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KEF 107 1 KUBE UPGRADE
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brickx
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Joined: 23 Mar 2008
Posts: 9

PostPosted: Mon Mar 24, 2008 9:53 pm    Post subject: KEF 107 1 KUBE UPGRADE Reply with quote

Hi.
Thanks Terry for getting me in, even though it took a while Wink
I own a pair of 107 1 since last november, and play them through a modified quad 405&44, with a SlimDevices musicserver and Xindak external dac.
The woofers had just been professionally refurbished by Audiolab in The The Netherlands for more than 300,-.
I love the looks and of course the sound stage of the 107.
But in spite the 107's being an improvement in comparison with my last speakers (DIY Vifa/Kef passive), I couldn't imagine this being 'all there is'. I was looking for more control, definition, depth and clearness/freshness in the highs.
And I stumbled along this forum, and read quite a deal actually, wanted to join, but didn't pay enough attention how to get through the initial hassle of registering.
What I rembered most was reading alot about the T33 replacement, but not hearing well defined experiences with having done so. I too have been looking for a replacement, and Ruud from Speakerland (Oss, The Netherlands) recomended vifa's, but wouldn't take them back if I found them unsuitable, and taking the risk of more than 80,- was too much for me. (suggestions what would be the best replacement for the T33 still welcome!)
I also remembered reading about the possiblity of upgrading the Kube, where as the use of it had the effect of losing lots of the high. (I have been using it off and on up till now, not being able te determine what sounded best.) But again I coulndt recall reading of anyone who actually did it, and what his experience was.
I had my Quads modified by Dada Electronics in Antwerp, and was astonished by the new freshness they got by using modern opamps.
As I was busy with a DIY Q303 upgrade with my son, I was mailing with Stefaan from Dada about some difficulties, and decided to ask him some advice about the Kube while I was on it anyway.
He suggested that replacing the old opamps with BB opa2604 and the capacitors as well, would bring an important improvement in sound quality.
I was actually a bit scared to try: it's easy to bust, and I would be without a Kube, facing more costs.
But I had become more confident about my soldering skills due to the 303, and decided to take the risk. Total costs including postal: 56,24.
It was not easy to open the Kube; I even had to drill out an old screw that wouldnt budge. It was a tricky job getting the old opamps out, but I developed a trick and some handyness.
Soldering had to be done carefully, but was not too difficult.
And to my relief it worked right away, and just as important, there was a dramatic change (for the better) in sound quality. So much I wondered whether I still would need to look for a peplacement for the T33's.
The curtains were lifted, beautiful details and depth with a far greater imaging.
So I hope by writing about this experience here, others can determine for themselves if they would like to take a try or not.
I'll be glad to answer any questions if I can, or to recieve other comments or experiences.

Brian
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O'Shag
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Joined: 28 Feb 2008
Posts: 69
Location: City of The Angels

PostPosted: Tue Mar 25, 2008 5:42 am    Post subject: Reply with quote

Hi Brian,

I'm a new member of the SpeakerTalk Forum also. I own the reference 107/1. I think it might be wise to leave the T33 well enough alone unless it is having a problem. It is an excellent tweeter after all. I would venture to say that performance limitations would be more to do with the crossover network parts ie capacitors/wire. I have often wondered if the KUBE could be improved upon, and your adventure in upgrading the opamps demonstrates that the KUBE mod can make a difference. Silver Wire? VCAP Teflon capacitors? I wonder what sort of a difference these might make? Anyhow, well done on tackling the modification on the kube!
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Parts
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Joined: 13 Jan 2006
Posts: 176
Location: Edinburgh

PostPosted: Tue Mar 25, 2008 9:42 pm    Post subject: Reply with quote

Hello BrickX,

Nice to hear your Kube Mods went well, would you be able to post a list of the parts or any schematics or pics of the work you carried out?

I myself have an old damaged Kube (not in use) I would like to have rebuilt, but it also requires new pots for the Q and contour. I would prefer it in a nicer full width case with a better power supply also though.
This is one of my old Kubes which didn't seem too happy with the high output available with one of my Audio Research Pre's. Pre out or tape loop is another area which can affect a Kube's percieved performance, I am sure some have preferences which vary with kit though.

An XLR capable Kube would be usefull, I have heard there was apparently a Pro Kube (would love to find one) but unsure if this was XLR, the other option used to be an early Meridian Pre amp which had Kube DSP settings for use with the R107.

I have also been wanting to find a suitable drop in replacement tweeter to replace the T33, but not found anything with identical specification and fitting as yet.

I agree that the T33 treble ability is a weak area of the R107's performance, this was also pointed out by many of the reviews. I think it may well bring worthwhile improvement having any old T33's rebuilt though, as I am sure with age performance deteriorates.

One option I was thinking of was a pair of Raal ribbon tweeters with custom face plates. Raal can do these with the same size faceplate as the T33, and in a custom 4ohm. (Time, kids and money will have thoughts of this on hold for some time though, as they are pretty expensive.)

Not sure if a ribbon trebble would match the Kef midrange though?

Raal 70-10 spec.
- Frequency response: 2 kHz ~ 100 kHz
- Sensitivity: 92 dB / 1 m / 2.83 V
- Impedance: 8 Ohm
- Program power handling: 150 W*
- *Recommended crossover: 4th order L-R @ 2800 Hz

T33 spec.
- Frequency response: 3 kHz ~ 20 kHz
- Sensitivity: 93 dB / 1 m / 2.83 V
- Impedance: 4 Ohm


They originaly guessed that the T33 may have some attenuation applied by means of two resistors(series-parallel). If I purchase a 4 Ohm version of the Raal ribbons, all I may have to do is to increase the attenuation and keep everything else the same? But I think I gave them the wrong specifcation? (The above spec is correct, but what of the attenuation requirement?)

Could still find a Kef R107 crossover schematic usefull, for the treble and mid in particular. Anyone have one?

Hello O''blocked word',

You mention the crossover components may be performance limiting more than the T33 tweeter, not sure if this is the only case, though it could be improved upon, I believe someone else on the forum was going to ask about crossover upgrades from Wilmslow Audio, not sure if they got that quote. No doubt replacing aged components would help. I myself noticed overall improvement when I fitted new Kef R107 crossovers a few years back.
When my children are older and I have spare money, I may try and have new external crossovers built based on the old ones.

My own Kef are still awaiting me getting some more stuff to finish refurbishing them.

I currently require (when I find suppliers!),

WBT terminals.
New grommets and spacers as Kef used for decoupling the drivers.
Lots of the gasket sealing strip like which Kef use. (Been unable to find similar decent stuff so far)
Allen key machine bolts for all the drivers.
Allen Key machine bolts with recessed heads to replace the top and bottom panel fixings.
New spikes.

And would also like some more stable/secure head/body spigot interface if possible?

Steve


Last edited by Parts on Tue Mar 25, 2008 10:54 pm; edited 1 time in total
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O'Shag
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Joined: 28 Feb 2008
Posts: 69
Location: City of The Angels

PostPosted: Tue Mar 25, 2008 10:01 pm    Post subject: Reply with quote

Hi Parts,

If I understand correctly, the T33 from the outset, was not a good design? Or are you suggesting that it deteriorates over time? My only concern is that when one starts to change the essential components of the 107 ie the drivers, then the sound characteristics which define this speaker will also change.
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Parts
Senior Contributor 100+


Joined: 13 Jan 2006
Posts: 176
Location: Edinburgh

PostPosted: Tue Mar 25, 2008 10:53 pm    Post subject: Reply with quote

Hi,

Both I guess,

From the outset the T33 was a little poor, treble performance was not in the same league as mid and bass. This was also mentioned in the Stereophile review. (Still available for reading online)

My preference is for the fabric T33 over the metal replacement which came later. I remember my local dealer giving this advice also.

Though reasonable, the T33 is by todays standard in particular found lacking. With age the performance does suffer, I am sure others here have mentioned ferrofluid drying up too. Most speaker drivers suffer with age, and some companies do recommend rebuilding or replacing "tired" drivers, I have read mention of ATC doing this with pro monitors.

I think if you have an old pair of speakers which are well used, having the treble units (or other drivers) fully rebuilt or serviced by the likes of Wembly may prove cost effective and worthwhile, and may help bring performance back in line with original spec. No old speaker keeps its tollerance and performance, like any mechanical item this is subject to change variably with age. I myself have new bass drivers fitted, and new mids for my R107, and some old treble units stored. Once I have refurbished my R107, if I myself cannot find better performance from drop in replacements I will have an old pair refurbished, even if they are working well.

No Kef R107 (or any other speaker such as BC1 or LS3/5a) will have its "original" sound characteristics or tight tollerance specification, unless well looked after with a reasonable and up to date service history, eveything inc the bass drivers and crossovers, dampening etc change slightly over the years. Paper softens, spiders loosen up, foam surrounds dry up as do adhesives, coils accumulate debris etc. Crossovers get dull and vieled etc. The most noticable areas which suffer detrimental performance with age are the bass and treble sections of the R107, Kubes too suffer with age but this seems less consistent.

Some of the old "unserviced" R107 which have done the rounds over the years have I feel given many a detrimental view of the speaker, most seem to do a few going cheap rounds on eBay (many without Kube) then disappear. Sadly I feel it is a superb speaker which will not prove capable unless fully serviced with a Kube in good working order, and even then the speaker requires a reasonable amplifier to wake the mid bass up and bring the bass to life. Components and rebuilding of drive units is not cheap, my replacement bass drivers cost over 300, and having the old four rebuilt would have not been much cheaper at around 70 each I believe.

I think as long as you stick with original components and specification replacements then all should stay consistent and true to spec, but changing the treble unit or using a different spec replacement rubber surround instead of foam, or even slightly different manufacturer crossover components will affect the speakers voicing and tonality in some manner. (My own are re-wired internaly with Chord spkr cable which I felt gave an improvement)
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brickx
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Joined: 23 Mar 2008
Posts: 9

PostPosted: Wed Mar 26, 2008 6:33 pm    Post subject: pics and questions Reply with quote

Hi.
I have some pics here if you're interested, and a parts list as requested.

http://www.flickr.com/photos/brickx/

About the T33's. Wouldnt it be great to find a dealer who is willing to try out different combinations of tweeters, as to determine which suits the 107's 'the best'.
It's actually a surprise to me that besides the MG27 (which seems te be not available anymore), that not more has been tried by forum members.
As I wrote, I would have liked to try the Vifa HT 275D2 as recomended by Ruud, but I couldnt get a refund in case I didnt like them.
Thats his good right of course, but I hoped the DIY guru would be a bit more dedicated.
And what would a 107 do with real high end tweeters like Scanspeak.
Does someone perhaps have connections that would enable experimenting, in the hope to find a good replacement for the 33's?
I called Transtec in Rotterdam, they had a replacement (dont recall which one) but also at more than 60,- a piece. And from what I read people were not very enthousiastic about Kef's own alternative.
I also asked Transtec (and Ruud as well) about the crossover, and if it was wise to replace old components.
I was advised it was best to leave them as they were. In comments above I understand the opposite.
Is there anyone who has really done it and described any benifits?
And by your experience: does the quality of the B110 deteriorate with time as well, or do they stay top notch?

Chrz, Brian.
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O'Shag
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Joined: 28 Feb 2008
Posts: 69
Location: City of The Angels

PostPosted: Thu Mar 27, 2008 5:28 am    Post subject: Reply with quote

Parts, your point about aging components, especially those that have been in less-than-ideal environments makes sense. I had not really given consideration to the possiblity of ferrofluid drying up, and this would certainly be critical when the speakers are used at louder levels for long periods of time. By the way, does the ferrofluid serve another purpose other than cooling?

Brian, excellent photos and excellent work! You did a tidy job of soldering. I might gather up the nerve to tackle the job soon. Your information is invaluable.

I wonder if the conjugate load matching network does anything to affect transparency, and would there be any value in attempting to disengage this function?

Cheers
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O'Shag
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Joined: 28 Feb 2008
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Location: City of The Angels

PostPosted: Thu Apr 03, 2008 11:26 pm    Post subject: Reply with quote

Some further thoughts on this.

Brian I think the KUBE job that you've done is excellent.

I haven't heard anyone else's 107s, but mine still sound excellent. They convey the musical message and its structure very well, and this is something many speakers don't do so well.

The bass performance of the 107 is very good in terms of extension and detail retrieval. On some musical material however, one is left desiring a tad more mid-bass presence and volume.

The otherwise superb midrange and treble performance are held back by a slightly perceptable lack of energy in the upper mid / high frequencies. From my perspective as a listener, the B110 midrange unit especially developed for the 107 is a world class driver. If driven within its limits, it operates beautifully well without distortion, and I've driven my 107s hard on occasion.

I am inclined to think that the answer to improving this speaker lies in the crossover components, where upper frequency energy and transparency may be improved by accessing the crossover located in the MF/HF unit. Perhaps a similar result in mid-bass enhancement might be realized through the crossover located in the bass module. Am I making any sense? Has anyone tried modifying crossover components?
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brickx
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Joined: 23 Mar 2008
Posts: 9

PostPosted: Fri Apr 04, 2008 8:26 am    Post subject: Reply with quote

Hi,

I just got a quotation from solens for mg27's. they still have 10 in stock, and ask US$53 per pair (whilst solen being located in Canda....), but also ask US$45 for shipment to the netherlands, which is a very steep amount if you ask me, and makes it not worth my while anymore.
It would cost just as much to buy the newer and better tweeters I mentioned before.

Too bad, because if transport had not been so expensive, I would have tried them out, and been able to share my experience with you all here.
But I'm sure in due time I will find a solution.

@O''blocked word': I looked at changing the x-over parts, but that also looks like a costly project with an uncertain outcome.
And I assume it will depend to some extend on the quality of replacement units; alas in this world better means more expensive. I'm waiting for that inheritance......
Chrz.
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Laemmle
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Joined: 11 Apr 2008
Posts: 22

PostPosted: Fri Apr 11, 2008 9:32 pm    Post subject: KUBE 107 Reply with quote

The best thing I ever did (after purchasing the 107's new) was to purchase from KEF a balanced 'pro' KUBE. I utilize it with my ARC SP-15 pre and McIntosh MC252 amp.

I will not waste time here..........find one of these, it's that good!

Additionally, I had the great George Kaye replace all the factory op-amps and replace with top of the line high end examples....this really kicked it up as it were.
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O'Shag
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PostPosted: Fri Apr 18, 2008 5:04 am    Post subject: Reply with quote

Laemmle,

That professional series KUBE looks to be the business. I would think it is nigh on impossible to find one used out there. From experience with my own 107, I should think it makes a real difference. In my case, the KUBE does slightly take some energy away from the upper frequencies. But it is only slight. My 107s sound marvellous. I've had no issues either.
I'm currently slumming it with The Maidstone. I'm at the front row of a live gig almost every night, while still sitting in my living room. Wink
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Laemmle
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PostPosted: Fri Apr 18, 2008 5:02 pm    Post subject: Reply with quote

Did you contact KEF UK to see if any pro KUBES are in fact available?
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O'Shag
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PostPosted: Fri Apr 18, 2008 6:08 pm    Post subject: Reply with quote

No I haven't. I would be interested if they had one. The original KUBE I have is matched to the speakers. I assume the pro KUBE will allow for change of settings to accomodate different speakers.

I see you've had your 107 since new. I picked mine up about 4 years ago. I have a friend who like you, had his since new. He unfortunately suffers from severe tinnitus, and caved in to pressure from his new young wife to sell his 107/2s in the interest of creating a modern spartan living room environment. They were mint, and he sold them for a $1000 (a steal). I was tempted to buy them myself just to have a second pair.
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Laemmle
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PostPosted: Fri Apr 18, 2008 6:39 pm    Post subject: Reply with quote

Young wifes.........ya gotta love their 'persuasion'!

The pro KUBE only has the ability to change contour and HF/LF cut-off..ie..50 or 20 HZ. Additionally one can run with no active eq....but why would one want to? When George Kaye changed all the oem op amps and fitted top of line high-end examples the sound changed drastically...more open airy..like several veils had lifted.

I think I will purchase a set of T-33 replacement drivers just in case the ferro-fluid in mine hardens....although admittedly I never make a habit of driving them hard.....I live in a one bedroom affair and it takes very little coaxing to envelope the room with major sound output...as you know the 107's could be driven by quality amps of 50 watt....so my 250watt McIntosh is a bit over the top...but one never knows when one wants HEADROOM!
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O'Shag
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PostPosted: Fri Apr 18, 2008 8:44 pm    Post subject: Reply with quote

The results I've experienced with more power have been noticable. I've also found the 107 to be very flexible in terms of room size, where it has delivered better results in a large room but works well in a smaller one also. The manuveurable head unit is a stroke of genius.

I really will have to check into the pro KUBE with KEF.

I did read the excerpt from the SP-15 manual you posted. There seems to be accomodation for bi-amping, but there is only one balanced out. I'm guessing one has to use the single-ended/non-balanced outs for bi-amping.

Have you ever experimented with the 107 as the front channel speakers for a surround system? I was amazed at how good they are used in this way. What do you think of the 107s performance with vinyl?
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