Help Blown Speaker!

[rennie234]

Hey all,

Got to the gig last night to find that 1 of my cabs has blown . Can anybody sugest a replacment or what I should be looking out for?

My rig consists of;

15 Band sterio graphic eq
Into a 900w head - 450w P.S. @ 4ohms
Into the Marshall MBC 410 & 115 stack

Both cabs are rated @ 4ohms, the 410 is 600w but the 115 is only 300w.

I need to replace the 15" as i think its blown because it was farting like crazy during sound check so in the end i didnt use it.
I've been looking around on the net and the only driver i can find which i think will do the job is this;

[url="http://www.lean-business.co.uk/eshop/celestion-bn15400s-4ohm-neo-magnet-bass-guitar-speaker-15-p-547.html"]http://www.lean-busi...r-15-p-547.html[/url]

Celestion BN15-400 - 400w @ 4ohms but it costs a fortune.

I've looked a a few from Eminence but they are all rated at 8ohms for some reason.

So anybody with any sugestions please give me a shout, I believe im after 450w or more @ 4ohms.


Right thats that bit, now for the complicated bit

The cab also has a tweeter in it, and i believe a crossover. Would these affect what driver im looking for?

E.g. if the tweeter is rated at 8ohms (i dont know if it is) can i get say a 500w @ 8ohm driver as long as they are wired right?

Thanks in advance
Chris

Edited November 20, 2011 by rennie234

[LawrenceH]

Hi,
The cab will be designed to work around a particular speaker. That doesn't mean you can't put an alternative in, but not any alternative will automatically do just because it is the right wattage/ohm rating. Bear in mind if the speaker is farting out, it could well be due to mechanical damage through overpowering the bass end (causing the cone to move too far physically) rather than exceeding the thermal watts rating. Also worth checking it's not something trivial like a bent grill pressing against the speaker.

If the crossover is designed to work with 4 ohm speakers, then substituting an 8 ohm driver will make it behave differently.

For a single 15 to keep up with and complement a 4x10 cabinet in your set-up then you probably do want one that has decent low-end sensitivity, is 4ohms, and can handle close to the full thermal wattage. The Celestion driver you link to is expensive because it uses lightweight neodymium magnet. If you don't mind the weight then a more old-school driver will be cheaper and give you a bit more choice. Eminence do a delta 15LF and kappa 15c that are both available in 4 ohms versions. I have no experience with either, though Eminence as a brand are fine.

To work out if they'll suit what you want a good place to start is with the size of your cabinet (in terms of internal volume) and port tuning frequency. Loudspeaker modelling software like WinISD, which uses electromechanical parameters from the driver spec sheet to simulate how the bass end will behave in a given cabinet, can then be used. If that seems like a bit much, people here can probably help with the modelling side of things. There is a lot of info already on here and on barefacedbass.com about principles of ported loudspeaker design for bass guitar which is helpful. Also useful would be the details of the speaker already in the cabinet, Marshall will probably be using an OEM version of a driver from the likes of eminence, celestion, sica/jensen or similar and if we can work out which it is, then it'll give a clue as to the type of driver will suit as an upgrade.

[brensabre79]

Marshall are UK based and are also very helpful. They should be able to supply a direct replacement or if not at least tell you where to get one.

You could contact Eminence directly. they are really helpful in terms of will this speaker work in my cabinet questions. They were great with me when I needed to find replacement drivers for my SWR Goliath ii - the OEM had stopped making the speakers ages ago.

[Mr. Foxen]

You just learned why mixing 4x10 and 1x15 is a bad plan, if you dig the sound of the 4x10, but need louder, get another one. If not, rig rethink time. Then you have to weigh the cost of replacing the 15" speaker against the sale value of the cab, considering it has a value without a speaker.

[Musky]

[quote name='LawrenceH' timestamp='1321818171' post='1443470']Also worth checking it's not something trivial like a bent grill pressing against the speaker.
[/quote]

+1

Well worth checking there's nothing untoward going on inside the cab. There have been plenty of threads where people have thought they'd blown a cone only to find it was loose damping material, poorly dressed leads or screws stuck to the magnet causing the problem.

[KimKG]

[quote name='Mr. Foxen' timestamp='1321981713' post='1445129']
You just learned why mixing 4x10 and 1x15 is a bad plan, if you dig the sound of the 4x10, but need louder, get another one. If not, rig rethink time. Then you have to weigh the cost of replacing the 15" speaker against the sale value of the cab, considering it has a value without a speaker.
[/quote]

I'm curious, why is this a bad plan? Is the 1x15 more likely to blow in this situation?

I was about to start running my rig as a 4x10 and 1x15 but I have the option to run as a 4x10 and 2x10 or 2x10 and 1x15 if either of those option would be safer.

Sorry for the hijack but I figure any information shared would be relevant.

Thanks
Kim

Edited November 28, 2011 by KimKG

[LawrenceH]

[quote name='KimKG' timestamp='1322468791' post='1451033']
I'm curious, why is this a bad plan? Is the 1x15 more likely to blow in this situation?
Kim
[/quote]

Mainly because you're asking a single motor pushing a surface area of about 850cm2 to keep up with 4 motors pushing a total of nearly 1400cm2. The 15 will probably have higher excursion capability so net volume of air capable of being moved (Vd)
will be less unequal than these numbers would suggest, but thermal power handling is likely to be greater with the 4x10. If you're playing at real cooking volume you might even fry the 15 without really noticing. Having said that a better quality/higher power 15" in the OP's situation would probably handle it. There is another issue which is whether the cabs are well-matched in terms of output phase alignment, which means using two identical cabs is often preferable if you want to ensure low-end output is uniformly louder compared to a single cab.

[Mr. Foxen]

[quote name='KimKG' timestamp='1322468791' post='1451033']
I'm curious, why is this a bad plan? Is the 1x15 more likely to blow in this situation?

I was about to start running my rig as a 4x10 and 1x15 but I have the option to run as a 4x10 and 2x10 or 2x10 and 1x15 if either of those option would be safer.

Sorry for the hijack but I figure any information shared would be relevant.

Thanks
Kim
[/quote]

The exact results of mixing are hard to predict, whereas using the same is easy to predict, same as one, but more. At some points in the back and forth movement of different speakers with the same signal they might be moving in different directions due to differences in how they respond to signal, and this shows up as inconsistent sound depending on where you are in relation to them. Additionally they might have different impedance characteristics (the 'ohms' is just a vague nominal figure', impedance is actually variable with frequency), which can put weird loads on your amp and unbalance the power. Simplest situation that can make one of your speakers die is that the happy one is being loud enough that the farting one is drowned out so you don't hear it and turn down.

[KimKG]

Thanks LawrenceH and Mr. Foxen That's very interesting information from both of you and something that for the most part I'd not considered. I had thought about a phase issue but figured there was little I could do with actually having the cabs to try them out.

I'll probably pop the 1x15 on top for the first few gigs just to see if we're getting into the danger zone. It's typically used on functions so I can't see myself hitting 'cooking' volumes but I don't want to blow anything.

Is there a formula for calculating the wattage delivered to each cab? 400w head into two daisy chained 8ohm cabs 4x10 and 1x15?

Thanks,
Kim

[Mr. Foxen]

It isn't wattage that breaks bass cabs, it is excursion, and working out that is much harder. Additionally the rating of the amp doesn't tell you much about what it is feeding the speakers. Especially since the impedance depending on frequency, in different ways for each cab means that some frequencies will be unevenly distributed.

[pete.young]

You don't say what kind of head you're using, but if it has a gain for each channel you don't have to feed the same amount of power to both cabs.

[BassBunny]

Why not just get the speaker fixed?
At least then you KNOW it is the right driver for the cab.
Wembley Loudspeakers are great at fixing drivers.