Should I embark on this ambitious project based on KEF drivers?

Hello everyone,

The conjuncture and poor built of vintage KEF cabinets lead me to owning quite a few KEF drivers:
- 2 pairs of T27 SP1032 tweeters (one matched)
- 1 pair of B110 SP1003 mid-woofers
- 1 pair of B200 SP1039 mid-woofers
- 2 pairs of B139 SP1044 woofers
- 1 pair of B139 SP1042 passive radiators

Basically these represent the drivers pulled out of a pair of KEF 104 Reference and a pair of KEF Concerto speakers. Also I have the related crossovers.

My question is: do you think it would be worthy to build a 4 way speaker, based on the design of the Acoustic Research AR-9's?

I plan to use one pair of T27 SP1032 tweeters for highs, the B110 SP1003 for the upper mid range, the B200 SP1039 for the lower mid range and one pair of B139 SP1044 along with the passive radiators B139 SP1042 for bass (so the impedance will be 8ohms). The bass units will be positioned on the sides of the speaker box similar to the design of the AR-9's.

Crossover points will be at 400Hz, 1000Hz and 3500Hz.

Regarding the speaker size, positioning of drivers on baffle and crossover design, a specialized company will be seeked as I do not own the technical equipment, nor the knowledge.

So, what do you think?

Thanks in advance
 

Attachments

  • WP_20170511_21_02_06_Pro.jpg
    WP_20170511_21_02_06_Pro.jpg
    46.3 KB · Views: 63
Well, you certainly have cornered the market of vintage KEF drivers. :)

Having owned (and sold) several pairs of Concertos, and a bunch of KEF drivers from stripped speakers, I'm really at a loss as to what the fuss was about with their offerings, but many people love KEF speakers.

You will surely have a project on your hands, but if you have the time, money and patience to see it through, it would make a great thread and a good story on AK. A bit "Grand Designs" like.
 
Well, you certainly have cornered the market of vintage KEF drivers. :)

Having owned (and sold) several pairs of Concertos, and a bunch of KEF drivers from stripped speakers, I'm really at a loss as to what the fuss was about with their offerings, but many people love KEF speakers.

You will surely have a project on your hands, but if you have the time, money and patience to see it through, it would make a great thread and a good story on AK. A bit "Grand Designs" like.

Yes I did, unwillingly:))

My problem is that basicaly these drivers are old and don't know if sound wise are worth it. I mean I liked the sound of the 104's but I wasn't blown away....

The whole project will set me back a few hundreds so, I would like to choose wisely....

Thank you for your thoughts.
 
I have the concerto but use the upgraded crossover from Falcon Acoustics. They are truly exceptional now! I would love to try a transmission line enclosure in the future.
 
Understood. I thought you knew a similar built. I've seen theTL IMF projects....wanted to do something different and maybe use all my drivers :))
Keep in mind the only way you'll realize the benefit of doubling the drivers is if you also double cab volume. Putting twice the drivers in a cab adequate for one won't help you. Especially the bottom end as that would just raise the -3db point. It would be +3db more efficient but it wouldn't go as low.
 
If I were you, I would simply build a KEF Constructor Series CS5 and CS7 kit, you have the drivers to do it. Actually, the drivers you have would be more suitable for making a clone of a 104aB since you have the square chassis woofers instead of the triangular ones for the CS5.

If you are looking for more ambitious projects maybe a transmission line design as others have suggested. Or using the two pairs of B139s in isobaric configuration like the Linn Isobarik.

Lee.
 
Keep in mind the only way you'll realize the benefit of doubling the drivers is if you also double cab volume. Putting twice the drivers in a cab adequate for one won't help you. Especially the bottom end as that would just raise the -3db point. It would be +3db more efficient but it wouldn't go as low.

I've thought about the volume needed for the bass drivers, based on the specification sheets, and in turns out that in this configuration SP1044 + SP1042 (basicaly, as I understood, when using a passive driver the volume is calculated for the active one as for a bass reflex enclosure) I need a box of minimum 60l and I can go up to a maximum of 140l. I was thinking to use a 120l one. The other drivers will have their own enclosures as it follows: the B200 SP1039 needs 20-25l, the B119 SP1003 needs 5-10l and will share the same enclosure with the tweeter. The problem is that at these dimensions I will end up with a enormous box....
 
If I were you, I would simply build a KEF Constructor Series CS5 and CS7 kit, you have the drivers to do it. Actually, the drivers you have would be more suitable for making a clone of a 104aB since you have the square chassis woofers instead of the triangular ones for the CS5.

If you are looking for more ambitious projects maybe a transmission line design as others have suggested. Or using the two pairs of B139s in isobaric configuration like the Linn Isobarik.

Lee.

Actually, some of the drivers come from a 104 speaker set, so I see no point in doing that.... I would like to build something never atempted.... Those Isobariks sure look nice....
 
I've thought about the volume needed for the bass drivers, based on the specification sheets, and in turns out that in this configuration SP1044 + SP1042 (basicaly, as I understood, when using a passive driver the volume is calculated for the active one as for a bass reflex enclosure) I need a box of minimum 60l and I can go up to a maximum of 140l. I was thinking to use a 120l one. The other drivers will have their own enclosures as it follows: the B200 SP1039 needs 20-25l, the B119 SP1003 needs 5-10l and will share the same enclosure with the tweeter. The problem is that at these dimensions I will end up with a enormous box....
Isobaric would be the way to realize a performance increase by multiple drivers without the real estate.
 
The deal with Isobaric is that given the optimal volume, in your application, for
one woofer, if you have room for twice that do not use Isobaric, rather put them
both driving into the room.
If, on the other hand, you need to reduce the volume to about 1/2 the optimal
size then put them in an Isobaric configuration. I have always viewed this as
a much less than optimal way to go. Power is wasted simply to provide for a
smaller box and there is no increase in the maximum SPL.
 
The deal with Isobaric is that given the optimal volume, in your application, for
one woofer, if you have room for twice that do not use Isobaric, rather put them
both driving into the room.
If, on the other hand, you need to reduce the volume to about 1/2 the optimal
size then put them in an Isobaric configuration. I have always viewed this as
a much less than optimal way to go. Power is wasted simply to provide for a
smaller box and there is no increase in the maximum SPL.
But...there is an increase in overall performance; elimination of even order harmonics and better definition/transient performance. The question is whether it's significant enough to matter.
 
The deal with Isobaric is that given the optimal volume, in your application, for
one woofer, if you have room for twice that do not use Isobaric, rather put them
both driving into the room.
If, on the other hand, you need to reduce the volume to about 1/2 the optimal
size then put them in an Isobaric configuration. I have always viewed this as
a much less than optimal way to go. Power is wasted simply to provide for a
smaller box and there is no increase in the maximum SPL.

Thank you for your input. Space/size wouldn't be a constraint...but power needed to amplify them would, so, I think I will take lean towards a traditional design.
 
Isobaric requires 2 ACTIVE woofers per cabinet, not one active and one passive driver, so an Isobaric would only work as a central subwoofer using the two B139 SP1044's. Otherwise, you could consider two cabinets with one active/passive drivers in a subwoofer configuration - side by side or one above the other in a tall slim deep cabinet. Run those from 30-70 or 80 hz. Otherwise, run the central subwoofer isobaric and from 25-70hz. with an active crossover and amp.

I would then suggest you consider building a midbass cabinet (sealed or ported, maybe even a simple TL) for the B200 and restrict it to 70-150 or 180hz. A fairly simple low pass crossover would be a good start. Look at the Rogers AB1 as an example, but scaled up for the B200.

Build a nice LS3/5a clone with the Falcon LS3/5a crossover and the B110/T27 combo, and build the cabinet to LS3/5a specs or slightly deeper.

I have LS3/5a baffles and grilles if you need them but I'm in USA, I see you're in Eastern Europe so probably easier to get them from the UK. There are LS3/5a cabinets available from Moldavia on Ebay so that's probably a lot easier for you. You should order the Falcon front panels (if needed), grilles, T27 grilles, felt, interior acoustic foam, crossover felt pads, hardware (bolts, nuts), B110 plastic channel insulator strips, and front baffle gaskets from Falcon. You will still need the bitumen sheets that are glued to the side, top and bottom interior panels that go underneath the acoustic foam. Do not be tempted to add additional polyfil damping material, it is not needed.
 
Isobaric requires 2 ACTIVE woofers per cabinet, not one active and one passive driver, so an Isobaric would only work as a central subwoofer using the two B139 SP1044's. Otherwise, you could consider two cabinets with one active/passive drivers in a subwoofer configuration - side by side or one above the other in a tall slim deep cabinet. Run those from 30-70 or 80 hz. Otherwise, run the central subwoofer isobaric and from 25-70hz. with an active crossover and amp.

I would then suggest you consider building a midbass cabinet (sealed or ported, maybe even a simple TL) for the B200 and restrict it to 70-150 or 180hz. A fairly simple low pass crossover would be a good start. Look at the Rogers AB1 as an example, but scaled up for the B200.

Build a nice LS3/5a clone with the Falcon LS3/5a crossover and the B110/T27 combo, and build the cabinet to LS3/5a specs or slightly deeper.

I have LS3/5a baffles and grilles if you need them but I'm in USA, I see you're in Eastern Europe so probably easier to get them from the UK. There are LS3/5a cabinets available from Moldavia on Ebay so that's probably a lot easier for you. You should order the Falcon front panels (if needed), grilles, T27 grilles, felt, interior acoustic foam, crossover felt pads, hardware (bolts, nuts), B110 plastic channel insulator strips, and front baffle gaskets from Falcon. You will still need the bitumen sheets that are glued to the side, top and bottom interior panels that go underneath the acoustic foam. Do not be tempted to add additional polyfil damping material, it is not needed.

Thank you for your thoughts.

Drivers wouldn't be the probelm, as I have 2 pairs of SP1044 and 1 pair of SP1042. Isobaric sounds and is a little bit complicated for what I'm willing to do and for what I had in mind.

Actualy I have some ramaining baffles from an unfinished project based on the B110/T27 drivers. The layout is similar to the one used in the KEF Cresta MK II's, but mirrored. I think I could also use the crossover from the KEF 104, so the cost will actualy be close to none. I think I will give that a go for starters. I know the Faclon site, the prices are a little bit steep. With what I would pay for a crossover there I could build a hole boxe at a specialized shop here in Romania.....

All the best.
 
Back
Top Bottom