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Cantata crossover
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iso
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Joined: 29 Aug 2011
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Location: Finland

PostPosted: Wed Jan 25, 2012 10:09 am    Post subject: D/F at resonance Reply with quote

In my previous tread I mentioned that D/F is actually better at resonance due impedance max. As max is roughly 30 ohm, you get real electrical 6,5 D/F from 0 ohm source and 5,4 D/F from 1 ohm source at B139 input.

Above mentioned figures are reasonable at resonance. They also show how little amplifiers output impedance can change damping, if there is considerable inductance between source and load.

At 70-250 Hz D/F:s are considerably worse, close to 1, as load decreases close to 7 ohm and source impedance increases due reactance of inductors.

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iso
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PostPosted: Tue Feb 07, 2012 7:58 am    Post subject: QED 79 Reply with quote

Snake oil cured Cantatas.

I tried to improve low level resolution and hardening of sound at upper midds with various ways. When I upgraded internal wiring from inputs to midd/hi crossover and from crossover to B110/T52 with QED 79, I finally got Cantatas performance to be as expected.

I used originally ordinary 0,75 mm2 speaker cable for midd/hi frequency and 1,5mm2 for B139. QED 79 seemed to tame nasty upper midd hardness that I supposed to be some diffraction effect. Also low level detail was improved considerably at same time.

Improvement was such that it could be heard at once. I suppose that reason for this is crossover location at well in back panel and removable front panel. These mods increased lenght of wiring considerably.There is now slightly over 1 m wire between crossover and B110 0r T52. The reason for this mod was my idea to locate magnets and crossover coils as far as possible to each other. This also makes it easy to adjust crossover.

I have considered this wiring stuff in past decades to be mostly nonsense. Last year I have heard myself things that have made me to think, that we do not know too much about effects of wiring. I ques I have to change B139 wiring soon...

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iso
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PostPosted: Sat Mar 10, 2012 2:31 pm    Post subject: Improvement on upper mid hardness of Cantatas Reply with quote

I upgraded my late 90:s Sony CDP XA-30 ES CD player to 2nd hand Audio Research CD3 mk. II. New CD player is roughly 5 years newer design of slightly higher quality. This change of source removed almost all remaining hardness on upper mids.

The new player has considerably quieter background, therefore reproduction of music seems to be quite much more accurate. It was funny to note that even reproduction seems to more accurate, sense of space is now much more on left to right axis. Earlier depth and height information was much better.

Ambience is also quite good when there were not too many players playing at same time. When mix is dense and several players are playing same time, sense of space seems to disappear from Cantatas.

It is possible that this has nothing to do with Cantatas. ARC has grounded mains lead ad Sony used ungrounded lead... so grounding arrangement can make these things happen... but I have tried to arrange grounding every way I can imagine. But nothing in grounding seems to be straight forward. 2 years ago when I got my setup performing reasonably well with Sony, it took 2 months to try too may ways and I had to modify both pre amplifier and power amplifier groundings... and there was no way to get pre amplifier sound good with legal grounding... ie. green wire to chassis ground...

BTW I haven´t upgraded woofer wiring yet... but if anybody have any ideas for my ongoing Cantata project, your response is most welcome.

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proffski
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Location: Tewkesbury UK

PostPosted: Sat Mar 10, 2012 7:11 pm    Post subject: Re: Improvement on upper mid hardness of Cantatas Reply with quote

All my Hi-Fi equipment has always been well grounded.
A three metre copper pipe driven into the ground using the water hose method.
Never looked back... Smile
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iso
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Joined: 29 Aug 2011
Posts: 215
Location: Finland

PostPosted: Sat Mar 10, 2012 8:44 pm    Post subject: Grounding 230 VAC line Reply with quote

I have considered if it would be beneficial to make own AC supply to audio equipment using isolation transformer with 115 + 115 VAC output. If secondaries are connected in series and center tap of secondaries is connected to AC ground bus, or maybe even 3 m copper pipe in the soil, you would have nicely balanced 230 VAC power line.

Using this idea impedance from both ends to ground would be quite similar, much better balanced than conventional one end connected to ground set up.
Conventional RFI filters should work much more efficiently after proposed set up, as they are usually connected such a way that balanced line would improve their performance.

This set up does not offer isolation from ground, but would be also safer than conventional set up, as you have only 115 VAC against ground instead 230VAC.

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iso
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Joined: 29 Aug 2011
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Location: Finland

PostPosted: Mon Apr 09, 2012 1:25 pm    Post subject: B139 wiring upgrade Reply with quote

I upgraded B139 wiring with Eagle silver line cable. There was no other reason to use Eagle, but I happened have suitable lenght lying around. Also previous QED upgrade on hi and middle sections suggested that it was worth to try. This LF wiring upgrade proved to make sound quality more accurate.

Soldering this unnecessary thick (4mm2) cable was not pleasant experience. I probably heated input terminals too much. I lost contact on one LF terminal time to time. Most often it did record similar 8,4 ohm as other speaker, but LF did disappear on this speaker sometimes.

This loss of LF made me think about input terminals. I used Monacor branded gold plated bi-wire economy terminals. They are probably not best terminals available... but they are priced fairly and they had enough room for cabling I have used.

I reasoned that if heat can distort contacts enough to make temporarily open circuit, maybe I should solder gold plated tabs, post and nut together to improve contact. I suspect that post is not machined one piece assembly, instead post is probably pressed together. Consequently this press joint is inside the assembly. I suppose there is nothing I can do to improve this part of contact.

However, I felt this extra soldering was also worth the trouble as this improved also presentation of sound. I suppose that almost all the hardness, I have previously complained, has now been removed.

This cabling issue makes me to think all the possible variants of cabling available. You can probably tweak reproduction of sound as you wish with different cables. This seems incredible. Last year I thought that electrolytic caps and cored inductors were biggest hindrance for proper reproduction of sound. Now I can see that there was nothing wrong in basic design of Cantatas. During production you have to skimp little everywhere. Therefore you can improve sound design considerably if you fix all small shortcuts made during production. This wiring issue makes me also think if inductors and PCB tracks had been made also using OFC LC copper.

Even with previous tweaks, I feel that LF performance can be improved further. LF lacks authority somehow. LF seems to be flat to roughly 40 hz, but there is not enough grunt.

I have used B139:s of 1979 vintage and I have extra pair from 1975 which seems to be quite similar. I remember somebody has been saying that late production SP1044 are more consistent than early SP1044. Also 70´s and 80´s data sheets point out that different materials have been used, as thermal handling has been improved... also slight variation on T&S have been recorded.

Does anybody have good information how different vintage SP1044 differs from each other ... and which one is most usable in Cantatas. I suppose one reason for my thought about Cantatas being a little light on bottom octaves is closed box tuning. I have feeling that port resonances on vented boxes are one reason for illusion of LF grunt.

Anyway good B139/SP1044 info is most welcome.

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iso
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PostPosted: Wed Jul 04, 2012 1:22 pm    Post subject: floor coupling Reply with quote

Several improvement has been made to signal source for Cantatas. They are now performing quite well.

However interface to room seems to have some problem. There are no too severe standing waves in LF. However when listening acoustic guitar at pretty high level, peaks maybe in 10W range, the room and cabs seems to resonate somewhere between low E to A string. Cabs do have felt pad under all 4 corners. The concrete floor is lined with oak parquet. Oak is glued directly to concrete.

I tried if 2 thickness cardboard under Cantatas would help. Cardboard reduced this resonance or ringing to tolerable level. However HF and MF performance was now so dull, that isolation was not clearly the solution to this problem.

My friend advised me that maybe I should try spikes. Construction of cabs is now such that spikes might do harm to bottom panel glue joints. Therefore I installed 3 aluminium cones between the cabs and floor. This also reduced ringing but also made MF and HF dull, maybe not so much as cardboard sheets. It seems like there is considerable more distortion on MF/HF and this makes the speakers to sound quite dull with cones or cardboard isolation.

It seems that Cantatas are performing most favorably here on felt pads. It is funny as most audiophiles seems to prefer coupling with spikes. Others, like Max Townshend, seems to recommend decoupling/isolation from the room.

Effects seems to be considerable, even weight of Cantatas is something like 34kg ea. Any ideas how and why?

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Kimmo
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proffski
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Joined: 22 Aug 2003
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PostPosted: Wed Jul 04, 2012 4:50 pm    Post subject: Re: floor coupling Reply with quote

Interesting!

Have you got neigbours?
Easier than an anechoic chamber but try listening to them outdoors if you can.
You can learn a lot about the behaviour of the enclosure / transducer interface. Shocked
Obviously well recorded instruments are important, no room for studio processed & amplified garbage here! Smile
_________________
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
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iso
Senior Contributor 200+


Joined: 29 Aug 2011
Posts: 215
Location: Finland

PostPosted: Thu Jul 05, 2012 1:15 pm    Post subject: neigbours Reply with quote

Very good idea... listening outdoors newer came to my mind even I remember Hifi News used to measure speakers outdoors on 6 m pod in 80`s. However there were some practical limitations on this measuring set up as Martin Colloms mentioned. They were unable to use standard measurements when reviewing Tannoy Westminster´s.

Neighbours might also be problem if they get proof about my mental disorder, when I rig my audio gear to my garden and start tweaking them. I might end in to mental hospital.

Anyway, it seems that biggest problem is now enclosure/room interface. I can reduce ringing to tolerable level with cones or cardboard and HF/MF performance is good with felt pads. It seems to me that cab to floor coupling is the cause of this resonance and the best compromise to date is to use felt pads.

However it might be possible to improve HF/MF performance with different T52 and B110 gaskets... original gasket are used now, T52 cork gasket is in very good condition but B110 gasket is quite flat...

Best Regards

Kimmo
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