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B200 SP1070 8 ohms

 
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vans60
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Joined: 21 Oct 2013
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PostPosted: Wed Oct 23, 2013 9:04 am    Post subject: B200 SP1070 8 ohms Reply with quote

Hello everybody.
I'm french so you have to excuse my poor english.
I have a pair of SP1070 and i want to use them like Kef Celeste 3, in a 17 litres closed box.
Perhaps i dont search for correctly, but i dont find any parameter or specification like T/S or impede curve.
I need those informations for the crossover.

I try to associate the B200 with a Celestion tweeter : T3939.
Thanks for your answers.
David.
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proffski
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Joined: 22 Aug 2003
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Location: Tewkesbury UK

PostPosted: Thu Oct 24, 2013 11:55 am    Post subject: Re: B200 SP1070 8 ohms Reply with quote

Welcome to the KEF forum!

The answer you seek for the KEF SP1075 parameters is not far from you!
Here: http://www.hifiloudspeakers.info/Anatomy/KEFDocuments/KEFDriveUnitsSpecSheets/KEFB200.G_SP1075SpecSheet.html

And here: http://www.hifiloudspeakers.info/Anatomy/KEFDocuments/KEFGermanGallery/pages/p37.htm
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vans60
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PostPosted: Thu Oct 24, 2013 3:24 pm    Post subject: Reply with quote

Hello. Thanks for your answer.
Is the SP1075 realy the same Embarassed ?
[img]http://forum.vintage-audio-laser.com/ressources/image/72868[/img]
[img]http://forum.vintage-audio-laser.com/ressources/image/72886[/img]

I have seen the data of the SP1075 and it's note 5 ohms and a bigger box.

If i can use those parameters, i can start to try to calculate a crossover.

Do you think i can find some curves ?
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proffski
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Location: Tewkesbury UK

PostPosted: Thu Oct 24, 2013 4:58 pm    Post subject: Reply with quote

No, it is mnot the same. I made a mistake, sorry! Smile
I would start by using a similar cabinet volume as the original loudspeaker.

If you can wait I shall see as to what I have in my library regarding the SP1070 this weekend.
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vans60
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PostPosted: Thu Oct 24, 2013 7:17 pm    Post subject: Reply with quote

Of course i can wait Very Happy
It's realy friendly.
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proffski
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PostPosted: Sun Oct 27, 2013 2:10 pm    Post subject: Reply with quote

Sorry, I have looked everywhere but no luck.
As long as you stick to the correct cabinet volume and aim for Q of 0.7 then there should be no problems arising from your intended project.

At least my search found the 'missing' technical blurb I had mislaid for the KEF 104/2! Smile

I'll let you know if anything turns up regarding the SP1070...
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vans60
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Joined: 21 Oct 2013
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PostPosted: Mon Oct 28, 2013 1:22 am    Post subject: Reply with quote

Quote:
At least my search found the 'missing' technical blurb I had mislaid for the KEF 104/2! Smile


Realy happy for you and other members who may need it Very Happy

Quote:
As long as you stick to the correct cabinet volume


i made a box like Celeste 3. 17 litres.

Quote:
aim for Q of 0.7


I'm begginer and don't understand this Embarassed

If i don't find the specifications i'll try several inductances and listen. But my ears are not very entrained Sad

Thanks for your help.
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vans60
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PostPosted: Tue Nov 05, 2013 8:17 pm    Post subject: Reply with quote

Hello, my boxes are finish and i can try some crossover.
I ear them with 6db on the B200 : 1.2mh in serie and 12db on the tweeter : 4.3µf and 0.22mh.
The sound is ok but the level of the tweeter is higher than the B200. I have to put a resistance before it.
Bye.
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speakerguru
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PostPosted: Wed Nov 06, 2013 4:13 pm    Post subject: Reply with quote

at mid to high frequencies, the woofer impedance is inductive, so a series inductor will just attenuate the woofer. It will not roll off at 6dB/Oct. You need a Zobel network across the woofer to make the load resistive then a series inductor will have the effect you describe.
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vans60
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PostPosted: Wed Nov 06, 2013 6:33 pm    Post subject: Reply with quote

Thanks for your answers Speakerguru.
But with my poor school english, it's difficult to understand all that you say Embarassed And the internet translater is bullshit with technical words Shocked
Could you explain what is a Zobel network ?
For the difference of level between the speaker, i have read that the tweeter simply need a resistance in serie to be attenuate. Is it a mistake ?
If i am not enough accurate i put :
inductance in serie for the B200 1.2mh
capacitor in serie 4.3µf and inductance in parallel 0.22mh for the tweeter.
Cordially
David
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speakerguru
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PostPosted: Thu Nov 07, 2013 11:49 am    Post subject: Reply with quote

Re: Zobel see http://www.trueaudio.com/st_zobel.htm
I'm sorry my technical French is not good.

you could select component values by trial and error if you can measure impedance.
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vans60
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PostPosted: Fri Nov 08, 2013 1:00 am    Post subject: Reply with quote

Thanks a lot. Really interesting site.
I can't measure anything. I haven't got the equipment.
I hoped find the T/S and some curves in your excellent forum but visibly nobody have anything about this woofer.

Quote:
I'm sorry my technical French is not good.


Don't be sorry. It's like my english.
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DrBoar
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PostPosted: Sat Nov 23, 2013 9:37 pm    Post subject: Reply with quote

with regard to zobel. Use the data from an other B200 unit and calculat the Zobel network and use those values. Even with values quie far of the correct ones the zobel will flatten the impedance rise a lot. This will be a large improvement over a not using a zobel even if it will not be perfect.
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speakerguru
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PostPosted: Sun Nov 24, 2013 11:04 am    Post subject: Reply with quote

DrBoar wrote:
... Even with values qui(t)e far of(f) the correct ones the zobel will flatten the impedance rise a lot...

Agreed, the values are not critical but beware of dragging the overall impedance down too low when trying to get the woofer impedance flat AND use a resistor of adequate power rating, especially if using a first order roll-off (single inductor).
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vans60
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PostPosted: Wed Dec 25, 2013 11:15 pm    Post subject: Reply with quote

Hello.
After several tests, i can ear with pleasure my first DIY.
[img]http://forum.vintage-audio-laser.com/ressources/image/76075[/img]
I'm agree it's certainly not perfect without measure but they sound nice and the speakers are coherent.
I'll can measure them when a friend will instal his equipement and i can compare with the simulations.
Thanks a lot and mary christmas.
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