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Old 1st February 2013, 07:12 PM   #11
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Originally Posted by wolf_teeth View Post
The reason the spread is needed is it produces a peak in the summation if 1st orders are used at the same frequency. BW1 do not sum flat without spread. Peak if not far enough, hole if too far, there is a sweet spot.

I don't know that the experiment listed has anything to do with beat frequencies at all. Still- great discussion thread!

Later,
Wolf
Hi Wolf _ teeth , thanks for your reply.
That is true what you say.
How far apart would you normally you suggest this might happen?.
If the drivers are operating within their natural piston range, and not being used into areas that might make the frequency responses irregular and peaky this gap or spread can be quite wide .
Cheers Ian
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Old 1st February 2013, 07:25 PM   #12
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Originally Posted by tvrgeek View Post
Are you sure you are not just realizing that no one I am aware of has ever recorded a piano realistically, let alone reproduced it in any speaker? I have only heard one reproduced instrument that almost, again almost, could convince me it was live. It was of an upright bass, half-track master tape, etc. Recorded music can be fantastic, but it sounds nothing like live. I am not sure it ever can.
That's a very valid point that you have made.
We all know that there isn't perfection in this pursuit, but whilst the recording engineers and studios use very poor quality monitors to mix upon I think that we may well have had to be listening to the by-product of that.
I have designed nearfield monitors that are in use in some professional studios in Florida some years ago. There is also one of my 7.1 wall soffit mounted systems used in the executive listening suite in Warner Music New York. Both use my design methods.

Live music is my benchmark. It is also very rare that an orchestras violin section can be reproduced realistically. It usually is balanced so forward in the mix, that just sends amplifiers and speakers in to a real oscillation sometimes.

Cheers Ian
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Old 2nd February 2013, 01:57 AM   #13
AllenB is offline AllenB  Australia
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Originally Posted by IanKnight View Post
I was not happy with the crusty/fizzy midband despite the drivers being smooth in response in that area and capable of reproducing the frequencies well.
I decided to start pulling the crossover frequencies apart,
I suspect we've all battled with this one. For quite some time I was perplexed, with the thought that woofers and tweeters were just not meant to be together.

It is interesting to hear about another's journey through this.

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Originally Posted by IanKnight View Post
to rely on measurements first then tweak until the measurement is correct.
I feel that the relative dispersion of the drivers and related effects, as it is not always considered, probably accounts for the larger share of this discrepancy. On the other hand the absolute dispersion of a system also has an effect which could be inadvertently attributed to a crossover.

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The beating and reinforcement of certain frequencies will occur according to the crossover frequency points are imposed on each driver and what slopes are used.
I could be misunderstanding something here. Do you mean cancellation and reinforcement? Ordinarily the phase from a tone from each of two drivers will remain apart, ie they will track together with a certain offset and won't cross each other over time.

I agree that crossover changes can affect the phase relationship of two drivers. Regardless of the slope you chose for either driver, the apparent gap or slope or whatever, the phase relationship can be set arbitrarily.

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Originally Posted by speaker dave View Post
An interesting phenomonon with pianos is that the overtones of a string are somewhat inharmonic (not exact multiples)
There is a lot of wonderment inside a piano This is surely a field where art is valid and even encouraged.

May I ask about the strings that are made with nested coil-overs, whether their mechanical complexity is responsible for producing the non-harmonically related overtones?
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Old 2nd February 2013, 09:57 AM   #14
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Originally Posted by IanKnight View Post
Hi Wolf _ teeth , thanks for your reply.
That is true what you say.
How far apart would you normally you suggest this might happen?.
If the drivers are operating within their natural piston range, and not being used into areas that might make the frequency responses irregular and peaky this gap or spread can be quite wide .
Cheers Ian
Drivers are never flat and ultimately won't be best fit for a translatable argument. The loudspeaker Design Cookbook covers BW1 xover "spread factor" with a xover part-value multiplier. Top it off with lobing,
dispersion, Baffle-step, and harmonic distortion signatures, and you are really going back to zero.
Later,
Wolf
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Old 2nd February 2013, 10:38 AM   #15
AllenB is offline AllenB  Australia
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The Loudspeaker Design Cookbook had me thinking that crossing where the drivers are at 4.5 to 5dB down would be ideal, but I wouldn't say that in general now. The fact is that although the ideal first order crossover is 3dB hot at the most, when you figure in the nulls the power averages to flat in the vertical plane. Furthermore, if you maintain the 90 degree phase difference between the drivers on axis, they'll be flat there.

This would lead me, if all else is as stated, to look to the horizontal planes among other factors.
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Old 2nd February 2013, 03:14 PM   #16
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Originally Posted by AllenB View Post
I suspect we've all battled with this one. For quite some time I was perplexed, with the thought that woofers and tweeters were just not meant to be together.

It is interesting to hear about another's journey through this.


I feel that the relative dispersion of the drivers and related effects, as it is not always considered, probably accounts for the larger share of this discrepancy. On the other hand the absolute dispersion of a system also has an effect which could be inadvertently attributed to a crossover.


I could be misunderstanding something here. Do you mean cancellation and reinforcement? Ordinarily the phase from a tone from each of two drivers will remain apart, ie they will track together with a certain offset and won't cross each other over time.

I agree that crossover changes can affect the phase relationship of two drivers. Regardless of the slope you chose for either driver, the apparent gap or slope or whatever, the phase relationship can be set arbitrarily.

There is a lot of wonderment inside a piano This is surely a field where art is valid and even encouraged.

May I ask about the strings that are made with nested coil-overs, whether their mechanical complexity is responsible for producing the non-harmonically related overtones?
Hi Allen,

I think the point that you raise about the relative dispersion could be a major factor in the integration process of the the 2 drivers.
I have always felt that a big woofer and a (small) tweeter unit couldn't live together properly either!.
I have been doing all sorts of things to try ascertain what is actually happening when trying to tie-in the two drivers at certain frequencies. This is why I am working on the basis that to give anything in the crossover region a chance of reproducing correctly then for starters we should not be pushing the drivers out of their natural piston range. EG. getting too close to the mechanical breakup in woofers, or conversely getting to close to FS in tweeters.
Although the response is never flat from a driver, at least it is smooth, and working morenaturally in the mechanical and electrical sense.
The dispersion characteristics also become more predictable for each driver.

Yes I do mean the Cancellation and Reinforcement !.
Yes, as you say, the phase relationship can be set arbitrarily. according to the crossover that is used, but just as tilting the speaker back, or altering the plane of the tweeter to so called time align the units , I thinks that we perceive is quite different once the correct spacing of frequencies has been achieved even if both the woofer and the tweeter have identical phase characteristics such as 1st order.

Cheers Ian
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Old 3rd February 2013, 12:14 AM   #17
AllenB is offline AllenB  Australia
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Keeping away from the woofer breakup region will also be keeping away from narrowing dispersion. A dome tweeter has wide dispersion and so side reflections would otherwise be thin at the crossover region.

Do you like anything about the sound of the mid/treble produced by a good smaller full range driver, apart from them being light on the upper treble?
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Old 3rd February 2013, 08:56 AM   #18
lolo is offline lolo  France
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Quote:
Originally Posted by IanKnight View Post
Hi Allen,

I think the point that you raise about the relative dispersion could be a major factor in the integration process of the the 2 drivers.
I have always felt that a big woofer and a (small) tweeter unit couldn't live together properly either!.
Who says they really can? It's just a compromise.. Ideally one would want a two way crossed low, at the schroeder room's frequency and one driver going up all the way from there. But, how do you keep distorsion and dispersion under control, and still manage decent SPL? Has anybody made such a driver yet? Constant directiviy has been THE big thing these last few years.
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Old 3rd February 2013, 10:03 AM   #19
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Originally Posted by AllenB View Post
Keeping away from the woofer breakup region will also be keeping away from narrowing dispersion. A dome tweeter has wide dispersion and so side reflections would otherwise be thin at the crossover region.

Do you like anything about the sound of the mid/treble produced by a good smaller full range driver, apart from them being light on the upper treble?
I haven't tried any full range drivers to be honest.
But I agree with what you say about keeping away from the woofer breakup zone. It promotes a lot of things that can be used to advantage when dealing with integrating the tweeter. In fact I have an article regarding this on my website. The articles are intended as an introduction to the way I design speakers.

http://http://knightloudspeakers.com...eakup-zone.pdf

If you are interested just sign up to the website it's free!.

Cheers Ian
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Old 3rd February 2013, 10:06 AM   #20
Elias is offline Elias  Finland
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Originally Posted by IanKnight View Post
For the past 15 years or so I have been researching and developing my interest in the part that the basilar membrane plays in how we interpret the sound of the loudspeaker.

Vau, that's quite a long time to focus on basilar membrane only

You may have found out that it serves as a prefilter, and the most interesting stuff on sound perception happends in the modulation domain in time-frequency-amplitude space at the deeper parts of auditory chain.

If you find interest, check my 'basilar membrane' wavelets aka Bark wavelets on my home page.


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