SpeakerTalk Forum Index SpeakerTalk
This forum has been set up to facilitate discussion of 1970s KEF speakers and drive units. The owner of the Forum has no connection with KEF Audio.
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

KEF 107/2
Goto page 1, 2  Next
 
Post new topic   Reply to topic    SpeakerTalk Forum Index -> KEF speakers
View previous topic :: View next topic  
Author Message
steve59
Junior Contributor 10+


Joined: 14 Mar 2015
Posts: 17
Location: chicago il

PostPosted: Sun Mar 15, 2015 4:48 pm    Post subject: KEF 107/2 Reply with quote

I'm a new member so forgive me if I missed this thread.
I got a pair of 107/2 rosewood with the kube but I have nothing with a tape loop or pre in. My options are running the kube between a pre and a B&K 4420 amp that has some muscle but not a lot of sweetness or a Anthem 225 integrated pushing the top and the kube before the 4420 pushing the bass bins. What I really want to know is how much does the KUBE affect the mid and treble and if biamping is worth leaving the kube out of the path for the mid and treble. thanks for any reply's
Steve
Back to top
View user's profile Send private message
SaSi
Senior Contributor 200+


Joined: 24 Aug 2008
Posts: 223

PostPosted: Sun Mar 15, 2015 7:23 pm    Post subject: Reply with quote

You can try it out and see for yourself. Different people take the difference from a different angle and some even claim using the KUBE is a degradation of fidelity.

According to the KEF people who designed the 107 and 107/2, the design is an actively assisted bandbass alignment and the KUBE is the means to make the response flat, not only in the bass section but also halfway across the midrange.

Having said that, they also added controls to allow the listener to fine tune the response - probably to taste and room.

BTW, you can't really separate the mid/high pods from the bass boxes and drive them separately - not without some tweaking with an active crossover. The crossover inside the bass boxes pre-processes the midrange before sending it to the pods by means of a high pass filter and probably some impedance equalization as well.

You will need about 70-100W RMS to drive them to 105dB peaks in an averge room of 11'x18' with moderate furnishings.
Back to top
View user's profile Send private message
speakerguru
VIP Contributor 750+


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

PostPosted: Mon Mar 16, 2015 10:21 am    Post subject: Reply with quote

The 107|2 Kube provides fixed LF/box eq. It also provides variable LF eq intended for room eq and variable HF eq. The HF eq is a fixed Q, variable depth notch at 4.5 kHz intended to equalise for a corresponding off-axis peak in the head response.
Back to top
View user's profile Send private message
proffski
Über Contributor 1000+


Joined: 22 Aug 2003
Posts: 1296
Location: Tewkesbury UK

PostPosted: Mon Mar 16, 2015 10:54 am    Post subject: Reply with quote

And a little praise... (Parts 1/2/3 & see other links at end of part 3, including measurements).
Link: http://www.stereophile.com/content/kef-r107-loudspeaker-thomas-j-norton-1995
_________________
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
Back to top
View user's profile Send private message Send e-mail
steve59
Junior Contributor 10+


Joined: 14 Mar 2015
Posts: 17
Location: chicago il

PostPosted: Sun Mar 22, 2015 9:20 pm    Post subject: Reply with quote

Well I tried the speakers without the kube and found the sound flat and lifeless, having said that I currently biamp these jems with the Anthem I225 on the upper binding posts and my aging B&K 4420 with the kube in the path connected to the lower pair of binding posts and find the speakers less forgiving of poor recordings but the magic is still there on the good stuff. I have to say Trying to upgrade kef's from this era with anything new has proven futile for me maybe i'm just conditioned from owning kef's for so long everything else just sounds like speakers.
Back to top
View user's profile Send private message
steve59
Junior Contributor 10+


Joined: 14 Mar 2015
Posts: 17
Location: chicago il

PostPosted: Fri Mar 27, 2015 7:15 pm    Post subject: kube without tape loop Reply with quote

speakerguru wrote:
The 107|2 Kube provides fixed LF/box eq. It also provides variable LF eq intended for room eq and variable HF eq. The HF eq is a fixed Q, variable depth notch at 4.5 kHz intended to equalise for a corresponding off-axis peak in the head response.

I'm really struggling here because I want these to perform as intended so If there is a way to match the kubes hf eq thru the speaker cable I would be good to go.
Back to top
View user's profile Send private message
speakerguru
VIP Contributor 750+


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

PostPosted: Fri Mar 27, 2015 11:01 pm    Post subject: Re: kube without tape loop Reply with quote

steve59 wrote:
.... so If there is a way to match the kubes hf eq thru the speaker cable ...
I have no idea what you mean by this. Do you have any electrical or electronics knowledge?
The hf eq is a fixed frequency, fixed Q, variable cut-boost active filter. I can dig out the S-domain transfer function if that's any use to you. In case you didn't realise, the full Kube circuit is here http://www.hifiloudspeakers.info/Anatomy/KEFDocuments/KUBE1072_schem.pdf
Back to top
View user's profile Send private message
proffski
Über Contributor 1000+


Joined: 22 Aug 2003
Posts: 1296
Location: Tewkesbury UK

PostPosted: Fri Mar 27, 2015 11:12 pm    Post subject: Re: kube without tape loop Reply with quote

Are you implying that you are somehow attempting to drive the Kube from the loudspeaker output terminals?!? Shocked
_________________
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
Back to top
View user's profile Send private message Send e-mail
SaSi
Senior Contributor 200+


Joined: 24 Aug 2008
Posts: 223

PostPosted: Sat Mar 28, 2015 10:56 am    Post subject: Reply with quote

If I understand the scenario correctly, he is bi-amping the loudspeakers and using KUBE only for the low frequency section. The heads seem to be driven directly from another amplifier, which I think is incorrect.

BTW, is it possible to bi-amp the 107/2?

I would also recommend a reading of this thread
http://www.diyaudio.com/forums/multi-way/99056-crossover-instead-kube-kef-2.html
where the 107/2 crossover and KUBE function is discussed, with input from Andrew Jones as well.
Back to top
View user's profile Send private message
speakerguru
VIP Contributor 750+


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

PostPosted: Sun Mar 29, 2015 9:29 am    Post subject: Reply with quote

SaSi wrote:
... is it possible to bi-amp the 107/2?....

with 2 Kubes?
Back to top
View user's profile Send private message
SaSi
Senior Contributor 200+


Joined: 24 Aug 2008
Posts: 223

PostPosted: Sun Mar 29, 2015 7:50 pm    Post subject: Reply with quote

speakerguru wrote:
SaSi wrote:
... is it possible to bi-amp the 107/2?....

with 2 Kubes?

With one only.
BTW, I've seen the back of the 107 and they only have a single pair of binding posts. Do the 107/2 come with a pair of sorts?
Back to top
View user's profile Send private message
steve59
Junior Contributor 10+


Joined: 14 Mar 2015
Posts: 17
Location: chicago il

PostPosted: Mon Mar 30, 2015 1:03 am    Post subject: Reply with quote

yes there's a pair of binding posts for both the bass and head unit next to each other on the base, my integrated unit hasn't got a tape loop or pre in so i'm driving the head units by running speaker wire from the integrated to the upper pair of binding posts. the pre outs then go to the kube then my bass amp then wired to the lower pair of binding posts.
my electronic understanding is limited and i'm asking specifically what the kube does to the mid/hi frequency and if the same results could be done passively? if it's as simple as turning the tone control on the integrated down a db.
Back to top
View user's profile Send private message
speakerguru
VIP Contributor 750+


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

PostPosted: Mon Mar 30, 2015 8:26 am    Post subject: Reply with quote

steve59 wrote:
....and i'm asking specifically what the kube does to the mid/hi frequency...

I have already explained this in both of my posts in this thread.
steve59 wrote:
.... and if the same results could be done passively?...if it's as simple as turning the tone control on the integrated down a db.

It is possible to make a fixed cut with a passive circuit. A passive boost would result in a much reduced input impedance.
A variable cut-boost passive circuit would not be practical.
A fixed Q, cut/boost at 4.5 kHz is nothing like the shelving effect of a typical tone control.
Back to top
View user's profile Send private message
steve59
Junior Contributor 10+


Joined: 14 Mar 2015
Posts: 17
Location: chicago il

PostPosted: Mon Mar 30, 2015 5:27 pm    Post subject: Reply with quote

The HF eq is a fixed Q, variable depth notch at 4.5 kHz intended to equalise for a corresponding off-axis peak in the head response.
thanks for your patience while I try and work thru this, It makes sense kef would have just added a resistor to the internal xover if it were so simple. At this point, with my gear I don't think the 107/2 benefits from the second pair of binding posts at least not for bi-amping. the best sound I have been able to get is using a single amp driving both pair thru the kube.
Back to top
View user's profile Send private message
SaSi
Senior Contributor 200+


Joined: 24 Aug 2008
Posts: 223

PostPosted: Mon Mar 30, 2015 6:33 pm    Post subject: Reply with quote

steve59 wrote:
yes there's a pair of binding posts for both the bass and head unit next to each other on the base, my integrated unit hasn't got a tape loop or pre in so i'm driving the head units by running speaker wire from the integrated to the upper pair of binding posts. the pre outs then go to the kube then my bass amp then wired to the lower pair of binding posts.
my electronic understanding is limited and i'm asking specifically what the kube does to the mid/hi frequency and if the same results could be done passively? if it's as simple as turning the tone control on the integrated down a db.
You're doing this in the wrong way.
You should be having the source before the kube and both power amps after the kube.
So, by driving them this way, you have the mid/hi section not being equalized by the kube, hence, the overall frequency response isn't the designed one.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    SpeakerTalk Forum Index -> KEF speakers All times are GMT + 1 Hour
Goto page 1, 2  Next
Page 1 of 2

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group