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Multi-Way Conventional loudspeakers with crossovers

The POOR man's Tannoy DMT - AKA "The PM-DMT"
The POOR man's Tannoy DMT - AKA "The PM-DMT"
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Old 18th August 2018, 10:40 AM   #41
wae is offline wae  Netherlands
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Default 12" TL version design for the PM-DMT

As previously discussed, it would be nice to have a 2x Transmission Line LF.

Here is a nice start with a Dayton LS12-44, which has a flat cone, comes at around 140 Euro's, sexy..

Apart from being sexy, it appears to love TL's. +-3 dB point is around 25 Hz in a cabinet with internal dimensions of 76 High, 57 Deep and 35 wide (centimetres that is).

I used Leonards TL software. Also, to figure out where the damping needs to go, I slice up the TL, so to be able to find those places by adding High damping as a check. That way you can see the effect in the Freq. response and xmax. Typically, I find that there a 3 (almost obvious) spots which require some kind of damping.

- The closed end of the TL (works for almost the entire spectrum).
- Right around the driver (tame the low-mid 1e order? dip, which is also controlled by off-setting the driver)
- In the last segment at the open end of the TL, control the high end of the spectrum).


kind regards.
Attached Images
File Type: jpeg Dayton LS12-44 displacement.jpeg (190.5 KB, 192 views)
File Type: jpeg Dayton LS12-44 freq-resp.jpeg (200.1 KB, 193 views)
File Type: jpeg Dayton LS12-44 TL-config.jpeg (98.7 KB, 188 views)
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Last edited by wae; 18th August 2018 at 10:45 AM.
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Old 19th August 2018, 01:07 PM   #42
wae is offline wae  Netherlands
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Default Damping a TL with Leonard software (as a start)

Quote:
Originally Posted by wae View Post
Typically, I find that there a 3 (almost obvious) spots which require some kind of damping.

- The closed end of the TL (works for almost the entire spectrum).
- Right around the driver (tame the low-mid 1e order? dip, which is also controlled by off-setting the driver)
- In the last segment at the open end of the TL, control the high end of the spectrum).


kind regards.
I guess that should be "at least 3 spots...". To be completely honest, I still have to build my first TL, which as I understand will improve my panel fixing skills by a nice margin. It would take a lot of adding / changing and removing damping material while listening and measuring. Construction of the test TL so that one side panel can be screwed on and off a lot of times without leaking.

Just hoped that by doing it as described in my previous post. If we can design a TL with this software and take our trust in it, why would applying damping material with the same software be WAY off. So, as a start I currently trust the software and therefore the damping starting point.

Question will always be, HOW does it SOUND. Most likely, we could damp all the live out of the TL and still have a nice graph. So testing and measuring comes in as a must.

What I did here is apply the bare minimum and have the SPL level as least influenced as possible. Assuming that this would keep the TL alive...

I added 3 frequency graphs to show the different effects;

- First graph with NO damping in the last (open ended) segment
- Second graph with NO damping around the driver
- Third graph with NO damping at the closed end of the TL

Look at the SPL level in the effective area we want to use (25 - 250 Hz). The damping at the closed end impacts the SPL mostly.

comments / corrections always welcome.

kind regards.
Attached Images
File Type: jpeg no damping at open end.jpeg (123.1 KB, 168 views)
File Type: jpeg No damping around driver.jpeg (121.1 KB, 163 views)
File Type: jpeg NO damping at clsed end.jpeg (123.4 KB, 15 views)
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Old 19th August 2018, 01:46 PM   #43
wae is offline wae  Netherlands
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Default The TL design squeezed into a cabinet

Next, I made a sketch of the cabinet that is to hold this design.

Personally I like this 2 fold, 3 element version. It is very simple to put in to a cabinet.

Looking at the picture I added of the TL design;

The second element will be 180 degrees turned and placed against the first element. The third element goes against the bottom of the first and second element. Both the first and second element have the same length. The length of the third element is the sum of the closed end size (a) and the smallest side of the second element (b) and the thickness of one panel (18mm).

Note: the dotted line can be ignored, it's a slice of the first element that I used to determine if another damping spot was required. With the Leonard software, you can split an element. You get an new element within the existing element so to speak which you can move around and change in size. Adding damping to this slice shows the effect on the frequency graph.

Second picture is the design, in this case still with a separate MF and HF driver. For our PM-DMT, we need to put hold of the closed cabinet for the coaxial into this design. It's about 3 litres, so not a big deal.

Note: Sizes could be in-accurate, have to do a final calc.


kind regards.
Attached Images
File Type: jpeg Dayton LS12-44 TL-config.jpeg (108.9 KB, 28 views)
File Type: jpg WAE-TL12-DaytonLS12-44-v2-WAE-Style.jpg (55.1 KB, 41 views)
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Old 19th August 2018, 02:04 PM   #44
wae is offline wae  Netherlands
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Quote:
Originally Posted by wae View Post

Here is a nice start with a Dayton LS12-44, which has a flat cone, comes at around 140 Euro's, sexy..
This is the Dayton LS12-44. Something different

kind regards.
Attached Images
File Type: jpg Dayton LS12-44-front.jpg (347.3 KB, 52 views)
File Type: jpg Dayton LS12-44-back.jpg (63.7 KB, 28 views)
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Old 19th August 2018, 02:21 PM   #45
wae is offline wae  Netherlands
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Quote:
Originally Posted by tmuikku View Post
Speaking of which there are some very modern coaxial speakers such as Geithains and Genelec the Ones for inspiration
Thanks, looking into the generic's, what's "behind" slot panel? Hhmmm

kind regards.
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Old 19th August 2018, 02:29 PM   #46
tmuikku is offline tmuikku  Finland
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Quote:
Originally Posted by wae View Post
Thanks, looking into the generic's, what's "behind" slot panel? Hhmmm

kind regards.
Genelec has some public papers on the design with photos, remember reading them some time ago. there are oval shaped woofers top and bottom behind the slots. I don't find them now though... here is one paper on it Magazine Articles | Genelec.com

some more info Acoustically Concealed Woofers (ACW™) Technology | Genelec.com

Last edited by tmuikku; 19th August 2018 at 02:44 PM.
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Old 19th August 2018, 02:39 PM   #47
Charles Darwin is offline Charles Darwin  United Kingdom
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Just the one 12" per side then?
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Old 19th August 2018, 02:48 PM   #48
maxlorenz is offline maxlorenz  Chile
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Quote:
I guess that should be "at least 3 spots...". To be completely honest, I still have to build my first TL, which as I understand will improve my panel fixing skills by a nice margin. It would take a lot of adding / changing and removing damping material while listening and measuring. Construction of the test TL so that one side panel can be screwed on and off a lot of times without leaking.
I say: go for it.
Make the first with cheap MDF and few screws to test damping. I'd go from no damping to full damping and backwards. With such a simple box (I expected more convolutions and lenght ) it shall be easy.

My own first attempt (no software used ) was transforming some cheap Aywa little surround speakers (3,5" woofer) into test speakers with an 83 X 40cm PCM-like box. The total length of TL is around 2,8m. Obviously, they are not perfect, but they serve its purpose and produce some articulate bass.

Have fun,
M.
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Old 19th August 2018, 03:52 PM   #49
wae is offline wae  Netherlands
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Quote:
Originally Posted by tmuikku View Post
Genelec has some public papers on the design with photos, remember reading them some time ago. there are oval shaped woofers top and bottom behind the slots. I don't find them now though... here is one paper on it Magazine Articles | Genelec.com

some more info Acoustically Concealed Woofers (ACW) Technology | Genelec.com
THANKS!
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Old 19th August 2018, 03:55 PM   #50
wae is offline wae  Netherlands
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Quote:
Originally Posted by Charles Darwin View Post
Just the one 12" per side then?
Well, as a starter to see if I can handle this.

I'm shure it will be a series 10" 12" (15") single with a coax and same with 2x LF, for the bigger bang so the speak

kind regards.
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