GM's MLTL with 416-8B

[westend9]

Depends on the XO point/slope WRT predominately baffle, horn mouth width and woofer size same as with point source drivers with the caveat that a WG or horn will have dramatically more directivity for a given desired BW than a typically much smaller point source driver, greatly reducing the need for any BSC per se, with whatever is needed usually being accomplished by the XO design and/or horn adjustable shelving filter. The M19's, 846B's XOs are good examples. For < ~500 Hz XO points, HF shelving combined with some form of CD horn EQ is usually sufficient.

In short, you can't go wrong by making a horn baffle of the same width [and height if there's room] as the cab, but in most cases there's no need for it in a HIFI/HT app beyond having a highly absorbent one to reduce mouth reflections back to the driver as much as practical. By highly absorbent, I mean more like the thick fiberglass lined early M19s, 846Bs, etc. than the mostly cosmetic sculpted ones used later on.

Unfortunately, I didn't get to do much foam testing way back when and don't know the density of the two different layers of sponge material I was fiddling with back before the lightning strike, so don't have a clue what might work for even 511/500 Hz XOs; so at this point the only foam I know of that will work is something called trail pad and then only if wrapped around the mouth at the flange to form a crude ~12" deep mouth ~90 deg included flared extension which is about as anti-WAF as anything I can think of ATM, though Pano-Mike's T-shirt? experiments might be right up [down?] there too.

GM

I've built the frames for the 811 horn and chose not to extend them out any further than the material I had on hand would allow (just enough to maybe tack on some foam). My BIL gave me a small piece of foam to experiment with, it is used for upholstering patio furniture, it's an open cell foam.

GM, I'm using active crossovers that have CD compensation circuits and they seem to tackle most of the horn and drivers top end very well. If I choose to implement the super tweeters I have, I'll have more variation and functionality at my disposal, I would guess. IIRC, I had the high end crossover point at 1075 hz. for the 811 and 802G.

Again, at least way back when, designers either allowed for a typical amount of leaks due to manufacturing tolerances and/or intentionally designed them in such as the M19 not having any gasketing between its two cab sections and 811 mounting, so in a 'worst' case scenario, removing all leaks will lower the cab's tuning (Fb) which one may, may not prefer depending on how they sound in-room with all the variables this implies.

Personally, I would seal up any lossy cabs and then re-tune them in-room to suit if necessary since factory tunings are almost always a compromise and at the very least tends to 'sharpen up' the woofer's perceived response, but so many folks think the M19 is [near] perfect as is, so may not be worth the effort for them.

Assuming a relatively 'still' room WRT airflow, a candle, smoke or similar will find all of them worth plugging while driving the cab around/at driver Fs at some high enough SPL to see obvious cone excursion with the vent blocked off [densely stuffed with rags/whatever].

Then there's the folks that just spray a soapy liquid on all the potential leaking areas and look for bubbles except any exposed MDF could be problematic. Wonder if baby shampoo thinned with alcohol would blow bubbles without blistering MDF?

GM

I've gone over the cabs and filled the small slots that I made with a glued in piece of wood. That, of course took care of the major air leakage. I'll maybe try a smoke or bubble test in certain areas when I have the cabs finished and woofers mounted. I wonder if a guy could get ahold of some of that theatrical smoke, fill the cab from the vent, plug the vent, and pressurize the cabinet to see if any smoke comes out.

Or one could just caulk all the joints with silicone/adhesive etc....

Great minds....., AB. I have caulked all the joints with PL400, using a double application amount (two beads) and then smoothed that into the joint with a spoon. The spoon worked great.

Pictures of the nearly completed horn sleds, I still have to attach the tweeter bases and then will break it all down for finishing.