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Why did I blow a speaker?

Scobby Bott

Scobby Bott

Guest
Jan 23, 2012
264
8
Pottstown, PA
#1
I've been searching for a good deal on a 2x15 cab, and just the other day one came up. I went to check out a ported Sunn/Fender Bassman 2x15 loaded with brand new Eminence Legend CB158s. Despite the fact that the design of this cabinet is not optimized for these particular speakers, it sounded amazing. No shortage of the lows, tight mids, crisp highs and at a great price, so I threw caution into the wind and jumped on it. Bad idea apparently.

Today, at practice I blew a hole in one of the speakers. The output of the head I was using is well within the power and displacement ratings of the drivers, and the volume I was playing at was quite reasonable. Upon looking further into speakers, I found that Eminence recommends a 40hz high-pass filter in a vented situation to protect the speaker. Assuming that there was no prior mistreatment of the speaker, was it a lack of the recommended filter or the inefficiency of the cabinet that led to its downfall?

What I'm essentially getting at is, if I really like the sound the cabinet delivered, would it be a suitable course of action to recone/replace the driver and have the cab equipped with an HPF; or should I be abandoning this configuration altogether and be searching for a different cab/a pair of more appropriate speakers?

Thanks in advance for educating me and not trolling.:D
 
#2
Hpf is better placed in the low voltage side, before amp input, in the effect loop or between pre out and power amp in, if these jacks are present. (A speaker level hpf is massive, expensive, will be a DIY affair and robs power.)

Did you blow the voice coil assembly through the cone?
 
#4
Drivers are blown by one of 2 ways, over heating, or over excursion. Knobs on amplifiers are not a good gauge to how much power, and especially lower frequency power, your amp is putting out. And finally, a speaker must be combined with a cabinet appropriate for it. Replacement spkrs, no matter how good they may be, must be enclosed properly, and tuned to the box they're in. Knowing all this- I would never buy a used cab that's had replacements fitted, unless they were the right ones for that cab.
 
#5
The Emi CB158 is a good sounding speaker for bass. It also does well with a variety of cabinet sizes and port configurations. But, even in a perfectly designed cab, the speaker won't handle more than about 180-200 watts before it starts to fart and go into over excursion. The more low content you feed it, the fewer watts it will handle cleanly. If you were putting 400 watts into that 2X15, you were at the max. If you were putting in 400 watts with the low EQ turned up, you were over max.
 
#6
it looks like it was a mis-mathed cab to me, the reason a cone would tear is if it hit resonant frequency of itself, causing an over-excursion and too much flexing of the cone, which then leads to the failure of the driver, you should have the cab checked to make sure the drivers are compatible for the cab before continuing to repair, a professional sound tech will be able to tell a mis-match pretty quickly, there is one thing you can try if you have enough unused pillows... use the stuffing from them to fill the cab to dampen the internal vibration, this will in theory fix the issue... the physics added up when I tried it out on my small 20W micro bass, and it actually improved the tone as well... bonus!! :3
 
#7
A hole in the cone is not at all a typical failure mode due to over excursion. It implies a small area of weakness in the cone and/or a fairly tightly focused area of high pressure. Sounds to me like that driver has a repaired tear in the cone that failed. Could you describe the tear and its location? Look closely for signs of adhesive on the back of the cone.

Check the driver for voice coil alignment. Very gently push inward about 1/8 inch with fingers along the edge of the dust cap (if it is hard) or around the apex. It is highly unlikely that a cone tear due to high spl would occur without the voice coil also being out of alignment.
 
#9
AlexanderB said:
Hpf is better placed in the low voltage side, before amp input, in the effect loop or between pre out and power amp in, if these jacks are present. (A speaker level hpf is massive, expensive, will be a DIY affair and robs power.)

Did you blow the voice coil assembly through the cone?
Click to expand...

Noted, thank you. Sorry for the lack of details in my OP. The voice coil does not appear to have blown through the cone. The hole is an inch-long tear that begins at the inner edge of the surround and extends about an inch inward toward the dust cap.


Mr. Foxen said:
These two things contradiction each other.
Click to expand...

I was running a GK Backline 600 into the two 8ohm speakers wired in parallel. According to the Backline's manual, it's only capable of putting out 180w at 8ohms. Am I mistaken in that the displacement limitations of the speaker are dependent on the specific volume of the cabinet? If so, I suppose that's basically what I was asking in the first place. And is there another factor I am overlooking as well?


RickenBoogie said:
Drivers are blown by one of 2 ways, over heating, or over excursion. Knobs on amplifiers are not a good gauge to how much power, and especially lower frequency power, your amp is putting out. And finally, a speaker must be combined with a cabinet appropriate for it. Replacement spkrs, no matter how good they may be, must be enclosed properly, and tuned to the box they're in. Knowing all this- I would never buy a used cab that's had replacements fitted, unless they were the right ones for that cab.
Click to expand...

Duly noted, and lesson learned. There are two factors that make me curious to explore AstroSonic's response though: the speakers never gave any audible indication of overexertion ("farting out") and the fact that only one speaker was damaged in a small location. In your experience, are either of these details of any consequence?


AstroSonic said:
A hole in the cone is not at all a typical failure mode due to over excursion. It implies a small area of weakness in the cone and/or a fairly tightly focused area of high pressure. Sounds to me like that driver has a repaired tear in the cone that failed. Could you describe the tear and its location? Look closely for signs of adhesive on the back of the cone.

Check the driver for voice coil alignment. Very gently push inward about 1/8 inch with fingers along the edge of the dust cap (if it is hard) or around the apex. It is highly unlikely that a cone tear due to high spl would occur without the voice coil also being out of alignment.
Click to expand...

Will do. The speakers are supposed to have been brand new, but I will check for these things when I get back to the practice space, and provide a picture as well.
 
#12
Sounds like maybe the screwdriver slipped & someone poked a hole in the driver during the installation. What kind of sound was the speaker making to make you think something was wrong? Are you sure the hole wasn't already there when you bought the cab? Two of those Legends should be able to take quite a bit of pounding even without a HPF. A hole in the cone is not a blown speaker and can usually be repaired by simply patching the hole.
 
#13
Blowing a hole in the speaker sounds like the cone had a weakness. Either there was a manufacturing problem or it was damaged and repaired. It might help if you documented the issue with some pics and sent an email to the engineering department at Eminence and ask them if it is possible that the failure is due to a manufacturing flaw. Provide all the codes that are stamped onto the basket or cone. They can be very helpful. In fact, they appreciate product feedback from the field.
 

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