KEF Kube 10b, what is wrong with my measurement?

[Peerke007]

I just received my new subwoofer (KEF Kube 10b) and also new in my system is the MiniDSP 2x4. I bought the Umik-1 and downloaded REW software, so I would be able to fine tune my system.

System is:

Source: Either BlueOS Nodi 2i or vinyl
Amp: Houston mini 1998+ tube amp
Speakers: Sonus Faber Venere 2.0
Sub: KEF Kube 10b

The MiniDSP is placed between the passive Houston preamp (source selector) and the input of the integrated amp, so the tube amp is (or will be) seeing only the higher frequencies (>80 Hz or so).

What puzzels me is the result of the measurement I did with the REW software on the KEF Kube 10b. I read everywhere this sub can go very low. See attached file for my result. Target is set to 75 dB. Both front speakers and sub were "calibrated" at 75 dB.
Is my new sub broken, or is REW software to complicated for me (I guess the later). What do I do wrong?

By the way: I don't have any filters yet in the MiniDSP. The results for the Venere 2.0 look (in my none expert eyes) more normal I guess.

 

[Rednaxela]

Hi @Peerke007 and welcome!

Is it possible for you to redo the measurement without the miniDSP in place?

 

[Peerke007]

For some reason my previous post is gone???

Anyhow. My Sumiko S.5 went bad (no more output), so I bought a new subwoofer for my little system. After reading good reviews the choice was made for the KEF Kube 10b.

My system consists of:

Source: BlueOS node 2i of vinyl (Technics SL Q2 and Vincent PHO700);
Amp: Houston Mini 1998+ integrated tube amp with separate Houston passive preamp/source selector;
Speakers: Sonus Faber Venere 2.0;
Sub: KEF Kube 10b.

To separate sub signal from the speaker signal I decided to purchase also a MiniDSP 2x4, so my little tube amp will not have to work so hard. Bought also the Umik microfone and installed REW software.

I did not yet configured any filters yet in the MiniDSP, just set the routing.

Calibrated the speakers and sub to 75 dB with pink noise form REW.

Started the measurements. Results see attachments. The Veneres look okay to me, but the KEF is not. I don't know what I'm doing wrong.

@Rednaxela: I did select the 50dB/decade option this time. And yes, I was thinking to connect the sub directly to the preamp out in order to rule out any hidden filters in equipment. Did not had the chance yet to do this. Work just started .

 

[bodhi]

It seems that the subwoofer is getting the signal meant for the main speakers.

 

[Peerke007]

It seems that the subwoofer is getting the signal meant for the main speakers.

I was thinking of that too Bodhi, but I did not put in any filter yet in the MiniDSP. I will check if the measurement in REW is done with the correct range. I believe I measured both front speakers and the sub with a sweep 20 - 20000 Hz

I just read that the BlueOS node 2i is also has a Xover as soon as the subout is connected and the option in the setting menu is enabled. That would be solution also, but only for streaming audio and not when playing vinyl.

As soon as I'm back from work, I will look into the options and double check again.

 

[YSC]

wild guessing, it looks like you've implemented a roll off/high pass filter for the sub at 60hz or so, how do you feed the sub? and maybe need to test the sub only without any filter implaced

 

[Willem]

Anyway, my own Kef Kube 8b gives a more or less full response down to 25 Hz when positioned in a corner.

 

[Rednaxela]

For some reason my previous post is gone???

I see it here.



Edit: I just asked the mods to merge the two threads.

 

[Peerke007]

Ah, now I have this topic twice I guess. This one was gone for a while.

Anyway, after work I will connect the sub directly to the preamp out and redo the whole measurement. I did not enable any filters in the MiniDSP, only the routing was set. But I will do the above mentioned and see if there is a hidden filter I'm not aware of.

I'm going to try to use the sub output of the BlueOS node 2i too and do the measurement. I will post the results.

 

[Peerke007]

Anyway, my own Kef Kube 8b gives a more or less full response down to 25 Hz when positioned in a corner.

Reassuring message, thank you.

 

[Peerke007]

I see it here.



Edit: I just asked the mods to merge the two threads.

Thnx

 

[Peerke007]

Okay, lunch break and the wife is out. So i plugged the KEF direct in the output of my passive preamp/selector. Same result more or less.

Can my laptop output be the filter or should i send the KEF back?

 

[staticV3]

@Peerke007 make sure that in REW's settings under Soundcard, the driver is set to Java and Output is set to EXCL: Laptop out
The EXCL part will ensure that all "enhancements" that the laptop may apply to the output are bypassed.

 

[HarmonicTHD]

Okay, lunch break and the wife is out. So i plugged the KEF direct in the output of my passive preamp/selector. Same result more or less.

Can my laptop output be the filter or should i send the KEF back?

Yes something is wrong here. The sub works so there is little reason to assume that it is broken. Therefore yes it must be something in your signal chain.
You can also try to get a FLAC or WAV file with white or pink noise and have your blueNote play it directly to your sub (make sure everything is set to neutral) and record the sound with REW FFT. This way you can eliminate your preamp and laptop as the source of the problem.

 

[witwald]

Those measured results do seem odd. Have you tried to do a measurement sweep with the microphone a few centimeters from the sealed woofer. That should give you a smooth response, and you can get a better idea if there is more filtering at play than you expected.

 

[Peerke007]

@Peerke007 make sure that in REW's settings under Soundcard, the driver is set to Java and Output is set to EXCL: Laptop out
The EXCL part will ensure that all "enhancements" that the laptop may apply to the output are bypassed.

Done, no difference

 

[Peerke007]

Yes something is wrong here. The sub works so there is little reason to assume that it is broken. Therefore yes it must be something in your signal chain.
You can also try to get a FLAC or WAV file with white or pink noise and have your blueNote play it directly to your sub (make sure everything is set to neutral) and record the sound with REW FFT. This way you can eliminate your preamp and laptop as the source of the problem.

I just connected the sub directly to the sw out of the BlueOS node. No audible bass unless i put the volume knob at 9 - 10 o clock. Not normal I think.

By the way, I turned the Xover knob all the way to LFE, so that should not be the cause either.

I guess I will ask for a replacement.

 

[Kervel]

The measurements suggest a high-pass filter is applied to the sub (while you want a low pass). Can you connect the sub to the main RCA outs of the BlueOS node, so that it receives full signal without Minidsp in the chain, and measure again?

 

[HarmonicTHD]

I just connected the sub directly to the sw out of the BlueOS node. No audible bass unless i put the volume knob at 9 - 10 o clock. Not normal I think.

By the way, I turned the Xover knob all the way to LFE, so that should not be the cause either.

I guess I will ask for a replacement.

Can you hook it up to the mains out not the SW out, just to exclude that the Node does something strange. (Edit. Sorry Kervel was faster).

 

[Sokel]

Doesn't look much different than the measurements here though...

(maybe it describes something else,my German are poor)

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