011, 04:28 PM   #2
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are there no informations ??
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Old 23rd September 2011, 05:34 PM   #3
tvi is offline tvi  Australia
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A lot of the problem I'd think comes from chasing Xmax, needs a strong/thick surround rather than linear.
Foam surrounds in a sealed box and trying to get high spls makes me edgy. Maybe horn or slot loading.

I found this
http://profesional.beyma.com/ingles/...uspensions.pdf
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Old 23rd September 2011, 06:43 PM   #4
tinitus is offline tinitus  Europe
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always 'question' what you are being told by others
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Old 24th September 2011, 06:27 PM   #5
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Are you sure that non linear distortion caused by the surround sounds bad? for example 1st harmonic distortion products are not bad at all.
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Old 2nd March 2012, 02:27 PM   #6
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Are there any news concerning measuring methods for extract the linear and non linear parts arround the value of mechanical losses (Qms) ??

Is the value extremly low in case of HF drivers (tweeters) the case is quite clear: Ferrofluid is in use (I hate it like the plague).

But in case of the Bass-Mid aera by low Qms values it is mostly hard to say - have a look to the drivers from Morel, Dynaudio and Seas.

If I want modify crossover networks by loudspeaker models, where this brands are in use, I always get stomach ache and headache.

Last edited by tiefbassuebertr; 2nd March 2012 at 02:32 PM.
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Old 2nd March 2012, 06:46 PM   #7
hm is offline hm  Europe
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Hello,
"bad sound in the low level sonic aera"
i wrote:
The inertia of the a heavy membrane slows the music signal down and this is especially
noticeable on lower sound levels, typical for a normal living room, where the larger
the mass of the membrane, the more it will dampen the signal, which is the main reason
for the serious lack of bass resolution in heavy bass membranes.
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Old 2nd March 2012, 07:39 PM   #8
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Quote:
Originally Posted by hm View Post
Hello,
"bad sound in the low level sonic aera"
i wrote:
The inertia of the a heavy membrane slows the music signal down and this is especially
noticeable on lower sound levels, typical for a normal living room, where the larger
the mass of the membrane, the more it will dampen the signal, which is the main reason
for the serious lack of bass resolution in heavy bass membranes.
Most developers and manufacturers of electrostatic loudspeakers tell me the same.

But this is wrong, as long as a suspension with very low loss is present (check therefore always the parameter "Qms" and "Rms").

If you have heard this transducer from Morel (Mms 105 g) about
http://www.morelhifi.com/products/pd...0UW%201258.pdf
against follow transducer from Eminence, model Lab12 (146 g) about
http://www.eminence.com/pdf/LAB_12.pdf
you will understand, why your estimate isn't correct.

If that occurs, what you describe in previous post, then it could be a also driver like the follow:
http://www.ground-zero-audio.com/en/...zpw-12spl.html
Here the two parameters Qms and Rms are not published.
Nevertheless such a driver can also provide good bass transmission at low levels.
But you only know exactly this after after a thorough investigation (i. e. explicit soundcheck).
In case of the Morel bass transducer model the case is clear: The behaviour is exact as you say in previous post.

BTW - the most significant disadvantages of small cubes in subwoofer applications are the very small piston aera. This means too many places in the listening room with too much bass and not enough bass.

Last edited by tiefbassuebertr; 2nd March 2012 at 07:56 PM.
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Old 2nd March 2012, 08:10 PM   #9
forr is offline forr  France
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Quote:
Originally Posted by hm View Post
The inertia of the a heavy membrane slows the music signal down and this is especially
noticeable on lower sound levels, typical for a normal living room, where the larger
the mass of the membrane, the more it will dampen the signal, which is the main reason
for the serious lack of bass resolution in heavy bass membranes.
I suggest you try to prove it using scientific means.

Last edited by forr; 2nd March 2012 at 08:18 PM.
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Old 2nd March 2012, 09:53 PM   #10
hm is offline hm  Europe
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Hello,
it is listenable,
proved by Hornlautsprecher - Avantgarde Acoustic? Hornlautsprecher GMBH
they wrote this in philosophie ~2000
"The inertia of the a heavy membrane slows the music signal down and this is especially
noticeable on lower sound levels, typical for a normal living room, where the larger
the mass of the membrane, the more it will dampen the signal, which is the main reason
for the serious lack of bass resolution in heavy bass membranes.The inertia of the a heavy membrane slows the music signal down and this is especially
noticeable on lower sound levels, typical for a normal living room, where the larger
the mass of the membrane, the more it will dampen the signal, which is the main reason
for the serious lack of bass resolution in heavy bass membranes. "

In my double horns you get 100 dB 1W1m with less of 1 mm stroke down to 35 Hz and no
bassimpedanz = below 50 Hz ~4 Ohm, and you know a difference of 6 dB is not able to fill with a bigger amp.

(m
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