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Multi-Way Conventional loudspeakers with crossovers

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Old 19th August 2010, 07:30 PM   #7251
mige0 is offline mige0  Austria
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Ok, ok - and what *if* we combat about the key word of "possibly" - for any real world speaker
I "guess", you can't even hold that ...

C'mon, you are not *that* old !?


If you prefer, I'd agree on rephrasing "combating" with "teamwork investigation"


Michael

Last edited by mige0; 19th August 2010 at 07:45 PM.
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Old 19th August 2010, 08:23 PM   #7252
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Default Progress !

Sorry to interrupt the research ....
Just thought Gary and Lynn might like the attached pic of my first Jensen bass unit for the combination . I know it took me a barely finite amount of time to do this, but I'm quite proud of the woodwork !
I got some autoformers for the 288-H's from Dave a while back, and it was nice to find the horns sounded the same with or without the autoformers . Good effort Dave !
I'm off on hols to Austria now before tackling the final work on speaker no.2 ....

Mark
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Old 19th August 2010, 08:48 PM   #7253
g3dahl is online now g3dahl  United States
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Beautiful work, Mark!!

I noticed your discussion thread on dave slagle's forum. Glad to hear that you got good results.

Gary Dahl
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Old 19th August 2010, 10:43 PM   #7254
Pano is offline Pano  United States
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Originally Posted by g3dahl View Post
I normally use a parallel ("swamping") resistor along with an autoformer, which as I understand it, locks down the impedance.
Yes indeed. Thanks for the links to Dave's forum. Lot's of info there.
I'm curious about the difference in sound between and autoformer and parallel resistor vs series + parallel resistor. Basically swapping the series resistor for the autoformer.
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Old 20th August 2010, 12:57 AM   #7255
soongsc is offline soongsc  Taiwan
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Quote:
Originally Posted by mige0 View Post
Ok, ok - and what *if* we combat about the key word of "possibly" - for any real world speaker
I "guess", you can't even hold that ...

C'mon, you are not *that* old !?


If you prefer, I'd agree on rephrasing "combating" with "teamwork investigation"


Michael
I think John is just pointing out that the points to consider rather than drawing conclusion.
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Old 20th August 2010, 04:16 AM   #7256
mige0 is offline mige0  Austria
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Given that John had done quite some investigation into Thermal Distortion - both on his page as well as almost for a whole thread - he probably should already *know* better.
If he has some ideas though, that thermal instability (run away) with current amps is a realistic scenario then I'd definitely would like to hear about.

To all of *my* knowledge / investigation on the topic of Thermal Distortion and thermal speaker behaviour, this is practically impossible - but lets see...
There IMO is an underlaying mis-concept/mis-interpretation about "thermodynamics" in heating/cooling mechanism that "possibly" leads to such conclusions.

But as said - there is always a good chance that I may have overlooked something. Being clearly in the second half of a full century but possibly not as old as John - I nevertheless would like to exercise in "getting gracefully old" by a teamwork investigation about thermal instability.

Michael

Last edited by mige0; 20th August 2010 at 04:43 AM.
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Old 20th August 2010, 04:37 AM   #7257
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Originally Posted by JohnPM View Post
Mike, whilst it is good to see a sense of humour around here, selectively editing my posts to make it appear as if I said the opposite of what I actually said is misleading for others browsing the thread, as Michael's post demonstrates, and kind of dishonest. To be fair to others you should edit your post.

Michael, the comments quoted were preceded by In my view the basic misconceptions underpinning the above are: which rather changes the meaning.

Mike, your earlier engine mapping analogy isn't really applicable to the discussion as engines are not LTI systems. I used to design engine, gearbox and chassis management and data acquisition systems for motorsport applications as it happens, though that was 2 decades ago. One of the most interesting engine types to deal with is two-strokes, as a single misfire has a dramatic effect on scavenging efficiency and hence the crankcase mixture - the early two-stroke fuel injection systems tried a simple map-based approach which was disastrous, as misfires caused havoc. The solution there is to model the crankcase mixture, using crankshaft acceleration as an input to the model. If that doesn't count as off-topic, even in a thread of 7,000+ posts, I don't know what does
Hi John, my apologies. Thankyou for attributing me with a sense of humour, however in this case my comment was due to my poor understanding and even poorer attention span. Must try harder.

Would you mind explaining why an engine is not an LTI system whereas a speaker is?

Best,
Mike
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Old 20th August 2010, 04:57 AM   #7258
soongsc is offline soongsc  Taiwan
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Quote:
Originally Posted by mige0 View Post
Given that John had done quite some investigation into Thermal Distortion - both on his page as well as almost for a whole thread - he probably should already *know* better.
If he has some ideas though, that thermal instability (run away) with current amps is a realistic scenario then I'd definitely would like to hear about.

To all of *my* knowledge / investigation on the topic of Thermal Distortion and thermal speaker behaviour, this is practically impossible - but lets see...
There IMO is an underlaying mis-concept/mis-interpretation about "thermodynamics" in heating/cooling mechanism that "possibly" leads to such conclusions.

But as said - there is always a good chance that I may have overlooked something. Being clearly in the second half of a full century but possibly not as old as John - I nevertheless would like to exercise in "getting gracefully old" by a teamwork investigation about thermal instability.

Michael
If anyone is really interested, putting together a simple Howland current pump using a chip amp might not be that difficult.
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Old 20th August 2010, 05:51 AM   #7259
CLS is offline CLS  Taiwan
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.... putting together a simple Howland current pump using a chip amp might not be that difficult.
Never heard of, and not studied it yet.

Maybe this would be similar (in some way, at least): Variable Amplifier Impedance

It's a mixed voltage and current feeadback circuit. Because it's quite simple to mod an existed ordinary SS amp to that kind of operation, I gave it a try.

Eventually I got 20 Ohm (or so) output impedance for my amp, and it works very well with my OB bass with low-Q woofers. (I posted a thread here before.)

Days ago, I happened to get a chance to listen to a CD with helluva bass, at a very satisfying level - pipe organ version of [Pictures at an Exhibition] (Dorian record). The woofers seemed fine, there was no sign of thermal problem, or any abnormal sound I could hear. They just kept blowing me away.
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Old 20th August 2010, 06:31 AM   #7260
soongsc is offline soongsc  Taiwan
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Information in simple to find by googling it. It may not be suitable for pure audio amplifier purposes, but could be usefull for thermal runaway studies.
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