Renovation of Celestion 66 Studio Monitors

[The Barbarian]

Before and after shots of one of the re-capped x-overs I completed today.

Ive not really kept up with this thread but why do people fit Electrolytics to these Re-builds, i personally would never use them or is it cash constraint due to high part values that made you fit them? However that does not explain the small one across the top of the board!

[Reffc]

Ive not really kept up with this thread but why do people fit Electrolytics to these Re-builds, i personally would never use them or is it cash constraint due to high part values that made you fit them? However that does not explain the small one across the top of the board!

Because you cannot trade polys for electrolytics and expect the crossover point to remain the same. If they were voiced with electrolytics, then that's what you should use with a few exceptions. Also, some values manufacturer's used were fairly high in value and it could mean a lot of expense and more space usage than permissible by the current crossover housing in some speakers. Look closely at the photos and tell me where you can get a 72uF capacitor and what it would cost, then what the space usage would be with a grouped set of caps to make up that value, and also how would you deal with the difference in ESR between electrolytics and polys? The Alcap electrolytics available today can be supplied to tight tolerances and although they are not as stable or linear with temperature or frequency variation as Polys, they're pretty good. Add to that they cost very little and the question becomes "why not use them?"

[Qwin]

Thanks for the comments gents.

Andre - I've fitted electrolytics where they were fitted in the first place.

If you just fit Polyprops where Lytics used to be you can compleatly screw up the circuit as Polyprops behave in a very different fashion.

You have to add additional resistors in series for every Poly prop fitted to try and make up for their lower ESR value, but this is only a partial fix as the Lytics are non linear and are effected by temperature, load and frequency in a major way compared to the Polyprops.

Circuits designed using Lytics have been tailored for the way they work.

If you replace all the Lytics with Polyprops you may have to compleatly re think the circuit design to maintain x-over points, impedance behavior and relative loudness of the driver combinations. It gets VERY complicated and without measuring equipment and the knowledge to use it, you can spend months going round in circles wondering why they don't sound the same as they used too. The Polyprops may sound cleaner and more transparent, but the balance and quite often the magic will have gone.

The reason I used the Polyprops in the HF section is that these were a film cap originaly that behaved more like a modern Polyprop.

The more I dabble with x-overs, the more I realize that these differences have major repercusions.

EDIT: Oooops I see Paul answered in a similar way while I was typing. Thanks for that Paul, you first raised my attention to this and I am finding with experimentation and actual results that it is the case.

[The Barbarian]

Because you cannot trade polys for electrolytics and expect the crossover point to remain the same. If they were voiced with electrolytics, then that's what you should use with a few exceptions.

Is that so Well ive rebuilt loads of vintage X -Overs with just PP they have always been a vast improvement. One thing i don't do & thats take advice from forum posters because i don't need to. I use one brand of PP always have always will do, all other sound cack to me regardless of their boutique price tag..

Let me think now Martin T re-built his Gale '401' crossovers with just PP guess what he's happy, i use three different pair of speakers with full PP rebuilds guess wat im more than happy.. Just done my mates speakers too guess what he's over the moon.

[Reffc]

Is that so Well ive rebuilt loads of vintage X -Overs with just PP they have always been a vast improvement. One thing i don't do & thats take advice from forum posters because i don't need to. I use one brand of PP always have always will do, all other sound cack to me regardless of their boutique price tag..

Let me think now Martin T re-built his Gale '401' crossovers with just PP guess what he's happy, i use three different pair of speakers with full PP rebuilds guess wat im more than happy.. Just done my mates speakers too guess what he's over the moon.

Yes, that is so and just because you don't agree with it doesn't make it less so. You asked the question so why so aggressive when you're given the answer? Up to you if you ignore advice freely given and in an attempt to be helpful.

[Marco]

Here's a pic of my (totally stock) 66s, in situ in our downstairs lounge, where about 75% of my listening is done these days:







Marco.

[Marco]

Yes, that is so and just because you don't agree with it doesn't make it less so. You asked the question so why so aggressive when you're given the answer? Up to you if you ignore advice freely given and in an attempt to be helpful.

Indeed.

Andre, your response to Paul, dude, was unnecessarily confrontational. He was only offering his relevant experience, in order to try and help, which although contrary to yours in this instance, was equally as valid

Marco.

[Qwin]

Nice Walnut finish on the 66's Marco, suits the room.

Isolation platforms? Look different to the ones in the Scalford Pictures.

I need to knock some platforms up for NEBO4, I have the moulds 50% complete and will be casting them in concrete.

The design is 75mm thick and the same shape as the speaker, with the small flats on the two front edges. They have carpet spikes in each corner on the underside which are adjustable through holes in the top face and a leveling bubble mounted in the centre of the top face.

My speakers have 3 of those Soundcare spike/shoe assemblies fitted and these will sit on the Plinth.

Pictures of the plinth build will follow.

[Marco]

Hi Ken,

Cheers. They're pretty minty, although could do with a little attention here and there, in order to really bring them up like new!

The Mana 'platforms' are indeed different than those we used at Scalford. The ones pictured above are what's known as 'Mini Soundbases', designed to be used under tall floor-standing speakers, and suit the 66s perfectly.

At Scalford (as I didn't have the Mini Soundbases then) we used ones which are normally used under Krell power amps, so they were totally oversized, but fulfilled a purpose!

The 66s undoubtedly sound much better on top of some type of properly designed stands/plinths, rather than simply plonked on the floor, as they would've been originally used, and probably why some folk complained of 'boomy bass'. That just doesn't happen when they're properly supported and driven by an amplifier with suitable 'grip' and slam!

Look forward to seeing your plinth build in due course.

Marco.

[Macca]

It's a question you could ask about a lot of vintage speakers. Celestion did not just ship them out without listening. These are from well before the day of boxcalc and so forth. So what did the engineers do for stands when testing?
Probably just the castor feet. And bell-wire speaker cable.