Choosing correct cab drivers

[bpbpbp]

Hi,

I'm hoping a kind soul will help me with a technical grey area in my life - not women no, but Bass speakers!

I run a project studio and some people rehearse here. In the last year someone has blown three cab drivers:

- Marshall JCM 800 Bass Series 100w tube head into a custom 2x 15" 16 ohm wired in series Carlsboro Powertone drivers, rating unknown
> Both are farting with reasonable bass tone level

- Trace Elliott GP7 SM 300 combo 280w RMS / 500w Peak with Celestion C15H-200 8ohm driver
> Some small tearing in places. A glue repair worked for a week or two only

- Carlsboro solid state 100w head into Soundlab L041F 4ohm 15" 400w 'max power' rating (peak I presume)
> General distortion, can't see any tears but it's damaged alright

Questions:

* Is the Marshall head 100w peak or RMS?
* Can anyone recommend replacement speakers for the Marshall and the Trace that will be a 'heavy duty' upgrade to prevent further damage?

I don't know if someone is running a synth bass sound through the cabs or what as no-one surprisingly has owned up to the damage, so I'm hoping overrated drivers will be a solution?

Best,
Benny

[Dad3353]

Sorry, just thought I'd get that one out of the way...

I'm not expert enough to help much, but I would say that the Marshall head will blow almost any speakers, if cranked and abused. A pair of solid 4 x 12 cabs will hold up for a while, but 'back then', even they would often 'blow'. How about a noise limiter in the room, which cuts the juice..? If your blokes turn up too loud... black-out. Not a solution..?

[Phil Starr]

honestly if you are running a practice studio with all sorts of people using stuff then I wouldn't start here.

The Marshall tube head will be 100RMS but a valve head will be more liable to damage with every Tom, Dick and Harry playing with it and probably has good second hand value.

I think those Carlsboro speakers are very old Fanes rebadged and aren't probably worth trying to fix.

You can probably repair small tears with copydex and some tissue paper, layering the tissue up with the latex based adhesive like fixing a bicycle puncture. Other adhesives won't really work. you need something flexible.

Your best bet on a budget would be to go for something old and heavyweight, which most bass players are getting rid of. Old Peavey stuff is pretty reliable and goes for peanuts because of it's size and weight but in a studio where you don't want it moved it's ideal. Sounds OK too. You'll probably pick up a working cab for less than a reliable new 15" driver.

[luckydog]

My humble experience of blowing bass drivers is that it is mostly amp faults that do it - followed by excessive cone excursion (ie voice coil hitting the end stop), followed by self-destruct of voice coil spontaneously coming unglued from cone.

Amp faults - DC offset faults normally, or squeals that only bats can hear...

Cone excursion - underpowered amps clipping and producing weird and unnatural subsonics, or badly eq'd amps producing deep subsonics at high levels, or badly matched drivers and cabs handling subsonics with much cone flapping........

Self destructing voice coils - cheap drivers.

Ah the halcyon days of Johnson & Jones speaker repairs in Dalston - anyone remember them ? I was a regular customer back in the day.........

LD

Edited May 9, 2016 by luckydog

[bpbpbp]

Thanks fellas! That is great feedback.

I will look at replacing the Trace cone and keep the Marshall for recording and gigging.... on which note, I need to source a pair of heavy duty 15" cones to fit in the Marshall cab that will hold up to the Marshall head.

Any suggestions?