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Old 15th February 2010, 02:00 AM   #11
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John - that was my point. The YG comment said "elimination of resonances
at the source, RATHER than their absorption through stuffing, dramatically lowers enclosure losses" The source being the driver. I was pointing to the mechanical coupling of the driver/baffle system to the rest of the enclosure which is not discussed but certainly a source of vibration that can lead to resonance in an enclosure panel.

I could load the .pdf but now I was able to open it and see they are talking about box geometry.
It is a hyperbole ad to say the least.

Last edited by stephenmarklay; 15th February 2010 at 02:19 AM.
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Old 15th February 2010, 02:56 AM   #12
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The driver can be clamped to the cabinet. The cabinet can be made like a wedge. An acoustic "swamp" can be made staring with no damping around the driver, then soft, then harder and then even harder material. I usually watch the impedance curve, A dynamic speaker is a reciprocal device so in a way a microphone. Actually Baxandal had an AES paper where he has shown how to transfer a speaker into a microphone. Watch the small wricles in the impedance curve. The phase of the impedance is usually more sensitive visually then the magnitude. The cabinet shows its presence usually in the fundamental tone range between 150 and 300Hz provide the cabinet is of "medium" size. Wrinkles higher up can be the sesult of bad cone termination and can not be influenced by damping material. When the wrikles in the impedance curve are JUST gone the damping is optimal in my experience. More damping will lower the sensitivity of a reflex box for example and more damping may bring no benefit to lower the sound that comes back trough the cone. One exeption is a closed box where more damping can extend the frequency response in the lower reaches because it has a strong effect on the Q and resonance frequency. A totally overstuffed small box can have a surprisingly low resonance. Rockwool is best for that kind of experiment because it is quite heavy and dense.
I usually like "soft" boxes better then metal boxes two. A double wall construction can have both benefits.
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Old 15th February 2010, 05:02 AM   #13
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I like this thread... sorry I have no input at all to give. Just thanking you guys for all this information. It was an awesome read.
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Old 15th February 2010, 05:46 AM   #14
Key is offline Key  United States
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Well with YG I would think they are kind of implying there metal boxes are less resonant than wood. Or something along those lines. They are keeping it open ended and letting your imagination and the pictures fill in the blanks haha.

Does YG decouple their drivers from the baffle? I've seen speakers with decoupled tweeters or something but has anyone really made speakers that are decoupled with mechanical bushings or something? Or does that just kill the whole baffle loading effect and force you to use more power or drivers?
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Old 15th February 2010, 05:52 AM   #15
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Quote:
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has anyone really made speakers that are decoupled with mechanical bushings or something? Or does that just kill the whole baffle loading effect and force you to use more power or drivers?
Fujitsu Ten Eclipse

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Old 15th February 2010, 05:54 AM   #16
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Originally Posted by Joachim Gerhard View Post
The driver can be clamped to the cabinet. The cabinet can be made like a wedge. An acoustic "swamp" can be made staring with no damping around the driver, then soft, then harder and then even harder material.
The mid-tweeter in Tysen uses that technique but also throws a TL into the mix

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Old 15th February 2010, 11:53 PM   #17
Key is offline Key  United States
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Cool thanks. Those are some strange looking speakers.
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Old 16th February 2010, 12:12 AM   #18
ScottG is offline ScottG  United States
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I've mentioned poor results due to "stuffing" several times before. Here is one thread:

My Fostex FE 108EZ project, Part 2

Notably:

Me:

"..Stuffing should increase resistance and subjectively "suck the life" out of the drivers. (the closer the stuffing to the driver, the worse the effect.).."


Taperwood:

"Scott,

Just this afternoon I tried stuffing in the CC. I tried it directly behind the driver and also just in the V-shape part, both a lot and a little bit. You are right, the life is completely sucked out. It was like sticking your ear up to a midrange driver (well, not that bad but close). My wife stuck her head in the room and said "there's something wrong with that recording."

However, it seemed that vocal resolution was better, but I don't know if that was because it was so forward or something else going on."


Me:

"If your wife says that then you KNOW something is wrong. Funny thing is that it will actually measure better on a CSD plot. This is another classic case of measurements leading to a WRONG conclusion. This could have to do with the altered behaviour being wrong in the microsecond range and not the millisecond range. In otherwords every CSD plot I've seen is millisecond, not microsecond - and so it won't really be visible.

I bet another thing occured:

..centered imaging remained about the same (maybe better, maybe worse - likely moved forward near the plane of the speakers), but off center imaging probably sounds a lot closer to the speakers (perhaps even as if its comming from the speakers).

The cleaner vocals was likely a product of removing ambiant information from the track and leaving just the vocals/instruments. (..kinda like scrubbing out the sound stage.) My guess is that there would be very little change for tracks with close mic vocals and little or no hall-sound/reverb (..possibly a little better).

The funny thing is that topic seems to be restricted to the fullrange forum. The other so-called "progressive" forums dealing with "real" speakers never seem to talk about this (..except for the question "what happened to imaging depth?")."


Taperwood:

"Scott, that is exactly what happened. I couldn't have described it any better by writing an entire book. Thank you."




Of course now I "stand" corrected - it now *is* being "talked about.
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Old 16th February 2010, 12:30 AM   #19
ScottG is offline ScottG  United States
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Quote:
Originally Posted by Key View Post
Well with YG I would think they are kind of implying there metal boxes are less resonant than wood. Or something along those lines. They are keeping it open ended and letting your imagination and the pictures fill in the blanks haha.

Does YG decouple their drivers from the baffle? I've seen speakers with decoupled tweeters or something but has anyone really made speakers that are decoupled with mechanical bushings or something? Or does that just kill the whole baffle loading effect and force you to use more power or drivers?

Actually they are referring to linear decay.

You can generally improve a driver's linear decay along traditional time measurements with added stuffing - particularly if the driver doesn't have well suppressed diaphragm modes and is NOT made with a material that has high internal loss.

In this case what they are saying is that drivers they have selected already have good linear decay, and don't need to be "cleaned up" via stuffing.


The same is particularly true for tweeters.

Note that the more expensive the tweeter in a "line", the *less* stuffing it has in it's rear chamber (generally).

In fact manufacturers like scan speak go to great lengths to create chambers to "sink" the rear output of the driver. i.e. multiple labyrinths.
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Old 16th February 2010, 09:33 AM   #20
graaf is offline graaf  Poland
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Quote:
Originally Posted by john k... View Post
The nonlinearity of the air in the box makes a nonlinear spring which can introduce distortion. However, unless the box is small and the change in volume due to driver excursion is large (Big woofer in small box) this nonlinearity is pretty insignificant.
are there any user-friendly formulas for calculating this effect? I mean for rough determination if the box is too small for a given displacement?
What kind of distortion can arise? Does non-linear in this context
mean harmonic? If so, what is tha scale of the problem? In other words how much distortion in what frequency bands can arise when the box is too small for a given displacement?

I ask becasue I wonder what volume of a closed box is best compromise.
From the perspective of internal reflections and standing waves the smaller the better, isn't it?

Which one of the two sources of distortion/colouration is measurably and/or audibly worse: "a nonlinear spring" or "retransmission of sound through the cone" becasue of "internal reflections and standing waves"?

best,
graaf
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