Truextent Beryllium replacement diaphragms - Page 4 - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

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 21st December 2012, 08:29 AM   #31
Ang is offline Ang  United States
diyAudio Member
 
Join Date: Feb 2006
Location: Pittsburgh
Has anyone tried swapping out the 4" diaphragms from 2" B&C CD's with these? I don't see them listed on the spec sheet, but perhaps someone found that it works?
  Reply With Quote
Old 23rd January 2013, 12:48 AM   #32
Legis is offline Legis  Finland
diyAudio Member
 
Legis's Avatar
 
Join Date: Dec 2009
I finally got my pair of JBL 2446Js, these things are quite huge. I will be playing them for awhile with the original phrams, but at some point Truextent is the natural course of action. I bet they will sound wonderfull in a right horn, they sound quite good even without a horn.

2446J and 8"

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.
  Reply With Quote
Old 23rd January 2013, 01:27 AM   #33
pos is offline pos  Europe
diyAudio Member
 
pos's Avatar
 
Join Date: Feb 2008
Location: Paris
Another measurement for those interested, comparing a 2452H (ribbed titane) and a 2450SL+Truextent, both on the same PT-F95HF waveguide.

3rd distortion is plotted, and is lower that the titanium diaphragm as you can see.
A small distortion peak can be seen just above 7kHz. As it is 3rd distortion it does happen just above 21kHz, which corresponds to the big response peak (breakup mode). That 21kHz breakup also clutters the impulse response (ringing), but is of course rather benign at this high a frequency. EQ would get rid of the response peak, but not of the 3rd distortion peak (but who can hear that sort of thing anyway). Reticulated foam on the other hand would probably take care of both, so it would be interesting to try...
Attached Images
File Type: png 3195202452Hvs2450Bedisto.png (33.6 KB, 760 views)

Last edited by pos; 23rd January 2013 at 01:41 AM.
  Reply With Quote
Old 23rd January 2013, 10:04 PM   #34
diyAudio Member
 
Join Date: Nov 2010
Quote:
Originally Posted by Legis View Post
I finally got my pair of JBL 2446Js, these things are quite huge. [/IMG]
May I ask what you paid for them?

Quote:
Originally Posted by pos View Post
Another measurement for those interested, comparing a 2452H (ribbed titane) and a 2450SL+Truextent, both on the same PT-F95HF waveguide.
Thanks for the data, several surprises.
I am surprised that breakup seems to occur at the same frequency for the Ti and the Be. Very different stiffness to mass ratio so this seems unlikely. Could this be a measurement anomaly? due to a resonance in the microphone perhaps. Or a real anomaly but due to a resonance elsewhere in the driver, maybe a cavity mode?
The lower distortion is also a bit of a surprise. I expected similar pistonic response in the lower frequencies. Perhaps the polymer suspension really is as superior as TrueExtent claims. Very nice for you anyway.

Best wishes
David
  Reply With Quote
Old 24th January 2013, 01:07 AM   #35
pos is offline pos  Europe
diyAudio Member
 
pos's Avatar
 
Join Date: Feb 2008
Location: Paris
Quote:
Originally Posted by Dave Zan View Post
I am surprised that breakup seems to occur at the same frequency for the Ti and the Be.
Not sure what you are referring to here.
The Ti ribbed diaphragm has two main breakup modes that show on the frequency response and CSD around 12khz and around 17khz.
The Truextent has its main breakup at 21khz.

Quote:
The lower distortion is also a bit of a surprise. I expected similar pistonic response in the lower frequencies.
At it is 3rd harmonic distortion it happens at 3 times the frequency it is reported at, so it looks like it is due to breakups (more spread with the Ti diaphragm, both because of the ribs and the diamond surround I think).
  Reply With Quote
Old 24th January 2013, 06:01 AM   #36
Legis is offline Legis  Finland
diyAudio Member
 
Legis's Avatar
 
Join Date: Dec 2009
Quote:
Originally Posted by Dave Zan View Post
May I ask what you paid for them?
Sure! Around 450$ for the pair plus shipping. They are mint, look almost like new, and phrams are original JBL.

I think I will try to mate some transconductance/current drive amp with them at some point. I like what a 33R series resistor does to the sound, even though measured IMD differences are very small.
  Reply With Quote
Old 24th January 2013, 07:10 AM   #37
diyAudio Member
 
Join Date: Nov 2010
Quote:
Originally Posted by pos View Post
Not sure what you are referring to here.
....
The Truextent has its main breakup at 21khz.
There is also a substantial spike in the Ti. curve at the same frequency and the associated spikes in the 3rd harmonic distortion at 7 kHz. Seems a bit of a coincidence. You mention a CSD so perhaps it is clearer on that.

Quote:
At it is 3rd harmonic distortion it happens at 3 times the frequency it is reported at
Yes of course, but there is a substantial difference even below 4Khz where neither the Ti or Be have breakup modes below 12 Khz.

Best wishes
David

Last edited by Dave Zan; 24th January 2013 at 07:16 AM.
  Reply With Quote
Old 24th January 2013, 08:31 AM   #38
tomtom is offline tomtom  Slovakia
diyAudio Member
 
Join Date: Dec 2006
In case of compression driver it is very difficult to know what is diaphragm breakup and what is cancelation of HF from phase plug /from measurement/. The cancelation is different for different phragm because of different breakup.
  Reply With Quote
Old 24th January 2013, 12:07 PM   #39
pos is offline pos  Europe
diyAudio Member
 
pos's Avatar
 
Join Date: Feb 2008
Location: Paris
Quote:
Originally Posted by Dave Zan View Post
There is also a substantial spike in the Ti. curve at the same frequency and the associated spikes in the 3rd harmonic distortion at 7 kHz. Seems a bit of a coincidence. You mention a CSD so perhaps it is clearer on that.
Yes I think it is a coincidence, and the peaks are not exactly at the same frequency.
On the CSD you clearly see two ringing traces at 12 and 17khz for the Ti ribbed idaphragm.

Quote:
Yes of course, but there is a substantial difference even below 4Khz where neither the Ti or Be have breakup modes below 12 Khz.
They both have breakups bellow those that we clearly see on the frequency reponse.

This is particularly true for the Ti ribbed diaphgram: the entier >5khz range is cluttered with small partially controlled breakups, due to both the ribs (that give a boost in this range compared to a normal Ti diaphragm) and the diamond surrounds (that allow some extention in the UHF). It seems to show in the distortion measurement also...

In comparison the Truextent Be is much smoother in this range, and does not attempt to control the dome breakups that occure above 15khz. And neother does it rely on parasitic resonances of the surrounds to extend its reponse up high. And it shows, as it drops quite a bit in the UHF (despite the higher mass breakpoint), but nothing that a good EQ cannot compensate...

It is similar to the TAD TD4001 vs TD4003 comparison.
  Reply With Quote
Old 24th January 2013, 12:09 PM   #40
pos is offline pos  Europe
diyAudio Member
 
pos's Avatar
 
Join Date: Feb 2008
Location: Paris
Quote:
Originally Posted by Legis View Post
I like what a 33R series resistor does to the sound, even though measured IMD differences are very small.
Intersting
Have you compared with an Lpad or an autoformer?
  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
The Whole Truth About Beryllium Diaphragms mowry Multi-Way 280 25th June 2009 06:50 AM


New To Site? Need Help?

All times are GMT. The time now is 12:06 AM.


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