Pass Labs B4 crossover questions

[woofertester]

There is a 3 way in the works for the store. What slopes did you want?

The ribbon tweeter high pass may need 24dB/octave at 3kHz. It will flap in the breeze with a gentle slope.

The woof /mid crossover at 100 Hz can be 12 dB.

The midrange may need some low pass to match the roll off of the ribbon tweeter. I will have to see if I can dig out some ancient measurements.

I will perform some due diligence to let you know for sure.

 

[feds27]

Fortunately the parts are symmetrical, and work the same either way.

That’s a relief. Thanks for responding.

 

[Nelson Pass]

I have resisted the temptation to deliberately do these backwards.....

 

[Zen Mod]

not first and not last time

at least 50% deliberately

 

[woofertester]

I have resisted the temptation to deliberately do these backwards.....

This raises a question. For those people who cannot obtain matched pairs of K170/J74, is there a way to make a quasi complementary buffer from a pair of K170/K170 or a pair of J74/J74?

It seems you can find quantities of one or the other but no batches that produce matched pairs.

 

[Zen Mod]

K/K easy

 

[tyman63]

Is this possible with a B4 or B5?
30-260Hz
30-580Hz
580Hz to 20K

 

[woofertester]

K/K easy

Is there a thread or an example somewhere?

 

[Nelson Pass]

It's pretty simple. Use two matched 2SK170's LSK170's or 2SK370's,
set the negative side as a CCS by tying the Gate and Source together,
and you are done. If they are not matched, you will see some DC
offset, but you can block that with a capacitor, or degenerate the higher
Idss part with a little resistance.

You can do this with the P ch parts as well, but since they are more
expensive and harder to get, there is little reason.

 

[Nelson Pass]

Is this possible with a B4 or B5?
30-260Hz
30-580Hz
580Hz to 20K

The design is not the limitation.

If it is an actual B4, it has been set up with the values to cover 25 to 6375
Hz in 25 Hz steps. B5 is more limited, at 20 to 300 Hz.

 

[Soundhappy]

The design is not the limitation.

If it is an actual B4, it has been set up with the values to cover 25 to 6375
Hz in 25 Hz steps. B5 is more limited, at 20 to 300 Hz.

Sound like serious upgrade to multi-way audio system !
Best regards

 

[tommydoan84]

Mr Pass
I remember you mentioned somewhere in some other post, we can change the capacitor values to extend the Xover frequency range of B5 somewhere to 500 Hz or 600 hz, right ?

Btw, i'm also patiently waiting for the B4 and B5 kits to come out in the store. I'm currently playing with my OB using miniDSP 2x4 HD and get some decent good sounding. Can't wait to see how much it will improve with B4 or B5

Thanks,
Tom

B5 is more limited, at 20 to 300 Hz.

 

[woofertester]

It's pretty simple. Use two matched 2SK170's LSK170's or 2SK370's,
set the negative side as a CCS by tying the Gate and Source together,
and you are done. If they are not matched, you will see some DC
offset, but you can block that with a capacitor, or degenerate the higher
Idss part with a little resistance.

You can do this with the P ch parts as well, but since they are more
expensive and harder to get, there is little reason.

Thank you, I will give that a try. I bought some of each K170 and J74 and they do not match as complements. This will make them useful.

 

[Nelson Pass]

Btw, i'm also patiently waiting for the B4 and B5 kits to come out in the store.

The planned kits will be easy to adjust by choice of capacitors, and then by
trim pots over 1.5 octaves.

 

[chrisb]

Maybe I’m just in a particularly puckish place presently, but considering what papa based designs offered through the aegis of the DIY Audio genies ( they know who they are) end up costing us, I think it’s time again to say - thanks, to all parties.

I might know a guy for whom a B4 kit would be a godsend -it’d certainly eliminate the amp compatibility issue with PLLXOs

 

[tommydoan84]

Thank you Mr. Pass!

The planned kits will be easy to adjust by choice of capacitors, and then by
trim pots over 1.5 octaves.

 

[Joca]

im waiting for this antecipated christmas gift. I have a OB project on the shelf with the eminence beta15 and MarkAudio alpair 10. In the past i searched for an insight about the amp choices and XO. I have the sony vfet 2 in monos and a F5. What configuration would you guys do. F5 on the bottom or another amp? (i have 1530/201 toshibas laying around waiting to put them on a good amp). and what crossover? B4 or B5?

thanks

 

[tyman63]

The design is not the limitation.

If it is an actual B4, it has been set up with the values to cover 25 to 6375
Hz in 25 Hz steps. B5 is more limited, at 20 to 300 Hz.

I am actually thinking of triamping the OB
W1 - 25-253Hz
W2- 25-600hz
CD- 600Hz to 20Khz or use a simple passive crossover

Or maybe a B5 that has a Low freq eq and change the caps to achieve 600hz

 

[Nelson Pass]

I am actually thinking of triamping the OB
W1 - 25-253Hz
W2- 25-600hz
CD- 600Hz to 20Khz or use a simple passive crossover

The LXmini+2 or Studio version will do that. I have a couple prototypes
already, and the store is prepping a chassis with 8 RCA's.

 

[Nelson Pass]

im waiting for this anticipated christmas gift.

I think Christmas will be coming early this year.