Kef 105/3 Meta

[phantomrad]

Could really do with some help, I have a set of Kef 105/3 in mint condition and a spare set that have faulty UniQ speakers, I can use these to test my idea before implementing it into the good ones
Idea - I have a set of Kef LS50 Meta that I don't use, would I be able to do a straight swap with the Meta speakers and the original 105 UniQ?
Fitting is not an issue as I can CNC a new complete front panel or make a spacer to fit the speaker.
Both speakers are 4ohm both speakers are wired in the same way with about the same RMS power output but would I have to change anything on the crossover, and if so what would I need to look at changing?
Any help with this would be much appreciated.

 

[Allison3]

https://media.tenor.com/WRnTA1QNBHsAAAAM/the-office-steve-carell.gif

 

[SaSi]

I doubt anybody has considered doing this so it's a stretch to expect guidance, especially with the crossover.
However, I would indeed try that, using a spacer to mount the driver, connect it and test it. You may be pleasantly surprised.
Regarding possible crossover modifications required, it's possible. As the LS50 are two way speakers, a high pass for the mid base driver would not be present. On the 105.3, there are the woofers to take care of the base frequencies so the existing crossover would feed the low frequencies to the woofers and higher frequencies (IIRC from 300Hz and above) to the mid/woofer and the high frequencies to the tweeter. So, the 105.3 existing x-over may well take care of things.

 

[phantomrad]

I doubt anybody has considered doing this so it's a stretch to expect guidance, especially with the crossover.
However, I would indeed try that, using a spacer to mount the driver, connect it and test it. You may be pleasantly surprised.
Regarding possible crossover modifications required, it's possible. As the LS50 are two way speakers, a high pass for the mid base driver would not be present. On the 105.3, there are the woofers to take care of the base frequencies so the existing crossover would feed the low frequencies to the woofers and higher frequencies (IIRC from 300Hz and above) to the mid/woofer and the high frequencies to the tweeter. So, the 105.3 existing x-over may well take care of things.

Cheers for that, I had the same thoughts when it came to the crossover working. Will give it a go and see what happens, may try my old Ls50s first in the old 105s and then give the Metas ago.
fingers crossed.
Will update as I go along.

 

[BmWr75]

Not having to make some crossover changes would be a miracle.

 

[SaSi]

Worst case scenario:
The low pass section of the 105.3 loudspeaker needs to remain in place to separate the woofers.
The band-pass and high pass need to be disconnected.
The x-over of the LS50 is used after the low pass section, to separate the mid-woofer and the tweeter.

The original 105 uses an arrangement like that. There is a low pass crossover in the main cabinet, feeding the woofer and the pods. In the pods there is a two way crossover for the midrange and tweeter.

 

[phantomrad]

Worst case scenario:
The low pass section of the 105.3 loudspeaker needs to remain in place to separate the woofers.
The band-pass and high pass need to be disconnected.
The x-over of the LS50 is used after the low pass section, to separate the mid-woofer and the tweeter.

The original 105 uses an arrangement like that. There is a low pass crossover in the main cabinet, feeding the woofer and the pods. In the pods there is a two way crossover for the midrange and tweeter.

So in your opinion the original crossover should work. From recapping the x-overs I realised that the Low and the mid/high were separate boards which gave me the idea, I new the back of the LS50 speaker was wired the same way as the 105s, so I wondered if they would work.
The LS50 are rated at 8ohm but the speakers individually are 4ohm, wouldn't using the LS50 x-over change the overall ohm of the speakers? 6 ohm I think? With the low x-over(105) being 4ohm and the LS50 x-over being 8ohm.
If I completely wrong please be gentle.

 

[daybreak2350]

Sounds like fun, so Just do it ~ that is, trial and error . . . or miracle. Type of music is a factor but the truth is in the listening. Please let us AK'ers know your results!

• If the existing configuration is disastrous then no doubt we can provide more technical speculation on what you should do. Enclosure dimensions, electrical schematics, component specs, signal generator sine wave scope images, oxygen-free monster cables, listening room environment, climatic conditions--why I'll bet we could even run it through a few algorithms to see what AI has to say; it's smarter than us, ya know...
• Send pics, too.

 

[SaSi]

I didn't pay attention to the 105.3 being a 4 ohm loudspeaker.
The LS50 are 8 ohms nominal impedance, with a minimum of 3.
The 105.3 is using a conjugate load x-over that presents a constant 4 ohm resistive load to the amplifier.
In general you don't mix 4 and 8 ohm drivers in the same system as it generates an uneven distribution of load and output.
You need to listen to the results and decide for yourself. It may be that the result will be "bass heavy" if a lot of power is driven to the 4 Ohm woofer section compared to the nominal 8 Ohm mid/high section.

There are no hard rules here - listening will give you the truth.

As an example, I wanted a custom sized good quality loudspeaker pair to place to the sides of my TV. The bookshelf spacing dictated the dimensions. I had to have very narrow front baffle but wanted a "full range" loudspeaker that would provide plenty of low frequencies.
I worked with drivers that I had in my collection, and that included a B139 A6171 racetrack woofer that would not fit to the front baffle, so it was mounted to the inner sides towards the back. I also had plenty of B110, 24Ohm versions. The Concerto is an 8 Ohm system so I used 3 of them each in parallel. I also had a concerto x-over that was my starting point. It works fine.

I also built a system based on the R107 having the original crossovers and pods. Not the cabinets or original woofers.
I worked out the internal dimensions of the bass unit by measuring, guessing and asking and tried several woofers I had. Found that the B200 SP1014 performed well. That whole project was - by definition - a true path to disaster. Well, the result sent my R105 to living room duty and the custom design has been in my main system since 2012 or so and I no longer lust for finding/building better loudspeakers. They sound just fabulous.