Unknown speaker rating

[themickster]

I was going two PA speakers. The drivers have no markings on them, not even a faded label. Is there any way to find out their power handling? I've now been given the shared use of a 250w + 250w powered mixer. The giver doesn't know the rating.

 

[agedhorse]

Nope, not without knowing what driver it is, though there is destructive testing which would would tell you what the power handling WAS.

 

[hamertek98]

Nope, not without knowing what driver it is, though there is destructive testing which would would tell you what the power handling WAS.

.....or wasn't.

 

[themickster]

Nope, not without knowing what driver it is, though there is destructive testing which would would tell you what the power handling WAS.

I was hoping you'd answer. Thank you.

 

[Pulverizor]

I was going two PA speakers. The drivers have no markings on them, not even a faded label. Is there any way to find out their power handling? I've now been given the shared use of a 250w + 250w powered mixer. The giver doesn't know the rating.

If you can post a photo of the bins, front and back, someone might recognize them.

 

[sokolasty]

Before you start using them, measure DC resistance in order to define how many ohms these are. One can assume either 4 or 8 and the former assumption is safe for SS amp but not for tube one.
AFAIR DC resistance shouldn't be lower as 0.8 times the impedance.

 

[agedhorse]

The DCR can be as little as 60% of the nominal impedance depending on the VC inductance and the cabinet’s acoustic impedance contribution.

 

[Redbrangus]

I'm not clear about this: are you playing through two PA speaker systems (cabs)? Or two drivers (speakers) out of some PA speaker cabs? If it's the former, are there any brand-name IDs or manufacturer's markings on the enclosures themselves? Are there horns and drivers, or some other sort of HF components? Do they have 'rat fur' on them? (Always a sign of quality ) And what sort of powered mixer is it? If your speakers are 8Ω, and your powered mixer is rated for 250 watts at 4Ω, then your mixer is only going to develop ~125 watts per channel with that 8Ω load.

I'd say, generally speaking, even un-branded, or store-branded 'CGM-type' generic PA speakers would be fairly safe to operate with a 250-watt-per-channel powered mixer for PA use, which is to say vocal or acoustic instrument reinforcement. For use in bass instrument amplification? Nope -- not for anything louder than individual practice volume. Unbranded speaker systems are almost always built with the cheapest, lowest quality loudspeaker components and typically don't perform very well even when operated within their intended scope of operation. I really wouldn't expect much from them when you start playing a bass through them, even with only a modestly powered amp behind them, which is what you have. As always, just IMHO/IME, of course.

 

[B-string]

Unless you're into some Nickleback vocals you are not going to enjoy the vocals much of a small PA with a bass guitar at volume. YMMV

 

[beans-on-toast]

A reconer might be able to tell you something about the speaker. They would look at the frame to possibly identify the manufacture. The coil wire gauge that comes out to the terminals, the coil diameter (heat dissipation), the cone weight all offer indications as to the suitability for use as a bass instrument speaker.. Finding the literature on the PA cabinet might provide power handling capability of the cabinet.

Of course, try it and see. All manufacturers determine what power level a speaker can take by blowing it.

 

[agedhorse]

Can’t see the wire gauge of the VC, diameter doesn’t really mean much either, etc.

All of the important information is in the details that can’t be seen.

 

[beans-on-toast]

@themickster It might help if you posted an image of the back of the speaker.

 

[themickster]

@themickster It might help if you posted an image of the back of the speaker.

It might be, if there were any markings. The backs are bare metal.

 

[themickster]

Before you start using them, measure DC resistance in order to define how many ohms these are. One can assume either 4 or 8 and the former assumption is safe for SS amp but not for tube one.
AFAIR DC resistance shouldn't be lower as 0.8 times the impedance.

8 ohms

 

[beans-on-toast]

It might be, if there were any markings. The backs are bare metal.

It isn’t about markings, the frame and magnet could give an indication of the manufacturer.

 

[Hoochie Coochie Man]

Nope, not without knowing what driver it is, though there is destructive testing which would would tell you what the power handling WAS.

That is how, (according to the designer Harvey Gerst) the power handling rating for the JBL D130/140F speakers were determined when they were going to be marketed for MI rather than HIFI use back in the 1960s.

 

[agedhorse]

That is how, (according to the designer Harvey Gerst) the power handling rating for the JBL D130/140F speakers were determined when they were going to be marketed for MI rather than HIFI use back in the 1960s.

Yup, that’s how they came to the derating factors for MI applications when developing speakers for Fender. This was back in the days of paper bobbins where thermal failure was more prevalent.