Help w/ Altec Model 15 crossover - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 7th October 2011, 08:29 PM   #1
diyAudio Member
 
Join Date: Aug 2005
Default Help w/ Altec Model 15 crossover

I own 1979 Altec Lansing Model 15 loudspeakers and rebuilt the crossovers. Now I have a extremely low volume. Can you please recommend the next course to take to resolve it?

The story:
I replaced the caps w/ Solen and rewired it. Upon reassembling the speakers the sound is now very quiet.
I rechecked my assembly hookup to my hand drawing of the factory x-over schematic. (The schematic and crossover photo posted below) Note that the woofer runs full range and the crossover only affects the horn.

When I hook the speaker wire direct to the binding posts it produces an almost un-hearable volume. When I touch the speaker leads direct to the woofer I hear the same until I remove one of the x-over leads, then the woofer sounds normal, of course I can test the horn. So the problem is with the x-over.

Let me clarify. The xover only operates the horn, but if it is in the system because it isn't bi-wired. The woofer sound is very muted. If I remove at least one x-over lead from the binding post the woofer sounds fine, but of course there is no way to test the horn.

To do another test it I took one x-over to a friends, hooked up another woofer and another tweeter and a vintage amp it it worked fine. I bring it home and hook it in the Altec Model-15 speakers/ Carver Receiver 900 and it doen't work again.
I'm using a Carver receiver that worked before the x-over rebuild that powered the M-15 w/o issue. The Carver has no problem driving other speakers, only the Altecs. Furthermore, using the M-15 if I turn the volume up the protection circuit clicks in until I turn it back down, like there is a short somewhere, yet the x-over worked w/ other components at my friends.

It's crazy. Bad caps, bad pots, etc? What should I test?

Any suggestions? (I've have built many crossovers and have rebuilt many others and have never experienced this, but there is a first time for everything.) A simple project has become a little more complicated.

Attached:
x-over drawing
x-over rebuild photo (I since redid it in its entirety from scratch but using thinner Kimber Kable instead of the 14 ga. Audioquest as in the photo.

Regards,
Mike
Attached Images
File Type: jpg Altec Model 15 x-over002.jpg (316.8 KB, 130 views)
File Type: jpg two x-overs_2249.jpg (222.9 KB, 109 views)
File Type: jpg system right_2150.jpg (239.9 KB, 107 views)

Last edited by mjatabor; 7th October 2011 at 08:48 PM.
  Reply With Quote
Old 7th October 2011, 09:45 PM   #2
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
I'm not quite sure I understand, so I'll ask a few questions:
  • If you connect the amp directly to the woofer, what do you get?
  • If you connect the amp to the horn via a cap (say 8uF and keep the volume low) what do you get?
  • Can you isolate or bypass any sections of the new crossover with jumper leads to test it?
I don't see any problems in the schematic, hard to tell in the photo.
__________________
Take the Speaker Voltage Test!
  Reply With Quote
Old 7th October 2011, 10:01 PM   #3
diyAudio Member
 
Join Date: Aug 2005
Pano,

If I hook the amp direct to the woofer while it is connected to the speaker binding posts shared by the x-over and horn it plays very quite. If I remove at least one lead from the binding post connection to the woofer, and then connect the amp to the woofer it plays normal volume.

The xover is laid out nicely to isolate, but do I need to desolder, or can I just use jumpers as in the case of using 8uf cap and horn?

Should I test caps and inductors? I'm willing to buy a cheap $50 cap/inductor meter, as it would be a wise investment for me.

Could I have applied to much heat in soldering w/ my small 15 watt (?) iron to have damaged the Solen caps, pots, or inductors?
  Reply With Quote
Old 7th October 2011, 10:26 PM   #4
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
I doubt you hurt the inductors or the pots, maybe the caps. But even if the caps were shorted, it should not cause a short from + to -. If connecting the crossover causes a big drop in woofer volume then you are right to suspect a short.
You may have to look hard and start unsoldering some stuff.

Double and triple check your wiring (yes, again) then start unsoldering the parallel elements one at a time. That would be the pots and the 1.2mH inductor. That's the way to start.
  Reply With Quote
Old 7th October 2011, 11:22 PM   #5
just another
diyAudio Moderator
 
wintermute's Avatar
 
Join Date: Aug 2003
Location: Sydney
Blog Entries: 22
I'd be looking very closely at the 3uF cap. If it is shorting you have a big coil shunting in parallel with the woofer. You could try disconnecting one end of the 1.2mH coil and see what happens....

Tony.
__________________
Any intelligence I may appear to have is purely artificial!
Some of my photos
  Reply With Quote
Old 8th October 2011, 02:33 AM   #6
diyAudio Member
 
Join Date: Aug 2005
OK. I actually rebuilt the xovers 2x. After finding the problem I rebuilt them w/ the same components, but replaced the 14 ga wire w/ small gauge to make sure my solder joints were clean. At that time I pulled the woofer wires from the binding posts instead of off the xover post. I know the circuit is laided out correctly.

Tomorrow I will begin you all suggestions. First jumping across the MF pot and then by disconnecting one end of the 1.2mH inductor coil. I will get back with you with my findings. I wish I had a meter to measure capacitance to test that 3uf cap.
  Reply With Quote
Old 8th October 2011, 02:39 AM   #7
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
Do you have a cap you could put in it's place that is near the same value? Like +/- 200% Just to test.
  Reply With Quote
Old 8th October 2011, 02:41 AM   #8
tb46 is offline tb46  United States
diyAudio Member
 
Join Date: Jan 2006
Location: Texas
Hi mjatabor,

Just lift one leg on your 3uF capacitor, this should immediately tell you if the crossover is shorting out the woofer.

Regards,
__________________
Oliver
  Reply With Quote
Old 8th October 2011, 02:30 PM   #9
diyAudio Member
 
Join Date: Aug 2005
Default I found the problem.

I found the problem, at least on the one speaker I tested, but the other is probably the same. Thankfully its not the caps.

The cup that the binding posts are mounted on is conductive. (see attached photo of cup) It doesn't feel like metal, but if it is painted cast aluminum it is conductive through the paint and a poor design. This is why the x-over worked with just the x-over and speakers when testing with my friend, and didn't work when installed in the speakers at home.

I replaced the cheap factory push-spring speaker wire posts for beefy gold plated brass posts that bite the cup firmly. (see attached photo) I was so concerned with x-over issues I didn't notice the cups. Now I will need to coat the through-bolt and use some type of insulator on the front and back of the cup. What is funny is that the factory speaker pot metal wire posts didn't use insulators either, but the posts I installed dug in and make a good contact. When I tested resistance with my $10 cheapo MM on the post cup I get a small reading on the cups surface, and the same reading from + post to - post. Crazy isn't it.

Has anyone experienced this? I've read where the glue used to adhere caps in some vintage amps becomes conductive over time.
Attached Images
File Type: jpg binding posts stacked_2256.jpg (214.2 KB, 76 views)
File Type: jpg both post types_2286.jpg (92.8 KB, 70 views)
File Type: jpg binding posts_2232.jpg (256.3 KB, 17 views)

Last edited by mjatabor; 8th October 2011 at 02:40 PM.
  Reply With Quote
Old 8th October 2011, 05:23 PM   #10
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
Duh! The obvious problem that we all missed. Well, it was a short.
I don't have experience with conductive glue, others might.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
altec lansing model 6 superfunk Multi-Way 1 13th October 2011 06:29 PM
Altec 604e/Alpha 15 Open Baffle? dgator Multi-Way 13 7th February 2010 08:52 PM
WTB: Altec 15" Woofer vmanp Swap Meet 6 1st July 2008 08:39 PM
Altec Lansing Model Three Neville Multi-Way 9 2nd October 2007 08:33 PM
si t amp with altec model 288c driver. tade Class D 13 12th May 2006 11:00 AM


New To Site? Need Help?

All times are GMT. The time now is 11:33 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2