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Old 17th December 2005, 02:38 PM   #11
Zaph is offline Zaph  United States
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Quote:
Originally posted by ooheadsoo
Thanks for the reply, John.

Do you think there is benefit in extending the directionality of the speaker by crossing the drivers down into the 1khz or below range (with different drivers of course) ala Dr. Geddes's implementation or SP Technology?
Yes, that could be done but it might be hard to get a significant power handling increase out of the MCM horn lens, simply because it is a bit shallow and only 6" diameter. As I built it, I think the increase in power handling below 1500hz is minor.

Or, if you're getting at the idea of adding a waveguide to the woofer, I don't think it's a good idea. The size of the waveguide would be large, and the tweeter would be so far away that there would be severe lobing and the vertical listening axis would be so narrow that even a few inches could create a large null.

For thosing thinking of a "small" waveguide on a woofer, consider that one these has to be substantially larger than the radiating surface to even be useful at all. Otherwise it just causes a large peak and dip in response.

John
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Old 17th December 2005, 04:27 PM   #12
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You could try making some sort of weird custom waveguide that houses both a mid and a tweeter. Go to http://www.genelec.com/products/1038...es/b_1038b.jpg to see what I mean. The midrange driver doesn't look like it's that much further away from the tweeter in Zaph's 2 way design. Obviously if you had seperate waveguides for the mid and tweeter individually things would be different.
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Old 17th December 2005, 11:31 PM   #13
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very nice project john, it's been a long time since i wanted to design a speaker with waveguide, as some of my most beloved studio monitors do have waveguides.

parts express do sell bigger waveguides, up to 12"

As long as we are talking about directivity what do you think would be the effect of doing a 2 way with 6" or 8" waveguide and 8" woofer ?

or lets be crazy, assuming i find a woofer that's having a well extended response, a system with a 10" woofer with a 8" or 10" waveguide (actively crossed over so i can use slopes as steep as 48 db / octave)
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Old 18th December 2005, 12:06 AM   #14
Zaph is offline Zaph  United States
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Quote:
Originally posted by Depth Charge
You could try making some sort of weird custom waveguide that houses both a mid and a tweeter. Go to http://www.genelec.com/products/1038...es/b_1038b.jpg to see what I mean.
Those would be great. I have no doubt that the Genelec monitors sound incredible. I've heard good things about them. I can't see myself trying to build a mulit-driver waveguide anythime soon. I can barely hack up the plastic from MCM, much less do some custom forming.


Quote:
Originally posted by Nemophyle
very nice project john, it's been a long time since i wanted to design a speaker with waveguide, as some of my most beloved studio monitors do have waveguides.

parts express do sell bigger waveguides, up to 12"

As long as we are talking about directivity what do you think would be the effect of doing a 2 way with 6" or 8" waveguide and 8" woofer ?

or lets be crazy, assuming i find a woofer that's having a well extended response, a system with a 10" woofer with a 8" or 10" waveguide (actively crossed over so i can use slopes as steep as 48 db / octave)
I was completely unaware that Parts Express sells waveguides. Digging around there, I see the 8", 10" and 12" . Just looking at them, I have a slight concern about their shape - mainly the edges around the outside. I believe there should be a smooth transition from the waveguide to the baffle or an irregular diffraction response could result. I'm just guessing though, I think I'll buy one to check out. They're cheap. Depending on how well the response curve looks, one of those could make a nice combo with a 8 or 10" driver.
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Old 18th December 2005, 12:40 AM   #15
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Actually, making ones own waveguide shouldn't be TOO hard...

Search google for "diy vacuum forming table"...

You could make it out of 1/4" plexy and paint the backside silver for a super spiffy look...

I might actually investigate this :-D
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Old 18th December 2005, 11:53 AM   #16
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i'm gonna buy a couple of 8" and a couple of 10" , and measure them with a silk dome... anyway i think that the edges could be rounded with some patience if it is better for the sound.

i was planning of using this very nice 10" driver with a tweeter ==>
A.T.S French drivers
look at the HG 25

they use a sandwich ceramic/paper/ceramic with an elastic compound inbetween.


what do you think is better ? 8" or 10 " waveguide for this application ?
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Old 18th December 2005, 04:11 PM   #17
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Zapf project is just amazing, you can really afford using the best components.

What is the x-y co-ordinates (pattern) for the wave guide curve ?
Thinking of cnc-machining the wave guide direct to the complete front baffle (ex. mdf/baltic birch)
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Old 18th December 2005, 11:35 PM   #18
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wilbur-x asked:
Quote:
What is the x-y co-ordinates (pattern) for the wave guide curve ?
links to Earl Gedde's waveguide papers are in post #10 here:

Acoustic Waveguide
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Old 19th December 2005, 05:00 AM   #19
JonPike is offline JonPike  United States
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Quote:
Originally posted by Nemophyle

As long as we are talking about directivity what do you think would be the effect of doing a 2 way with 6" or 8" waveguide and 8" woofer ?

or lets be crazy, assuming i find a woofer that's having a well extended response, a system with a 10" woofer with a 8" or 10" waveguide (actively crossed over so i can use slopes as steep as 48 db / octave) [/B]
Ahhh... Nemophyle beats me to it.. ;-)

I was thinking the same thoughts... being that I have a pair of RS225's sitting here waiting for some kind of project...

Wondering how much lower one might be able to usefully use a tweeter with the waveguide loading. That too, has gotten touched upon in this thread, but any further thoughts on that John? I know there is only so much Xmax to deal with on a particular tweeter, and as one goes lower in frequency it's easier to use it up... How can we figure out how low can we go before distortion or power handling starts to become a problem?

I've done some preliminary first CSD's (new SE user here) on the RS225's, and it looks like the big energy storage is around 1.4-1.6Khz, assuming I'm doing things right. So, a serious challange to do a 2 way, for most tweeters. But... if you could cross lower than that, well, the possibilites open up..

I'm also paitently waiting to hear more info on how a certain RS28-RS225 project turned out.

The SP Technologies site was interesting... and got me wondering if they are using some kind of custom spec tweeter, or are they thru the wonders of proper horn loading, getting something more standard to be usefully crossed over at the 750Hz (or 900) that they quote?

If you could get a 27TDFC to cross that low, it should be a great match with the RS225 or other large woofers..
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Old 19th December 2005, 12:18 PM   #20
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hey jonpike

there is a project with RS225-RS28 that turned out quite well : RS225+RS28

I personnally wanted to use a 10". It's something you almost never see,at least in the non-pro drivers world, because of too much directivity issues.But then the waveguide would really help resolve theses issues for what i did understand

the use of a 10" aluminium cone is pretty excluded because of breakups too much too early. except maybe this one that maybe very interresting with a steep slope (24 db at 1500 + notch around 2000 or 48db at 1700)
alcone AC10HE

but the A.T.S woofer i previously linked seems to have at the same time a very rigid and very well damped cone that may be perfect for what i want to do.

but it would require a big waveguide
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