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-   -   TQWT x Golden Rule for 8 inches Full Range (http://www.diyaudio.com/forums/full-range/207262-tqwt-x-golden-rule-8-inches-full-range.html)

FullRangeMan 21st February 2012 05:41 PM

TQWT x Golden Rule for 8 inches Full Range
 
Hello,
I wonder if on a TQWT for a 8 inches fullrange as the Supravox 215 or Visaton B200, the box wide and depth are critical??

As at this Supravox project the inside dimensions are smaller(W=25,6cm, H=102,5sm, D=36,5cm, Litrage=95,4Litres) than the Golden Ratio sizes:
http://www.supravox.fr/kits/tqwt215.pdf
According the Golden Rule the inside sizes would be> W=26 H=110cm D=42cm, Litrage=120 Litres;
This new, Golden rule bigger box may ruin the sound quality??
Thanks for any input.

Scottmoose 21st February 2012 07:05 PM

A couple of points straight off.

Firstly, nobody said golden rule dimensions have to be adhered to.

Next, what is relevant in a folded horn of this kind (TQWT in inaccurate modern parlance) is the length, driver tap location, expansion (viz. total volume), damping quantity & location, and if mass loaded, the dimensions & location of the duct. Since there is an internal line / expansion, golden rule HxWxD for a rectillinear cabinet is irrelevant. Note however that the more extreme the WxD ratio, the further you will depart from conical expansion into parabolic. The baffle dimensions & shape are relevant for baffle-step frequency & edge diffraction of course.

FullRangeMan 21st February 2012 10:39 PM

Quote:

Originally Posted by Scottmoose (Post 2916631)
A couple of points straight off.

Firstly, nobody said golden rule dimensions have to be adhered to.

Next, what is relevant in a folded horn of this kind (TQWT in inaccurate modern parlance) is the length, driver tap location, expansion (viz. total volume), damping quantity & location, and if mass loaded, the dimensions & location of the duct. Since there is an internal line / expansion, golden rule HxWxD for a rectillinear cabinet is irrelevant. Note however that the more extreme the WxD ratio, the further you will depart from conical expansion into parabolic. The baffle dimensions & shape are relevant for baffle-step frequency & edge diffraction of course.

Thanks for reply, I appreciated it.
One doubt remain, in terms of music/sound quality, what means a barabolic expansion??
Thanks

Scottmoose 21st February 2012 10:47 PM

You're welcome.

Parabolic doesn't mean anything in terms of music or sound quality since music is the recorded medium, and sound quality is a nebulous concept that varies depending on what it is you mean by it. A parabolic expansion provides the lowest efficiency of the various horn expansion profiles, a catenoid the highest, with the hyperbolic family (inc. exponential) falling in between depending on the T value. This is rather moot, since folded pipes of the type you link to are too small to get any significant horn loading within their useful BW in any case; the majority are just standing-wave generators with a taper that spreads the harmonics; whether that's a good or bad thing depends on the design in question & the desired objective.

FullRangeMan 21st February 2012 11:30 PM

Quote:

Originally Posted by Scottmoose (Post 2916983)
You're welcome.

Parabolic doesn't mean anything in terms of music or sound quality since music is the recorded medium, and sound quality is a nebulous concept that varies depending on what it is you mean by it. A parabolic expansion provides the lowest efficiency of the various horn expansion profiles, a catenoid the highest, with the hyperbolic family (inc. exponential) falling in between depending on the T value. This is rather moot, since folded pipes of the type you link to are too small to get any significant horn loading within their useful BW in any case; the majority are just standing-wave generators with a taper that spreads the harmonics; whether that's a good or bad thing depends on the design in question & the desired objective.

OK, Great explanation, Thanks. Iam a dumb about horns.
This Supravox project is too short to my taste, Do you would suggest a taller TQWT, around 130cm or 150cm tall??
Thanks

chrisb 22nd February 2012 05:22 AM

Quote:

Originally Posted by FullRangeMan (Post 2917038)
OK, Great explanation, Thanks. Iam a dumb about horns.


as are many, including come purveyors of commercial products

oops, did I say that out loud?

Scottmoose 22nd February 2012 07:49 AM

Ouch! :D

Scottmoose 22nd February 2012 07:58 AM

Quote:

Originally Posted by FullRangeMan (Post 2917038)
OK, Great explanation, Thanks. Iam a dumb about horns.
This Supravox project is too short to my taste, Do you would suggest a taller TQWT, around 130cm or 150cm tall??
Thanks

Not a problem.

I'd suggest a better designed cabinet, period. Tuning frequency is a function of axial length & taper, and the amount of mass-loading (if any) applied to the horn / TQWT / call it what you will. Going by memory (it's a while since I looked at them) those Supravox boxes don't IMO have sufficient Vb for the intended drivers though, so I'd antipate poor gain on the bottom-end.

FullRangeMan 22nd February 2012 05:04 PM

Thanks Boys, I appreciated your patience, thanks alot.

I suspect it will be a log reseach.

GM 23rd February 2012 12:10 AM

Hmm, all things considered, a BIB [or even an undersized one for floor loading] seems a better choice than the factory TQWT since a T/S max flat alignment is ~368 L/36 Hz Fb.

GM


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