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Old 15th June 2011, 07:02 PM   #1
diyAudio Member
 
Join Date: May 2007
Default 40Hz TH

Hi.
I love to read about all the projects on this forum.
I have build some speakers trough many years and i would like to share my latest project with you.
Goal: reasonably flat down to 35Hz, minimum 100dB @ 40Hz/2,83v 2pi.
Easy to move around, DJ use.
I will build 4pc first.
There are many 15inch speakers that simulate well, RCF 15NW100, Beyma 15P1000/1200/1300ND, Faital 15HP1060 etc.
I have some brand new Eminence 3015LF on my shelf, but they seem to do the job best in lower compression ratios.
There is one part i am unsure how will affect the result:
After the first bend there is a slight negative tapper towards the second bend...
Any idea?
As a result of that i am not sure how to acuratly simulate the horn, maybe i schould give AKBAK one more try...
Hornresp input will follow.

Dag
Attached Images
File Type: jpg 15062011141.jpg (551.9 KB, 2728 views)
File Type: jpg 15062011142.jpg (617.9 KB, 2525 views)
File Type: jpg 15062011144.jpg (696.5 KB, 2321 views)
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Old 15th June 2011, 07:29 PM   #2
epa is offline epa  Netherlands
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Location: amsterdam
nice job
good carpenter work.
(it would be nice to have an extra step in hornresp.)
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Old 15th June 2011, 09:15 PM   #3
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Join Date: Jan 2008
Quote:
Originally Posted by Dag Johansen View Post
Hi.
I love to read about all the projects on this forum.
I have build some speakers trough many years and i would like to share my latest project with you.
Goal: reasonably flat down to 35Hz, minimum 100dB @ 40Hz/2,83v 2pi.
Easy to move around, DJ use.
I will build 4pc first.
There are many 15inch speakers that simulate well, RCF 15NW100, Beyma 15P1000/1200/1300ND, Faital 15HP1060 etc.
I have some brand new Eminence 3015LF on my shelf, but they seem to do the job best in lower compression ratios.
There is one part i am unsure how will affect the result:
After the first bend there is a slight negative tapper towards the second bend...
Any idea?
As a result of that i am not sure how to acuratly simulate the horn, maybe i schould give AKBAK one more try...
Hornresp input will follow.

Dag
Looks good!
Why bother simulating something you have already built?
That will tell if you met your goals, sims don't.
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Old 16th June 2011, 04:38 AM   #4
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Join Date: May 2007
Quote:
Originally Posted by weltersys View Post
Looks good!
Why bother simulating something you have already built?
That will tell if you met your goals, sims don't.
I have simulated it, but i am not sure what to "call" the S2 > S3.
It seem to to be midway between CON and EXP looking at the schematic liters.

Dag
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Old 16th June 2011, 02:42 PM   #5
tb46 is offline tb46  United States
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Location: Texas
Default Hornresp model

Hi Dag,

For a 4-section simulation in Hornresp S1/S2/S4/S5 are defined by the box construction and the loudspeaker location. To find the location for S3 you almost have to draw a roll-out of the horn path, and find the point where S3 best matches the horn shape. Soho54 provided quite a few nice examples, here is one:

THAM15 - a compact 15" tapped horn

As to the flare, somebody calculated, that for hornpath with parallel sides, as in tapped horns, PAR is normally the correct flare.

Regards,
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File Type: jpg TH_inside_side view_area_locations_15062011144.jpg (41.9 KB, 2106 views)
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Old 16th June 2011, 03:01 PM   #6
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Quote:
Originally Posted by tb46 View Post

As to the flare, somebody calculated, that for hornpath with parallel sides, as in tapped horns, PAR is normally the correct flare.

Regards,
I think PAR is only right when paralell walls are used and the expantion is with 90 degrees bends!?
In my horns it expands a little more.
In liters it ads up between CON and EXP.
But i will try to simulate with four segments.
Here is how i calculated 3 segments:
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File Type: jpg Hornresp input.JPG (51.9 KB, 2003 views)
File Type: jpg spl.JPG (43.2 KB, 542 views)
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Old 16th June 2011, 04:24 PM   #7
tb46 is offline tb46  United States
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Location: Texas
Hi Dag,

Your design really looks nice, it reminds me a bit of screamerusa's Furysub, he empirically arrived at a number of non-obvious reflectors/angles/locations (e.g.: particularly at not putting a reflector into the upper front of the cabinet). He also added a board from S1 to S2 to reduce the S1 area. It may be something to keep in mind for modifications and another build:

LIVE SOUND Specific Tapped Horn thread...

Regards,
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Old 16th June 2011, 05:28 PM   #8
Djim is offline Djim  Netherlands
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Location: 'Ollanda
Quote:
Originally Posted by tb46 View Post
Hi Dag,

Your design really looks nice, it reminds me a bit of screamerusa's Furysub, he empirically arrived at a number of non-obvious reflectors/angles/locations (e.g.: particularly at not putting a reflector into the upper front of the cabinet). He also added a board from S1 to S2 to reduce the S1 area. It may be something to keep in mind for modifications and another build:
Hi Oliver, I think in this case the upper front could maybe benifit from a corner correction. I noticed when two horn path section of near same length they can benefit from corner correction and when two path sections have an 1/3, 2/3, 4/3 ect relation you need to be careful.
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Old 16th June 2011, 06:19 PM   #9
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Join Date: May 2007
Thanks for all the input and sugestions! :-)
Four segment simulation with Eminence 3015LF (i know- i know, but that is the only 15 inch driver at hand now)
Made a quick impedance meassurement and its not exactly spot on...
The height of the peaks is one thing, another is the first peak which are some 6Hz higher than predicted by Hornresp.
Hm...
As of reflector plate, i will try it in the second to last bend.
But first i have to decide on which speaker i am going to use.... decisions decitions! :-)

Dag
Attached Images
File Type: jpg 3050LF.JPG (48.5 KB, 325 views)
File Type: jpg 3015LF impedance.JPG (36.3 KB, 199 views)
File Type: jpg TH impedance.jpg (90.3 KB, 256 views)
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Old 17th June 2011, 01:25 AM   #10
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Join Date: Nov 2007
Quote:
Originally Posted by Dag Johansen View Post
The height of the peaks is one thing, another is the first peak which are some 6Hz higher than predicted by Hornresp.
The shape and location of the first peak suggests that (1) the horn is a bit shorter than the sim (how did you measure its length?), and (2) you might have some leakage around or near the driver.
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