Time Aligned Crossover for a 604c

[donaldpatten]

Three things are important to get the timing right. One : flatten the woofer impedance from two octaves below to one octave above XO ( 400 - 3.2kHz ) . For my 605s this was 13.1 Ohms +/- 0.1 ; Use a Zobel (R+C) to get this flat . I found 16uF & 16 R right for my thee 605s.
It is important to find this impedance to properly terminate the Bessel low pass filter ( 5 caps & 5 coils ). If the impedance is off so will the delay and the frequency response .
Three: when designing the low pass filter you need this info along with the amount of time delay to be added. If you change the woofer impedance, Zobel , or magnet structure ( dimentions, acoustic centers, etc ) all the coils & caps must change. I should also caution you that the amplifier output impedance should be considered ( tube vs solid-state ) since it also changes the filter delay/response and parts.
The test signal on my web site allows one to check the timing with a scope and microphone .
Wouldn't it be nice if all the alnico magnet 604s & 605s had the same acoustic centers, and impedance.
www.donpatten.com
Don

[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.

Yeah, I remembered on the way home. I know better than to trust my memory anymore, but ............

Absolutely! I've cured quite a few bass shy systems by getting folks to just swap wires to the sub. What they don't realize is that when the sub is up front with the mains that it's much more out of phase in this position than not.

Anyway, back to the 604......... Adding a simple wave-guide extension to the small horn would allow it to be used at the 604B's 1.2 kHz and the M19 XO's basic design, though of course with different values for some of the components.

GM

[Altec Best]

Anyway, back to the 604......... Adding a simple wave-guide extension to the small horn would allow it to be used at the 604B's 1.2 kHz and the M19 XO's basic design, though of course with different values for some of the components.

GM

GM do you have a photo of a wave-guide extension such as this ? I may like to add one to my 604G's one day...

[donaldpatten]

The Mastering Lab low freq XO coils do not seem right. Check reply # 8.

The 2mH coil with a DCR of 1.37 would have to be #23 AWG
The 5.5 mH coil with a DCR of 1.27 would be # 20 AWG
No one in their right mind would use wire that small for a 4 Ohm speaker.

The Zobel with a 25 Ohm R would be for a speaker around 20 Ohms

Don

[Earl K]

The Mastering Lab low freq XO coils do not seem right. Check reply # 8.

The 2mH coil with a DCR of 1.37 would have to be #23 AWG
The 5.5 mH coil with a DCR of 1.27 would be # 20 AWG
No one in their right mind would use wire that small for a 4 Ohm speaker.

The Zobel with a 25 Ohm R would be for a speaker around 20 Ohms

Don

The ML network was used with a 604E hybrid ( though I'm pretty sure the woofer section wasn't 4 ohms nominal ) .

I'll agree that the arrangement seen above is pretty unconventional .

I'll tell you what I see ( fwiw ) .

- Very low Q coils ( high DCR ) with one of them ( the 5.5 mH ) bypassed with a resistor ( to give a 2 part slope for BSC reasons ) followed by a cap whose value is so chosen to simply rotate the phase a bit ( near & above the crossover point ) . All in all, it should be a pretty gentle, low-slope, low pass ( with some "business" to take care of the woofers rising response, starting way below the actual crossover point ) .

- That's what I ( think I ) see / not what a spice program has confirmed ( or shot full of holes, btw ) .

- FYI, there are some obvious flubs ( at least to my eyes ) within the other linked to original transcriptions of the Urei filters .



Here's a pic of the guts of one Mastering Labs network ( not mine / it was eBay fodder ). Looks like fairly thin wire !

[Alien_Shore]

interesting - they weren't too concerned with magnetic coupling of those inductors...

[GM]

GM do you have a photo of a wave-guide extension such as this ? I may like to add one to my 604G's one day...

No, it would have to be engineered and one needs a 604 in hand to work from, but the actual making of it would be simple enough, though it would look similar to the 3 series horn except probably a bit larger.

This was one of the many audio projects I had lined up for when I retired, but considering what all has happened in the ensuing ~18 yrs, probably never going to happen now. I just wished GPA hadn't stopped 'short' on the 3 series unless there's a big horn 4 series still under 'wraps'.

GM

[HeathKitPat]

For now so I can get the original dividing networks out of my speakers I've ordered the new GPA crossovers designed for 16 ohm duplex speakers. They should be in early next week. After I install them and break them in I'll give a report. The 604c's in 606 corner cabinets really sound good now, so I can't wait to see what kind of improvement the GPA's xovers give. I spoke to them today and they did address the 2-4k hump in the curve with a notch filter and although they told me they are not perfectly time aligned they are aligned such that they are a great improvement over stock.

[Altec Best]

No, it would have to be engineered and one needs a 604 in hand to work from, but the actual making of it would be simple enough, though it would look similar to the 3 series horn except probably a bit larger.

This was one of the many audio projects I had lined up for when I retired, but considering what all has happened in the ensuing ~18 yrs, probably never going to happen now. I just wished GPA hadn't stopped 'short' on the 3 series unless there's a big horn 4 series still under 'wraps'.

GM

OK Thanks GM !

[mah]

HeathKitPat, the crossovers do not require breaking-in. They are ready to go as soon as connected.