Concentric Cone-Yay or Nay?

[GT]

Thanks guys for pointing me in some directionsI most likely would have never followed on my own.

But my question was specifically, about how much phase coherancy in degrees are we talking about from a good full range that two ways will never achieve? And if I've gathered what has been said correctly, that three ways will never achieve then either?

And while on the subject, anyone know what we're talking about in degrees for the mentioned coaxials by Thiel Audio and flat panels by Quad?

I don't have the specs, but with a full range the sound eminates from allmost the ideal single point source. Depending on the actual depth of the speaker cone.

Where as a most two ways the tweeter is seperate, not allways optimally placed front to back, and above the woofer.

Plus as ds21 so pointed out, corectly I might add, a two way is much more sensitive to the listeners movement. Vertical, and horizontal.

Flat panels such as Quads, in my opinion are also not correct, with no speaker box, the out of phase sound eminating from the rear of the speaker cancels out a very good portion of the bass response.

This is why the panals are usually so big to make up for some of this problem. The panals being so big, deviate from the ideal single point source.

There are so many problems with electrostats, accuracy is out of the question.

Think of it in reverse, think of a mic with more than one diaphram. Just wouldn't be the same.

Yeah a three way, will just make the above said, even more apparent.

Hope this helps.

GT

 

[ds21]

alfalfa,
WOW, to think that in a little while you'll know more than the guys at Meadowlark:

http://www.geocities.com/kreskovs/

 

[alfalfa]

Ok could not restrain myself any longer ... I am no expert on Quad speakers but I disagree with the statement that they are not a point source. Here is a link to their website that describes how they work to produce a spherical sound pressure pattern.

http://www.quad-hifi.co.uk/eslworks.htm

I agree with the other problems associated with Quads - out of phase rear wave, lack of deep bass, cant go that loud - just not the statement that they do not simulate a point source.

GT, I dont believe that the microphone analogy is valid because a microphone diaphragm is much much smaller than a speaker diaphragm. The issues and physics involved is different because of the difference in size and amount the diaphragms move. If we were discussing headphones (which are much closer in size to microphone diaphragms and in the amount they move) then I would agree with you - it makes no sense for a multi driver headphone.

 

[GT]

alfalfa,

Good morning!!

GT

 

[alfalfa]

http://www.geocities.com/kreskovs/

Thanks for the link. It is interesting to know that there, in theory, alternatives to the first order crossover for time/phase coherency. Would it be okay for me to say instead that all commercially available time and phase accurate multi-driver speakers utilize first order crossovers?

 

[ds21]

Just so you know, one of the draws of these types of speakers is because the back wave IS out of phase, and because of this eliminates alot of the side wall reflections or somthing like that, I don't know I havn't really looked into them that closely. I could give you a site to explain this too but I think you've got enough reading to do, so do I.

There's always somethng!

alfalfa, yes for now it's OK to say that

 

[alfalfa]

alfalfa,

Good morning!!

GT

Good evening GT

 

[GT]

RE,

Good morning!!

Ok, your interest is peaked about full range speakers.

Now all you have to do is go listen.

I don't care where you are, Kmart, Target, Wallmart, JUST LISTEN.

I have recomended a set at Sam Ash, or ZZounds, that may or may not be good. It's a start.

http://www.zzounds.com/a--2676837/item--EDIMA5D

The full range speakers I'm using in my studio came with a $75.00 stereo from Target. 5 1/2" short throw, in a vented box, very simple, very honest.

I really don't think you have to get exotic, it'll only cost you more money.

One more log for the fire, I think short throw speakers have better transient response than long throw, stands to reason.

GT

 

[GT]

ds21,

Good morning to you, my intuative friend!!

GT

 

[ds21]

top-o-the morning to ya

 

[mixsit]

Looks like this discussion could use some fresh meat (not mine I hope ), so here are some fresh questions and assumptions to through into this.
If distortion is to be kept to a minimum at low frequencies, cone movement must be minimized, thus driver size needs to be large. (all in relative terms)
If driver size is large, high frequency performance should suffer, including pattern control.
If even small amounts of cabinet resonance are a source of coloration and inaccuracy, with full-range drivers, what is the effect of a rather large cone producing bass and midrange excursions on high frequencies.
Some are using wave guides on their tweeter (for pattern control and loading I presume). How does that fit in with the above issue in both full-range drivers and dual-concentric.
My gut feeling is that in either case, having your tweeter vibrating in and out, or have it's surrounding baffle doing the same is problematic.
I'll site GT's example of how just a little change in tweeter orientation changes the sound.

Hey, I'm just trying to learn as I go here.

Wayne

 

[alfalfa]

If even small amounts of cabinet resonance are a source of coloration and inaccuracy, with full-range drivers, what is the effect of a rather large cone producing bass and midrange excursions on high frequencies.

If I understand you correctly, you are asking, in a single full range driver, what is the effect on highs due to the driver also having to reproduce bass and midrange frequencies. If this is your question, the answer is significant intermodulation distortion (IMD). This, as I have previously mentioned, is a major problem to be overcome in single driver designs (and I am unsure it can be overcome).

My gut feeling is that in either case, having your tweeter vibrating in and out, or have it's surrounding baffle doing the same is problematic. [/B]

Yep, a major problem to overcome in coaxial/concentric speaker design. The moving midrange cone may modulate the output of the tweeter and vice versa.

 

[Recording Engineer]

Well, what I was try to do was to get some numbers to compare to my monitors... Someone had mentioned it'd be interesting to to hear what people think of their monitors...

OK, I'll spill my beans...

Not too long ago, I started using Yamaha NS-1000Ms as mid-fields... Thanks to Bill Roberts, my cries for a solution to all my requirements for "real" monitors to use in my control room has been found!

I haven't done any measurements with mine at all, but Bill says his are +/- 0.7dB 20Hz-17kHz. No roll-off at 20Hz! They'll do 17Hz at 110dB with no resonance! They have a phase coherancy of +/- 2 degrees at crossover frq. Setup correctly, Bill says the listener experiences a phase coherancy within 5 degress and says that's unheard of! "You honestly cannot hear a single driver. The ears play huge tricks on the eyes.", says Bill Roberts.

So do the listening results match the quoted specs. and comments? From what I can tell certainly YES, in every way!!! But what do I know... I'm serious...

Eventually, I want some "real" near-fields to use a alt monitors during mixdowns... Once again, Bill to the rescue... I'm anticipating the release of his 22-year-developed 2-way near-fields. He says it will using a Morel tweeter and Bohlender/Graebener woofer, but the enclosure and crossover are his designs. From the few things he's mentioned, it will have rivaling specs. and at an insane price! He's mentioned Oct. 22 of this year to be the release date.

 

[Recording Engineer]

Oh, and I really WILL go listen to the fullrange speakers at places like you suggest... If good enough, I may even buy some to try out for further investigation... Hell, I've always been willing to give things a try...

 

[alfalfa]

RE, those yamahas are phase coherent in the crossover region (which is a good thing) but they would not be phase coherent over a wide frequency range. I am not really sure what levels of phase shift are acceptable for phase coherency but on one manufacturers website they measure their speaker as having a phase response of +-5 degrees from 100hz to 20khz (Go to www.vaf.com.au and check out the I-91 speaker and its measurements). Usually step response measurements will indicate time and phase coherency.

 

[Recording Engineer]

RE, those yamahas are phase coherent in the crossover region (which is a good thing) but they would not be phase coherent over a wide frequency range.

No. The NS-1000Ms are phase coherent at +/- 2 degrees at X frequency, and when setup correctly, are phase coherent within 5 degrees and the inverse square law is fully realized, to paraphrase Bill.

 

[alfalfa]

RE, does the ns-1000m have a flat baffle or a sloping baffle ie is the tweeter physically stepped back from the midrange and the midrange from the woofer? If the baffle is flat/vertical with the drivers are equidistant from the listener, the speaker cannot be time and phase coherent. All commercially available time and phase accurate conventional speaker designs have their tweeters further away from the listener than the midrange driver which again is further away than the woofer. It is the only way to compensate for the 90 degree phase shift associated with the first order crossovers that are used. Again I refer you to the explanation on the meadowlark site.
http://www.meadowlarkaudio.com/TC1.htm

The step response measurement would confirm if the speaker is time and phase accurate but I have not seen one of that particular speaker.

ps I have heard the ns1000m uses 2nd order (12db/octave) crossovers for both crossovers. Can you or Bill confirm this?

 

[Recording Engineer]

The NS-1000Ms have a flat baffle... Ah, but don't be so quick to judge...

As I've been saying, the biggest key here, when "setup correctly", we're talking some seiously phenomenal phase coherency! In short, this is achieved by laying them horizontal with the tweeters on the inside and giving them a degree of tow. I can give specifics if need be... Massive thanks to Bill on that too!!! Which if I remember correctly, was given to Bill by Akira Nakamura himself. [One of (?) / The (?) designer of the NS-1000Ms.] But don't quote me on that as I don't remember for sure. I'd reference my email about it from Bill, but I can't seem to find it doing a quick search.

 

[Recording Engineer]

As for the NS-1000M crossovers... You know, I've been searching high and low for info on the crossovers, but have come-up dry...

Let me see if I can get a hold of Bill and see what he says. I had actually thought about trying to get a hold of him to see if he cared comment [to bring-in another perspective] about things in this thread before I had even mentioned the NS-1000Ms, but supposedly, Bill's been very hard to get a hold of lately as he's been so busy. I'm gonna give him a try though.

 

[alfalfa]

The modified setup sounds interesting. Let us know if you find any more info or manage to get a hold of Bill.