Good 8" drivers for Tapped horns with long path lengths? - Page 3 - diyAudio
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Old 14th February 2014, 01:43 AM   #21
sine143 is offline sine143  United States
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I know you know a lot more than me brian, so please dont take anything I'm saying the wrong way, its your knowledge and a that of a number of others here thats basically taught me anything.

as far as the resonances go, one of the most well regarded DIY low tuned THs available in these parts (gjallerhorn) displays the same problems, with 3 peaks almost 10 db up from passband average (the lowest being at 65 hz, WAY in the passband).

Gjallerhorn

Click the image to open in full size.

the TH Spud itself displays a similar, 10 db jump, starting at 75hz and continuing above 110 hz.

Dual 8" tapped horn = TH-SPUD

Click the image to open in full size.

So I dont see how this is a major design flaw? I actually tried to design it to push the spikes outside of the passband (instead of inside around 70 to 80 like seen in those 2 examples.
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Old 14th February 2014, 05:22 AM   #22
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Originally Posted by sine143 View Post
So I dont see how this is a major design flaw? I actually tried to design it to push the spikes outside of the passband (instead of inside around 70 to 80 like seen in those 2 examples.
I didn't say it was a "design flaw". I said that it would need quite a bit of processing to deal with it. e.g. a simple 12dB/oct low-pass filter may not be enough to get the best results.
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Old 14th February 2014, 05:02 PM   #23
sine143 is offline sine143  United States
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oh, I wouldn use anything wiith less than 24 db/oct slope. LR filter willhelp take down some of the peaks at xover point ast well.
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Old 14th February 2014, 08:18 PM   #24
JLH is offline JLH  United States
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Originally Posted by sine143 View Post
thanks for that link TB (sorry, my six key doesnt work so I'll never be able to spell your name out lol). I've been looking for it.

The THspud seems to dig a bit lower than I need, and is about 375 liters for 2 8s, I'd like to stuff 4 8s in that space if possible. I realize I'll likely only be able to get response down to about 20 to 25hz rather than the 15 or so hz the spud goes to. It has like a six hundred and 20 cm path length, about 150 more cm than I think I am really willing to go.

I dont think I can beat the spud, but then again i'm not trying to compete with it ;p

GM, I missed your second post. checking it out now!!!!
Try this. It is a smaller TH-Spud style horn that still uses two Tang Band W8-740 drivers. An Erse 3.6mH coil helps flatten the response out.
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Old 14th February 2014, 11:28 PM   #25
sine143 is offline sine143  United States
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Oliver, the JBL gto804 seems good in your 140 liter design, capable of another 4db output (digs a tiny bit deeper too). a tiny bit smoother as well.
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Old 16th February 2014, 01:38 PM   #26
JLH is offline JLH  United States
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Originally Posted by JLH View Post
Try this. It is a smaller TH-Spud style horn that still uses two Tang Band W8-740 drivers. An Erse 3.6mH coil helps flatten the response out.
I worked out the folding for this horn. A few things changed due to practical considerations and fitment requirements. The resulting Horn Response parameters reflect the required changes. The exterior dimensions are 11 5/16" (28.7cm) deep X 27" (68.7cm) wide X 38" (96.3cm) tall. Total folded volume is 6.7 cu. ft. or 189.86 liters. I think this is a lot of horn in a pretty reasonable sized package. Panel thickness used is 19mm or . An Erse 3.6mH coil is added and the Tang Band W8-740 woofers are wired in series for an 8 ohm load. An amplifier capable of 500Wrms into 8 ohms should be more than enough. Its Max SPL level well exceeds THX standards. I'm seriously considerenig building a pair of these once the weather clears up.
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Old 16th February 2014, 02:02 PM   #27
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Originally Posted by JLH View Post
I worked out the folding for this horn. A few things changed due to practical considerations and fitment requirements. The resulting Horn Response parameters reflect the required changes. The exterior dimensions are 11 5/16" (28.7cm) deep X 27" (68.7cm) wide X 38" (96.3cm) tall. Total folded volume is 6.7 cu. ft. or 189.86 liters. I think this is a lot of horn in a pretty reasonable sized package. Panel thickness used is 19mm or . An Erse 3.6mH coil is added and the Tang Band W8-740 woofers are wired in series for an 8 ohm load. An amplifier capable of 500Wrms into 8 ohms should be more than enough. Its Max SPL level well exceeds THX standards. I'm seriously considerenig building a pair of these once the weather clears up.
Switch the expansion from "CON" to "PAR" for a more accurate sim of a horn folded up into a rectangular box.
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Old 16th February 2014, 05:03 PM   #28
JLH is offline JLH  United States
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Originally Posted by Brian Steele View Post
Switch the expansion from "CON" to "PAR" for a more accurate sim of a horn folded up into a rectangular box.
I tried your suggestion. It virtually made no difference. I can barely see the difference when I do the "compare previous" command. Historically, my Horn Response predictions have measured very close using Conical sections for the simulation. Is there a significant reason for your suggestion? Did I miss a conversation somewhere?
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Old 16th February 2014, 05:28 PM   #29
sine143 is offline sine143  United States
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JLH, your sim is nice (very flat), but it seems to have VERY similar output capabilities to a half of the sime I posted on page one (Good 8" drivers for Tapped horns with long path lengths? (I posted a 4 driver design, by showing graphs of 2 2p designs in 2S).

They are withing about 1 db of each other if both are graphed in 1 pi, and are the same size (140 liters pre fold).

the conical vs Par thing might be more relevant when working with a larger horn.

Last edited by sine143; 16th February 2014 at 05:30 PM.
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Old 16th February 2014, 06:01 PM   #30
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Is there a significant reason for your suggestion? Did I miss a conversation somewhere?
Expansion in a horn which has two parallel sides (basically almost every horn folded into a rectangular enclosure) is parabolic, not conical. A search for "parabolic" on this forum should turn up the message threads where this has been discussed.
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