Speaker/Pa/Compatibility question

68 lost souls

Hey,

I have an old set of book shelf speakers rated at 8ohms but cant find a max power rating on them anywhere. They are from an old record player entertainment system thing and I have an old PA rated for speakers between 4 and 15 ohms and max power loading 100Watts. Whats the best wat to check if I can use the speakers on the PA ok?

Bearing in mind at the moment the speakers have a 2-din plug and I would need to change that if they were compatable. I really dont wanna change it only to find out that I cant use it because I am still trying to figure out if I can fix the recordplayer system.

Thanks

Eoin Madsen

I'm not aware of any (feasible) way to measure the power handling of a speaker, but it might be something worth googling. I don't suppose you know the power output of the original system?

For CD or mastered material the risk is manageable as long as you're careful with the output. Start with the volume at 0 and turn up slowly. If the speakers start to distort or sound crap, turn it back down. I wouldn't suggest using them with any live PA source in any eventuality. The possibility of a stray transient destroying a speaker becomes rather more distinct.

68 lost souls

Thanks I thought you might be the one to respond to me. Ive soured google to no avail and I cant even find any information on the system it came from.

Eoin Madsen

If it was my own, I'd probably hazard a guess as to the power based on the dimensions of the speaker and speaker cabs - assuming I couldn't open the box and get the rating from the back of the speaker magnet.

When you say "book shelf speakers" it makes me think that 100 watts would be quite a lot of power, so it might not be a good idea if you're playing it by the numbers. Personally, I'd probably try it anyway though. :pac: But I do break things from time to time.

68 lost souls

yeah its a totally sealed box so cant chek the back of the speakers. There are 2 speakers in each cab, thinking one is like a tweeter and the other is a main. (Might be wrong terminology) I cant find any info online since tey are from the late 80s. Id say its about a 10" speaker not sure which leads me to think not rated for 100+watts.

I may try and get the record player fixed and then use them for that. Leads me to searching for freee PA speakers, the life of a design student....

Eoin Madsen

Well, I think for a hi-fi system 10" is a big enough speaker for a 2-way cabinet. But you wouldn't really know. If the box has a large volume and a bass reflex then I could certainly believe it would handle the power easily enough - you can get 10" PA speakers that will handle hundreds of watts RMS. But if it's fully sealed and reasonably small then I'm thinking best not chance it.

b318isp

They should be fine once you don't play them too loud. The amp will be rated at 100W max, but if you operate at reasonable volume, you won't create anything near this. The speakers could be anything from 5W up. If they are crappy/low power speakers you ahve little to loose!

68 lost souls

Ok I went to lidl and got a set of speakers for E15. They say 200W max 20W RMS. Will these do?

68 lost souls

Nobody has any answers? Eoin would you like to give your opinion?

Eoin Madsen

I have no idea. But a real PA with a peak of 100watts should have a higher RMS rating than 20W afaik.

Wattage can measured as:
Program power
Continuous power
RMS power
Peak power
etc.

All of these things are proportionally related. It's mathematical. 20 watts rms does not equal 200 watts peak, as I understand it. So their "max" rating could mean anything tbh.

Incidentally, cheap hifi speakers are often measured in "Watts PMPO" which is effectively any one of the above multiplied by a random number.

68 lost souls

Thanks. Ok Im guessing the only way to test this is to stick a jackon the end of the cable and test them out. If they blow they blow and its only E15. If they work then Yay.

Paolo_M

68 lost souls wrote: »

Thanks. Ok Im guessing the only way to test this is to stick a jackon the end of the cable and test them out. If they blow they blow and its only E15. If they work then Yay.

With a Prms of 20W your max instantanious power will be 28.3W and equally with a Pmax of 100W Prms will be 70.7W?!?
You sure it doesn't say 20Vrms?
This would add up, as 100W peak into 8ohms represents a Vrms of 19.9969.