# REW readings with KEF speakers



## robsong (Apr 3, 2010)

Had Dan over my house to run REW on my system. But we got these strange readings with my KEF Q900 fronts. So why is it taking a nose dive around 2k but my NHT rear looks flat thanks. :help:


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## ajinfla (May 10, 2009)

Hi John,

That looks like the Q900 tweeters are disconnected (or non-functional). I'm surprised you wouldn't have heard this out of the box when listening initially. There are biamp terminals on the back with twist knobs for (dis)engaging, should allow you to test the tweeters separately to see if functional.

cheers,


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## robsong (Apr 3, 2010)

Will check but this is happening to all 3 front speakers.


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## Wayne A. Pflughaupt (Apr 13, 2006)

robsong said:


> Had Dan over my house to run REW on my system. But we got these strange readings with my KEF Q900 fronts. So why is it taking a nose dive around 2k but my NHT rear looks flat thanks. :help:


Hard to say without knowing more about the mic orientation (0-90), calibration file in use (ditto), mic axis in relation to the speakers in question, etc. I doubt it’s inoperable tweeters, however; you’d be seeing a much stiffer rollout above 2 kHz than that, and that 8k spike wouldn’t be there for sure.

Regards, 
Wayne


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## robsong (Apr 3, 2010)

I'm new to all this stuff and just trying to understand what's going on. Why is it the NHT looks good but not the KEF's.


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## Smith_wesson (Mar 2, 2014)

Wayne A. Pflughaupt said:


> Hard to say without knowing more about the mic orientation (0-90), calibration file in use (ditto), mic axis in relation to the speakers in question, etc. I doubt it’s inoperable tweeters, however; you’d be seeing a much stiffer rollout above 2 kHz than that, and that 8k spike wouldn’t be there for sure.
> 
> Regards,
> Wayne


Mic is a UMIK-1. Each speaker was measured separately on axis with 0 deg cal file. I measured his surrounds to make sure there wasn't anything wrong with my equipment(although I had just used it the night before and it worked fine). All of his surrounds stayed flat out to around 15-17khz(Audessy ON) as expected. 

Also it's important to note that the tweeter attenuation is clearly audible during the sweep,.I can hear all the way to 22khz on a good day and i lost track of his mains well before that where as I was able to hear his NHT surrounds complete the sweep.


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## ajinfla (May 10, 2009)

Wayne A. Pflughaupt said:


> I doubt it’s inoperable tweeters, however; you’d be seeing a much stiffer rollout above 2 kHz than that, and that 8k spike wouldn’t be there for sure.
> Regards,
> Wayne












So you're thinking that Robs measurement showing 15db-ish drop from 2k to 5k-ish and spike at 8khz, exactly matching the Stereophile graph above, is just coincidence?
I don't. 

cheers


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## ajinfla (May 10, 2009)

robsong said:


> Will check but this is happening to all 3 front speakers.


What is your center?
I missed it in your graph.

cheers


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## robsong (Apr 3, 2010)

We forgot to put it in but it did the something.


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## Smith_wesson (Mar 2, 2014)

ajinfla said:


> What is your center?
> I missed it in your graph.
> 
> cheers


It was happening with all 3 front KEFs. I didn't include it in the graph because it was getting too busy with 5 lines already.


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## ajinfla (May 10, 2009)

Ok, so a Q...900...????


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## Smith_wesson (Mar 2, 2014)

ajinfla said:


> Ok, so a Q...900...????


The center? I believe so.


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## Smith_wesson (Mar 2, 2014)

My guess is only the bottom posts are being powered. 

I think ajinfla is onto something with those graphs, they look very similar to the measurements we got. I thought his tweeter was busted right away at first, but when all 3 speakers did it that seemed unlikely.


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## ajinfla (May 10, 2009)

Ok gents.
Step 1: twist the center knobs into the "open" position.
Step 2: Connect speaker wires to the bottom terminals, play music, hear sound (probably same as now)
Step 3: Connect speaker wires to the top terminals, play music, hear.....


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## ajinfla (May 10, 2009)

Smith_wesson said:


> I think ajinfla is onto something with those graphs, they look very similar to the measurements we got.


They won't be exact match due to the nearfield vs farfield measurements and mic used, but I know exactly what those drivers measure like, if you catch my drift.

cheers


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## Smith_wesson (Mar 2, 2014)

ajinfla said:


> They won't be exact match due to the nearfield vs farfield measurements and mic used, but I know exactly what those drivers measure like, if you catch my drift.
> 
> cheers


I think I understand. So then that 8k spike is from the mids breaking up right?


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## robsong (Apr 3, 2010)

The center is the Q600c sorry for been late had to help the boss out.


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## robsong (Apr 3, 2010)

I got my terminals connect to the bottom of all speakers. I removed the terminals from my left speaker. Twist the center knobs to open and connect the terminals to top and no sound coming from the left speaker the others are working with connection to the bottom.


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## Wayne A. Pflughaupt (Apr 13, 2006)

ajinfla said:


> So you're thinking that Robs measurement showing 15db-ish drop from 2k to 5k-ish and spike at 8khz, exactly matching the Stereophile graph above, is just coincidence?
> I don't.


Why would you assume that I’ve ever seen that graph before?

And John's graph doesn't "exactly" match. Despite Stereophile’s impressive ability to measure SPL in negative dB values, assuming the green trace is low freq drivers only, they show the drop from 2-5 kHz to be more than 25 dB, not the 15 dB John’s graph shows, which supports my contention that the tweeters aren’t dead (hey thanks for backing me up  ), but for some reason down in level more than they should be.

Or maybe not. Assuming the Sterohile graph (which shows relatively flat high-end response) is near-field, we can naturally expect to see a droop in high freq measurements taken at the listening-position, so John’s graph really isn’t off the mark. 

So to answer the original question...


robsong said:


> But we got these strange readings with my KEF Q900 fronts. So why is it taking a nose dive around 2k but my NHT rear looks flat thanks. :help:


...apparently these speakers are merely softer on the high end than the NHTs are.

Speaking of, the response of those NHTs is pretty impressive! Do they sound as good as they measure?

Regards, 
Wayne


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## robsong (Apr 3, 2010)

OK I went and did all three the center is the only one working per your steps. The NHT speakers are the VT & VS 1.2 line from 1999 I think. I had the Full line up in my system the Towers and rears with VS-2a as center. Give the towers and center to my friend and got the KEF"s.


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## ajinfla (May 10, 2009)

Smith_wesson said:


> I think I understand. So then that 8k spike is from the mids breaking up right?


Yes. It's down a bit due to the series inductor, but the shape is distinct.




robsong said:


> I got my terminals connect to the bottom of all speakers. I removed the terminals from my left speaker. Twist the center knobs to open and connect the terminals to top and no sound coming from the left speaker the others are working with connection to the bottom.


Ok. Problem somewhere between the terminal through to the tweeter itself.
_Very_ strange if all 3 had the same issue, given the center is another model.
With the wires still connected to the top of the left speaker, twist the knobs just to make sure "open" is open and "closed" is closed.
Were these bought new?

cheers


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## robsong (Apr 3, 2010)

Yes NIB. With it open no sound when I close it I get sound with terminals connect top posts.


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## ajinfla (May 10, 2009)

Sorry, cross posting, I now see your center is ok.
The Q900s are operating sans tweeter. Could be the driver itself, or the connections, including XO.
If you're feeeling up to it:
The XO is usually mounted on the inside of the plate terminal. You could pull the plate. The tweeter wires should come down to it (usually blue) and terminate at push on connectors + and -. With the volume lowered, you could try touching your speaker wires to those connectors, see if any sound comes out of tweeter. Or use a AA battery.
Or call KEF.

cheers


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## robsong (Apr 3, 2010)

Is there a video where I can see how this is done thanks guy's for all your help. Looks like I've should have keep my NHT set up. :sad:


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## robsong (Apr 3, 2010)

Took a look at the speaker. It's going to be hard to remove the speaker driver to see what's going on inside. Anyone have any ideas how to do this.


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## littlejohn74 (Feb 11, 2014)

Measurements aside...
How do the Q900s sound?


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## robsong (Apr 3, 2010)

They sound very good. I audition about three speaker's before picking the KEF speakers.


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## ajinfla (May 10, 2009)

robsong said:


> Took a look at the speaker. It's going to be hard to remove the speaker driver to see what's going on inside. Anyone have any ideas how to do this.


Hi John,
Sorry, no video. Yes, popping that very snug press fit trim rig around the driver without scuffing the cabinet is tricky business indeed....hence my previous recommendations.
First of course, would be having KEF handle it. They sent a dud. Call 'em. They are a good company.
2nd, pop the back plate terminal. Blue wires.

cheers


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## robsong (Apr 3, 2010)

Hi ajinfla,

I removed the plate terminal, connect the speaker wires and got sound out of the speaker.


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## ajinfla (May 10, 2009)

By sound out of "speaker", do you mean "tweeter"?
If so, then you issue is with the XO board, or connection to it from upper terminals.
Any reason why this doesn't constitute a return to seller?

cheers


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## robsong (Apr 3, 2010)

Yes sound out of the tweeter. I've also been in contact with Jack at KEF. He believes there is an outside factor that is causing this problem and not the speakers. To have three speakers doing the same thing is very rare. His emailing my REW charts to engineering department in U.K., will get answer in about two days.


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## ajinfla (May 10, 2009)

robsong said:


> OK I went and did all three *the center is the only one working* per your steps.





robsong said:


> To have three speakers doing the same thing is very rare.


:scratch:



robsong said:


> Yes sound out of the tweeter. I've also been in contact with Jack at KEF. He believes there is an outside factor that is causing this problem and not the speakers.


You explained to Jack there *is* sound out of the tweeter when you touch your speaker cables from the AVR direct to the crimp terminals on the XO board for the wires that lead directly to the tweeter, but *no sound* when connected at the upper binding posts on the rear cup.....and it's an _outside_ the speaker factor??
Something's getting lost in translation here. 
Best of luck, hopefully they work this out for you. Keep us updated.

cheers


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## robsong (Apr 3, 2010)

Will just got a reply back from Jack. Looks like I could be having a problem with the tweeters. They are going to send me instructions on how to remove the driver. He wants me to check the XO board for lose connections.


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## ajinfla (May 10, 2009)

Hey John, are your speaker cables banana plugs, or bare wire, or..?


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## robsong (Apr 3, 2010)

Banana plugs.


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## ajinfla (May 10, 2009)

If you got sound out of the tweeter using the method I suggested, I highly doubt it's the driver.
Try repeating the process, make sure you get sound from the tweeter. Then, do again, but this time plug the negative banana plug into the upper negative jack on the back plate. Touch the positive like you did before to the positive crimp terminal on the XO board (should be labeled). See if the fault is in the ground path.
Remember to keep the volume relatively low. A good test signal is FM, tuned between stations noise.

cheers


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## robsong (Apr 3, 2010)

I got the plate off the back. But I notice that the blue wires are connected to the top posts and the red ones to the bottom.


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## robsong (Apr 3, 2010)

OK I removed the plate connected the negative to the top and touch the positive on XO board and open the center knobs into the "open" position. I get no sound then close the center knobs I get sound.


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## ajinfla (May 10, 2009)

robsong said:


> I got the plate off the back. But I notice that the blue wires are connected to the top posts and the red ones to the bottom.


Yes, that's what I've been saying all along. That's why you're plugged into top. 
Does this mean you unscrewed the XO circuit board from the plate to expose where the wires are push on connected to the back of the banana post terminals?


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## ajinfla (May 10, 2009)

robsong said:


> OK I removed the plate connected the negative to the top and touch the positive on XO board and open the center knobs into the "open" position. I get no sound then close the center knobs I get sound.


_*If*_ your descriptions are accurate, then the problem seems to be on the positive side. Regardless, this long ago should have been KEFs problem. It's clearly not "external", as I could tell from your first post. Beware of voiding warranty with further tinkering!
Maybe check to see if wires from XO board are properly connected to the upper binding posts, especially the + one. Or ask KEF to take care of this.

cheers


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## robsong (Apr 3, 2010)

I email them yesterday about the blue wire been on top and that's the way it should be. But on the manual it shows single wire connections goes to the bottom post. They will take care of me.


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## robsong (Apr 3, 2010)

Just got my new drivers from KEF and installed one and what a difference between the two speakers. Going to install the next one and a run some test again. :T


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## robsong (Apr 3, 2010)

Finally got done doing some calibration with the new drivers. Now it looks like I'm having an issue with the center speaker. :hissyfit:


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## ajinfla (May 10, 2009)

Hi John,

Did you swap the center with either L or R to see if the problem is the center speaker itself?
L & R look just fine now...


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## robsong (Apr 3, 2010)

The driver for the center is smaller than the fronts. I'm going to call KEF tomorrow and see what happens. Just can't believe that all three tweeters went bad.


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## ajinfla (May 10, 2009)

I meant the entire speaker, not the driver 
But yes, going through KEF is your best bet


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## robsong (Apr 3, 2010)

OK got it thanks.


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