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Multi-Way Conventional loudspeakers with crossovers

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Old 7th April 2009, 05:27 PM   #5131
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Quote:
Originally posted by gedlee


This seems like looking for a needle in a haystack to me. Unless you are talking about driving the system with another source. If self driven then the very small back EMF when compared to the driven voltages would be hard to detect reliably. And then there is the fact that energy absorbed by the cone does not mean its all "reradiated", it could just be absorbed. How do you sort that out?

I've worked out a complete approach to do just that. If I ever bother to take sufficient data to demonstrate the approach I post a web page. Maybe I'll just write it up as a proposed approach.
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Old 7th April 2009, 06:48 PM   #5132
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by john k...
Bill indicated that if the cone was transparent sound would pass through it without exciting the cone to vibrate.
That would be a pretty useless speaker cone.

Sheldon
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Old 7th April 2009, 10:39 PM   #5133
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I knew my question in my last post was rough but when I typed it it was the last minute before I left work and picked up my kids from school yesterday so I had no time to define what was transparent and what was opague, etc.

Anyway, I have to say that JohnK's way of doing things is very impressive. Unlike some of us, me included of course, using assumptions, guesses, pseudo-science, (execuses us, we don't have time, at least I don't.) JohnK uses thorough scientific and engineering approach to look at even small problems.

In this instance, I guess (oh yes, guess again) JohnK's result was that the cone is rather opague (oh yes, guess again, no dB level defined) so it may be like what Gedlee said "needle in a haystack", but JohnK still "worked out a complete approach" to let us have a more accurate understanding of what is going on.

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Bill
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Old 7th April 2009, 10:56 PM   #5134
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yeah but gedlee is try to say.. that the leaky roof needs to be fixed before the waterspot on the sealing should be painted...


Quote:
Originally posted by HiFiNutNut
I knew my question in my last post was rough but when I typed it it was the last minute before I left work and picked up my kids from school yesterday so I had no time to define what was transparent and what was opague, etc.

Anyway, I have to say that JohnK's way of doing things is very impressive. Unlike some of us, me included of course, using assumptions, guesses, pseudo-science, (execuses us, we don't have time, at least I don't.) JohnK uses thorough scientific and engineering approach to look at even small problems.

In this instance, I guess (oh yes, guess again) JohnK's result was that the cone is rather opague (oh yes, guess again, no dB level defined) so it may be like what Gedlee said "needle in a haystack", but JohnK still "worked out a complete approach" to let us have a more accurate understanding of what is going on.

Regards,
Bill
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Old 8th April 2009, 12:04 AM   #5135
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I don't think cove transparency is a black and white issue. For example, a few years back I was working with a guy who had a small 2-way with Eton midrange. When measured in the enclosure there were obvious spikes in the frequency response and corresponding glitches in the impedance. Taken out of the box and mounted in an IEC baffle the response was smooth. So here is an obvious case where the driver was "transparent enough" that the builder's poorly damped enclosure was coloring the sound. Rethinking the enclosure design and adding sufficient damping solved the problem. So where is the threshold? This driver was obviously so transparent that the problem was obvious in the impedance curve. I don't think that the issue can just be swept under the rug under the guise that all drivers are acoustically opaque or all are transparent. Either way, OB mounting potentially eliminates the problem from consideration.
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Old 8th April 2009, 12:13 AM   #5136
Salas is offline Salas  Greece
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And that was a Kevlar sandwich with hex cell internal matrix layer? Imagine the hear through in a paper cone case.
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Old 8th April 2009, 01:33 AM   #5137
gedlee is offline gedlee  United States
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Quote:
Originally posted by john k...
I don't think cove transparency is a black and white issue. For example, a few years back I was working with a guy who had a small 2-way with Eton midrange. When measured in the enclosure there were obvious spikes in the frequency response and corresponding glitches in the impedance. Taken out of the box and mounted in an IEC baffle the response was smooth. So here is an obvious case where the driver was "transparent enough" that the builder's poorly damped enclosure was coloring the sound. Rethinking the enclosure design and adding sufficient damping solved the problem. So where is the threshold? This driver was obviously so transparent that the problem was obvious in the impedance curve. I don't think that the issue can just be swept under the rug under the guise that all drivers are acoustically opaque or all are transparent. Either way, OB mounting potentially eliminates the problem from consideration.
Nothing like this is ever black and white. But because there is an example of a problem design does not mean that all designs with boxes are flawed. I've tried to find this kind of thing on my speakers and I can't. The black to your white I suppose.
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Old 8th April 2009, 01:40 AM   #5138
dlr is offline dlr  United States
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Quote:
Originally posted by Salas
And that was a Kevlar sandwich with hex cell internal matrix layer? Imagine the hear through in a paper cone case.
I would expect there to be more transmission through a Kevlar sandwich, sandwich for stiffness, but low weight, and less through a well-damped paper composite cone such as those of Scan-Speak or Seas.

Dave
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Old 8th April 2009, 01:44 AM   #5139
Salas is offline Salas  Greece
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Those Etons are rigid but not lighter than paper. With damped paper things change. Worse case must be light paper full range cones. Talking all things equal of course. I.e. Different cones on that same reactive enclosure.
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Old 8th April 2009, 09:34 AM   #5140
Telstar is offline Telstar  Italy
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Quote:
Originally posted by Salas
Worse case must be light paper full range cones.
Like Feastrex?
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