Single sheet TH challenge - Page 129 - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers

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 7th January 2012, 01:19 AM   #1281
diyAudio Member
 
Join Date: Jun 2007
Quote:
Originally Posted by weltersys View Post
If there are any other tests you would like to see done to help in confirmation of any changes you decide to implement in Hornresp, don’t hesitate to PM me.
Hi Art,

Excellent - many thanks.

The two things that continue to puzzle me are:

1. Why your test results and now those of Wayne, show only a 6 dB gain at low frequencies rather than a 9 dB gain (my previous post refers) - particularly since you indicated in an earlier post that the combined response of multiple front loaded horns is extended downwards in frequency (if I understand correctly).

2. Why the response of multiple tapped horns is not extended downwards, similar to the front loaded horns you compared them against.

Kind regards,

David
__________________
www.hornresp.net
  Reply With Quote
Old 7th January 2012, 01:23 AM   #1282
diyAudio Member
 
Join Date: Jun 2007
Quote:
Originally Posted by Wayne Parham View Post
Some sample datasets can be seen here:
Hi Wayne,

Many thanks for this - every little bit helps :-).

Kind regards,

David
__________________
www.hornresp.net
  Reply With Quote
Old 7th January 2012, 01:38 AM   #1283
diyAudio Member
 
Join Date: Jun 2007
Quote:
Originally Posted by Wayne Parham View Post
Hmm, I dunno. The measurement distance was 10 meters (32.8 feet or 393 inches) and the center-to-center distance between subs standing side-by-side is around two feet, even the largest models. That means each was about 2° off-axis. I'm pretty sure the difference between 0° and 2° is negligible, not even measurable.
Hi Wayne,

Perhaps at the higher frequencies the two signals being combined are no longer completely coherent or correlated?

10 metres is quite a distance, particularly if there happens to be any movement in the air. Also, the two diaphragms may no longer be acting together as rigid pistons, with independent resonance modes starting to develop depending upon the slightly different physical properties of each driver.

Just a thought... :-).

Kind regards,

David
__________________
www.hornresp.net
  Reply With Quote
Old 7th January 2012, 01:42 AM   #1284
diyAudio Member
 
Join Date: Jun 2007
Quote:
Originally Posted by weltersys View Post
Cool, will this have an effect on the simulated LF response of multiple TH ?
Hi Art,

Not unless I make a special adjustment, just for multiple tapped horns :-).

Kind regards,

David
__________________
www.hornresp.net
  Reply With Quote
Old 7th January 2012, 01:59 AM   #1285
diyAudio Member
 
Wayne Parham's Avatar
 
Join Date: Feb 2004
Quote:
Originally Posted by David McBean View Post
Perhaps at the higher frequencies the two signals being combined are no longer completely coherent or correlated?
Yes, this has always been my understanding too. I mean, on-axis, the two should sum coherently since the path lengths from microphone to each source are the same. But still, the two sources are not acoustically close above 100Hz or so. And then there is also the matter of acoustic centers, which probably shift w/frequency a little differently due to the larger effective mouth size. Lots of little differences between a single horn with one or two square meters mouth size and a couple horns with twice that much area.
__________________
Visit the π Speakers website
High-quality audiophile loudspeakers and kits
  Reply With Quote
Old 7th January 2012, 02:20 AM   #1286
diyAudio Member
 
Join Date: Jun 2007
Quote:
Originally Posted by Wayne Parham View Post
I mean, on-axis, the two should sum coherently since the path lengths from microphone to each source are the same.
Hi Wayne,

Provided that there is not a slight breeze blowing, and that there are no random reflections from the ground :-).

Kind regards,

David
__________________
www.hornresp.net
  Reply With Quote
Old 7th January 2012, 02:46 AM   #1287
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by David McBean View Post
Hi Art,

Excellent - many thanks.

The two things that continue to puzzle me are:

1. Why your test results and now those of Wayne, show only a 6 dB gain at low frequencies rather than a 9 dB gain (my previous post refers) - particularly since you indicated in an earlier post that the combined response of multiple front loaded horns is extended downwards in frequency (if I understand correctly).

2. Why the response of multiple tapped horns is not extended downwards, similar to the front loaded horns you compared them against.

Kind regards,

David
I am puzzled when simulations don’t agree with measured results, you are puzzled when your simulation does not agree with measured results that can be seen from many different sources . Your Hornresp program is incredibly useful, it will be even more so when it agrees more closely with measured results.

Doubling the radiating area of two equally powered speakers adds 6 (.02) dB.
In the case of "too small mouth" FLH, such as most bass horns, an additional LF increase occurs, Wayne's 12Pi appears to have about a 1.5 dB LF increase.

If Hornresp predicts an additional 9 dB rather than the 7.5 dB LF increase, it is inconsistent with measured results.

Wayne, having both the Hornresp sims and his LMS results could give a more accurate account of the disparity, perhaps he will reply to that .

Wayne's measured increase with a pair of his FLH correlates well with my own measurements of multiple FLH, and others he has tested.

Silas Pradetto has measured 1, 2, and 4 Labhorns, similar increases occurred.

Typical TH have a much smaller radiating exit than similar volume FLH, the TH exits are usually only a couple times SD.
My Keystone TH has nearly the same front dimension as the 12Pi, but does not exhibit any LF increase from one to two cabinets.
My 2x10" small TH (26.5 x 22.5 x 15 inch) also does not exhibit a low corner reduction in multiples.

Tom Danley has mentioned many times that TH do not have an increased low corner in multiples.

Bass reflex cabinets don't have much of a reduced LF corner in multiples either, other than the slightly reduced FS from mutual coupling .

Having used BR cabinets from one cone to 112 cones, and FLH from one cone to 80, I can tell you that the difference in FLH LF gain compared to BR gain is substantial.

I will leave the theory to why FLH, BR and TH enclosures respond differently in multiples to theorists, I am more an empiricist, I measure and listen, and make changes until results improve.

Art
  Reply With Quote
Old 7th January 2012, 03:04 AM   #1288
diyAudio Member
 
Wayne Parham's Avatar
 
Join Date: Feb 2004
I thought probably most people had seen the Hornresp models and measurements of my 12Pi hornsub. They've been posted online for years and subject of many discussions on various messageboards. Otherwise I would have pointed them out earlier. In many of those discussions, I've mentioned how very good I thought the Hornresp model was, and how close the response curve predicted was to what was measured. I even went to the trouble of modeling and building three different versions of the 12Pi hornsub, each with slightly different front and rear chamber sizes. The models and the measurements correlated very well.

Here is a link with all this data:

Pi Speakers - 12Pi Basshorn Subwoofer with Push/Pull Drive

This page shows the Hornresp model of the prototype 12Pi and the LABhorn:

PiSpeakers Forum - 12Pi observations and comparisons with other designs - Wayne Parham, July 08, 2005 at 03:53:47

I used a much older version of Hornresp at the time I designed this horn, but the input forms are shown so you can see how I described the model on that page.

This page shows measurements of the prototype 12Pi:

ProSpeakers Forum - Re: Hornsub shootout RESULTS - 12Pi - Wayne Parham, October 15, 2005 at 14:20:02

Measurements were done using an LMS system outdoors at high power levels at 10M. Even at this distance, the signal to noise is very good and results perfectly consistent and reliable. You can run a sweep several times and always get the same chart. So this is very repeatable and reliable. I would say this is probably the most universally accepted method for obtaining accurate results - 10 meters / 100 watts outdoors ground plane.

This page describes the first and second production versions, including Hornresp models:

PiSpeakers Forum - 12Pi basshorn subwoofer - the best yet! - Wayne Parham, October 04, 2007 at 15:33:34

I say Hornresp models are shown, but they aren't really - only the output screens are shown. But the differences are described. The only changes are the front and rear chambers. So you can take the input screens from the prototype and change the front and rear chambers to get the 12Pi v1 or v2 models.

Both of these pages show measurements of the 12Pi v1:

ProSpeakers Forum - 12Pi - Wayne Parham, October 18, 2006 at 11:31:36
ProSpeakers Forum - Pi Speakers 12Pi v1 - Wayne Parham, October 21, 2007 at 14:56:15

I hope these models and charts prove to be helpful. There is a lot of data there that can be used to compare Hornresp models to accurate measurements of physical models.
__________________
Visit the π Speakers website
High-quality audiophile loudspeakers and kits

Last edited by Wayne Parham; 7th January 2012 at 03:09 AM.
  Reply With Quote
Old 7th January 2012, 09:05 AM   #1289
diyAudio Member
 
Join Date: May 2007
I remember mr.Danley talked about the soundwaves coming out of the horn not as a flat wave but more like a sphere/bubble.
Wouldnt this make the horn longer than its physical dimensions?
And because of that, make 4 coupled TH's even longer?
Or does it only apply to FLH's?

In any case, would this difference show up in a impedance-sweep of one and four?

Dag
  Reply With Quote
Old 7th January 2012, 12:36 PM   #1290
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
Is a "Tapped Horn" really a horn in the bottom octave it operates in?
(I don't think so)
__________________
Candidates for the Darwin Award should not read this author.
  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
Here is a Challenge latala Solid State 41 12th May 2011 01:13 AM
Renovation Challenge ZirconiumZephyr Multi-Way 16 1st September 2009 08:38 AM
Design Challenge #1 kgillies Subwoofers 12 13th June 2007 03:20 PM
a challenge --or I need help lawrence99 Car Audio 0 9th March 2005 04:44 AM
The challenge ! thylantyr Solid State 51 24th July 2003 08:41 PM


New To Site? Need Help?

All times are GMT. The time now is 10:56 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2