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Dag Johansen 15th June 2011 07:02 PM

40Hz TH
 
3 Attachment(s)
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

epa 15th June 2011 07:29 PM

nice job:)
good carpenter work.
(it would be nice to have an extra step in hornresp.)

weltersys 15th June 2011 09:15 PM

Quote:

Originally Posted by Dag Johansen (Post 2606932)
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.

Dag Johansen 16th June 2011 04:38 AM

Quote:

Originally Posted by weltersys (Post 2607075)
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

tb46 16th June 2011 02:42 PM

Hornresp model
 
1 Attachment(s)
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:

http://www.diyaudio.com/forums/subwo...ml#post2451737

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

Regards,

Dag Johansen 16th June 2011 03:01 PM

2 Attachment(s)
Quote:

Originally Posted by tb46 (Post 2607948)

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:

tb46 16th June 2011 04:24 PM

1 Attachment(s)
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:

http://www.diyaudio.com/forums/subwo...thread-54.html

Regards,

Djim 16th June 2011 05:28 PM

Quote:

Originally Posted by tb46 (Post 2608073)
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.

Dag Johansen 16th June 2011 06:19 PM

3 Attachment(s)
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

Brian Steele 17th June 2011 01:25 AM

Quote:

Originally Posted by Dag Johansen (Post 2608232)
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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