Hi All,
I have a friend who's son is starting a band and he's trying to put together a cheap PA just for a bit of foldback.
To save money he wants to use a couple of KEF speakers he already owns with the little powered mixer he's getting for them.
The speakers are KEF Q55 150W 6 Ohms each. The mixer is a SubZero SZ-PMIX4 from Gear for Music's website, which shows the output on the back plate as 8 Ohms.
It also shows the output of the mixer as 175W peak.
Do you think the speakers will work on that, he's worried about blowing them but doesn't want to have to buy passive speakers at this stage if he can avoid it, while this is just a bit of fun for the youngsters while they're starting out?
I have a friend who's son is starting a band and he's trying to put together a cheap PA just for a bit of foldback.
To save money he wants to use a couple of KEF speakers he already owns with the little powered mixer he's getting for them.
The speakers are KEF Q55 150W 6 Ohms each. The mixer is a SubZero SZ-PMIX4 from Gear for Music's website, which shows the output on the back plate as 8 Ohms.
It also shows the output of the mixer as 175W peak.
Do you think the speakers will work on that, he's worried about blowing them but doesn't want to have to buy passive speakers at this stage if he can avoid it, while this is just a bit of fun for the youngsters while they're starting out?
It's not that they won't 'work' with the mixer, the problem here is that they are very inefficient at converting electrical energy to acoustic energy, ie they just won't be loud enough to keep up, so will likley be pushed until they emit the magic smoke. Loudspeakers designed for PA use tend to be way more efficient with other design compromises to suit their intended use.
At 91db efficiency those speakers might be just about OK, but it would be loud hifi levels not PA levels. That might prove to be adequate for guitar / keyboard / vocals in a relatively small room but no good for bass. That mixer amp ultimately will have the same limitations even with passive PA speakers, it's just not that powerful. Again might be Ok for midrange and up elements but any bass will need something else. Assuming the bass guitar has its own bass amp and the drums dont need to be mic'd then it might be workable.
I guess it also depends on the style of music. I'm not sure how long the speakers would last with a load of distorted guitar ragging through them. I haven't checked the detail of that mixers spec, but at a bullet point spec level I see no mention of limiting or compression, which could be a real problem as live sound can be intensely dynamic. Assuming the amp and speakers will be already working hard it will leave little overhead for sudden increases in level not kept under control by compression or limiting.
I guess it also depends on the style of music. I'm not sure how long the speakers would last with a load of distorted guitar ragging through them. I haven't checked the detail of that mixers spec, but at a bullet point spec level I see no mention of limiting or compression, which could be a real problem as live sound can be intensely dynamic. Assuming the amp and speakers will be already working hard it will leave little overhead for sudden increases in level not kept under control by compression or limiting.
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Frontman,
I'd seriously consider selling or trading those Kef speakers for some half-decent PA speakers.
PA speakers deal with frequent abuse, and usually survive. For example, a squeel of feedback is usually perfectly fine for PA speakers with suitable power handling etc. The dome tweeters in the Kef speakers would likely stop working almost immediately. Dome tweeters have very little thermal mass, and would die quickly in the event of high-frequency feedback. The complete speaker might survive 150w, but that tweeter won't stand more than about 10w on its own. Hint: when feedback happens, lots of power is delivered at the feedback frequency.
FWIW, for band use, I typically use 1x stage monitor per musician. It's usually an old-school 12" 2-way box in the 300W RMS range, with about 700w per box on-tap. Those are usually enough for most bands, but I have had instances where more output would have been useful.
I don't know how loud your son's band is or will be, but my recommendation would be to save up a bit more cash, and put it towards something that will be useful long-term. I often recommend a Yamaha DBR10 as the minimum PA speaker that's still worth having. Any cheaper/lower-grade than that, and I promise it's not worth having. I took mine to show a band in their rehearsal room. They had a SubZero 15" 2-way speaker already, and it was really awful. Not as loud as the size would suggest, and sounded really very rough. The Yamaha demolished it in all regards.
If you're near Sheffield and would like me to take a look, you're welcome to get in touch. I might even have some old gear around here that I'd be happy to move along for a good price.
Chris
I'd seriously consider selling or trading those Kef speakers for some half-decent PA speakers.
PA speakers deal with frequent abuse, and usually survive. For example, a squeel of feedback is usually perfectly fine for PA speakers with suitable power handling etc. The dome tweeters in the Kef speakers would likely stop working almost immediately. Dome tweeters have very little thermal mass, and would die quickly in the event of high-frequency feedback. The complete speaker might survive 150w, but that tweeter won't stand more than about 10w on its own. Hint: when feedback happens, lots of power is delivered at the feedback frequency.
FWIW, for band use, I typically use 1x stage monitor per musician. It's usually an old-school 12" 2-way box in the 300W RMS range, with about 700w per box on-tap. Those are usually enough for most bands, but I have had instances where more output would have been useful.
I don't know how loud your son's band is or will be, but my recommendation would be to save up a bit more cash, and put it towards something that will be useful long-term. I often recommend a Yamaha DBR10 as the minimum PA speaker that's still worth having. Any cheaper/lower-grade than that, and I promise it's not worth having. I took mine to show a band in their rehearsal room. They had a SubZero 15" 2-way speaker already, and it was really awful. Not as loud as the size would suggest, and sounded really very rough. The Yamaha demolished it in all regards.
If you're near Sheffield and would like me to take a look, you're welcome to get in touch. I might even have some old gear around here that I'd be happy to move along for a good price.
Chris
Thanks for all the advice guys, it's much appreciated.
I should've explained more clearly that I think he's only looking to use the speakers / amp for vocals, so the lads can hear themselves a little over the drums / guitars. This is just a converted loft room with some limited sound proofing, so we're not talking anything too loud happening (although I'm sure we can guess that it might occasionally get too loud when they get silly).
If he wants to give it a go, just to start them off, then I guess he just connects the speakers straight to the 2 outputs and see's what happens?
He'll spend on some proper gear once the kids have shown they'll carry on but you know what kids can be like for starting something then not carrying on!
I should've explained more clearly that I think he's only looking to use the speakers / amp for vocals, so the lads can hear themselves a little over the drums / guitars. This is just a converted loft room with some limited sound proofing, so we're not talking anything too loud happening (although I'm sure we can guess that it might occasionally get too loud when they get silly).
If he wants to give it a go, just to start them off, then I guess he just connects the speakers straight to the 2 outputs and see's what happens?
He'll spend on some proper gear once the kids have shown they'll carry on but you know what kids can be like for starting something then not carrying on!
Anytime with a microphone feedback squeal can occur. Also a mike can be dropped or the cord can be pulled out, causing a big bang. If you could get into the speakers, you could install incandescent bulbs series the tweeters. Something like a 12 v dashboard lamp, the bulbs sold for real PA speakers limit at 50 or 70 watts. Or install a PTC resistor fuse series the tweeter, something like a 1/2 amp or so. These aren't used in real PA speakers because they trip point moves as they are used. But for this home use, there won't be that many cycles as a real bar band incurs. PTC fuses reset as soon as the power goes off and they cool down.
I've used home speakers for church PA, but the KLH23 had a 3" paper cone tweeter. Much more tolerant of overpower than a silk dome. 3" cone tweeter costs about $2 if you want to build a 2 way in a trash box from the charity resale shop. Crossover in the KLH23 was one film capacitor series the tweeter. Woofer was a 10".
I've used home speakers for church PA, but the KLH23 had a 3" paper cone tweeter. Much more tolerant of overpower than a silk dome. 3" cone tweeter costs about $2 if you want to build a 2 way in a trash box from the charity resale shop. Crossover in the KLH23 was one film capacitor series the tweeter. Woofer was a 10".
With 91db efficiency I would call them silent speakers. Keep them for Your living room and buy some PA speakers.
You say that, but my Hifi speakers are 92db and coupled with the 140 watts rms input (speakers are 200 watts rated) they create a huge amount of noise. They would do in the absence of anything else but I would agree they arent really fit for this purpose, not because of the levels, but more the ability to handle uncontrolled / unknown live input.
A simple experience. One channel Your KEF speakers. Another channel a good known brand (not Ibiza Sound or similar) PA speakers with 100dB sensitivity.
You´ll hear the difference. The KEF will be silent compared to the other.
You´ll hear the difference. The KEF will be silent compared to the other.