Impertinent half serious question...

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bdp24

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Re: Impertinent half serious question...
« Reply #80 on: 15 Feb 2017, 10:53 pm »
There are a pair of LS6 on Audiogon right now, asking price $1700, located in Napa California.

aceinc

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Re: Impertinent half serious question...
« Reply #81 on: 15 Feb 2017, 11:10 pm »
Napa is a bit of a hike, from sunny SoFla.

danvprod

Re: Impertinent half serious question...
« Reply #82 on: 15 Feb 2017, 11:33 pm »
Those ones on eBay are really nice looking.

S Clark

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Re: Impertinent half serious question...
« Reply #83 on: 16 Feb 2017, 12:00 am »
There are a pair of LS6 on Audiogon right now, asking price $1700, located in Napa California.
What?  I'm sorry but that's just crazy.  I've been to enough RMAF's and been in enough high end living rooms to know that those are not common speakers, yet they are priced like a set of high end book shelf speakers???
I agree they aren't the easiest to place, and need space, but holy cow!!!  Seventeen hundred bucks?  Where else can you find speakers that were at the top of all speakers displayed at a major show about 10 years back.  I just shake my head.

aceinc

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Re: Impertinent half serious question...
« Reply #84 on: 16 Feb 2017, 01:33 am »
The ones on Audiogon, and E-bay are the same ones;

https://www.audiogon.com/listings/full-range-av123-ls-6-speakers-lowest-price-ever-2017-02-02-speakers-33193-miami-fl--2

If anyone wants them, I can pick them up and store them in my living room, until you can come get them.  :green:

Danny Richie

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Re: Impertinent half serious question...
« Reply #85 on: 16 Feb 2017, 01:52 am »
Man, that is a crazy great deal for someone.

aceinc

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Re: Impertinent half serious question...
« Reply #86 on: 16 Feb 2017, 03:12 am »
So if I were to use the 16 of the 4" HiVi drivers and something similar to 8 of the Neo 8s, what would the baffle shape look like?

Would there be a wing like the Nx-otica? If there was a "wing", could it be 90 degrees?

It looks like the drivers would fit on a 9" to 9-1/2" baffle.

The idea would be to mate it to the OB subs I am building. So I don't think it needs to handle any frequencies below 100hz, which I think makes a difference in the baffle/wing design.

Paul

Danny Richie

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Re: Impertinent half serious question...
« Reply #87 on: 16 Feb 2017, 04:43 am »
You'll have to shape the baffle and side wing to be like the one I designed for Mockingbird Audio.

http://mockingbirddistribution.com/mockingbird-audio-lsx-speaker-system/

aceinc

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Re: Impertinent half serious question...
« Reply #88 on: 16 Feb 2017, 07:16 pm »
Impressive looking speakers. Impressive price. Hopefully I can achieve a large fraction of the performance at a small fraction of the price.

I assume the depth of the side wing is based on the low frequency that you are trying to get to. If I was looking for a 120hz cross to the sub, how big should the wing be?

Danny Richie

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Re: Impertinent half serious question...
« Reply #89 on: 17 Feb 2017, 02:57 pm »
I assume the depth of the side wing is based on the low frequency that you are trying to get to. If I was looking for a 120hz cross to the sub, how big should the wing be?

The lower you can cross them to the subs the easier it is to blend.

The LSX line sources crossed in the 80Hz range. And it seems like that wing was about 16" deep.

aceinc

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Re: Impertinent half serious question...
« Reply #90 on: 17 Feb 2017, 05:40 pm »
Will the 4" HiVi drivers I am looking at cross at 80hz?

Since my woodworking skills are questionable at best and since the baffle would be fairly narrow, would dimensional lumber (1" x 10" hardwood) be satisfactory? This way I do not need to try and veneer it.

An alternative might be;

https://b2b.parts-express.com/dayton-audio-pa130-8-5-full-range-pa-driver--295-010
« Last Edit: 17 Feb 2017, 09:34 pm by aceinc »

Danny Richie

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Re: Impertinent half serious question...
« Reply #91 on: 18 Feb 2017, 12:03 am »
Will the 4" HiVi drivers I am looking at cross at 80hz?

Since my woodworking skills are questionable at best and since the baffle would be fairly narrow, would dimensional lumber (1" x 10" hardwood) be satisfactory? This way I do not need to try and veneer it.

You can use hardwood for the baffle, but I'd also couple it to at least a thin layer of MDF.

Quote
An alternative might be;

https://b2b.parts-express.com/dayton-audio-pa130-8-5-full-range-pa-driver--295-010

The sensitivity is getting up there real quick with that one and you'd have a tough time matching the sensitivity levels to the tweeters.

aceinc

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Re: Impertinent half serious question...
« Reply #92 on: 18 Feb 2017, 12:36 am »
The sensitivity is getting up there real quick with that one and you'd have a tough time matching the sensitivity levels to the tweeters.

I was thinking;
<talking out my nose>
if I could reduce the SPL on the frequencies between 150hz and 600hz, things might be OK.
</talking out my nose>

Of course I have no idea how to build that kind of circuit, or if it could be accomplished mechanically.

aceinc

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Re: Impertinent half serious question...
« Reply #93 on: 18 Feb 2017, 04:17 am »
Danny, you have mentioned and inferred that ribbon tweeters in an array behave differently than do cone woofers in the sense that the woofer's efficiency will increase the more drivers that are added and the ribbon tweeters don't.

Can you elaborate, or point me to where I can get a better understanding of this phenomenon?

I always thought you get ~3db extra SPL per watt (in their frequency range) for every driver you threw on the fire. Is this different behavior because;
  • It is a line array?
  • The driver is a planar?
  • Of the frequency range?

My curiosity is so that I can better screen drivers without coming to you and saying, "How about this one?" 187 times.

For open baffles, I understand high QTS is good. The fellow that designed the Carver Amazings indicated the ratio between QTS and QMS linearity (whatever that means) is important. I know you say low efficiency is good, but if the old 3db per driver boost rule of thumb works for the woofers and the woofer is 80 db per watt, 16 woofers would make the efficiency 128db per watt, which is unlikely, but would require a very efficient tweeter if they didn't get any boost in multiples.

So as always, I am confused.

aceinc

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Re: Impertinent half serious question...
« Reply #94 on: 18 Feb 2017, 02:49 pm »
      I re-read the article by Griffin, especially the end section.

      Two things gleaned/interpreted.

      • By changing the total impedance of the overall woofer array, one can ameliorate the increase in efficiency.
      • It is beneficial to decrease the sensitivity of the drivers at the outer ends of the array in relation to the center of the array. This can also be accomplished by changing the impedance of the sets of drivers from the center out.

    All that I need now is a spreadsheet or program that I can plug in the driver size, their frequency ranges and efficiency ratings, add the distance to the listening position, an voila I could get an optimal wiring diagram. Anybody know of the existence of such a program, script or spreadsheet?

Danny Richie

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Re: Impertinent half serious question...
« Reply #95 on: 20 Feb 2017, 03:40 pm »
Danny, you have mentioned and inferred that ribbon tweeters in an array behave differently than do cone woofers in the sense that the woofer's efficiency will increase the more drivers that are added and the ribbon tweeters don't.

Can you elaborate, or point me to where I can get a better understanding of this phenomenon?

I always thought you get ~3db extra SPL per watt (in their frequency range) for every driver you threw on the fire. Is this different behavior because;
  • It is a line array?
  • The driver is a planar?
  • Of the frequency range?

My curiosity is so that I can better screen drivers without coming to you and saying, "How about this one?" 187 times.

For open baffles, I understand high QTS is good. The fellow that designed the Carver Amazings indicated the ratio between QTS and QMS linearity (whatever that means) is important. I know you say low efficiency is good, but if the old 3db per driver boost rule of thumb works for the woofers and the woofer is 80 db per watt, 16 woofers would make the efficiency 128db per watt, which is unlikely, but would require a very efficient tweeter if they didn't get any boost in multiples.

So as always, I am confused.

Anytime a driver is playing a frequency range when the width (or height) of the driver is greater than the length of the wavelength that it is playing then it is in what we call its beaming range. In other words it will play it straight forward only and not spread out in all directions. 

Check out the picture on page 15 of Jim's paper that you referenced earlier. Note the lines that he drew out from the tweeters. This is what happens at 20kHz. Each tweeter plays that range straight ahead. The short wavelengths do not spread out and couple with the other tweeters. As you move up or down then you are out of the range of all but one tweeter. So at 20kHz you never exceed the SPL capability of one tweeter.

Now this is only true for the top octave. Actually only the very top of the top octave. As wavelengths increase the output begins to spread out. It is just like looking at the off axis response of any driver. As the wavelengths increase and spread out then they start to couple. Some waves arrive delayed in time compared to others and cause out of phase cancellations. But the few that you are in front of are not delayed too much in time and they couple.

By the time you reach 1kHz most of the output is in phase and coupling. So you get a huge increase in output. You get a response line that starts at 20kHz that is no greater than one tweeter. But will increase 20db or so going to 1kHz. So the filter has to correct for the response with in that range of those drivers and not just create a crossover point.

Danny Richie

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Re: Impertinent half serious question...
« Reply #96 on: 20 Feb 2017, 03:42 pm »
      I re-read the article by Griffin, especially the end section.

      Two things gleaned/interpreted.

      • By changing the total impedance of the overall woofer array, one can ameliorate the increase in efficiency.
      • It is beneficial to decrease the sensitivity of the drivers at the outer ends of the array in relation to the center of the array. This can also be accomplished by changing the impedance of the sets of drivers from the center out.

    All that I need now is a spreadsheet or program that I can plug in the driver size, their frequency ranges and efficiency ratings, add the distance to the listening position, an voila I could get an optimal wiring diagram. Anybody know of the existence of such a program, script or spreadsheet?


Power tapering the impedance on short lines like this doesn't really work out real well.

But you can vary the series/parallel grouping of the woofers to reduce or increase output. The key is that you need the impedance of the woofer and tweeter line to closely match and you need the sensitivity levels to closely match.

aceinc

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Re: Impertinent half serious question...
« Reply #97 on: 20 Feb 2017, 05:48 pm »
Danny, the arrays I am thinking of are 64" on the tweeter, and 72" - 80" on the woofer. Does this qualify as a short line?

If the impedance does not closely match between the woofer array and the tweeter array, can't this be compensated for in the crossover?

In a standard MT environment, if one driver is 4 ohms and the other is 8 ohms and I want to crossover at say 2khz, can't I just adjust the capacitor and inductor values to compensate?

Danny Richie

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Re: Impertinent half serious question...
« Reply #98 on: 21 Feb 2017, 02:12 am »
Danny, the arrays I am thinking of are 64" on the tweeter, and 72" - 80" on the woofer. Does this qualify as a short line?

That's a pretty good sized line. I still wouldn't taper them though.

Quote
If the impedance does not closely match between the woofer array and the tweeter array, can't this be compensated for in the crossover?

Not really. If the tweeter level is higher and the impedance is lower then you can add a resistor to bring down the sensitivity and increase the impedance. That's really rare with a line source though.

Quote
In a standard MT environment, if one driver is 4 ohms and the other is 8 ohms and I want to crossover at say 2khz, can't I just adjust the capacitor and inductor values to compensate?

Yes, the crossover values can be adjusted, but you still have an impedance mismatch. Think of how solid state amps react to different loads verses a tube amp.

aceinc

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Re: Impertinent half serious question...
« Reply #99 on: 21 Feb 2017, 02:44 am »
Is this description I found a reasonable explanation?

Impedance is a function of frequency. Don't confuse "Impedance" with "Resistance." Both impedance and resistance are measured in "Ohms" but impedance can and will change as the frequency changes. Audio frequencies are typically in the range from 20 Hertz to 20,000 Hertz (20Hz - 20KHz).

Pure simple resistance doesn't concern itself with frequency, because it is measured at no frequency (zero Hertz).

A typical 8ohm woofer might have an impedance that varies from slightly below 8ohms at 1 Hertz to maybe 60ohms or more at it's resonant frequency peak and then back down to somewhere near 8ohms again. After that a woofer's impedance continues to rise gradually as the frequency extends towards and beyond 20,000 Hertz.

If you use an 8ohm woofer and an 8ohm tweeter WITHOUT a crossover, your impedance would be 4ohms! But who would use a woofer and a tweeter together without a crossover? A crossover is a frequency dividing network. As long as you are using a crossover with an 8ohm woofer and an 8ohm tweeter then your impedance will remain at or near 8ohms straight across, not 4ohms.

If you use a 4ohm woofer and an 8ohm tweeter without a crossover, your impedance would be 2.66ohms. But with a crossover, your impedance would be 4ohms in the range of frequencies covered by the woofer and 8ohms in the range of frequencies covered by the tweeter. If you use a 4ohm woofer with an 8ohm midrange and a 6ohm tweeter all with a crossover, then your impedance would be 4ohms in the range of frequencies covered by the woofer and 8ohms in the range of frequencies covered by the midrange and 6ohms in the range of frequencies covered by the tweeter.