Distorting Kick Drum

Distorting Kick Drum

Postby Dorian » Thu May 02, 2019 12:00 pm

I have a new problem. On certain tracks with prominent kick drum (bass drum), if I turn the volume up pretty loud, the bass starts distorting. It's ok at lower volumes. You know that terrible sound when a car drives by with its stereo turned up way too loud and the subwoofers are distorting? That sound. Not good.

I did measure my room recently using REW and there is a prominent spike in the bass in my room. I also recently switched the speakers terminals on my amp from the 4ohm to the 8ohm and although the sound is overall better on the 8ohm terminals (more open and relaxed), the bass distortion is more pronounced. Any ideas what this is? Is it simply a room mode being excited and my only solution is to move speakers and/or add room treatments (or keep the volume down!), or could there be something else going on here?

Thanks.
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Re: Distorting Kick Drum

Postby Brf » Thu May 02, 2019 12:54 pm

Dorian wrote:I have a new problem. On certain tracks with prominent kick drum (bass drum), if I turn the volume up pretty loud, the bass starts distorting. It's ok at lower volumes. You know that terrible sound when a car drives by with its stereo turned up way too loud and the subwoofers are distorting? That sound. Not good.

I did measure my room recently using REW and there is a prominent spike in the bass in my room. I also recently switched the speakers terminals on my amp from the 4ohm to the 8ohm and although the sound is overall better on the 8ohm terminals (more open and relaxed), the bass distortion is more pronounced. Any ideas what this is? Is it simply a room mode being excited and my only solution is to move speakers and/or add room treatments (or keep the volume down!), or could there be something else going on here?

Thanks.


Based on your description, your amp is having difficulty controlling your speakers. The LS50 dips to 4 ohms in the 150-200hz range, which is the kick drum range. Having your speakers attached the 8ohm tap of your tube amplifier compounds the issue by limiting current. I would use the 4ohm tap for the LS50
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Re: Distorting Kick Drum

Postby Dorian » Thu May 02, 2019 1:16 pm

OK will do Brf, thanks as always for your excellent advice. It's a shame that is the answer though, as I'm sure it sounds better on the 8ohm taps. Or am I imagining that?
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Re: Distorting Kick Drum

Postby Brf » Thu May 02, 2019 1:18 pm

Dorian wrote:OK will do Brf, thanks as always for your excellent advice. It's a shame that is the answer though, as I'm sure it sounds better on the 8ohm taps. Or am I imagining that?


If the kick drum distortion disappears, you will be convinced that the 4 ohm taps sounds better :-)
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Re: Distorting Kick Drum

Postby Dorian » Thu May 02, 2019 3:29 pm

Listening on the 4 ohm taps right now. It has reduced the issue, but not entirely eliminated it.

I know nothing about electrical engineering, so forgive what may be simple questions. Is the issue essentially that I need an amp with more power to drive the LS50s at high SPLs without distortion? I have a full complement of KT-120 power tubes in the Primaluna HP, which I think gives me at least 100 watts per channel.
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Re: Distorting Kick Drum

Postby Golear » Thu May 02, 2019 5:40 pm

What you described is "cone breakup", I think. That can damage the driver. A higher powered amp may not help. 100W is more than enough power from an amp.

You might need to:
- listen at a lower level, or
- put the system in a smaller room; or
- sit closer (near field listening) so you can set a lower volume; or
- get bigger speakers, that can fill a bigger room. Small speakers need small rooms, big speakers need big rooms. And vice versa.

BTW, I suggest getting a phone app or stand-alone sound level meter. You should, I gather, be listening at about 85 dB (max) at your listening position. That's the level that many mastering engineers use as a ref. If your playback level is less than that, you might not get the right level of bass (because how we hear bass depends a lot on the level). If you play much louder than that, then the tonal balance is not what the engineer had in mind and you risk injury to your ears. You need a phone app or stand-alone meter because each LP will be cut at a slightly different level. So you need to set the volume for each LP.
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Re: Distorting Kick Drum

Postby Johnny » Fri May 03, 2019 8:08 am

I’ve heard the LS50 many times and it is quite capable of playing high spl with tight impactful kick bass. The LS50 likes power, therefore, you might be pushing your tube amp beyond its limits, especially considering the huge impedance swing in the bass region (which is tough on tube amps).
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Re: Distorting Kick Drum

Postby Dorian » Fri May 03, 2019 2:56 pm

Thanks Golear and Johnny.

My room size is not large: 16'4' x 12'4" x 9'.

I do have a SPL meter; I will check the level at which breakup starts to occur and report back.
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Re: Distorting Kick Drum

Postby kurtster » Sat May 04, 2019 8:40 am

Post updated below.
Last edited by kurtster on Sun May 05, 2019 12:04 pm, edited 1 time in total.
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Re: Distorting Kick Drum

Postby kurtster » Sun May 05, 2019 12:02 pm

Dorian wrote:I have a new problem. On certain tracks with prominent kick drum (bass drum), if I turn the volume up pretty loud, the bass starts distorting. It's ok at lower volumes. You know that terrible sound when a car drives by with its stereo turned up way too loud and the subwoofers are distorting? That sound. Not good.

I did measure my room recently using REW and there is a prominent spike in the bass in my room. I also recently switched the speakers terminals on my amp from the 4ohm to the 8ohm and although the sound is overall better on the 8ohm terminals (more open and relaxed), the bass distortion is more pronounced. Any ideas what this is? Is it simply a room mode being excited and my only solution is to move speakers and/or add room treatments (or keep the volume down!), or could there be something else going on here?

Thanks.


Distortion on certain songs ? Hmmm. Any in particular ? It could be at some very busy crescendo and there is too much going on for the woofer to properly handle everything at once. Perhaps with live recordings ? More than likely this could be relieved with a subwoofer to take away the need for the KEF's woofer to work so hard. A kick drum can go really low and work a woofer very very hard much lower than 150 hz. They can certainly exceed the lower range of your KEF's. This chart may help out. It helped me out very much for setting up EQ's when I do remastering of audio tracks and understanding where to look for what.

Updated reply. The 4 ohm vs 8 ohm subtleties are admittedly above my paygrade so I'm approaching this from the sonic results based upon listening and the school of hard knocks.

I did take a look at your IA. Very nice and was happy to see that it has a sub out. Does it have the ability to cut off the lower frequencies to the main speakers ? Could not access any manuals. That is critical. Just freeing the KEF's from everything below 120 hz will dramatically improve their overall ability to handle everything else above 120 or 140 hzs just for conversational purposes. With no where near the ability to afford what you have, using a sub woofer has greatly improved the listenability and performance of my small Polk mains. Back in the 90's Stereophile recommended the Optimus LX5's coupled with the Realistic 10" in line passive subwoofer (with a 120hz cutoff) as a very affordable and listenable system. About 10 years ago, the surrounds blew out in the LX5's and I got the Polk's based upon a friend's recommendation. They were adequate, but when putting the sub in front, everything shined. The Polk woofers then just became mids and were freed up to work much better. Then the surround went in the sub. Looked around and all I could find were powered subs. Dismayed with the searches and the prices, I elected to re foam the sub surround. Couldn't be more happy with the results. Point being, I think a sub of some sort is needed to supplement your KEF's and let them do what they do best. From the audio engineering side of things, having the in line sub kept all the sound natural with out having to worry about separate volume settings in a powered sub and wondering if things were flat and natural sounding as intended and should be.

Granted that my primary musical interests are in rock and roll, through the years of doing audio work, I learned that the bulk of the frequencies lie between 60 to 10k hzs. So with having the passive sub in line with the mains, I cut off all frequencies below 40 hz so the sub did not have to even try reproducing what is basically noise and it is working much more efficiently as a result.

I would love to find another nice in line passive sub or a pair. Otherwise, it demonstrates the need for good old fashioned 3 way speakers. I have my old Cerwin Vega R123's from the 70's sitting waiting to be re foamed, which might be my next project for S & G's. Just some thoughts from an old, old school fool.

Cheers !

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The source ... http://www.audio-issues.com/music-mixing/all-the-eq-information-youll-ever-need/
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