Collaborative Tapped horn project - Page 3 - diyAudio
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Old 9th March 2007, 01:08 AM   #21
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Ok, managed to sort out the missing parameters (WinIS pro is also useful for that)

Click the image to open in full size.

It's quite surprising how well the AV12 performs. It is actually more efficient than those larger drivers which would normally have over 10db higher efficiency. Both of the larger pro drivers meet all the recommendations for a driver except they have a large SD and they are very light at around 80g where >200g is recommended for a 12" driver.
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Old 9th March 2007, 01:08 AM   #22
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G'day again Paul

This is one of the better threads I've read for a while!

You should have enough power, but watch your voicecoil. Unless you drive way below cutoff, excursion should not become an issue.

This reminds me of a funny thing that happened the other day. I installed the XXLS drivers, with the help of some adapter rings, into the holes normally filled with the 15LW1401s below the Unitys in my system. (They were in separate sealed boxes of the same internal volume) I was a bothered by some distortion that was present on some tracks at moderate levels. I pulled the XXLS drivers out of their boxes for a visual. They seemed fine. Powering them up with another power amp in free air could not induce the distortion I had heard while the drivers were installed in their boxes. I re-installed the drivers and fired up the system again. Slowly increasing the level until I could just hear the distortion again. At that point I headed down stairs to have a look at the level meters on the AM1600 that was powering this pair of drivers. It's probably an understatement to say I was a little shocked to discover the amp was being driven into clipping! 800WRMS into each of these poor 12" drivers. I'm so used to very efficient speakers that this outrageous consumption of power took me completely by surprise! Had I ever driven the 15LW1401s to even 100W each, I'd have been blowing my head off. Needless to say I am delighted with the low distortion at high drive levels that these XXLS drivers show. There was not a hint of distress to just short of 1KW per driver, then it was the amp that went ugly.

AJ

Didn't measure GD. Should have but didn't reverse a driver. The sub was still very clean.

Cheers

William Cowan
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Old 9th March 2007, 01:22 AM   #23
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William, I'm a twit! I was trying to come up with a way to mount drivers push pull, and didn't think of the simple solution you used there with just one driver reversed!

If this does get beyond prototype, then I'll either build two installed under the floor, or one with push pull drivers. The beauty of this is that I can put them anywhere in the room (almost), hence have the freedom to get the best room interaction. Of course, the beauty of push pull is that it's possible to mount them so that their forces also cancel, which is welcomed in a box of this size - anything to keep vibration down without having to brace, make the box thicker and use more expensive materials. The difficulty is getting that to work with this type of box - a bit complex to pull it off, and quite awkward. I need to find out first if it's worthwhile.

What sorts of dimensions do you have with that XXLS tapped horn?

Have you by any chance tried it with push pull?

Do you know what the efficiency with 1w is? Hornresp seems to show very high efficiency.

I'm also curious to know if you have been able to trick hornresp into modelling something like what you actually measure?
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Old 9th March 2007, 02:07 AM   #24
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G'day again Paul

That horn is XLS, 830500. The XXLS drivers are in sealed boxes in my Unity system at the moment (covering 20-300Hz). I will try them in the 30Hz tapped horn some time in the next few weeks (Pending time) The timber in the big horn has since gone into other projects.

Reversing one of the drivers in the dual driver horn will not give a reduction of vibration. It will only serve to reduce even order distortion products. I guess you'd need to do a one up two back type deal to put the drivers in a clamshell front to back type arrangement.

The different tapped horns I measured were between 95 and 100dB/W/M.

No luck with an accurate model in Horn Response, but the guesstimates give you a pretty good idea.

Outside dimensions of the big tapped horn are 2250 by 450 by 515. All material is 25mm. Taper is shallow, under 1.5:1.

Cheers

William Cowan
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Old 9th March 2007, 02:25 AM   #25
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When I mentioned the more complicated push pull I meant a clamshell labhorn type mounting, except with one driver inverted, hence as you know, reduced distortion and vibration. As you can imagine, much more complex to build. If I go beyond prototype then I'll see if I can come up with something along those lines.

Did you form any conclusions when it comes to throat to mouth ratios and compression ratios?

Did you discover any particular and significant impact of changing throat to mouth ratio?

Did you find that 25mm ply is adequate without bracing?
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Old 9th March 2007, 02:31 AM   #26
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G'day again

One path up, two back or the other way around will give you an easy to build clam shell.

#2 Umm...See below
#3 Yep, Hornresponse will show the changes I saw.
#4 Yep, for testing at least. (The pressure didn't rip any boxes apart, and the panels did not vibrate too much)

Cheers

Wiliam Cowan
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Old 9th March 2007, 02:59 AM   #27
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Quote:
One path up, two back or the other way around will give you an easy to build clam shell.
Could you elaborate, I don't quite follow!
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Old 9th March 2007, 03:15 AM   #28
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The bottom left and right corners are the mouths. You could reverse the whole thing for a mouth in the middle. This arrangement reduces even order distortion products and cancels mechanical vibration.
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Old 9th March 2007, 04:18 AM   #29
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Ahhhhh, I get it now. Yours is perhaps a little simpler than my idea of how to do it:

Click the image to open in full size.

I think I like your version better.
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Old 9th March 2007, 04:36 AM   #30
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Paul

Your drawing is better.

Since this is a new idea, perhaps I should patent it!?$

My design just requires one more internal baffle, which adds bracing. External size is only increased by the thickness of that baffle (25mm). A horizontal brace between the two drivers would probably help.

During the free air testing of the XXLS driver I thought had failed, I had it sitting on it's magnet and playing high level sinewave through it. The driver was almost bouncing off the floor! The carpet has a 9mm or so pile and the driver frame was moving up and down about 6mm at times. Cancelling vibration between opposing drivers has got to help.

Have a good weekend.

Cheers

William Cowan
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