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Old 24th February 2009, 03:30 PM   #11
pkitt is offline pkitt  United States
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Quote:
Originally posted by Vigo
Ok thanks,

The thread "What's the difference between a TL, a ML-TL and a TQWT?" was very good and gave me better understanding about the different designs.

But what i mostly want to try is a classic TL line that have a constant cross section or tapered down.
Is it possible to get down to a f3 around 30-35 Hz with such a design and my drivers??.

I dont mind the size sow much, but if they can be kept below about 20cm wide that is good. But the hight is not a big problem.

Thankfull for any help on this.
I don't think you can realistically expect an F3 of 30 Hz with these drivers while also keeping the overall response decently smooth, but an F3 in the upper 30's is doable, possibly 35 Hz. Also, a constant cross-section line will almost always have a pretty lumpy response; a tapered line or either an ML-TL or ML-TQWT will typically have a much smoother response. Later today I'll model what you sketched out and also take a look at a tapered TL or ML-TQWT.
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Old 24th February 2009, 07:22 PM   #12
pkitt is offline pkitt  United States
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Default I modeled the TL you sketched...

I will attempt to attach the system response curve that resulted from modeling the folded, traditional TL for which you provided your box sketch. If the attachment is visible, the solid red line is the system response. You can see two basic problems with the system response: The first is that the line's resonant frequency is too low for these drivers' Fs and Qts which causes the response to drop off below 100 Hz or so, and the second is the lumpiness in the overall response, a very typical characteristic of a traditional non-tapered line. If the attachment is not there, as I have a hunch it isn't, I'll try again with a different type of attachment.
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Old 24th February 2009, 09:00 PM   #13
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Default Maybe this time?

I'll try to attach that graph this time...
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Old 24th February 2009, 09:01 PM   #14
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Paul,
Go to the bottom of the reply window and hit the browse button. Do not try and preview, just post it.
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Old 24th February 2009, 09:10 PM   #15
Vigo is offline Vigo  Sweden
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Ok sow a traditional TL with constant cross section wont work any good with these drivers. How about a tapperd TL line.

The box don't need to have same dimensions or size as my sketch.
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Old 25th February 2009, 12:37 AM   #16
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Default Third time a charm?

Cal, thanks for the directions and I hope it works. Vigo, I modeled a tapered TL and an ML-TQWT. A tapered TL will work but the box size would need to be significantly larger than what you sketched to get a decent F3. The ML-TQWT didn't have as good as response as a tapered TL. In the end, an ML-TL will work best and I'll address that in a later post. So, cross your fingers that the attachment showing the system response resulting from your cabinet sketch shows up.
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File Type: jpg vigo tl.jpg (19.8 KB, 651 views)
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Old 25th February 2009, 12:37 AM   #17
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Default An ML-TL

Vigo, I modeled an ML-TL and will attach its system response graph. Using the cabinet sketch you provided as a general indicator of an acceptable size, the cabinet I modeled has internal dimensions of 1016 mm high, 200 mm wide and 343 mm deep. The tweeter's center is 25 mm below the top (internally). The mass-loading port, which can be mounted on the baffle or the rear panel, is a slot port located at the very bottom, with a width equal to the cabinet's internal width and a length, including the wall thickness it exits, and a height of 25 mm. The top 575 mm of the cabinet's internal height is stuffed with 455 grams of polyester "pillow" stuffing, or Acousta Stuf, or equivalent. This stuffing is uniformly distributed to obtain a uniform stuffing density of 0.75 lb/cu.ft. (however that converts to metric). In the attached graph, the system response (solid red line) is acceptably smooth, and F3 is around 37 Hz. If you would prefer using a round tube for the mass-loading port, a diameter equivalent to the area of the slot port I suggested would be right at 80 mm, and its center would then need to be about 50 mm from the internal bottom (and still mounted on either the baffle or rear panel. I hope this helps.
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Old 25th February 2009, 12:37 AM   #18
pkitt is offline pkitt  United States
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Default Oops!

In trying to converse in metric units, I made a mistake. In the ML-TL I modeled, the tweeter's center is located 25 cm (not 25 mm) from the top (internally) of the cabinet. Sorry about that. I don't think I made similar conversion mistakes elsewhere, but you might want to make sure no other dimensions seem wacky.
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Old 25th February 2009, 12:37 AM   #19
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Default One more correction...

I left out the length of the mass-loading port for the ML-TL I modeled. It is 44 mm, including the thickness of the wall it exits. I better stop posting today before I make anymore mistakes!
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Old 25th February 2009, 07:12 AM   #20
Vigo is offline Vigo  Sweden
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Thank you all for all you help with this.

You write that a tapered TL will need a big box to work.
Can you please informe me how big as this is not a big problem for me. Sow please dont think of that skecth it is not anyway the maximum size of the speaker.

The simulation for the ML-TL is very good and helpfull and i will look more in to that to.

I want to look at both designs and then decide witch to go on.

Witch of these designs sounds better, if there is any good answer to that.Or maby what is the differnce in sound is a better question ?

Thankyou all for any help
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