tictac wrote:Not to change the subject but I just read some interesting stuff about the EVM12L speakers. It seems they suffer from a phenomina called "cone sag". Evidently due to the heavy voice coil used in these series speakers gravity will cause the cone to deform causing voice coil rub.
The recommended fix for this condition is to rotate the speaker every six months or store them lying flat when not in use. Obviously reconing is the only solution if this doesn't work.
I wonder if this could be one of the reasons why later in his career SRV played with his cabs laying on their back?
I have an EVM12L that worked fine but then started this "cone cry" sound; it's been in storage for a couple of years lying flat; maybe it'll work fine now....hmmmm....
TT
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additional thread de-railment
A guy here in the bucks,pa area who re-cones speakers was telling me the same thing about EVM12L cones, "They go sour"- I had 2 re-conned and the difference was night and day, took a good bit of time to break them in again but once there the sound was tighter..
A lot of truth in what Tony has said!
I have been tweaking my 102 since I had it, partly because it's fun experimenting and partly to try to "improve" the tones available.
Yesterday I put it back to the layout stock values and guess what - it still sounds great!
I think there is a lot of mileage in adapting your playing technique a little to suit the amp as they are incredibly touch sensitive. As also said, the room will affect the performance more than probably changing a resistor value a couple of ohms.
Most people who hear the ODS amps are blown away by the inherent quality and definition of the sound and in a full band setting, it is perhaps more important to find a sonic space not inhabited by horns or keys or other guitars than anything else.
At home I use the mid boost a lot but when out, it muddies up my sound I found.
If I do some stuff as a 3 piece, then that is the only time I can do what I like without worrying about the frequencies I am using.
EVs just get weird. I love still them. I am in Phoenix where the humidity is usually very low. I have used EV VCs & JBL Cones in Altec 15" frames. I do that for my Evans clones. (pedal steel amps). Those big cast frame 12" EVs sound great in my Insanepro Supro based 90 watt combos. The wackier it is the more attention it gets, & 8 6973 tubes is wacky. They will run very nicely through a 1900 ohm CT Hammond OT. The math is perfect coming off of a 23 watt Supro 1624T & adding 6 more tubes. The 12" EV sounds quite a bit like the Rola which would smoke at 35 watts, let alone 90+. Our biggest problem in Arizona's deserts is poor air quality & low humidity leading to dry rot. The speaker cone paper just shatters. Forced air heating is also horrible for cones, & acoustic guitars alike.
Last edited by Satch on Sat Dec 21, 2013 1:06 pm, edited 2 times in total.
Cone cry is usually not a coil rub issue. Usually you get rattle in the loud low notes with VC rub. I keep my big EVS laying flat while in storage. I bought an old Beckman function gen that has a .1Hz setting. The sine wave is sloppy running that slow (until I try to fix it again), but it does move the coil in and out very slowly so I can listen for coil rub, as I increase the signal amplitude. Cone cry & edge howl, & other phantom ghost notes are usually caused by the voice coil driving the cone beyond it's design damping when design parameters were set with loose flexible spiders to try to gain more sensitivity & efficiency from a speaker. If you feel gravity was in part to blame rotate the speaker 180 degrees & see if it sags back down. My climate is so dry, break in takes longer, & cone paper does not get as damp & saggy/soggy. Cones will dry rot though. (after 30-50 years) You might try doping the edges. I have another technique called strobotach for finding where a speaker is vibrating in other than the primary frequency. An old O Scope that is getting sloppy, & wont sync well, is modified to run at full intensity (brightness), & it has your sweep signal run through it as well as the amp. The speaker cone will appear to stop moving at the primary freq. You will want to take the signal off the O scope & move to using a second signal gen on the scope or if it has an internal, use it, & run at even order harmonics. You want to keep those. You can sometimes see a areas on the cone that speaker doping compound may help out. I would play it some more & see what happens before slathering doping compound on it. I check for VC rub first thing anyway with all speakers. Strobing speakers is an art I was introduced to through McIntosh in 1977, & learned about at Speaker Works 25-30 years ago. Usually cry howl & ghost notes come from the edge surrounds, corrugations, or by the voice coil & dust cap glue points. They can & do radiate inward or outward, but 97% of the time it originates from the VC or the edge. Sometimes the speaker is just what it is & sometimes it just won't work without some invasive intervention, like swapping it out, or doping it up.
Can you elaborate, explain further your strobe-tach technique for checking speakers. I'd like to try that with a problematic EVM12 I've got.... I live in Oregon which has a climate 180 degree opposite to Arizona but we've got our speaker issues too...
