Beyond the Ariel - Page 877 - 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 15th May 2013, 03:06 PM   #8761
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by ra7 View Post
Lynn, the low end of the XT25 gets a huge boost, about 10db in the 1-4 kHz range. Pretty useful. Further up, the response evens out. But as you mention, there are many dips and peaks, apart from the low end boost.

Apart from real measurements, I guess I was posing a more fundamental question about whether given the right matching between dome/ring radiator and waveguide, can it be superior to a CD/horn combo? Is the response of a traditional tweeter inherently smoother than that from a CD? If all we are craving is directivity, then it might be a worthwhile solution.
Smooth frequency response, smooth polar response, accurate transient response, wide dynamic range all are important, but which is most important is a subjective choice we each make.

To be "superior" in audio is a subjective quality.

The Vifa XT25 appears to be smoother than most horn/compression drivers, an example of the XT25 and a BMS 4550 on a conical horn (frequency resolution of 1.5 Hz like you wanted) below.

Of course, as you mention, the XT25 in a waveguide does not have smooth response.

Even if the waveguide provides the XT25 10 dB of midband gain, it still is an order of magnitude lower than most compression driver/horns, it will take the full power of 50 watts to achieve the SPL that 5 watts would do with the compression driver.
The directivity of the XT25 narrows to about 90 degrees at 10 kHz, so a 90 degree waveguide will have no increase in sensitivity that high, comparing the BMS 4550 on the conical horn to the XT25 at 10kHz we would see (hear) more like a 15 dB drop in sensitivity (20 dB on the horn used in the comparison which is 115 dB one watt one meter midband).

Once you have messed with the smooth on axis response of the XT25 by putting it in a waveguide, it looses that metric of being "superior", and from a dynamic standpoint, it can't come close to a good compression driver.

Art
Attached Images
File Type: png VifaXT25, BMS4550.png (95.1 KB, 619 views)

Last edited by weltersys; 15th May 2013 at 03:08 PM.
  Reply With Quote
Old 15th May 2013, 03:34 PM   #8762
badman is offline badman  United States
diyAudio Member
 
badman's Avatar
 
Join Date: Sep 2003
Location: Sunny Tustin, SoCal
Quote:
Originally Posted by weltersys View Post

Once you have messed with the smooth on axis response of the XT25 by putting it in a waveguide, it looses that metric of being "superior", and from a dynamic standpoint, it can't come close to a good compression driver.

Art
The shown response on the waveguide tracks the flat-baffle power response and looks quite smooth to me, with the exception of the one big peak. If you mean that the "lump" response isn't smooth, that's a problem with compression drivers too, they all exhibit that behavior on constant directivity horn/waveguides (but you already knew that). Is it just the HF peak that's bothering you? Certainly one would want to notch that.

For home levels, the need for the higher output and power handling of a compression driver are less key, I'm using a soft dome on a constant directivity horn and getting great results once the power response is accounted for, for my rear-firing section of my speakers.

Click the image to open in full size.
__________________
I write for www.enjoythemusic.com in the DIY section. You may find yourself getting a preview of a project in-progress. Be warned!
  Reply With Quote
Old 15th May 2013, 03:57 PM   #8763
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by badman View Post
The shown response on the waveguide tracks the flat-baffle power response and looks quite smooth to me, with the exception of the one big peak. If you mean that the "lump" response isn't smooth, that's a problem with compression drivers too, they all exhibit that behavior on constant directivity horn/waveguides (but you already knew that). Is it just the HF peak that's bothering you? Certainly one would want to notch that.
Unlike many contributors in this post, peaks don't bother me, I just equalize them out .

The upper graph in #8761 is a stock Vifa XT25 on a flat baffle measured at .5 meter that I found when Googling that driver.

The lower graph is a BMS 4550 compression driver on a Welter Systems Maltese horn on a 1 square meter flat baffle about 5 feet off the ground pointed skyward outside at two meters.

As far as I know, ra7 has not posted any graphs of his XT25 on a waveguide, but he wrote it "gets a huge boost, about 10db in the 1-4 kHz range".

Neither graph shows his observation, they were just presented to show relative smoothness between a compression driver/horn and the tweeter he uses, without a waveguide.

Art
  Reply With Quote
Old 15th May 2013, 04:12 PM   #8764
ra7 is offline ra7  United States
diyAudio Member
 
Join Date: Feb 2009
Blog Entries: 1
I do have measurements, in Holm, that I can post later this evening.

I'm aware of the ultra flat response of the XT25 on a baffle. On the SEOS-12, there are peaks and dips, but these can be EQed. In a CD, there are many small squiggles that look flat when smoothing is applied. That is the difference I'm trying to understand.

I was recently re-reading Toole's book, especially Chapter 18. He says that smoothness of the response was found to have higher preference compared to flatness. Small resonances that are usually lost in smoothed or gated measurements are very audible.
  Reply With Quote
Old 15th May 2013, 04:19 PM   #8765
badman is offline badman  United States
diyAudio Member
 
badman's Avatar
 
Join Date: Sep 2003
Location: Sunny Tustin, SoCal
Quote:
Originally Posted by weltersys View Post
The upper graph in #8761 is a stock Vifa XT25 on a flat baffle measured at .5 meter that I found when Googling that driver.

The lower graph is a BMS 4550 compression driver on a Welter Systems Maltese horn on a 1 square meter flat baffle about 5 feet off the ground pointed skyward outside at two meters.
Ah- I missed that- I thought the lower was the XT25 on a WG- thanks for the clarification.
__________________
I write for www.enjoythemusic.com in the DIY section. You may find yourself getting a preview of a project in-progress. Be warned!
  Reply With Quote
Old 15th May 2013, 04:33 PM   #8766
ra7 is offline ra7  United States
diyAudio Member
 
Join Date: Feb 2009
Blog Entries: 1
Art, thanks for the measurements. The BMS4550 measurements have a resolution of 1.5 Hz? That is great!

I might do a nearfield comparison between the DNA360 and XT25 tonight.
  Reply With Quote
Old 15th May 2013, 04:36 PM   #8767
diyAudio Member
 
Robh3606's Avatar
 
Join Date: Nov 2002
Location: Destiny
Quote:
Small resonances that are usually lost in smoothed or gated measurements are very audible.
Hello ra7

Yes but typically not in the tweeters bandwidth, the lower frequencies where you need longer gate times are where you see it the most. It's not all that hard to just look at the ungated measurement to see what's going on. Also depends on the Q and amplitude, higher Q generally being less audible than a lower Q resonances.

Rob
__________________
"I could be arguing in my spare time"
  Reply With Quote
Old 15th May 2013, 04:44 PM   #8768
wesayso is offline wesayso  Netherlands
diyAudio Member
 
wesayso's Avatar
 
Join Date: Jul 2007
Here's a Vifa XT25 in a waveguide (WG-300) from the above link I posted.
The 10+ dB gain is obvious:
Click the image to open in full size.
Note the smoothed 1/9 oct note on the graph.
  Reply With Quote
Old 15th May 2013, 04:51 PM   #8769
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by ra7 View Post
I do have measurements, in Holm, that I can post later this evening.

I'm aware of the ultra flat response of the XT25 on a baffle. On the SEOS-12, there are peaks and dips, but these can be EQed. In a CD, there are many small squiggles that look flat when smoothing is applied. That is the difference I'm trying to understand.

I was recently re-reading Toole's book, especially Chapter 18. He says that smoothness of the response was found to have higher preference compared to flatness. Small resonances that are usually lost in smoothed or gated measurements are very audible.
"Small", another relative term when it comes to resonances. I don't hear the .5 to 3 dB resonances in a "smooth" horn driver, but when they are large enough, like 6-12 dB, then I may detect the difference in an A/B test.

The Vifa XT25 may be smoother than the Vifa dome tweeter in the Tannoy PBM 6.5 I use in my control room.

The same BMS 4550 from post 8761 and the PBM 6.5 are both shown below with no smoothing, 1.5 Hz resolution.
The horn/driver is "smoother" in the critical 1-6 kHz range, the dome tweeter smoother (but less flat) above 6 kHz.

At any rate, some of the drivers I tested were less smooth, all equalized relatively flat, you can listen to them and report back if you are in agreement with Toole.
My ears are not golden enough to tell them apart until driven in to distortion.

High Frequency Compression Driver Evaluation

Recordings of six drivers using different diaphragm materials and size, phase plug designs, and magnet structures, all on the same horn are there.

Art
Attached Images
File Type: png Tannoy PBM6.5,BMS4550.png (114.0 KB, 561 views)
File Type: png 1-4kHz.png (102.7 KB, 464 views)

Last edited by weltersys; 15th May 2013 at 05:01 PM.
  Reply With Quote
Old 16th May 2013, 10:35 AM   #8770
diyAudio Member
 
Join Date: Jun 2006
I can't help thinking that the solution with 2 x 12" would be nice with a crossover around 950 and a E-JMLC on top the get the drivers closer and to have good dispersion.
  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



New To Site? Need Help?

All times are GMT. The time now is 11:43 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