Model 14 crossover help

[Nickd]

I have been on a bit of a Altec acquisition binge lately and am starting restoration of the first pair of Altec's to arrive. A nice pair of model 14,s that need a bit of a restoration. I am sending the drivers to Bill for re-cone and new diaphragms in the 902's ( they are aftermarket rose colored anodized ).

I pulled the crossovers and noted they are series 1. Two inductors on the board. I plan a re-cap at least a through cleaning of the pots, mills resistors and some better wire leads. Sheesh those production guys were cheap. The hookup wire is really light (20ga.?)!

My questions are:
1. Does anyone know the best crossover schematic that leaves in the adjustment pots but looses the tweeter "overload protection" circuit. I would be ok with a fresh point to point crossover build using air coils etc.

2. If I have to stick with the original circuit and just change caps and resistors that's fine, but I would like to at least ditch the "protection" circuit if anyone has successfully accomplished that.

3. Does anyone know why the changes to the crossover over the production runs? Did the sound get better as the changes occurred or was it just save a few parts as money got tighter?

Thanks,
Nick

[Nickd]

After doing a lot of thread searching, I have come to the following conclusions.
The stock Altec M-14 crossovers are usually preferred over existing re-designs.
The inductors look horrible but actually sound good.
The overload protection while not "Purest" in nature may not be harmful to the sound.

Looks like I will re-cap and run with the stockers.

Still wonder if there is a known "best sounding" of an three factory versions?

[VolvoHeretic]

The only thing I have to say about speaker protection is that I wish I had had some when one day 15 years ago something went POP and took out the Staxs preamp, Soundcraftsmen EQ, one channel of the Crown DC300A, and the diaphragm and woofer of one of my A7-500's. Still haven't gotten the 416-8A reconed yet.

[Nickd]

I thought about bypassing the protection, but everyone who has left it in place seems to like the speaker as a whole. Perhaps it acts as a resistor in front of the 902?

Looks like the only questionable part in my pair are a leaky electrolytic cap that is easy to replace. Going to run stock for now and see how they sound.

Boxed up the drivers today to send to GPA for some well deserved love. The woofers were in desperate need of a total re-cone and the 902's have after market farms.

[voice of the theater]

The protection circuit is very unreliable. Unsolder the protection resistor from the top of the crossover. Then, unsolder the positive lead from the board and put it where the resistor lead entered the board. The circuit is now by-passed. See the photo. Attachment 3054

You may want to read this article before you waste too much time on it. Altec Lansing Model 14, Part 4: The Ultimate 14 - Audiophile Nirvana

I'd like to try to remove the protection circuitry from my Model 14's. Can you post a photo of the positive lead/what is the positive lead? Is it the positive wire that first connects to the crossover from the positive terminal at the bottom of the 14's?

[voice of the theater]

Follow this link for photos. Model 14 Mods - Audiophile Nirvana

Thanks! I'm going to bypass the protection circuitry. I don't need it and I don't want my signal passing through unnecessary circuitry. Model 14's are so efficient, they are almost deafening with 10 watts per channel. Even though I'm using a 150 watt power amp I'll never push them so hard that they are in danger...

[voice of the theater]

This is a duplicate post that I made today in my thread "Crossover Help Needed With Another Pair of Altecs". I think it may be helpful to the OP here, so please excuse the duplication.

Great idea--there's no way that I need the protection circuitry as these speakers are so efficient I doubt if I ever put much more than 10 watts per channel through them--they blow you out of the room if you go past that. Anyone out there know how to bypass the protection circuitry? I doubt if it will effect the sound but it just makes sense to not have the signal go through any more circuitry than is necessary.... Not sure if this schematic will help as it leaves out the protection circuitry..... (click on images for full size)

OK, I asked if anyone out there knew how to bypass the Model 14 crossover protection circuitry FIVE AND A HALF YEARS AGO (see above quote) AND I GOT AN ANSWER THIS WEEK! lol I guess patience really is a virtue. This forum has been SO helpful with me learning how to optimize, update, and recap etc. my Model 19's, Model 14's, and Santana II's--this is the first question I've ever asked here (that I can remember anyways) that "stumped the panel" for five and a half years. Well, I finally got my answer from (user name) Lansing 4112 who is part of the Audiophile Nirvana team. He sent me this link in response to my question:

Model 14 Mods - Audiophile Nirvana

I have finally bypassed the protection circuitry in my Model 14 crossovers! In post number 56 of my thread "Crossover Help Needed With ANOTHER Pair of Altecs" (page 6 of thread) I comment on how much better my Model 14's sound after recapping the crossovers with Solen caps (thanks to help from Earl K, GM, Altec Best, Aditya, etc. etc.). I comment on how the high end and clarity are both significantly/noticeably improved after replacing the 30 year old caps!

Well, now that I've finally bypassed the protection circuitry on the Model 14 crossovers, this week, I am happy to report that these things sound even better without having the signal pass through that 35 year old protection circuitry. There is a lot to that circuit--a good chunk of these crossovers (much of the electronic circuitry) comprises the protection circuitry. By bypassing it, I am left with just the basic crossover circuitry--much less unnecessary "gobbledygook" (technical term) for the signal to pass through. I am really impressed that the 14's now have even greater clarity (and they just plain sound clearer/cleaner) and a more defined sound than they did before the "bypass"! Also, very surprising, I'm getting more low end out of them. Apparently, having the signal pass through the 35 year old protection circuitry was having a derogatory effect on the low end of these speakers. I said after I re-capped the 14's that they rival my two pair of Model 19's. I did some extensive listening last night and this morning after completing this bypass, and with the increased clarity/more defined sound and enhanced (restored) low end from this bypass, it is now too close to call IMO which speakers sound best on most recordings--the 19's or the 14's. In fact, there are a couple of recordings that I did an A/B comparison (same song on the 14's and 19's) where the 14's actually bested the 19's! That has never been the case prior to this bypass--up until now the 14's at best sounded comparable (but different) to the 19's on some recordings and inferior on others. Now, post bypass (and of course 5 years post recap), I have recordings that sound better on the 19's, some that sound better on the 14's, and many that are too close to call---they sound amazing on both the 14's and 19's and it's really a tough call which speakers most recordings sound "better" on! THANK YOU TO EVERYONE HERE WHO HAS HELPED ME ON THIS JOURNEY WITH THESE AMAZING SPEAKERS!

DSCN4206.jpgDSCN4218.jpgDSCN4223.jpg

PICS OF BYPASS (1st pic is pre bypass, 2nd and 3rd are the two crossovers bypassed) As you can see, I've recapped these crossovers with Solens, and have bypassed the treble "pot" to reduce the amount of circuitry the signal passes through since the optimal range for the treble pot, according to Altec, is in the maximum range and they do sound best with that pot turned "all the way up". I use the mid pots so those are still connected---in their optimal range (about halfway up), the balance of bass to mid to treble is excellent. In a recent thread in this forum, someone asked which of the three versions of the Model 14 stock crossover sounds best, based on reports I've heard of some of the versions of this crossover sounding too "shouty", I'd say this version is probably the best. Sounds AMAZING! (this version is the one with the 10 uF and 2 uF caps)

[SaintOtis12]

Your diagram is very detailed and the instructions are easy to understand. Thank you very much. a great job!
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