Phase-alignment based method of designing multi-way speakers - 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 15th May 2012, 10:31 AM   #11
Juhazi is offline Juhazi  Finland
diyAudio Member
 
Juhazi's Avatar
 
Join Date: Mar 2007
Location: Jyväskylä
PRTG - are you going to create such a speaker? Please go on and show us your results!
__________________
AES Associate Member / My DIY speaker history: -74 Philips 3-way, -82 Hifi 85B, -07 Zaph L18, XLS10+PR/Hypex, -08 CSS125FR, -08 Hifitalo AW-7, -08 TangBand FR, -09 MarkK ER18DXT, -13 PPSL470, -13 AINOgradient
  Reply With Quote
Old 15th May 2012, 10:59 AM   #12
tvrgeek is offline tvrgeek  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Md
A bit harsh here. Using DSP tools like UE from Bodzio, it is possible to build a system that would be phase coherent by preprocessing the signal. In theory, with a boat load of parts, it is possible to do it passively. I mean hundreds of passive parts to build delay lines and various all pass networks.

So, let's look at the OP's basic approach and see the merit in his ideas. His basic premise is not to ignore problems because they are difficult, but to attempt to deal with them. Quite reasonable.
  Reply With Quote
Old 15th May 2012, 02:10 PM   #13
diyAudio Member
 
LafeEric's Avatar
 
Join Date: May 2010
Harsh indeed. A good example is the What is the ideal directivity pattern for stereo speakers? thread - 2200+ posts and counting. Clearly things are not as clear cut as some would make out, even over seemingly simple aspects of speaker building. So PRTG has a method that works for him and has spelled it out - is that any reason to trash the guy? I commend his efforts, whether I agree with them or not. Personally, I feel I have something to learn from everybody - which isn't to say I think I know nothing.

I too would be interested to see the results of this method - whether or not I had certain technical or editorial prejudi... err, misgivings.

PRTG - I also commend your patience and restraint.

Last edited by LafeEric; 15th May 2012 at 02:15 PM.
  Reply With Quote
Old 15th May 2012, 02:36 PM   #14
diyAudio Member
 
lduarte1973's Avatar
 
Join Date: Feb 2009
Location: Lisbon
Quote:
Originally Posted by tvrgeek View Post
A bit harsh here. Using DSP tools like UE from Bodzio, it is possible to build a system that would be phase coherent by preprocessing the signal. In theory, with a boat load of parts, it is possible to do it passively. I mean hundreds of passive parts to build delay lines and various all pass networks.
would something like minidsp do ?
__________________
Hey ! just because i´m getting bald doesnt mean i cant like hair metal
  Reply With Quote
Old 15th May 2012, 02:47 PM   #15
diyAudio Member
 
vacuphile's Avatar
 
Join Date: Apr 2011
Location: Seaside
Quote:
Originally Posted by CharlieLaub View Post
The above statement is rubbish. More than that, it's essentially impossible.

-Charlie

Charlie, it is very well possible to align the phase shift of the different drivers around Xover so that they show the same shift at any given frequency. As a matter of fact, it is not only possible, it is necessary. Linkwitz' site explains how and why. The above statement is therefore not rubbish, but an insight to behold.

There is general confusion between aligning the phase shift of the different drivers in a loudspeaker around xover(phase coherent, necessary), and preventing any phase shift by using all pass filters to correct for group delays introduced by the Xover, like the Urei of long gone times. I also have a Tannoy little red monitor that has such an all pass filter section in the Xover. This is expensive, difficult and in my view unnecessary. The ear can cope with a couple of complete phase rotations between 20Hz and 20Khz, without really noticing it.

Then one remark about the necessity to have the same filter order for high and low. Actually, it depends. Don't forget that drivers exhibit phase shift too when their output goes on a downward slope for mechanical reasons. So, you really have to measure the phase behaviour of the drivers around Xover to come to any definitive conclusions.

Otherwise, I think PRTG did a commendable job posting this.

vac

Last edited by vacuphile; 15th May 2012 at 02:51 PM.
  Reply With Quote
Old 15th May 2012, 03:12 PM   #16
diyAudio Member
 
Join Date: Mar 2007
Location: California
Quote:
Originally Posted by PRTG View Post
A small remark regarding the introductory statement - it's in quotes, so it's not mine. I took it as a guideline for a challenge to try to get as close as possible and find whether there is a truth in it.

Thanks for all the opinions so far, lets summarize what we have in to do list:

Building loudspeaker with acoustically aligned drivers and two types of filters - one using phase alignment method and second using traditional method. Then making:

- comparative F response on-axis and off-axis measurements;
- blind listening tests.

Anything else?
I think that you will find that "traditional" methods already phase-align drivers where it counts. This is not considered "too difficult to understand" as you postulated - plenty of DIY loudspeaker designers do this all the time, every time. You do not need a waveguide, or need to use a certain baffle width, resort to exotic passive networks, etc. but rather you can do this with any loudspeaker if you know what you are doing and you have good design tools and accurate driver measurements. Practically speaking, it is only necessary to phase align around the crossover point. Once one of the drivers is down about 40dB or more, the relative phase of it and other drivers just isn't important. So, phase alignment and phase tracking IS important, just not everywhere as stated in the passage you quoted in the beginning of your opening post.

Once you are away from the crossover region, so that you have a single driver dominating the loudspeaker's output, then it's phase doesn't really matter. The only phase related quantity that I could see being of any importance is the group delay, which must be kept within reasonable limits (e.g. under about 3 ms) between 250Hz and 2500 Hz. A small number of studies (by telephone researchers) found that people could detect more group delay above these levels and within these frequency limits.

Also, as brought up by a recent post, you can use a system like the UE from Bodzio to implement frequency flattening and phase linearizing filters, however, this is still only carried out between some limits, and not "everywhere". I really do not think that you will be able to pull anything like this off using passive filters! Even if you could design such a series of networks, the losses would be enormous. But keep in mind that phase angle varies with distance from the source. Let's say that you have gotten everything perfected (using the UE) at some point in space - as you move away from that point and off axis, the relative phase of all the drivers changes because the distances to all the drivers to the new point in space has now changed and now you have phase related frequency response deviations.

So, basically I am still asserting that the quote used to start your initial post is not correct. I suggest that you look at Jeff Bagby's Passive Crossover Designer (a free software). There are many posts on the TechTalk forum at parts-express.com that provide examples of excellent loudspeakers designed with this software that have good phase match/tracking in the crossover region. Many of these have received excellent reviews by other DIYers when the speakers were demoed at shows and events.

-Charlie
  Reply With Quote
Old 15th May 2012, 09:08 PM   #17
tvrgeek is offline tvrgeek  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Md
Quote:
Originally Posted by lduarte1973 View Post
would something like minidsp do ?
Sorry, don't know anything about it. Check out UltimateEqualizer. I have not used it, but I use SoundEasy. I have no reason to doubt what he says. Of course, it is Microsoft based, so trying to do real time streaming and processing with a non-real time OS is always dicey. Oh for the days of OSF-RT. I can't even get my emu-1616 to play a CD without crashing. I see an m-audio 610 in my future.
  Reply With Quote
Old 15th May 2012, 09:11 PM   #18
PRTG is offline PRTG  Latvia
diyAudio Member
 
PRTG's Avatar
 
Join Date: Mar 2005
Location: Riga
Send a message via Skype™ to PRTG
Quote:
Originally Posted by CharlieLaub View Post
Practically speaking, it is only necessary to phase align around the crossover point. Once one of the drivers is down about 40dB or more, the relative phase of it and other drivers just isn't important. So, phase alignment and phase tracking IS important, just not everywhere as stated in the passage you quoted in the beginning of your opening post.
Isn't that right only for filter orders above third, which means taking active filtering path as mandatory? This may seriously doom financial perspective for SET amp guys.

I really appreciate potential of DSP and MiniDSP was the next thing I was planning to try. Still some minimalistic passive filtering approach with best-effort level of coherent phase would be handy for comparison by then. Just to be sure.

My article actually started with reference to another one which I felt hasn't covered resonance damping and notch design as being too complex and underestimating value of measurements. With plenty of tools available.. Why? I hope my addition would create nice and informative guide for those that want to take the harder part by building passive, doing it by the right means and order and getting results close to excellent, still without much of a strain.

Regarding phase angle variation with distance from the source - you're right. That's why I prefer single drivers for near-field listening. I'm also aware that even single driver has the problem of phase shifts caused by same frequencies radiating from different parts of a single driver.

So my obviously idealistic introductory citation could be easily perceived as too ambitious and lacking insight. Personally I like idealistic statements. They open some freedom of thought and experimentation and sometimes raise some friction between the obvious needs and limitations of the known ways of how to fulfill them. I understand that you were actually trying to help, and I appreciate that, so no offence is taken.
  Reply With Quote
Old 15th May 2012, 09:12 PM   #19
tvrgeek is offline tvrgeek  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Md
I find LTSpice to be quite informative when cascading multiple networks. You can then add the phase response of the driver if you measured it with SoundEasy. I was having issues with a mid where I had a BSC, 3 order electrical, and a notch. The plot clearly showed why I was having problems. 90 degrees at the crossover frequency.
  Reply With Quote
Old 15th May 2012, 09:29 PM   #20
tvrgeek is offline tvrgeek  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Md
There is only one absolute correct statement. That is the consultant's answer to everything. No, it is not "42". That's the answer to everything.

"It depends"

Anyway, it has been long determined we have no sensitivity to phase shift over frequency. The issue here the OP is correctly addressing is the issues of shift across the driver overlap region. If by complex networks or DSP, the phase response is flat, then you will have no issue IF IT IS COAXIAL AND TIME CORRECT. Otherwise, still more problems. Then we have to deal with the distortion from the networks. This is of considerable concern for my with my wife's ultra sensitive hearing. Experiments show a low pass followed by a notch filter at tweeter breakup help. All this is the argument the single driver camp uses. Too bad I have never heard a decent single driver. ( Ok, My Grado's are darn right decent.)
  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
Designing a LM1875-based amp frasco Chip Amps 39 19th January 2012 05:30 AM
Phase alignment of the isobaric design Jimmy DIY Multi-Way 14 1st April 2006 03:42 PM
Audio phase scope and multi segment meters rockstudio Instruments and Amps 3 31st January 2006 11:00 PM
Designing a box based on room dimensions StevenLB Subwoofers 1 14th December 2005 08:56 AM
Crossover design mojo...phase alignment with a hint of zobel? camusmuse Multi-Way 0 6th March 2004 12:12 AM


New To Site? Need Help?

All times are GMT. The time now is 03:50 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