Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Foam Core Board Speaker Enclosures?
Foam Core Board Speaker Enclosures?
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 11th November 2013, 06:46 PM   #2011
wesayso is offline wesayso  Netherlands
diyAudio Member
 
wesayso's Avatar
 
Join Date: Jul 2007
Quote:
Originally Posted by xrk971 View Post
Wesayso,
Yes, it was a compromise because I am trying to make a two way so this is really more of a bass driver that I am forcing to get higher freq. I have not looked at the phase mismatch with the HF yet. The simulations showed that at this location the bandwidth goes from 150 Hz to about 1300 Hz. Putting the ports near the throat would push this to a 385 Hz low end and then I would really need a 3 way. One thing I am seeing in working multiple drivers is the pain in making good cross over. I may have to Ho with a digital solution like miniDSP.
I figured as much... if passive were easy, I'm already dreaming away thinking of a home synergy with 4 TC9's and a Vifa XT25 instead of a CD driver.
I think you might need some time alignment between mids and CD in this configuration? Or at least a longer path from the mids into the horn at that position I'd guess. Is the distance of the holes within the quarter wave length of the chosen crossover point?

Last edited by wesayso; 11th November 2013 at 07:15 PM.
  Reply With Quote
Old 11th November 2013, 07:33 PM   #2012
drmcclainphd is offline drmcclainphd  United States
diyAudio Member
 
Join Date: Aug 2013
Location: Abingdon, Virginia
Looking back through the thread I see many have already suggested the same or similar to what I've said, including the builder. My fault for not reading it all, but good in that it means we're all on the same page and probably correct in our assumptions.

I once suspended a full length mirror from the ceiling and stuck a couple transducers on the back. What a weird sensation, watching myself play guitar with the sound coming from the image in front of me.

The Vifas are flat out to 20k on axis (the off axis not being pertinent to a horn, I think). You might consider letting them dominate some higher freqs and xo up high. Maybe a low pass on them around 8 to10k and some well padded very high end tweeters. Like I said, I favor piezos. Cheap, easy to work with, and if their little plastic horns don't fit your design, the element in back is usually around 1" dia. Plus, they don't figure into network impedance. High pass them at the same higher freq that the Vifas are low passed, and they might not even need to be padded. Well, a dog might disagree, since a lot of piezos go up to 27k or so.

Hey, where you at in Virgina, xrk971? I'm in SWVA, near Bristol.
  Reply With Quote
Old 11th November 2013, 08:24 PM   #2013
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Foam Core Board Speaker Enclosures?
Quote:
Originally Posted by wesayso View Post
I figured as much... if passive were easy, I'm already dreaming away thinking of a home synergy with 4 TC9's and a Vifa XT25 instead of a CD driver.
I think you might need some time alignment between mids and CD in this configuration? Or at least a longer path from the mids into the horn at that position I'd guess. Is the distance of the holes within the quarter wave length of the chosen crossover point?
I have a design where a Vifa BC25 silk dome can work very well too - I just happened to have the PH44's already.

To tell you the truth, I am new to this Synergy business and have not thought about the XO freq and the 1/4-wave length of the horn. Since I did not consider that at all, I am sure it is not correct. My bass ports are located at a horn circumference of 83 cm and that corresponds to 103 Hz quarter wave. I think this is for making sure the port dia is much smaller than the wavelength affected by the port size.

The port is located about 6.5 in from the throat of the PH44 horn so the quarter wave freq is 518 Hz. So not sure if this means that I really should have it closer in at about 3.25 in from the throat?

Last edited by xrk971; 11th November 2013 at 08:46 PM.
  Reply With Quote
Old 11th November 2013, 08:41 PM   #2014
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Foam Core Board Speaker Enclosures?
Quote:
Originally Posted by drmcclainphd View Post
Looking back through the thread I see many have already suggested the same or similar to what I've said, including the builder. My fault for not reading it all, but good in that it means we're all on the same page and probably correct in our assumptions.

I once suspended a full length mirror from the ceiling and stuck a couple transducers on the back. What a weird sensation, watching myself play guitar with the sound coming from the image in front of me.

The Vifas are flat out to 20k on axis (the off axis not being pertinent to a horn, I think). You might consider letting them dominate some higher freqs and xo up high. Maybe a low pass on them around 8 to10k and some well padded very high end tweeters. Like I said, I favor piezos. Cheap, easy to work with, and if their little plastic horns don't fit your design, the element in back is usually around 1" dia. Plus, they don't figure into network impedance. High pass them at the same higher freq that the Vifas are low passed, and they might not even need to be padded. Well, a dog might disagree, since a lot of piezos go up to 27k or so.

Hey, where you at in Virgina, xrk971? I'm in SWVA, near Bristol.
So along the lines of an all TC9FD single type full range driver, maybe we can mount the 4 Vifa's in sideways star config to form a 1 in duct which then leads to the throat of the horn. Let the Vifa's go from whatever the low cutoff is to their natural 20 kHz high end. I think the problems is, the HF's won't make it out since the Vifa design requires an open face for the HF's to radiate from the paper dustcap, if that is blocked may not work. It then goes back to the volume of the chamber being very small which is why CD's are the way they are. A closer approximation is to put 4 Vifa's open face in a 2x2 array and put that at the horn throat which contains the 4 drivers. At a distance far away, they will appear a single point source full range driver.

I live up in NoVa.
  Reply With Quote
Old 11th November 2013, 09:28 PM   #2015
wesayso is offline wesayso  Netherlands
diyAudio Member
 
wesayso's Avatar
 
Join Date: Jul 2007
Maybe you'd need something in the line of Tom Danley's layered combiner for that .
Click the image to open in full size.

Click the image to open in full size.

Last edited by wesayso; 11th November 2013 at 09:35 PM.
  Reply With Quote
Old 11th November 2013, 10:06 PM   #2016
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Foam Core Board Speaker Enclosures?
You know, I tried running the horn with just the Vifa's and it doesn't sound too bad. Just missing a little of the sparkle but pretty listenable.
  Reply With Quote
Old 12th November 2013, 01:15 PM   #2017
BP1Fanatic is offline BP1Fanatic  United States
diyAudio Member
 
BP1Fanatic's Avatar
 
Join Date: Jan 2009
Location: Columbus, Ohio
Quote:
Originally Posted by wesayso View Post

Like this picture:

Click the image to open in full size.

from: Synergy Horns-Dayton and PRV.....
Impressive speakers! I like how the wall terminals are on display too!
  Reply With Quote
Old 13th November 2013, 02:49 PM   #2018
drmcclainphd is offline drmcclainphd  United States
diyAudio Member
 
Join Date: Aug 2013
Location: Abingdon, Virginia
Quote:
Originally Posted by xrk971 View Post
So along the lines of an all TC9FD single type full range driver, maybe we can mount the 4 Vifa's in sideways star config to form a 1 in duct which then leads to the throat of the horn. Let the Vifa's go from whatever the low cutoff is to their natural 20 kHz high end. I think the problems is, the HF's won't make it out since the Vifa design requires an open face for the HF's to radiate from the paper dustcap, if that is blocked may not work. It then goes back to the volume of the chamber being very small which is why CD's are the way they are. A closer approximation is to put 4 Vifa's open face in a 2x2 array and put that at the horn throat which contains the 4 drivers. At a distance far away, they will appear a single point source full range driver.

I live up in NoVa.
I think that sounds like a reasonable adjustment to the design. The loss of "sparkle" you mention elsewhere is likely due to having them try to reproduce low freq at the same time. That sucks up a lot of energy, and the reproduction of the low freqs precludes accurate reproduction of the highs. Perhaps use a small woofer or two (I think subs might be a bit much for the substructure in terms of weight and box vibration) Give them the low freq and let the Vifas handle everything above. I've favored the Sony "Dynamic Bass" poly cone neo mags (Parts Express # 299-011). I built a 2.1 PA with 48 of them (a Sweet 16 center and two 2x6 towers, plus a couple subs and 4 piezos). Marvelous little drivers. They've sold out, in part thanks to me. I'd be glad to donate a couple to the project for testing.

As for the problem with the 1" opening for the Vifas, consider cutting them a full sized opening then placing a Karlson style bilateral parabolic vent over them. It'll focus the freqs in the way the horn expects. I can calculate the proper shape for you, given the size of the opening and the angle of the driver to axis. They can be simply taped in place for testing.
  Reply With Quote
Old 13th November 2013, 02:59 PM   #2019
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Foam Core Board Speaker Enclosures?
Doc McClain,
I have thought about a Karlson type aperture too for the little driver injection holes. Although over a 3 in length the frequencies we are dealing with are pretty high to be impacted kind of like a K tube tweeter - also, if you orient the apex of the K aperture towards the horn throat, it may have some Beneficial effects for shielding the CD tweeter wavefront from an abrupt change in geometry. I have had some success modeling the K aperture by approximatig it as a series of variable rectangular aperture radiators in feont of a waveguide for large scales in the bass region like a K15 or Karlsonator.
  Reply With Quote
Old 14th November 2013, 03:07 AM   #2020
drmcclainphd is offline drmcclainphd  United States
diyAudio Member
 
Join Date: Aug 2013
Location: Abingdon, Virginia
I suspect you're right, the high freqs need as much length on the vent as possible. The usual ratio is 5.33 x aperture diameter. It'd take a K-tube to do the job, and that would really mess up your geometry. I've experimented with a 4 point star shaped K type aperture (two K vents, wide ends together) that might fit but that would give a wide dispersion on the high freqs, some towards the throat but some out the front. Good for imaging (stereo and/or depth) but I'm not so sure it'd have that effect on the tweeter wave.
  Reply With Quote

Reply


Foam Core Board Speaker Enclosures?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Replace speaker foam with this odd material? flyingsquirrelman Subwoofers 10 3rd March 2015 07:44 PM
Speaker damping: Foam or expanding foam akunec Multi-Way 4 11th February 2014 01:14 AM
concrete board for enclosures? alandarkdale Multi-Way 6 31st March 2007 08:35 AM
Foam core construction for subwoofers morbo Subwoofers 19 30th August 2005 08:09 PM
speaker foam dave k Multi-Way 2 24th June 2003 05:05 AM


New To Site? Need Help?

All times are GMT. The time now is 07:23 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki