Are these speakers worth refurbing?

[DSJR]

A shame Robin isn't readily available to doscuss it, but I PROMISE you that these speakers weren't in the slightest bit "cobbled together" and that much listening, at our KJ branch amongst other places, was carried out in conjunction with measurements.

I think that presence dip is as much to do with the age and development of the drivers used back then - these things really have improved in recent times I believe. What you need to do is a computer model of the crossover slopes in conjunction with the driver characteristics to see how the crossover works and whether anything can be done without replacing either driver (or both). The fact that the off-azis performance in the review above is so good means that Robin got the phasing right (he's a great mathematician) - he'd had years fighting the LS3/5A batches he'd made for Audiomaster and was quite used to selecting components etc to get each batch through testing (KEF had tremendous variability issues with those drivers back then and every other batch would fail on forst testing - a bloody nighmare, the 3/5A).

You may just find that a modern tweeter will have far greater bandwidth at the lower end of its range and Wilmslow Audio may possibly be able to help. This really is where the DIY aspect comes in, together with computer simulations of the final results - someone here should be able to point you in the right direction..

Hope you can make something great out of something that's still good

[Kaiman]

I have a suspicion that they may well have overcooked the rolloff of the crossover by doing it too early

That's what I suspect too.

[Kaiman]

What you need to do is a computer model of the crossover slopes in conjunction with the driver characteristics to see how the crossover works and whether anything can be done without replacing either driver (or both)

That's what I had in mind to do in due time, after learning how such things are done in the first place.

Robin got the phasing right (he's a great mathematician)

Indeed I have the utmost respect for him. I understand that his speaker design philosophy evolved over the years, which would make discussion all the more fascinating but alas, one cannot have everything. If you are in touch with him, please convey my thanks for a 30 year old product that has stood the test of time.

something great out of something that's still good

That's why I don't want to make any irreversible changes. In case things go wrong, I'd like to be able to put everything back and just make do with replacing old XO components.

BTW does anyone have any clue as to the white stripe Audax woofer?

[Kaiman]

Gentlemen, many thanks for the discussion so far. At this point I'd like to model what I can do with the existing drivers. Is there XO design and simulation software that you can recommend? Freeware or reasonably priced (less than three digits) is preferable. Since the box is ready, the quality and comprehensiveness of the enclosure design and tuning part of the software does not matter I guess, it's just the electronics/XO part of it that does. Any suggestions?

[Kaiman]

After much perusing the internets I came to the tentative conclusion that the Volt BM220.8 woofer
http://www.voltloudspeakers.co.uk/Lo...y_bm220_8.html
could be a suitable replacement for the Audax HD20. It is very robustly made and should have impeccable sound quality for an 8 incher. It is also usefully sensitive, about 3 dB on the Audax, which means it can play as though driven with twice the power compared to the Audax.

My biggest problem with finding a replacement was mounting diameter. The Audax has 4 screws on a 222 mm circle, and this is too big for modern 8 inchers. The Volt has its screwholes on an 218 mm diameter circle, so I may have to file each about 2 mm outwards, which shouldn't be too hard to do.

It's the same problem that has hindered my search for a replacement tweeter. The Audax HD100 is mounted with 4 screws on an 86 mm diameter circle. I'd really like to use a bigger tweeter, hopefully around 1.2-1.3 inches, and these usually have large faceplates with widely spaced screws. The idea is to cross at around 2 kHz, maybe even lower, for an even dispersion characteristic. So far I have not been very fortunate. The only tweeter I have found to have a perfect fit is the Fountek NeoCD1.0, which is a fragile ribbon that cannot possibly be crossed low. There are 3 tweeters from the Scanspeak Classic line, the 2905 series, that fit on 90 mm, so they will need a little filing too.

The only other option I've been considering is to have a custom waveguide made, modelled after one of the few shallow plastic waveguides on the market, and then mount whichever tweeter I want on it. This will also improve sensitivity, lower distortion, and facilitate an even lower cross frequency.

As usual, any ideas will be very much appreciated.

[Rare Bird]

So how did Rich go on with his Crossover Rebuilld?

[Kaiman]

He probably does not follow the forum any more. I've sent him a PM with some questions, but he never answered.

[Mothman]

My apologies for not replying to this thread and Kai’s PM’s at the time, though I don’t think I could have added anything useful to the discussion, his technical knowledge obviously being far greater than mine.

Earlier in the year I decided to step back from the forum for a short while after experiencing a number of gear failures within a short space of time which left me feeling deeply frustrated. I guess having an interest in vintage gear but without the knowledge or ability to keep it working is probably not a good combination.

Unfortnately the re-capping of the Audiomaster crossovers was one of my disasters. This was my first attempt at DIY electronics and it did not go well. I purchased some new Electrolytic Caps from Falcon Acoustics but my ham fisted attempts at soldering meant I ended up damaging the metal circuit path on this first crossover board, at this stage I decided to call it quits and have left the second board untouched. I am hoping that the damaged board may be salvageable by using some form of connector between the caps but have decided to leave this until I can get someone who knows what they are doing to look at them.

Again my apologies for not replying at the time.

[Reid Malenfant]

Yes, easily salvageable Have no fear on that score

Good to see you about again by the way Rich

[Mothman]

Thanks Mark good to hear they may be fixable. It's also good to be back