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Straight vs tapered 1/4 wave, rear waves.
Straight vs tapered 1/4 wave, rear waves.
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Old 12th January 2021, 07:50 PM   #1
50AE is offline 50AE  Bulgaria
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Straight vs tapered 1/4 wave, rear waves.
Default Straight vs tapered 1/4 wave, rear waves.

Not sure if already discussed, but how significant is the contribution of a non-parallel wall in a tapered TL construction towards fighting the internal box reflected waves? As far as I know, the parasitic harmonics need as much as bouncing as possible to get caught the most into the stuffing, before reaching back to the driver or port. Is a straight TL considered evil in this aspect and if yes, how can it be fought without tapering? Adding some asymmetric construction inside, like braces?

Last edited by 50AE; 12th January 2021 at 08:36 PM.
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Old 12th January 2021, 08:13 PM   #2
Booger weldz is offline Booger weldz  United States
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Its mass loading and heat or friction. But its created a long LP filter and compared to a straight or expanding shaped pipe it stands out in its affective ‘qw Fb for its length(shorter). at some point thats bass reflex, just diverge from the blended shapes into distinct ones (more than a Dalene TL). The MLTL is pretty neat, it would be interesting to stick a mic up inside or drag it with an exterior magnet(fish tank glass cleaning tool?) and find the pressure nulls and put them at harmonics by design(fold at the those points)? But also in the ‘straight csa TL, to compare . And answer parts of your question, cause its a good one!!

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Old 12th January 2021, 08:49 PM   #3
TBTL is offline TBTL  Germany
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Assuming you mean reflections at midrange frequencies:
Non-parallel walls do not remove standing waves, they just make it harder to calculate at what frequencies they occur.
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Old 12th January 2021, 08:53 PM   #4
AllenB is offline AllenB  Australia
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Straight vs tapered 1/4 wave, rear waves.
Quote:
Originally Posted by 50AE View Post
need as much as bouncing as possible to get caught the most into the stuffing,
The higher frequency performance of the damping will already do this.
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Old 13th January 2021, 04:38 PM   #5
50AE is offline 50AE  Bulgaria
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Straight vs tapered 1/4 wave, rear waves.
After specific frequencies, yes. But what about the lower midrange, 200 to 400Hz? The closest parasitic harmonic is removed with driver offset.

One tip I know is making the depth (distance from the driver to its rear wall as small as possible, to avoid big wavelengths (low frequencies) developing.
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Old 13th January 2021, 05:08 PM   #6
50AE is offline 50AE  Bulgaria
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Straight vs tapered 1/4 wave, rear waves.
Quote:
Originally Posted by Booger weldz View Post
Its mass loading and heat or friction. But its created a long LP filter and compared to a straight or expanding shaped pipe it stands out in its affective ‘qw Fb for its length(shorter). at some point thats bass reflex, just diverge from the blended shapes into distinct ones (more than a Dalene TL). The MLTL is pretty neat, it would be interesting to stick a mic up inside or drag it with an exterior magnet(fish tank glass cleaning tool?) and find the pressure nulls and put them at harmonics by design(fold at the those points)? But also in the ‘straight csa TL, to compare . And answer parts of your question, cause its a good one!!
Makes sense! But thinking pragmatically, if you find out where these hot spots are, what follows? Some kind of local Helmholtz resonators?
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Old 13th January 2021, 06:51 PM   #7
planet10 is offline planet10  Canada
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Straight vs tapered 1/4 wave, rear waves.
A tapered line vrs a straight one will be a shorter but they usually end up the same volume.

The taper has little or no effect on reducing the (usually) close to non-existent side-to-side waveform because they are at such a high frequency that the absorbion used to kill the unwanted quarter-wave harmonics is more than sufficient to kill higher frequencies.

I have found that getting any interior walls too close to the driver leads to significant mid-range/voice colouration.

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Old 13th January 2021, 07:21 PM   #8
50AE is offline 50AE  Bulgaria
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Straight vs tapered 1/4 wave, rear waves.
I've found out during the latest years, when listening to bigger box projects of a same constructor, the larger ones having sounded like having more box coloration than the smaller ones. My only two explanations for this phenomena are the possible lack of bracing and probably lower frequency standing waves developing inside. Some bigger box speakers have even sounded colored from the drivers themselves (possible leaking) and not from the port.

So I'm a bit confused. One of our local speaker designers from whom I heard one of the most transparent ML-TL project so far, said, the best way to treat rear waves is to make the box as little shallow to avoid wave development or to make them as deep as possible, like a Nautilus. But he also puts in a lot of bracing.

The other extremely transparent TL I've ever heard was made like an Ariel. There wasn't even driver offset. A lot of folding downwards into small sections, which I presume, gives included bracing. This TL sounded like an OB. Here's a video of the project, you can see construction photos: Stoy40 TL - YouTube

Last edited by 50AE; 13th January 2021 at 07:26 PM.
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Old 13th January 2021, 08:13 PM   #9
planet10 is offline planet10  Canada
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Straight vs tapered 1/4 wave, rear waves.
It is much easier to build a small box that has panel resonances suppressed to a much bigger degree than in a big box.

One of the reasons i like loading woofers push-push if i can. Dramatic reduction in box load.

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Old 13th January 2021, 09:15 PM   #10
50AE is offline 50AE  Bulgaria
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Straight vs tapered 1/4 wave, rear waves.
Now this has opened a new question. How significant can be the weight of audibility of internal returned cones waves vs cabinet resonances?

Returned waves to the cone should be measurable by looking at the impedance curve?
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