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Old 28th June 2008, 10:53 PM   #1
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Default An interesting principle

Though I use only boxes without "exhaust" nowadys I find this one quite interesting.

When I first saw a picture of a Dynacord Planar Waveguide I did somehow not like it. Specially the fact that it was a reflex box radiating into said waveguide. I then thought that it must be possible to build some type of bandpass by the use of a quarterwave resonator in the front of the driver and a reflex box at it's rear. The advantages would be that the reflex-box would be smaller than a tube (like used in the Acoustic Wave Cannon) and the quarterwave resonator giving higher SPLs than just a reflex box in front (like it is used in 6th order bandpasses).

I then occasionally stumbled over the following Yamaha patent describing exactly what I was thinking of (though I don't like the particular designs shown in the patent):

http://v3.espacenet.com/textdoc?DB=E...=US5313525&F=0

The biggest advantage is that the patent has ceased due to non payment of the fees.

I never found the time to actually build one - but today I suddenly felt the urge to simulate one with "Hornresponse". I modelled a horn with just one conical section in the front having a veeeery low flare-rate. At the back it has a reflex chamber. The throat was slightly less than SD. A SD/Troat ratio around 1 looked the best in the simulations. The reflex box and the resonator are tuned slightly more than one octacve apart. The "driver" I used is just a hypothetical 15" one but maybe soemone is interested to try it with the parameters of a rel-world driver.
The (simulated of course) response doesn't look too bad over the frequercy range where it acts as a bandpass. See the atrtached diagram.

What do you think ?

Regards

Charles
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Old 29th June 2008, 04:35 PM   #2
gedlee is offline gedlee  United States
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This appears to be nothing more than a badely designed bandpass woofer.
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Old 29th June 2008, 05:30 PM   #3
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Obviously, you are simply at a preliminary stage of the design. So I would ignore the previous insult.

It looks like an interesting analogy to TL design. So there would be all sorts of neat things to play with along with the taper(s).

Hornresp is a very addictive piece of software isn't it?

Good Luck and keep us up to date
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Old 29th June 2008, 08:02 PM   #4
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Quote:
This appears to be nothing more than a badely designed bandpass woofer.
Yes it is in fact a bandpass. Since the "upper" resonator is a tube one has to deal with multiple resonances. I assume that this could be tamed by the use of the right crossover and slight stuffing if used below 100 to 150 Hz. The thing was never intended for high quality but for loud (which is nice too once in a while).


Quote:
Obviously, you are simply at a preliminary stage of the design. So I would ignore the previous insult.
Since he is more knowledgable than me regarding modeling of waveguides etc I don't see a problem with this critique. He had to take some insults here as well and he is still posting which is not so obvious.

I am most probably not going to try it out by myself but wanted to present the principle here since there are always people who are interested in "loud but compact".

Regards

Charles
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Old 29th June 2008, 10:20 PM   #5
gedlee is offline gedlee  United States
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Quote:
Originally posted by phase_accurate


Yes it is in fact a bandpass. Since the "upper" resonator is a tube one has to deal with multiple resonances. I assume that this could be tamed by the use of the right crossover and slight stuffing if used below 100 to 150 Hz. The thing was never intended for high quality but for loud (which is nice too once in a while).




Since he is more knowledgable than me regarding modeling of waveguides etc I don't see a problem with this critique. He had to take some insults here as well and he is still posting which is not so obvious.

I am most probably not going to try it out by myself but wanted to present the principle here since there are always people who are interested in "loud but compact".

Regards

Charles

It was intended to be an insult but simply a note that this same response could be achieve very easily with a bandpass design with a long port. But these resonances are not desirable at all and making the port shorter and moving them up in frequency facilitates using a LP filter to get rid of them. You will have thus achieved exactly the same design that I use for virtually all of my subs.
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Old 29th June 2008, 10:37 PM   #6
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The Karlson works like this too, (BR firing into a TL, which amounts to BP) but falls off on the low end due to the 'Karlson' slot along the length of the TL (has the same peaks in the highs too...)
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Old 29th June 2008, 11:00 PM   #7
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It was intended to be an insult but simply a note ....
So you actually plead guilty of trying to insult me ?

regards

Charles
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Old 29th June 2008, 11:30 PM   #8
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Now that's a funny typo.
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Old 30th June 2008, 12:37 AM   #9
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Old 30th June 2008, 02:34 AM   #10
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[QUOTE]Originally posted by gedlee
[B]


It was intended to be an insult but simply a note that this same response could be achieve very easily with a bandpass design with a long port.

Paging Dr, Freud, We have a code blue!..........






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