Whats wrong with my cab!?

Scotch11 · #1 06-18-2011, 04:23 PM

So i fired up my Mesa MPulse / PH410 8ohm the other day and noticed that the sound seems to only come out of the right side of the cab, more noticeably out of the top right speaker.

I placed my ear against the grill to try and hear if the speakers were blown and could not quite determine what was going on... I'm not sure if I'm just being paranoid and looking for a problem with it or if something is actually wrong with it.

There's no buzzing or noticeable sound that something is wrong, its just that that the sound is clearly only being projected out of the right side.

Is there anything I can do to determine if something is faulty? I have a multimeter lying around but am not really sure what to do with it

Any advice would be greatly appreciated!

Electricblue · #2 06-18-2011, 04:34 PM

Open up the back and give all of the wires a wiggle. Push the cones individually, and see if you can feel a rubbing/scratching.

Scotch11 · #3 06-18-2011, 06:04 PM

Everything looks pristine inside of the cab, speaker cones move freely with no scratching. Maybe I am just going crazy. How would I use a multimeter to determine if something is electrically messed up?

will33 · #4 06-18-2011, 07:02 PM

Pull the grill off and watch the speakers as you play. The ones that seem "controlled" are working properly, the ones that are flapping about/moving too far are either blown or disconnected. A 410 will most likely be wired series/parallel and it's entirely possible a wire may have shaken loose as earlier stated so check that as well.

Scotch11 · #5 06-19-2011, 10:07 AM

All wires look to be in good shape and are securely connected. The top right speaker is clearly working but I can't visibly tell if the other speakers are moving on there own power or just because that one speaker is pushing them. You mentioned 4x10s are wired series/parallel... I'm running my cab with my Mpulse 600 at 8ohms so the cab is only getting about 300watts, could the right side be getting the majority of the wattage and choking the left side due to the series/parallel wiring? I don't know if that makes any sense, my electrical knowledge is very limited. I'll keep staring at the thing and hopefully find a solution!

billfitzmaurice · #6 06-19-2011, 10:32 AM

Quote:

Originally Posted by will33

Pull the grill off and watch the speakers as you play. The ones that seem "controlled" are working properly, the ones that are flapping about/moving too far are either blown or disconnected. .

Too imprecise. Connect a 9v battery to the end of the speaker cable, grille removed, the cones of the good drivers will move, any dead (or disconnected) won't.

Scotch11 · #7 06-21-2011, 10:06 PM

Aha! Did the 9 volt battery trick... At first I was lazy and didn't disconnect the speakers, I just tapped the battery to the speaker terminals. I noticed some moved simultaneously, I'm assuming that's the parallel/series wiring job? I got them all to move except the bottom left speaker of the 4x10... I then disconnected that speaker and tried the 9volt again and still got no movement. I also noticed a VERY VERY slight rubbing sound on the bottom left speaker when I push on the cone (i had to have my ear 1/2" away from the cone to hear it) Soooooo JUST ONE BLOWN SPEAKER!?!!?

Can I wire the 4x10 up to operate on just 3 speakers then? With that blown speaker connected, only 1 speaker in the cab seems to work, but the remaining 2 aren't blown?... Help meeeeeeee

Never_grew_up · #8 06-21-2011, 10:33 PM

If you bypass a speaker you'll change the impedance. Depending on whether the bad speaker was series or parallel, you could drop the impedance to 2 ohms.

Mousekillaz · #9 06-21-2011, 11:24 PM

Try this:
Google: multiple speaker wiring by Wayne Harris.
I would try to understand the impedance relationship and asses the risks to the equipment. These articles refer to Car Stereo systems, but the bottom line is the electrical principles are EXACTLY the same. Wayne is a legend in the car stereo world.
I personally would replace all four drivers at this time, reason being is, most likely they have all been stressed and the weakest one failed first. The others will likely fail too. There are many good online retailers that have great products available. US Speaker being one of them. Mesa make great cabs, I do not know who makes their drivers, likely a well known brand name.
With a 4x10 configuration, 4 - 8ohm drivers wired series/parallel will result in a 8ohm nominal load which is good if you intend to ever run a 2nd cab. Likewise 4 - 4ohm drivers will net a 4ohm nominal load when wired the same way. not so good for adding a extra cab if your amp can not run a 2 ohm load.
I don't wish to sound like a blow hard, I spent twenty years engineering/building/installing in the car stereo business. so I have had the opportunity to see a lot of issues with amps and speakers that could have been avoided with some readily available knowledge.
Best of luck!

Scotch11 · #10 06-22-2011, 07:22 PM

Thanks for all the info, its a bit overwhelming but I'll see what I can do with it... Am I right to assume that all four speakers in my cab are 8hms each? I definitely cannot afford to replace all 4 speakers right now, let alone a single speaker (I'm a poor starving college student) So how would I go about wiring this whole thing up so my 3 remaining speakers work? Is my only option parallel? (8/3=2.66 ohms) I'm a bit nervous running my Mesa Mpulse600 at 2ohms even though it says 2ohm minimum on the back...

Scotch11 · #11 06-22-2011, 09:55 PM

So if i wanted to wire them parallel, can i just "daisy chain" the positive terminals together, and the same with the negatives? Or do i need a separate lead for each terminal going back to the board?

Mousekillaz · #12 08-01-2011, 01:07 PM

If your amp can handle 2 ohms safely, you could do that(8/3=2.66). It will make more power, Which will most likely send another driver to a early grave.

fenderhutz · #13 08-01-2011, 01:14 PM

Call Mesa.

Ask what you need.

They are VERY helpful.

RickenBoogie · #14 08-01-2011, 01:20 PM

+1 call Mesa. Do not attempt to use the cab with only 3 working spkrs, or risk damaging the rest of them. Either replace or recone the damaged spkr, then, in the future, watch your volume and low eq.

BassmanPaul · #15 08-01-2011, 01:27 PM

+1

Leaving a speaker disconnected will allow that speaker to work as a passive radiator and will throw out the tuning of your cabinet.

JimmyM · #16 08-01-2011, 01:38 PM

Reconing a broken speaker is an option that doesn't cost a whole lot and will bring your cab back good as new. But in the future, watch your volume or it'll be all 4 speakers next time