Unexpected disappointing performance of KEF Q300 :(

[elangoas]

You are absolutely right. My bad.. I some how assumed that AVRs will honor the speaker size and do the cross over appropriately .

-John.

Chill buddy... I too learn it after some experience with three different AVR ( Onkyo, Marantz & Harman Kardon) & all of them does the same thing when you say Pure Audio/ Pure Direct / Source Direct.... So was sure that Denon also must be doing the same thing....


Anyways, now that you have fixed it, Happy listening :clapping:

 

[john_k_antony]

^^^

Thanks dude. I will check with ProFx if I can get a replacement / repair for the damage. How ever the damage doesn't look so serious as its still sounding fine and my center channel is safe and that's where majority of action takes place for movies apart from the Subwoofer .

I also have a spare Q300 that I can use if the right channel speaker develop some issues later on.

Thanks,
John.

 

[mpw]

Happy you found the cause John.

any thoughts on changing the title of the thread ?

Since you discovered your mistake and it was not really the speaker you may request the mods to allow you to put in a more humble / circumspect title.

KEF may not take too kindly to the present thread title.

regards
mpw

 

[john_k_antony]

Mpw,

I still feel KEF disappointed me for 2 reasons.

It is rated at 120w and promises to go all the way down to 42Hz. It miserably failed in both the departments. So as a consumer I am not happy with the speakers. I am planning to take this up with KEF directly for giving misleading specs. I wouldn't have run Q300 to louder volume if they said it can't handle more power. I drove it with 105w/ch amp and it couldn't take it even with its rated 120w handling capacity.

I hope I am making sense.

Thanks
John.

 

[john_k_antony]

Got the videos uploaded. Here it is

Very vigorously moving Right channel speaker and hardly any movement from Subwoofer. The movement goes crazy as I increase the volume. The video starts with volume level of 65 on Denon and I turn it up to 73 gradually generating a SPL level of 80db at 18 ft from the speakers.

20131006023533 - YouTube

Lighly moving Center speaker and vigourusly moving Right Speaker with the same volume level of 73 in Denon.

20131006023755 - YouTube

After turning off Pure Direct in Denon. Right speaker is not moving that much, Subwoofer is working very active now . Here I am getting the SLP of 80db with volume level of 68 in Denon.

20131006023942 - YouTube

I hope the Subwoofer movement in the above video is expected right or am I going to blow my Subwoofer too soon ?

Thanks,
John.

 

[Santy]

@ John
Remember, when you started to build your HT, I asked if the bookshelves would have enough juice to fill such a large room? I had the same situation in mind that you are facing now when I asked so.

There seems to be a problem with KEF300's bass handling ability. We heard it with Denon PM710AE and it was just coughing up during intense bass passages. Like the speaker cones fluttering and about to be thrown out of the box. That was music. Now movies could be more intense as far as low frequency is concerned.

And don't worry about the sub. The excursions seen in your video is hardly anything. The sub's driver is designed to move. Move the air. Plenty of it. Its quite difficult to blow it out.

@mpw
The KEFs have very nice, refined and controlled bass but when that is fed a shade more, they seem to give up. So there is a reason for Johns disappointment and I too have made up my mind not to recommend this for those who are into both music and movies.

 

[john_k_antony]

Yes Santy, I very well remember your point. Well some lessons are learnt the hard way .

However, end of the day I am okay as I have found the optimum setting that works well for my Denon + KEF setup, that is no more Pure Direct. Also I still love the midrange performance of Q300 and the dialog clarity is simply AMAZING. Thank god, I didn't screw up my center channel yet .

I also learnt the truth the hard way that DO NOT trust the specs of any speaker manufactures blindly and always include the boundary conditions in your audition. Its pretty difficult to test the extreme conditions in most of the auditions as the dealer "smartly" never lets to control the volume and loudness beyond a certain extend. And also I have found that most of the demo rooms in Bangalore are smaller than my room size of 375sft and the speakers attain a very good loudness level in the smaller demo rooms with lesser volume levels and they perform fine. Same has happened with my Q300 demo in ProFx. Only when you push them to the limits, you see its limitations.

I chose Q300 after lots of auditions, but never had them pushed to the limits. I trusted the specs and assumed that it will perform fine when pushed harder by looking at the specs. And I never expected it to perform BADLY when they are pushed harder, but well with in their allowable limits according to the specs. But I was proved wrong.

I think KEF Q300 should NEVER be fed any thing less than 100Hz at a reasonably louder volumes or you will damage the driver. Disclaimer : This is purely my opinion after my bitter experience with them and looking at the damage caused to the driver cones .

Thanks,
John.

 

[kapvin]

Mpw,

I still feel KEF disappointed me for 2 reasons.

It is rated at 120w and promises to go all the way down to 42Hz. It miserably failed in both the departments. So as a consumer I am not happy with the speakers. I am planning to take this up with KEF directly for giving misleading specs. I wouldn't have run Q300 to louder volume if they said it can't handle more power. I drove it with 105w/ch amp and it couldn't take it even with its rated 120w handling capacity.

I hope I am making sense.

Thanks
John.

Dear Mr. Anthony,

Good you found the source of the issue. almost all of us who push the envelope a little have at some point of time cooked a speaker or two. for most of us it happens early in our music journey so the impact is not too much. for you it is unfortunate.

now, for some unpalatable facts, if I may. your speakers are "cooked", if you are happy with the sound, good for you, but given the photos that you posted, I would be very surprised if they sounded as the manufacturer intended. the misshapen cone will not be structurally as sound, as most likely your sound will degenerate further by the very act of feeding dynamic music. high pass of 100hz is not the solution either, unless you have a super clean sub; the 50hz-100hz octave is better filled by the Kef, and if you wanted to high pass at 100hz, you could have purchased a smaller pair of speakers.

secondly as per claims of Kef - though I am no fanboy, Kef is not going to spoil their reputation by underspecing a popular design. I am sure that the specs are as on or off as any other manufacturer's. the problem is not power handling either i am sure in can handle 120w without a problem. the problem lies (and with most speakers) when feed low bass energy at high power. putting even 100w of bass will cause over excursion and much worse if you feed bass below the tuning frequency.

in fact it is a testament to kef quality that they are still playing acceptably. many other speakers would just jam solid when subjected to this abuse.

finally - my suggestion - get in touch with the dealer and try to get the drivers replaced. if not both then at least one and then you can swap the other for the centre channel.

you would have spent a decent amount on the kefs, make sure that you can really enjoy them.

as a postscript - like it has been written in earlier posts, pure direct is fine and even advisable for almost all music. but for Home theatre, always use the bass management and as a rule of thumb set the crossover at least 1/2 and octave above the Low frequency limit - i.e if you speaker is rated at 40hz, get the crossover for 60hz.

Edit i just saw the video - for 80dB spl the sub is moving too much. (i am assuming a 10 or 12"sub) it seems there is a lot of ultra low frequency content in your music. how did you measure and arrive at the 80dB spl number?

 

[john_k_antony]

I totally agree Kapvin. Even I am really surprised to see Q300 still sounding ok even after such an abuse and deformed and dented cones. But they are jarring at high volumes now and that means they are already "cooked" . Now I am keeping the volume lower, which I am not very happy with. I also wanted anything above 80Hz or even 60Hz to be handled by KEFs. But with my bitter experience, I don't want to feed anything less than 100Hz to KEFs anymore. My Sub is Velodyne EQMax 12 and I feel it does a decent job for 50-100Hz. I think I need more listening to see whether this setup is working fine or not..

I will talk to the dealer - ProFx and also write to KEF regarding this unpleasant experience. Let me see what can be done. I have a spare Q300 in the box as I have bought 2 pairs and right now using only 3 of them for L-C-R. So I can replace my overly damaged Right channel with the spare. But I will definitely try my luck with ProFx and try to get my drivers repaired or replaced with in warranty. It is highly unlikely that I get a replacement in this country as 99% of the dealers are GREEDY and will refuse my claim with some silly reasons. However, I will try my luck though . Will keep you guys posted.

Thanks,
John.

 

[kapvin]

I totally agree Kapvin. Even I am really surprised to see Q300 still sounding ok even after such an abuse and deformed and dented cones. But they are jarring at high volumes now and that means they are already "cooked" . Now I am keeping the volume lower, which I am not very happy with. I also wanted anything above 80Hz or even 60Hz to be handled by KEFs. But with my bitter experience, I don't want to feed anything less than 100Hz to KEFs anymore. My Sub is Velodyne EQMax 12 and I feel it does a decent job for 50-100Hz. I think I need more listening to see whether this setup is working fine or not..

I will talk to the dealer - ProFx and also write to KEF regarding this unpleasant experience. Let me see what can be done. I have a spare Q300 in the box as I have bought 2 pairs and right now using only 3 of them for L-C-R. So I can replace my overly damaged Right channel with the spare. But I will definitely try my luck with ProFx and try to get my drivers repaired or replaced with in warranty. It is highly unlikely that I get a replacement in this country as 99% of the dealers are GREEDY and will refuse my claim with some silly reasons. However, I will try my luck though . Will keep you guys posted.

Thanks,
John.

well if you purchased 2 pairs then you have a working stereo pair. I guess your centre channel is okay. so move that to one channel the new one to the other. you are back in business! as for centre channel duties, you can use the less damaged one high passed at 100hz.

meanwhile try your luck with pro-fx. my experience with them has been good, but you will need to speak to the head office, the guys at the retail outlets are useless on these issues. i think they can share the blame, esp if they sold you the denon - after they should have explained pure direct mode better. ;-)

Kapvin

 

[john_k_antony]

Kapvin,

I used an SPL meter placed at my listening position that is 18ft away from the front speakers and Subwoofer to measure the db levels. As you said, even I am really surprised to see such a vigorous Subwoofer movement, that's why I was checking whether the movement of the Subwoofer is normal or not.

Well my room is treated for first and second reflection points for all the front speakers with side wall absorbers. The entire false ceiling is acoustically absorbing and I have floor to wall corner bass traps in all the four corners of he room that are 2' wide and 6" thick. So I feel my room is not "helping" the Subwoofer and seems like my Subwoofer needs to work little harder to create a room filling bass in my dedicated room. The result is I am getting absolutely non boomy bass.

The Subwoofer has a 12" driver. It is Velodybe EQ Max 12. The volume setting in the Sub is set at 45 when the video was taken and the max volume level is 80 for the Sub. The volume was set at 68 in AVR, where 100 is the max and the channel level for the Sub was set at 0db in AVR. The cross over frequency was set at 100Hz in AVR.

Thanks,
John.

 

[john_k_antony]

Hey Kapvin,

I hope Pro-Fx will listen to my concern as I am a returning customer and have bought 5 pairs of KEFs and 1 Denon AVR from them already .

Lets see.

Thanks,
John.

 

[Audio_Freek]

venk61176,

I think I learnt my lesson the bad way . Its still okay as my speakers are still working fine.

I have a different setting for 2 channel in Denon and I have kept the speakers as Small there as well and also set the cross over at 100Hz. But I don't use my Denon + KEF for 2 channel anyways. I have a different setup for 2 channel stereo. So I guess I am fine as long as I use Denon + KEF only for movies and NEVER EVER use Pure Direct mode for that .

Thanks,
John.

Johny\all,

I have a question here,it would sound silly but if some tech Guru would advice, it would be greatfull.

What is the Function of Xovers in Speaker specifically Q300,In case the Drivers have been damaged then probably the Xovers also should have damaged.In case the X overs are not damaged, then does it means that Xovers were allowing the full range frequency to the drivers?

1.Its issue with Amp or Driver or Xover design?

 

[doors666]

you cant blame kef et al in this case. all the fault is yours. By using pure direct mode, you allowed even 20hz content to goto the speakers, that too at very loud volumes. you subwoofer will not function in pure direct mode, but you failed to notice that. the moment the speakers started complaining, you didnt reduce the volume to control the excursion of the drivers. No point blaming KEF for this, they should not be held responsible for this.

 

[reignofchaos]

Distortion from the amp - especially DC at the output which most cheap AVRs and amps end up outputting when driven to the limit is really bad for speakers. The only solution for this is to get a better/more powerful amp.

Also if one notices the speaker cones bottoming out, one has to reduce the volume or risk damaging them.

Follow the above and the speakers won't get damaged. I'm not sure what the issue was here but either of the above could have caused the damage in this case.

 

[john_k_antony]

you cant blame kef et al in this case. all the fault is yours. By using pure direct mode, you allowed even 20hz content to goto the speakers, that too at very loud volumes. you subwoofer will not function in pure direct mode, but you failed to notice that. the moment the speakers started complaining, you didnt reduce the volume to control the excursion of the drivers. No point blaming KEF for this, they should not be held responsible for this.

Let me ask you a very simple (or rather dumb) question here. If I was using Q300 with a Stereo Integrated Amp rated at 100w/ch with NO bass control or bass management or cross over and most of the stereo amps are capable of outputting 15-20Hz to 40Khz frequency response. And do you say that Q300 would have performed perfectly fine in that case? Now you are saying that one should NEVER use KEF Q300 with a stereo integrated amp rated at 100w/ch that does frequency response form 20Hz to 20Khz.. I doubt KEF never said that or mentioned it anywhere.

FYI.. my subwoofer was working in the pure direct mode all the time, but was not excurting fully during normal scecens and it did move properly during heavy bass sequence. I guess all the LFE information was definitely passed on to Sub. However Denon didn't send bass content from LCR + Surround channels to Subwoofer in pure direct mode.

I don't know if a SPL level of 80db, 18ft from the speakers can be termed "very loud". I agree its reasonably loud. Again Q300 specs say the max SPL it can produce is 110db, which is much higher than the 80db level I was asking them to create!.

My speakers had the dust cover on. Frankly I was not expecting Q300 was the cause as I thought the distortion was coming from else where. But by the time I opened the dust cover and saw the cones excurting very badly, the damage was already made.

I also have the same question regarding X-over. A good speaker with proper X-over design should be rolling off frequencies that are not capable of reproducing by the drivers. I assume that is the basics of the X-over design in any "well-designed" speakers. I am really surprised that KEF Q300's X-over failed here. I am not sure if the X-over was faulty in the first place, as in manufacturing defect.

BTW, I have taken this issue with KEF and Pro-Fx. Waiting for the response.

Thanks,
John.

 

[kapvin]

Johny\all,

I have a question here,it would sound silly but if some tech Guru would advice, it would be greatfull.

What is the Function of Xovers in Speaker specifically Q300,In case the Drivers have been damaged then probably the Xovers also should have damaged.In case the X overs are not damaged, then does it means that Xovers were allowing the full range frequency to the drivers?

1.Its issue with Amp or Driver or Xover design?

Not really. see my post on electrical rating. crossover are designed with a lot of tolerance in mind; failure can happen, but mostly because of age.

most crossovers do not have a high pass filter to the woofer- in order to preserve as much musical information as possible. In my humble opinion, the absence is a desirable feature, and adding such a filter will add to the part cost significantly, while also reducing fidelity.

the speaker is designed based on how most people listen to music. this is designed for people who prefer midrange fidelity over other attributes. if you listen to music with deep sub bass content, there are other speakers thatmight be better. in fact, you'd probably reject the kefs at audition stage. (the last time I purchase speakers, i rejected kef for precisely that reason - my system was going to do dual duty Music +HT)

many times on the forum it has been written that you should audition speakers with music that you really listen to. But on the rare occasions i go to hifi stores, I see people listening to the "usual suspects". is there such a need to impress the store people of your "audiophile" credentials?

 

[doors666]

Let me ask you a very simple (or rather dumb) question here. If I was using Q300 with a Stereo Integrated Amp rated at 100w/ch with NO bass control or bass management or cross over and most of the stereo amps are capable of outputting 15-20Hz to 40Khz frequency response. And do you say that Q300 would have performed perfectly fine in that case? Now you are saying that one should NEVER use KEF Q300 with a stereo integrated amp rated at 100w/ch that does frequency response form 20Hz to 20Khz.. I doubt KEF never said that or mentioned it anywhere.

Usually music doesnt go below some 35hz, except for a very few instruments. Action movies can go down to some 10-20hz also.

FYI.. my subwoofer was working in the pure direct mode all the time, but was not excurting fully during normal scecens and it did move properly during heavy bass sequence. I guess all the LFE information was definitely passed on to Sub. However Denon didn't send bass content from LCR + Surround channels to Subwoofer in pure direct mode.

Since you are decoding the audio in your oppo, what are the settings there? What is your source, if its a downloaded file from the internet, its possible that the main 2 ch audio contains the low freq also which werent filtered to LFE, due to a bad rip. Denon is just amplifiying the signal it received from oppo and sending it to the speakers.

I don't know if a SPL level of 80db, 18ft from the speakers can be termed "very loud". I agree its reasonably loud. Again Q300 specs say the max SPL it can produce is 110db, which is much higher than the 80db level I was asking them to create!.

the standard spl is at a distance of 1m (or 2m, check on it), with every doubling of distance, the spl drops by 3db if my memory serves me right.
SPL handling also depends upon the frequency. if a speaker can do 110 db at 1khz, does not mean it can do the same at 40hz.

My speakers had the dust cover on. Frankly I was not expecting Q300 was the cause as I thought the distortion was coming from else where. But by the time I opened the dust cover and saw the cones excurting very badly, the damage was already made.

I also have the same question regarding X-over. A good speaker with proper X-over design should be rolling off frequencies that are not capable of reproducing by the drivers. I assume that is the basics of the X-over design in any "well-designed" speakers. I am really surprised that KEF Q300's X-over failed here. I am not sure if the X-over was faulty in the first place, as in manufacturing defect.

BTW, I have taken this issue with KEF and Pro-Fx. Waiting for the response.

Thanks,
John.

You are not talking about crossover. The crossover in a speaker is between the woofer and the tweeter and is at about 1.5k-4khz usually, depending upon the capability of the drivers and the order of the crossover. What you are talking about is a high pass filter at some 40hz at the lower end. As far as i know, no speaker in the world provides that. That is why the receiver sets it for you. thats the frequency at which the speaker crosses over with a sub, at 40hz or 100hz or whatever. Since you are using a pure direct mode, that didnot work. There is one more setting you need to check in your amp and oppo, speakers are set to large/small and if the bass is sent to both the mains and sub or just the sub. my yamaha amp has such a setting where I can choose to send low frequencies to both sub and mains or just the sub.

 

[kapvin]

Let me ask you a very simple (or rather dumb) question here. If I was using Q300 with a Stereo Integrated Amp rated at 100w/ch with NO bass control or bass management or cross over and most of the stereo amps are capable of outputting 15-20Hz to 40Khz frequency response. And do you say that Q300 would have performed perfectly fine in that case? Now you are saying that one should NEVER use KEF Q300 with a stereo integrated amp rated at 100w/ch that does frequency response form 20Hz to 20Khz.. I doubt KEF never said that or mentioned it anywhere.

FYI.. my subwoofer was working in the pure direct mode all the time, but was not excurting fully during normal scecens and it did move properly during heavy bass sequence. I guess all the LFE information was definitely passed on to Sub. However Denon didn't send bass content from LCR + Surround channels to Subwoofer in pure direct mode.

I don't know if a SPL level of 80db, 18ft from the speakers can be termed "very loud". I agree its reasonably loud. Again Q300 specs say the max SPL it can produce is 110db, which is much higher than the 80db level I was asking them to create!.

My speakers had the dust cover on. Frankly I was not expecting Q300 was the cause as I thought the distortion was coming from else where. But by the time I opened the dust cover and saw the cones excurting very badly, the damage was already made.

I also have the same question regarding X-over. A good speaker with proper X-over design should be rolling off frequencies that are not capable of reproducing by the drivers. I assume that is the basics of the X-over design in any "well-designed" speakers. I am really surprised that KEF Q300's X-over failed here. I am not sure if the X-over was faulty in the first place, as in manufacturing defect.

BTW, I have taken this issue with KEF and Pro-Fx. Waiting for the response.

Thanks,
John.

John, you are right. in fact i see no issues with using a 150w amp with your speakers. WRT to overexurcison, you can hear it as well as see it. In most cases. as you raise the volume you will hear the sound hardening and compressing before you overdrive the woofer ( and there is a sound technical reason why that happens). you need to watch out for that.


WRT to crossover see my previous post.

80dB is not loud. but if you want 80dB of 20hz bass from the bookshelf - it is waaaay too loud. you are asking a bit much from your speakers.
1. you want them clear,
2. you want them small,
3. you want them cheap (WRT to the average spend of a hifi fan)
4. and you want deep bass.

if that were all possible in 1 speaker, then forum members are less than wise to buy their multi lakh speakers, right?

. pls do not blame the speakers.

 

[john_k_antony]

Doors,

I am not doing any processing in Oppo for digital output via HDMI. All the decoding is done in Denon. As far as I know, Oppo does speaker management and bass management only for if you use the analog outs.

I stand corrected on the X-over part. I agree with you on the X-over part. I understand that the Low Pass Filter is done by the Amp.

The content played was a 5.1 channel source. Yes it was a DVD rip from the original DVD and not the original DVD disc.

I know its a wrong thing to compare, but I have similarly speced KEFs in the same room

1. Kef iQ7.

Amplifier Requirements: 15-150W
Frequency response: 40Hz to 40kHz +/-3.0dB
Sensitivity: 90dB at 1m for 2.83V
Maximum output: 111dB

2. Kef Q300

Amplifier requirements 15 - 120W
Frequency Response 3dB 42Hz - 40kHz
Sensitivity (2.83V/1m) 87dB
Maximum output (SPL) 110dB

Kef iQ7 being a FS with 3 driver/3 way cross over does the same music sequence effortlessly and Q300 for the same music sequence runs out of breath.

I know iQ7 has 90db sensitivity compared to 87db of Q300 and would only need half the power to reach the same SPL level that is needed by Q300.

But in either case, I have provided much lesser power to both the speakers than its rated power handling of 150w and 120w respectively. I would assume Denon would have been outputting around 70w to Q300 at the volume level of 73 out of 100 when Q300 was excurting like crazy.

My only worry is that KEF didn't warn me from any of this and I went blindly based on the Specs. According to the Specs, Q300 should have handled this "abuse".

I will see what KEF has to say about this. Waiting for their response.

Thanks,
John.