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Reverse engineering an MLTL - enclosure done, need to find a woofer that works in it
So here's an unusual question... but hopefully a fun theoretical exercise 
I have a pair of MLTL cabinets built for the Rival R176p woofers. The design is a wonderful one someone in the FB Tline group shared with me, I believe one of Paul Kittinger's, based on the use of the MJK worksheets and Paul's normal formatting style. I was very happy with the limited listening I had of these woofers in these boxes; really great low end performance.
The project has unfortunately stalled out; some of you may know one of my hypex fa123 plate amps died, frying the voice coil of one R176p. It is becoming increasingly clear that I will not be able to find a single r176p (no one privately has singles to sell, RAD doesn't reply to my inquiries about singles). However, I am determined to finish out the project, hopefully without much additional $ outlay. To that end, I do have a whole pile of other Rival 7" drivers that fit the cutout. Namely:
Rival r176 cpc 8 (the version that looks identical to standard 176p) x 2
Rival r176 cpc 8 (shiny coated cone, convex dustcap version) x 2
Rival r176 cpac-08 x 2
Rival r176 cfc-04 x 2
Rival r176 kvc-08 x 2
Rival r176 kapa-08 x 2
I also have a pair of r182 KMO but those won't fit the cutout. Looking at this list in retrospect, I wonder if I bought more of these than anyone else? Kind of crazy. Hoarders gonna hoard, I guess.
Anyway, in an effort to salvage my project, I have been thinking I could measure all these woofers with DATS, and see if any of them work in the same MLTL enclosure. The problem for me is, I can't replicate the design, since the MJK sheets aren't available anymore. And for whatever reason hornresp defies my best attempts at understanding, so I don't know how to translate the sim to that software, or to be honest even what the critical similarities/differences in response to look for would be.
Now to my question - what if I model the MLTL as I built it, with the R176p, as a standard bass reflex box? I would use say, Bassbox Pro, VituixCAD, or whatever FRD consortium tool is appropriate. If one of the other rival woofers gets me close to identical response in the 'normal' BR model of the MLTL, is that a good fit? Or is there some unique aspect of MLTL design that would make two woofers that would work well in the same BR box not work well in the same MLTL?
Comments
Hornresp tutorial;
https://diyaudio.com/forums/full-range/243483-improved-transmission-line-alignment-10.html?fbclid=IwAR3HiqOk0G16mdUUFGEAsbmyqAXi7cBMJwbNHgzGom_2xtyTovAfhBFkQfQ#post5703741
And Brian Steele worksheets https://diysubwoofers.org/sheets/
MJK's website quarter-wave.com/
Thanks Kornbread, I am aware of Martin and Brian's sites, and I have in fact used Patrick's tutorial in my last attempt to learn hornresp. Maybe it's the way I learn, but it doesn't help much at all. I can repeat his steps, but have little understanding of what I'm actually doing, why I'm zeroing out parameters, how to adapt to an MLTL, move the port to the back, etc. That's without even getting into how to replicate my existing enclosure and verify the results match what I have from MJKs worksheet.
While I realize 'just learn hornresp' is a right answer, quite likely the best answer... it's really not worked for me so far, and since I really am just looking to salvage this particular project for the time being, I'm hoping there may be an easier way. And of course, I'd like to know the answer from an just an intellectual POV.
Sorry I couldn't help. Maybe pm Brian? He seems like a very helpful person.
I have MathCAD and King's MLTL models for them (grandfathered in from years ago). If you want help, let me know.
(RAD doesn't reply to my inquiries about singles) I'm shocked to hear that. The Rivals are not available in singles but they should've replied to your needs.
Dude, got you beat!
I actually have 14 of the Rival 176 drivers.
(And I really need to make a pair of MLTL towers to use some up!)
I've modeled the R176s extensively in Hornresp (took me a while to get up to speed)
and probably can pump out a sim for you easily.
Send me the T/S specs for what you want to use, and the specs for the box.
My experience with HR is that the bottom end of a MLTL models very similar to a standard bass reflex,
but the "art" is moving the driver up and down and using stuffing to even out the nulls.
Since the position of your drivers is fixed, much easier job.
The model will show basically what you will get, and it's your decision from then on.
Thank you, everyone. On rereading this this with less beer in me, I'm realizing that I probably buried the lead here a bit, and should have just left out most of the context. Really I wanted to start a discussion about modelling the same enclosure as MLTL vs BR and how, when, and if they were interchangeable. All but the last paragraph though read more like a sob story than an invitation to that discussion. That being said, I appreciate all the offers of help!
Kornbread; your links may not help me in this instance, but they ARE the right answer. And someone finding this thread in the future will get that from them, so the effort isn't wasted.
Jason, I appreciate the offer, I may call that favour in at some point.
Leon, first off I need to be clear about one thing: when you were involved with RAD, the customer service was uniformly great. On more than one occasion you or the other fellow I emailed with (whose name embarrassingly eludes me right now) went above and beyond to make something right, or provide assistance. The customer service may well still be great; I've had no interaction with the new owners, have only sent a few messages through the contact form on the site explaining the damaged woofer and asking about any replacement or repair options. I was surprised not to hear back, especially since presumably they could look at my account and see my purchase history. To be charitable to them; the contact form may not work, or they may not have replied because they don't want to sell singles or know they can't get the drivers again. I don't want to belabour this aspect of the situation, since the fact they don't sell singles, and the fact they've been out of stock on the 176p since the first time I checked a few months ago, make it something of a moot point.
Don, if you've 14 pairs then you do have me beat! If we have overlap in models, we should compare notes sometime about project plans and measurements! I've done little with mine yet but really should do... once I clear this first project. I will PM you with the design I have (not sure if the PDF was meant for public consumption) and see what you think. It does mention substituting one of the Kevlar versions and adjusting port length and stuffing to compensate, so I know it's doable. But the driver mentioned is not one I have unfortunately.