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Old 21st November 2004, 06:11 PM   #1
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Default Baffles and steps

We all know that baffle step response can be a problem and there are ways to compensate for it.

We also know about sonotube for subwoofers, but how about as an enclosure for mid bass drivers? What potential problems might there be with baffle step response? My intuition says none. Am I right?

I rember in Pasadena there used to be a place called Gross National Products or GNP. They came to my attention when a friend told me I had to hear their lead cylinder speakers. It was one of several in-house designs. They were quite easily one of the best speakers I'd heard at the time.

Since then I've learned that lead does not a great enclosure make.
Sonotube however does.

Can you see where I'm going with this?

Has anybody seen other systems using tubes for enclosures?
Have any of you built such systems?

Thanks in advance for any information you might provide.
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Old 22nd November 2004, 03:27 AM   #2
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My understanding is that mounting a driver in the middle of a round baffle has the most problems with frequency response due to diffraction; since the driver is exactly the same distance from the edge of the baffle all the way around, the response irregularities tend to be few but VERY severe.

Now if when you say "midbass" you mean a dedicated driver for, say, a 4-way system that handles only the "middle of the bass" then these FR problems might be sufficiently out of band to not be a concern. But if you meant "midbass" as in a bass/midrange driver for a 2-way, then you'd probably run into problems.

The picture you have in your head may be what happens when you mount a driver to a sphere, I've heard you can have great results with that but unfortunately they don't sell custom-drilled hollow bowling balls at Home Depot.
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Old 22nd November 2004, 05:21 AM   #3
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Quote:
My understanding is that mounting a driver in the middle of a round baffle has the most problems with frequency response due to diffraction; since the driver is exactly the same distance from the edge of the baffle all the way around, the response irregularities tend to be few but VERY severe.

Now if when you say "midbass" you mean a dedicated driver for, say, a 4-way system that handles only the "middle of the bass" then these FR problems might be sufficiently out of band to not be a concern. But if you meant "midbass" as in a bass/midrange driver for a 2-way, then you'd probably run into problems.

The picture you have in your head may be what happens when you mount a driver to a sphere, I've heard you can have great results with that but unfortunately they don't sell custom-drilled hollow bowling balls at Home Depot.


I'm thinking of something like a straight 2 way or an M-T-M using 7" mid-woofers. Having done some further research,I have confrmed that indeed a tube is entirely the wrong shape. I still wonder how the hell they got those GNP speakers to sound so good, though.

I do know where to get spherical enclosures but the cost is more than I'd be willing to invest, plus there's the WAF.
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Old 22nd November 2004, 04:22 PM   #4
cjd is offline cjd  United States
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Mounting into the end of a tube is a problem for higher frequency drivers.

Mounting into the side, if you can pull it off, is closer to a sphere than most enclosures - which is a good thing.

C
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Old 22nd November 2004, 06:00 PM   #5
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If the tube is essentially the same diameter as the driver you end up with really early diffraction effects which shouldn't be too bad... a little shaping helps too (ie B&W Nautilus tweeter), but if you need to get bigger than that a shaped baffle with the tube hanging off the back is probably called for.

dave
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Old 22nd November 2004, 10:13 PM   #6
Ron E is offline Ron E  United States
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You can simulate the baffle diffraction effects with several different freeware tools. No shape is really perfect. A sphere offers very smooth diffraction response assuming a small source and a smooth sphere. A rectangle can still offer quite smooth response if you mount the driver properly. Proper crossover design is much more important than baffle shape.
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Old 23rd November 2004, 03:23 AM   #7
andy2 is offline andy2  United States
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I am just a beginner but from Dickason book, mounting the tweeter off to one side help DF problem. Proac does this I believe.
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Old 23rd November 2004, 09:00 AM   #8
rabbitz is offline rabbitz  Australia
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If you notice the designs he has in the Loudspeaker Design Cookbook, none of the stereo speakers use offset tweeters.

A case of do as I say not as I do.
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Old 25th November 2004, 06:31 PM   #9
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If the tube is essentially the same diameter as the driver you end up with really early diffraction effects which shouldn't be too bad... a little shaping helps too (ie B&W Nautilus tweeter), but if you need to get bigger than that a shaped baffle with the tube hanging off the back is probably called for.

dave


If I were to do it at all, it would be with tubes that were the same diameter as the drivers..

It's beginning to look like a better option would be to mount the drivers on an appropriate size baffle and mount the tube behaind it.

I just liked the look of the cylindrical speakers I saw years ago at GNP.
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