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Lets do it all again: TL Sub.
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Old 2nd June 2006, 01:14 AM   #21
johninCR is offline johninCR  United States
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Quote:
Originally posted by Relax
The Transflex is just soo Tall. I would have to set it up in the corner, or lay them on their side in the front and back or sides of the room.
You're thinking of the straight transflex. Here's the folded one:

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Old 2nd June 2006, 02:57 AM   #22
GM is offline GM  United States
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Greets!

Well, the vent opening looks too small, but I assume it will be cut out to 50"^2 and the layout won't yield quite as much boundary loading as when the driver/vent is against the floor, but if it's what you want, then go for it.

WRT the Transflex, it seems to me it would be a very acoustically efficient 'one note' BP and why to get any BW out of it you need to trade efficiency by positioning the driver somewhere along its length, though I'm not convinced that halfway is the ideal except with one specific acoustic aspect ratio.

GM
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Old 2nd June 2006, 03:24 AM   #23
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Quote:
Originally posted by GM
Greets!
...WRT the Transflex, it seems to me it would be a very acoustically efficient 'one note' BP and why to get any BW out of it you need to trade efficiency by positioning the driver somewhere along its length, though I'm not convinced that halfway is the ideal except with one specific acoustic aspect ratio.
GM
GM,
I don't understand why you're calling it a 1 note BP. The driver's rear radiation goes into the beginning of a 15ft TL, which is folded so the driver's front radiation is just inside the terminus. Here's a drawing of the straight one.

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Danley's version is different in that the driver radiation goes into the line 25% down from the top and also the out of phase radiation goes into the line 25% from the terminus, so the front & rear radiation are separated by 1/2 the line length. From what I read, the out of phase radiation has little effect on response, but since that side of the cone was loading into the line (instead of the room), there was less excursion allowing much high power input.

What am I missing?
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Old 2nd June 2006, 04:05 AM   #24
GM is offline GM  United States
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Greets!

Well, the way I view it, when the driver is in compression it's an end loaded TL and on rarefaction it's a terminus driven TL, so we have a max gain BW/min gain BW situation, but 180 deg apart, so it seems to me they would sum, creating an acoustically efficient 'one note' vent, 'locking' the driver just like in a BR or TL or BP at resonance. Obviously it will have a rippling decay based on its Q, but I don't see it as being a very useful BW unless maybe if it's tuned really low, like 7-8 Hz. Only one way to know for sure though.

I just mentioned the 50% position because Joe (qi) speculated in another thread that's what TD used in the TOP sub.

GM
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Old 2nd June 2006, 04:10 AM   #25
just a guy is offline just a guy  Canada
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Isn't the effect you described going to happen anyway, at the frequency dictated by the driver offset, whatever it happens to be? I guess that's the idea, moving the gain boost away from the resonance point...

The TOP driver offset cannot be 50%, that's the end of the line and there's nowhere to mount there.
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Old 2nd June 2006, 04:56 AM   #26
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Quote:
Originally posted by just a guy
Isn't the effect you described going to happen anyway, at the frequency dictated by the driver offset, whatever it happens to be? I guess that's the idea, moving the gain boost away from the resonance point...

The TOP driver offset cannot be 50%, that's the end of the line and there's nowhere to mount there.
Regarding the TOP sub, notice how everything is kept kind of vague. Doesn't TD usually like to show off the great technical stuff with his designs? This one even includes the smoke screen of "special driver", with no detail at all. It leads me to believe that Jensen just missed the mark with the transflex and the TOP is just quite simple, a TL folded in half with the driver in the center of the cab.
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Old 2nd June 2006, 05:00 AM   #27
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Greets!

Right, as you move the driver along the pipe's length, its gain BW changes, trading peaking at Fp for BW.

End of the line? 50% means halfway between the closed end and terminus and if you read MJK's thoughts on driver positioning, halfway was the reasonable choice for his positive taper (horn) MLTL, though he does 'backpedal' a bit with his Classic TL driver positions, instead using a sliding scale based on taper ratio like I've recommended.

GM
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Old 2nd June 2006, 05:23 AM   #28
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Greets!

Only after his patents have been published and in the public domain. BTW, the Labhorn unit qualifies as a 'special driver'.

I don't believe Jensen 'missed the mark' at all if you consider the limits of audio available to the consumer at the time of its debut. Concrete slab construction homes were coming into vogue, so there was no basement for the avid enthusiast to turn it into a subterranean Helmholtz resonant coupler for those few R-T-R tapes that had true LF content. These would fade away for a few decades and be 're-invented' as manifold IBs.

GM
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Old 2nd June 2006, 05:26 AM   #29
just a guy is offline just a guy  Canada
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You said "50% means halfway between the closed end and terminus".

Exactly. There is nowhere to mount at 50% unless you mount on top of the box (when standing up, mouth side down), but then it would just be a traditional tl with the driver mounted outside the box.

My Jensen Imperial impressed me and I now have to believe that if they designed a sub to be used from 45 hz down to ??? (maybe 18 flat or possibly lower) that it is going to perform as designed (with the driver being an arguably small variable). I am semi-happy with 45 down, but would prefer 60 and down.

My transflex project (which you helped me model for an appropriate driver for, traditional style) will hopefully be underway in a couple of days and my mounting position of choice is transflex position. In case of emergency the 25-75% tap was second choice and traditional tl as modelled is the fallback plan.

If you or anyone else has good reason to try any other alignment I am open to suggestion, but all 3 of my potential alignments are basically commercially proven designs (except maybe the traditional, which is modelled with a commercially proven program).

And what is your opinion of the idea that increased power handling is a side effect of positioning the driver a substantial distance from the mouth?
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Old 2nd June 2006, 07:23 PM   #30
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Greets!

Yeah, in retrospect, I was visualizing a two pipe system rather than a 'tapped' one.

WRT power handling, it's a fact, study up on pipe resonance theory for a much more in-depth explanation than my previous admittedly simplistic references.

For the rest, I have at least one other alignment, but I'm going to check it out myself whenever I get around to it, so for now I'm going to sit back and look forward to you telling us how well reality matches what's been published so far.

GM
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