Altec 604-8G, stock crossover vs Markwart, anybody can share experiences?

[Franknfurter]

Hey mates,
..would like to get some input from users who built it.
Here the Markwart design:



Stock version:


Greetings from Hamburg..
Frank

 

[dblDeckWreck]

I had a pair of 604-E that had original crossovers with them. I built Markwarts for them, and they sounded fine. I personally liked when I used active crossovers, more control and could tailor per whim.

 

[kyle]

I had 604-8Gs in 620 cabinets. the Markwart crossovers sounded better defined and more open than the stock crossovers. The components were better quality which may account for some of the difference but in my eyes (or ears) Jeff's provided better balance and a smoother crossover area.
I had 604Es that benefited from Jeff's crossover design in the same manner.
I also bought Jeff Markwart's 604-16Xs that he talks about in some of his posts from him and made his crossover for them. They were quite good - almost the same as the 604-8Gs but not quite as smooth sounding. I did not make a special cabinet for them, just used the 620 cab from the 8Gs. I did no comparison between the crossovers because of the difference in impedance.

For my listening perspective, I have Model 19s now and I much prefer them. This is at odds with most people but I had 604-8Gs and the 19s at the same time and at 3 different houses and in 4 different rooms. I just prefer the sound of the 19s, most on the various boards think the 604 is better. In light of that, my opinion should be taken with a grain of salt.

 

[Franknfurter]

May I ask which crossover exactly of the Marwarts you used in the 620s? Guess in my Stonehenge it might be different anyway, just interested.
And absolutely no probs with salt, yw

 

[kyle]

For the 604-8Gs, I used Jeff Markwart's 604-8H crossover. The 604E are 16 ohm speakers and I adjusted cap and coil values to suit. The distance between voice coils is the similar or the same so the crossover spread that Jeff used still works.
I used the attached version of Jeff's schematic.
Edit: The box you have them in won't change the crossover points so the 620 or Stonehenge should be the same.

 

[Franknfurter]

Now I am puzzled, cuz Jeff himself suggests that layout I posted above for the "G". Yours is 18 dB in lowpass too ...

 

[kyle]

I sold my last pair of 604s about 8 years ago but I'm pretty sure that that is the crossover I used. I looked at my pile of stuff in my work shop and could only find the cannibalized remains of the last crossovers I made. The remaining parts look right for the schematic I posted.

 

[Franknfurter]

Thanks for looking after your old xovers @kyle. Too bad I don't have a shed with cannibalized markwarts. And yeah, it's that 18 dB lowpass design. I decided to go for that 12 dB markwart xover from the opening posting ....meanwhile I spent a week testing, looks very promising, hopefully will be done next weekend.

Btw, I stripped the original "Altec 604G crossover" to measure the parts. Interesting, all Cs were 8-10% about their values (guess they have been too 47 years ago, still within that 10% tolerance).
But: The original coils do not have the values they should have (if the only schematic I was able to find, see in first posting, is correct) :
L1 1.8 mH measures as 1.5 mH
L2 0.6 mH has 0.5 mH
Double checked this at my part dealers LCR bridge.
So my question: Did Altec maybe change the values or is it possible that those nice little core coils have lost some inductance in 5 decades?

Frank

 

[Franknfurter]

Hey there .... ended up with the Markwart design from above. Maybe years later somebody is interested so here you go, many hours of testing showed:
- as mentioned, the only available 604G crossover layout seems wrong (Coil values)
- after measuring original xovers I started with replacing the Cs with modern MKPs (exactly the + 8-10% values I measured): Clearly much better than orig caps.
- then replaced serial orig coil (LF) with a awg16 foil coil (same inductance, RDC estimated same, too low to measure with my gear): Wow. Much better bass, tighter, "faster". Vocals also better.
- replacing HP orig coil with foil coil: No difference for me (and another tester).
- listened a week to that setup to get used to it, then built the Markwarts (with borrowed L pad from orig xovers): Wtf, Jeff! Or: Wtf, Altec? 604s didn't loose their "sound", but the shout traded in for the missed brilliance. Great work Mr Markwart!
-finally found a good value for the Lpad, so replaced it. I can recommend to replace the Lpad (was used in Jeffs design only as variable R, connectors 2 and 3) and the following 2 Ohm resistor with just 1 15 Ohm R. Also played with the serial R (3 Ohm in Jeffs design), ended up with 3.9 Ohm.

Cheers!

Frank

 

[dasacco]

Hi!

I built the Jeff Markwart crossovers for my 606-8G's last year and I'm thrilled with how they sound as compared to the original crossovers that came with the speakers when I bought them in 1978. Much smoother and less fatiguing.

I'm curious, when replacing the serial R with 3.9ohm instead of 3ohm, how does that impact the sound? What would I listen for?

Thanks!!
Dave

 

[pete1729]

I had a pair of 604-E that had original crossovers with them. I built Markwarts for them, and they sounded fine. I personally liked when I used active crossovers, more control and could tailor per whim.

Hey now, do you have a record of which values you changed and in which position?

 

[pete1729]

For the 604-8Gs, I used Jeff Markwart's 604-8H crossover. The 604E are 16 ohm speakers and I adjusted cap and coil values to suit. The distance between voice coils is the similar or the same so the crossover spread that Jeff used still works.
I used the attached version of Jeff's schematic.
Edit: The box you have them in won't change the crossover points so the 620 or Stonehenge should be the same.

Is the attached schematic showing the values you used for your 604e crossover?