Bush SRG86 Speakers - Repair or replace?

[Edward Huggins]

The 10" speakers you have been offered should work very well. They look to have curved cones and a plasticised surrounds. As regards the old Celestion 4" unit, I would sacrifice "originality" and use 2 new matched tweeters. There's no (sonic) point in having unmatched tweeters.

[PsychMan]

Update: Received the speakers kindly donated by kirstyd, and have fitted to the baffle ready to install. Along with the similar looking tweeters I’ve found. I have recreated the wiring as it was, but was slightly confused to see the tweeter on one side connected differently to the other. I’ve attached a picture of what I mean. I may be missing something but expected both channels to be the same.

I checked the phasing of the 10 inch units using a battery flashed on the terminals, the tweeters were marked

[usradcoll1]

I like the way the speaker baffle board uses the rubber mounts!
I had understood it was easier on the valves to avoid damage from excess vibration.

[Nickthedentist]

Don't worry re. the wiring, the phasing is right which is all that matters.

And I would have thought that the rubber mounts were there more to prevent acoustic feedback ("howl round") when playing records.

N.

[Edward Huggins]

You could rewire so that both channels are the same. Those replacement 10" units look good (what a generous donation) and may even sound better than the originals.

[PsychMan]

Thanks Edward, I may change it so both are as the left channel, as that seems more logical, though in reality may make no difference.

It sounds really decent. Big thanks to Kirstyd for so kindly sending me these speakers.

I've lashed up a connection for an ipod into the pickup socket, though will experiment and see if it sounds any better with an opamp buffer between.

Turntable next

[kirstyd]

Hi Adam
glad the speakers got to you undamaged .If you type in Bush SRG 86 up top you can see my post from when i refurbished mine .There are some photos of the chassi and the panel with the speakers out of the cabinet .You can see the wiring clearly .The rubber mounts are probably there to stop vibration .This gram can really make some noise when the volume is up

[crackle]

I believe the tweeter -ve should be wired to the bass +ve etc. as the in line capacitor creates a phase inversion. i.e. the right speaker is wired correctly.

mike

[Nickthedentist]

Sorry, forget what I said earlier, I hadn't looked at the drawing carefully enough.

[PsychMan]

Ive looked at various crossover diagrams online and there doesn't seem to be much consensus on phasing for tweeters. Most diagrams I see are actually + to + terminals, but most crossover networks are more sophisticated than on this machine. Ill have a think and try and understand this better before changing anything.

After running a while, around 30 mins+, I did get some distortion on the right channel. I'm going to try substituting or swapping the EL84s to see what difference it makes. I did give one of them one hell of a fright when I put it in the EZ81 socket in a moment of madness. Perhaps it didn't survive as well as I had hoped. Cathode voltages were on spec, but I didn't exactly soak test it, not 30 mins worth anyway....That'll learn me

Depending what I find, I'll try swapping EABC80s next. When I had the chassis out I replaced all of the hunts capacitors and most of the electrolytics, and a large number of resistors that were out of tolerance or visibly stressed, so I think its fair enough to try some trial and error with known good valves. Worth a go before I extract the chassis again. One of the EABC80s is used for detection so It will be interesting to see what affect it has on radio reception too

[Nickthedentist]

The matching of the double diodes in the EABC80 will have a big effect on FM performance, do a forum search for VHF64 alignment.

[PsychMan]

Had another look tonight and I’m wondering if there is an issue with one of the speakers. The fault was not as first thought. Last night after 30 minutes I turned the volume down. Looking again today it’s clear there is distorted sound coming out of the right 10inch speaker at lower volumes. At higher it’s less noticeable and at a point clears. Press my finger on the cone at the back seems to stop it.

I had also tried swapping each el84 and eabc80 with no difference. The next step is to swap the speaker connections for a definitive answer, I might have to wait till another night to try that

[kirstyd]

Hi Adam
I know this may sound a bit silly but have you bolted the speakers down to tightly.Those speakers are not as robust as the old ones and the basket may have been pulled out of shape .I had this happen in a record player .Speaker in cabinet distortion .speaker out of cabinet and its ok .Took me ages to work out that the plywood cabinet was slightly distorted pulling the speaker out of shape

[PsychMan]

Quite possibly, more than finger tight but not my usual level of torque. Come to think of it the originals didn’t seem very tight. I won’t have any more time tonight but I will take the baffle out again and do an assessment. If there is a fault it will be easier to see where that way and I can get an understanding of what’s happening

[crackle]

Originally Posted by PsychMan

Ive looked at various crossover diagrams online and there doesn't seem to be much consensus on phasing for tweeters. Most diagrams I see are actually + to + terminals, but most crossover networks are more sophisticated than on this machine. Ill have a think and try and understand this better before changing anything.

To be honest with this type of speaker setup you probably wont notice much difference either way, but at the least both speakers should be wired identically.

Mike

[PsychMan]

Success! Removed the baffle and connected a test amp to the right channel, same distortion audible.

Slackened off all the little nuts and did them up again just finger tight this time, re-tested and no distortion!

I decided to correct the tweeting phasing and went with what you said Mike, all back in the cab again and sounding nice!

I noticed some loud pops in the left channel and realised the record deck light switch was cutting in and out with the door shut and arcing a bit. Next problem to fix

Thanks once again kirstyd for the speaker donation, seems my cack handed installation was the problem