L 300 Crossover Rebuilding-What Caps Would You Use?

[Oldmics]

Gentlemen

I have a customer that frequents this site who has asked me to rebuild the crossovers for his L 300 speakers.

He is looking for better than stock preformance but using value engineering parts selection.

He has a brand new original pair of crossovers to compare against the soon to be rebuilt crossovers.

The original caps were mylar and he is leaning towards using polypropelyne caps.

I personally think this is the way to go for a slightly better than original sound quality at reasonable cost outlay.

What would you guys suggest?

And what would the sound quality differences be using the parts that each of you recommends,when compared to originals?

I know that everybody will have a unique perspective.I am just putting out some feelers at his request.

Best regards,Oldmics

[macaroonie]

http://audioheritage.org/vbulletin/s...42&postcount=3

[4313B]

What would you guys suggest?

Build him a charge-coupled pair. Having built the 4344/4345 and 4355 charge-coupled networks and having listened to the difference I have to agree with G.T. - "These days I don't even bother listening to anything that isn't charge-coupled."

These days I don't even bother building a network that isn't charge-coupled; And those old systems get a new lease on life.

[CauYem]

Build him a charge-coupled pair. Having built the 4344/4345 and 4355 charge-coupled networks and having listened to the difference I have to agree with G.T. - "These days I don't even bother listening to anything that isn't charge-coupled."

These days I don't even bother building a network that isn't charge-coupled; And those old systems get a new lease on life.

What is "charge-coupled"?
Where can I get more in for about "charge-coupled"?
Thanks!

[Earl K]

Where can I get more in for about "charge-coupled"?

Read the last post in this thread for an introduction to Charge Coupling™ .

[Earl K]

Hi Oldmics

,,,,,,snip,,,,,,,,he is leaning towards using polypropelyne caps.

I personally think this is the way to go for a slightly better than original sound quality at reasonable cost outlay.

What would you guys suggest?

,,,,,,snip ,,,,,,,,

I know that everybody will have a unique perspective.I am just putting out some feelers at his request.

- After 4 years of dc biasing caps / I still think this topology is the best thing I've encountered since sliced bread . So ( never having heard the L300 ) I would still recommend Charge Coupling™ as an excellent starting point, for any new crossover build.

- For the sake of expediency ( and cost ), I'd start with biased Solens on the woofer and horn circuits .
- For the low entry price of doing comparitive studies, I'd try both biased Solens in the UHF circuit as well as unbiased Clarity caps ( on the 077s ).
- Since I never know what people will like / I'd offer up the two choices and then let the client decide what "floats his boat".
- ( ie; Some people prefer more of an Aphex style top end / of exaggerated UHF harmonics / while others don't find this musically appealing )

And what would the sound quality differences be using the parts that each of you recommends,when compared to originals?

- A ton more clarity offering a much deeper "look-see" into the music. I find this quite engaging.

addendum ;
- ( IME ) this ( the benefits of dc biasing ) is primarily due to the dc potential ( when held within the cap ) inducing electrical damping into "resonance prone capacitors" & providing for an electro-mechanical type damping on JBLs' "Over-Amped" transducers . ie; ( from my POV, ) most of these JBL transducers ( used in the 434x systems ) were originally designed for SR work and as such have way too many false dynamics built into them ( a type of loudness effect that's effectively damped down by Charge-Coupling ™) . Reducing both types of sonic aberrations ( which I call "splash" ) helps me hear further into the musical experience .
- I primarily like to emphasize these 2 benefits to dc biasing ( since I actually hear the effects being implemented ) .

[timc]

One question about CC. Is there a special reason 9v is choosen? Would you get an even better sound if you biased the caps to, lets say, 24v?

-Tim

[Earl K]

One question about CC. Is there a special reason 9v is choosen? Would you get an even better sound if you biased the caps to, lets say, 24v?

Stick with voltages approved by JBL when using JBL transducers .

- JBL used 18 volts in the S9500 & M9500. The 475nd compression driver with the aquaplased titanium diaphragm seemed to have needed the extra damping provided by the larger voltage .

- I've never searched for ( & therefore, never found ) what dc voltage will overdamp a typical JBL compression driver .

- I've worked with ( & extensively listened to ) an Altec 288-8K for more than 3 years now , on a CCed Hipass circuit . I find that I can only use 3 volts of dc in cap pairs that are isolated from the driver by inline resistance ( such as an Lpad ) . Sometimes even 1.5 volts of DC in a pair of caps is too much ( damping ) when those caps are directly connected to the driver (ie; no inline resistance, as is the typical case of a HF bypass circuit ).

[Ian Mackenzie]

Oldmics,

There seems to be a number of members lately enquiring about wanting crossover upgrades for reasonable cost and even low cost.

There is no cheap / low cost upgrade by the time you add up your own time (incl (R & D) and all the parts incl new binding posts etc

If they are expecting you do to the R & D for a low cost upgrade that is worthwhile imho that is more difficult than a properly engineered outcome.

The CC network outcomes are well documents on the forums.

The less expensive options (non charge- coupled) with low cost budget capacitors are not worthwhile in that by the time you bypass these cheap parts with high quality bypass capacitors it will end up costing about the same as charge-coupling.

Some people pefer the more exotic and expensive capacitors. I dont think this model or your client belongs to that category.

Ian

[Robh3606]

I have CC Mylars with bypass caps and PP without and either sounds very good. I would just go with PP and CC them.

Rob

[timc]

Stick with voltages approved by JBL when using JBL transducers .

- JBL used 18 volts in the S9500 & M9500. The 475nd compression driver with the aquaplased titanium diaphragm seemed to have needed the extra damping provided by the larger voltage .

- I've never searched for ( & therefore, never found ) what dc voltage will overdamp a typical JBL compression driver .

- I've worked with ( & extensively listened to ) an Altec 288-8K for more than 3 years now , on a CCed Hipass circuit . I find that I can only use 3 volts of dc in cap pairs that are isolated from the driver by inline resistance ( such as an Lpad ) . Sometimes even 1.5 volts of DC in a pair of caps is too much ( damping ) when those caps are directly connected to the driver (ie; no inline resistance, as is the typical case of a HF bypass circuit ).

Very good answer Earl. So just to clarify, The amount of voltage supplied to the caps, will determine how much damping will be applied to the driver? If so I sense a lot of experimenting in the future


-Tim

[Earl K]

Very good answer Earl. So just to clarify, The amount of voltage supplied to the caps, will determine how much damping will be applied to the driver? If so I sense a lot of experimenting in the future

Note ; You're highjacking "oldmics" thread with questions that are very specific to application techniques for CCed circuits .

- Anyways, rather simplistically, "yes" . ( inline resistance plays a role )

- But as I said above, JBL has already done the R&D for their drivers, so I'm not sure why you want to bother with this ( assuming you're using JBL drivers ).

[timc]

Sorry for the hijacking

It was a general question from my side Earl, I was just curious what the biasing actually did. I have discussed it with a few speaker builders and they have said it is just a "marketing hype" Good to hear they are wrong.

Anyway. Back to oldmics question. I have done something similar with my L65 crossovers. I used stock values on the caps and changed them to Solen. The coils i didn't change since i did not have an easy way to measure them. The result was a much smoother sound than the original, with less hiss. It also seems there is less "noise" in quiet parts.

I have also good experiences with Auricap and Mundorf Supreme Silver/oil. They are expensive. Worth the cost?.......if you can afford them without going broke.


-Tim

[Thom]

Have there been blind A/B tests done with various high quality (not high quality against junk) capacitors. Is this really different than wires. Please, I'm not staking out a position here. I have no facts to do that on. It's an honest question. Also I saw that JBL, on it's top speaker I believe, used charge coupled for part and didn't for another part. Is there a belief that it is audible in one range and not in another?

[Earl K]

Hi Oldmics,

- There's an old thread from Regis that's worth a read ( for your client & yourself ) . Click Here !
- Regis bypassed his stock L300 crossovers with small value PolyPropylene & Polystyrene caps .
- This simple approach might represent all that your client needs to hear & experience, to feel the change has been worth the investment.