AE td driver transmission line? - AVS Forum
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post #1 of 7 Old 04-18-2013, 04:59 AM - Thread Starter
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Anyone done this? I'm having difficulty nailing the required perameters and if the td10m would suit this alignment.
I like the idea of the gentle roll off, effectively no fs, and reduced distortion all together.
Any thoughts? A TL for a 10" would be large, that's for sure.
It will be mated to a 350hz jmlc horn (already have this)
I would have preferred a 8" driver, but can't find a suitable one, and ae don't make one.- boo!
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post #2 of 7 Old 04-18-2013, 05:51 AM
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Can you explain what the actual benefits are to building a transmition line enclosure?

I googled it and from what I can tell, a TL type enclosure is basically like a ported enclosure with a set of boards on the interior of the cabinet that start out at one width and then slowly get narrower as it approaches the bottom where the hole is at.

Is this right? What does the term, "coupling" mean, with regards to drivers in a TL enclosure?
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post #3 of 7 Old 04-18-2013, 07:15 AM - Thread Starter
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Instead of a resonator tuned to a frequency that is just below the roll off of the driver, a TL is a tube that is a specific length which the sound travels down from the back of the driver and exits out the other end in time with the sound coming out the front if the driver, this increases the output if the driver by as much as 6db.
I would likely make a tapered quarter wave TL, meaning that the tube starts as a narrow passage, but progressively widens towards the exit. This reduces standing waves.
The design reduces distortion generally, as the wave coming from the back of the driver isn't forced to exit the speaker by reflecting back through the driver cone as much at a delayed time to the signal smearing detail to some level.
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post #4 of 7 Old 04-18-2013, 07:55 AM
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I found reference to one simulation using Martin J. King's worksheet where it was found a TD10M worked best in a 45Hz line. The pipe length would be 83.5 inches based on 40.5Hz fs. If using hornresp I'm not sure how it would simulate the expansion, but I agree it may not be a small enclosure. This sounds like a neat project.

I've got two TD10M's I'm using for another design, but I like your direction. I was planning a JMLC-350/Radian over a TD15S. I hadn't considered the TL alignment until now.

-Nate
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post #5 of 7 Old 04-19-2013, 05:24 AM - Thread Starter
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Hi nate,
Can you link me to the reference?

Yea, your design sounds similar. I started with a jbl 15inch bass driver, but I just couldn't find a way of making it visually acceptable for my living room.
My design will have an 11 inch front baffle, as this is the acceptable limit before it looks overbearing.
I've given up on the other options of using a pair of 10m's or equivalent as the cost seamed excessive for no real gain, a bass driver in the side of the cab is a no go as the only ones good enough to mix with the 10m's are ae drivers and again increase the costs and complexity.
The 10m was chosen as it measures the best out of the 10 inch drivers, and will give me enough range to not excite any harmonics in the mid, regardless of the crossover point used.
But it's xmax limited, so as a sub will handle below 70 hz, the TL design seams to fit the need- keeping excursion down right where I need it and generally reducing distortion further anyway.

The other thing I need to find out is how to measure the tube length when folded. Is it the length down the center of the tube or the shortest route or what. Haven't found an answer to this yet.
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post #6 of 7 Old 04-19-2013, 10:51 AM
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Hello sir,

Here's the thread: http://www.diyaudio.com/forums/multi-way/132884-10-mtm-neopro5i-ribbon-build-thread.html

Ya, this TD10M design your proposing would need to be integrated with a sub, but the TL in combination with the JMLC horn seems to be the best for both frequency response and efficiency, imo. Of course, the trade off is the size of the enclosure and SPL. It may not hurt to at least try a bass reflex, but I think I've got a grasp of what your after here.

Not completely sure about the length, I'm still learning hornresp, but...according to MJK's offset driver geometry figure (I'm assuming the driver will be offset), total line length equals the sum of the closed end and open end of the TL. So, it would seem the length would be the longest route. Here: http://www.quarter-wave.com/TLs/Advanced_Models.pdf

(1128/40.5) / 4 = 6.96 ft. (Speed of sound in feet divided by Fs divided by 1/4 wavelength)

6.96 x 12 = 83.55 inches

This may be shorter with tapered TL as apposed to straight and any lining you use from what I've gathered.

-Nate
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post #7 of 7 Old 04-21-2013, 02:24 PM - Thread Starter
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My biggest concern is the cabinet width. Height is actually a good thing for me and a fair amount of depth is acceptable.
I'm hoping its possible to mount the driver in a cabinet that's 2 inches narrower than the bass driver, and make the cabinet 'bulge' out around the driver to accommodate it properly.

If I read the thread right, a lower tuning leads to a shorter tube- that sounds wrong to me to be honest.
The measured difference between the tl and the final sealed design is massive! It seams that the TL completely compensated for all baffle step.
It's a shame his project went so wrong, the second I saw it change to a sealed design I thought it was all over. Made me remember my Troels Gravesen tjl3w speakers- great, but totally the wrong speaker for my application. Really feel for the guy!
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