[BobM]

I've got 2 left over V-Cap .1uF's and 2 Russian .1 UF Teflons that I want to use on my speakers tweeter crossover. I have Apogee's, so this crossover schematic might look a little strange to some of you. My question is, where shold I put the teflon bypasses?

I figured, put the best cap (V-Cap) at the earliest part in the circuit (C5) and the Russian Teflon at the next closest point (C1). Anyone disagree with me, or have a bettter suggestion (short of buying more V-Caps)?

Thanks

[Speedskater]

The impedance of the Apogee's is so low that I don't think a 0.1 uF will do much at anything below radio frequencies.

[madisonears]

If C5 is electrolytic, bypassing with 1 or 2.2uF film cap might make a difference.  You could try the small caps as a bypass on C1 or C3 to see if that has an effect.  Otherwise, sell them to someone who could put them to better use.

[Vapor Audio]

That's a very strange layout, with 3 consecutive series caps.  And a 64mh inductor 

But C5, C1, and C3 are all in series so theoretically they would all have the same amount of impact  with bypassing.  If C5 is an electrolytic, changing it to a decent poly cap would probably have the largest possible impact.  Use something like a 68uf Solen and 2uf Clarity MR to get the full value. 

[BPT]

I agree with Ryan's suggestion. Keep the values the same. Try to make C3 a combination of say a 4 uf Clarity cap plus a 1 uf VCap Cu Teflon plus a .01 Cu Teflon.
If you just want to use your Russians, then bypass C3 with them.
Chris H.

[BobM]

Yes, I warned you this crossover might look a bit strange. I can't fully explain it either.

C5 is actually 7 x 10uF foil caps in parallel. This is where I am using 2 Sonicaps, 3 Auricaps, and 2 leftover Spragues. I have bypassed this with my .1uF V-Cap.

C1 is a 10uF Sprague. I have bypassed this with the .1uF Russian teflon.

C3 is a 5uF Sprague.

The initial result I heard last night was a definite increase in top end extension. Perhaps too much so, because it became a little hard (all these teflons have been used before and should be fully broken in, but I am not ruling out that more break-in could smooth this out a bit).

My next thought is to replace the (C3) 5uF Sprague with a 1uF Russian K40Y paper and oil + a 4uF Sonicap. I'm thinking this will give me some additional midrange warmth and bloom.

I might also remove the .1uF Russian teflon from C1 and replace it with a .1uF Sonicap Gen II, depending on how the K40Y changes the sound. Or perhaps just replace it completely with a 10uF Sonicap.

Thanks

[Davey]

Just for clarification.  L2 is mislabeled in the schematic.  More likely it's a 63.7 microhenry coil.

The Apogee crossovers were populated with good capacitors from the factory.....and very well built too.  Many larger value requirements were constructed with smaller value poly capacitors in shunt configurations.  And you won't find any electrolytic caps in their crossovers.

I have my doubts that shunting those large value capacitors with 0.1uF capacitors made an audible difference, but there's no arguing with subjective evaluation. 

Cheers,

Dave.

[BobM]

Yes Davey, the factory installed Sprague's were very good, for the time, but they are at least 25 years old now so I thought selective replacement would be of great benefit. And that is proving to be true, at least to my ears. I was hoping to avoid full cap replacement though by using a bypass cap in certain spots over the old Spragues. Not sure I fully understand how the low 3 ohm impedance may affect this though and make a .1uF bypass insufficient. I am hearing a definite improvement with the bypasses I have installed already.

PS - I very well may have misinterpreted the value of the coil from their schematic (my bad).

[Davey]

Bob,

A good technique I've always used when evaluating shunting (or bypassing) capacitors (of small value) is to attach one side of the extra capacitor and then play pink/white noise through the speaker while connecting/disconnecting the other side.  If it's yielding an audible difference you'll hear it immediately, and much more conclusively than listening with music.

Cheers,

Dave.

[BobM]

Great idea Davey. I will give that a shot.

[BobM]

Well I tried lifting the .1 Russian teflon bypass on C1 while playing pink noise. No discernable difference that I could detect with my ear right next to the tweeter ribbon. So I'm going to pull that off and replace the old Spragues in C1 and C3 as follows. In fact, here are the components of the reworked crossover in their entirety (once they arrive):

C5 (70uF) =
~ 1 x 20uF Sonicap
~ 2 x 10uF Sprague (original caps)
~ 3 x 10uF Auricaps
~ 1 x .1 uF V-Cap Teflon (bypass)

C1 (10uF) =
~ 1 x 1.0uF K40Y (Russian PIO)
~ 1 x 4.0uF Sonicap
~ 1 x 5.0uF Sprague (or maybe a Multicap I have lying around unused)

C3 (5uF) =
~ 1 x 1.0uF K40Y (Russian PIO)
~ 1 x 4.0 Sonicap

I'm hoping to get some additional bloom and midrange PIO warmth by using the Russian K40Y PIO's, but if they don't work out I have either 1.0 Sonicaps, Multicaps or Obbligato Coppers I could use instead.

All resistors are being replaced with Mills MRA12's. The inductors I am leaving alone (for now).