blown speaker in bass cab

[Diablorojo]

Hi

I have a  Marshall dynamic bass system rig and have blown one of the tens in the cab. Can i just disconnect it and continue using it? or will this damage the amp?

TA

[Teebs]

13 minutes ago, Diablorojo said:

Hi

I have a  Marshall dynamic bass system rig and have blown one of the tens in the cab. Can i just disconnect it and continue using it? or will this damage the amp?

TA

I'm no expert, but I'd imagine that disconnecting one of the speakers will affect the impedance in Ohms (Ω) of the cab, changing the load on the amp.

This is probably not a good idea, although I'm sure someone more knowledgeable than me will be along shortly to give you the answer

[Bill Fitzmaurice]

A disconnected driver becomes a passive radiator, upsetting the tuning of the cabinet, which could result in blowing the remaining drivers.

[Phil Starr]

assuming it is a 4x10?

the speakers are most likely wired in series/parallel, ie they are wired in pairs first and then all together. this means you can only disconnect them two at a time. They are then effectively using the whole of the space they were once sharing with the other pair. This will affect their bass response and may end up with some excessive excursion/reduction in power handling. You'd be fine at moderate sound levels but not in a gig situation. 

Time to look to see if you can source the blown speaker.

 

[Diablorojo]

34 minutes ago, Phil Starr said:

assuming it is a 4x10?

the speakers are most likely wired in series/parallel, ie they are wired in pairs first and then all together. this means you can only disconnect them two at a time. They are then effectively using the whole of the space they were once sharing with the other pair. This will affect their bass response and may end up with some excessive excursion/reduction in power handling. You'd be fine at moderate sound levels but not in a gig situation. 

Time to look to see if you can source the blown speaker.

 

thanks - its a 2x10 1x15

[Phil Starr]

I'm having trouble finding the speakers, is that a 2x10 in a separate cab?

 

[Dan Dare]

Are all the drivers in the one large enclosure, or is it divided internally so the 10s and 15 have separate compartments? If they're all in the one space, they won't be doing each other any favours. Peavey did a 2x10 plus 1x15 once with no internal subdivision. It didn't work very well (the bass player in a band I used to play in had one and it wasn't great). If possible, you might look at dividing it internally.

[tauzero]

I had a 4x10 which blew one speaker without me realising. It was wired as two pairs of parallel speakers in series, and the result was that the single speaker not only got twice as much current going through it as each of the paired speakers, but because the impedance was double that of the parallel pair, had twice the voltage across it too. So it was dissipating four times the power of each of the others, and also blew, which resulted in silence and a rather costly bill which would only have been half as much had I realised.

[Diablorojo]

18 hours ago, Phil Starr said:

I'm having trouble finding the speakers, is that a 2x10 in a separate cab?

 

no its 2x10 and a 1x15 in one cab

 

[Phil Starr]

2 hours ago, Diablorojo said:

no its 2x10 and a 1x15 in one cab

 

I think my initial advice that you should only use this at moderate volumes until you have this sorted is good, as everyone is saying you may do further damage. Is this a bit of historic kit you want to keep original, something you particularly love or just an old system you happen to use? I suppose I'm asking how much money and effort do you want to spend on it?

Have you emailed Marshall?

Is this a sealed cab or is it ported?

[itu]

Some basics:

If the casing has a hole that is not designed to it, the bass response is sacrificed. In this case the blown speaker is functionally a hole, like @Bill Fitzmaurice told. The case begins to act like an open back g-word cab = no bass.

If other elements and the system is otherwise functional, the only way to fix the cab is to replace the element or block the hole. The block needs to be stiff like the rest of the casing (plywood or similar).

If the block is not airtight, the block is next to useless.

As one element is missing, the tuning of the case and the electronics (X-over) may not work like designed.

[Balcro]

From your description it sounds like you have a Marshall 1553. A bit of a strange hybrid. It has even been asserted that the drive units are really for guitar and not bass. If you wish to persevere with it, contact Celestion and or Marshall, but the cost could be startling! Good luck.

[Bill Fitzmaurice]

Pictures of the 1553 show it to be two tens and a fifteen sharing the same air space, with a port that has no ducting. Even though the drivers all share the same air space the jacks are set up for optional bi-amping. It's the kind of bizarre Mickey Mouse engineering that guitar cabs can get away with, but not bass. As it dates to the early 1980s chances are the drivers are musical instrument rather than true electric bass drivers.

[casapete]

2 hours ago, Bill Fitzmaurice said:

Pictures of the 1553 show it to be two tens and a fifteen sharing the same air space, with a port that has no ducting. Even though the drivers all share the same air space the jacks are set up for optional bi-amping. It's the kind of bizarre Mickey Mouse engineering that guitar cabs can get away with, but not bass. As it dates to the early 1980s chances are the drivers are musical instrument rather than true electric bass drivers.

Although designated as part of the JCM800 Bass series, your findings sound quite likely Bill. Here's the backplate -

 

[Bill Fitzmaurice]

It's this picture that left me shaking my head:

Cabs like that are the reason why I started building my own in 1969. There were some very well designed bass cabs back in the day, EV B115M and B215M and the JBL Cabaret series are a couple that come to mind. Nobody bought them, because they were sold as separates, and in those days you always bought the amp and speaker as a set. The largest amp manufacturers were Fender, Marshall and Vox, and their bass offerings were basically guitar amps without reverb or tremolo. The only amp manufacturers from the 60s that were first and foremost electric bass oriented were Ampeg and Sunn, and not coincidentally they had the best bass speakers as well.

[Phil Starr]

That's really shocking, even with the state of knowledge back in '69 (just before Thiele and Small) we knew better than this. The idea that we would put out something like this in 1980, well it's no wonder the UK lost it's reputation as a serious manufacturer of pro audio. 

As a speaker it isn't really worth repairing. if it's a valued piece of vintage kit you won't be able to source replacement parts easily, but someone might be able to recone the broken speaker. Only the OP can decide it that's a project you want to take on.

[stevie]

I have to wonder what progress has actually been made in bass guitar cab design since the 1960s. A modern design might split the drive units into two separate cabs - not that that will necessarily make much difference - but apart from that, this is typical of what's on the market today - a fifteen and two tens in an undamped ported cab. At least the Marshall has a bit of bracing.😀

Edited September 30, 2019 by stevie

[LukeFRC]

6 hours ago, stevie said:

I have to wonder what progress has actually been made in bass guitar cab design since the 1960s. A modern design might split the drive units into two separate cabs - not that that will necessary make much difference - but apart from that, this is typical of what's on the market today - a fifteen and two tens in an undamped ported cab. At least the Marshall has a bit of bracing.😀

My start wondering about cabs was when I wondered why my Tecamp cab sounded ok quiet but rubbish at gigs - it wasn’t far from that Marshall cab (except no driver mixing) what was crazy is they made the cab in three sizes and I think you or someone pointed out it would probably work ok in the smaller size enclosure