Measuring and voicing waveguides v.s. flush mount tweeters - diyAudio
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Old 6th March 2013, 08:19 AM   #1
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Default Measuring and voicing waveguides v.s. flush mount tweeters

I'm about to begin my first measurements/crossover design of a system with a waveguide. I was wondering if people who've worked with waveguide designs do anything different when taking measurements and designing the crossover. Here's the measurements of the tweeter on a flat baffle and in the waveguide: http://techtalk.parts-express.com/sh...09#post1841309 As you can see there's quite a bit of "droop" in the response off axis response for the WG compared to the flat baffle. I'm thinking if I approach this like a standard design the end result is going to sound dull/rolled off because of this. If I'm used to using on axis driver measurements for crossover design, should I use off axis measurements (let's say 30-40 degrees) for a project like this and plan on pointing the speakers more or less straight ahead? (I usually measure and listen about 5-10 degrees off axis to my non-waveguide designs.)

Last edited by dsrviola; 6th March 2013 at 05:48 PM.
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Old 6th March 2013, 04:07 PM   #2
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It depends on the waveguide, and your techtalk link is broken, but the answer to using 30-40 off-axis measurements is almost definitely no. If the -6dB pattern is close to constant directivity, you'll probably want a gently falling (3-6dB) response on-axis, and if the pattern is narrowing at HF maybe a more flat response on-axis.
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Old 6th March 2013, 05:49 PM   #3
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link repaired.
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Old 6th March 2013, 07:59 PM   #4
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Looks like you could treat it as an approximation of an 80 constant directivity waveguide to me. I'd design on-axis, incorporating compensation to flatten the on-axis response in your measurement to something like this below, and crossing over to where the midwoofer has an approx. 80 pattern, i.e. -6dB at +/-40.
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Old 6th March 2013, 08:18 PM   #5
boris81 is offline boris81  United States
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The best way to do it is to find a woofer at the particular size where it's directivity (due to beaming) matches that of the waveguide in the proposed crossover region. You can study this design for reference:

The Seas ER18DXT ported two way

There is considerable variation for woofers' directivity but if I was to give a very general reference (for a 60degree directivity) a 10" driver should cross well to a waveguide around 1kHz, 8" @ 1.5kHz, 6.5" @ 2kHz, 5.5" @ 3kHz, 4" @ 4kHz.

Last edited by boris81; 6th March 2013 at 08:20 PM.
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Old 7th March 2013, 06:03 AM   #6
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It's being mated to a 4" midrange: ACCUTON C79-6
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Old 7th March 2013, 01:36 PM   #7
AllenB is offline AllenB  Australia
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To keep matters flowing, once you decide whether the drivers can be matched, and where (possibly 3k5), then you might go ahead and design a crossover in the usual way. The downward droop with the tweeter response isn't a bad thing regarding why it happens, but you should still straighten it up or maybe leave some of the downward trend if it sounds better.
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Old 7th March 2013, 02:04 PM   #8
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Yeah I'd guess 3.5kHz too.
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Old 7th March 2013, 03:32 PM   #9
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Why use such a small mid Dave? I'd maybe use an 6 or 7" mid. Would look better to.

PS. I'm ryanbouma from TT.
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Old 7th March 2013, 03:55 PM   #10
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Location: Not where whatever I am looking for is at.
Small mids rule in my opinion, but in combination with a waveguide they might not be the perfect solution.
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