Altec N801-8A Crossover Upgrade

[dgwojo]

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

Technically you could just change the caps but I feel as you do, most of these coils when measured out of circuit are out of the 20% spec, probably made that way as I doubt they drift over time.

GPA 515-8LF's, I have serial numbers 3 and 4, I guess Bill kept 1 & 2?? My Altec versions are Alnico, same as the 515C, the GPA's are ferrite.

 

[grandville45]

I will probably just do the caps and see what diference it makes. I only have one 416 8A right now need to send the other one into bill for a recone too. These are still a 800 crossover then? Or did u change it? Would it be better to say 1200? Fwiw that was your cut and paste above just incase u didn't know Are the 515's much louder than the 416?

 

[Maxamillion]

If you are attempting to replicate the above rebuild, you might want to rotate one of the air-core inductors by 90 degrees, as stacking them directly on top of each other will definitely cause cross-talk between them, which is not a good thing. Here is a link to a guide for inductor positioning that has some recommendations, and some DIY experiences:

http://techtalk.parts-express.com/showthread.php?p=1500176

 

[grandville45]

I have the same crossovers, case and all just want to update the electronics in them like he did,not trying to build the whole thing if I understand you correctly? Nice link by the way!

 

[dgwojo]

I will probably just do the caps and see what diference it makes. I only have one 416 8A right now need to send the other one into bill for a recone too. These are still a 800 crossover then? Or did u change it? Would it be better to say 1200? Fwiw that was your cut and paste above just incase u didn't know Are the 515's much louder than the 416?

Still 800hz, yes, the 515's are more efficient than the 416 but some people like the 416 better for depper bass, I solved that issue by using both!!

 

[dgwojo]

If you are attempting to replicate the above rebuild, you might want to rotate one of the air-core inductors by 90 degrees, as stacking them directly on top of each other will definitely cause cross-talk between them, which is not a good thing. Here is a link to a guide for inductor positioning that has some recommendations, and some DIY experiences:

http://techtalk.parts-express.com/showthread.php?p=1500176

Not enough real estate on this crossover to mount them any other way.

 

[Zekeman]

I have a pair of n801 xos without the back covers .... Do I need then for proper operation?

 

[dgwojo]

I have a pair of n801 xos without the back covers .... Do I need then for proper operation?

I didn't measure the inductance without the covers but I think you'll be OK, if I did measure it with the covers on, I was trying to get 2.30mh for a crossover point of 780hz, I think the cover with aluminum strip dropped the crossover point down about 20hz.

 

[drummerB]

Rebuilding N501-8As Need advice

I would like to do the same upgrade on my X-overs. What induction and Cap values would be closest to original Altec spec?

 

[dgwojo]

The last ones I did I bought 16 of the 18mfd caps and selected 4 that measured 17.5mfd, and used 2.5mh 18awg coils that measured 2.25mh, all parts from Parts Express, don't use the black metal back covers on the crossovers with these values, Dave.

Coils

Caps

 

[drummerB]

The last ones I did I bought 16 of the 18mfd caps and selected 4 that measured 17.5mfd, and used 2.5mh 18awg coils that measured 2.25mh, all parts from Parts Express, don't use the black metal back covers on the crossovers with these values, Dave.

Coils

Caps

So, this would give me an x-over at 780hz? The N501-8A x-overed at 500hz. Is it better to go higher? I have a 416-8A and 808-8A with 511B horns.

Thank you for your response.

 

[dgwojo]

Hi, I went by the thread name, not your post regarding the N801-8a vs N501-8A, I haven't converted a 500hz yet, hopefully the parts will fit? :scratch2: The values I mentioned crossover at 800hz (17.5uf/2.25mh), for 500hz the calculator say 28.13uf, and 3.6mh for 2nd order Butterworth.

Calculator

 

[drummerB]

Thanks for the reply.

Having trouble finding air core inductors with the 3.6mH value. Parts Express has an Erse Super Q solid core inductor with that value but everyone recommends the air core. Any thoughts??

Also, I can't find caps with the 28uf value on PE site and as I am a novice regarding these things, I am wondering if there is a way to achieve this with wiring in series or parallel with 14uf caps??

 

[dgwojo]

Thanks for the reply.

Having trouble finding air core inductors with the 3.6mH value. Parts Express has an Erse Super Q solid core inductor with that value but everyone recommends the air core. Any thoughts??

Also, I can't find caps with the 28uf value on PE site and as I am a novice regarding these things, I am wondering if there is a way to achieve this with wiring in series or parallel with 14uf caps??

I use a 10 and 18mfd in parallell to get 28, the coils usually measure different than they're rated so short of purchasing and measuring them it's hard to say what you'll actually end up with. Altec used 20% tolerence so getting it right on is not alway's possible, an LCR meter is what I use. E-mail me if you need some suggestions, Dave.

 

[drummerB]

Hi Dave,

I actually went ahead with your project specs as I wanted to use 811-B horns due to small listening room. Completed the upgrade over the weekend and am pretty darn happy with the results. I no longer have a true N501-8A but like the higher x-over point.

I appreciate your help on this.

Bob

 

[dgwojo]

Excellent Bob, do have any pictures to post?? :scratch2:

 

[Mustsail]

Variation on a theme.

Variation on a theme.

Variation on a theme. My N809-8As had seen better days. They smelled burnt. I became suspicious because I’ve blown more diaphragms in my Altec 802s in the last 6 months than in the prior 30 years. I rebuilt mine following Dave’s strategy, although I used 1.5 micro Henry coils and 12 micro Farad caps for a slightly higher crossover point: 1200 Hertz according to the DIY Audio crossover calculator. All parts are from PE. I use 2-12 midrange cabinets along with my homebuilt A7 style bass cabinets, so I hope the higher crossover point will be appropriate.
I had difficulty fitting the new coils where the old coils were, so I mounted them above. The wooden blocks are just spacers.
Here is a picture of the assembly. I’ll post when I’ve given them a good testing.
Chris,
NH

 

[dgwojo]

Variation on a theme.

Variation on a theme. My N809-8As had seen better days. They smelled burnt. I became suspicious because I’ve blown more diaphragms in my Altec 802s in the last 6 months than in the prior 30 years. I rebuilt mine following Dave’s strategy, although I used 1.5 micro Henry coils and 12 micro Farad caps for a slightly higher crossover point: 1200 Hertz according to the DIY Audio crossover calculator. All parts are from PE. I use 2-12 midrange cabinets along with my homebuilt A7 style bass cabinets, so I hope the higher crossover point will be appropriate.
I had difficulty fitting the new coils where the old coils were, so I mounted them above. The wooden blocks are just spacers.
Here is a picture of the assembly. I’ll post when I’ve given them a good testing.
Chris,
NH

Interesting mounting, wonder if the metal surrounding will impact the inductance? :scratch2:

 

[Mustsail]

Metal and inductance

Hi Dgwojo,
I guess it will, somewhat. If it moves the crossover frequency up or down a bit, I won’t mind too much. I hope it doesn’t affect efficiency.
Dave’s design has metal on two sides, this mounting is less than three; I removed some of the short flange edge. When the cover is on, there is metal on four out of six sides. I could put some aluminum around, but I’m not exactly sure what that would do and I thought I’d test it first.
I also am uncomfortable mounting the coils end to end, which is supposed to be taboo. Again, Dave’s setup is the same. I put them as far apart as possible.
All I have done, so far, is run test tones through the system. It seems to function, in that highs are going to the high output, etc.
I won’t really crank this system up in a big room until February.
I have added a second power amplifier and an electronic crossover, so the passive crossovers have become a back up configuration. I will test them then as rigorously as I can at high volume with test tones and recorded music.
Chris
NH

 

[Mustsail]

Results

I set up as a DJ system for a school dance Friday. I let the students DJ with Ultra mixer software (check it out if you want to DJ, free download, fantastic program) loaded onto a laptop and into the system. I configured the Crown D400 into the rebuilt 809 crossovers. They worked as well as the originals. I could not discriminate any difference, even with having moved the crossover frequency up to 1200 Hz. The 802 horns still sounded bright and clean.
Then I re-configured to my DOD electronic crossover. I had put fuses (10 amp, slow blow) in line with the crossover low frequency out, so I could, by removing the fuses, completely disconnect the crossovers.
Wow. I hate to say it, but the electronic cross-over, even this DOD $100 one, is massively superior to passive cross-over-ing. Also, I could adjust the crossover frequency and decided the whole system (1 15” A7 type cab in parallel with a Fender 2 12” Band Master for some mids (the 12” are 8 ohm, in series) sounded best with a crossover at about 1500Hz. The lows used the Crown D400 and I used a 1979 Kustom 60+60 rms watt amp for the highs.
It was a great dance (white out). The kids had a lot of fun, and I was able to play around with my equipment at high volume.
Mustsail