Altec crossover upgrade
- Thread starter Billfort
- Start date
Seadweller
New Member
Hi gang,
I have what may be an ignorant question....Can the GE oil filled caps be mounted on their sides, or must they be mounted vertically? I'm getting ready to build the Markwart crossover, and this looks intriguing! Problem is, I made a removable panel to which the crossover is mounted on my 604 system, so I'll need to squeeze it into those dimensions.
Thanks!!
I have what may be an ignorant question....Can the GE oil filled caps be mounted on their sides, or must they be mounted vertically? I'm getting ready to build the Markwart crossover, and this looks intriguing! Problem is, I made a removable panel to which the crossover is mounted on my 604 system, so I'll need to squeeze it into those dimensions.
Thanks!!
Russellc
Addicted Member
does anyone have a guess as to how this crossover may work in an altec A7 with 416 8C and 802 8G opn 511B? I have wanted to experiment with something better than the original 501 8B that came with my A7s. Have also considered the M19 crossover as well, but didnt want to go to the expense if it didnt work.
Thanks, Russellc
Thanks, Russellc
Russellc
Addicted Member
Most A7s are either 500 or 800 hz, but there is no reason they necessarily have to be as far as I can see, the same driver (416 8C) is also used in some of the Model 19s. While I may be wrong, I cant see a problem with going to 1000 0r 1200 hz. Usually, for the uses they were intended for, (theater) everyone seems to want to cross at the lower points. I have participated on that forum for years and the only discussion I have seen are either "text book" crossovers, or model 19 "super" crossovers. I guess I could run plots to make sure the mid horn goes that high in the A7 box, as that is the only limitation I could see. The A7 crossovers dont seem to have the compensation for the high end that the crossover for the model 19 does. I guess I could replicate the crossover as is to get the benefit of modern parts and add the compensation circuit. anyone know off hand if the mid horn on the A7 would have problems properly integrating with the 802 8G on a 511B horn?
russellc
sleddogman
Super Member
As I get closer to finally attempting a crossover rebuild using motor run caps, could someone familiar with them confirm and comment on the above and then take a whack at another question?
(4.) I've seen those round motor start capacitors that are 2-in-1, e.g., they have a 30uF tap, a 3uF tap, and a common tap. Can the cap be wired and used as shown in the drawing and if so is the output value considered parallel? If so, this would solve trying to create one of the 33uF caps I need to use without using two separate devices.
Thanx!
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Paul C
Super Member
The A7's were later changed to 1200 hz for better power handling.
If 800 hz, you can KISS and buy the 2-way 800 hz crossover by Eminence from Parts Express. It would be difficult to build a better crossover any cheaper. Add a 100 w 8 ohm L-pad between the crossover and horn driver.
If 800 hz, you can KISS and buy the 2-way 800 hz crossover by Eminence from Parts Express. It would be difficult to build a better crossover any cheaper. Add a 100 w 8 ohm L-pad between the crossover and horn driver.
zekk,
They're 370ACV and I will wire them in parallel to effectively increase the capacitance to the desired value. For ex: (4x6uF)+1uF=25uF. I don't know the voltage that Bill used for his prototype, maybe 240VAC? I bought mine off Ebay for ~$3 ea.
BTW, I am NO expert, I'm kinda along for the ride. Any technical questions should probably be addressed to someone that knows this stuff, like Bill or Paul.
I'm really just copying Bills' concept of Jeffs' crossover.
They're 370ACV and I will wire them in parallel to effectively increase the capacitance to the desired value. For ex: (4x6uF)+1uF=25uF. I don't know the voltage that Bill used for his prototype, maybe 240VAC? I bought mine off Ebay for ~$3 ea.
BTW, I am NO expert, I'm kinda along for the ride. Any technical questions should probably be addressed to someone that knows this stuff, like Bill or Paul.
I'm really just copying Bills' concept of Jeffs' crossover.
I love the 800hz Eminence units from PE, 18db high pass, 12db low-pass, horn protection, I changed out the caps to Daytons and then mounted them to Santana crossovers for use in my A7 cabinets. I didn't go with other brands of caps becuase they all had higher working voltages that made the caps physically too large. I'm not sure if the higher grade caps helped any but the Daytons were an inexpensive upgrade. Dave. :yes:
kyle
Super Member
Russellc:
does anyone have a guess as to how this crossover may work in an altec A7 with 416 8C and 802 8G opn 511B? I have wanted to experiment with something better than the original 501 8B that came with my A7s. Have also considered the M19 crossover as well, but didnt want to go to the expense if it didnt work.
From what I understand, Jeff Markwart's crossovers are used to compensate for the physical offset (the distance) between the compression driver and the bass driver in the Altec 604 series speakers. He uses the phase difference at the crossover region to simulate a time delay and includes wiring one driver out of phase to give a coherent response. With an A7 you would need to look at the distance between drivers and measure the phase difference at the crossover.
This is a quote from Jeff's web page: "As I mentioned on the Home Page, horizontal separation between voice coil gaps for ferrite magnet Altec Lansing 604 & 904 duplexes is 2.8125”. This distance produces 112 degrees of phase shift between the driver’s acoustic centers at 1500Hz."
It's not a matter of picking a crossover point and attaching your drivers, you need more info.
I have built Xovers for several different 604's based on Jeff's design and they work really well, everything sounds better.
does anyone have a guess as to how this crossover may work in an altec A7 with 416 8C and 802 8G opn 511B? I have wanted to experiment with something better than the original 501 8B that came with my A7s. Have also considered the M19 crossover as well, but didnt want to go to the expense if it didnt work.
From what I understand, Jeff Markwart's crossovers are used to compensate for the physical offset (the distance) between the compression driver and the bass driver in the Altec 604 series speakers. He uses the phase difference at the crossover region to simulate a time delay and includes wiring one driver out of phase to give a coherent response. With an A7 you would need to look at the distance between drivers and measure the phase difference at the crossover.
This is a quote from Jeff's web page: "As I mentioned on the Home Page, horizontal separation between voice coil gaps for ferrite magnet Altec Lansing 604 & 904 duplexes is 2.8125”. This distance produces 112 degrees of phase shift between the driver’s acoustic centers at 1500Hz."
It's not a matter of picking a crossover point and attaching your drivers, you need more info.
I have built Xovers for several different 604's based on Jeff's design and they work really well, everything sounds better.
Billfort
Addicted Member
Zekk, I bought the GE motor-run caps off ebay for a couple bucks a piece – it took a few days to find a value that could be used in combinations to get what I needed but the low price allowed me to buy more than I needed and cherry-pick by measuring values. Don’t remember the vendor but a search for “motor run capacitor” or “oil capacitor” should get you lots of options. You can buy these things in an amazing range of sizes and manufacturers from the big electronics supply places (in Toronto I looked at Electro-Sonic and Sayal) but they are way more expensive – I much prefer the surplus route.
I’m not sure what audible effect the inductor change would have but you could always ‘unwind’ the higher value piece to achieve the desired inductance if you have a way to measure it. My tossed-together version of the Markwart certainly does look crude and I really have to pretty it up someday as Fran is doing but it does sound nice so I’ve found it easy to live with the ugliness.
I wouldn’t think the any of the Altec 604/605 crossovers would be optimal for an A7 – different crossover points, horn responses, driver offsets and relative efficiencies – the woofer in an A7 is horn loaded from about 100Hz up which is a very different situation. The 19 crossover might be closer but again, different driver offsets and no horn loading of the woofer.
I think you can get nice results with these drivers using textbook circuits (and added horn compensation) but tweaking circuits and components to suit the actual driver/speaker combination is where things can get truly special. I sure am grateful for the work Markwart has done for my particular drivers as they worked fantastic from the get-go and it’s now all down to packaging and component tweaking – too bad he hasn’t yet turned his attention to more Altec offerings.
I’m not sure what audible effect the inductor change would have but you could always ‘unwind’ the higher value piece to achieve the desired inductance if you have a way to measure it. My tossed-together version of the Markwart certainly does look crude and I really have to pretty it up someday as Fran is doing but it does sound nice so I’ve found it easy to live with the ugliness.
I wouldn’t think the any of the Altec 604/605 crossovers would be optimal for an A7 – different crossover points, horn responses, driver offsets and relative efficiencies – the woofer in an A7 is horn loaded from about 100Hz up which is a very different situation. The 19 crossover might be closer but again, different driver offsets and no horn loading of the woofer.
I think you can get nice results with these drivers using textbook circuits (and added horn compensation) but tweaking circuits and components to suit the actual driver/speaker combination is where things can get truly special. I sure am grateful for the work Markwart has done for my particular drivers as they worked fantastic from the get-go and it’s now all down to packaging and component tweaking – too bad he hasn’t yet turned his attention to more Altec offerings.
Russellc
Addicted Member
I had considered doing this before, but wanted the compensation,( which I could just add on I guess) to flatten out the high end. apparently the horn (Mid horn) stays loaded that high up. Parts are also smaller and less expensive at the higher crossover point! thanks for the tip.
russellc
Russellc
Addicted Member
I love the 800hz Eminence units from PE, 18db high pass, 12db low-pass, horn protection, I changed out the caps to Daytons and then mounted them to Santana crossovers for use in my A7 cabinets. I didn't go with other brands of caps becuase they all had higher working voltages that made the caps physically too large. I'm not sure if the higher grade caps helped any but the Daytons were an inexpensive upgrade. Dave. :yes:
Nice looking job there! I have thought about doing something similar to the 501-8B crossovers I have, but hate to destroy them, outdated though they may be.
russellc
I'm with you, I couldn't destroy some N501-8B's either, the Santana crossover was so chincy it just made sense!! :yes:
