604 - 12 inch ?

In theory it should act as a phase plug over some portion of the woofer's BW and ideally it will be through the XO BW, but with no polar plots..............

GM

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Originally Posted by Panomaniac

The looks of that 212 horn worries me. Good for the highs, but doesn't it block a lot of the 12? Looks like trouble. No idea if it makes a difference. Anyone know?

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Simply a matter of relative size, both the size of the obstructing object (the horn), and the "size" (wavelength) of the wave passing around it;

HyperPhysics (Sound and Hearing/Diffraction)

Frequencies with a smaller WL than the horn will be obstructed, while those larger will diffract or bend around it, and if you are a few wavelengths away, you'd never know the horn was there.

Which highlights the biggest problem Duplexes must overcome IMO. The horn must be large enough to load to the lowest HF tone, and at the same time small enough to not obstruct the same tone from the cone. The lower the XO slope, the more noticeable it becomes.

The 212 may have an advantage over previous horns in that regard, as the close proximity of the horn mouth to the cone should present less of an acoustic impedance "bump" between where the horn unloads the HF, and the cone begins to load it up again.

Which seems to be a disadvantage in the Mantaray horn. The smaller sectoral horn in the older 604/605 was so small and far back in the 15" cone that the cone actually helped with some loading. The Mantaray does not benefit in the same way.

Thanks to John Busch for pointing that out to me. I found it to be true when working with the 2 different coax horns.

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Originally Posted by bowtie427ss

Agreed.

In particular, i think what many of us would like to know is what combination of parts(cone, coil/former, and suspension) might work acceptably with a 515(604) motor in a 12 inch frame.

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Originally Posted by GM

Then again, why bother? GPA has the 212 and what appears to be a superior horn.

GM

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what bowtie said about what might work.

would like to get as much flux as possible.

on the low fz. part for shure.

Small powerful Neodynium magnets made it more feasable for new coax "NON Hi FI TYPE "such as B&C, BEYMA, EMINENCE, PHL, RADIAN ,BM to be marketable.BUT

Altec Lansing "GPA MODELS" and perhaps Tannoy are the only HI FI Coax on the market today.

A 12 " from 20 to 20 KHZ is feasable and I encourage Bill to pursue this line .

Any news of someone finally hearing the GPA 212 yet, or planning to purchase etc?

Thought I'd bump this up as it has interested me and curious to know any impressions..

Dave :)

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Originally Posted by bowtie427ss

Many years ago, Peavey made a single box system(project four) ..."

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Neat.

I just had to look and found the following thread with an image of a cab which seems may be a Peavey Project 4:

Image:
http://srforums.prosoundweb.com/index.php/fa/26449/0/

Thread:
PSW Sound Reinforcement Forums: LAB Lounge => Peavey Black Widow Magnets ??

...or at least uses it's xover.

The MR does not appear to be a duplex, but am not arguing or trying to argue that point. Someone could've replaced it or perhaps it's just not obvious etc.


What really prompted me to post...

...looks like someone's already installed an Altec driver in that one for the LF!

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Originally Posted by bfish

Simply a matter of relative size, both the size of the obstructing object (the horn), and the "size" (wavelength) of the wave passing around it;

HyperPhysics (Sound and Hearing/Diffraction)

Frequencies with a smaller WL than the horn will be obstructed, while those larger will diffract or bend around it, and if you are a few wavelengths away, you'd never know the horn was there.

Which highlights the biggest problem Duplexes must overcome IMO. The horn must be large enough to load to the lowest HF tone, and at the same time small enough to not obstruct the same tone from the cone. The lower the XO slope, the more noticeable it becomes.
.

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?...When I constructed the big mid bass horn...I was researching articles...I thought I referenced it in the big 80-800 post...but JBL did a good white paper on their horn in horn design and the wavelength of the highest mid bass freq's had to be longer than K*SA or K*Circumference..something..I'll have to locate it.... of the mid range horn...well it's probably in the article you reference.(nice run on sentence ;) ) This was one reason I desired a lower XO point on the mid range horn. What is a lower slope? 6dB as opposed to 12dB? So more of the upper mid bass/lower mid range output above the XO point gets thru with a less steep slope right?...which in turn gets interfered with by the mid range horn depending on dimension?

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Originally Posted by Steve Mac

?... What is a lower slope? 6dB as opposed to 12dB? So more of the upper mid bass/lower mid range output above the XO point gets thru with a less steep slope right?...which in turn gets interfered with by the mid range horn depending on dimension?

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Hi Steve,

Yeah, lower (in db/oct), flatter, whatever. The greater the overlap, the greater the interference. 24dB LR networks make that apparent. ;)