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er Dave, et al...help (please)
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Old 31st May 2006, 04:09 AM   #1
Nanook is offline Nanook  Canada
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Default er Dave, et al...help (please)

In the past I have defended the virtues of OB loudspeakers, and will continue to do so.
I am however in search of a fast sub that can operate from 80 HZ down without much equalization. As I had tried over a year ago to download MJK's Mathcad sheets and the Explorer version of Mathcad to no avail, I could use some help. (my system refused to unzip it , and when it finally did it indicated it couldn't run it). I am not against paying Mr King licencing fees at all, but as I said, I have NEVER been able to run his Mathcad sheets on my computer (prior to his $25 dollar licencing fee, which seems very reasonably priced to me). I understand Mr. King's need to licence his software , as some have produced commercial loudspeakers using it, without providing him due fees and acknowledgement

I am asking anyone to help with this design. The design has some physical limitations:

24"X32"X12" outside dimensions max.

front TL exit (or side ways as in Nuuk's sub for his OB loudspeakers).

and , use a pair of existing car drivers I have (just cause I have them) , w/following specifications..:

10" driver
Qts: .581
Qms: 6.620
Qes: .637
Vas: 39.26 litres
Fs:45.2 Hz
Spl: 88.79 (91 dB equivalent into 8 Ohms)
Re: 4.2 Ohms
Pe: 200 W
Le: .80 mH
BL: 10.45
Xmax: 4.3mm
Dd: 21.11
Z: 4 Ohms
Sd: .0350 m^2

The plan is to get good, fast, clean bass. Hence the wish for a TL. I have a choice of 3 amps in the 125 Watt (8 Ohm) per channel RMS range to drive a stereo pair of these subs. Initially I will use an existing set of 91 dB, 8 Ohm "bookshelf" types with these subs, but want to be able to do a full range on an open baffle similar to Mr. Linkwitz's "Orion" design, but using 4 amplifier channels and an electronic crossover. I have an electronic XO to try, but am unsure of the quality. I understand that room transfer functions may come into play, so please assume the room is 20' X 12" X 8" = 1920 ft^3 or 54.37 m^3 or

So any and all that are feeling generous with their time , any help would be appreciated.
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Old 31st May 2006, 05:57 PM   #2
vinylkid58 is offline vinylkid58  Canada
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er Dave, et al...help (please)
Hi Nanook,

IMHO your driver was designed for a vented box, not a TL. In WinISD we get a nice flat FR down to 33Hz in a 118L box with a 3"dia. x 2.18" long port.
With a tapered line of 68.5" FR starts to fall off well above 100Hz.
No idea why your computer won't run Mathcad, unless you are not using a PC.

Jeff
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Old 31st May 2006, 06:06 PM   #3
Nanook is offline Nanook  Canada
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Default vinylkid58..thnx for reply

I have seen some literature on the net regarding TLs, and some have suggested Qts of .6 is still quite viable in a TL (MJK design tables).

As per Mathcad..it simply refuses to launch. I have tried help from planet10 about a year ago as well.

An idea is a spiral horn, similar to the wall mouted "Cornu". Except I would put the TL exit (on both "sides" of the enclosure)where the driver is and the driver where one of the exits are.

Another idea is the "spiral horn" as per Takenaka. I am not looking for flat to 20 HZ.... room transfer will take it down quite a ways.
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Old 31st May 2006, 07:31 PM   #4
vinylkid58 is offline vinylkid58  Canada
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er Dave, et al...help (please)
Ok, this driver looks much better in a ML TQWT. Hey I'm no expert, I just picked the wrong line config.

Sorry for the crapy image.
Jeff
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Old 31st May 2006, 07:36 PM   #5
Nanook is offline Nanook  Canada
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Default what line length?

Tune to Fs of driver or tuned to Fs + 10%? I am assuming that I can tune the line as per regular mass loaded types?, Long fibre wool is available here... carded and moth balled...
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Old 31st May 2006, 08:27 PM   #6
vinylkid58 is offline vinylkid58  Canada
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er Dave, et al...help (please)
L = 60"
Z = .5 (driver position ratio)
So = 3*Sd
Sl = 3*Sd
Stuffing density = .25 lb
Port dia. = 3"
Port length = 1.5"
Tuning for this line would be ~55Hz (from Martin's alignment tables).

Going to a shorter line length (50") doesn't seem to hurt FR much:
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Old 31st May 2006, 09:30 PM   #7
Nanook is offline Nanook  Canada
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Default thanx again..vk

this looks more like it!

I can use the 60" line without much problem (cause I'm planning on folding it a couple of times if need be, depth and width are not a great concern, but height is!)

Taking room transfer functions into consideration I may have to pull down the bass output via the electronic XO I have, about - 3dB. I'd rather do that then find out the 50" insn't as deep.

What about the port.. can it be front firing without subtractive effects if I do so? (I prefer front firing subs:-) ), it looks like any 7 in^2 port 1/.5" long will do?

vK, I did email you directly...
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Old 31st May 2006, 10:44 PM   #8
vinylkid58 is offline vinylkid58  Canada
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er Dave, et al...help (please)
Quote:
What about the port.. can it be front firing without subtractive effects if I do so? (I prefer front firing subs:-) ), it looks like any 7 in^2 port 1/.5" long will do?
It may be better to have the port front firing, and it doesn't have to be round either. Just don't make it too narrow.

Jeff
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