Passive PA speaker fault - no sound - any help gratefully received.

close2u

Hello all. I have just bought some pa gear and in the advert was stated that one of the speakers was blown. It is SubZero kit from Gear4Music. Basically this (plus some other bits n pieces).

https://www.gear4music.com/PA-DJ-and-Lighting/SubZero-SZPA-410-175W-10-PA-System-With-Digital-Media-Player/1O34

I have no knowledge whatever of why a passive pa speaker may become 'blown' nor what may be involved in diagnosing the fault and fixing it.

Any help / advice / suggestions gratefully received.

Thanks.

Danny1969

Put a meter on the terminals of the speaker, should measure below the stated impedance so an 8 Ohm speaker will measure roughly 5.8 ohm's or so .... if thats good check wires to crossover  ... if no reading (open circuit) then speaker coil is blown

On crossover look for protection fuses ... these are often 24V bulbs used as current limiters. If these are open circuit replace with similar 
Also look for blown ceramic resistors .... normally these are large and coated with white fire proof ceramic coating 

Check wires from cross over to input connector 

close2u

@Danny1969 ;
Many thanks for a quick and detailed response.
Sadly - it is as I feared it might be ... I honestly don't have much idea what that technical talk means and I don't have the basic equipment to test anything. Oh boy.
I can see for someone that has a few basic tools and kit such work may be common place.
Given that I don't, I'm wondering if:
a] would it be worth spending money on a repair given that they are modest price items in the first place?
b] are they saleable as a pair when one doesn't work?


[ side note:  I bought as a bit of an experiement to see if I could do without an amp in a small bedroom and just use a multi-fx and a mixer. That experiemnt is on-going and I'm considering a non-powered mixer with a pair of active monitor speakers I have. ]

ICBM

If no sound at all comes out, it's actually more likely to be a simple fault like a wire come off the jacks - while it's possible that both the bass driver and either the crossover or the tweeter are blown, it's not that likely. Normally I would expect one or the other to still work.

The first thing to do is take the jack panel off - just four screws - and see if you can see a detached wire.

close2u

@ICBM ;

Thanks a lot. The speaker is totally silent, no buzz, hiss or similar when connected.
I took the panel off - black and red wires all nicely secure in their positions. I couldn't see very well inside. I gently took hold of the black, red, green and blue wires, all gave resistance when slowly pulled so that may indicate each is also properly attached - but I couldn't see or be certain.
How do I actually get fully in? Should I even try to get in to look? Do I need to unscrew the corner mountings and more?

ICBM

close2u said:

How do I actually get fully in? Should I even try to get in to look? Do I need to unscrew the corner mountings and more?

Looking at the pics, you remove the two screws at the top and bottom centre of the grilles, then pull the grilles out - the corkscrew on a Swiss Army knife is actually good for this! - by pulling where the screw holes are so the grille flexes and becomes narrow enough to pop out from the sides of the cabinet. Then lay the cab on its back and take the bass driver out. Be careful when you lift it not to pull the wires tight.

close2u

@ICBM ;
Thanks again. Earlier on I took those two screws out, the grille seemed tight in and I didn't want to yank it if it was not supposed to come out with just those removed. I'll give it a go. Should I take the jack panel off and feed it through the hole when I lift the bass driver out?

ICBM

close2u said:

Earlier on I took those two screws out, the grille seemed tight in and I didn't want to yank it if it was not supposed to come out with just those removed. I'll give it a go. Should I take the jack panel off and feed it through the hole when I lift the bass driver out?

Yes, if the grilles do come out that way - they do on most speakers with screws like that - they can be a bit stiff.

There's probably enough slack in the wires to lift the bass driver, and if they're too short to get any more access, disconnect them from the speaker - they'll most likely be just push-connectors. Make sure you note which way round they go if it isn't obvious or labelled.

close2u

ICBM said:

... disconnect them from the speaker - they'll most likely be just push-connectors. Make sure you note which way round they go if it isn't obvious or labelled.

Thanks again. I'll take a photograph methinks ... just in case I forget 

steamabacus

Hope I'm not stating the obvious but have you checked it's definitely one of the speakers and not just one of the two output sockets on the amp? ie Does the 'working' speaker work when connected to either of the sockets (and vice versa)?

ICBM

steamabacus said:

Hope I'm not stating the obvious but have you checked it's definitely one of the speakers and not just one of the two output sockets on the amp? ie Does the 'working' speaker work when connected to either of the sockets (and vice versa)?

Or the cable...

Good work. It can be important to check the really basic stuff before disassembling the wrong thing . Speaking from experience .

close2u

steamabacus said:

Hope I'm not stating the obvious but ...

It needed stating.

ICBM said:

... Or the cable...

The cable indeed.

OMG I am such a plonker.

I took it all apart as advised. All looked fine. Everything was secure and connected. It gave me a chance to clean out some of the dust and fluff etc at least. So I thought well, let's look at the other, compare, and take the opportunity to clean that one inside too. A little more dust and fluff etc. Both looked fine and just the same.

So, I thinks - surely it's worth another try, switch things around. Lo and behold. Using the first cable neither speaker worked from either output socket. Using the second cable both speakers worked from both output sockets.
OMG and bloody hell. It was only the flipping cable that was faulty!

I simply took the seller at their word that the speaker was blown and din't even think to take it right back to basics of checking cables, connections etc. I was told that only one speaker worked and didn't think beyond it. 

There's a lesson to learn eh!

Still - it seems I may have benefited more than just learning a little lesson.

All's well that ends well.

Thanks so much everyone @Danny1969 @ICBM @steamabacus for chippinng in with your advice.

steamabacus

Glad it was something simple.

ICBM

close2u said:

The cable indeed.

OMG I am such a plonker.

Even those of us who supposedly know what they're doing get caught out like this occasionally, so don't feel too stupid .

Roland

Question one for diagnosing faults: “Is it plugged in and turned on?” In my experience this solves 90% of problems.