What to do with Altec 420Y Drivers?

[Bill Murray]

old threads never die…
So I have a pair of Altec 879a (Madrid) with the tweeter strapped across the 420y.
For the most part, they serve as stands for my Bozak Symphonies as I was never that found of the high end. When I finally got around to recapping them (14uf, really?) I decided to disconnect the tweeters all together. You know what, that’s a much nicer sounding speaker w/o the little paper cone tweeter. I seriously doubt as the late, great Zilch observed they go that high but w/o the tweeter, what’s there is really rather nice. Perhaps one day I‘ll play with adding another tweeter but given the number of speakers I have now, I sort of doubt it. Anyway my point is if you have a pair laying about you might try disconnecting the tweeter (two spade plugs right in front). I get the impression whoever designed the 420y knew what they were doing and the cheap little paper cone tweeter was more of a marketing department thing.View attachment 3290948View attachment 3290950

Well, since I ain't dead yet I will reply to some old threads (including my own) like my re-coning adventure with the Altec 420. Mine still sounds fine to me (it has the tweeter on the bracket plus another one of the same type that I added) and the treble is there, altho I am not sure which cone is putting it out. Someday I will disconnect the tweeters on one of the speakers and test it out and hear what happens. I think I heard somewhere that those tweeters were made by CTS for Altec. They are pretty big for a cone tweeter and have a rather heavy magnet. IIRC it added just a little bit to the total sound, prolly just beyond the capability of the 15" tweeter (!). I have hearing aids now which opened a whole new world of treble to me. TTYL.

 

[rider33]

when I took that tweeter out it looked like a $3-5 part to me. The 420a, however, is seriously stout and very well made. I think most peoples perceptions of the biflex are colored by either the cone tweeter in the Madrid or the ubiquitous CST ring in the Santana’s. Having owned both at one point & never really caring for either, I was rather surprised how much better it sounded to me with the tweeter removed. There is more than a little Altec magic in that big dual-coned, wide-band beast. ‘Sort of wish I had tried disconnecting the CST tweeter on the slate-top variant before I sold it.

 

[loudnoises]

when I took that tweeter out it looked like a $3-5 part to me. The 420a, however, is seriously stout and very well made. I think most peoples perceptions of the biflex are colored by either the cone tweeter in the Madrid or the ubiquitous CST ring in the Santana’s. Having owned both at one point & never really caring for either, I was rather surprised how much better it sounded to me with the tweeter removed. There is more than a little Altec magic in that big dual-coned, wide-band beast. ‘Sort of wish I had tried disconnecting the CST tweeter on the slate-top variant before I sold it.
View attachment 3291263

I've said it many times before, Altec sabotaged the Santana with that tweeter. Sounds infinitely better without. Makes no sense why they put it in and not even a level control.

They also advertised the 420a as a stepping stone, that it could do low end duty when you added a horn. A way to build up to a bigger system. Definitely wants a bigger box than the Santana provided.

 

[Bill Murray]

I've said it many times before, Altec sabotaged the Santana with that tweeter. Sounds infinitely better without. Makes no sense why they put it in and not even a level control.

They also advertised the 420a as a stepping stone, that it could do low end duty when you added a horn. A way to build up to a bigger system. Definitely wants a bigger box than the Santana provided.

You're getting me interested. I think I will try my tweeter test and use a L-pad too. BTW the 872 box always seemed a little small for a big speaker like that. It doesn't have a tubed port, just a cutout on the baffle that presumably is right for the internal dimension. Also, I think I used 2 different size caps for my tweeters.

 

[rider33]

A post-script on this one: I had a chance to do a frequency sweep on my 15” Bi-flex w/o tweeter assist. Just by ear mind you (no db meter) but output seemed strong up to about 7,000 hz. where it continued on for another ~500-1,000 hz. at an ever diminishing rate.
Then again my hearing much above 8-10k is not what it was use to be so part of that might be my ears as well. Still, a solid ~50-7,000+ without the muddling of multiple drivers or crossovers & coming from a very well built driver might explain why the 420a sounds so nice on its own. ‘Not sure I’d be listening to a lot of string quartets on them but acoustic jazz, ‘very nice. I stand by my original assertion: somebody who knew what they were doing took the time to get the 420a right. Unfortunately, somebody down the road slapped a parts bin tweeter on it and damaged its reputation. Used as designed, it’s a sweet unit.

 

[Guido57]

Messing around with a recently acquired Santana I was surprised at how well the 420 handled female vocals. Not sure where I'll cross them over yet but definitely not higher than 6K. I think reconning them into a standard woofer should only be done to basket cases.

 

[Bill Murray]

Messing around with a recently acquired Santana I was surprised at how well the 420 handled female vocals. Not sure where I'll cross them over yet but definitely not higher than 6K. I think reconning them into a standard woofer should only be done to basket cases.

Right, don't re-cone them the bi-flex is too unique to ruin. Would you know the handiest way to know how to mate a capacitors rating to a given frequency? Is there a table of some kind for this??

 

[Guido57]

What caps or other crossover components to choose depends on the high frequency driver options chosen. Plenty of crossover calculators on the net to get one close but unless one knows the impedance graphs of the drivers they are at best an approximation. And that's just to start, sometimes the best blending of drivers occurs with the drivers crossed at different points with different slopes. My current experiments are using a miniDSP as an active crossover and bi-amping allowing me to try different points and slopes. One could of course use the natural roll off of the bi-flex and just use a high pass for the tweeter section but the same principles apply. Personally I think going too simple on the crossovers for these speakers would make blending the two drivers difficult in most situations.

 

[Bill Murray]

What caps or other crossover components to choose depends on the high frequency driver options chosen. Plenty of crossover calculators on the net to get one close but unless one knows the impedance graphs of the drivers they are at best an approximation. And that's just to start, sometimes the best blending of drivers occurs with the drivers crossed at different points with different slopes. My current experiments are using a miniDSP as an active crossover and bi-amping allowing me to try different points and slopes. One could of course use the natural roll off of the bi-flex and just use a high pass for the tweeter section but the same principles apply. Personally I think going too simple on the crossovers for these speakers would make blending the two drivers difficult in most situations.

I am not trying to make rocket science out of this. I am using the bi-flex to just roll off, and I was just wandering what capacitor value would function as a high-pass filter for say, 8k, 9k, 10k up to about 14k so I could hookup various caps to the tweeter and see how it sounds. Approximate, estimate, guess all are OK.

 

[Guido57]

If you're looking simple first order the online calculators will do. Plug in the nominal ohm rating and desired crossover point. Just search for a crossover calculator.
Are you using the original tweeter? If so I would have to recommend replacing it. I've got to think even relatively low end domes would be an improvement.

 

[loudnoises]

The biflex has a mechanical crossover at about 1k, when the inner cone starts... uh... doing whatever it does. But at some point that metal dome takes over, which is really a bit of a stretch. If I was to add a tweeter (as opposed to the 511b crossed at 650hz), I would be crossing it around 5k, same point the tweeter is brought in on the Santana. But use a 5k low pass on the biflex.

 

[Bill Murray]

If you're looking simple first order the online calculators will do. Plug in the nominal ohm rating and desired crossover point. Just search for a crossover calculator.
Are you using the original tweeter? If so I would have to recommend replacing it. I've got to think even relatively low end domes would be an improvement.

I bought several of these CTS tweeters when one of them sizzled out. So yes those are the original. They sound OK to me as far as I can tell. But I haven't done my test yet so we will see how it all turns out in maybe a few weeks.

 

[Bill Murray]

The biflex has a mechanical crossover at about 1k, when the inner cone starts... uh... doing whatever it does. But at some point that metal dome takes over, which is really a bit of a stretch. If I was to add a tweeter (as opposed to the 511b crossed at 650hz), I would be crossing it around 5k, same point the tweeter is brought in on the Santana. But use a 5k low pass on the biflex.

isnt a low pass filter a coil rather than a capacitor?

 

[Guido57]

Whether upgrading from the CTS style tweeters would be significant to you depends on how far gone your hearing is. You'd only be able to tell by listening to some speakers with better tweeters. Adding a low pass (yes, coil) to the bi-flex would lessen the frequency range where the two drivers are playing the same signal.

 

[Bill Murray]

Whether upgrading from the CTS style tweeters would be significant to you depends on how far gone your hearing is. You'd only be able to tell by listening to some speakers with better tweeters. Adding a low pass (yes, coil) to the bi-flex would lessen the frequency range where the two drivers are playing the same signal.

So if the bi-flex is playing the same signal without distortion it wouldn't hurt to just leave it, and try the tweeter at different crossover freqs and test it that way. I have a hearing aid I use that definitely lets me hear things I can't hear without it. BTW I have a couple of Sansui 16 ohm tweeters I could try too, if the impedance difference didn't confuse the situation.

 

[loudnoises]

So if the bi-flex is playing the same signal without distortion it wouldn't hurt to just leave it, and try the tweeter at different crossover freqs and test it that way. I have a hearing aid I use that definitely lets me hear things I can't hear without it. BTW I have a couple of Sansui 16 ohm tweeters I could try too, if the impedance difference didn't confuse the situation.

I like to use an lpad as well as a 4uf cap to dial in or out the tweeter level. Even if the math works out perfectly it's still nice to be able to tweak the level. Especially if you're running the biflex at full.

 

[EarWhacks]

Must be some kind of record...17 year long thread, but glad I ran across it. Here we go...

I picked up a pair of Madrid 872A about three weeks ago, and have become fascinated with this 420 A / Y driver. Bought them to yank the drivers and sell but now I'm off on another WhatTheHellAmIDoing adventure. Once I got them home I could see that the cabinets were in better shape than I thought. Having some skill in audio as well as woodworking, I'm going to Frankenstien these baby's but with all Altec components. I have seen so many comments as to what to do with the 420...use alone, better tweeter, some type of horn. After much reading and watching a vid from the Chicago Horn Loudspeaker guys, this is my direction. I have a line on an inexpensive pair of Mantaray horns (endorsed by Tom & Kwing, the CHL guys) from a pair of Model 14 and just snagged a couple of Santana II xovers cheap on eBay. If it all stacks up and sounds good what I intend to do is craft a matching wood enclosure for the horns, something that will compliment the original cabs.
Only thing I can't decide...I have seen the 420 Bi-flex in a sealed cab (Madrid 872B) and these 872A which have a small vent in the baffle board. May take some experimentation and potentially wasting one baffle board to find out what works best. The guy I bought the xovers from actually has the port tubes from the same Santana II's. But what the hey...

Quite looking forward to any comments / suggestions arising from the resurrection of this thread and / or the 872A's.

 

[rider33]

As I think I had mentioned, I think it’s a very nice sounding speaker up to say 5-7k. Its sins are of omission, not commission. If I were to play with it I would let the 420 run wide open & add a horn with a simple high pass. That way you could change out the caps to see what sounded best to you, the horn really wouldn’t care what it’s mounted to as many were free standing anyway.

 

[bowtie427ss]

In the distant past i sold a few pair of 420 to fellas in eastern Europe who were getting very satisfying results using them in back loaded horns. JBL 4530 was their inspiration.

 

[EarWhacks]

As I think I had mentioned, I think it’s a very nice sounding speaker up to say 5-7k. Its sins are of omission, not commission. If I were to play with it I would let the 420 run wide open & add a horn with a simple high pass. That way you could change out the caps to see what sounded best to you, the horn really wouldn’t care what it’s mounted to as many were free standing anyway.

Yeah, everything I read suggests running the 420 full range, that's my plan... CHL guys suggested xover at 3.5k, the Santana II's go at about 2.5k from what I read, close enough to start. I've got active XO's and amps enough to bi-amp so I may doodle with that route just for S&G. The Mantaray horns supposedly have great dispersion, never heard one so looking forward to that. All good fun...