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I present, the Altec MOTT.

loudnoises

loudnoises

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What's a MOTT? It's a Mutt of the Theater. Yep. I did that.

Long ago, before I had a clue, or any reason, or any idea what it involved, I decided I wanted a set of vott. A7-500 style. Huge, impractical, and annoyingly expensive. But awesome. Quickly realizing this wasn't practical or easy it's been squirreled away eating at the back of my mind.

First I scored me a pair of 511b. It was a start. Then the Santanas appeared and the gears began turning. Lots of reading and resisting, couple years of waiting, the path began to clear. Finally got altec horn drivers, built some z19 crossovers. Mounted the horns in an old set of ar-2 cabinets (the sizing is almost perfect) and hooked it up to my vta st-70.

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They're ugly and awkward, and not quite an end product, but they're real altec, just on a budget. And they sound good. 902-8b with original diaphragms, matching 511b, 420a on the bottom. Z19 in the middle. So far I'm enjoying the results. 97db for the 420a vs 99db for the 416 doesn't seem to be a huge mismatch but I know the room is helping me out with this. Gotta figure out how to use the mic I have and try to see how it's actually doing. Incidentally this also marks the completion of an entirely homespun audio chain. Vta st-70, my redone beta ii, ad797 phono stage, and overly tweaked 1219.

And I couldn't have done it without the help and knowledge of many of you. Thanks!
 
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I could see that being pretty outstanding. The 420A, according to some people I know (and who have great ears), may well have the best midrange of any Altec, and also has good bass. That, with the 902 (which may well be the best old-school Altec 1" throat driver), and the Z19 (arguably the best/most sophisticated Altec crossover design), should be able to produce great results.

Regards,
Gordon.
 
macyjrm said:
I like what you did there. Have you any more pics to share? Can’t tell much detail in this darkened room.
Click to expand...

Sorry about that, thy day got away from me. I'll update tonight with better pics.

GordonW said:
I could see that being pretty outstanding. The 420A, according to some people I know (and who have great ears), may well have the best midrange of any Altec, and also has good bass. That, with the 902 (which may well be the best old-school Altec 1" throat driver), and the Z19 (arguably the best/most sophisticated Altec crossover design), should be able to produce great results.

Regards,
Gordon.
Click to expand...

I appreciate the input, I've had to base much of this on posted data and the results of others. Graphs of the 902 on the 511, compared with the 811 and altec 14 mantaray, showed it to be a hair smoother. And you're not the first to hold up the 420a in high regards, they've made me happy just on their own as well.

I have dayton dsp i might put in the chain. I've been trying to do this right and the next step is actually testing out what I've made here. The bass has filled in a bit, and i began playing with horn placement. Lining up the coils sound better than baffle aligned, Altec says that means I do need to swap polarity of the drivers so I'll swap that tonight and hopefully the baffle line up will sound right. Lining up the coils had the horns sticking way out.
 
Some rear shots of the tops

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Horns are very secure, using some gym mat to wedge the back in seemed prudent though the horn is rock solid. The crossover will fit inside, but I need to remove the horn to get it in.

The ar-2 cabs were almost the perfect size. The corner screws are into the end panels so a hair wider might have been nice, but they were free. Totally recommended as a cheap solution. Plenty of these cabs out there.

They still have welded vanes. Don't know how motivated i am to cut them.
 
It's a week in and I'm still very happy with the results. Just need to sort it all out.

Phasing is still a work in progress. Need to open up the Santanas and see how the 420a are wired. I know the po had them open. Reversing the horns with the baffles aligned was good, but there was a specific vocal in one of my records that was notably quiet on both channels. Going to start from scratch.

How do I determine which of the horn terminals is the positive? (Or #2) One has a + scratched into the loading cap, but no other markings, and best i can tell that's the negative, but it's also where I think the positive would connect in an Altec 19... Currently I'm working with the altec phasing instructions where the baffles align and the horns get wired out of phase. So far this seems my best option as the other alignment options push the horns notably forward.
 
The diaphragm is marked on the hub, earlier issues will have + and - molded in the hub near the tabs, later issues marked positive with a red dot. You'll have to pull the loading cap to see the markings. But, you don't have to remove the diaphragm or otherwise upset it's relationship with the driver, just the loading cap.

I'd ignore anything scratched on the loading caps, they're older 800 series style caps, can't be sure they're original to the drivers.
 
It's been a busy week but I dug into one of the Santana's last night. White basket 420a in this one, no serials on the boxes, we'll see if the drivers are close. Yet another really pretty driver nobody will ever see.

Box has seen a hair of water, had to drill out the lower baffle screws. And the bottom brace has broken off the bottom panel so that's glued back in. Looks like the back bottom joint may have pulled out. (Stepped joints people, always.) Two layers of insulation on all sides.

Are these cabinets meant to be fully sealed? Or is a little air leak intended? The rear terminal is screwed across a hole, no way it seals, and the baffle has no real solid lip so it leaks a bit too. Should I try to seal them up?

I've looked to see if anyone tested it with the tweeter hole open like a port, but my google-fu is failing...
 
loudnoises said:
Are these cabinets meant to be fully sealed? Or is a little air leak intended?
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Sealed is a relative term here, versus ported for example.

I don't think leaks were intended so much as they're just inconsequential up to a point.

So long as you're not trying to achieve rock band sound reinforcement levels, i think they'll work favorably in just about any box that Altec put a 416 or duplex in.

I've sold 420's to folks in Eastern Europe who run them in back loaded horns.
 
Ok, one is together. One more Santana to rehab.

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So fresh, so clean. Made some new terminal plates and replacing the old jumpers (20ga? Seriously?).
20260406_202723.jpg

So now that I know the 420s are wired right inside, I can figure out how I'm "supposed" to wire these up. And of course, I've found 2 answers, both from altec. Baffles will be aligned.
Screenshot_20260406_211329_Chrome.jpg
Says both in phase. Ignoring terminal numbers, using polarity marked on the drivers. Cuz that's what I have to work with.

phase.jpg
Oh but wait, this one says horn out of phase...

What am I missing? Particulars of a driver? In the end it'll be done by ear and what testing I'm capable of.
 
loudnoises said:
Baffles will be aligned.
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But, what about the mounting flanges, will they be on the same vertical plane, or offset by the baffle thickness?

Consider that the true acoustic center of a 511 horn and driver combination is not exactly at the voice coil.

Having some adjustability of what Altec calls the directional relationship between the HF and LF sections might come into play. I'd opine that is one of the reasons the HF is mounted to a sled in the VOT systems.
loudnoises said:
In the end it'll be done by ear and what testing I'm capable of.
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I think this was always Altec's intention. Their instructions are a basic guide, good enough for most novice applications, and a starting point for the advanced enthusiast or professional installer.

Enjoy the journey! :)
 
I really enjoyed my Santanas. I recently gave them to my son as I had acquired some 846B Valencia’s.
My Santanas had the 16” frame 420-8B. So for grins I stuck the woofers in my Model 19’s. Sounded quite good! Very clear. Matched quite well with the 811’s and 902-8A.
That was like 20 years ago.
I was a bit surprised the bass was just fine given that those 420’s model best in a sealed box.

Fun project you have there. Enjoy!
 
RonSSNova said:
I really enjoyed my Santanas. I recently gave them to my son as I had acquired some 846B Valencia’s.
My Santanas had the 16” frame 420-8B. So for grins I stuck the woofers in my Model 19’s. Sounded quite good! Very clear. Matched quite well with the 811’s and 902-8A.
That was like 20 years ago.
I was a bit surprised the bass was just fine given that those 420’s model best in a sealed box.

Fun project you have there. Enjoy!
Click to expand...

Excellent to hear. The 420 seems to be an oddly hidden gem. Still don't get it. While anything altec is getting expensive, they're still accessible. I'm sure many were unnecessarily made into 416s, as they seem to have just about every bit of the abilities. While a full size 19 cabinet is probably bigger than i really want, the width of the horns i prefer does give me a bit more space to take up before I make the setup itself larger. So maybe some scaled down cabs would be nice, but that's a future project. I need to build up a bit of a wood shop first as well. Im also considering trying out a very lowly crossed sub.

Much of this is based on anecdotal experiences, I'm chasing a myth really. But they do sound good! I'm probably better off not having a great frame of reference, I'm not pursuing a memory just good sound.
 
I made 3 16” 420’s into 416’s. It’s the same frame and motor assembly. They were blown up and of course the bi-flex cones haven’t been available for many many years.
 
RonSSNova said:
I made 3 16” 420’s into 416’s. It’s the same frame and motor assembly. They were blown up and of course the bi-flex cones haven’t been available for many many years.
Click to expand...

I've been able to sometimes save the 420 cones, rebuilding them with new voice coils, spiders, surrounds and dust caps.

Not easy or guaranteed success, but it can work. Might not look "factory fresh" afterward after re-gluing the cones, but if it works properly and isn't ugly, I consider it a complete success.

Regards,
Gordon.
 
Good job. FWIW, I recommend you to folks over on the Haven should they need work done.

One of the ones I bought had been in a flood. Fortunately not up to the gap. That was a 420-8B

The other two were the large frame -8A with the welded magnets. Both had the voice coils jumped out of the gap and semi sideways. Bizarre.

Thanks for chiming in
 
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Have no fear, I've long ago decided these 420a will stay in Santana form. I just enjoy them as-is too much, aside from how well they're doing here. Doesn't seem to be a shortage of actual 416 woofers anyways should I decide i need a set. Would be a shame to ruin these.
 
Ok. NOW we're getting somewhere.

I've long held the belief that the 511b horns need the CD compensation.

Pretty sure I was wrong. I've modified my crossovers to convert the "hf" pot to a pure level control. Seems the coil and cap that are pulled from the circuit to do this were there to add cd compensation. Which was not doing good things for me! Oh the smoothness that has appeared. Just taken down a hair even and many issues have been resolved. Thanks @EarlK
 
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