Model 19 and 17

Hi GM,

Thank you for your time and patience for novices lke me. I will be trying both the typical vintage Altec tuning and the Fs tuning as you suggested with the vents up 3" from the bottom of the enclosures. BTW the enclosures still do not have the back and front panels attached. I'm thinkng of permanently attaching the rear panels and having the front ones detachable. What would be the pros and cons of doing it this way?

Thanks again for the guidance. Will post progress and results of this project.

All the best!
BugC

Greets!

You're welcome!

Well, the only potential 'cons' I know of is that you can't conveniently use a vintage style grill system and heavy drivers make them a bit unwieldy to deal with. FWIW, I began using removable front baffles for rear loaded drivers long before I first saw them on 846Bs, so my default recommendation along with not making them any bigger than necessary since the mounting system plus any extra permanently installed baffle section will add a significant amount of bracing. Never really understood why prosound cabs didn't use them from day one, especially for the ones where different size drivers were spec'd for them. Instead, they chose a typically flimsy adapter ring.

GM

Hi GM,

I truly appreciate your thoughts and advice on this project. After looking at the photo you attached, am considering adding a brace horizontally at the middle of the front baffle from where I could attach another brace connecting the front to the rear baffle. I could now have 2 detachable panels at the front (just like yours, if I'm not mistaken) for added flexibility! I could go bass-reflex or infinite baffle and experiment with different drivers and vent sizes. It sure is a lot easier making those removable panels than building new boxes for different drivers! ;-)

Thanks again and have a nice weekend!
BugC

Greets!

You're welcome!

There's three removable panels, two for drivers and one for the vent at the bottom (its screws are painted black whereas I never got around to painting the replacements for the driver baffles). For pipe vents it doesn't need to be removable since they don't have to be in all they way for testing, just temporarily sealed with soft putty. These are EBS alignments though, so due to the driver's specs a ducted port would be unnecessarily huge for high efficiency and a simple reflex port is fine if 'critically' damped as these are with a couple of pieces of expanded knit tightly stretched over the rear of them.

Anyway, they have the 'T' bars you're contemplating made with 2x4s.

A lot easier to rotate drivers that need it too!

Thanks, hope all ya'll have a fine weekend/holiday too !

GM

Hi Gm!
I didn't notice the third panel. I guess I'll settle for two panels for the mean time. My enclosure is not as big as yours. Might build something as big as yours but have to wait and see the wifey's reaction to the 10 cuft enclosures once completed! ;-)

Wasn't able to work on my project because of the rains. But I was able to make a baffle with a 2.5" x 11" vent for the 416-8C's. It's now playing along with the 811B horns with the GPA 902-8A's and the Altec N1201-8A x-over in an enclosure measuring 16.25" x 24.75" x 35.75" (outer dimensions). Got this from the Altec Library recommended enclosure for 15" duplex studio monitors. A pair of Altec 415-8A's Biflex were originally installed in these enclosures. The 416-8C's are there for break-in purposes only. Once my project is complete, the biflex will be back in those enclosures... Funny, but the 416's sound good in those enclosures. Bass is smooth and robust compared to the biflex. The biflex however has better vocals than the 416's! ... Well, just my observation.

BTW, how close together should I make the two 4" diameter ports. Would an inch apart do?

Thanks again and all the best to you!
BugC

Greets!

The 416-8C's specs are way different to earlier versions to better meet the changing needs of the prosound community, i.e. higher SPL in a smaller bulk and tuned higher due to the switch to SS power with its vanishingly low output impedance, so you don't want a really big cab unless driven with a very high output impedance. Really, the M19 is too large for it unless it's tuned lower to 'tighten' it up and/or several ohms of series resistance (total including inductor, etc. losses) is added to 'plump up' its slightly under-damped alignment referenced to one loaded with a 416-8A or 8B.

The bi-flexes OTOH ideally require huge cabs to keep them from sounding 'flabby'/'loose' (under-damped), but then average/peak SPL is reduced to keep various distortions low due to the attached/suspended inner diaphragm acting as a Doppler generator. Best of both? Probably bi-flex and 416 in a wall size IB or OB XO'd 1st order around 300 Hz as a first approximation.

Vents are no different than drivers or horns where mutual coupling is concerned, so < 1/4 WL of the XO's HF-12 dB apart and since vent tuning is a high Q event with HE drivers, using the tuning frequency is close enough. For example, 42 Hz = ~13560"/4/42 = ~80.7" on center, so from this we see that 'close enough' for multiple vents means anywhere on any practical size cab will have good mutual coupling.

GM

Good things take time. I started this tread 2 years ago.
After having had to back out of Altec plans for a while :( and playing with smaller speakers for a while, for example Swedish Carlssons (interesting orthoacustic speakers) and ProAc D28s, I got the opportunity to buy a pair of extremely well preserved Altec 604 8Gs in home-made 620 cabinet copies (well made). Which I did :cool:
So I'm now the happy owner of these classics. :D
I also got most of the parts for a J. Markwart crossover as part of the deal and will finish and test the JM crossovers once I get the remaining parts (are now enroute via FedEx).
With the standard crossovers the Altec Duplexes deliver fine music driven by a pair of old but renovated Quicksilver KT88s.
The 604 are everything I expected and more as they are warmer and more flesh and blood than I had dared hope for.
Thanks for the good discussions and a great forum

Best regards
Kjartan

Glad to hear you finally got ahold of some Altec's! I just finished a two-year speaker build and it was definitely worth the wait. I built a GM -designed MLTL cabinet for 416b and have 802g/811 on top with a Heil AMT. Anyway you do it, the Altec sound is incredible.

Thanks westend9, well invested two years :). What crossover are you using?
I was quite interested in something similar to your setup, but did not get there for many reasons. Im happy with the 604's and glad i got the opportunity to buy them. 604's are as rare as hens teeth in Norway, where I live.
Yes the Altec sound is great. I just did the J. Markward crossover for the 604?s yesterday and put some winged c KT88's in my old Quicksilvers and life is good... dynamic, resolved and good :D
Regards
Kjartan

Hey