Kef R300 playground - measurements of raw drivers

[Zvu]

Es sieht ziemlich idiosynkratisch aus, wie John Atkinson sagen würde. Aber ich denke es muss sein, wenn die Form der Funktion folgt

Hast du jeder akustische Messungen ? Wenn Sie wunsch, können Sie hier posten.

Viele Grüße,
Mladen

[Zvu]

Einer noch, mit besserer? frequenzweiche.

[ATTACH=CONFIG]46439[/ATTACH]

Messungen im Haus, so etwas lausig. Es ist noch ein bisschen warm auf 8KHz. Ich möchte Kerbfilter vermeiden auf 8 KHz, wenn ich kann. Wir werden sehen.

Der einzige differenz in der Frequenzweiche ist 2 Ohm Serienwiderstand am Hochtöner, nicht 0,5 Ohm.

[chro]

Ja das ist wohl ziemlich Eigentümlich


abgespeicherte Messungen habe ich derzeit nur im Raum, am Hörplatz:built:
[ATTACH=CONFIG]46083[/ATTACH]

[Jesse]

Zum Tieftöner fahre ich aktiv.

[ATTACH=CONFIG]46026[/ATTACH]

Hallo,
sieht sehr edel aus. Diesen Koax find ich sehr spannend. Verätst du uns wo du das Chassis her hast?

[Zvu]

@Chro:

Es sieht super. Es ist überraschend, was heute mit der richtigen Software möglich ist.

Herzliche Glückwünsche zu einem gut ausgeführten Projekt :prost:

Viele Grüße,
Mladen

[Zvu]

Hier sind mehr Fotos von den Innenseiten von lautsprecher.

Das ist sogenannte "constrained layer" dämpfung by Kef. Überhaupt nicht viel.


https://i.postimg.cc/vBSfVnwW/DSC-0029.jpg


Hier sind Anschlüsse und Bassport.


https://i.postimg.cc/rwC493Ly/DSC-0036.jpg


https://i.postimg.cc/mkzMNrTK/DSC-0034.jpg


https://i.postimg.cc/43s6kZ1h/DSC-0035.jpg


Hier ist das Highlight des Lautsprechers, ein kleiner konzentrischer Treiber. Vielleicht nicht die besten Bilder, aber man kann leicht einige der Designmerkmale erkennen.


https://i.postimg.cc/t40dkFZk/DSC-0033.jpg


https://i.postimg.cc/VkjqV5X8/DSC-0030.jpg


https://i.postimg.cc/76BMnc0J/DSC-0032.jpg

Oh, und der Grill sieht auch ganz nett. Es ist gemacht aus MDF mit kleinen Nd-Magneten an den Ecken. Cool


https://i.postimg.cc/C5qBn6Ng/DSC-0037.jpg


https://i.postimg.cc/RF8JFzwd/DSC-0038.jpg

Ich mag glänzendes Kef-Zeichen auf der Rückseite. Normalerweise ist es nur schwarz, also ist es schön dass jemand daran gedacht hat. Ich werde etwas bituminöse Beschichtung auf die Außenseite der Mitteltöner kammer auftragen und die gehäuse zum lackieren schicken.

Viele Grüße

[chro]

Hallo,
sieht sehr edel aus. Diesen Koax find ich sehr spannend. Verätst du uns wo du das Chassis her hast?

Servus Jesse,

ich hatte ja eigentlich meine Manger mit den PHL B4021, und war auch super zufrieden. Als ich bei Ebay mal etwas gestöbert habe, hatte jemand die Koaxe für 140€ inklusive Versand (Paarpreis) drin Da konnte ich nicht nein sagen. Und als ich die Koaxe getestet habe, gefielen sie mir auch noch besser (Sind halt nicht so Laserbeams, wie die Manger) :prost:

BG Timo

[Jesse]

Hallo Timo,
na Top, da muss man ja zuschlagen. :ok:

Dann noch viel Spaß damit.

[Zvu]

Es tut mir leid, aber ich muss diesmal auf Englisch schreiben. Es ist jetzt auf Deutsch zu kompliziert für mich.

It's been a while since i've addressed the sound of modified Kef R300.

When the initial impressions of sound settle, then comes that long lasting feeling you get when you get to know your loudspeakers very well. Kef did an amazing job with these drivers, well almost. Almost everything sounded the best ever but i will not write about qualities of this loudspeaker but more on the weak spots. R300 when modified has two of them. Low bass - it's there but not really. In my room it worked perfectly but when put in larger rooms 40sqm or more, it needs help - and i'm talking about hard walls, not wood or drywall - i'm guessing it would behave worse in that situation. Other one being low mids. Concentric at the top does such a good job that i wonder what could sound better than that. When Kef says -obsessed with high resolution- they really mean it. It's one of the finest midranges and tweeters i have ever heard, and i've heard quite a few loudspeakers. Woofer is crossed at about 450Hz to midrange, and there problems begin. I'll post a picture оf its construction first:


[ATTACH=CONFIG]48381[/ATTACH]

It's made by attaching large aluminium plate to a paper cone that is connected to voice coil former. In the paper cone there are elliptical openings to let the pressure out. Something similar can be seen in typical car subwoofer units. When it comes to bass frequencies boy does it deliver. It is one of the most punchy bass drivers i've laid my eyes (ears???) on. It would be almost no compromise loudspeaker if midrange could be crossed to it at say 120-150Hz but pushing it to 400-500Hz has taken its toll. Since i made quasi-anechoic measurements with almost 11ms gate time, i get very good resolution from about 90-100Hz. I've made the flattest measuring loudspeaker (on and off axis) up to about 2KHz i've seen. But something was missing. i first thought that midrange was a bit quieter than it should be so i reduced the attenuation in 0.2dB increments to set its level by ear. That's wasn't it. Then, after some time i started to look at the crossover frequency between midrange and woofer. With few slight adjustments i moved it to 380Hz - it was better. Then i moved it to 310Hz, even better still. All the time i kept linearity and good phase tracking. The more i let the midrange work, the better the rendering of that thing missing was. Then i just played some music i know well and got really close to loudspeaker listening to midrange and woofer up and down. Every tone that wasn't pure bass frequency (say 80Hz and up) it played virtually the same. Every note sounded the same. They've made it work well and deep enough at low frequencies but they've damaged the transients of lower midrange on the way. I guess the price had to be payed somewhere and it was right there where it hurts the most. That couple hundreds hertz it should be playing it doesn't do well.

Knowing that, there were couple of options. To buy used Q300 and use its 6.5" woofer. I'd remove the tweeter and make a phase plug. But that's an investment of more or less 300-400 euros and leaves me with having to measure new trim rings dimensions and have them made out of plastic or aluminium, new crossover etc. Color of Q300 woofer looks really ugly when combined to concentric midrange in R300 so i gave up. Next thing would be trying to find a 4 ohm woofer that will work as well as factory one in about 15 liters of volume. That was cheaper option but i haven't found it.

Anyhow, i'd strongly recommend concentric driver from R series as it really sings but to use it with another woofer that will not absorb transients on the way. If you're listening electronic music, you'll never want for another loudspeaker. Couple of my friends does so i sold my R300's to one of them.

This was a very good experience. I've learned a lot and it showed me that Kef is a force to be reckoned with when concerning their concentric drivers.

Viele Grüße

[roomcurve]

Very interesting reading, thank you, also interesting that KEF kept the high crossover frequency of 400 Hz for their successor series:
http://nl.kef.com/media/doc/r2018_whitepaper_en.pdf

[mtthsmyr]

Hi Zvu,

Do you have off-axis measurements of your flat-to-2kHz-Voicing? I have found this measurement of the R300:

https://www.soundandvision.com/content/k...s-measures

I would expect the original KEF voicing to yield a straight declining power response and a similar behavior at 20..30° hor off axis. Which appears sensible to me. Also, the LS50 speakers that I have seen and heard demoed at audio shows were always placed parallel (not toed in) which seems to validate this point.
If my suspicion about the off-axis behavior is correct, that would also explain why you felt the midrange to be recessed because that hump is actually needed for a balanced response. Also the limited baffle-step-compensation.

... damaged the transients of lower midrange...

I had a similar experience in the flight speakers, but in that case it was not the woofers deficiancy but could be traced back to room interaction (floor bounce). Changing the crossover point had a significant impact on power response and room interaction. In my case, the effect was maximized around 380 Hz. Crossing over at 300 Hz made it disappear, as did crossing beyond 500 Hz. It still could be a property of the woofer, as you say, but I wouldn't rule out other influences. I find this frequency range very challending to deal with.

Viele Grüße, Matthias

P.S.: did you get the PM over on htguide?

[Zvu]

@Roomcurve:

They've seem to keep the woofer construction as well so the stuff i'm talking about could and should be test listened before purchase.

@Mtthsmyr:

I have simulated response but it matches measurements i made outside (disregarding tweeter response which for some reason turned out to be 2dB hotter on axis which may have been influence of temperature outside on the tweeter itself).

Here's my sim - high resolution on axis and 45 deg off axis:

[ATTACH=CONFIG]48383[/ATTACH][ATTACH=CONFIG]48382[/ATTACH]

My opinion is that they've tailored the response to make impression on first listening session. There are measurements of R3 (equivalent of R300) that are pretty flat and are very similar with what i have done with my R300. The topology of the crossover given in their R series whitepaper is virtually the same as in R300 but with the right values they've made it measure flat. The hump in R300 comes from woofer, not midrange. Mid is pretty flat. Recessed midrange was felt in nearfield also - listening at 0.5m makes off axis behavior much less important. Nearfield revealed to me that the woofer is the problem.

Since i enjoyed R300 sound so much, if we disregard woofer, i've bought LS50 and it is soon to get the same treatment as R300 did. But it'll get one or two woofers covering frequencies <120Hz.

I did get the PM and i'm still pondering on where i am right now and where i want to be. Thanks for providing peronal perspective