Cone Cry and Ghost Notes

[Buduranus2]

I've seen some postings about "ghost notes" and wanted to contribute to the discussion. I just installed 4 JBL E110s in a cabinet I recently purchased for that purpose. The tech used a "torque screwdriver" to install them. He asked me why he was using that, and I knew the answer: If you overtighten the speaker mounting screws, it'll warp the speaker frame, and offset the magnet gap (very unlikely on a cast frame speaker but easy enough to do on a stamped basket.) The result is "cone cry." He tightened all the mounting screws to 15 ft/lbs. So any of you experienceing "cone cry" may want to check to see if you've over-tightened the mounting screws.

I also recently discovered the cause of false overtones ("ghost notes") plaguing two of my amps. Turns out that my electrical outlets are improperly grounded. As three knowledgable friends concurred, the amps were "looking for ground" but couldn't find it, creating a "ground loop," perhaps in conjunction with other electronics on the same circuit. The false overtones may have been a multiple of 120 Hz, which would be out of tune with almost everything. So it's worth it to see if that's relevant to your situation. BTW unsafe too.

More commonly, I've read here that the "ghost notes" encountered are false "undertones." Filtering may have something to do with it, but I think ultimately it's the intermodulation (IM) distortion inherent in all guitar amps. While hi-fi amplifiers are engineered to minimize IM and harmonic distortion, they don't make very good guitar amps for exactly that reason. One of my amps has always had false undertones, but with four gain stages it'd stand to reason. After all, each gain stage amplifies and distorts the IM and harmonic distortion of the previous stage. Cheers!

[qingcong]

Ground loops produce a constant 60Hz hum, they're not a factor in altering your amp's behavior. Think of the your amp as a car and ground as smoothness of the road. No matter how bumpy the road, your car is still the same car, you just get a bumpier ride because your reference is not flat.

Overtightening screws potentially causes voice voil rub. Voice coil rub is dangerous and can permanently damage the speaker.

[Buduranus2]

I'm not sure I understand your analogy. If the road's bumpy won't that cause all kinds of problems, i.e. worn tires, front-end misalignment, hubcaps falling off, loose motor mounts etc? So while it's still the same car, it's not in as good condition as if I had driven it on a smooth road. Is that what you meant?

[qingcong]

Yeah, a ground loop can be potentially hazardous to electrical equipment, but my point is that if you have a ground loop, it will be heard as a constant 60Hz hum. If you hear it, then you have a ground loop. If you don't, you do not have a ground loop issue. I'm not sure what you mean by ghost notes or false overtones. Those terms sound more like they have to do with the amp's distortion characteristics and not grounding.

[Sirloin]

Uhhh....15ft lbs??? Maybe you meant 15inch/lbs ? 15 ft lbs is almost enough for lug nuts on a car wheel.

[man_mars]

Originally Posted by Buduranus2

The tech used a "torque screwdriver" to install them. He asked me why he was using that, and I knew the answer: If you overtighten the speaker mounting screws, it'll warp the speaker frame, and offset the magnet gap (very unlikely on a cast frame speaker but easy enough to do on a stamped basket.) The result is "cone cry." He tightened all the mounting screws to 15 ft/lbs. So any of you experienceing "cone cry" may want to check to see if you've over-tightened the mounting screws.

Thanks for the great advice.

I've got a V30 that has horrible cone cry. Thought about changing it to a WGS Vet 30 (a little googling reveals a lot of people have cone cry issues with V30's it seems) but then again some people have even reported cone cry with the Vet 30 (apparently something to do with this type of speaker cone). So for now I've put off the purchase.

There's also some who suggested to me that a larger magnet type speaker (EV12L or Eminence Delta Pro 12A) is the safest bet to avoid cone cry or otherwise Hemp Cones (ala Tone Tubby). Is there any truth to this ?
I really would like to just buy 1 speaker which would get rid of this problem. I'm not really in a position to buy and try different speakers to see what really works.

I'll check if the mounting screws have been over-tightened and if that indeed solves the problem.

Cheers !!!

[gtrnstuff]

I've had some speakers that cry brand new. Some don't. Some of the same type, say V30, that cry on different notes. But usually if they aren't driven too hard it won't show up at all. An Emi Governor that was almost unusable by itself did fine in a 4-12 cab.

[Sirloin]

Does anyone have a recording of a good example of "cone cry"? Just curious...

[man_mars]

Originally Posted by Sirloin

Does anyone have a recording of a good example of "cone cry"? Just curious...

I'll try and make one by this weekend.

Cheers !!!

[qingcong]

Originally Posted by man_mars

There's also some who suggested to me that a larger magnet type speaker (EV12L or Eminence Delta Pro 12A) is the safest bet to avoid cone cry or otherwise Hemp Cones (ala Tone Tubby). Is there any truth to this ?
I really would like to just buy 1 speaker which would get rid of this problem. I'm not really in a position to buy and try different speakers to see what really works.

If you kept everything else the same but increased magnet size (which increases magnet power), your cone cry would be even worse. Cone cry has to do with the damping factor, or Q of the speaker. If you look at the T-S parameters, you'll see a Qt parameter. The lower the number there, the better the damping factor and the less cone cry you will have.

Also, sealed cabinets help to reduce possibility of cone cry, as the air that is trapped in the cabinet acts as a load to keep the voice coil from going out of control.

[qingcong]

The EV12L probably doesn't have issues with cone cry because -
1) it's rated for very high power, so it takes more power to get the voice coil moving beyond the magnetic gap
2) its mechanical suspension is very well designed
3) it has a very low Qts

[man_mars]

Originally Posted by qingcong

The EV12L probably doesn't have issues with cone cry because -
1) it's rated for very high power, so it takes more power to get the voice coil moving beyond the magnetic gap
2) its mechanical suspension is very well designed
3) it has a very low Qts

Hey thanks for the info. Can you list a few speakers you are aware of with very low Qts ?

[qingcong]

Originally Posted by man_mars

Hey thanks for the info. Can you list a few speakers you are aware of with very low Qts ?

I'm afraid it's not quite as easy as just picking one with a low Qts. The speaker's Q is also dependent on cabinet design. The Qts parameter is measured in a free air environment, not a box. In general though, there is a rough correlation.

Basically, most guitar speakers are crappy woofers. V30s, Governors, Greenbacks, etc, they're not actually good designs and you'll encounter issues like cone cry and cone breakup. The EVM12L is a well designed woofer that is suitable for guitar applications.

Speakers like the 12L such as the Weber Michigan, Scholz Sugarcone, Fane Studio 12L, Emi Delta Pro will probably spare you from the side effects of poorly designed guitar speakers.

[pula58]

My experience is that the smaller voice coil diameters (1.75" or smaller) are the speakers most likely to have cone cry. The larger diameter voice coils (EVM12L, JBl's, etc) don't have cone cry issues.

4" voice coil: JBL D120, D120-F, K120,E120
2.5" voice coil: EVM12L, EV SRO, Emi Deltalite, EMi Delta Pro, Weber Michigan



Also, I never had cone cry with the Eminence C-Rex, even though it has a 1.75" voice coil.

Ron at Austin Speakerworks has a good handle on understanding cone cry. His speakers have a 1.75" voice coil and no cone cry.

[man_mars]

Great info guys...Thanks