Audax KLS11 design modificaions?

[phibes]

I read with some interest an old thread (are you out there Pinkmouse?) which showed a picture of a highly modified KLS11 loudspeaker and a comment that the ultimate aim was to go to an active crossover network and bi-amping with this design.

I am using the KLS11 which is by comparison only moderately tweaked and I'm interested in any comments from other users on the above path to active crossover and bi-amping of these speakers. The KLS11 is a superb loudspeaker and in particular the HD3P tweeter and I'm just curious as to how much better they can be made to sound.

Cheers,

[pinkmouse]

Hi Phibes

Progress I'm afraid has been minimal, due to lack of money...

However, I can suggest a couple of things that you could try fairly simply, that will improve the sound no end.

The first is to make the mid driver work better, and if you read the other thread you know about my thoughts on back radiation. So, get out your power tools, and open up the back of the mid-range enclosure to the outside world. Then stuff it really heavily with damping material, ( I used long haired wool because I had it to hand, but anything should work). I don't have the speakers to hand right now, but I just kept putting it in until it stopped improving.

Once that is done, it also seems to damp out some of the higher frequency nastyness that the driver response plots show, so as an experiment, I played with the Xover frequency between it and the HD3P, taking it in the end about 800hz higher than standard, ( I think, this was a while ago!! ). This seemed to give the HD3P more room to breathe, and resulted in a sound better than any other tweeter I have ever heard. And the ^&*%^&&%$£$ have stopped making it.../sulks...

[phibes]

Hi Pinkmouse,
Thanks for you reply and I can empathise with the lack of money......I think with this hobby it goes with the territory! I did notice on your early thread that you had housed the bass driver in a separate curved enclosure, with separate enclosures mounted above for the mid and tweeter. Did you start with this design or with the original all in one enclosure designed by Gary Holland? Perhaps you've already answered that question in your earlier thread, however, I haven't gone back into the archives yet to read it again.
The higher crossover point for the HD3P is interesting.......what frequencies are you crossing at now? I agree with your comment and don't understand Audax's wisdom in discontinuing the HD3P! Just before Christmas last year I had my RHS tweeter put on a little light show and burn up during a moderately energetic piece of music. I thought I would have to redesign the whole shooting match until a forum member came good with two new HD3Ps that he was not going to use. I purchased both and now have a spare tweeter for the future. Incidentally, both these tweeters have slight wrinkling of the gold dome coating.......have you ever seen this on a HD3P before? By comparison my original is smooth, however, both the new tweeters seem to be performing just fine.
I'm going to rebuild the KLS11 enclosures in the next couple of months and I'll open up the back of the mid enclosure. I'd appreciate any other comments you may have, especially regarding separating the bass driver and the design of that curved bottom enclosure.
Cheers,

[pinkmouse]

Well, the system was built as per the original article, but after using them for a six months or so I felt they could be improved and so started on the design you may have seen.

I split the top box out to avoid vibrational coupling from the bass causing possible distortion in the mid highs. The parabolic design came out of an idea to try and reduce the back radiation from the cones as much as possible. The design was such that the focus of the reflected sound is the back of the magnet, the biggest and densest structure in the box, and this was then damped with about 250g of Plasticine, a non setting modelling clay. The final, ( after many other methods), construction of the curve was done by building a rough jig of the curve, and applying two layers of bendy MDF, (prescored with grooves on one axis). Because this seemed a little live, I then covered the MDF with approx. 15mm concrete, mixed with long haired wool to give a little more structural strength, and then to finish, a 5mm thick flooring grade flexible laminate. After beefing up the construction jig to provide extra bracing, the top, bottom, and baffle made of 18mm hardwood over a 15mm MDF base, was glued and clamped to the curved section.

The two boxes are separated by a layer of neoprene router mat, this seemed to work the best after extensive listening trials.

As for the wrinkes in the HD3P, I seem to remember hearing from the guy I bought my speakers from, that it was caused by being exposed to low pressure in an aircraft's cargo hold. This is why the drivers were not readily available outside Europe. However, I am tempted to take this with a pinch of salt.

[phibes]

Hi Pinkmouse,
Thanks for the info and I'll definately implement at least some of your design changes into the new enclosures.
As for the wrinkling on the tweeters, your point may have substance as I really feel the seller would have pointed out such an obvious fault. The reason I say this is that on certain days the wrinkles can't be seen and on others they are obvious! I'll take notice of the ambient conditions next time they apperar/disappear.
Please drop me a line if you progress your speakers any further as I still have not been able to find anyone else who has built or are using these speakers, let alone willing to talk about them! Was the KLS11 a popular design in the UK and Europe?
Cheers.

[Nuuk]

I am using the KLS11 which is by comparison only moderately tweaked and I'm interested in any comments from other users on the above path to active crossover and bi-amping of these speakers.

The first thing to realise with converting a passive design to active, is that the removal of the passive crossover components will change the alignment and result in a change of the ideal enclosure volume.

The amount of change varies according to the design and the new volume is best detrermined (IMHO) by empirical methods.

Build a temporary cabinet about one third larger than the present one and have some method of reducing the volume in stages.

I found when changing my IPL A2 speakers to active use that I went from a volume of 28 litres to 33 litres.

Going active is worth the effort and with chip amps and a home-made crossover, it doesn't have to be expensive!

[pinkmouse]

Good points, Nuuk, and something that slipped my mind, as I will be going to a terminated line enclosure when I get round to going active with my setup.

BTW, I like the new avatar!

[phibes]

Thanks Nuuk,
My initial idea was to use an electronic crossover removing the passive components to the bass driver and using a separate amp [between the active crossover and the speaker] for the mid and high, leaving the passive components in place for these two drivers. Any thoughts?
In this configuration, is there much to be gained from bi-amping each side as opposed to bi-amping the system? [ie. two stereo amps feeding both channels]
Cheers,

[Nuuk]

After hearing my Gaiclones, a freind built a pair for a mutual friend and they put them in his system with some 2000+ UKP Monitor Audio speakers.

The improvement was stunning (and this guy had previously tried some pretty expensive power amps). But when a second pair of Gainclones were added in bi-amp mode there was another quite clear improvment so I would say go for it as an interim move but do try fully active when you can.

The low cost of the Gainclone really has removed the only negative aspect of active speaker operation, ie the high cost of providing the amplification.

[Alfaa]

HD3P - 101405K

If someone has HD3P (11405K) tweeters for sale I am interested. Even units with gas leakage are interesting.
BR
Alfaa