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Old 16th November 2012, 07:58 PM   #51
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An high quality active crossover may be the way to go, but you have a lot of added expense and equipment and fiddling.
A good passive network done right will sound just fine. The problem with many of the passives is they aren't done right-high ESR, excessive inductance impedance mismatches etc.
Despite what some may say, in my experience an active crossover does not always guarantee the best sound, if you really did your home work with the passive.
I have heard good, and not so good examples of both. Some electronics crossover seem to have a narrow sound stage, and add a hard electronic haze to the sound, and some frankly are just plain unmusical IMHO. Part of this is the unavoidable added electronic processing, an added noise and potential electrical interference.
Personally I would do what ever your comfortable with, and go from there.

Last edited by automaticmojo; 16th November 2012 at 08:21 PM.
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Old 17th November 2012, 02:38 AM   #52
miklos is offline miklos  Canada
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Some electronics crossover seem to have a narrow sound stage, and add a hard electronic haze to the sound, and some frankly are just plain unmusical IMHO.
Why is that? After all a filter is a filter ,before or after the amp, and amp is the same in both cases.
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Old 17th November 2012, 03:51 AM   #53
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Hard to say- poor quality parts, electrical interference. With the purely digital crossovers, poor quality ic's, power supply issues, etc.
I have seen more them a few hot-rodded active crosovers-so others must have felt the same.
A filter is a filter spec wise, but they can perform differently sonic wise. Capacitors, resistors, inductors all can impart a signature-good, bad, or indifferent.
As mentioned, these are my opinions and experiences-try one out and see what you think, as that's all that really matters. Don;t take my word for it-go out and find out for yourself-DIY.
Some people really like them, in my experience I'm luke warm to them so far-stock wise from what I have heard.
I also prefer the traditional passive setup, with less fiddling, amps wires etc.
Other this doesn't bother.
IMHO I would take the plunge-and see what happens-you can always sell it, or maybe it will be the best thing your ears have heard.
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Old 17th November 2012, 01:14 PM   #54
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I just foun this on the internet:PSP Marine Tapes : Sail Repair Tapes
Mylar selfadhedsive tape 25my or 50my. 50mm or 150mm wide.
Have ordered 50my 150mm wide.For diaphragm,might have ordered 25my 50mmwide.

Bernt
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Old 17th November 2012, 05:22 PM   #55
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I'm following this thread very keenly, since I'm considering a horn-loaded AMT for my wedding speakers next year.

A question for the AMT gurus. What determines the lower rolloff frequency more, given identical pleat depth -
1/ total area
2/ height
3/ width

Do you need a half wavelength~ lambda/2 to fit in the height of the pleat for good wave launch from the diaphragm? The TPL is about 15 cm high which is about half the wavelength at 1 kHz.
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Old 17th November 2012, 08:40 PM   #56
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Hornloading the Heil AMT1

Ess hd12 - AudioKarma.org Home Audio Stereo Discussion Forums


Horn vs. Heiled Horn?

As mentioned earlier part of the difficulty one runs into with crossing over the Great Heil low (1k) has to do with the in phase lower frequency form the rear causing cancellation. Some call it a bit of a "honk" sound, some consider it more of a midrange dip. This still happens to a smaller degree with the AMT3, which in practice crosses over fully @ 2500hz.
Some of this is in phase output from the rear wrapping around the Heil housing, and interfering with the overlap frequencies of the transition driver, and the front Heil output-the foam blocks on the side eliminates this. With the AMT3 it's a subtle, but noticeable improvement, as the cancellation is very mild to begin with.
IF you are completely blocking off the rear output with the horn setup, you would avoid much of this. You still may have a bit of honk/tonality issue-but I think the dip would be minimized, and perhaps precise horn tuning would gain some improvements, aside from output gain.
If do block of the rear, you will lose the airy quality of the Heil. Even without the contribution of the rear output, the output would obviously rise do to the (larger) horn loading.
IMHO the airy quality of the Heil is a added bonus, along with the correct tonality and awesome imaging the driver already has.
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Old 19th November 2012, 08:56 AM   #57
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Thanks for the info and links automaticmojo. I have more reading to do!

One of the reasons that getting some replacement diaphragms or making some is so interesting to me, is that they can serve a dual purpose as tweeters and also HQ headphone drivers. Learning how to make them would be the way to go in this case.
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Old 19th November 2012, 10:31 AM   #58
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There was a thread on DIYA somewhere that discussed the technicalities of Air motion transformers, and pleat depth was mentioned as being the major factor in high end response, cant remember where but a search should throw it up.

I would think that total surface area would be the ultimate decider of the amount of low end you get (subject to having enough folded width to get the air out - too tightly spaced and you would get nothing!

Bernt I think you will need a thinner material for your homemade diaphragms. look at the 2-10 micron mylar sheets that aeroplane modellers use to cover their wings
eg: HERE

Nick
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Old 19th November 2012, 11:20 AM   #59
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i'd suspect, with more surface area,

the lower the frequency to be had.

Quote:
Originally Posted by automaticmojo View Post

Oskar was a brilliant man- I think he probably would have figured it out.

seems he did

the Transar woofers.


ESS - YouTube


seen an unmounted pair at a audio store in the late 80's.


Click the image to open in full size.

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Old 19th November 2012, 03:51 PM   #60
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That would also be my first guess (up to the dipole/bipole wrap around effects mentioned above). The pleats do break the symmetry though. It would be interesting to have 2 diaphragms of the same area but different dimensions.

For those with AMTs and measurement capabilities, may I request a couple of experiments?
1/ What happens when the front of the driver is enclosed like an ear chamber for headphones? With the planars in my Fostex headphones there is a natural rolloff in free air at about 1 kHz. With sealed earpads output is actual higher below 1 kHz than below. I wonder if the resonance of the AMT gets in the way of full range headphone use.

2/ What happens when you expose less of the diaphragm at the front? Besides a reduction in output, perhaps there is better linearity. In an ideal universe you could have a giant diaphragm and expose only part of it. If it is big enough the part in the center doesn't really 'see' the boundary.

Quote:
Originally Posted by Grumpy_Git View Post
I would think that total surface area would be the ultimate decider of the amount of low end you get (subject to having enough folded width to get the air out - too tightly spaced and you would get nothing!
[/URL]

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