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Multi-Way Conventional loudspeakers with crossovers

Altec 605a duplex crossover upgrade
Altec 605a duplex crossover upgrade
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Old 25th October 2017, 05:12 PM   #11
WBS is offline WBS  United States
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Altec 605a duplex crossover upgrade
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Originally Posted by mrmky View Post
To my ears they sound pretty good now, but I canít get it out of my head that they could be better....
I agree. The imaging is spooky at times! I can't believe the way you can pinpoint instruments on the sound stage. I've read about it, but never really experienced it this way until I got these things. Hearing Artur Rubinstein's piano bench creaking kind of freaked me out at first!
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Old 25th October 2017, 09:39 PM   #12
kaputt is offline kaputt  Germany
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Originally Posted by WBS View Post
Thanks for sharing your experience. I'm currently trying to overcome the muddy bass you referenced as well as fatiguing mids. Would you be willing to share your schematic?

By loading cap do you mean the 6uF C4 in the Markwart schematic? Did you keep all resistors as designed? Finally, where did you insert the autoformer? and what are its specs?
It's bedtime, I'll draw up the crossover schematic tomorrow.
The loading cap is an actual plastic cap at the back of the compression driver, limiting the space behind the diaphragm. I have never taken apart a 605 but the 604s and 802s have these. They are necessary to protect the diaphragm in pa use with high power. On a 604 you take the back cover of the driver and there is a plastic cap. Remove that and you have access to the diaphragm. Line the outer cap with thick felt and put it back on with shorter screws, leaving out the inner cap.
No idea if the 605s have that inner plastic cap, but it's easy to check.
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Old 25th October 2017, 11:50 PM   #13
Skip Pack is offline Skip Pack  United States
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605s (mine are B's) have the caps in the back. I took mine out and made and exit horn-like back piece from wood and now use the compression driver in dipole mode with low powered amps. You need to get shorter screws to hold the diaphragms in place. I got stainless screws.

I'm curious about your autoformer attenuators on the tweeters. Did you have to do much work/experimentation to get the right loading?

Skip
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Old 26th October 2017, 02:13 AM   #14
WBS is offline WBS  United States
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Altec 605a duplex crossover upgrade
Okay, now I remember what the loading cap is and reading Jeff's comments about removing it. I'll look around for some thick felt. Michael's Stores maybe?

Skip Pack, do you have a picture of the wood piece you mentioned? It sounds interesting. How do you have your drivers mounted?
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Old 26th October 2017, 08:34 AM   #15
kaputt is offline kaputt  Germany
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GPA604.jpeg

Here's the schematic of my current crossover. Capacitors are relatively uncritical, low ESR polypropylene is a plus. L4 is cored inductor, DCR 0.07 Ohm.
The autoformer L5/L6 is set to -12dB, R3 is the shunt resistor setting the impedance seen by the high pass filter. R3 lets you pick an impedance to play around with smaller C, which then has to be made up with larger L of course.

Picking R3: it can be calculated easily. I did that as a start, then checked behaviour of the crossover on a scope and lastly put a rheostat in that position and measured different settings.
As what worked for me here is for different drivers in a different cabinet it can only be used as an inspiration, you will have to measure anyways.
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Old 26th October 2017, 04:02 PM   #16
WBS is offline WBS  United States
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Altec 605a duplex crossover upgrade
Thanks for posting Kaputt!

One last question (for now ) what cabinet do you have your 604s mounted in?
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Old 26th October 2017, 04:56 PM   #17
bentoronto is offline bentoronto  Canada
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Altec 605a duplex crossover upgrade
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Originally Posted by mrmky View Post
Thanks for all the feedback! I hadn’t ever thought of an active crossover and bi-amping, I might have to try that after I have some extra amps kicking around.
Dotneck is absolutely right. Hard for me to imagine reasons why anybody would settle on the crudeness of crossovers today. Makes no sense. The only reason people say nice things about crossovers is their adaptation to it. Once you cobble together those crude components, you are stuck with whatever you've got, room acoustics be damned.

On eBay, you can get a Behringer CX3500 (?) electronic crossover* or much, much, much more wonderful, the DCX2496 DSP.

B.
*and add a fried-egg dome tweeter on top for a few pennies
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Old 26th October 2017, 05:15 PM   #18
WBS is offline WBS  United States
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Altec 605a duplex crossover upgrade
"fried-egg" ? Does that mean it's facing up?
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Old 26th October 2017, 05:37 PM   #19
bentoronto is offline bentoronto  Canada
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Altec 605a duplex crossover upgrade
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"fried-egg" ? Does that mean it's facing up?
Not ordinarily. Few elements downstream of the amp that fulfil their appointed role as well as dome tweeters.

Before going electrostatic, while at Bells Labs, some audio buddies tested a couple and we bought a carton of the best* of the dome tweeters. I made a 3x3 (semi-cylinder) array using 9 units. Great tweeting power.

B.
*sorry, it was long ago; they were marked Magnavox if I recall
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Last edited by bentoronto; 26th October 2017 at 05:41 PM.
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Old 26th October 2017, 06:38 PM   #20
mrmky is offline mrmky  United States
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Would going active be that noticeable? I’ve done a bit of reading and it seems to be that the most profound gains are made with three ways. With the woofer on the 605 going from ~30-1500hz I’m wondering how much of a difference it would make.
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