Width of crossover region - Page 3 - 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 26th March 2006, 06:13 AM   #21
diyAudio Member
 
Join Date: Aug 2004
Location: Italy
Hi forr,
I symply constate that "official result of this scentific tests" always contraddictc listening perception of audiophile lovers.
The absurdity of this old question is evident : can a doctor affermate
that I have not pain on my head because he have made to me a perfect X-ray and the result is negative ?

about the audibility oh phase: what do they want hear with a earphone?

again, if only a few person can hear a difference, why considerate the others that do not hear? It is a paradox... can you maybe take 50
"casual" subjects on the street and to demand they can hear the difference from to say CD and SACD?? Are we crazy?
I total disagree about methodology of 99/100 of these "scientific" test.
Le Cleach is right IMHO: only a few subjects are able to detect...
life is not democratic.

Just my personal opinion, of course.

Cheers,
Inertial
  Reply With Quote
Old 26th March 2006, 06:21 AM   #22
diyAudio Member
 
Join Date: Aug 2004
Location: Italy
Charles, I agree with you...
If 99% are "lost" , I'll serch to meet the 1% !!

Inertial
  Reply With Quote
Old 26th March 2006, 10:13 PM   #23
diyAudio Member
 
Join Date: Jan 2006
Location: on the move
A few notes on x-over-regions and the audibility of phase errors...

From my experience you will have a hard time anyway reckognizing the (lack of) intrinsic phase shift of conventional x-overs. There are quite a few other effects masking the possibly audible information lying within an optimum time behaviour. The most evil fogging of spatial information to me is any kind of *stored energy issues* of which there are plenty within most (99%?) of common speaker designs.

Since any stored energy will introduce badly smeared delays to differnt frequencies - often in the magnitude of generic x-over phaseshifts or larger - one will usually not be able to reckognize the benefits of any "linear phase" system, because frequencies still do *not* arrive time aligned. This even happening on systems which appear & measure quite "time aligned" over the whole audio range and already produce a "somewhat" rectangle. Not enough, I'd like to say.

Some of the "usual suspect" causes for stored energy/delays I've always been looking into are:

- misalignment of driver's distances to listener
- driver ringing @ cone breakup (including phase breakups)
- driver ringing @ resonant freq. (tweeters & midranges)
- intrinsic ringing of any steep sloped filter circuits
- short term back reflections from cabinet (driver air flow)
- edge diffraction effects
- x-over components vibrations
- lack of rugged/stiff driver mounting
- parasitic cabinet wall resonances

So you might say "Hey, these are 20/30/50dB down from the signal!". Yes they are, but I must ask: aren't any spatial informations quite "down" compared to the full signal too? So just in case you want to experience details at, say 30dB below level within a given signal, you might want an "error level" way below these signals. Just in case...

Now the above issues are not any "must care" critera (but these actually some of my "must look at"s), and finally stored energies are far from beeing the only thingies worth considering. So your mileage will vary as will your preferences and weightings. Nevertheles I'll want to repeat: without having these (and other effects) in check, a discussion about audibility & benefits of "phase accuracy" seems quite futile.

Now the initial thread title is "Width of crossover region" and that's where I see a tight link to the above said. When thinking of a really low "error level" (not only with stored energy, but in general...), at the same time targeting to lowest possible order crossovers for your desired "phase acurrate" design, you will run into "crossover regions" covering *at least* a decade above and below the x-o-frequency.

So one of my ways of dealing with x-overs was to completely give up the term "crossover region" long ago. Any driver I look at, I will initially "implement" from about ~10Hz to ~40kHz. Then I will weight the multiple effects introduced by each driver at any frequency. (e.g. Dome tweeter at 30Hz? Cone excursion is worth a look... Dome tweeter at resonance? Top priority! Sub-woofer? Controlled performance at 5-10kHz is highly preferred.)

Now in the end it's all about listening. I might be one of the few who had the chance to mangle phase accurate multi-way systems on such a strict design level, and what can I say? The listening experience is outraging immersive. The speakers themselves completely dissapear to the ear. The just sit there as if serving not any pupose at all. Provided a decent recording (plus matching electronics) there is virtually not any sound coming out of the speakers themselves. Very irritating to the common listener. Spatial localisation especially in depth field is as frightening accurate as it can get (30-50m and more! but *only* if it's actually on the recording!). Quite some people regarding these speakers as "bad" simply because "something was missing" (hehe... missing with the speaker? or rather with the listener? Ahemm, BTW: see my signature for this too...)

Again, no one has to put this much effort into his work, but in case discussing, please do not obfuscate the (IMHO) massive importance of speaker phase / delay issues due to the fact that you are lacking knowledge of construction and/or experience with the related effects thereof.

Just my two microseconds, thanx for reading, you are now free to beat me up.

regards, redunzelizer
__________________
There is no truth. Only incomplete perception...
  Reply With Quote
Old 27th March 2006, 06:07 AM   #24
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
I once read about a test where they came to the conclusion that there is a small audible effect on rectangulars that were passed through all-pass filters. Now it makes me wonder how scientific a comparison between rectangulars (i.e. a static signal) via headphones and music via speakers really is ???????

I belong to the camp who thinks that transient response matters. But I am also aware that this is not the only one and not the most important parameter.

Regards

Charles
  Reply With Quote
Old 27th March 2006, 06:24 AM   #25
diyAudio Member
 
David Gatti's Avatar
 
Join Date: Mar 2004
Location: Melbourne, Australia
Everyone has to form their own opinions regarding the compromises they're prepared to make when designing a loudspeaker.
I personally believe a true high-fidelity speaker should be as phase accurate as possible.

http://phasecoherent.com/index.htm
  Reply With Quote
Old 27th March 2006, 09:40 AM   #26
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
redunzelizer wrote:

Quote:
Just my two microseconds, thanx for reading, you are now free to beat me up
With pleasure !

Fun aside: Can you give more details about your system like drivers used, active/passive, what cabinet precautions used for minimising stored energy ...... ?

Regards

Charles
  Reply With Quote
Old 27th March 2006, 05:58 PM   #27
diyAudio Member
 
Join Date: Jan 2006
Location: on the move
Quote:
Originally posted by phase_accurate
Fun aside: Can you give more details about your system like drivers used, active/passive, what cabinet precautions used for minimising stored energy ...... ?
I have to ask for you understanding that I'm not able to give you every explicite detail, since I'm somewhat under non-disclusure. Nevertheless I will try to explain some of the basic principles involved with such a "strict" design.

The basic description of that system is:
Passive 4-way, point-symmetric electrodynamic transducer with
1x Tweeter: 28mm dome
2x Midrange: 54mm dome
2x Midbass: 17cm, high excursion
2x Woofer: 25cm, high excursion

Tweeters & Midranges with 6++mm custom machined front plates, mounted for closest possible distance. Plates designed for both extreme stiffness and controlled on/off-axis responce. Mid & tweeter plates not only screwed onto cabinet but also onto (into) each other. Machined basket enforcement rings for midbass & woofers. Additional mounting holes drilled into basket for midbass & woofers. All drivers mounted twice, both at front plate/basket, as well as at the magnet. (Yes, even the tweeter.)

Compound cabinet walls (stiff case plus heavy damping material) with lots of cross braces. Sand-filled sandwich was in consideration too, but with cabinet resonance character mainly defined by design & bracing, and second only by material, you may chose for your convenience. Then, weight! The more the better. Think in "tenths of tons"...

Driver center alignment in correlation to "sweet spot" listening position can be done by a front panel with angled level-stepping, sending/diffusing possible reflections of said steps into "uncritical" directions, away from listener and walls/floor (stealth airplane design anyone?). Gradually bent sides of cabinet to virtually eliminate any edge diffraction effects. Front panel stepping at the same time providing a thickness of 7-10cm (3-4") front plate for midbass and woofer (sorry, it happened just by accident, hehe...)

Now for something showing most important in any case: Conical rear cutouts for midbass & woofers! (that one being a wide baffle design there was room enough anyway...). Do "send away" any output from the driver's rear! Care to annihilate that output within the cabinet before it hits the cones again from the back after some time. Also, try experimenting with additional "deflection plates" within to further increase the "damping travel path" of these delayed energies. Will show even greater positive effects. Or get a dipole...

In short: stiff and damped case, most heavy, extremely rigid mechanics, controlled dispersion & diffraction.


Having (hopefully) done all that mechanical homework (which, btw, would apply the very same for any neat & budget fullrange speaker! Just look at zaphaudio's tricky W3-871 design! http://www.zaphaudio.com/archives.html ) we're back on topic: another few remarks on an x-over design for such a system:

Note that all of this stuff has been done before, but rarely alltogether within one design. Valuable thoughts & calculus can be found all over the web & in countless forii. (Although basically it would be searching needles in the haystack...)

What to care for with any such crossover in terms of "stored energy"?

Behaviour of midbass, midrange & tweeter at resonant frequencies has to be mastered. Electrical damping (Qe) of drivers limited by a conventional low-pass filter will more or less suffer badly. (Ring! Ring... midrange calling! tweeter on the other line too? Stress! Hectics! Transient panic! Damn, where is my original signal?) Additionally most existing drivers, even with driving them at zero source impedance, are somewhat underdamped already at their resonance frq. You will always have to do something about it.

So, in this case, applying some kinds of passive(!) Linkwitz-Riley transforms, thus moving "effective Fr", changing the actual acoustic Qts *within* x-over environment to suitable values, has shown mandatory. Yes, provided capable drivers, this can certainly be done within any reasonable ranges.

IMO, it's way cheaper to assign some new "acoustical effective" Thiele/Small params to a given (otherwise excellent) driver, instead of waiting for that other "dream of a driver" getting never built. Active systems can do many (but not all!) wonders for you here too, however, I'll stick to my passive versions for some reasons.

Then there are resonant peaks to be "mirrored out". Given a suitable driver, you will have to model networks compensating these in *both* amplitude and phase, thus omitting other certain kinds of ringing and coming yet another bit closer to your "acoustical design target" functions that way.

Of course there is the usual other stuff to handle: additional phase shifting wherever required, providing the actual crossover functions, chosing the appropiate quality for each part, seperate x-over enclosure, rugged parts mounting again and again, etc., etc., whatever will fit your intentions.


All these heretic x-over efforts? What for?

When having turned a former "loud"speaker into a fairly non-resonant "tranducer", not only the overall transfer function will start to behave quite like desired, but suddenly phase *relations* of any involved drivers will start to show extremely important. (10Hz to 40kHz for all drivers, remember?). For a given theoretical design (spreadsheet galore...) compared to the actual acoustical driver output (B&K, MLSSA, Osci...), the phase errors should stay well below a few degrees (a really tough one, believe me) and no more than 10-20deg within "lesser-critical" ranges.

It's "as easy as that"...


regards & greetings from within the haystack,

redunzelizer
__________________
There is no truth. Only incomplete perception...
  Reply With Quote
Old 28th March 2006, 12:14 AM   #28
forr is offline forr  France
diyAudio Member
 
forr's Avatar
 
Join Date: Dec 2004
Location: Next door
Inertial
I can name, at least, three renowned scientists/engineers/researches who are very skilled in sound recording. So they know a lot about what is the sound and what affects it through the whole record/reproduction chain. I have the greatest respect for the writings of these renowned people whose theorical and practical knowledge as well as extended experience are shared by only very few audiophiles.

Phase_Accurate
--- I belong to the camp who thinks that transient response matters. But I am also aware that this is not the only one and not the most important parameter.---

The camp you belong to justifies your pseudo !
There is a general agreement that a linear frequency response must be attained before any attempt to get a good transient response from a speaker.
  Reply With Quote
Old 28th March 2006, 12:23 AM   #29
diyAudio Member
 
Join Date: Jan 2006
Location: on the move
Quote:
Originally posted by forr
There is a general agreement that a linear frequency response must be attained before any attempt to get a good transient response from a speaker.
Please take a look at the according time/frequency dependencies. In case you are seriously heading for a (near) transient-perfect response, linear frequency response will show up by itself. You just can't avoid that happening anyway!

In other words, I personally do *only* have to care for linear frequency response in case I am intentionaly building a conventional speaker with too few drivers and/or (then naturally occuring) all-pass phase shifts. Which is happening in times and is fun as well. But otherwise...
__________________
There is no truth. Only incomplete perception...
  Reply With Quote
Old 28th March 2006, 06:33 AM   #30
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
Quote:
In other words, I personally do *only* have to care for linear frequency response in case I am intentionaly building a conventional speaker with too few drivers and/or (then naturally occuring) all-pass phase shifts. Which is happening in times and is fun as well. But otherwise...
Care has to be taken not to mix things up. While a linear frequency response is necessary for good transient performance - a linear frequency response alone does not guarantee a good transient response.

The reason for this is that also non minimum-phase systems can have perfect linear frequency response (like LR 4 transfer functions).

Otherwise I must admit that your design seems to be a very careful and competent one.

Regards

Charles
  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
Most linear region of Mosfets ? Bernhard Solid State 15 11th March 2009 04:00 PM
Crossovers in the 1KHz region angel Multi-Way 20 3rd April 2005 08:52 PM
DVD HACKS (not region codes : ) ) magic_mat Parts 2 1st February 2005 11:34 PM
Dvd Free Region joz Solid State 0 6th April 2004 11:13 AM


New To Site? Need Help?

All times are GMT. The time now is 02:42 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