TH-18 Flat to 35hz! (Xoc1's design) - Page 11 - diyAudio
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Old 15th June 2011, 08:47 PM   #101
jbell is offline jbell  United States
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been away... I see the cat's been playin....
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Old 15th June 2011, 08:53 PM   #102
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i've tried to sim the peavey 18" lowrider and it looked pretty similar to the P Audio CB18-650EL. course i am just learning hornresp and there is a good chance i have no idea what i am looking at. however, best way to learn is to do it......now in the states, the P Audio driver is on sale for $156 (overstock item), the peavey 18" lowrider can be had for $184.
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Old 15th June 2011, 08:55 PM   #103
Djim is offline Djim  Netherlands
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Originally Posted by scameron78 View Post
i've tried to sim the peavey 18" lowrider and it looked pretty similar to the P Audio CB18-650EL. course i am just learning hornresp and there is a good chance i have no idea what i am looking at. however, best way to learn is to do it......now in the states, the P Audio driver is on sale for $156 (overstock item), the peavey 18" lowrider can be had for $184.
Look at the group delay response in HornResp and you'll see the difference and I can assure you the impulse behaviour in reality is another issue.
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Old 15th June 2011, 08:59 PM   #104
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Look at the group delay response in HornResp and you'll see the difference and I can assure you the impulse behaviour in reality is another issue.
i'm getting ready to head out for the evening. i will have some questions for you tomorrow i'm sure. i have the CNC programs written to cut out the uprights for the TH-18. just gotta get the guy that operates the machine to run my programs.
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Old 15th June 2011, 09:07 PM   #105
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Since this design is the same fold that I originally came up with for the ss15.... should that make me go hmmm?????
Jim,

I don't know what makes you hmmm????

The Apache, SS15, Fury sub all have similarities to the DSL TH-115/118 which they all emulate to some degree.

Martin's plan happens to be even more similar to the DSL TH-115/118 .

My BC18SW125-4 loaded (like the current TH-118) Keystone uses a different fold pattern entirely, but similar path length and cabinet volume, and has very similar frequency and phase response to the DSL TH-118.

I had hoped that would happen .

Art
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Old 15th June 2011, 09:44 PM   #106
Xoc1 is online now Xoc1  United Kingdom
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I don’t get a lot of time to keep up with this thread - and this thread is taking up a lot of my time... Never less I still consider this design as work in progress, and I sure that it could be improved on.

At the moment I am considering the bracing of the cabinet.
It would be nice to be able to use the spare material from the cut sheets to brace the cabinet. I am a little unsure how using 18mm wide material would affect the performance of the speaker.
It occurred to me that the bracing should be angled to the horn path within the speaker to reduce the cross sectional area reduction at any given point.
Also I have tried to connect the strongest points of the speaker to the weakest points.
Is this bracing to thin for the material? The ribs as shown are 18 x 30 typically.
I will probably add some more bracing yet – but thought I would post this for some feedback
Regards
Martin
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File Type: jpg TH18 Brace Proposal.jpg (359.9 KB, 1215 views)
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Old 15th June 2011, 10:50 PM   #107
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Originally Posted by Xoc1 View Post
Is this bracing to thin for the material? The ribs as shown are 18 x 30 typically.
I will probably add some more bracing yet – but thought I would post this for some feedback
Regards
Martin
Your proposed bracing is more than adequate, cut off strips in triangles are very effective.
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Old 16th June 2011, 12:26 AM   #108
Djim is offline Djim  Netherlands
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Martin, with bracing you have 3 different issues;

Suppression of resonances in the panels (can be achieved with relative thin braces).
Suppression of deformation of panels under the pressure of large and intensive sound waves (needs much stronger braces such like the bottom brace).
Structural reinforcements to make the cab resistant to (extreme) external forces from accidental drops and transport. For example small square braces behind the wheel attachments are no luxury, I think.

But somehow I believe you can teach us more about structural reinforcements and how panel thickness works in relation to brace thickness and their position to endure forces from all sides . The enlarging of the first brace section to 81mm is roughly based on its angle and the total surface of the bottom panel. Oh, I made a small correction (suggestion) in the back where the braces are 'attached' to their vertical brace.
Click the image to open in full size.

I know the force from the front brace at the bottom is the extension of it in your suggestion but I'm worried more about the back panel to be honest. Wondering if you can model all these things more precisely, if you ever find the time to do these things…
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File Type: jpg Bracing02.jpg (124.4 KB, 2102 views)

Last edited by Djim; 16th June 2011 at 12:39 AM.
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Old 16th June 2011, 01:31 AM   #109
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I like all the ideas and effort put into this design! I have been busy with work and doing motor swaps so I haven't had spare time to grab the wood and start building theses. Soon soon
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Old 16th June 2011, 03:42 AM   #110
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Originally Posted by Djim View Post
??? Did you miss something ??? Or did I miss something ???
What do you mean?

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Originally Posted by m R g S r View Post
I have been busy with work and doing motor swaps
What engines are you swapping? What chassis?

Last edited by CRESCENDO; 16th June 2011 at 03:43 AM. Reason: Quote #2
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