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Author Topic: Danley Demo Review  (Read 40855 times)

Paul Dershem

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Re: Danley Demo Review
« Reply #90 on: August 26, 2009, 01:01:41 am »

Thanks for your most thoughtful reply. Very interesting stuff, indeed!    Smile


I found and interesting discussion of group delay here:
http://www.trueaudio.com/post_010.htm
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Please be patient; I'm a noob!

Phillip_Graham

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Re: Danley Demo Review
« Reply #91 on: August 26, 2009, 01:16:33 pm »

Rory Buszka wrote on Tue, 25 August 2009 23:10

From the DIY department, here's a tapped horn design that a friend of mine and I designed and built in April 2008. It's an unconventional design in that it deviates from the typical conical tapped horn by incorporating a 2.2:1 restriction at the mouth that forms an acoustic mass element, effectively shifting the low corner of the horn down to about 45 Hz. This makes it the first (that I'm aware of) in a new class of tapped horn designs: the "Mass-Loaded Tapped Horn". Put simply, a bit of efficiency is sacrificed to achieve a slightly lower corner frequency; the tradeoff is that the more mass is added, the lower the overall efficiency. A very small amount of mass is added in this design, but I've seen promising things from designs where more mass is added.

...

The working title for the design is the "Hornet". Jerry McNutt of Eminence is using a 40Hz version designed for the HL-10 and is pleased with it; development of the ML-TH concept is ongoing.



Rory,

Since we are discussing such designs, I should mention that Art Welter and I cooked up something related to your design, but that is not a tapped horn.

I was inspired by the design of a class of optically "pumped" "q-switched" laser resonator cavities.  Art took to calling it the "Resopump."

There is a mouth reactance, and also a precisely-placed secondary reactance.  The coupled reactances are "pumped" by the driver, which has one side exposed to the open air.

Art went and put flesh on my theoretical bones, and tweaked the mouth cross sectional area for best performance.  Externally the design looks like a standard vented box with a slot port, but the measured response is similar to a bandpass enclosure.

I also started with the HL10C as the preferred transducer transducer, with its high BL and high FS.

I'm not sure its a viable commercial product, but the model behavior was accurately reflected by the as-built device.

Another way to skin the bass cat...
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Rory Buszka

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Re: Danley Demo Review
« Reply #92 on: August 26, 2009, 06:22:26 pm »

Phil, that sounds like an intriguing design, and I'd like to see a schematic just so I can understand the system you're describing. One thing I do want to mention, though, is that even though an acoustic mass element is used in my design, there is very little (if any) helmholtz resonance taking place (the type of resonance where the entire volume of air inside the enclosure comprises the air spring). Instead, the mass element is there to modify the quarter-wavelength resonance of the pipe. As best I understand it now, it's like adding more path length to the waveguide, but more resistance as well. A constriction at the end of the horn, being of negligible length, would behave acoustically like a resistor, and would only serve to increase the resonant character of the horn while decreasing overall SPL response, but a mass element (such as a port with a defined length) has a reactance that shifts the low corner of the horn's response even lower in frequency.

Send me a PM with details of the design, if you'd be so kind.
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Best Regards,

Rory Buszka
(The Gearmonger)

If it works, but you don't know why it works, then you haven't done any engineering.

Ivan Beaver

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Re: Danley Demo Review
« Reply #93 on: August 27, 2009, 06:37:18 am »

Paul Dershem wrote on Wed, 26 August 2009 01:01

Thanks for your most thoughtful reply. Very interesting stuff, indeed!    Smile


I found and interesting discussion of group delay here:
http://www.trueaudio.com/post_010.htm


I didn't read very far into that discussion, but I saw nowhere at the beginning where they were discussing GROUP delay. I say discussions about plain old regular signal (time) delay.

Very different animals.  I think they are confusing the two terms.

Maybe later on it turns into Group delay-I don't know.
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For every complicated question-there is a simple- easy to understand WRONG answer.

Can I have some more talent in the monitors--PLEASE?

Ivan Beaver
dB Audio & Video Inc.
Danley Sound Labs

Phillip_Graham

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Re: Danley Demo Review
« Reply #94 on: August 27, 2009, 07:24:11 am »

Rory Buszka wrote on Wed, 26 August 2009 18:22

Phil, that sounds like an intriguing design, and I'd like to see a schematic just so I can understand the system you're describing. One thing I do want to mention, though, is that even though an acoustic mass element is used in my design, there is very little (if any) helmholtz resonance taking place (the type of resonance where the entire volume of air inside the enclosure comprises the air spring). Instead, the mass element is there to modify the quarter-wavelength resonance of the pipe.


I'm not describing a Helmholtz case either, though you now have me wonder if the laser guys consider population inversion in the cavity to like Helmholtz resonance...

I like, like you, are modifying the acoustic impedance at the pipe end.

Quote:


A constriction at the end of the horn, being of negligible length, would behave acoustically like a resistor, and would only serve to increase the resonant character of the horn while decreasing overall SPL response, but a mass element (such as a port with a defined length) has a reactance that shifts the low corner of the horn's response even lower in frequency.


I think that a constriction at the flare end still has an effect on the distributed reactance of the flare, and therefore will still exhibit a similar effect.
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Silas Pradetto

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Re: Danley Demo Review
« Reply #95 on: July 06, 2010, 04:19:01 pm »

Pascal Pincosy wrote on Sat, 22 August 2009 18:16

Silas Pradetto wrote on Fri, 21 August 2009 17:45

I was more pointing out the ridiculousness of the crossover accusations. Like I wouldn't notice if I was sending full range to the sub? I definitely ran pink first full range, and let me tell you, the wash coming off the back of those woofers is LOUD.


FWIW I recently demo-ed the TH-412 (I'll have a review of it and the TH-46 posted soon) and I ran into exactly the same problem. With the TH-412 getting 2 X 2500 watts, at full power the drivers sounded like they were going to come apart and the racket coming out of the cabinet was quite loud. We solved the problem by turning the gain down a bit and raising the HPF from 25Hz to 30Hz.


I know I'm bumping an old thread here, but it was never concluded properly and an unassuming reader might conclude that the TH412 is a piece of crap.

Since Adrian started the real review with the most impossibly searchable, misspelled title possible, I'll link everyone to the review of the real TH412.

Here is the TH412 review using the updated woofers:

http://srforums.prosoundweb.com/index.php/m/480312/14303

The original TH412 design used neo woofers which made a bad "cracking" sound due to some air compression problem in the voice coil area. Nothing to do with the cabinet design itself.

Thanks!
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