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What to do with Altec 420Y Drivers?

Rex Everything said:
I have a set of Madrid cabs that the 420Y was no good in so they were modded w/ a 12" speaker from a model 14 and a nice Altec dome tweeter. I will probably go ahead and remove the dome and replace it w/ a horn at some point. This cab in this configuration is also in desperate need of porting IMO and will be the next project for these.
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The screws through the front at the edges of the baffle allow it to be removed?

The baffle IS removable, then? :dunno:
Tom Brennan said:
Mx---I think you're getting some bum advice, people transferring their notions and fantasies onto you.
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Regarding the "notion" part, see post #1, defining the mission, including exploration of the compression driver/horn option.

I am not aware of any large-format woofer and cone/dome tweeter that will combine to make a competent two-way. There's two octaves of "compromised" response left smack in the middle.

And as to the "fantasy," I have invited Mxlews to come by for a listen.... :thmbsp:

Redboy said:
That's one impressive pile of speakers!
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Well, I trust you noticed the pile of crossovers in front there, since you're now becoming initimately familiar with that part. ;)

dgwojo said:
I second that!!!
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Thanks Wojo! I should take a new pic; that one's over a year old now.

All two-ways, except the gratuitous L100 in the rear corner.

[Pesky things, they are.... :p: ]
 
Zilch said:
I am not aware of any large-format woofer and cone/dome tweeter that will combine to make a competent two-way. There's two octaves of "compromised" response left in the middle.... :yes:
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We can deviate from what you think is competent. The 420 even by itself without a tweeter makes a very nice sounding system. But that's just my opinion, it's not down from Mt. Sinai.
 
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Well I want to spend the money on horns and such and use these as my main speakers (replacing my Boston A150's), but I don't really have the money to do so. I guess I could sell some of my 'old' speakers..:scratch2:
 
Tom Brennan said:
We can deviate from what you think is competent. The 420 even by itself without a tweeter makes a very nice sounding system. But that's just my opinion, it's not down from Mt. Sinai.
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I don't know 420 from a hole in the ground, Tom, so I have no opinion in that regard.

Somebody asks about upgrading to a compression driver w/horn two-way, I give my current best advice, is all.... :yes:

mxlews said:
Well I want to spend the money on horns and such and use these as my main speakers (replacing my Boston A150's), but I don't really have the money to do so. I guess I could sell some of my 'old' speakers..:scratch2:
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If the baffle is indeed removable, you have plenty of options available.

It's not gonna cost anything to come up here for a listen and get some ideas.

Watch for Jackgiff's report on his Santana upgrade soon.

[Could be they'll suck, too, of course.... :p: ]
 
Analog Addict has a set of the Madrids and used a tweet from a set of Cerwin Vegas. He has a thread on it floating around here. There was no crossover to speak of just a cap on the tweet and the woofer running wide open. We tried an 811/808-8A combo on them and the CV tweeter seemed to integrate better. They are a very good sounding speaker the way he has them. Tom B is correct, the 420 woofers do not get any respect. I think good tweets and a simple XO (cap) and maybe an L-pad just to match the level between the two drivers is all that is needed. Good luck, have fun, and keep us posted on your progress.
 
Okay guys, how about some good tweeter suggestions for mounting over the woofer, or maybe even some very small horn drivers? Thanks!
 
mxlews said:
The baffle is not removable on this model. They are 872A's.
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Well, there's ways to handle THAT.... :p:

mxlews said:
Okay guys, how about some good tweeter suggestions for mounting over the woofer, or maybe even some very small horn drivers? Thanks!
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How small? What is the available space within which to work?

A pic would be helpful.... :yes:
 
The current tweeters mounted over the woofer are about 3 3/4" wide. If new ones were to be mounted over the woofer, they would have to be a little over 3". They could also be mounted to the top left or right of the woofer, I guess. That way I could mount bigger ones.
 
Stay away from that JBL copy lookin thing from PE for hifi applications, you'll be hard pressed to find 2 that sound the same.

The APT doesn't really go low enough to be used with a 1st order crossover at 3000hz

The Fostex while a great sounding tweeter, needs to be crossed at 5k or above.

The Vifa looks to be a very close match, it drops plenty low enough and it's sensitivity looks so well matched that no "padding" will be necessary.

Just my opinon y'all understand...........................
 
I think I'm going to try the Vifa. Since it's 6 ohms and the current tweet is 8 ohms, what will the overall impedance be? What size cap will I need? The current one between woofer and tweeter is 15uf. Or should I buy/make a simple crossover?
 
I cannot find an impedence graph for the 420. Usually a woofer's impedence rises with frequency at the upper end of it's range, the Vifa appears to have a nice flat impedence curve that doesn't drop below 6 ohms. Just a wild guess but i think that the 420's impedence should be high enough at 3khz that when paralleled with the Vifa the amplifier is still going to see an impedence of nominally not less than 8 ohms.

I didn't pay close attention so that 6 ohm rating on the Vifa might be "minimum" rather than nominal, it's graph certainly shows that to be the case.

I'm looking for a crossover calculator that does 6 ohms...............

FWIW, you can make any of the other tweeters "work", the Vifa route will be the easiest aproach and stay closest to the original design.
 
The current one between woofer and tweeter is 15uf.
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Does it look like it's ever been replaced?

According to this calculator: http://www.carstereo.com/help/Articles.cfm?id=55#first

a 15uF cap would bring the tweeter(8 ohm) in at 1300hz, no mystery there's blown tweeters.

According to the above calculator a 7.5 uF cap would bring a 6 ohm tweet in at 3500, and an 8.8uF would bring it in at 3000. I always like to use a couple different calculators to be sure they agree.
 
The original cap was 14uf and I thought it was dried out because I wasn't getting any sound out of the tweeters. I ordered new 15uf caps (there were no 14uf) from PE but that didn't fix the problem, so I figured the tweeters were dead.

I'm a total noob at crossovers, so thanks a bunch for the help. What do I enter in "Frequency" on crossover calcs?
 
Wow!, that just seems way too low for these old tweeters.

It's certainly easy enough to experiment with different values. Just remember the bigger the cap value, the lower the cutoff frequency or "knee" therefore lower power handling...................... and vice versa.

The most outstanding characteristic of the 420 is it's extended frequency range, so logic tells me that one would want to bring a tweeter in much higher than if trying to compliment a "typical" woofer.
 
Do you think I should go with the 7.5 or 8.8, or order both to try? The 420 doess have an extended range, but I don't want to have the tweeter coming in too high that I'm missing some sound, obviously. Should I order an L-Pad to adjust the tweeter?
 
I just had a thought................ the claimed frequency response of the 420 is 25hz to 14,000hz.

A 1.4 uF cap would give almost exactly a 14,000hz knee, and at only a 6db slope that would still have the tweeter working well below that point.

Could the original caps have actually been 1.4 instead of fourteen?
 
Do you think I should go with the 7.5 or 8.8, or order both to try?
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I don't want to make any suggestions until we hear from some of the other Altec and speaker guys, i think we have a small mystery as to the proper original cap value.
 
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