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Trying to re-create my fathers setup

Printed From: Graham Slee at Hifi System Components
Category: And the rest
Forum Name: Amplification
Forum Description: Share your interests or views on amplifiers, preamps, etc
URL: https://www.hifisystemcomponents.com/forum/forum_posts.asp?TID=4409
Printed Date: 22 Sep 2019 at 6:04pm
Software Version: Web Wiz Forums 12.01 - http://www.webwizforums.com


Topic: Trying to re-create my fathers setup
Posted By: Andrew123
Subject: Trying to re-create my fathers setup
Date Posted: 24 Jan 2018 at 7:35pm
When i was a kid, my father had Quad 33 and 303 amps with Leak Sandwich 600 speakers. 
I was given a near perfect looking Quad 33 with the power amp. I had it running beautifully with an old pair of Kefs.
Then a near brand new pair of Leaks came up. Not a mark on them. I heard them being played through a valve Leak amp and they sounded great. These are big speakers - 12" bass drivers and 2 other drivers. Got them home and plugged them into the Quad and they really don't sound good. There's distortion in the background. I assume the Quad can't quite handle them. I assumed because my father had the same setup it would be fine.
Anyone have any experience with this king of setups that could give me some clues? I'm not technically great but i did check the resistance of the speakers (4 - 8 ohms) and the Quad (4 - 16 ohms). 
Would be great to get them working.





Replies:
Posted By: Richardl60
Date Posted: 24 Jan 2018 at 8:09pm
Andrew hello.

To recap the quad/key combo was fine?

The leaks you heard were fine?

Your combo is not fine?

I would be surprised if they were incompatible though don’t think the 303 is great at difficult loads.

It could be possible the amp or speakers do have a fault but when less stressed it behaves ok?

Do yo have access to other amp/speakers in your own home this may show up where the problem sits?


Posted By: Graham Slee
Date Posted: 24 Jan 2018 at 9:26pm
The 12" sandwich type drive unit goes scratchy when given a bit of drive. The transistor 303 will drive it harder than the valve Leak at low frequencies. If it is the polystyrene/aluminium faced 12" driver it comes apart for cleaning out the debris that usually accumulates between magnet and voice coil after a number of years. The Leaks may look new but I reckon they'll have been used quite a bit. Realingning on assembly could prove tedious.


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Posted By: Andrew123
Date Posted: 24 Jan 2018 at 10:08pm
Hi. Thanks very much for coming back.

Yes - that's about right. I've heard the speakers play from another amp and the amp has been driving some smaller Kefs for a while with no issues. 
Both of the Leaks have exactly the same gritty distortion - not very loud but quite noticeable.

I'm going to see if i can borrow a more powerful 405 power amp at the weekend to see if that helps.

I'll let you know what happens!

Andrew


Posted By: Andrew123
Date Posted: 24 Jan 2018 at 10:26pm
Hi. Thanks for getting back to me.

Yes - it is the polystyrene/aluminium driver. Taking them apart sounds a bit scary! 
I'll see if i can find some instructions.

I'm going to test them on a more power power amp just in case the old Quad has seen better days. Probably worth a check.

Should have bought those Leaks you renovated a while ago!


Posted By: Graham Slee
Date Posted: 25 Jan 2018 at 12:58am
Hello Andrew, I'm afraid I don't think driving them with a bigger amp will make much if any difference. It would seem you are witnessing the same scratching noise as I and many more people have. I do understand what you are trying to achieve and your fond perhaps nostalgic memories and feelings - I'm a softy too, but I think you may end up moving the Leak speakers on. They're old and time has taken its toll. They will only perform (if you get them working properly) stood with their backs to the wall. They need that to do any worthwhile bass. And placed like that they will not image. If I'd had the room (and more to the point if I'd got WAF) I would have used the best pair unmodified as furniture. Admittedly they do look the part. And apologies if you think my reply unhelpful or insensitive.


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Posted By: Andrew123
Date Posted: 27 Jan 2018 at 5:00pm
Hi Graham

So I took the speakers to a friends house with a Quad 44 + 404 power amp. As you predicted they were exactly the same - very scratchy. Probably even worse than before. Bought them home and left them for a few days and thought about where I could use them as coffee tables.

Then a rather surprising thing happened. I was about to bring them into another room when i thought I'd give them one last go - and they worked absolutely fine. In fact rather well. Then i noticed that I'd left them upside down - the only thing that denotes which way up they are is the LEAK text along the top. 

Could it be that the cones on the woofers have dropped over the last 30-40 years and were rubbing on the magnets and turning them upside down has pulled them away? If so I could spin them around 180 degrees and turn them the right way up again. If it takes another 40 years for them to drop again I probably won't be around to hear it.
Andrew


Posted By: Richardl60
Date Posted: 27 Jan 2018 at 6:20pm
Sounds likely Andrew. Yo7 could try by taking the drivers out and rotate them 180 degrees.


Posted By: Graham Slee
Date Posted: 28 Jan 2018 at 7:21am
I guess it's sag in the bass cone and that's pushing the voice coil out of alignment and so it catches causing the scratching noise. We have to remember that back in the day this was innovative but not fully researched or perfected as cones were later to become.

I would look into obtaining a paper surround replacement drive unit, something like a Fane Sovereign 500LF. I am sure you'd get good sound from it. I think such a low-compliance driver should help the cabinets produce an acceptable sound.

In fact, the 12-300 should do it!

https://www.thomann.de/gb/fane_sovereign_12300.htm" rel="nofollow - https://www.thomann.de/gb/fane_sovereign_12300.htm

This being 8 Ohms and your Leaks maybe 15 Ohms? The simple crossover might well produce a decent sound, and the mid/tweeter would be attenuated by comparison meaning you could place them away from the walls and could get a decent tonal balance.

The fit might be a fiddle. Would I do it? Yes, but I'm an experimenter...


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Posted By: Andrew123
Date Posted: 04 Feb 2018 at 3:12pm
Hi Graham

Thanks very much for the advise. I've sensibly taken it and ordered the Fane Sovereign drivers. I'll let you know how i get on!

Andrew


Posted By: Andrew123
Date Posted: 12 Feb 2018 at 4:20pm
Hi Graham. Well you were right on both counts - the new woofers were quite a hassle to fit but the speakers now sound great. Thanks again for your suggestions.
Andrew



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