LIVE SOUND Specific Tapped Horn thread... - Page 54 - diyAudio
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Old 16th May 2009, 07:11 AM   #531
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Quote:
Originally posted by screamersusa
The test cabinet had no bracing at all. 102-103db at 40hz.
How did you take measurements? I am in South Florida and I'd like to see how my modified Labs compare to your tapped horn.
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Old 16th May 2009, 01:35 PM   #532
jbell is offline jbell  United States
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Thanks oliver for the drawing of scott's sub. I think I have a guesstimate why he has a winner. When he 'eliminated' the reflector at the upper front part of the cabinet, he said he got +3db at 100hz, vs with it. That 100hz is right in the 'valley' and would make this sub flat from 45hz on up, just like scott measured.

There must be a box resonance going on that hornresp isn't predicting, due to the folding, and scott 'stumbled' on a winner of a design. I know TD says you can't 'stumble' on these alignments, but I think scott got close.

My hat's off to you scott... you 'found' something by trial and testing, not by software.
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Old 16th May 2009, 02:28 PM   #533
tb46 is offline tb46  United States
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Default Posts #519 / #529

Hi fb,

Here is another take on building a tapped horn for the AV12H to your specs in Post #519. This one models well CON and EXP. Seeing the difference in response between screamerusa's measured results and the Hornresp model, I'd use OSB for a trial run. :-)

Regards,
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Old 16th May 2009, 03:05 PM   #534
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TB46....wow that was quick. Thanks.
You pretty much nailed it. I added the angle changes to the first two reflectors.
I was looking at some fluid dynamics sims and remembering some basic room acoustic issues and applied that to how the reflectors were done.
While it was not built directly from a hornresp sim, all those failures with computer aided sims gave me the "Feel" to try winging it a couple of times. I'd say a controlled "stumble" would be pretty accurate.
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Old 16th May 2009, 04:31 PM   #535
tb46 is offline tb46  United States
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Default FurySub_2009

Hi screamerusa,

On your revision is that 12 degrees for both angle pieces, and is the opening 15x29cm? The resolution is just not quite good enough for me to read.

What do you think about jbell's suggestion (Post #532), that removing the internal reflector resulted in filling in the first response dip, and if so, have you tried removing the 'upper left hand' reflector (squaring the outside corner)?

It's definitely quite an achievement to get this close by modifying the enclosure "life".

Regards,
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Old 16th May 2009, 05:10 PM   #536
tb46 is offline tb46  United States
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Default FurySub_2009

Hi screamerusa,

Just some questions/suggestions:
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Old 16th May 2009, 05:19 PM   #537
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Default Re: FurySub_2009

Quote:
Originally posted by tb46
On your revision is that 12 degrees for both angle pieces, and is the opening 15x29cm? The resolution is just not quite good enough for me to read.
One side of each piece is cut at about a 12 degree angle, yes.
15x29cm is the original opening, correct.
I will do some rechecking in a couple of days as this is my bust part of the week. The drawing looks spot on.

Removing the other reflectors all yielded unacceptable dips and losses.
The one "missing" reflector was my insane atempt to "cut" the path length and create a higher spl "Bounce" affecting the 100hz area as I was not getting ANY gain over the direct radiator.
Please remember that the goal was not to build the best tapped horn live sub (That's Tom's job), but to match or exceed a double driver cabinet to eliminate the amount of amps and wall power required to achieve high quality high spl with a 2.6ohm minimum load (3 drivers).. Smooth response at about 102-103 db from 38-125hz would be a realistic goal, for a single

You should see the shocked looks from the "know it all's" around here when they find out I'm only pushing about 5,500 watts on the mains. Except for one moron who insists I HAVE to buy 4 of his double 18 JBLs, not one engineer or bs artist looking for a quick sale, has had anything but praise for the 4 subs I'm using.
That tells me we have something here that is worth refining.


Edit: Hmm. that's interesting. No the reduction was not intentional. Glad someone else noticed it. It does look like
some of the geometry could be altered a bit. to smooth out
the back angles without causing any problems.
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Old 16th May 2009, 05:24 PM   #538
tb46 is offline tb46  United States
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Hi scremerusa,

That kind of practical feedback is priceless.

Regards,
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Old 16th May 2009, 05:33 PM   #539
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I think figuring out what made the core section work is probably the key to improving the whole cab.
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Old 17th May 2009, 03:01 AM   #540
jbell is offline jbell  United States
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3 questions, that I don't think we have, or can easily get answers to:

1. why does the angled part from s1 to s2 matter so much? hornresp doesn't show appreciable change with modifications to this part of the horn.

2. Why does removing the one reflector add +3db at 100hz? hornresp doesn't have any way to model with or without it.

3. Why does a solid rear brace diminish output down low (40-50hz, I'm guessing)

It would appear that there are MANY more acoustic interactions happening, than what geddes would call: "lumped masses"

Somehow, what I 'thought' I knew about TH, seems to be slipping away from me, and I'm realizing just how much I don't know about these beasts.
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