Scan-Speak D2008/851200 to D2008/852100 exchange for Spendor SP2 mk1

[Xanthe]

Reasons for the swap: the existing D2008/851200 are 35 years old and are a ferro fluid variant. Although there’s no increase in distortion indicating a big deterioration or a loss of fluidity in the ferro fluid, they are probably no longer performing at their best. On the other hand, the bass/mids of the mk1 SP2 are known to have very good longevity so it’s probably worth doing a replacement.

The question was to replace the original 851200 variant with the same or use the newer 852100 variant…
My understanding of the design optimisations for the original 851100 variant and the ferro fluid 851200 variant is that the 100 was more optimised for dynamics and the 200 for a smooth response with better control of sibilance; so my assumption was that the newer 852100 would be more like the 851100.

The crossover in the SP2s is very simple 2nd/3rd order circuit, so provided the impedance curve, electro acoustic parameters and acoustic interface are similar there should be no fundamental problem and the driver and crossover integration should be OK. Checking the data sheets suggest that the D2008/852100 variant shouldn’t present any real problems from these perspectives (although the cabinet changes would need some thought).

Thinking about what we wanted, and the different characteristics of the 851200 and 851100, we realised that we would now prefer the slightly brighter, slightly more dynamic presentation of the 851100, so we decided to try the new 852100 units.

Looking at things, we could make the cabinet changes such that either the newer tweeters or the older units could be used.
To do the cabinet modifications we designed and 3d printed a marking jig to cut the ‘ear’ slots for the new contact position on the sides, and a jig holding a pair of ball races to accurately guide the drill bit to position M4 threaded inserts in the cabinet. The same jig used to mark out the ear slots also held the M4 inserts in place while the glue set. These worked really well and the cabinet modification turned out to be a lot easier than expected!

So the result…

Well the dynamic gains and slightly brighter presentation are there immediately, but at the same time it gives less sibilance artefacts and more HF consistency than even the 851200 whilst maintaining the fundamental audio characteristics of the D2008 tweeters. Unexpectedly it also seems to give significantly higher resolution: after only 10 hours we are already hearing delicate treble details that we’ve never heard before.

So if you need to replace your tweeters and you’re no longer able to get the old D2008/851100, the new version does seem to not only be a suitable replacement, but also even a bit of an improvement over the original models To our ears, it appears to give the best characteristics of each unit rolled into one, and with some other gains added in.

If anyone need the designs for the jigs for the cabinet changes, we can certainly provide them.

Note that we can’t give any comment about the 851300 as to the best of our knowledge, we’ve never heard a speaker using them.

[trickydickie]

Interesting post, thanks Xanthe.

I’ve been going through a similar dilemma having tried my old rather unique JC-1 speakers recently to see how good they sounded with my current system.

There’s a separate thread on this (https://community.naimaudio.com/t/poorly-speakers-no-hf/29455/1) but to cut a long story short both tweeters failed within a very short time of playing having not been used for 15 years or so.

With the 851100 being unavailable now in the UK I spoke to a speaker specialist and they advised that the 852100 was an ideal replacement and very little surgery was required. It was also encouraging to learn that this is a new model which should be available for the foreseeable future. The old model was around for 35 years.

I’m pleased to learn that your cabinet modification went well. The specialist mooted the same that it would be quite straightforward with just a notch being required due to the terminals being down the side. My speakers don’t use threaded inserts so that should make things easier if I go down this path.

I had decided to park the project as I don’t really have a use for them at the moment but a pair of used D2008/851100’s have come to light so I have obtained them and will refurbish as is for the time being. I’m going to replace all the capacitors in the crossover as these seem to be a likely cause of the failure due to them being 35 years old! The tweeters have arrived and I await the capacitors which have been ordered.

Did you consider the Hiquphon OW2-92 tweeter? This is being sold as a significant upgrade and looks like a drop in replacement. They are quite pricey though so I may hold that thought for if and when I bring my speakers back to mainstream use. I do know that a Hiquphon tweeter was used in my design of the speaker, a friend has Hiqupons in his; I was a friend of the designer and had prototype pairs hence the variations.

[Xanthe]

Yes we did consider the Hiquphon OW2-92 tweeter, but thought:

1 It’s less suitable with the 2.9 - 3 kHz crossover of the SP2 due to the higher and more peaky 900Hz resonance

2 It’d have to be a really big improvement to justify the price (~£275 for the pair)

3 I’d be concerned about getting a substantial difference in the sonic presentation from the speakers as the OW2 is specifically designed to replace the Linn tweeter variant rather than the standard Scan-Speak D2008.

(The OW1 is ruled out as it’s too low sensitivity)

[Xanthe]

Update after about 20 hours of running in…

The overall character of the speakers hasn’t changed significantly (good, as I still really like them!).

The lowest level HF details are now quite a lot better preserved than with the old tweeters, it’s also easier to hear lyrics clearly - particularly in female vocals. Even more noticeable though, is how much better ‘organised’ the sound is: backing vocals and subtle instrumentation just seem to fit into the soundscape as a whole so much better than before.

On the other hand if I’d not previously improved the crossovers (better wiring and particularly the Mundorf Supreme MKP capacitors), we don’t think we’d have been able to hear the improvements anything like as clearly as we do now.