Uniform Directivity - How important is it? - Page 2 - 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 May 2013, 03:26 AM   #11
diyAudio Member
 
Join Date: May 2006
Quote:
Originally Posted by Wayne Parham View Post
It's not a crusade against anyone. This is a technical discussion. One that I would appreciate nobody derail into name calling, or turning it into something personal.
Let's review some comments from post #1.

Quote:
This brings me back to what I said in the first paragraph about some people throwing the baby out with the bathwater. I'm all for uniform directivity, and found myself regularly arguing its virtues over the years. But it seems like lately, I see guys posting polars and sonograms, looking for a holy grail in its virtues. Some have gone way too far with that, in my opinion, and are using prosound techniques to build home hifi speakers. Their polars look wonderful, but their response curves and distortion performance is only so-so.
Shortly after this comment you posted a pic clearly showing the response of a SEOS waveguide (but no proof of the so-so response curves and distortion performance IN A COMPLETE SYSTEM with a LF driver and crossover), and then a bit later you follow up with this evaluation of the graph:

Quote:
Which leads me back to the radial horns. I personally would rather have a radial horn that provided constant directivity in the horizontal, gently collapsing directivity in the vertical and smooth respponse in the pattern than I would a so-called "waveguide" that had peaky response. I've seen some out there that have 5dB ripple, and that's about twice what I would be willing to live with.

A good hifi horn offers response flat within a 2dB window, and a good studio monitor waveguide is able to do this too... But it need not increase response ripple like prosound horns do, otherwise it has thrown the baby out with the bathwater.
That sounds like an attack, not a technical discussion. But if you want to discuss it technically you have to admit that the raw response of a waveguide (without showing the LF driver or the effects of the crossover) isn't showing the whole picture. Here's the responses of a few different SEOS products, unfortunately a quick product search didn't show any off axis responses of the particular SEOS that you measured. Starting with the ones that do have off axis response shown:

Fusion 15
Click the image to open in full size.

Alpha 8
Click the image to open in full size.

They are not perfect but I don't see any babies in that bathwater. The following don't show off axis but I'm sure the off axis measurements are no worse than those shown above.

Fusion 8
Click the image to open in full size.

Fusion 12
Click the image to open in full size.

Alpha 12
Click the image to open in full size.

As far as I can see the raw response is just one data point, not a baby/bathwater situation (unless the waveguide is very bad, which these clearly are not).

Quote:
I can't stand it when an opinion or technical argument is made, and then the response is an ad-hominem attack. That's nothing but a distraction, pure subterfuge. I've seen it before - Seems to be used by some as a fairly clever way to sequester a discussion. Demonize your opponent so that only one side is heard.

And it hasn't been the designers on either side that have done that, if you'll notice. The "crusade" came from somewhere else. It was an emotional ploy, and some innocent parties have been really harmed as a result.

So can we agree to drop that right here and now? I left the other website when they started getting nasty, and it would be a shame to have this thread go the same way. Let's leave the personal stuff out of it, OK?
As soon as I saw the name "SEOS" on the graph and saw your conclusions, I thought exactly the same thing as Pallas. Given your history with the SEOS people don't you think you should have at least cropped the "SEOS" name off the graph if you really wanted a technical discussion? Or maybe chosen another waveguide entirely to critique? You've measured dozens of waveguides, why pick this one?

You say "when they started getting nasty". Maybe I need to reread the discussion again, but I think both sides got pretty nasty when you tried to shame and emotionally blackmail a non profit into donating proceeds to someone that had nothing to do with the currently available products. Is that the innocent party that has been really harmed? IIRC, that innocent party wanted nothing to do with diysoundgroup or it's new and unique products.

Please believe I'm not a diysoundgroup fanboy even though I really wanted to be. I've got a laundry list of complaints with them so I have no horse in this race.

Quote:
The truth is there has been a long-running technical email chain just like this going on behind the scenes, and it is with me and the guys that designed SEOS. The designers of that device are people I would consider friends.

The two design philosophies are really the same - Pi H290C and SEOS12 - with the subtle difference that each has been optimized slightly differently.

When you talk purely about the technology, you find the two are more alike than different, one sharing design approaches from the other. They are almost brothers, each having similar traits along with a few differences.

Bearing all that in mind, what do you think of the idea that I've proposed? Do you think a home hifi waveguide should be optimized for smoothness or for pattern control?
If you really want a technical discussion I think you should start again with a different waveguide to critique, or at least crop the SEOS name out of picture for at least an appearance of objectivity. But until then, my opinion is that the SEOS waveguides can be optimized for very good smoothness AND pattern control, from what I've seen. I don't own any of their products but I've seen a whole bunch of on and off axis measurements and good designers seem to be able to produce good designs with them.

EDIT - I guess the pics don't show up but they are all available on their product pages. I'm sure everyone knows where to look. (Or just right click and open in a new tab or window and they show up.)

Last edited by just a guy; 21st May 2013 at 03:34 AM.
  Reply With Quote
Old 21st May 2013, 03:26 AM   #12
diyAudio Member
 
Join Date: Nov 2012
Location: Melbourne
Quote:
Originally Posted by Wayne Parham View Post
What I am trying to say, actually, is that I would not sacrifice response within the pattern for a waveguide designed for a studio monitor or home hifi loudspeaker. It is still important that directivity be very uniform though, in my opinion.
Hi Wayne,

Interesting comment. Putting all emphasis on directivity sometimes has it's price.

http://www.bodziosoftware.com.au/Fre...Evaluation.pdf

Best Regards,
Bohdan
  Reply With Quote
Old 21st May 2013, 03:28 AM   #13
Face is offline Face  United States
diyAudio Member
 
Face's Avatar
 
Join Date: May 2007
Quote:
Originally Posted by Jay1111 View Post
1. On axis linearity
2. Distortion performance
3. Phase integration



4. Off axis Linearity

That's where I see uniform directivity falling on the order of importance. You can obviously have a great sounding speaker without it...
In a typical room, or especially a lively room, poor off axis linearity can make an otherwise well designed speaker, sound poor...especially outside the "sweet spot".
__________________
"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
  Reply With Quote
Old 21st May 2013, 03:33 AM   #14
diyAudio Member
 
Join Date: Jul 2003
Correct me if im wrong, but you can eq a bumpy fr, you cant eq directivity.
In that case my vote would be for directivity to be the priorty.
  Reply With Quote
Old 21st May 2013, 03:41 AM   #15
Jay1111 is offline Jay1111  United States
diyAudio Member
 
Join Date: Feb 2013
Location: AZ
Quote:
Originally Posted by Face View Post
In a typical room, or especially a lively room, poor off axis linearity can make an otherwise well designed speaker, sound poor...especially outside the "sweet spot".
This is a simple generalization and doesn't apply to every situation, or speaker. A few db more energy greater then 45 degrees off axis between 2-4 khz does not magically take over the entire room when you are listening to the on axis sound of the speakers... This idea is just getting ridiculous
  Reply With Quote
Old 21st May 2013, 03:42 AM   #16
diyAudio Member
 
Join Date: May 2006
Quote:
Originally Posted by Beau View Post
Correct me if im wrong, but you can eq a bumpy fr, you cant eq directivity.
In that case my vote would be for directivity to be the priorty.
They aren't mutually exclusive. If you change the on axis response you also change the off axis response.

Neither on or off axis needs to be flat in the raw response but after the crossover (including any contouring filters) is applied and integrated with the LF driver, both the on axis and off axis should be reasonably flat (meaning reasonably free of ripple - the off axis may or may not smoothly decrease in amplitude as frequency rises).

Last edited by just a guy; 21st May 2013 at 03:47 AM.
  Reply With Quote
Old 21st May 2013, 03:43 AM   #17
Face is offline Face  United States
diyAudio Member
 
Face's Avatar
 
Join Date: May 2007
Quote:
Originally Posted by Jay1111 View Post
This is a simple generalization and doesn't apply to every situation, or speaker. A few db more energy greater then 45 degrees off axis between 2-4 khz does not magically take over the entire room when you are listening to the on axis sound of the speakers... This idea is just getting ridiculous
Try it, you'll see. Or just listen to a pair of Wilson speakers.
__________________
"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
  Reply With Quote
Old 21st May 2013, 08:32 AM   #18
diyAudio Member
 
Wayne Parham's Avatar
 
Join Date: Feb 2004
Good points, all good points. I agree with most of what I've read here so far.

In particular, I agree that equalization of a constant directivity source provides response tailoring of all axes within the beam simultaneously.

But I would also counter that the idealized constant directivity is never really realized. We only have degrees of closeness to this ideal, which is why I often refer to loudspeakers with collapsing DI at the low end and relatively constant directivity up high as "uniform directivity" loudspeakers. They do not provide constant directivity, but what they do provide is fairly smooth and uniform. I think it's a good approach.

I would also suggest that large, abrupt directivity swings are to be avoided because they represent off-axis response abberrations. I think I gave the example of a woofer with 90 beamwidth crossed-over to a tweeter with omni radiation (180 because of the baffle). That creates a 6dB shift in the response at large off-axis angles, which is obvious and audible. But naturally smaller directivity shifts are less audible.

Another point I agree with is the matter of how this all comes into play when incorporated in a system. One of the things to realize is that the midwoofer (or midrange) and tweeter directivities blend in the crossover overlap region. So the individual directivities of each source will be partially or completely masked by the adjacent source. That makes it somewhat pointless to optimize pattern control in a region that will be blended with an adjacent source anyway.
__________________
Visit the π Speakers website
High-quality audiophile loudspeakers and kits
  Reply With Quote
Old 21st May 2013, 09:58 AM   #19
Elias is offline Elias  Finland
diyAudio Member
 
Elias's Avatar
 
Join Date: May 2003
Location: Where you live
How is uniform different from constant ?


Merriam webster: uniform = having always the same form, manner, or degree : not varying or variable


If it is not varying nor variable, it is constant !
__________________
Liberate yourself from the illusion of two speaker stereo triangle
Dipole Bass vs Monopole Bass Stereophonic Sound from a Single Loudspeaker 3 Speaker Linear Stereo Matrix Wavelets
  Reply With Quote
Old 21st May 2013, 10:39 AM   #20
Banned
 
Join Date: May 2008
Location: Switzerland
Quote:
Originally Posted by Elias View Post
How is uniform different from constant ?
It's the same thing People simply don't use precise wording.

What kind of directivity is that - constant or uniform?

Click the image to open in full size.
Attached Images
File Type: gif Monopole.gif (6.0 KB, 736 views)
  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
Dumb Directivity Question Patrick Bateman Multi-Way 2 23rd April 2013 02:02 AM
My S13 OB. Uniform polar response to tweeters at last! gainphile Multi-Way 12 24th February 2010 08:03 AM
A question on directivity swak Multi-Way 18 31st July 2005 03:03 PM
Improving on the LCY uniform dispersion ribbon Audiophilenoob Planars & Exotics 34 22nd July 2005 12:01 AM
where is short wiring in an amp important/ not important ? sandro600 Solid State 5 4th April 2004 03:10 AM


New To Site? Need Help?

All times are GMT. The time now is 04:42 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