Altec crossover upgrade
- Thread starter Billfort
- Start date
Paul C
Super Member
The 12v automotive bulbs can be seen in dwojo's photo of his modified Eminence crossover on page 1 of this thread. The bulbs are the tubular type that look like glass fuses. In the photo, this bulb is in the middle of the lower edge of the board, with an outboard capacitor next to it.
The bulb (or bulbs, two in parallel) are wired in series with the tweeter portion of the crossover. At higher voltage levels the bulb begins to heat and light up. As it does so it increases in resistance, thereby limiting the current going to the tweeter. As the voltage decreases, it cools, and resistance goes down. So it acts as a sort of "soft limiting circuit". It limits power to the tweeter, protecting it, with little audible effect.
No need for LED's... at really high music levels you can see the bulbs as a flickering glow coming through the ports.
The bulb (or bulbs, two in parallel) are wired in series with the tweeter portion of the crossover. At higher voltage levels the bulb begins to heat and light up. As it does so it increases in resistance, thereby limiting the current going to the tweeter. As the voltage decreases, it cools, and resistance goes down. So it acts as a sort of "soft limiting circuit". It limits power to the tweeter, protecting it, with little audible effect.
No need for LED's... at really high music levels you can see the bulbs as a flickering glow coming through the ports.
dividebytube
Well-Known Member
I would build a time-align crossover as used in some of the Urei monitor speakers - it wouldn't be that hard to configure it for a single 604.
http://www.jblproservice.com/pdf/Vintage JBL-UREI Electronics/UREI-811.pdf
One of the local speaker guys here built something like that for his 'nico 604s and by all reports it was a big success.
http://www.jblproservice.com/pdf/Vintage JBL-UREI Electronics/UREI-811.pdf
One of the local speaker guys here built something like that for his 'nico 604s and by all reports it was a big success.
Thanks for the input, Paul, the UREI's had bulbs in the x-over circuit, but I don't think I'll use them. I've been looking at Bill's version of Jeff Markwarts design for some time and because of Bill's experience with it, I'd like to build it.
Dividebytube, I've seen the schem for those x-overs, but the thing is, I want to simplify things a bit and I've read some very good things about Jeff's modifications to the Altec design. I'm going to keep things relatively inexpensive for now, and I've even thought about building a pair of the Altec 604-8G x-overs just for comparison. The UREI's are definitely something I'd like to build in the future. There were a pair listed in that auction site yesterday with some really nice pics that I pirated for future reference, and I have copies of the schem from that JBL site, as well. Currently I'm using nos 604-K x-overs I bought from GPA several years ago. They sound really good, but I've found that they need to be pretty heavily attenuated on the HF to sound good. Obviously there is room for improvement.
Thanks for the input!
Dividebytube, I've seen the schem for those x-overs, but the thing is, I want to simplify things a bit and I've read some very good things about Jeff's modifications to the Altec design. I'm going to keep things relatively inexpensive for now, and I've even thought about building a pair of the Altec 604-8G x-overs just for comparison. The UREI's are definitely something I'd like to build in the future. There were a pair listed in that auction site yesterday with some really nice pics that I pirated for future reference, and I have copies of the schem from that JBL site, as well. Currently I'm using nos 604-K x-overs I bought from GPA several years ago. They sound really good, but I've found that they need to be pretty heavily attenuated on the HF to sound good. Obviously there is room for improvement.
Thanks for the input!
Billfort
Addicted Member
Yes, looks like you've got it Fran.
I still haven't got around to putting mine in a proper box, eliminating the pot and moving to better resistors & connectors as I want to do but did recently try the stock cross-over again. It didn't last long as the Markwart definitely does a better job IMO.
I might also be interested in trying the UREI circuit reconfigured for the 604-8G at some point but I seem to get less and less time lately to mess with this stuff and I just enjoy the hell out of listening to music on the Altecs as they are now - system change dollars and time gets funneled into other areas.
I suppose that's a good indication that I like the Markwart just fine as-is and I should really 'button it up' properly and move on.
Thanks Bill,
When I finally get things going on this, I'll let you know. The hardest part is coming up with a "case" for them. It's probably going to be polycarbonate, as I have a piece of 1/2" inch at the shop that I saved for this. I'm going to build 2 separate boards per x-over and tier them. I think I've got the mental image configured.
Thanks again for the help!
When I finally get things going on this, I'll let you know. The hardest part is coming up with a "case" for them. It's probably going to be polycarbonate, as I have a piece of 1/2" inch at the shop that I saved for this. I'm going to build 2 separate boards per x-over and tier them. I think I've got the mental image configured.
Thanks again for the help!
judgeschreber
Well-Known Member
I had thought that the Markwart uses time-alignment as well. So, since it has this, as well as the mid-frequency compensation, what would be the advantage of the UREI crossover?
Well, I finally bought some parts...
I'm stoked!
It looks like I'm finally moving ahead on the Billfort inspired version of Jeff Markwarts 604-8G crossovers. :thmbsp:
I just received the electronics today, and have been working on the CNC program for the case components at work. I ran into some problems with an "undefined error...call for service" on the machine, a TRAK DPM 3-axis bed mill, so I guess I'll scrap that program and use the other CNC machine, an old Lagun Dynapath, it should be called a DINO-path, it won't hold better than .002", but it works.
I'm using 1.5" alum plate for the fronts, .5" acrylic for the sides, which will have the caps mounted to them, and the bottoms, tops and backs will be .25" plexiglass.
I decided to light them up with ultra bright blue LED's (hence the wallwart in the photo) and dispense with the fuse lamps altogether, in favor of not modifying the circuitry.
Hopefully by Thanksgiving, I'll have more pics to post.
P.S. Bill, not to hijack your thread, but I don't know if I ought to put this elswhere? :scratch2: Maybe one of the mods can chime in?
I'm stoked!
It looks like I'm finally moving ahead on the Billfort inspired version of Jeff Markwarts 604-8G crossovers. :thmbsp:
I just received the electronics today, and have been working on the CNC program for the case components at work. I ran into some problems with an "undefined error...call for service" on the machine, a TRAK DPM 3-axis bed mill, so I guess I'll scrap that program and use the other CNC machine, an old Lagun Dynapath, it should be called a DINO-path, it won't hold better than .002", but it works.
I'm using 1.5" alum plate for the fronts, .5" acrylic for the sides, which will have the caps mounted to them, and the bottoms, tops and backs will be .25" plexiglass.
I decided to light them up with ultra bright blue LED's (hence the wallwart in the photo) and dispense with the fuse lamps altogether, in favor of not modifying the circuitry.
Hopefully by Thanksgiving, I'll have more pics to post.
P.S. Bill, not to hijack your thread, but I don't know if I ought to put this elswhere? :scratch2: Maybe one of the mods can chime in?
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Billfort
Addicted Member
Interesting choice of components and layout Fran, looking forward to seeing how this turns out for you.
I keep saying I want to finish mine off with a pretty CNC carved box and to replace those resistors, pots and connectors but it keeps sliding down the project list - it just sounds good as-is.
I keep saying I want to finish mine off with a pretty CNC carved box and to replace those resistors, pots and connectors but it keeps sliding down the project list - it just sounds good as-is.
jaymanaa
RIP 1961-2018
Interesting choice of components and layout Fran, looking forward to seeing how this turns out for you.
I keep saying I want to finish mine off with a pretty CNC carved box and to replace those resistors, pots and connectors but it keeps sliding down the project list - it just sounds good as-is.
That's what happened to me too. I was planning on trying lots of different caps and values, so I made my crossover fairly "mod friendly". I haven't touched it since I hooked it up. It just sounds fine to me.
I'm hoping that will be the case. I respect Bill's opinion, and the changes I've made to my system, based on a lot of great advice here at AK, have been a great improvement to my listening pleasure. Plus it's just so enjoyable to "mess" with things I don't neccesarily understand.
That's what happened to me too. I was planning on trying lots of different caps and values, so I made my crossover fairly "mod friendly". I haven't touched it since I hooked it up. It just sounds fine to me.
It just dawned on me that I should have included your crossover as an inpiration also, Jay, it was your incredible ability to fine detail, that got me interested in acrylic for the housings.
Thanks!! :thmbsp: I fell in love with that crossover!!
Paul C
Super Member
To clarify about the automotive bulbs... they are available as a soldered pair from Eminence and sold by Parts Express. These are placed between the crossover and the horn/tweeter. This is for high power equipment, not for delicate dome and ribbon tweeters.
http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=290-659&CFID=10595330&CFTOKEN=23664564
Again, these are NOT fuses. These are light bulbs and work in the way stated.
And these are not for use with the woofers. For overall protection, you can still use a fast blow fuse between the speaker input terminals and crossover.
---
Jaymanaa: "I haven't touched it since I hooked it up. It just sounds fine to me."
:thmbsp:
http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=290-659&CFID=10595330&CFTOKEN=23664564
Again, these are NOT fuses. These are light bulbs and work in the way stated.
And these are not for use with the woofers. For overall protection, you can still use a fast blow fuse between the speaker input terminals and crossover.
---
Jaymanaa: "I haven't touched it since I hooked it up. It just sounds fine to me."
:thmbsp:
jaymanaa
RIP 1961-2018
This is exactley why I think my crossover was good to go right off the bench. I'm handy with tools and such, but am fairly clueless when it comes to any kind of circuit design. It was Paul C. that actually drew the schematic for mine, but beleive me, I read all the threads I could find by Bill and Wardsweb. What a wonderful thing we have going here. I'm just sure I would still be listening to BPC, if I was even listening at all. :thmbsp:
jaymanaa
RIP 1961-2018
And trust me Paul, that is a HUGE statement from a guy who has to fiddle with EVERYTHING. :yes::thmbsp:
Thanks, Paul, for the clarification. I'm thinking that when using my TAD-60 to drive my speaks, I shouldn't have to worry too much about over driving the tweets, but when I use my Adcom GFA555 for the loud rock and roll experience, I would like the piece of mind that the bulbs would give me. I will use the LED's for the lighting of the crossover cases, that should be pretty cool looking. Maybe I can just put some fast blow fuses in line after the crossover between the speaker cabinet binding posts and the tweets? Now that I think about it, this setup would also protect my tweets in the event I get around to biamping, as well.
Thanks for the pointers, everyone!
Thanks for the pointers, everyone!
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jaymanaa
RIP 1961-2018
I have thought about adding a little something for the ultra high frequencies, since I got a good report on my last hearing test. :yes:
