Crossover servicing

[MikeMusic]

Seeing Martin's post about crossovers made me think - yes honest !

Is is a good idea to have crossovers serviced ?
What sort of age and any other parameters ?

[Reffc]

If they're from the 1970, 1980's or even the 1990's and used electrolytics, then almost certainly by now, the electrolytics will have drifted miles out of tolerance as the legs oxidise and the seal between the leg and the cap is broken allowing the caps to dry out. Not always, as I've come across 30 year old electrolytics that were still within tolerance, but I have to say that they were the exception. This alters the crossover point and speaker response and can lead to instability in a crossover circuit depending on where the problem capacitors are. Some though will be fine even after 30 years, ones like polypropylenes and polysesters. However, many manufacturers weren't all that fussy about speaker matching (although some were) and tolerances on early caps and inductors etc may be far from ideal. Add to that the use of ferrite cored inductors (not ideal), high resistance inductors etc and advances made in capacitor design (low plate distortion versions of polyptrops for the signal path etc) and it's not hard to see that almost every mass produced crossover of a certain age can be improved upon. You don't need to go down the expensive "Foo" component path either to reap the benefits. It's more about having the right components in the right place to the right tolerances than about branding etc. Saying all that, you may find, depending on your speakers, that nothing needs doing. You can't generalise as it varies from one speaker to another depending on age and heritage.

[istari_knight]

Somtimes. :)

It entirely depends on the crossovers in question... Vintage speakers almost always benefit from having new electrolytics, replacing them with modern polyprops willy nilly can have undesirable effects but in the right hands the original balance can be preserved whilst improving upon what was already there. IME UK built speakers from the 80's quite often used "cooking grade" components [cored inductors & electrolytics & low quality films - If any] there is large room for improvement here...

[istari_knight]

I typed my reply & went for a cuppa before submitting :)

Paul's spot on.

[DSJR]

Mike, your 'Brik crossovers only used polyprop caps as I remember and with the amps you use, shouldn't have aged at all, apart from a layer of dust as they're in the stands. I still maintain that the only way to really hear isobariks is active, either with the naim box, or better, with the Linn Tune-Box and three amps able to drive a 3 to 4 ohm load safely. The amount that's being lost in your complex passive crossovers won't be believed until heard, and no amount of boutique bits will cure it I'm afraid!

Remember, it was in Linn's best interests to sell you the active upgrade and they pulled all the stops out to help you to do this. Unlike Naim, who used common electrolytics in their SBL crossovers, Linn did try with the later 'Briks to keep them fairly up to date, but the active option just takes them to a genuinely higher plane irrespective of the amp driving them IMO.

[MikeMusic]

Somtimes. :)

It entirely depends on the crossovers in question... Vintage speakers almost always benefit from having new electrolytics, replacing them with modern polyprops willy nilly can have undesirable effects but in the right hands the original balance can be preserved whilst improving upon what was already there. IME UK built speakers from the 80's quite often used "cooking grade" components [cored inductors & electrolytics & low quality films - If any] there is large room for improvement here...
Linn Isobarik crossovers from the late 80s

[MikeMusic]

If they're from the 1970, 1980's or even the 1990's and used electrolytics, then almost certainly by now, the electrolytics will have drifted miles out of tolerance as the legs oxidise and the seal between the leg and the cap is broken allowing the caps to dry out. Not always, as I've come across 30 year old electrolytics that were still within tolerance, but I have to say that they were the exception. This alters the crossover point and speaker response and can lead to instability in a crossover circuit depending on where the problem capacitors are. Some though will be fine even after 30 years, ones like polypropylenes and polysesters. However, many manufacturers weren't all that fussy about speaker matching (although some were) and tolerances on early caps and inductors etc may be far from ideal. Add to that the use of ferrite cored inductors (not ideal), high resistance inductors etc and advances made in capacitor design (low plate distortion versions of polyptrops for the signal path etc) and it's not hard to see that almost every mass produced crossover of a certain age can be improved upon. You don't need to go down the expensive "Foo" component path either to reap the benefits. It's more about having the right components in the right place to the right tolerances than about branding etc. Saying all that, you may find, depending on your speakers, that nothing needs doing. You can't generalise as it varies from one speaker to another depending on age and heritage.
Thanks Paul
For me these are super large components in my Isobarik crossovers.
Has DSJR's reply change the ball park ?

[MikeMusic]

Mike, your 'Brik crossovers only used polyprop caps as I remember and with the amps you use, shouldn't have aged at all, apart from a layer of dust as they're in the stands. I still maintain that the only way to really hear isobariks is active, either with the naim box, or better, with the Linn Tune-Box and three amps able to drive a 3 to 4 ohm load safely. The amount that's being lost in your complex passive crossovers won't be believed until heard, and no amount of boutique bits will cure it I'm afraid!

Remember, it was in Linn's best interests to sell you the active upgrade and they pulled all the stops out to help you to do this. Unlike Naim, who used common electrolytics in their SBL crossovers, Linn did try with the later 'Briks to keep them fairly up to date, but the active option just takes them to a genuinely higher plane irrespective of the amp driving them IMO.

They sound superb at the moment.
The temptation was always to go 6 pack
Now I have heard the Chord driving the Isos that could be 3 Chords, plus a SNAXO and PSU with loads of cabling.
That is a level of complexity and additional boxes I'm not keen on now though

[Reffc]

Thanks Paul
For me these are super large components in my Isobarik crossovers.
Has DSJR's reply change the ball park ?

Not really. It depends on what components are actually used and whether improvements (eg to inductors) can be made reasonably economically. Many inductors used of the age were ferrite cored so there may still be tweaks, but as David says, if they did use Polyprops, the only point of replacement would be to use higher tolerance and lower distortion versions now available using things like the Claritycap ESAs, MRs and Mundorf M-Cap Evi capacitors, which in come systems can deliver audibly better results. As David also mentions, the real upgrade for isobariks is unquestionably to go active, so if bigger gains are required, that's the best plan although it is more costly.

A simple X-over examination and replacement of less than optimal parts to see the X-overs serviceable and improved may not be that pricey but whether it'll make big audible gains is doubtful in the case of Isobariks.

[YNWaN]

These are your crossovers Mike:

http://www.mickandviv.com/pfm/PMSXO1CutLinks.jpg

The smooth yellow components in the upper half are basic polyprop capacitors - the rest of the yellow and black components are electrolytics capacitors. All the coils are ferrite cored (no air cored at all).

[Reffc]

There's a fair few electrolytics in there as well as 100% ferrite cored Inductors. I'd certainly recommend at the very least replacing the elctrolytics. You can use like for like (ie current production electrolytics to mainatain the same ESR) or polys with some equivalent resistance added. Those will more than likely be out of tolerance by now.

[Arkless Electronics]

Replacing inductors is generally a very bad idea! The resistive as well as inductive properties need to be taken account of or one is likely to end up with a pretty bizarre frequency response ;)

[Reffc]

Replacing inductors is generally a very bad idea! The resistive as well as inductive properties need to be taken account of or one is likely to end up with a pretty bizarre frequency response ;)


That's easily done Jez. You measure them and replace like for like with air cored equivalents in the high power sections such as for the bass section. It's a good idea providing as you say, the values are correct.

[YNWaN]

Jantzen do a very wide range of inductors and air cored with the same DCR as the ferrite cored can usually be found (though, obviously, they are quite a bit bigger :)).

[Reffc]

Jantzen do a very wide range of inductors and air cored with the same DCR as the ferrite cored can usually be found (though, obviously, they are quite a bit bigger :)).

Precisely. The main limitation is generally size and not values.

[Arkless Electronics]

That's easily done Jez. You measure them and replace like for like with air cored equivalents in the high power sections such as for the bass section. It's a good idea providing as you say, the values are correct.

I would disagree that it's easily done... It's possible yes but not always easy! If DCR is taken into consideration then obviously it can be a good idea to replace inductors with air cored ones but often it is not taken into consideration!

[istari_knight]

Jantzen do a very wide range of inductors and air cored with the same DCR as the ferrite cored can usually be found (though, obviously, they are quite a bit bigger :)).

:exactly: Very good they are too. I've only replaced ferrite cores with air cores once but I felt the improvements were significant.

Even my [cheap POS] LCR meter is very accurate for reading inductors, it always matches what the schematics say when reading unmarked inductors and only cost £20. Once you have one of these its plain sailing :)

[MikeMusic]

Not really. It depends on what components are actually used and whether improvements (eg to inductors) can be made reasonably economically. Many inductors used of the age were ferrite cored so there may still be tweaks, but as David says, if they did use Polyprops, the only point of replacement would be to use higher tolerance and lower distortion versions now available using things like the Claritycap ESAs, MRs and Mundorf M-Cap Evi capacitors, which in come systems can deliver audibly better results. As David also mentions, the real upgrade for isobariks is unquestionably to go active, so if bigger gains are required, that's the best plan although it is more costly.

A simple X-over examination and replacement of less than optimal parts to see the X-overs serviceable and improved may not be that pricey but whether it'll make big audible gains is doubtful in the case of Isobariks.

Thanks Paul

Does Mark's pic give clues ?

[MikeMusic]

Thanks for the pic Mark

[MikeMusic]

So the reply in general seems to be
"Yes, should be a good idea after x years" x being 10 plus ?

Specifically for me how much benefit in SQ ?

[Reffc]

Difficult to quantify Mike as it depends entirely on how far the electrolytics have drifted, but I'd be willing to bet a free check for you that they have! They could have gone far enough to affect the crossover points in which case the gains in SQ of replacing them could be large. Some of those inductors can be changed if you have sufficient space where the x-over board fits to accommodate some larger air-cored ones of the same DCR.

[YNWaN]

The X-over fits in the speaker stand Paul - there is no more area in plan, but there is plenty of height - should be able to fit the inductors on. I would hard wire it too.

[Reffc]

Ah....no problem for Mike then should he want to get them refreshed.

[YNWaN]

No, I don't see an issue. Could be pretty expensive though with all those caps and inductors!

[MikeMusic]

Thanks Paul and Mark