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Alec 604-8G Crossovers

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Paully

Active Member
Specifically, what is wrong with them? I have a pair of 604-8G speakers, and they sound absolutely marvelous to me. But of course I read that the crossovers are a problem and need to be upgraded. Are the old crossovers really that bad? Just has me wondering how much of an improvement I am going to get versus the massive amount of trouble to get into the enclosures my specific pair were mounted in. So what was technically wrong with how Altec designed the originals? Thanks for any insight!
 
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Capacitors, change value with age and the internal resistance will increase. I would use the N1201 crossover so you can match the mid horn sound and upper horn tweeter sound to the woofer section. I always wished Altec would have developed a crossover for the 604 like Tannoy has for their big coax/ . The problem as I see it with the 604 is folks won't put them in a large enough enclosure to get rid of the port. We had a two customers that had 604c mounted directly to walls with the back radiating into storage closets, and they sounded fantastic. Totally different than ones in small ported cabinets. Mc 30's or 40s were all the amp you ever needed. Some others had 604 HPLN, that they used in conjunction with 416's or 927 trying to imitate Urei 813's. One college professor had his 604-8G mounted in slim 5 foot tall custom cabinets that were ported and had the best over all sound I ever heard with a 604. He was using the the N1201 crossover and Rane 1/3 octave room equalizers. .
 
Yes you will notice quite a difference when you replace the capacitors.

Do you have the regular 604G crossovers, or something else?

I built some Markwart designed crossovers for my 604G's and love them
 
I have, I think, regular Altec crossovers. They would have had to have been altered in some form of fashion for the Piezo (sp?) super tweeters that the speakers have. I suppose pulling these out and updating capacitors would be fairly easy? Unless they are potted, not sure on that. I am the type to let this just fester until I feel compelled to put in the Markwarts though. The speaker boxes are pretty darn big, as big as I can fit into my space.

I will have to look up what the N1201 crossover is referenced in the first post.

 
Paully said:
I have, I think, regular Altec crossovers. They would have had to have been altered in some form of fashion for the Piezo (sp?) super tweeters that the speakers have.

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Not necessarily, and probably not. You can connect piezo tweeters directly across the speaker leads and it will not damage them. In fact, this is how it is typically done. As the frequency drops, the impedience of the tweeter increases to (IIRC), about 70 ohms. I bet they just connected them across the horn terminals in parallel.
 
I would recap those and see how they sound. You could always add some bypass caps too

Or if you like how they sound just leave them as-is. Nothing bad is going to happen or anything
 
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Could we see a picture of the front of your 604 enclosures? Are you saying that piezo tweeters were added to the cabinet in addition to the coaxial hi frequency horn in the 604? As usual, I'm a bit confused.

GeeDeeEmm
 
gdmoore28 said:
Could we see a picture of the front of your 604 enclosures? Are you saying that piezo tweeters were added to the cabinet in addition to the coaxial hi frequency horn in the 604? As usual, I'm a bit confused.

GeeDeeEmm
Click to expand...

Happy too, a picture is worth a thousand words.

 
elitopus said:
I would recap those and see how they sound. You could always add some bypass caps too

Or if you like how they sound just leave them as-is. Nothing bad is going to happen or anything
Click to expand...

I like the idea of recapping first. The one thing I wouldn't want to do is ruin anything. I guess I just need to open up the crossovers and see if they are potted and what the values of the capacitors are.
 
Folks like Elitopus, who have experience with the 604s with the Markwart crossovers, can confirm or dismiss this notion, but I'm under the impression that the mid range attenuation accomplished in the Markwart accentuates the 604's high frequencies to the point of not really needing augmentation with super tweets.

I wonder what the Altec 30923 attenuator/equalizer would do for the 604? Would it accomplish the same thing?

Just curious.

GeeDeeEmm
 
I took a look at the crossover and it is not potted. The values are 6, 12, and 21uf. Not easily accessible but not impossible either. So I guess I will keep reading about what is wrong with the old crossover and what is accomplished with a new and decide what to do. Thanks for all of the input so far!
 
There's nothing wrong with the crossover.

It is the 604 itself that is flawed and riddled with little shortcomings.

The "problem" in a nutshell, is that the rather generic design and function of the 604-8G network does absolutely NOTHING to address any of the flaws or shortcomings of the 604.
 
bowtie427ss said:
There's nothing wrong with the crossover.

It is the 604 itself that is flawed and riddled with little shortcomings.

The "problem" in a nutshell, is that the rather generic design and function of the 604-8G network does absolutely NOTHING to address any of the flaws or shortcomings of the 604.
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+1

Which the Markwart or later 604 crossovers help to correct.

The drivers will still have some little issues, because of their design, but they sound so good its easy to overlook the flaws.

:music:
 
elitopus said:
Which the Markwart or later 604 crossovers help to correct.
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Without question, the best bang for the buck.

Mastering labs networks were very good too, but most were rolled for 16 ohm applications, and even those are hard, and generally quite pricey to come by.

For those so inclined and equipped, active bi-amping can yield the best results with 604's IMNSHO.

EDIT: did i really say "passive"?
 
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elitopus said:
Yes

I used Genteq oil caps, Jantzen coils, and Dayton resistors. All wired together with 12 awg copper wire
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Awesome, thank you! I am going to go ahead and build one. Worst case I spend a little money and switch back to the old. Best case, I have improved a pair of speakers that were phenomenal to begin with. What did you use for the 30 ohm pot?
 
Paully said:
Awesome, thank you! I am going to go ahead and build one. Worst case I spend a little money and switch back to the old. Best case, I have improved a pair of speakers that were phenomenal to begin with. What did you use for the 30 ohm pot?
Click to expand...

I left out the pot and used a fixed resistor in its place. I tuned the HF attenuation by ear, to what sounded good to me. Same thing you would do when adjusting the pot.

Its not for everyone, and requires some experimenting and a bunch of different resistor values.
 
elitopus said:
I left out the pot and used a fixed resistor in its place. I tuned the HF attenuation by ear, to what sounded good to me. Same thing you would do when adjusting the pot.

Its not for everyone, and requires some experimenting and a bunch of different resistor values.
Click to expand...

Buddy who helps me with this stuff had already mentioned putting in a fixed resistor in the end after deciding what I might like. What value did you end up with if you remember?
 
I'll have to go and check, but I want to say a combined 13 ohms. I emailed J Markwart about it and he told me to replace P1 and R4 with a resistor between 10-15 ohms.
 
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