KEF LS50 playground - measurements of raw drivers in factory cabinets and simulations

[Zvu]

I'm posting .txt files that you can convert to .frd or .zma if your simulator needs it. I derived frequency files with about 10ms gate time. I didn't merge it to get low frequency response of woofer (under 120Hz) because i'm not interested in it. In the .zip file that is available for download from my DB account there is another .zip file that can be uploaded to HolmImpulse if you are not satisfied how i extracted sim files so you can do it as you see fit. All measurements are done from about 108cm on axis and approximately 30 degrees off axis. It is not good as 0-180 in 10 degrees increments but if you cross it over between 2000-2800Hz you won't get into trouble. Any fine tuning i recommend to be done by measuring and listening of your drivers.

If there's anything that you want me to do (other than measuring TS for woofers because i'm not doin' it :) ) feel free to ask.

Dropbox - Kef LS50 measurements and sim files.zip - Simplify your life (https://www.dropbox.com/s/zni55ujjo8yzgh9/Kef%20LS50%20measurements%20and%20sim%20files.zip? dl=0)

Measurements done with calibrated Behringer ECM8000, M-audio FastTrack USB, Holmimpulse.

Measurement conditions

https://i.postimg.cc/jwb740fb/IMG-2671.jpg (https://postimg.cc/jwb740fb)
https://i.postimg.cc/B68BsJQX/IMG-2671.jpg


Midwoofer and tweeter

https://i.postimg.cc/7bX20RYF/50-a.png (https://postimg.cc/7bX20RYF)
https://i.postimg.cc/gkbHFF92/50-a.png

https://i.postimg.cc/qgpKtr0c/50.png (https://postimg.cc/qgpKtr0c)
https://i.postimg.cc/1RqrjRjd/50.png


Simulation of Kef's factory crossover: frequency, impedance and phase response

https://i.postimg.cc/dZQZg2nN/LS50.png (https://postimg.cc/dZQZg2nN)
https://i.postimg.cc/yxchgnRK/LS50.png

https://i.postimg.cc/WFwJ9WmJ/LS50.png (https://postimg.cc/WFwJ9WmJ)
https://i.postimg.cc/QtRkdvHS/LS50.png

https://i.postimg.cc/qg2mr4w8/50.png (https://postimg.cc/qg2mr4w8)
https://i.postimg.cc/QNyvpMWn/50.png

Few comments:

In Kef LS50 they've seem to done around 8dB baffle step compensation for midwoofer. That sounds like a lot but surprisingly it doesn't sound that bad at all. I guess that it doesn't go much low so it kinda evens out. Tweeter level is set, as can be seen, a 1.5-2dB higher than midwoofer. Again, i'm surprised that it isn't perceived like overly bright. You can hear it being louder but it doesn't make you want to turn the volume down - quite strange actually, unlike any metal dome i've listened so far. Also, good thing i've prepared and measured both cabinets because there are few measured differences between drivers. You'll see.

[wgh52]

Hello Mladen,

thanks for sharing your interesting work. Looking forward to see more an learn from it. Two questions in the baffle step context:
- Where/How have you been able to see/analyse the 8 dB Baffle Step correction?
- Did you (or would you) do additional measurements to show horizontal/vertical directivity?

I envy you for the environment you have available for doing measurements...

Thanks!

[Zvu]

You're very welcome,

About baffle step. It starts early but kicks in really hard at about 550Hz and peaks +6dB at 850Hz in regard to <200Hz. So, 6dB baffle step compensation aka full BSC would be if 850Hz and everything bellow would be in line with 200Hz. Instead of that 550Hz is 2dB lower and the whole response is tilted downwards untill it hits the beginning of that hump that peaks at 850Hz. So one could say either that there is a dip in response at 550Hz, or that it is 8dB baffle step compensation. It works for me either way but the dip definition would probably be more accurate :) Here's a pic for clarification:

48952

Those numbers are not made up, i put the cursor over the grid and it lines up perfectly. As for measuring room, it is an old volleyball court that is soon to be demolished but it suits my needs perfectly and it is about 20 euros to rent for the night.

[Zvu]

I've been listening for a few days this crossover:


48982


Loudspeaker No.2 has few slight changes in crossover and one significant:


48983


The surround on that midwoofer didn't get enough coating so its resonance is quite visible. I decided to solve it with LC filter. 2x4,7uF in series and 7.5mH/Rdc=12.5ohm. 2.2uF will also work but i ran out of 2.2uF capacitors and i was eager to listen to it. The coil is Jantzen, catalog number 000-1541 and can be bought at HiFiCollective (https://www.hificollective.co.uk/catalog/000-1541-7-500mh-jantzen-air-core-wire-coil.html)for about 3 euros a piece. Its outer diameter is 26mm and it is 15mm high but without it the response looks like this and that was unacceptable:


48984


So, last night i've made some measurements of modified Kef LS50. Bare in mind that this is 1dB grid.


0, 10 and 20 degrees
48985


30, 40 and 50 degrees
48986


60, 70 and 80 degrees
48987


Here i had to make the grid 2dB to be able to see the level of 90 degree against 0 degrees


So 0, 80 and 90 degrees
48988


Tangerine phase plug obviously works like a charm. There will be some tweaking by ear but all in all, i'd say that's it.


And now, traditionally, a little livelier display :)


http://oi68.tinypic.com/qp5q2p.jpg

[wgh52]

Hi Mladen,

congratulations to your successful work and thanks a lot for sharing.

Is there any possibility to show a comparison with the "original" KEF crossover? I actually did not see a "motivation statement" in this thread why you did all this work ;) , despite the results seem to make it worthwhile anyway :prost:. If this is npot possible maybe you share your subjective impressions about the effect of the new cross over?

[Zvu]

Hallo Winfried,

Original Kef's crossovers are still in cabinets, disconnected. I'll see that i measure one of them in near future but i don't expect large differences comparing to what they've measured at SoundStageNetwork:

https://www.soundstagenetwork.com/index.php?option=com_content&view=article&id=941:nrc-measurements-kef-ls50-loudspeakers&catid=77:loudspeaker-measurements&Itemid=153


I think i can do better than Kef - that is my driving engine. Not because i think i'm all that better than guys at Kef but they are limiting themselves by having to tailor the sound to adhere to the majority so they can sell more. That sound doesn't suit me (more on that later). Other that, tolerances are slightly on the larger side. At least for what i'm used to see from drivers from the same batch, or i'm just spoiled by Seas and SB consistency. Not to say they are bad drivers because of it, but i think they need special care to make them shine as they can and deserve.

As for sound of factory LS50, it wasn't all that bad for out of the box loudspeaker. Most of them i find unlistenable on the long run but LS50 did quite well. The sound was too polite? for me. I enjoyed listening to them but i could clearly hear that lower mids are a little bit too smooth. That few dB missing before baffle step hump played their role perfectly. As for tweeter, it is one of the best i've had chance to listen. Strange thing to me was that tweeter, being obviously louder, wasn't harsh on ears, at least to me. I found out yesterday that some guys did found it harsh. I think it could be bad electronics or lousy room placement, i really don't know. I get why people are raving about them. You can listen them for hours without any fatigue, but also without any excitement. I constantly had the urge to push them up to rear wall (or front wall, whatever) and play some irrelevant music for background noise. Quite boring for me actually, I don't need to spend 1200 euros to get that, i can do it much cheaper. Compared to that, sound is now much more vivid, snappy and overhaul more enjoyable for me. Still lacks bass and authority in midbass though :)

Since i still consider R3, R300, Reference 1 etc. the ultimate concept (dualconcentric for mids and highs and dedicated bass bellow) what i did now is the first step toward that. I'm waiting for 4 woofers to arrive from Germany in a few days. I'll make it mtm? with LS50 and cross over at around 150Hz. 150uF in front of LS50 midwoofer and 2mH parallel to it makes it very adjustable and doesn't influence rest of the response too much. I'll try to do it passive but if i fail, i"ll just order a plate amp and be done with it. I still need to make few decisions on how to do it because i don't want to make new cabinets and mount the LS50 coax in it. I intend to use all the great engineering that went in to this cabinet, and make bass boxes modular. Then i can test what works best for me, mtm or tmm.

Hope this cleared things up a little bit :)

Viele Grüße

[wgh52]

Hello Mladen,

thanks for the extensive and interesting insight! This makes following your project even more exciting.

Being a Fan of active speakers since >30 years, I do admire people being able (and not least having the patience) to design and achieve well sounding speakers with passive components :)

I'm looking forward to follow your further progress and wish you the well deserved success!