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Old 19th October 2013, 01:54 AM   #11
system7 is online now system7  United Kingdom
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Unless you are a filter specialist, these may not mean a lot to you, but KEF did much more complex things when they used computer modelling on filters. I think they were getting a bit too obsessed with perfecting/flattening their curves really. Lynn Olson talks bout this stuff:
The Art of Speaker Design

The KEF R101 was the best small speaker KEF made at the time. Almost LS3/5A in concept. The KEF 104AB (acoustic butterworth) used the 8" bass unit.

Bigger improvements were found by Spendor and Harbeth with more advanced speaker materials IMO.
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File Type: jpg KEF_R101_crossover.jpg (44.2 KB, 166 views)
File Type: jpg KEF-104ab.JPG (35.1 KB, 161 views)
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Old 19th October 2013, 02:10 AM   #12
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I can read them no problem, but no, I am not a filter specialist. Just learning. The second looks like the 104aB filter network. I used to have a pair of these, but I much preferred the Concerto's. I know they aren't the best, but I just really like how they sound. Interestingly, I found the 104aB's complimented the Concerto's, only the Concerto's have a much deeper bass! Much deeper! Most music types shine on these speakers, even Hip Hop!

I have very eclectic music tastes.

I also have a pair of ESS AMT 1aM towers, and they are influencing me a great deal. I first got a pair of ESS AMT 1 pedestals (10 inch Alnico bass reflex ported out the back) and I loved that Heil Transformer! I then auditioned the 1aM towers and found my sound. These speakers are awesome! They aren't perfect, and a future project of mine will be to tweak their sound more to my liking, but my obsession with finding that 'sound' stopped when I bought them. I also love the way they look. The imaging and the sound field is superb, and the clarity and airiness of the mids to highs is very addicting!

And I still love my Concerto's...
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Old 19th October 2013, 05:00 PM   #13
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Default Picture of my living room with Concerto's

This photo shows, although very poorly, my living room layout with the Kef's. As you can see, I am very limited in speaker placement. I have my 4 year old grand son living with me, so I can't leave the speakers in an exposed area. Behind the side tables is the safest.
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File Type: jpg Concerto's in Living room.jpg (247.6 KB, 149 views)
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Old 19th October 2013, 08:58 PM   #14
sreten is online now sreten  United Kingdom
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Quote:
Originally Posted by system7 View Post
I must be a world expert on KEF speakers. Either that or
I'm just plain talented, you have hit paydirt anyway...
Hi,

Or just deluded and overrating your opinionated "knowledge".
I think its fair to say your expertise doesn't match your opinion.

rgds, sreten.
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Last edited by sreten; 19th October 2013 at 09:12 PM.
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Old 26th October 2013, 12:57 AM   #15
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Last night I pulled my Kef Concerto's from their home over the last 10 months and put my ESS AMT 1's in their place. Interesting how the character of the sound changed for the AMTs from being in the middle of the room, to being stuck in the corners. No flexibility on where I can place them. I now notice how little midrange the AMTs have. I guess before, with the bass being less emphasized, the lack of mids didn't stand out.

Don't get me wrong. They sound very good, but nearly as good as the concerto's in that same place. I placed some concrete slabs underneath them. Not sure if that was a good thing or not, but I am not about to take them out now. It is a pain to get there.

The Kef's are Bass reflex ported to the front, and the AMTs are Bass reflex ported at the bottom rear. I'm not really surprised that the Kefs outperform the AMTs in that location just because with a front ported speaker, being placed in the corners has less of an impact to the sound. At least that is why I think it is like that.

Next week I will be starting on the Kef's.

Last edited by TechnoDweeb; 26th October 2013 at 01:01 AM.
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Old 27th October 2013, 12:08 AM   #16
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That is enough you two.

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Old 27th October 2013, 10:16 AM   #17
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Quote:
Originally Posted by system7 View Post
Unless you are a filter specialist, these may not mean a lot to you, but KEF did much more complex things when they used computer modelling on filters.

The KEF R101 was the best small speaker KEF made at the time. Almost LS3/5A in concept. The KEF 104AB (acoustic butterworth) used the 8" bass unit.
Those crossovers show 2 unique features that KEF pioneered. The bridged T of the tweeter was integral to the Acoustic Butterworth approach. It allowed a controllable notch in the tweeter drive that let you get a combination of electrical and acoustical that were still straight Butterworth rather than having a strong inflection point in the curve at the electrical resonance.

The series capacitance was part of the overall LF shaping. The rule of thumb was to start with a sealed box with an overall Q of 0.9 and size the capacitors to create a flat third order. Works quite well and actually flattens and extends response slightly, plus helps power handling.

The R101 was meant to be an "LS3/5a done right" but it never had the prominance in the market that the BBC unit had. A couple of years later we redesigned the LS3/5a, but that is another story.

David S
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Old 28th October 2013, 05:46 PM   #18
system7 is online now system7  United Kingdom
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Always enjoy discussions with you, speaker dave. For people who don't know, Dave used to work for KEF and is rather knowledgeable about them.

I have been dabbling with some vintage 8" bextrene plus 1" tweeter Audiomaster MLS4 jobbies lately, designed by Robin Marshall in THE TRADITION apparently:
Are these speakers worth refurbing? - Page 8

The whole plastic cone thing is fascinating. Joachim Gerhard likes metal and reed cones currently, rightly pointing out that they have about a third of the stored energy, but for all that a LOT of people like heavily damped cones. It's almost like you either build the damping into the crossover or into the drive unit. You're going to need it one way or another for the smooth, sweet sound.

Students of plastic cones might also find these pages interesting. Rogers speakers which were using polypropylene cones IIRC, superbly documented by Mark Hennessy:
Rogers Speakers - BBC LS5/9

TechnoDweeb mentioned he liked the Concerto's. 3-ways just work better than 2-ways for various reasons, the main ones being that the mid is spared excursion into non-linearity and dispersion is better in the midrange.
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Last edited by system7; 28th October 2013 at 05:48 PM.
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Old 28th October 2013, 08:36 PM   #19
AMV8 is offline AMV8  United Kingdom
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TechnoDweeb
I updated the crossovers on Kef 104'4, Concerto's and on the 101/2 some time ago.
I discussed with Kef ( they were still around then ) the possibility of replacing the electrolytic capacitors in the mid and treble sections with plastic capacitors. Kef replied that the Kef crossover calculations took account of the electrolytic capacitors series resistence and good electrolytics were recomended by Kef as the replacements. If I changed from electrolytic to plastic capacitor then I was advised to add a resistor in series with each changed capacitor. The value being 1 ohm per 10uf of capacitor. I did that and it worked well.
If you do not include the extra resistors I imagine you will change the crossover frequency/profile.
Don
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Old 7th December 2013, 01:25 AM   #20
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Default I'm a bit behind on this project...

Quote:
Originally Posted by AMV8 View Post
TechnoDweeb
I updated the crossovers on Kef 104'4, Concerto's and on the 101/2 some time ago.
I discussed with Kef ( they were still around then ) the possibility of replacing the electrolytic capacitors in the mid and treble sections with plastic capacitors. Kef replied that the Kef crossover calculations took account of the electrolytic capacitors series resistence and good electrolytics were recomended by Kef as the replacements. If I changed from electrolytic to plastic capacitor then I was advised to add a resistor in series with each changed capacitor. The value being 1 ohm per 10uf of capacitor. I did that and it worked well.
If you do not include the extra resistors I imagine you will change the crossover frequency/profile.
Don
Thank you very much Don. That is very interesting. I was aware of the difference in ESR, but I never knew how they calculate it.

Well, once again, I am behind on my project, and I haven't even started it yet! It seems I keep spending too much money on equipment, and have none left for my projects. Right around the time I was planning on starting this, I got a call from my Audio Tech, and he had finished restoring my Bose 1801. I bought this unit in February as a dead unit, and it has been in his hands ever since. In the meantime, I was able to locate the 4401 preamp, that came with an 1801. So now I have my first 1801 back, and there is a really big difference between it and the 1801 I got in the summer. Amazing, the way my ESS AMT 1aM towers just disappear! I love it! So I have been listening to my collection all over again, in between building Lego creatures with my grandson and searching for cool bargains at thrift stores, estate sales, and on kijiji. Unfortunately, that eats up my spending money for parts and my time as I clean the cool things I've found.

I need to sell some of it. I'm trying, but the market seems to have slowed down, or maybe I have an inflated view of the value of these things. Anyway, it looks like this project will be on a pause until after Christmas. I'm getting back on track though.

Stay tuned....
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