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.

[voice of the theater]

Those look great--nice progress!

[Altec Best]

Yes, but I'd like to test just so I know if there are any actual leaks I'd be sealing in these factory cabs or am I just playing with silicone and making a mess when and/or where I don't really need to.

It can never hurt.It is called going the extra mile.If you feel it is too much of a bother than your in the wrong hobby !

I'll maybe try a smoke or bubble test in certain areas when I have the cabs finished and woofers mounted.
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.

Absolutely ! That's the carpenter in us.Better to be safe than sorry.It is much easier to do it now while your building than have to go back.

How bout using water and soap ? Can you use wax on the area to keep the water from penetrating the wood ?

[voice of the theater]

Yes, but I'd like to test just so I know if there are any actual leaks I'd be sealing in these factory cabs or am I just playing with silicone and making a mess when and/or where I don't really need to. Also, if I just caulked all the joints without doing a test first, I'd always wonder afterwards if I had actually fixed anything or not. Whereas if I test first, I'll know for sure if there were leaks that were sealed, and if so, I'd know that I may have to adjust the tuning of the factory cabs to compensate.....
P.S. Another test just occurred to me--maybe I could just put a canary inside the cabinet, temporarily seal off the port and check in a couple of days to see if he's still breathing in there (like the old coal mine test).....:doh:

It can never hurt.It is called going the extra mile.If you feel it is too much of a bother than your in the wrong hobby !

I hate to disagree with you (because you've been incredibly generous with some top notch advice which helped me to re-cap both of my pairs of Model 19's and my Model 14's as well for example) but with all due respect, in this case--actually, doing a leak test before caulking IS going the extra mile. Remember, these are factory cabs we're talking about--"if I just caulked all the joints without doing a test first, I'd always wonder afterwards if I had actually fixed anything or not. Whereas if I test first, I'll know for sure if there were leaks that were sealed, and if so, I'd know that I may have to adjust the tuning of the factory cabs to compensate....." In other words, since these are factory cabs and I'm extremely happy with their current tuning, if I try to cut corners by not testing first, and just caulk every wood joint, I won't know afterwards if the cabinet's tuning has been changed by caulking the joints because I won't know if there were any leaks present that were sealed by caulking (which might mean that I need to consider doing some tuning adjustments/serious critical listening evaluations and/or measurements).... Wow, talk about a run-on-sentence..... I think you misunderstood my intentions (or I didn't make them clear)--there is no way I would cut corners regarding my Altecs--they are a high priority for me. I use one pair of Model 19's in my (in home) recording studio for recording/monitoring and I use the other pair of 19's in my rec room to playback mixes in a different environment/different acoustics (and of course to enjoy vinyl, CD's, DVD's digital cable, etc.). I use the Model 14's in my living room to further evaluate mixes to see what they sound like on a different pair of speakers (in a different room/different acoustics) and for general listening purposes/enjoyment as well...... If anything, the guys in my band accuse me of being too diligent--not of cutting corners. For example, after I mix a song/CD, to "test it out" I play it on both pair of 19's, the 14's, a small pair of speakers (two way with 10" woofers), a boom box, the car stereo, and even on my computer speakers. If the mix/song sounds good in all of those places, I feel like I've got a winner......

[GM]

It doesn't,but it shouldn't have any leaks in any of the wood joints.Driver seal leakage,door hatches/acess panels, would be another matter.

Guess you've never leak tested any early Altec or similar consumer cabs.......... How do you think I learned this? Indeed, if you look at early T/S programs, considerable leakage [low Ql value] is recommended in the vented alignment design routine due to how hard it is to seal one up properly for most efficient vent action.

Heathkit's vented cabs OTOH taught me what 'tight' was all about. Ditto theirs and AR's sealed cabs.

GM

[Altec Best]

I hate to disagree with you (because you've been incredibly generous with some top notch advice which helped me to re-cap both of my pairs of Model 19's and my Model 14's as well for example) but with all due respect, in this case--actually, doing a leak test before caulking IS going the extra mile. .

I think you forgot who's thread this was, I was talking about Westends cabs he is building.Since he is building them from scratch.Factory cabs I think you can have a different approach unless they are pretty beat up. Everyone has an opinion though so to each's own.

Guess you've never leak tested any early Altec or similar consumer cabs..........

GM, I think you misunderstood what I said too. Lance knew what I meant.

[GM]

The candle test sounds like a simple, yet effective test. That way I don't have to worry about any potential damage from spraying a liquid on the cabs. Even if the leak isn't substantial enough to blow out the candle, I'm sure you'd see the flame being affected by small "gusts" of air coming out of cabinet leaks when the bass is really "thumping". Thanks GM! Should I be more careful than usual regarding how loud I play the speakers during the test--is there any potential danger to the woofer having the port blocked while testing with relatively high SPL's? I'm sure I'd want to wear ear plugs during the test--being that close to the cabs.....

You're welcome, though I've never tried either the candle or smoke test, just have read of others doing them. I've always used Windex or generic equivalent as it blows nice bubbles and doesn't hurt any wood/finish I've sprayed it on, though I use a small pump sprayer normally for cleaning eyeglasses to keep overspray/saturation to a minimum and if it's any kind of particleboard I just automatically caulk it and it 'is what it is'........

I'm sure a vent could blow out a candle, but I doubt a typical leak could even at peak SPLs on underhung motors such as Altecs, though I imagine one of those 15-25 mm Xmax monsters being pumped up with a few kW might.

Probably not, but watch the excursion and don't exceed an 'eyeballed' Xmax value or ~3 mm [1/8"] if none is available.

WRT ear plugs, that's a personal call since at low frequencies we can tolerate a lot more SPL for a lot longer time without damage than higher up in our acute hearing BW. Anyway, around/at Fs in a ~sealed cab shouldn't be all that loud sounding even right next to it with just a single LF tone at this low an excursion. Get up around 80-100 Hz though and its T Rex stomping on your head or you're at the intro to a Headbanger's Ball.......

GM

[GM]

If the mix/song sounds good in all of those places, I feel like I've got a winner......

Agreed, wish the major players were so diligent as most CDs I've listened to in the last decade are was too forward/strident for HIFI/computer apps, though not so much for car audio. What little music I listen to these days is mostly on DVD since they are either movie soundtracks or mixed like one and use some old Sony headphones for computer.

GM

[GM]

GM, I think you misunderstood what I said too. Lance knew what I meant.

If you say so, but when someone quotes me I will always assume it's directed only to me and my response........

GM

[westend9]

How bout using water and soap ? Can you use wax on the area to keep the water from penetrating the wood ?

I could but not until I have a finish on the wood. I am thinking about GM's idea of the alcohol and shampoo.

Those look great--nice progress!

Thanks,
I am putting tung oil on the Maple that I used on the sleds and I'm acutually excited. I've finished a lot of wood but this spalted stuff is really cool (and it's mine).

Guess you've never leak tested any early Altec or similar consumer cabs.......... How do you think I learned this? Indeed, if you look at early T/S programs, considerable leakage [low Ql value] is recommended in the vented alignment design routine due to how hard it is to seal one up properly for most efficient vent action.

Heathkit's vented cabs OTOH taught me what 'tight' was all about. Ditto theirs and AR's sealed cabs.

GM

Yeah the original Model 19 must have had some pretty fair leaks. IIRC, mine had the top enclosure just bolted to the bottom cab with four long bolts into cleats. The dividing partition (black board) was particle board. with a rough edge. The laminate was what made it look finished.

You're welcome, though I've never tried either the candle or smoke test, just have read of others doing them. I've always used Windex or generic equivalent as it blows nice bubbles and doesn't hurt any wood/finish I've sprayed it on, though I use a small pump sprayer normally for cleaning eyeglasses to keep overspray/saturation to a minimum and if it's any kind of particleboard I just automatically caulk it and it 'is what it is'........

I'm sure a vent could blow out a candle, but I doubt a typical leak could even at peak SPLs on underhung motors such as Altecs, though I imagine one of those 15-25 mm Xmax monsters being pumped up with a few kW might.

Probably not, but watch the excursion and don't exceed an 'eyeballed' Xmax value or ~3 mm [1/8"] if none is available.

WRT ear plugs, that's a personal call since at low frequencies we can tolerate a lot more SPL for a lot longer time without damage than higher up in our acute hearing BW. Anyway, around/at Fs in a ~sealed cab shouldn't be all that loud sounding even right next to it with just a single LF tone at this low an excursion. Get up around 80-100 Hz though and its T Rex stomping on your head or you're at the intro to a Headbanger's Ball.......

GM

I've got a box that will hurt your ears, a DIY subwoofer in a small sealed box. The woofer was used for one of the Mfg.'s car audio teams, they doubled the magnet to about 40lbs. The thing will shake your drink across the room, if you want it to. I push it with a proaudio amp and use it for HT. I have it moderately playing below 80hz.

Sleds are drying on the first coat of finish, the Maple is very nice against the birch plywood.