PA speakers blown?

[flyfisher]

We have a Yamaha stagepas vocal PA that we use for small gigs or as monitors when using our larger PA.

It has recently started to sound distorted through both speakers so I assumed it was a mixer/amp problem. Finally got around to investigating it properly this evening and it's actually both speakers that are knackered and the mixer/amp works fine into different speakers.

I've removed the speakers and when I move the cone gently by hand I can hear a rubbing noise which I'm guessing is the voice coil rubbing against the magnet. I've only had one speaker blow, a long time ago, and the voice coil was completely blown, but this one is still working but very distorted, presumably because of the rubbing.

I'm curious about how this could have happened, especially to both speakers. Presumably they've been over driven and the voice coils have overheated and become physically distorted, causing them to rub. Is this sort of thing a common failure mode? Or could it be something else?

The PA is at least 10 years old and has not always been treated well, but it has survived for so long that I wonder why the speakers have suddenly given up together.

[flyfisher]

So replacement speakers from Yamaha are £77.38 each - and I need two of them

This seems pretty expensive for an 8-inch, 200W, 4 ohm speaker.

Any suggestions for a good place to buy an equivalent speakers?

Are the mounting holes standardised between different manufacturers>

[Dad3353]

[quote name='flyfisher' timestamp='1412338916' post='2567967']
So replacement speakers from Yamaha are £77.38 each - and I need two of them

[color=#800080]That's £15 a year. Not so bad when spread out..?[/color]

This seems pretty expensive for an 8-inch, 200W, 4 ohm speaker.

[color=#800080]They're not the only spec to consider. Frequency response..? Efficiency..? Cheaper speakers exist, almost certainly, but they may or may not give satisfaction.[/color]

Any suggestions for a good place to buy an equivalent speakers?

[color=#800080]Not really; not familier with UK market. T'bay would be a start..?[/color]

Are the mounting holes standardised between different manufacturers

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[/quote]

In general, eccentric cones are caused by over-heating and/or damp. Often by running too hard (over-loud, or badly ventilated, clogged with accumulated dust..?) or by poor storage (Back of a van over a hot summer week-end..? Over-wintering in un-heated garage..?). Sometimes, but not often, they may be cured by re-centring (search Utube for videos...), but replacement or re-coning is the usual remedy. Strange that both should 'flake out' at the same time, unless it's by over-enthusiastic usage, I should think. They're good units, and 'wear and tear' can be expected, whatever the gear, so should be worth repairing. Tough break, certainly, but a bullet to be bitten..?
Hope this helps.

Edited October 3, 2014 by Dad3353

[flyfisher]

That's a good bit of perspective - £15/year makes it sound a lot more reasonable.

I agree about cheaper speaker units though and it was already a concern that I could mess about finding something that physically fits but without knowing if it would give good results. You're right that the Yamahas are decent bits of kit, so this might be a false economy.

I'm pretty sure it must have been an overheating problem as the units have always been stored in someone's house rather than a damp shed, plus they were very clean when I dismantled them.

Our acoustic guitarist has taken to playing through this PA using a DI box this year, so I'm wondering if that might have caused the problem. It's the only recent difference in the way the PA has been used over many years, which has otherwise been used only for mics.

Thanks for the thoughts - I reckon you're right about biting the bullet.

[stevie]

That's a lot of money for a pair of 8" drivers. You could buy a superior, modern neo 8" driver for less than that, but the 4-ohm impedance is problematic. A recone would probably cost half as much as a replacement driver and may be your best bet. Ask the reconer to tell you what caused the damage. They will be able to tell when they have removed the old cone/coil.

[flyfisher]

I've not had any experience of re-coning and have always though it a bit of a specialised job only worthwhile for particularly valuable speakers.

TBH I'm not entirely sure about the 4 ohms.

I've also been told this afternoon that the PA isn't really a Stagepas300. Apparently, it WAS a Stagepas 300 but the mixer/amp unit failed so they replaced it (before my time) with a Yamaha EMX-212S mixer amp and used that with the Stagepas 300 cabs.

I've found the Yamaha specs for the mixer/amps but not the speaker cabs themselves.

The Stagepas amp/mixer docs state 150+150W (max) into 6 ohms (at 10% THD) or 100+100W (max) at 1% THD.

The EMX mixer/amp states 220W into 4 ohms or 130W into 8 ohms.

So I'm now unsure of the speaker specs, but if they were originally intended for use with the Stagepas amp then the EMX amp might have been a bit too much for them . . . . though odd that they lasted so long before deciding to both die.

Seems we could buy a pair of new passive PA cabs for about the same price as repairing the Yams, though I'm not sure about how they would compare.
Something like this?
[url="http://www.thomann.de/gb/the_box_pa110_fullrangebox.htm"]http://www.thomann.d...ullrangebox.htm[/url]

Perhaps just sell the EMX mixer/amp and buy a small non-powered mixer to use with our Mackie SRM actives?

Decisions, decisions.

Edited October 3, 2014 by flyfisher

[stevie]

I can't find any specs for the speakers anywhere. As it's a complete system, it's very likely that they are 4 ohms as you suspect, which makes it difficult to replace the driver with something equivalent. You could always take a driver out and check - just in case. The impedance will be marked on the driver. If it is 8 ohms, there are plenty of relatively inexpensive drivers available from companies like P.Audio.

[flyfisher]

Yes, strange isn't it - perhap Yamaha doesn't sell the speaker cabs separately?

Anyway, I've got one of the speakers out and there is no ohm marking anywhere that I can see.

The only markings are:

[b]Yamaha[/b]
[b]410403[/b]

[b]CHINA[/b]
[b]7H801J[/b]

Perhaps there is a clue there for anyone who understand those numbers?

I've measured the DC resistance as 5.4 ohms so I'm thinking it's an 8 ohm impedance?

[Dad3353]

[quote name='flyfisher' timestamp='1412359584' post='2568289']...
I've measured the DC resistance as 5.4 ohms so I'm thinking it's an 8 ohm impedance?
[/quote]

Yes, that would be right. It's probably worth changing the speakers, rather than the whole system, unless you particularly want/need to upgrade for any reason, imo.

[lurksalot]

[quote name='flyfisher' timestamp='1412359584' post='2568289']
Yes, strange isn't it - perhap Yamaha doesn't sell the speaker cabs separately?

I've measured the DC resistance as 5.4 ohms so I'm thinking it's an 8 ohm impedance?
[/quote]

The stagepas comes complete I thought doesnt the amp/mixer fold into the cab box or something like ?

The spec you quoted was 150W into[b] 6ohm[/b]s , could that be relevant with regard the speaker resistance?

[stevie]

Sounds like you're in luck, flyfisher. Have a look at the 8-inch drivers on the Blue Aran site. This one: http://www.bluearan.co.uk/index.php?id=PAUE8200N&browsemode=manufacturer is very nice if you want to go for the lightweight option. Good price too, and it takes a lot of hammer. I could lend you one to try if we can sort the logistics out.

[flyfisher]

[quote name='lurksalot' timestamp='1412360590' post='2568303']
The stagepas comes complete I thought doesnt the amp/mixer fold into the cab box or something like ?

The spec you quoted was 150W into[b] 6ohm[/b]s , could that be relevant with regard the speaker resistance?
[/quote]

The Stagepas mixer/amp fits into the rear of one of the speakers but can also be removed for ease of use. It makes for a very easy to carry vocal PA. Seems that this original mixer broke before I joined the band and they replaced it with a Yamaha EMX-212S mixer/amp, which is a slightly larger unit about the same size as one of the cabs, making three units to carry (though not a big deal as they are all fairly compact).

The 6 ohm spec I quoted was from the EMX manual about the amp output power, which is a bit odd to specify at 6 ohms, so might be a bit of a red herring as far as the cabs are concerned.

I see your point about the DC measurement of 5.4 ohms being very close to 6 ohms, but I don't think resistance and impedance would be so close, hence my guess at the actual speaker cab being 8 ohms. But it's all a bit of guesswork at this stage.

[flyfisher]

[quote name='stevie' timestamp='1412364509' post='2568356']
Sounds like you're in luck, flyfisher. Have a look at the 8-inch drivers on the Blue Aran site. This one: [url="http://www.bluearan.co.uk/index.php?id=PAUE8200N&browsemode=manufacturer"]http://www.bluearan....de=manufacturer[/url] is very nice if you want to go for the lightweight option. Good price too, and it takes a lot of hammer. I could lend you one to try if we can sort the logistics out.
[/quote]

Thanks for finding that. It should certainly be more rugged than the blown ones, which is good!

My immediate concern is the 3KHz spec as the manual I've seen says that the crossover operates at 4kHz, but I'm not entirely sure if this is particularly relevant without knowing what the roll off of the crossover might be. Anyway, the amp has low/mid/high controls so that's probably enough to compensate . . . we're not talking precise hi-fi here!

Might be worth a try for £59, although a genuine replacement is a bit less than £20 extra, so is it worth the risk? I sense a band meeting coming on!

Many thanks for the suggestion though - plenty of food for thought.

[Phil Starr]

My view is that it probably isn't worth swapping speakers around, buy the Yamaha replacements or give up on them. I'm a fan of the Stagepas 300 as a generally well engineered niche product, now widely copied. We used some as stage monitors for years and I picked up one of the little mixer amps (someone else with blown speakers?) on ebay which I still use for rehearsals and carry as a get you out of trouble amp for all our gigs.

Any different speaker is going to change the sound, though the one Stevie found looks a good un. The P Audio does have output at 4kHz but it is going to behave differently in the crossover region and sound different, it looks like it is a bit louder too so the sound is going to be bassier than you are used to. It may, or may not physically fit and adapting a plastic cab isn't straightforward. Finally the cab is ported and tuned to the speaker it carries, again the new speaker might work well or might not. Too many variables to gamble on to make saving £40 seem like a good bet.

So the question is whether it is worth spending £150 on repairing them or whether you would be better buying something else, as you have a perfectly decent mixer amp. Andertons have a B-stock Stagepas for £250 [url="http://www.andertons.co.uk/active-pa-speakers/pid35598/cid627/b-stock-powered-300-spkr-passive-500-speaker.asp?"]http://www.andertons...00-speaker.asp?[/url] for instance. Or you could buy a couple of new speakers like these for instance [url="http://www.bluearan.com/index.php?id=WRFTITAN8P&browsemode=category."]http://www.bluearan....emode=category.[/url] Repairing the yamaha's if you like them a lot isn't a daft decision but it is worth thinking about what you want to get out of this since you will have to spend £150 anyway.

Edited October 6, 2014 by Phil Starr

[Dad3353]

Devil's advocate to the above, if I may..? Worst case £150 is still less than £250, and there's a certain satisfaction in not 'wasting' stuff and discarding, rather than achieving a satisfactory repair. There are limits, of course, but if the cabs are otherwise in good enough condition, a new pair of speakers will make them almost like new, ready for at least another 10 years of service, if properly used.
Not quite the same debate if they're to be sold on, or no longer serve their purpose, maybe, but if they were good before, they'll be good afterwards, surely..? I would agree that swapping out for different drivers would be a risk; is it worth the potential benefit (or detriment...) for the relatively minor gain..? I'd put in original drivers, but it's not my credit card. [size=4] [/size]
[size=4]To be continued..?[/size]

[flyfisher]

Not to be continued for much longer.

The weekend band meeting decided on replacing the blown drivers with genuine Yamaha replacements and I'll be ordering them later today. The final rationale was along the lines of Phil and Dad's posts above - repair them as new or scrap them and buy something else, but they are good quality units and we don't like scrapping stuff. We're in for a minimum £100 for new drivers that would give unknown results so the extra £50 for genuine Yamaha units seemed worthwhile for the peace of mind. Anyway, the decision is now made.

Thanks for all the suggestions - very helpful to talk these things through.

[Dad3353]

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[3below]

When you get the new drivers, before you fit them, check if they state the dc resistance. If not, measure dc resistance and permanent mark on them. You never know in 14 years time ........... by which time PA mixers / power amps will be the size of a laptop / slab and speakers ???

[flyfisher]

Not a bad idea.
When I ordered them earlier today, I asked about the specification and they said they are usually stated in the parts manual, but when the chap tracked down the part number he said there was no actual spec given, just the part number, which he said was unusual. So I'm still no wiser about the actual spec, even though I'm buying the 'proper' replacements.

Oh well, at least they worked out a bit less than the price I was given last week. £143 including the chancellor's cut and delivery.