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SBL cross-over

If you want to experiment a little bit more you really should try swapping the Solen capacitor in the tweeter network with one of the many selections of 'boutique caps' out there. Certainly in my DBL crossovers, putting a high grade capacitor in the tweeter network gave a much sweeter, more lucid and detailed sound. I used Cardas, although they are no longer available. But something like V-cap, Clarity or Duelund should work a peach. You also would be more than a little surprised to hear the effect of a high quality resistor again in the tweeter network. A Mills wirewound is very good and quite inexpensive, although a Duelund CAST graphite resistor at x25 the cost is even better.
 
The plan was to export these Down -under, and get another pair made with Clarity caps and bi-amp capability, but I'm getting a SNAXO on Thursday.

Its put the cross-overs on hold a little, although Andy's keen on them for his Katans .

I've noted on this forum a new set from Naim has reaped small reward, with the upgraded components its night and day difference. I can't imagine active getting better, but it would've always been a thorn in my side if I hadn't tried when opportunity arose.
 
After spending some time optimizing my passive crossovers, they ended up superior in every way to the Snaxo/Supercap with four additional channels of active amplification. Once you have found the right design for your passive crossovers, it is then time to start looking towards component upgrades.

Using a toroid inductor in the bass network lowers its DCR maybe 50x and greatly increases damping factor giving a much tighter and tuneful bass. Some speakers however are actually designed around the added DCR of the air cored inductors in the bass network (however DCR changes seem to be more important in the mid or tweeter networks), so caveat emptor. Or ask James!
 
The DCR of an inductor is a function of the wire diameter and the length of the wire.

The DCRs of the air-core inductors that I recommended for the SBL crossover have approx the same DCR as the ferrite inductors that they replaced. They are only a fraction of an ohm so getting much lower requires much bigger inductors.
 
This is the problem with passing the soldering iron to a friend, I don't understand this stuff, just listen :D

I do know that these cross-overs are much better than original, and the nature of 2nd hand Naim I won't loose trying the SNAXO. I already had a SNAPS and 110's hanging round.


I tried my standard ES 14's yesterday (pre sale check over) I was quite shocked they were loose and flabby by comparison.
Our aural expectation changes quickly, probably a good thing, we'd never venture into Scalford if it stuck !
 
The aircore inductors in the SBL have DCR circa 0.4 ohms. The equivalent values in the Jantzen inductors are 0.06 ohms, so they are about 80% lower. If you tack on this DCR to the output impedance of your power amp, you will see why the damping factor becomes so much lower using these toroids in particularly the LF network.

The ferrite core inductors in my standard DBL crossovers saturated with only 5W of power and developed nasty resonances, whereas these toroids are rated around 500 to 700W continuous power.

Because of the much higher permeability of the mumetal cores, these require far fewer turns to achieve the same inductance as air cored equivalents, so have much lower DCR and probably too parasitic capacitance.

The other thing about air cored inductors...they are essentially a hollow tube and the Biot-Savart pulsations that occur with current surges can be literally heard as they hum along to the music. This is intrinsically 'lossy'. The toroid inductors are much better damped.

The coup de grace I had done on the DBL passive crossovers when they were taken as far as they could get was the shroud them in a very dense acoustically inert material (in the same way that transformers are sometimes potted in epoxy) that completely eliminated any tendency for mechanical resonances. The obvious disadvantage is the components are not entombed and are therefore virtually impossible to change. But by using components with near indefinite lifespans (no electrolytic caps for instance) some immortality was bestowed.

A couple snaps of the toroid inductors follow.

http://www.mediafire.com/view/1wrkm11m5egns3c/toroid_inductor.JPG

http://www.mediafire.com/view/6dypn353z3byztt/toroid_2.JPG
 
If you substitute an inductor for one with a significantly different DCR you will be altering the frequency response. If you make the wire thick enough you can achieve low DCR readings for air core inductors.
 
Info on Jantzen toroidal core coils here:

http://www.jantzen-audio.com/c-coil/

Jantzen say that they are designed for bass and sub-woofer, so not sure that they are really of use for the SBL crossover that operates at around 2.7kHz. Also no suitable values.

Foils coils look to be a better enhancement over conventional wire coils.
 
Jantzen do an extremely comprehensive range of inductors, both in terms of construction type and values - I use them in my own crossovers.

Ferrite cored inductors are often used for lower frequencies as they are more efficient. An air cored inductor of the same value and the same DCR rating will be very much larger. Foil inductors have greater surface area and are therefore a little smaller.
 
chord said:
I am not sure that air cored inductor is better anyway here.
Click to expand...

I am, I've got a bit of a dilemma, I've gone active with a SNAXO2-4 using DIY NCC on the bass, and mono 110's treble. (i only needed the snaxo, it was an obvious route to try)

The DIY PXO are so close to active its really difficult to justify the extra box's. Active makes sense when I crank the volume, but living in a flat, thats an exception rather than the norm.

The value of the SNAXO could be spent upgrading my NCC and more exotic caps, the PXO could also be made bi-amp capable, I'm attached to my DIY 110's:cool:

The SNAXO has introduced some Naimness, there's a mid bass hump and some PRATs been introduced (?), trouble is I'm an Avondale fan IMO a more natural presentation that doesn't tire after hours listening.

Nice choice to have though, either option is a major step from the original PXO:D

Mark
 
No, I'm still fairly new to SBL's, been a roller coaster ride already.

I've got a valve dac at home for audition, but I still prefer solid state for now.

I can see (at least trying) valves in the future, but it'll cost.
I regularly hear an EAR 834, but prefer my Arkless, same deal with the dac. The Prometheus sounds great, but there's something just not quite right (for me)

*fyi I have an Avondale 102, its quite a step away from a Naim pre
 
Oh what a journey, the last few weeks I've been Active with a SNAXO2-4, with the benefit of using amps I already had. DIY NCC on the bass, mono 110's on treble.

A small increase in quality, it was only really noticeable past 12 O clock, along with more PRAt I associated with the SNAXO?

Anyway, this arrived this morning;

DSC_3598 by levs the diver, on Flickr
Audio 42 V2, bowie for scale, its not a cd !
Forever impatient, the wiring's a mess, should I try and orientate the coils differently?

Initial impressions are favourable (the modded PXO was already very close to Active), I think the 'new' Audio 42 is genuinely NOS so can only get better. Its also independent high and low, so I can try bi-amping

I for-see a SNAXO for sale...........?
 
Are those the ones that sold on eBay for £162 (+£18.50 P&P)? If so, you got a good deal - the parts would have cost more than that (quite a bit more!).
 
I would suggest that the parts in this PXO would comfortably exceed the parts cost in a Snaxo by a comfortable margin. I also found out that a very well designed crossover with premium parts was quite superior to Snaxo/Supercap etc with multiple amps.

YNWOAN said:
Are those the ones that sold on eBay for £162 (+£18.50 P&P)? If so, you got a good deal - the parts would have cost more than that (quite a bit more!).
Click to expand...
 
The parts added up to over £400, and yes a few bargains still on ebay.

I'd already come to the conclusion that there was very little between my DIY (Steve's) PXO and active, another build with more expensive parts (and bi-amp) was on the drawing board when these came along.

I don't think they've been used, so will hold off any comments, but haven't noted any loss of quality, just more spaghetti again ;-)
 
Hi Mark,

Looks as though the audio 42 crossover may have used some different component values. Can't read many of them from the photo. Any chance that you can list the values of the components used?

John.
 
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