Altec N801-8A Crossover Upgrade

[dgwojo]

I gutted the Altec crossover and upgraded it with Jantzen parts from PE and an Lpad from MCM. I didn't start the second one yet, I want to test this one out first. I had to install strips of aluminum on the rear cover as the air coils inductance was affected by the metal cover, I wanted 2.25mh coils but they didn't offer them so I used the metal cover to get it to that value, the caps are 18mfd, I can't wait to hear these, Dave. :yes:

 

[Gibsonian]

Very nice. Better ingredients = Better ouput. Good idea to do one so you can directly compare the before to after. Be sure to post your results.

 

[Russellc]

I gutted the Altec crossover and upgraded it with Jantzen parts from PE and an Lpad from MCM. I didn't start the second one yet, I want to test this one out first. I had to install strips of aluminum on the rear cover as the air coils inductance was affected by the metal cover, I wanted 2.25mh coils but they didn't offer them so I used the metal cover to get it to that value, the caps are 18mfd, I can't wait to hear these, Dave. :yes:

Yes please do give results!...Also, could you explain about the metal cover having an effect on the coils and adding aluminum or what ever, both cross overs look the same to me with the exception of the coils/caps. what part number of attenuator did you use from MCM? Was the original shot? Nice clean work, I have a pair of 501 8b crossovers that appear similar to these, similar attenuators, they sound quite good so I am a little gun shy about ripping them apart, ( they were nos in boxes), but am looking for a pair to operate on.

Thanks,
Russellc

 

[dgwojo]

Yes please do give results!...Also, could you explain about the metal cover having an effect on the coils and adding aluminum or what ever, both cross overs look the same to me with the exception of the coils/caps. what part number of attenuator did you use from MCM? Was the original shot? Nice clean work, I have a pair of 501 8b crossovers that appear similar to these, similar attenuators, they sound quite good so I am a little gun shy about ripping them apart, ( they were nos in boxes), but am looking for a pair to operate on.

Thanks,
Russellc

I hooked the XO up last night and the sound was excellent, I'm using GPA 515-8LF's not the 515-8G's for the woofers and 902-8B/511B's for the high end. The highs are crisp and clear and the snappy transient response was perfect to my ears. I would have compared the untouched and this one but the caps are no good on the other, the two caps are supposed to be 18mfd, one read 21 the other 14 so they're toast!! On a related note, the coils are supposed to be 2.25mh, they read 1.50mh and 1.65mh, nothing was in spec so out with the old components and in with the new. The original circuit design was maintained, no aleration. The LPad was on sale for $3.99 at MCM; Lpad 50-070
Your N501-8A will probably have 28mfd caps, the 400 wvdc replacement caps will be pretty large, these don't have much space in them. The air coils are affected by any ferrous metal that comes near them, I used a stainless steel screw to retain them, the aluminum strips are nonferrous so they won't affect the inductance value. While the XO was apart, I ran test leads to the coils through the Lpad opening and I positioned the aluminum strips on the housing to get the desired inductance. I can't wait to start on the other one, I actually use scrap 809 XO chassis' and just replace the parts on those and mount them to the 801 XO face plate, Dave.

 

[Russellc]

dgwojo,
Mine are 501 8b not 501 8a, likely there is no signifigant difference. It has been a while since I had them out for a look, they looked similar to what you are showing except the face plate is rectangular instead of square with the same sort of attenuator. May be I am remembering wrong, but it seems like I remeber a bunch of resistors in there as well that I dont see in your "before" picture. If so, what would you replace them with? again, maybe I am remembering wrong, but it seems like they were the typical cast looking kind, but I'm probably mistaken?

Russellc

 

[spkrman57]

I gutted the Altec crossover and upgraded it with Jantzen parts from PE and an Lpad from MCM. I didn't start the second one yet, I want to test this one out first. I had to install strips of aluminum on the rear cover as the air coils inductance was affected by the metal cover, I wanted 2.25mh coils but they didn't offer them so I used the metal cover to get it to that value, the caps are 18mfd, I can't wait to hear these, Dave. :yes:


Dave,

I see you used 511B horns with the 800hz crossover. How would you characterize the sound with 811B's?

Ron

 

[dgwojo]

dgwojo,
Mine are 501 8b not 501 8a, likely there is no signifigant difference. It has been a while since I had them out for a look, they looked similar to what you are showing except the face plate is rectangular instead of square with the same sort of attenuator. May be I am remembering wrong, but it seems like I remeber a bunch of resistors in there as well that I dont see in your "before" picture. If so, what would you replace them with? again, maybe I am remembering wrong, but it seems like they were the typical cast looking kind, but I'm probably mistaken?

Russellc

You're correct, the N501-8B is a completely different animal, it does have resistors in it and a completely different face plate. I think the components on that model are glued down, this makes replacemant a little tougher, Dave. :yes:

 

[dgwojo]

Dave,

I see you used 511B horns with the 800hz crossover. How would you characterize the sound with 811B's?

Ron

Ron,
I think the 811B would probably sound slightly better in the home environment where you can't enough distance away from the horns. I only use 511B's in my A7's, I keep the 811B's for the Model 19's, Dave.

 

[spkrman57]

Dave,

I run these on occasion with a 15" on the bottom(different types from time to time). My only complaint is the 811 seems to strain (using 800hz) compared to my GP 399 (1.4") drivers on the 311-60 and Edgar 500hz tractix horns.

I have better luck with Altec 1" drivers on 811B crossed over at 1600hz.

Just wondering if you have experienced the same thing!

Ron

 

[dgwojo]

Dave,

I run these on occasion with a 15" on the bottom(different types from time to time). My only complaint is the 811 seems to strain (using 800hz) compared to my GP 399 (1.4") drivers on the 311-60 and Edgar 500hz tractix horns.

I have better luck with Altec 1" drivers on 811B crossed over at 1600hz.

Just wondering if you have experienced the same thing!

Ron

Ron,
I've run into some "beaming" with the 811B, nothing that toning down the Lpad didn't eliminate, I haven't run into that with the 511B's, Dave.

 

[Russellc]

Ron,
I've run into some "beaming" with the 811B, nothing that toning down the Lpad didn't eliminate, I haven't run into that with the 511B's, Dave.

Have to agree, I prefer the 511B to the 811B.

Russellc

 

[grandville45]

How did this all ever turn out? I would like to try this with my 801's...

 

[dgwojo]

How did this all ever turn out? I would like to try this with my 801's...

My N801's work excellent, I don't have them installed anymore as I had to model other ones after them.

 

[grandville45]

Do U have a exact parts list? also where did u install those aluminum strips? inside the metal back cover? thanks!

 

[dgwojo]

I have the list somewhere, it's been about 5 years, the aluminum strips are inside the rear cover, they're white in the picture and are adjacent to the air coils when the cover is installed. I also used stainless steel nonferrous screws and hardware around the coils. All caps and coils from PE, 18uf Jantzen Cross caps (PE# 027-938), 18awg 2.2mh .84 ohm coils (PE# 255-268).

 

[grandville45]

Thanks! How is the strip mounted in the box? How thick is it? Looks like a pretty easy deal just unsolder and solder in the new components? Looks like u shrink wrapped all the leads too?

 

[dgwojo]

Thanks! How is the strip mounted in the box? How thick is it? Looks like a pretty easy deal just unsolder and solder in the new components? Looks like u shrink wrapped all the leads too?

The strip is glued with contact cement, it was cut from thin aluminum used for house siding or gutters, scrap leftovers from when my home was built. Yes, it's a matter of unsoldering and soldering the new components, it's not so easy to fit everything back in, you'll see when you do it, yes, heat shrink used throughout.

 

[grandville45]

Thanks! Question for you on the coils, How do coils go bad over time if there just wound roll of wire for a certain resistance? Or is there more to it? What did you use to test the coils also? I have a older fluke 12 here at work. Please help a novice understand

 

[dgwojo]

Thanks! Question for you on the coils, How do coils go bad over time if there just wound roll of wire for a certain resistance? Or is there more to it? What did you use to test the coils also? I have a older fluke 12 here at work. Please help a novice understand

I never ran into a bad coil yet, I just wanted to try air coils instead, I measure my coils with a good LCR meter. Some say to keep the original coils so the Altec voicing won't be lost? :sigh:

 

[grandville45]

I never ran into a bad coil yet, I just wanted to try air coils instead, I measure my coils with a good LCR meter. Some say to keep the original coils so the Altec voicing won't be lost? :sigh:

Oh I read in your other post about the coils being out of spec? So technically i could just change the caps?

I hooked the XO up last night and the sound was excellent, I'm using GPA 515-8LF's not the 515-8G's for the woofers and 902-8B/511B's for the high end. The highs are crisp and clear and the snappy transient response was perfect to my ears. I would have compared the untouched and this one but the caps are no good on the other, the two caps are supposed to be 18mfd, one read 21 the other 14 so they're toast!! On a related note, the coils are supposed to be 2.25mh, they read 1.50mh and 1.65mh, nothing was in spec so out with the old components and in with the new. The original circuit design was maintained, no aleration