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Old 1st November 2010, 01:35 PM   #4911
doug20 is offline doug20  United States
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Quote:
Originally Posted by ScottG View Post
Yes, it's very much about choosing your compromise..

But what is "better" directivity?

Many designs with "domes" are often very uniform in their polar response. The exceptions are classic "two-ways" with a larger diameter midbass coupled to a 1" or smaller dome tweeter, and even then the usual loss in pressure off-axis between 1 kHz and the typical 2-3 kHz range can often achieve an increased sense of depth that often is more natural sounding (..and is found in better implementations that are essentially "flat" horizontally in the same freq. region).

Is *increased* directivity an advantage, and if so why?

Can you achieve that same advantage through other means?

Might there be *disadvantages* to a design that has an increase in directivity?


And particularly:

In the Raptor - isn't there the possibility that what people liked about had little if anything to do with it's polar response? In fact, perhaps people liked the design *despite* it's polar response.


Good questions, First, Domes absolutely suck for my applications. They have limited SPL and limited off axis response. I have no need for them whatsoever any more.

Waveguides/horns give the control needed and they also handle the dynamics better then any other tweeter choice so there is no other way to meet my application needs.

I have never read where directivity is a disadvantage, I think as time goes on more manufacturers will fix their off axis response because they are starting to realize how important it is. There will still be all types of designs and all those designs will have a fan base. Remember, people are not clones of each other and to think that there is only one superior design does not make sense at all in the real world.

Why people like the Raptor is not important to the directivity question, its important to the simple fact that its a 1.5" CD that measures well and sounds very good. It was using a specific design to counter Dr. Geddes too generalized "all > 1" CDs have bad responses".
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Old 1st November 2010, 01:51 PM   #4912
gedlee is offline gedlee  United States
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Quote:
Originally Posted by doug20 View Post
Again, its fine to like accurate measurements (I do) but lets not think that the only good speaker is an accurate design based on ONE philosophy. There are many different designs for different applications, there isnt one design that is superior to all others since there is not a design that fits all the variables people could want.

Remember speakers are no more then furniture to most people there is no need for superior design. Just a design that fits the specific needs of that individual.
For any given application there will be one and only one "optimal" solution. I, like most experts who have studied this situation, believe that accuracy IS the key. Subjective impressions are fleeting and unstable (especially when not blind), so to me the most accurate is the best. Any other position is hard to support with anything objective, only:

"Sounds good to me, so what does it matter?"

Fine, if thats how you want to view the situation - it's not my point of view that is for sure.
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Old 1st November 2010, 01:52 PM   #4913
AllenB is offline AllenB  Australia
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Originally Posted by ZilchLab View Post
Toole teaches that it is smooth and uniform, tracking the axial response.
The question may be: do we want our reverberant field to sound flat, or should we make some timbreal adjustments.

I suspect we may be able to adjust the timbre of the reverberant field without too much effect on the perceived timbre on the whole, since we have clearly delineated what we want from a speaker, where there is (hopefully) very little in between the direct field and the late reverberant field.

I'm sure some of us know the sound of a small single driver on a conical waveguide, that beams at the top.

I'd like to try it the other way and increase the power response toward the top end. Short of designing for increasing dispersion, I can't see how this could be done unless on axis was in a partiall null.
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Old 1st November 2010, 02:22 PM   #4914
doug20 is offline doug20  United States
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Originally Posted by gedlee View Post
For any given application there will be one and only one "optimal" solution. I, like most experts who have studied this situation, believe that accuracy IS the key. Subjective impressions are fleeting and unstable (especially when not blind), so to me the most accurate is the best. Any other position is hard to support with anything objective, only:

"Sounds good to me, so what does it matter?"

Fine, if thats how you want to view the situation - it's not my point of view that is for sure.
Im 100% in the DBT camp, I have been doing the tests since University 22 years ago.

Have you done a controlled listening test with a 1.5" vs a 1" CD?? Again, I will post that its important to have accuracy and measurements but at the end of the day does anyone really know how much audible difference there is between the two in a proper listening test? If there isn't much difference they why all the stubborness to be chase perfect measurements or to post that "all responses are horrible" type blanket statements?

I always go back to think BOSE knowing they sound like crap but they also do a lot of R&D on what sound sells and they stopped fussing over the unimportant stuff a long time.
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Old 1st November 2010, 02:30 PM   #4915
dlr is offline dlr  United States
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Originally Posted by doug20 View Post
I always go back to think BOSE knowing they sound like crap but they also do a lot of R&D on what sound sells and they stopped fussing over the unimportant stuff a long time.
Unimportant to whom? The marketing department?

Dave
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Old 1st November 2010, 02:41 PM   #4916
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Originally Posted by Robh3606 View Post
OK but what's happening up top?? Here is the DI curve for the JBL Screen Arrays you mentioned. In a perfect world the directivity would be a straight line. You can see that the bass starts at a very low number and then the DI increases as you change over to the waveguide in the mids and top end. Take a close look above 2K or so. The number is getting higher and above 10K it starts an abrupt change, you can see the hook at the end.

A CD waveguide would have a straight curve like the older 2360 Bi radial horns

http://www.jblpro.com/pages/pub/components/23606566.pdf

That horn family are 2" throats and you can see above 10K they simple loose control.

The on axis response is another matter entirely and can be flat either by the increasing DI from the horn, Electrical compensation or a combination of both.

Rob

Note that the 2360A has been replaced by the 2360B.

http://www.jblpro.com/catalog/suppor...=174&doctype=3

There is a slight improvement in the 16kHz polar but the main improvement is in response smoothness at 1kHz. I'd say that, outside of this forum, most of the users of 2" throat drivers use them for their very necessary increase in power output. 500 or 800Hz crossover points also work very well with 15 inch woofers in a theater environmnet. There are plenty of 2" throat drivers that work well to 15-16kHz so there is little compromise at the top end.

I've had good results with this system in Digital Cinema applications. I haven't tried the newer version screen array series but there performance parameters look pretyy good also. My impression is that the newer generation Optimized Aperature Waveguides are a different compromise with a little less emphasis on widest HF polars.

And the patented Screen Spreading compensation....marketing making lemonaid froma a bunch of sour lemons.

David
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Old 1st November 2010, 02:52 PM   #4917
doug20 is offline doug20  United States
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Originally Posted by dlr View Post
Unimportant to whom? The marketing department?

Dave
Unimportant to simply selling speakers.

The discussion is talking about accuracy and its importance. Importance it seems is just a highly subjective opinion just like BOSE opinion on what sells.
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Old 1st November 2010, 02:55 PM   #4918
doug20 is offline doug20  United States
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Originally Posted by speaker dave View Post
Note that the 2360A has been replaced by the 2360B.

http://www.jblpro.com/catalog/suppor...=174&doctype=3

There is a slight improvement in the 16kHz polar but the main improvement is in response smoothness at 1kHz. I'd say that, outside of this forum, most of the users of 2" throat drivers use them for their very necessary increase in power output. 500 or 800Hz crossover points also work very well with 15 inch woofers in a theater environmnet. There are plenty of 2" throat drivers that work well to 15-16kHz so there is little compromise at the top end.

I've had good results with this system in Digital Cinema applications. I haven't tried the newer version screen array series but there performance parameters look pretyy good also. My impression is that the newer generation Optimized Aperature Waveguides are a different compromise with a little less emphasis on widest HF polars.

And the patented Screen Spreading compensation....marketing making lemonaid froma a bunch of sour lemons.

David
Thanks, The smoothness at 1KHz and 500Hz XO stuff is very important, more important then directivity up past 10KHz and its why I disagreed with the statement " > 1" CD have a bad response in the higher frequencies" Its not a general statement but its just one opinion.

If we can get directivity upto 10KHz, it can be damn good already, add to that what Zilch posted about Screens and directivity. Then > 1" CD choices can work pretty good in our HT environments.

If someone can give me a DIY build with XO at 600Hz, smoothness at 1KHz and directivity upto 15KHz then Im ready to buy the drivers

Last edited by doug20; 1st November 2010 at 02:58 PM.
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Old 1st November 2010, 02:59 PM   #4919
gedlee is offline gedlee  United States
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Originally Posted by AllenB View Post
The question may be: do we want our reverberant field to sound flat, or should we make some timbreal adjustments.

I suspect we may be able to adjust the timbre of the reverberant field without too much effect on the perceived timbre on the whole, since we have clearly delineated what we want from a speaker, where there is (hopefully) very little in between the direct field and the late reverberant field.

I'm sure some of us know the sound of a small single driver on a conical waveguide, that beams at the top.

I'd like to try it the other way and increase the power response toward the top end. Short of designing for increasing dispersion, I can't see how this could be done unless on axis was in a partiall null.
I think that this question has been well researched and the data points in the direction of a slightly falling direct response with a parallel falling power response. This is the way of nature and it only seems logical that it is what we perceive as natural.

An increase in HF power response does not seem to have any supporting evidence.

Does all this make a difference? Above 10 kHz most certainly not, and above 8 kHz its unlikely. As Dave points out, most people use larger format compression drivers for power handling and sometimes a lower crossover point. I don't need the power handling, and the crossover point is dictated by the woofer and a good 1" has no trouble doing this. So what is the advantage of a larger format in a home theater application? They are certainly far more expensive, larger and heavier. I suspect its mostly bragging rights - I'm just not into that kind of design goal. Perhaps some lower thermal distortion due to the larger voice coil? Maybe, but again to what extent is this a problem in a 1"? Too much audiophile audio design is done on the principle of "because it is there!".

Last edited by gedlee; 1st November 2010 at 03:02 PM.
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Old 2nd November 2010, 02:39 AM   #4920
JZatopa is offline JZatopa  United States
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Just curious if anyone has had a chance to listen to the the Thor and gedlee's speakers. They are two different ways of doing the same job but I am curious to hear how they compare considering these two kits seem to be the top of the DIY kits available today.
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