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Kef inspired.

 
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john & Jake the dog
Junior Contributor 10+


Joined: 20 Sep 2007
Posts: 13

PostPosted: Mon Sep 24, 2007 10:34 am    Post subject: Kef inspired. Reply with quote

Hi everyone, first post here Smile
I have recently been converted to valves after having Exposure amps for over twenty years.
It's been a revelation to me and I wish I had done it sooner.
I have a 15 watt WD Kel 84 and am very pleased with it.
The downside is that I can't run my Isobariks with it, just not enough watts. Sad
I have been looking for some replacements and bought some Castle Clydes bookshelf.
They are brilliant in the mid and top but just don't have any weight to them.
Being on a tight budget I bought two tattyMission 710's for the cabs, at a pound I thought it was worth a shot.
A WD forum member sold me two big magnet B200's and B139 radiators with xovers from the Calinda's.
I have put these in the cabs with the original Seas tweeter.
Just amazing, I have the basic sound of the Isobariks with a little more detail in the treble.
Happy now to sell the Bariks and put these boxes right, rebate drivers and re-veneer.
Anyone else made anything similar?
cheers


before
after
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john & Jake the dog
Junior Contributor 10+


Joined: 20 Sep 2007
Posts: 13

PostPosted: Wed Oct 03, 2007 12:16 pm    Post subject: Reply with quote

Hi,
this is a trace using a mic from the listening position of a 20/20 sweep.
Could anybody please comment on the apperent upper midrange dip as the speakers sound fine to me.

any other comments would be most welcome.
cheers
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speakerguru
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Joined: 18 Nov 2005
Posts: 954
Location: Green Hut, Tovil

PostPosted: Wed Oct 03, 2007 3:36 pm    Post subject: Reply with quote

Welcome to the forum and I apologise if my comments are negative.

Why would a Calinda XO work with anything other than a T27 in a Calinda shaped box?
What's a 20/20 sweep?
How does the measurement system reject room reflections?

My kitchen radio sounds "fine" but hi-fi it ain't Wink
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john & Jake the dog
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Joined: 20 Sep 2007
Posts: 13

PostPosted: Wed Oct 03, 2007 3:56 pm    Post subject: Reply with quote

hi, thanks for your comments. Smile I'm in the dark a little so any comments are helpful.
I haven't got a T27 tweeter so I thought I would utilise the mission one as to my ears it sounds smooth enough.

Not an expert as regards measurements but I didn't think it would make much difference but looking at the trace they may not be integrating too well. That's why I asked for comments. Smile

By 20/20 sweep I am referring to a CD playing sine waves(I think) sweeping from 20 Hz to 20 kHz.
This ain't no kitchen radio. Marantz 6000ose into WD kel84 valve amp.
I have over twenty years of experience listening to a broad band of hi fi but have mainly stuck to Linn, marantz Exposure isobarik systems but have had a brief fling with Quad 63's.
So when I say they sound fine to me I mean they sound pretty good to my ears compared to my previous systems so much so that they are worth tweaking.
I have tried the mic in various positions in the room and results are very similar. New to the software so am uncertain regarding reflections.

If making the box larger, say Calinda size would help, then I could add to the bottom easily enough as they are going to be reveneered anyway.
cheers
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terry
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Joined: 22 Apr 2003
Posts: 262
Location: UK

PostPosted: Wed Oct 03, 2007 10:26 pm    Post subject: Reply with quote

John

It is good to have you contributing to the forum. As you can see discussion and involvement by members is rather slow at the moment and so your contributions are doubly welcome at this time.

Regarding your project. It is exciting to engage in a speaker building project and especially when you have a satisfactory outcome. As SpeakerGuru has already suggested, however, the approach you have adopted in combining the individual componets on this occasion has been perhaps a bit 'hit or miss'.

We will welcome your continued comments and thoughts.

Best wishes

Terry
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speakerguru
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Joined: 18 Nov 2005
Posts: 954
Location: Green Hut, Tovil

PostPosted: Thu Oct 04, 2007 8:15 am    Post subject: Reply with quote

OK now I understand what you meant.

A sine sweep measurement in a room will be contaminated by room reflections. If you do it in the middle of the room with the speaker on a stand and the mic 1m away it would be a bit better. Before they built their measurement rooms and before they developed impulse testing, KEF used to use this method when the weather was too bad to wheel their 10m hydraulic mast out into the car park. Even so, they used warble tone rather than straight sine waves, from a B & K oscillator, to "average out" room reflections. This only works at mid to high frequencies. At low frequencies you can't warble fast or wide enough and the first floor and ceiling reflections are too strong.

A XO only works as intended into the load it was designed for. I doubt that anything is close, in terms of impedance, to a T27, which had a higher resonance than typical modern 1" soft dome tweeters. As it never hurts to ask the obvious, a T27 was an 8 Ohm unit, what impedance are your SEAS tweeters?
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john & Jake the dog
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Joined: 20 Sep 2007
Posts: 13

PostPosted: Thu Oct 04, 2007 9:29 am    Post subject: Reply with quote

Hi Terry,
thanks for the warm welcome Smile
I found you after looking at the very informative Kef site.
My plan was to make a simpler speaker than the Isobariks but with the same dark sound. I'm on a very limited budget though so the Mission cabs at £1 with tweeters looked ideal.
I am puzzled a little bit though because I can now see after speakerguru's input that there is a mismatch but they sound pretty good, I wonder how much better they would sound with a T27 or whether that would spoil the dark balance I have now.
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john & Jake the dog
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PostPosted: Thu Oct 04, 2007 9:34 am    Post subject: Reply with quote

Hi speakerguru,
I think this is the tweeter,
http://www.seas.no/Gamle%20chassier%20pdf/1%20dome%20H107.pdf
From the xover freqency and the impedance I think it probably doesn't match the B200 Sad
I'll measure it as you suggest and see what happens.
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speakerguru
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Joined: 18 Nov 2005
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Location: Green Hut, Tovil

PostPosted: Thu Oct 04, 2007 12:03 pm    Post subject: Reply with quote

The best way to check if a speaker is neutral or true-to-life is to listen to a vocal recording of someone you know Idea . Make a recording in the open air (or anechoic chamber Wink ) of someone speaking. If they are reading, beware of the effect of a book between mouth and microphone Exclamation . 'Course you'll need a good mic Twisted Evil .........

Playback and alternate with the same person speaking in the same room as the speaker.

On the other hand if you're happy with the sound and are short of time and money, like most of us, just sit back and listen to the music and not the equipment............................... Cool
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proffski
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Joined: 22 Aug 2003
Posts: 1296
Location: Tewkesbury UK

PostPosted: Fri Oct 05, 2007 4:41 pm    Post subject: Reply with quote

john & Jake the dog wrote:
Hi,
this is a trace using a mic from the listening position of a 20/20 sweep.
Could anybody please comment on the apperent upper midrange dip as the speakers sound fine to me.

any other comments would be most welcome.
cheers


Welcome aboard!
Previous comments are probably near the mark, but have you tried moving the loudspeakers, altering their height above floor and seperation before running another sweep?

Or if you can try it in the garden as high as possible...

Question, I do not know of any Castle speaker using that particular mounting method forthe bass unit, could you confirm the model and year?
The size of the enclosure HxDxW would be most interesting!

Andy.
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proffski
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Location: Tewkesbury UK

PostPosted: Fri Oct 05, 2007 4:57 pm    Post subject: Reply with quote

I did once make something similar for my brother in laws dining room.
However the cabinets were by B&O and their internal volume greater than that for the 104aB but less than the Calinda and the ABR had to go on the back of the enclosure.
They did demand some stands higher than the lady of the house would have liked but the sound did improve dramaticaly!
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man standing in a bucket and trying to lift himself up by the handle.
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john & Jake the dog
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Joined: 20 Sep 2007
Posts: 13

PostPosted: Fri Oct 05, 2007 7:48 pm    Post subject: Reply with quote

proffski wrote:


Question, I do not know of any Castle speaker using that particular mounting method forthe bass unit, could you confirm the model and year?
The size of the enclosure HxDxW would be most interesting!

Andy.


Hi Andy,
the Castle Clydes were my previous speakers before I inserted the Kef drivers into the Mission 710 cabs.
Many thanks for your comments.
Peter Comeau, Heybrook designer, has suggested that I perform an MLS test and the trace above may owe more to the room than the speaker.
Similar to your suggestion about the garden.
I'll see what I can manage in this department and get back.
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proffski
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Joined: 22 Aug 2003
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Location: Tewkesbury UK

PostPosted: Fri Oct 05, 2007 11:11 pm    Post subject: Reply with quote

SPLENDID!

I'd liike to run some tests here regarding your interesting response curves. Can you quote please the cabinet size?

Above all enjoy tghe music! I've heard some incredibly expensive loudspeakers with response curves so weird that yours look in comparison ruler flat! Very Happy
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man standing in a bucket and trying to lift himself up by the handle.
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john & Jake the dog
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Joined: 20 Sep 2007
Posts: 13

PostPosted: Sat Oct 06, 2007 9:50 am    Post subject: Reply with quote

Hi, thanks for taking an interest Smile
The cabs are 52 x 29 x 24.5 cm H W D
They are quite well damped with a synthetic wool type material, two large rolls stuffed inside, standard Mission 710.
The walls are two thirds damped with thick bitumen panels again standard mission.
Material is chipboard
The B200 is the large magnet version.
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john & Jake the dog
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Posts: 13

PostPosted: Sat Oct 06, 2007 1:00 pm    Post subject: Reply with quote

hi, I've done an impulse test, don't quite understand the results though.
Soon as I get an extension sorted there'll be a speaker in the garden.

Is my listening room acceptable?


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