Help reverse engineering sim THAM15DS - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 13th August 2015, 03:09 PM   #1
Zwiller is offline Zwiller  United States
diyAudio Member
 
Join Date: Aug 2011
Location: Sandusky, OH
Default Help reverse engineering sim THAM15DS

Looking to increase my understanding of HR. I am pretty comfortable substituting drivers in existing sims but it's time to get outside of my comfort zone. I have become enamored with a particular sim and driver combo. Don Snyder's take on the THAM15 with the PA385-8. Info here: THAM15 - a compact 15" tapped horn

I have contacted Don and he no longer has info relating to this design. I'd like to reverse engineer the sim and take a good look at the design. Although originally designed for the 3015LF, the PA385-8 just looks great in it. The PA385 was not around back then. This could be a classic DIY audio TH cabinet.

To start... Don's HR comment lists dimensions 22.5x24x30. Schematic screen shows system volume of 210.88L/7.7ft3. The above box is 9.38ft3. If I subtract 1.5" from the measurements above, I get 7.4ft3. Interior or exterior measurements? Or maybe there is a better way to start?

HR export attach to those willing to play along. THANKS IN ADVANCE!
Attached Files
File Type: txt THAM15DS.txt (962 Bytes, 74 views)
__________________
_____________________
Sam
  Reply With Quote
Old 6th September 2015, 12:53 AM   #2
tb46 is offline tb46  United States
diyAudio Member
 
Join Date: Jan 2006
Location: Texas
Hi Zwiller,

Ref. (great thread :-) ): THAM15 - a compact 15" tapped horn

I noticed your link in Brian's "Spreadsheet for Folded Horn Layouts..." thread. This looks like some suggestion Don threw out four years ago in the THAM15 thread, and there was no interest/follow-up. The THAM15 is a great thread, but the posted drawing and the Hornresp simulation you found do not quite conform. As I had taken a look at that one before, let me roughly outline some steps that might help in your quest here, and in general:

- do a quick overlay drawing to get the drawing into your favorite drawing package, and scale the drawing to the desired height and depth,

- add the necessary construction lines and the advanced center line as recommended by soho54 (see all the notes by soho54 in THAM15 thread you linked to, e.g.: Post #202-209)

- draw a horn path (development / roll-out) that shows S1 to S5 - L12 to L45 (width and length) as actually in the drawing (see the nice example by xoc1 in the THAM15 thread Post #204)

- get the Hornresp data into a spreadsheet to calculate the horn area width data from the Hornresp data (you can also get all the data from Hornresp - Schematic - File - Export - Horn Data in tabular form)

- transfer the width/length data from the spreadsheet into a development (roll-out) of the horn path in your drawing

You can now compare the development you extracted from the drawing to the development you derived from the Hornresp data in graphical form. And in this case there seems to be quite a difference (it happens :-) ).

Also, I had a development for the original THAM15 (from my drawing, no guarantees) that I also inserted into the drawing. So now we can compare all three developments.

Hope this helps.

Regards,
Attached Images
File Type: jpg THAM15Mod_2015Sep05_spreadsheet.jpg (82.7 KB, 711 views)
Attached Files
File Type: pdf THAM15Mod_2015Sep05_dwg.pdf (38.5 KB, 49 views)
__________________
Oliver
  Reply With Quote
Old 7th September 2015, 05:43 AM   #3
diyAudio Member
 
Join Date: Nov 2007
[Here's a first attempt at something very similar, but not exactly the same. The external dimensions match, and I've rejigged part of the horn to smooth the expansion rate.

Something is still not quite right though, as the spreadsheet predicts at net volume of 199L and the HornResp sim suggests 208 L (it should always be lower than what the spreadsheet predicts).

I'll have another look at it this week if I get the opportunity.
Attached Images
File Type: gif 20150907-SS1.gif (72.5 KB, 680 views)
File Type: gif 20150907-TH1.gif (10.7 KB, 668 views)
File Type: gif 20150907-TH2.gif (19.1 KB, 669 views)
__________________
www.diysubwoofers.org
  Reply With Quote
Old 7th September 2015, 03:33 PM   #4
Zwiller is offline Zwiller  United States
diyAudio Member
 
Join Date: Aug 2011
Location: Sandusky, OH
Many thanks Gents! Seems like you both have come to a similar conclusion that something is amiss. I will continue to study the info presented but it appears the path length is a bit short.

Let me clarify why I am enamored with this design: This design seems to be a very balanced trade off of output for extension. In addition, it is a compact box and cost effective driver. Oh yeah, pretty easy build too... Dons design seems to bridge the gap between the THAM15/SS15 and XOC1/KS designs.
Attached Images
File Type: png THAM15DS.png (55.4 KB, 650 views)
__________________
_____________________
Sam
  Reply With Quote
Old 7th September 2015, 04:27 PM   #5
tb46 is offline tb46  United States
diyAudio Member
 
Join Date: Jan 2006
Location: Texas
Hi Zwiller,

Forsman added a nice wrinkle to the THAM design (I guess we could call it the Forsman loop) that would give you your extra length.

Thorn F1 - a learning experiance with Tapped Horn

Regards,
__________________
Oliver
  Reply With Quote
Old 8th September 2015, 06:11 AM   #6
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by Brian Steele View Post
Something is still not quite right though, as the spreadsheet predicts at net volume of 199L and the HornResp sim suggests 208 L (it should always be lower than what the spreadsheet predicts).

I'll have another look at it this week if I get the opportunity.
I found out where the error was - it turned out to be pretty simple.

Here's the power of the spreadsheet in use - this is a dual-fold THAM15 rejigged to be a decent match for Dayton Audio's PA380 driver. A slight change in the external dimensions and a shift in the internal layout is all that's needed.
Attached Images
File Type: gif 20150908-TH2.gif (73.0 KB, 169 views)
File Type: gif 20150908-TH1.gif (18.4 KB, 150 views)
__________________
www.diysubwoofers.org
  Reply With Quote
Old 8th September 2015, 02:48 PM   #7
Zwiller is offline Zwiller  United States
diyAudio Member
 
Join Date: Aug 2011
Location: Sandusky, OH
Thanks Oliver. Got excited the Forsman used a 12 but the sim with Infinity 1260w disappointed. I will try and sub a few other 12's. That design is busy and full of reflectors, these have been proven unnecessary right?

Brian, my sim does not look like yours. Decent but not as flat and low. I checked my HR inputs a few times.

In any event, you guys are getting me really close to what I am after.
Attached Images
File Type: png THAMBS.png (42.3 KB, 110 views)
__________________
_____________________
Sam
  Reply With Quote
Old 8th September 2015, 06:31 PM   #8
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by Zwiller View Post
Brian, my sim does not look like yours. Decent but not as flat and low. I checked my HR inputs a few times.
Yeah, that's probably because my driver information is different :-). I think I used the PA380 for that sim.

I'll check this afternoon to see if it can be modified to be suitable for the PA385.
__________________
www.diysubwoofers.org
  Reply With Quote
Old 8th September 2015, 06:32 PM   #9
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by Brian Steele View Post
Yeah, that's probably because my driver information is different :-). I think I used the PA380 for that sim.
Oh, and you're not accounting for the volume in front of the cone in your sim.
__________________
www.diysubwoofers.org
  Reply With Quote
Old 9th September 2015, 12:54 AM   #10
diyAudio Member
 
Join Date: Nov 2007
Here's one, using the PA385S driver. I've updated the spreadsheet as well (added some new features, and addressed one minor bug). I'll post the spreadsheet to my "spreadsheets" thread.

Note: the passband of this TH can be flattened even more by reducing S1, but the CR starts being pretty high.

I've also corrected the estimate for the driver's size in the TH
Attached Images
File Type: gif 20150908-TH4.gif (18.3 KB, 133 views)
File Type: gif 20150908-TH5.gif (78.8 KB, 157 views)
__________________
www.diysubwoofers.org
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Reverse engineering to drivers kevinsullivan Multi-Way 21 6th October 2012 04:20 AM
reverse engineering a box Zero Cool Multi-Way 1 16th July 2007 11:00 PM
reverse engineering a crossover? BlackDog Multi-Way 30 9th December 2005 04:01 PM
Svante, a reverse engineering problem sreten Multi-Way 16 4th April 2004 06:38 PM


New To Site? Need Help?

All times are GMT. The time now is 12:19 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright 1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki