SpeakerTalk

DarrenHW · Junior Contributor 10+ Joined: 30 Apr 2015 Posts: 18

Hi,

This is my first proper post here so hopefully it's in the right place?

A couple of weeks ago I picked up a pair of KIT3's, after a quick listen they sounded like they had the potential to displace the Celestion Ditton 44's I have. As the 44's have been rewired and recapped I thought it only fair to level the playing field. I've rewired with 2.5mm Van Damme Blue (as I had it) and recapped the x-overs with Alcaps.

The x-overs original to the KIT3's had a 60MFD which is usually a 30MFD is every schematic I've seen:

Unsure of what to do I ordered 60MFD and 30MFD and installed new caps like for like:

It didn't take many minutes of listening to realise the Mid range was too recessed so I swapped this for 30MFD with far better results. I'm not sure why the x-overs originally had 60MFD installed, but it's not the only irregularity.

You'll see in the photo there has been some kind of "super" (?) tweeter installed in parallel with the T27 which I've disconnected and the B139 in this speaker has been replaced with the newer version (the other has the original). There was an air gap around the new B139 where the original cut out was too large so I created a filler piece from some 6mm PLY:

I then rotated the mid and bass applied some rubber restorer and have had them burning in and loosening up for about 80 hours now. I've looked around but can't find any instructions for the DIY cabinets, these cabinets are constructed from 3/4" chip board and are ~ 750 x 325 x 400mm external. They're stuffed like this:

Any thoughts on the stuffing?

I have them sat on some 400mm stands which brings them up to a pretty good level. Any other recommendations for getting the best out of them?

Thank you,
Darren.

proffski · Posted: Fri May 01, 2015 8:59 am Post subject:

Interesting, and thank you for sharing.
Do I see an extra speaker (tweeter) in the top left hand corner?
For improvements you may consider the Falcon Crossover.
http://www.falconacoustics.co.uk/crossovers-ls35a-networks-filters-falcon/crossovers-ls35a-networks-filters-falcon.html

Having a meander here is worthwhile.
http://www.hifiloudspeakers.info/Anatomy/Crossovers/AnatomyCrossovers.html
_________________
I contend that for a nation to try to tax itself into prosperity is like a
man standing in a bucket and trying to lift himself up by the handle.
-Winston Churchill

DarrenHW · Junior Contributor 10+ Joined: 30 Apr 2015 Posts: 18

Hi proffski, yes an additional tweeter has been added. I don't know what it is, it appears to be something Russian from the writing on it? I disconnected it when I rewired them, I've only left it there to blank the hole.

Thanks for the links, I did contact Falcon for a recommended updated x-over but got bored of waiting for a reply (as yet still not received) so I just ordered the caps.

I've seen x-over No.33 recommended here http://www.falconacoustics.co.uk/crossovers-ls35a-networks-filters-falcon/kef-concerto-upgrade-super-power-kit.html?

habrune · Posted: Sat May 02, 2015 9:17 pm Post subject:

Hello DarrenHW,
Interesting project. You mentioned you applied some 'rubber restorer', could you please share what you use to restore the rubber? I'm stuck with aging B139's, the rubber loses its weakeners (evaporation) and fs goes up into the 35-40Hz regions. I thought it would be impossible to get weakeners back into their place between the rubber molecules, but some hope pops up now....(tried vaseline, glycerine etc, to no avail)

audiolabtower · VIP Contributor 500+ Joined: 06 Jan 2009 Posts: 686

Restoring the surround will depend on the exact material used, eg a nitrile rubber of otherwise neoprene, butyl or styrene etc. Derek Hughes (Spendor designer) has had success in the past on some specific later Spendor drivers with Dot4 brake fluid where the surround hardened after many years, but this only affected a small specific number of drivers in specific production dates where the surround supplier had changed material. Brake fluid is of course specifically designed to stop "rubber" brake pipes from hardening and cracking. It must be applied to the roll only, avoid any contact with plastics or adhesives rigorously, in moderation, and wiped off after a few hours. He has reported fo reduction from a measured over 100Hz back down to 50 Hz with this method on smaller drivers. I am not suggesting you do this without researching the exact material in your 139s first, since you may ruin them, but as information of a method that is proven to work with the correct materials, though the long term effects remain unknown till another decade passes!

speakerguru · Posted: Sat May 02, 2015 11:26 pm Post subject:

I've had some success with this http://griptyresoftener.com/ on 60s and 70s Moulton bicycle tyres; never tried it on speaker surrounds though.

DarrenHW · Junior Contributor 10+ Joined: 30 Apr 2015 Posts: 18

I use Auto Glym Bumper & Trim Gel:

It's for plastic and rubber. Use it at your own risk, I don't know whether it will damage the rubber over time? Personally I've had great results with it, I first used it about a year ago on a pair of Ditton 44's, the surrounds are still soft, supple and shiny.

habrune · Posted: Sun May 03, 2015 11:05 am Post subject:

Thank you all very much for the variety of tips. I'll try on some remote parts of the rim first (having been warned loud & clear). Dot 4 brake fluid is at hand, as I'm changing the brake leads of my classic Honda (becoming too soft... it s never right). I know it is very agressive to paint & plastics. I'll report back when (whatever) results are clear.

iso · Posted: Wed May 06, 2015 9:43 am Post subject:

Brake fluid was old second hand auto jobber trick to make old tired tyres look shiny. As far as I remember tyres looked even worse after couple of weeks on the road. So test before...

I do remember one peculiar way to use brake fluid in eraly 60´s. My grand dad used to have East German Ifa motorcar from early 50´s... I suppose it was 1953 model. Winter time is usually quite cold here... mercury in the thermometer will drop sometimes below -30C level. But... there was no cabin heater in the Ifa... so my grand dad used to spread brake fluid to inside surface of windscreen to avoid ice formation to windscreen due mist in the cabin. Tough times...

Best Regards

Kimmo

DarrenHW · Junior Contributor 10+ Joined: 30 Apr 2015 Posts: 18

habrune · Posted: Wed May 06, 2015 12:49 pm Post subject:

Thanks for the warning! Wow, nearly solid mercury....

DarrenHW · Junior Contributor 10+ Joined: 30 Apr 2015 Posts: 18

I've been listening to these for the last week now and they're really growing on me. In comparison to the Ditton 44's, the sound stage from the KEF's is far larger, however the bass from the 44's has more slam but the KEF's possibly go deeper, the KEF's produce more detail but the Celestions are more aggressive, the KEF's have a more natural mid but the 44's don't have a lisp

This is how my last week has gone, switching between the KEF's and the 44's both have different strengths and weaknesses. I find the 44's more exciting but the KEF's more natural and detailed, if only I could keep the bass from the 44's with the tweeter and mid from the KEF's.

What I'd like to do now is build a separate cabinet for the B110/T27 and leave the B139 in the existing cabinets. I'm thinking about a LS3/5a cabinet but keeping x-over values as they are for now just longer wires to allow for 2 cabinets, is this a good or bad idea, any recommendations for this?

proffski · Posted: Mon May 11, 2015 1:37 pm Post subject:

Have you considered changing the HF filter section for the Acoustic Butterworth as in the 104aB for example?
Link: http://bilder.hifi-forum.de/max/588660/kef-104a-crossover-with-extra-resistor-version-b_137250.jpg
_________________
I contend that for a nation to try to tax itself into prosperity is like a
man standing in a bucket and trying to lift himself up by the handle.
-Winston Churchill

DarrenHW · Junior Contributor 10+ Joined: 30 Apr 2015 Posts: 18

Hi Proff,
No, I'd not heard of the 104's until your post, I'll have to read up on them, I do like an ABR.

DarrenHW · Junior Contributor 10+ Joined: 30 Apr 2015 Posts: 18

Thanks for the x-over suggestion Proff, although I'm still going round in circles trying to get my head around the various x-over designs it did lead on to discovering a brief history of KEF speakers. Whilst this has given me even more options (and indeed confusion) for the bass enclosure I stumbled across the CS1A.

Disregarding x-overs for the time being if we may, I think this could be the perfect cabinet (for me) to house the mid/hf whilst experimenting with lf enclosures (and subsequently x-overs). I'd build them in line with these guidlines (http://www.hifiloudspeakers.info/Anatomy/SpeakerSystems/LS3_5a/LS3_5aJohnSmith.html) if applicable? What do you think?