Time Aligned Crossover for a 604c

[HeathKitPat]

Has anyone here done any experimentation with making a time aligned crossover for the Altec 604c? As I understand it the stock crossovers leave a lot to be desired and to really get the 604c to sign time aligning the two drivers for a real source point sound is important. Would love to see plans or a schematic for a crossover with adjustable features.

Pat

[cradeldorf]

Jeff Markwart did one but it was a B with an E cone. That's the only one I've ever seen. Don and Mike have been playing with them too, But they're for "E's"
Jeff Markwart's Corner - Phase Corrected Crossovers
MY personal thoughts are that I can't believe there is a difference when you figure how much difference there is between the phram and the cone (Appox. 4 inches) divided by the speed of sound. The offset of the sound is probably in the Micro milliseconds area. But feel free to chase the Leprechaun. Not sure where you got your information about the original networks but my mock N1600 is blowing away every other thing I've ever concocted.

[GM]

It's not anywhere near that simple, even though Altec's published alignment routine for its two way speakers implies otherwise because one can physically move the HF driver as required.

WRT the 1500-1600 Hz XO points, this is close to our 2 kHz peak hearing acuity, so most folks should be able to hear a difference in an A-B test, though whether or not one notices a more correct 3D image will be up to the individual.

Obviously, the recoding is the big variable. A ?dry? studio recording only has whatever ambiance the mixing engineer adds, so best to use either a proper test signal or live small venue one. On the ?best? performing system I?ve built/owned, Ramsey Lewis?s original THE IN CROWD and Yusef Lateef?s LIVE AT PEP?S stereo LPs came so close to replicating what I had experienced at Hotlanta?s THE CARROUSEL that about all that was missing was the strong, cloudy, ?aroma? prevalent in a post 1964 jazz nightclub.

Anyway, the human tolerance range of time/phase detection is fairly wide for men, but not so much for females, same as it is for some other aspects of hearing acuity, so where there's a female in the listening 'mix', best to cater to her generally superior hearing acuity if you need any audio related approvals.

GM

[HeathKitPat]

Jeff Markwart did one but it was a B with an E cone. That's the only one I've ever seen. Don and Mike have been playing with them too, But they're for "E's"
Jeff Markwart's Corner - Phase Corrected Crossovers
MY personal thoughts are that I can't believe there is a difference when you figure how much difference there is between the phram and the cone (Appox. 4 inches) divided by the speed of sound. The offset of the sound is probably in the Micro milliseconds area. But feel free to chase the Leprechaun. Not sure where you got your information about the original networks but my mock N1600 is blowing away every other thing I've ever concocted.

Isn't it more about what the two sound waves do to EACH OTHER.. and as it stands all comparisons are relative. My new (to me) 606 corner cabinet with a 604c and a 515 cone blows away my hotrodded Valencia's. But by tomorrow night when I install my pair of correct original cone 604c's I'm sure they will blow the socks off that 515 coned one. So cradeldorf to say your mocked up N1600 is blowing away everything else to date is believable, but that doesn't mean you've reached the end.

Also I chatted with Jeff after visiting his site. He pretty much seems to agree that the C is a different animal altogether. I tend to agree that each 604 has it's little nuances. I'm working on the C's with original cones as I believe the 606 cabinet was tuned from the factory for the C and B model 604's



BTW I've had the pleasure of seeing the Wee folk once or twice.. ('twas in the wee hours of the morning after a few too many pints.)

[HeathKitPat]

but not so much for females, same as it is for some other aspects of hearing acuity, so where there's a female in the listening 'mix', best to cater to her generally superior hearing acuity if you need any audio related approvals.

GM

My wife will testify in court regarding my inferior hearing. She swears I can't hear a thing she says.

GM and Cradeldorf, I am looking for information or guidelines to an actual crossover someone has made or used other than the factory designed. I'd like to get closer to a Mastering Labs type, but information on the web seems to be scarce.
Thanks,
Pat

[Alien_Shore]

Well, just like Cradledorf said, if you haven't already, you should start with Don's site. There really is a wealth of info for DIY 604 crossover construction. Hell, he even shows you how to wind your own inductors!!

[cradeldorf]

So cradeldorf to say your mocked up N1600 is blowing away everything else to date is believable, but that doesn't mean you've reached the end.

Also I chatted with Jeff after visiting his site. He pretty much seems to agree that the C is a different animal altogether. I tend to agree that each 604 has it's little nuances. I'm working on the C's with original cones as I believe the 606 cabinet was tuned from the factory for the C and B model 604's



BTW I've had the pleasure of seeing the Wee folk once or twice.. ('twas in the wee hours of the morning after a few too many pints.)

I will agree with you there Pat. Personally I think they're a bit light on the midrange bass (almost non existent), But the sound stage is crazy better than any parallel crossover I have tried. They almost disappear all together. I'll also agree with Jeff that they are a different animal. The worst part is no matter what you do they sound phenomenal so it's pretty hard to judge when their at their best.

I wish you well on your endless journey. It's been enlightening to me.

[Earl K]

Well, just like Cradledorf said, if you haven't already, you should start with Don's site. There really is a wealth of info for DIY 604 crossover construction. Hell, he even shows you how to wind your own inductors!!

In addition to Don's excellent efforts in these matters I suggest that you study the schematics for the Urei TA 838 network . It's enlightening to compare what he is up to, to the design topologies embraced by Urei back then . ( Hopefully you'll notice that the group delay for the woofer section is attained in a similar "brute-force" manner to Don's approach ). Be aware that these design choices result in overall reduced sensitivities that push sensitivities into the very low 90's . ( Urei ^Ta 839 network ,,, Urei ^Ta 840 network )

The 838 ( & the later versions ) is a network designed for 8 ohm drivers ( 604-8G for the 838 ) but I think most of the values could be transposed backwards to your 12-16ohm 604C drivers ( assuming yours are still, all original ) . I would want to compare impedance curves ( for the 604C to the 604G ) to try to get an idea about the feasibility of a straight transposition .

Since it's a parallel style network I suggest that you redraw the schematic into two parts ( HF & LF ) .

Once in two parts transpose all the LC values to work for 12 ohms & then again for 16 ohms. At this point I suggest pricing out the parts from Parts Express

If you want to maintain the 604's natural high sensitivity then I suggest biamping ( using an electronic crossover with woofer delay capability on the woofer ) / but a passive network for the HF driven by it's own amp . That passive can be either Dons HF network or the HF portion of the 838 ( they are all nominally 6db High Pass filters coupled to 36db LowPass filters with a notch filter thrown in , here & there ).

Really, none of this is for the casual user who wants a turnkey solution handed to them simply to implement .

You'll need some test gear ( such as REW ( Windows version )software with a UMIK-1 mic ) to test out your results .

[GM]

Hmm, IIRC the 604C has the large horn, so going from dim memory of reverse engineering it, it is physically large enough to support a 1000-1200 Hz XO, so seems like adapting the M19 XO would be the thing to do.

GM

[cradeldorf]

Hmm, IIRC the 604C has the large horn, so going from dim memory of reverse engineering it, it is physically large enough to support a 1000-1200 Hz XO, so seems like adapting the M19 XO would be the thing to do.

GM

The B's were the last with the big horn Greg, C's have the same horns as the E.

Also would like to add that I had my subwoofer all F'ed up and figured it out yesterday. There is no lack of bass now in my system. It's amazing what the phase switch in the right position will do.