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Old 25th May 2011, 01:01 PM   #1
oublie is offline oublie  United Kingdom
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Default Help with Silk Dome Tweeter Waveguide

Hi, Im building a pair of TMM Tline speakers the first one is built but i'm now working on the tweeter part. I'd Like to place the 1inch tweeter in a constant directivity waveguide so i've been working with hornresp to see if i can get the correct profile. There's an elderly gentleman I know who will be able to turn the guides on his lathe.

Here are some screenshots of what i've come up with. Am I on the right track and if not could someone advise please.
Attached Images
File Type: jpg CD Wharfedale Tweeter Waveguide.JPG (36.5 KB, 336 views)
File Type: jpg CD Wharfedale Tweeter Waveguide params.JPG (58.5 KB, 324 views)
File Type: jpg CD Wharfedale Tweeter Waveguide resp.JPG (41.2 KB, 320 views)
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Old 25th May 2011, 01:37 PM   #2
ttan98 is online now ttan98  Australia
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Hi,

I am doing something similar, but haven't got around doing it.

If I were to get the response you are geting I would be using an equalizer and make it flat, there measure the directivity 0,15,30,45deg Use a DSP to equalise is much faster.

A passive equalizer may include a parallel cap and resistor connected in series with the tweeter.
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Old 25th May 2011, 02:15 PM   #3
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It looks like you're using Hornresp to put an exponential horn on the tweeter. I don't think wave guides are the same as horns, so that may be part of the problem you're seeing. There is also some missing data in your model.

Last edited by dirkwright; 25th May 2011 at 02:18 PM.
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Old 25th May 2011, 02:16 PM   #4
AllenB is offline AllenB  Australia
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I would try making it a little longer, for a more narrow angle.
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Old 25th May 2011, 02:29 PM   #5
oublie is offline oublie  United Kingdom
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Quote:
Originally Posted by dirkwright View Post
It looks like you're using Hornresp to put an exponential horn on the tweeter. I don't think wave guides are the same as horns, so that may be part of the problem you're seeing. There is also some missing data in your model.
what's missing and ill try and fill it in
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Old 25th May 2011, 02:43 PM   #6
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Quote:
Originally Posted by oublie View Post
what's missing and ill try and fill it in
Sorry, my mistake. Nothing missing. I'm not familiar with the design of wave guides, so I can't really help there, but I assume Hornresp is designed for horns and not wave guides. Using the program, the response flattens out if you make the horn longer. How did you calculate the mouth area?
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Old 25th May 2011, 02:43 PM   #7
qusp is offline qusp  Australia
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watching with interest
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Old 25th May 2011, 03:42 PM   #8
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I did it in the past with a circular waveguide that followed the orriginal JBL CD flare and a starting angle of 100 degrees IFRC. Unfortunately the high symmetry gave it a pretty good dip (mouth reflection) on axis.

Your frequency response looks plausible to me (assuming you don't get a mouth dip). You will get a lot of gain towards the low end due to controlling directivity and better loading. At the high end your tweeter's directivity would already be close to the waveguide's so the axial gain diminishes.

Good Luck,
David S.
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Old 25th May 2011, 03:52 PM   #9
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Quote:
Originally Posted by oublie View Post
Hi, Im building a pair of TMM Tline speakers the first one is built but i'm now working on the tweeter part. I'd Like to place the 1inch tweeter in a constant directivity waveguide so i've been working with hornresp to see if i can get the correct profile. There's an elderly gentleman I know who will be able to turn the guides on his lathe.

Here are some screenshots of what i've come up with. Am I on the right track and if not could someone advise please.
This arrangement has a constant 120 deg beam width out to about 18,000 Hz. Is that what you're looking for?
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Old 25th May 2011, 04:10 PM   #10
oublie is offline oublie  United Kingdom
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these are for nearfield use with an acute 45 degree listening angle because of this i dont want the tweeters to beam. hopefully this is the correct method (im still a bit of a noob).

This all started with the design of a transmission line for my son's birthday. It has now evolved into 4' high dual 6/5" woofer t lines flat to 35hz with the tweeter filling in form approx 3khz upwards.
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