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Old 19th August 2004, 08:05 PM   #31
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Quote:
Originally posted by GM
The way I interpret it is he's proving my point WRT the detrimental effect on performance a simple diagonal divider board has in a rectangular cab due to not maintaining the flare rate through the bend(s).
I have always seen this as an excuse to solve 2 problems with
one stroke - corner pieces smooth the path and help keep the
taper.
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Old 19th August 2004, 09:24 PM   #32
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Hmm, corner deflectors in typical sized cabs have no impact on long WLs, so unless it's meant to have a wide BW they are a waste of time beyond stiffening the joint, though sticking some damping in the corners helps reduce any HF reflections back to the throat. Anyway, my remark referred to the simple one fold bend of a typical TL made by adding an internal baffle to divide a rectangular cab into two pipe sections.

Anyway, your designs imply you already know all this so I guess I miss your point.

GM
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Old 20th August 2004, 04:00 PM   #33
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Default How about 4 peerless 1727?

I have 4 of these 10 in drivers...

Specs are:

Fs = 22Hz
Qts = 0.35
Qms = 2.62
Qes = 0.38
Vas = 136L

How about Push-pull with drivers mounted on each other to cancel distortion then mounted in 2 TL cabinets one for each channel driven by a plate amp for each side?

It would be large...

I d/l the mathcad stuff but it doesn't work... it won't load the sheets.... dunno whats going on.

I do want to take into consideration room gain... so... any thoughts?

I really do enjoy this thread... I am trying to learn about TL and TQWT because I want to build a fullrange one to (JX92s or FE167).

Thanks!
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Old 20th August 2004, 04:22 PM   #34
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Default Corner deflectors

Hy guys. I'm missing something too because I'm not certain the connection between the above posts, and my last entry, but then again, this thread is about my original question and not so much about my project isn't it?

I have a question which may reveal some confusion I have about the process of maintaining the taper. Much of the reading I've done indicates that corner deflectors have minimal impact on the behaviour of a TL. I've been led to believe that the most important thing is to maintain the taper cross section.

Now, I have explained earlier in this thread that I don't do math well, hence my need to ask for help in designing this cabinet. Thanks again GM for your assistance. When you provided me with some alternative parameters for folding the pipe down to the size I was constrained to by my room, I used some simple geometry to arrive at the cabinet configuration. I simply manually drew out a scaled down representation of the pipe and divided it into three slices that could then be rotated and pieced back together within a square. I've attached a JPG graphical representation of my methodology, though it is far from proportionally correct. Perhaps there is a fatal flaw in my thinking on this, but anyway I "slice" it, the cabinet has the same volume and maintains the appropriate taper. If my assumptions are correct, then placing corner deflectors in this configuration will result in compromising the taper.

So am I gravely mistaken?
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Old 20th August 2004, 04:38 PM   #35
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Default Attachment

Boy, it's tricky to change the attachments on this forum!
Attached Images
File Type: gif single fold (small).gif (7.7 KB, 130 views)
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Old 20th August 2004, 04:46 PM   #36
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Default Learning about TL

Quote:
Originally posted by AudioGeek

I really do enjoy this thread... I am trying to learn about TL and TQWT because I want to build a fullrange one to (JX92s or FE167).
See this thread for the Jx92s and a nice little cabinet designed by GM... not TQWT, but looks really

mk
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Old 20th August 2004, 06:14 PM   #37
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Quote:
Originally posted by GM
Anyway, your designs imply you already know all this so I guess I miss your point. GM
My point would be that 45 degree corner reflectors might
only make a subtle difference, but they do so on several
fronts. They do stiffen the enclosure, they do allow a more
accurate taper with a folded pipe, and they do provide some
reflective/diffusive effects which reduce unwant internal
resonance. Having tried it both ways, I find that I prefer
the sound, what else can I say?
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Old 20th August 2004, 06:45 PM   #38
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Default Re: How about 4 peerless 1727?

Quote:
Originally posted by AudioGeek
I d/l the mathcad stuff but it doesn't work... it won't load the sheets.... dunno whats going on.
If you d/l mathCad Explorer did you d/l the version 8 worksheets to go with it?

dave
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Old 20th August 2004, 07:02 PM   #39
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>How about 4 peerless 1727?
====

Hmm, this needs a thread of its own........

====

>I suspect this is where the 15hz peak in the MathCAD curve may have been excited.

All in all I am very happy with this simple project. It is quite literally, the best sub I've ever heard in a home installation, and it isn't even finnished yet. Not bad for less than $100.00 total investment (not including the $60.00 Sanyo Amp that powers it)!

====

If it performs as the plot indicates, it 'rings' way too much in the audible BW, so I recommend damping it somehow. At a glance, I'm not sure what you finally built, so how about a recap of the sub's cab specs/construction?

====

>......but then again, this thread is about my original question and not so much about my project isn't it?

====

I thought it was covered rather thoroughly already, so what's still not clear?

====

>Much of the reading I've done indicates that corner deflectors have minimal impact on the behaviour of a TL. I've been led to believe that the most important thing is to maintain the taper cross section.

====

Correct, as has been discussed already. I guess in retrospect, NP was saying to use corner deflectors to help maintain the flare, but as I noted, in the typical simple bi-fold as shown on MJK's doc they have no audible impact until quite high in the BW. If you want to see measured proof, I believe BB posted some on his site: http://www.geocities.com/rbrines1/

Now if you design the folds using corner deflectors and make the cab whatever size this dictates, then of course they properly maintain the flare rate. The LABhorn is a good example. Doing it this way also preserves most/all of the HF BW, though this isn't necessarily desirable for its intended BW, so some means of attenuation is required.

====

>If my assumptions are correct, then placing corner deflectors in this configuration will result in compromising the taper. So am I gravely mistaken?

====

Not based on my experience.

GM
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Old 20th August 2004, 10:24 PM   #40
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Default Hi GM

In response to my comment: ".....but then again, this thread is about my original question and not so much about my project isn't it?"
GM asked:

"I thought it was covered rather thoroughly already, so what's still not clear?"

============================================

There's nothing contentious GM. The only confusion I have is that this thread has been inactive since my last posts in Dec 03, so the two posts following my recent update seem somewhat out of context, like a conversation carried over from another thread.

As far as the cabinet dimensions, I will be taking it apart and stuffing it this weekend so I will take some measurements and photos to post.

Could you explain to me how you can tell that the cabinet is ringing from the plot I posted. I punched in a number of different stuffing densities, up to 2 lbs/ft and it only nominally changed the curve. Perhaps I'm missing something.
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