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Old 15th March 2008, 10:25 PM   #1
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Default another transmission line question

The math and puter programs are over my head...
I'm wanting to marry a TL line with 10" woofer to my ESL panel crossing over at 500Hz with 24db slope. I'm looking at an Aurum Cantus AC-250F1 for this purpose.
Most ESL folks use an 8" for this but I need more puch-- thus, the 10" preference.

Since the ESL will sit atop the box, I will need the smallest box volume possible.

Please anyone jump in here and advise me on the woofer choice (or alternates) and on how small the box can be (willing to compromise some on bass extension to achieve minimum box size)

thanks all
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Old 16th March 2008, 04:04 AM   #2
GM is offline GM  United States
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Default Re: another transmission line question

Define 'small'.

Anyway, assuming a SS amp and sufficiently large gage wiring, using a 0.29 Qts driver in a TL pretty much defines a compromised bass output and the only way to get any 'punch' out of it in a small TL would be to use a ~max flat impedance alignment which further reduces its bass extension, though this driver's high Vas will still keep it from being small by most folk's standards:

L = 45.125"
CSA = 146.4"^2

All dims i.d. and 1.5 lb/ft^3 polyfil stuffing density simmed.

GM
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File Type: gif aurum cantus ac-250f1 68.97 hz max flat tl.gif (6.7 KB, 308 views)
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Old 17th March 2008, 01:46 AM   #3
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GM,
Thanks for the info. Let me better define "small" and invite you to advise me further. ESL's are big anyway and I'm trying to keep the TL box small to meet my design goal of 6ft total height. For the TL, I'm thinking a 7 1/2 ft tapered/folded line using a smaller than usual cross section to reduce the box size... that is; a line section about equal to the woofer's driven area at the front of the line, tapering to about 70% of that at the terminus. I will be driving the woofers and ESL panels separately with dual Carver 225W/channel amps so power shouldn't be a problem. I've attached a first draft drawing of the hybrid ESL/TL I have in mind. Please have a look and tell me what you think.

thanks!

Charlie
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File Type: jpg scan0003.jpg (33.4 KB, 305 views)
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Old 17th March 2008, 03:54 AM   #4
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Greets!

You're welcome!

Unfortunately, the thumbnail doesn't blow up enough to be legible. Anyway, here's the AC-250F1 in your TL:

GM
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File Type: gif aurum cantus ac-250f1 in 90' tqwt.gif (6.7 KB, 260 views)
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Old 17th March 2008, 03:56 AM   #5
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Looks like you're better off just putting it in the same size sealed cab:
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File Type: gif aurum cantus ac-250f1 in 2.4198 ft^3 sealed.gif (6.6 KB, 261 views)
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Old 17th March 2008, 12:16 PM   #6
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Yes, it certainly looks like sealed box of same volume would work better but please help me understand why... is the driver not suitable for a TL or is it my box configuration?
What could be changed to make it better?

I've attached a somewhat better scan (the file size restriction here is a killer)

thanks!

Charlie
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File Type: jpg scan0005.jpg (78.6 KB, 282 views)
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Old 17th March 2008, 04:54 PM   #7
sreten is offline sreten  United Kingdom
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Hi,

The simple fact is TL's are not volume efficient, so small / undersized
ones simply do not work well. Vented boxes AFAIK are smaller than
optimum TL's and sealed box is ~ half the vented volume again.

It seems you have 2cuft to 2.5cuft to play with, sealed is probably
best.
FWIW unless you have some independent test results you generally
cannot always trust chinese driver specifications, you should have
some way of verifying good distortion performance for example,
especially crossing over highish to an electrostatic.

/sreten.
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Old 21st March 2008, 08:46 AM   #8
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What would be a good TL box configuration for the Aurum Cantus 10" driver? That is; with respect to the line cross-sections and the front and at the terminus and the line length? If this driver isn't good for the application, can you suggest one?
thanks,
Charlie
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Old 21st March 2008, 10:17 PM   #9
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Quote:
Originally posted by CharlieM
Yes, it certainly looks like sealed box of same volume would work better but please help me understand why... is the driver not suitable for a TL or is it my box configuration?
What could be changed to make it better?

I've attached a somewhat better scan (the file size restriction here is a killer)

thanks!

Charlie
You're welcome!

It's just barely readable. FWIW I've had good luck with SnagIt 5.0 auto reducing big files to gifs I can post here.

It's the driver's specs, a ~2.4198 ft^3 net TL constitutes an acoustically large sealed cab, so it doesn't need a well damped pipe loading to get a ~I.B. response in a compact design, so the only advantage to loading it with a TL would be to damp the driver's impedance peak for an easy load to a high output impedance amp.

For low Q drivers, a high aspect ratio TQWT is preferred, ergo will be shorter for a given Fp:

L = 50"
SO = 149"^2
SL = 28"^2

All dims i.d. and 0.75 lbs/ft^3 polyfil stuffing density simmed.

GM
Attached Images
File Type: gif aurum cantus ac-250f1 20 hz tqwt.gif (6.7 KB, 128 views)
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