IMF RSPM Mk IV help with replacement drivers and impedances

Bo Andersen

New Member
Hi,

Just bought a pair of these. I remember them from my teens visiting Audioscan in Odense, Denmark. Super tweeters, one tweeter and one mid range are all shot. Cross-overs will also need to be recapped.

I am familiar with the British sources for replacement drivers BUT:

1. My "good" tweeter measured 3.6 ohms which points towards 4 ohm impedance? I cannot read any of the printed info on the tweeters. What model was used originally, please? Should it not be 8 ohms? Do you recommend an Audax driver as replacement and if so which one?

2. Super tweeters: Both a blown. I understand that Coles is a good replacement. I understand 16 ohm impedance, is that correct, please?

3. Mid range: One is blown. I would SO like to find a way to repair it. Midwest says it can't be done (well.) Thoughts?

4. I understand the is a Mk IV IMPROVED. Is that just the crossover or, what else what changed, please?

Anybody got a Diagram. I have the standard crossover diagram.

Best regards, Bo in Minnesota
 
Hello,

I realize this is an older post, but my question is basically the same. I plan on restoring a set of RSPM mk IV. I'm missing the tweeters which should be Celestion HF1300 I think and also the super tweeters which were originally Celestion HF2000 as far as I can tell. But I have no clue what the impedances should be 4,8 or 18 Ohm. Can somebody clarify this? Is there a source of reliable data to be found somewhere. Proper documentation would also come in handy. The serial nr of my set is 0315, this indicates it's an early mk IV. If this makes a difference.

Best regards, Gerben (Netherlands)
 
hi Gerben,

Original config was 8 ohm HF1300 and 6 ohm HF2000, in later series 4 ohm 1300's were used without modification to the crossover, this doesn't sound quite as good (to my ears). The general opinion is that the HF1300 is important for the signature op the RSPM, the HF2000 can be easier replaced by for instance the Seas tweeter Falcon offers.

kind regards, Peter (also from the Netherlands!)
 
Peter,
Thanks for your reply. In my collection I have one HF2000 (still to be checked), 1 set HF1300 (I think we measured them at around 5 Ohm) And a complete set of drivers from B&W DM4 (HF1300 and Coles 4001, impedance still to be checked). So I will be on the lookout for a set HF2000, if I cant find any, I need to go for an alternative. I thought Falcon offered the Coles (16 Ohm) as a replacement for the HF2000. The cross-overs still need to be checked, switches cleaned. I was thinking to leave the caps alone if nothing obvious comes up.
 
Peter,
Thanks for your reply. In my collection I have one HF2000 (still to be checked), 1 set HF1300 (I think we measured them at around 5 Ohm) And a complete set of drivers from B&W DM4 (HF1300 and Coles 4001, impedance still to be checked). So I will be on the lookout for a set HF2000, if I cant find any, I need to go for an alternative. I thought Falcon offered the Coles (16 Ohm) as a replacement for the HF2000. The cross-overs still need to be checked, switches cleaned. I was thinking to leave the caps alone if nothing obvious comes up.
I repaired all tweeters in mine
Here is the thread

https://audiokarma.org/forums/index...ls-80s-new-owner-restoration-to-begin.701209/

Athanasios
 
Thanks, very informative. Unfortunately I have only one original supertweeter, the other 3 are replaced with something else.
 
I understand the is a Mk IV IMPROVED. Is that just the crossover or, what else what changed, please?

Improved's came out in two variants, the first was both the Bass driver and Midrange were changed from KEF units to Elac made drivers while the second variant had the full contingent of Elac drivers with no KEF or Celestion parts used anymore. I've always felt that the first Improved version was the best upgrade while the top end upgrade in the second wasn't the signature sound that the Mk IV's were best known for.

These were available as factory built speakers and had "P" prefixed serial numbers while if you were already a Mk IV owner you could buy an upgrade kit which was either configuration along with the "IMPROVED" decal to place on the lower panel just like the Factory built releases. The secret to identifying these was the "P" prefix in the serial numbers.
 
Back
Top Bottom