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4-way with Kef B139 TL
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Andy_G
Introductory Contributor


Joined: 05 Jan 2006
Posts: 4
Location: Newcastle, Australia

PostPosted: Thu Jan 05, 2006 7:13 am    Post subject: 4-way with Kef B139 TL Reply with quote

I am looking at doing the 4-way using the old Kef B139, Vifa C13, Kef T15 and Foster ribbon. I got the Kef's for nothing, the Vifa at a sellout and the Foster ribbon was acquired cheaply because I felt the Kef T15 didn't have much top end. (is actually a 35mm dome with Fs=500, which explains the problem)

Note the shape of the Vifa C13 is very similar to the old Kef B110

I've link to a prelim sketch. The reason for the height of the tweeter is that these are aimed as being my main HT speakers, and 1050cm is the mid height of my screen.
(the second hand nature of the drivers will make them near impossible to sell, so I may as well design them for a specific duty for myself.)

This is a prelim sketch only, so if there are any comments that might help,... thanks

I have also linked to a speculative 4-way series x-o layout which might interest some of you.

http://users.tpg.com.au/users/gradds/Revised%204-way.jpg

http://users.tpg.com.au/users/gradds/3+1%20series%20x-o.jpg

Any comments , suggestions welcome.
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harry h
Junior Contributor 20+


Joined: 15 Oct 2004
Posts: 24
Location: Kapiti coast. New Zealand

PostPosted: Thu Jan 05, 2006 9:34 am    Post subject: Reply with quote

Hi Andy, welcome.
I know your still in the prelim stage of your design,but I cant help thinking it may be better to mount the B139 at the top of the t-line so as to intergrate better with the mid and highs,(eliminate lobing) plus this will allow you to get an extra fold in your line thus keeping the port at the bottom and allso achieving a line length of 2.75m.
cheers
Harry
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boyzo
Intermediate Contributor 25+


Joined: 10 May 2003
Posts: 44

PostPosted: Sat Jan 07, 2006 10:14 pm    Post subject: Re: 4-way with Kef B139 TL Reply with quote

Looks complex and a lot ot cabinet work not worth the effort IMHO

I would build a large vented enclosure for the B139, and build a sub enclosure for the mid/treble/supertreble to sit on top you could use an active filter to bi-amp the woofer to the passive mid enclosure or just go all passive.

Transmission lines are pretty dubious the theory sounds good but in practice they offer nothing over a well designed box vented or sealed, almost no one uses transmission lines commercially for many reasons.

At the end of the day (Read Richard Smalls papers) efficiency = F3 and cabinet volume transmission lines don't offer any advantage.
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Andy_G
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Joined: 05 Jan 2006
Posts: 4
Location: Newcastle, Australia

PostPosted: Sat Jan 07, 2006 11:27 pm    Post subject: Re: 4-way with Kef B139 TL Reply with quote

boyzo wrote:
but in practice they offer nothing over a well designed box vented or sealed, almost no one uses transmission lines commercially for many reasons.


Transmissions line do have a different sound to them than vented, and can be shown to act different, particularly in terms of low end. The only reason commercial speakers don't use them often is because they have to make commercial decisions, ie they will always choose the cheapest method of construction. Some of the more expensive speakers on the market are actually TL designs.. eg Nautilus.

As for being a difficult construction, its actually very easy, hardest bit is cutting the flush mount for the mid and tweeters. I spent 2 hours yesterday, and the two bass cabs are completed except for one panel, left off for access.

What I consider a waste of time is rectangular box vented or sealed cabinets!!!

I have made the TL cabs rectangular as a concession to the second hand nature of the drivers used, and that shape is what "fits" physically and aesthetically where they will end up.
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boyzo
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Joined: 10 May 2003
Posts: 44

PostPosted: Sun Jan 08, 2006 1:50 am    Post subject: Re: 4-way with Kef B139 TL Reply with quote

Good luck mate Sad
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boyzo
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PostPosted: Sun Jan 08, 2006 1:54 am    Post subject: Re: 4-way with Kef B139 TL Reply with quote

TL theory is ok only problem is everyone folds them
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Andy_G
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Joined: 05 Jan 2006
Posts: 4
Location: Newcastle, Australia

PostPosted: Sun Jan 08, 2006 2:00 am    Post subject: Reply with quote

The fold is necessary in this case. I have done several TL's and vented using the same drivers, and in each case the TL was an obvious winner, to my ears. There is a smoothness to the bass that you just don't get with vented boxes.
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boyzo
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Joined: 10 May 2003
Posts: 44

PostPosted: Sun Jan 08, 2006 2:02 am    Post subject: Nautilus B&W Reply with quote

Bears no relationship as to what you are trying to do
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boyzo
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Joined: 10 May 2003
Posts: 44

PostPosted: Sun Jan 08, 2006 2:06 am    Post subject: Ok TL are dreadful Reply with quote

The bass rumbles and also gives a false sense of power from the line harmonics

Andy_G wrote:
The fold is necessary in this case. I have done several TL's and vented using the same drivers, and in each case the TL was an obvious winner, to my ears. There is a smoothness to the bass that you just don't get with vented boxes.
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Andy_G
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Joined: 05 Jan 2006
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Location: Newcastle, Australia

PostPosted: Sun Jan 08, 2006 2:25 am    Post subject: Reply with quote

Well, obviously a pretty negative and ignorant place to visit..

Bye !!!
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harry h
Junior Contributor 20+


Joined: 15 Oct 2004
Posts: 24
Location: Kapiti coast. New Zealand

PostPosted: Sun Jan 08, 2006 5:58 am    Post subject: Reply with quote

Andy_G wrote:
Well, obviously a pretty negative and ignorant place to visit..

Bye !!!



Dont take one mans opinion as gospel or the general concensus here Andy.
I for one love t-lines and agree with all you have said regarding their sound.
Maybe Boyso has nver heard a good one, or doesn't have the skills to build them, either way the're his opinions and if we all thought the same, we would all drive Lada's. Razz

cheers
Harry
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proffski
Über Contributor 1000+


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

PostPosted: Sun Jan 08, 2006 2:21 pm    Post subject: Reply with quote

I love the sound of TLs. Most manufacturers as has been said already are not willing to pay the extra expense of manufacture.

Very few reflex enclosures are designed correctly, ATC and Spendor seem to be on the ball as also a couple of others.

The longest (IT DOES WORK!) TL I have built is almost half wavelength, it took a lot of time to get it right but partnered with a B110B and Decca Ribbon the results were worth it!

I found that TLs load rooms better and the only negative point is the reduced efficiency.

Manufacturers like PMC http://www.pmcloudspeaker.com/ make some superlative TL monitors.

Anyway, this is a magnificent site and the main purpose is to the paying of homage to KEF loudspeakers of yore and learning in the process.
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boyzo
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Joined: 10 May 2003
Posts: 44

PostPosted: Mon Jan 09, 2006 12:02 am    Post subject: Reply with quote

I have listened to the MK2 bailey transmission line built by various people and they all sound awfull .... the bass is rumbly resonant false.

Problem with TL's is underdamped = resonant .... overdamped = no bass
this is because they are always folded.

A 1/2 wavelength TL straight is Ok but who would build such an ugly thing for likes of a B139

I would NEVER drive a Lada no only the next worst thing on the Planet the
RANGE ROVER Wink

harry h wrote:
Andy_G wrote:
Well, obviously a pretty negative and ignorant place to visit..

Bye !!!



Dont take one mans opinion as gospel or the general concensus here Andy.
I for one love t-lines and agree with all you have said regarding their sound.
Maybe Boyso has nver heard a good one, or doesn't have the skills to build them, either way the're his opinions and if we all thought the same, we would all drive Lada's. Razz

cheers
Harry
Laughing Laughing Laughing
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boyzo
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Joined: 10 May 2003
Posts: 44

PostPosted: Mon Jan 09, 2006 12:18 am    Post subject: Reply with quote

Oops

TL's seem to be some sort of audio nirvana and indeed the theory suggests NO reflections in the midrange, in terms of bass any vented box just beats it hollow easy to design too.

What is interesting is there is no modelling software for a TL but for sealed or vented enclosures, plenty of modelling software around and predictable to 1dB all from Thiele and Small's research.

Go ahead and build your TL ... I just think they are not worth the effort at all.

btw you could do no worse than build the ETI TL (early 80's) a bit of an ugly monster tho'




Andy_G wrote:
Well, obviously a pretty negative and ignorant place to visit..

Bye !!!
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proffski
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Joined: 22 Aug 2003
Posts: 1296
Location: Tewkesbury UK

PostPosted: Mon Jan 09, 2006 12:39 am    Post subject: Reply with quote

The line IS critically damped, consisting of Doc Baileys specified long hair wool, sculpted anechoic grade foam and BAF.
It took many days and frayed tempers to get it right, and so it is!
Yes it is a stretched Bailey design, with accoutrements.
All folds are gently contoured with plaster of Paris mixed with PVA.
There are a few Hermoltz Resonator designs that come close.

Till recently the whole lot was tri-amped with lovely 1970s Naim gear.

Sealed box yes, but you must find the ideal driver first.
The ones with the ideal Thiele Small parameters are expensive.

What a lovely hobby it is and I shall never tire of building, experimenting and above all listening to music…
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