Speakerplans.com Homepage
Forum Home Forum Home > General > Advanced Discussion
  New Posts New Posts RSS Feed - Learning horn resp, need some advice.
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Learning horn resp, need some advice.

 Post Reply Post Reply Page  <123
Author
Message
fatfreddiescat View Drop Down
Registered User
Registered User


Joined: 15 October 2010
Location: N.E.Wales
Status: Offline
Points: 469
Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 15 January 2017 at 3:51pm
Ah ok thanks.
Back to Top
SouthwestCNC View Drop Down
Young Croc
Young Croc
Avatar

Joined: 27 November 2015
Status: Offline
Points: 716
Post Options Post Options   Thanks (0) Thanks(0)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 16 January 2017 at 10:20am
Originally posted by fatfreddiescat fatfreddiescat wrote:

Originally posted by SouthwestCNC SouthwestCNC wrote:

Hi there, I thought it's about time I start learning how to simulate horn response. Getting on quite well with it and now like to understand how using the ported throats works geometry wise. If the port vents into a horn throat does the length of the port include the remaining length to front of the horn its vented into or not. Or in that scenario does the port then become a tapered port?

TIA


My cabs are ported at the throat, sims suggest the port length and area would be at 65Hz if it was a traditional reflex cab, but with having the full length of the horn attached, the tuning drops to 32Hz.
On my cabs the port area is smaller than the throat area and is a hole cut in 18mm plywood.
The problem with the hornresponse sims is that if I model the cab, it still gives a tuning as though the horn is not acting as a duct.






And this goes for the new version of hornresp? How did you manage to identify the port tuning required was that of a 65hz wavelength to achieve an overall tuning of 35hz taking into account the horn is acting as a duct? Trial and error?
Back to Top
fatfreddiescat View Drop Down
Registered User
Registered User


Joined: 15 October 2010
Location: N.E.Wales
Status: Offline
Points: 469
Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 16 January 2017 at 12:57pm
Very much trial and error, I built various test boxes that I could change panels to convert between 4th/6th order bandpass and reflex, using bricks and waste pipe to adjust tuning, followed the same method for the horn with blanking plates to change from internal / external vents and sealed rear chamber. First box was built approx 18 years ago.
Back to Top
odc04r View Drop Down
Old Croc
Old Croc
Avatar

Joined: 12 July 2006
Location: Sarfampton
Status: Offline
Points: 4678
Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 16 January 2017 at 1:22pm
It's an odd one, I could easily see how in this case simulation would struggle to match reality. If the port doesn't terminate one end in essentially infinite space and the other in a chamber far enough from any walls, you need to start making end corrections. But worse than just end corrections is when they terminate into a region of the horn where acoustic velocity and pressure is far from normal. I guess the electronic analog would be boot strapping.
Back to Top
SouthwestCNC View Drop Down
Young Croc
Young Croc
Avatar

Joined: 27 November 2015
Status: Offline
Points: 716
Post Options Post Options   Thanks (0) Thanks(0)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 16 January 2017 at 2:30pm
Might be a ridiculous idea but Could the port not be simmed as two seperate horns, as if the rear chamber became the front chamber with a throat port only applying a rear chamber that simulates the remaining volume in the horn. Then sim the correct chamber orientation of driver and combine the results?

 Quite tempted to build one with a port tuning of 65hz to begin with and do the same. If only these could be 3d printed in miniature and tested. 
Back to Top
fatfreddiescat View Drop Down
Registered User
Registered User


Joined: 15 October 2010
Location: N.E.Wales
Status: Offline
Points: 469
Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 16 January 2017 at 10:32pm
There are various ways to try and fudge aspects of it HR although probably just as quick to just build a test setup- straight horn with one expanding surface and a reflex box with adjustable port that can be clamped to the horn profile. Model as for a standard ported horn for a starting point.
I also tried modeling it with Akabak but didn't get anything useful although that could have been my understanding of the software.
I will try and get some test results to upload but may be a few weeks before I get to do that, can't find any at the mo so will have to re test , all the old ones were not in ideal test conditions.
Back to Top
SouthwestCNC View Drop Down
Young Croc
Young Croc
Avatar

Joined: 27 November 2015
Status: Offline
Points: 716
Post Options Post Options   Thanks (0) Thanks(0)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 23 January 2017 at 11:04pm
Id be interested to see. Ive been going exactly as I mentioned and fudging it in horn resp by simulating the port as s1/s2 then leading to the horn and it seems to narrow the possible frequency tuning range of the port and the horn takes over, Could need three tunings ie two different length ports to compensate. All rather complicated.
Back to Top
fatfreddiescat View Drop Down
Registered User
Registered User


Joined: 15 October 2010
Location: N.E.Wales
Status: Offline
Points: 469
Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 24 January 2017 at 8:00am
Using multiple ports is one way to change the tuning, another would be to tune the rear chamber om the high side and then blank off part of the port to lower it.

As and when I get around to working on another version I will make a straight horn expanding from zero in one plane and adjust the position of the rear chamber / driver along the axis of the horn.
I would also aim to have the port tuning half an octave or more below the horn cutoff frequency.
Back to Top
jaya000 View Drop Down
Registered User
Registered User


Joined: 24 August 2008
Location: India
Status: Offline
Points: 59
Post Options Post Options   Thanks (0) Thanks(0)   Quote jaya000 Quote  Post ReplyReply Direct Link To This Post Posted: 29 June 2017 at 12:55pm
Originally posted by corell corell wrote:



How to get high resolution image of yoiur post?
Back to Top
DMorison View Drop Down
Young Croc
Young Croc


Joined: 14 March 2007
Location: Aberdeen
Status: Offline
Points: 898
Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 29 June 2017 at 2:24pm
Originally posted by jaya000 jaya000 wrote:


How to get high resolution image of yoiur post?

Right click & save the images, or pop them open in new tabs - they're not much bigger that way, but it is enough difference that you can read them.
Back to Top
SouthwestCNC View Drop Down
Young Croc
Young Croc
Avatar

Joined: 27 November 2015
Status: Offline
Points: 716
Post Options Post Options   Thanks (0) Thanks(0)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 01 November 2017 at 12:17pm
Originally posted by fatfreddiescat fatfreddiescat wrote:

There are various ways to try and fudge aspects of it HR although probably just as quick to just build a test setup- straight horn with one expanding surface and a reflex box with adjustable port that can be clamped to the horn profile. Model as for a standard ported horn for a starting point.
I also tried modeling it with Akabak but didn't get anything useful although that could have been my understanding of the software.
I will try and get some test results to upload but may be a few weeks before I get to do that, can't find any at the mo so will have to re test , all the old ones were not in ideal test conditions.

Any revelations FreddiesCat? With 0 volume on the rear chamber 0 atc vtc  and no port you are effectively simulating a tapped horn with horn flare extension on the front are you not?. Im thinking i have a tham 12 here, I should sim it as is, measure. Then sim with a horn flare extension and build the flare and stick it on the tham12 and re measure. Will at least give me an idea how accurate horn resp can sim this arrangement initially before trying any porting. 
Back to Top
SouthwestCNC View Drop Down
Young Croc
Young Croc
Avatar

Joined: 27 November 2015
Status: Offline
Points: 716
Post Options Post Options   Thanks (0) Thanks(0)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 01 November 2017 at 1:34pm
Just had a go at it and on second thought its probably a futile exersize, Can get some lovely improvements to response but group delay goes through the roof and and more worrying is even with a short horn extension it introduces sharp changes in phase inside operating range so just be measuring distortions thats unlikely to tell me much. 



Edited by SouthwestCNC - 01 November 2017 at 1:34pm
Back to Top
 Post Reply Post Reply Page  <123
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 11.10
Copyright ©2001-2017 Web Wiz Ltd.

This page was generated in 0.047 seconds.