PA system suggestion

hey guys I’m looking to get a small PA system to use for band practices and possibly small gigs. I looked up some reviews and it seems like packaged systems would be my best bet because any power amp under $150 seem to have pretty bad reviews, where I can get a Nady RPA-4 for $200 and people seem to be happy with it. does anybody have other recommendations?

thanks

We used the Behringer PMX 2000(please…no patent morals police) for several years. $299.00 shipped at american musical supply.

It was great. we used one channel for mains and the other for monitors. Independent EQ and effects for each channel Never had a bit of trouble with it.

dave

I was looking at the Nady RPA-6 and for some reason it’s got a piezoelectric horn instead of compression cone… what do you guys think of stuff made out of piezo in general?

right now I think I need to figure out how much power I need. I don’t really have a good idea of how much sound any certain power rating corresponds to. the only concern is to have it be able to match up to the drums during practice because everything else can be turned down. I want to stay with the minimal power that can work beacuse one obviously due to the cost but two I also don’t have space to store very big things (I just have a room in my dorm) so small and compact would be better. does anyone have ideas on a ballpark of power I should be looking at? The PA will be running vocals and one guitar, and if it can handle it possibly the bass as well

I’ve narrowed down my list to

Nady RPA-4 (80W)
Nady RPA-6 (120W)
Gemsound PXA250 (250W)
Gemsound XP-350 stereo power amp + kustom speaker (depends on the speaker…)

If you are looking for something small and compact for very small venues, those Nadys look very interesting. I would suggest you go to the RPA-6 with the 120W RMS. 80W RMS is not much power.

Of course it all depends on the venue. Is it indoors, outdoors, in a bar with yelling clients, small church, etc.

A potential problem with those Nady units is the fact they are designed to sit on the floor. Usually you want the speakers at head level using speaker stands in order to be heard effectively.

The Gemsound PXA250 is a powered speaker that is designed for speaker stands. Unfortunately, it only has 3 inputs (two mic, one line).

The problem with the berry PMX2000 is that you also would need one or two speakers to hook up to it (which adds to the cost). That unit is only a mixer/amp in the form of a head. It is also hard to tweak on-the-fly because of the vertical design.

Paul

It may have a piezo element on the back of the horn, but that horn is a compression style horn. A buddy of my designs and builds speakers and his comment on piezo horns is that they have to be “tamed” in the crossover design.

Power by itself means nothing. Power together with speaker efficiency rating tells you how loud it will be. Don’t think “power”, think “volume”. The question is, how loud do you need to be? The answer to the question will be in dB SPL (decibels, sound pressure level).

Manufacturers like Nady are idiots in that they only specify the power. (Though, the truth is they get away with it because the consumers are ignorant and think they want to know the power when they really want to know the volume. But Nady doesn’t spec it.) So, we can’t help you at all without knowing that particular unit.

What is the other instrumentation, what’s the genre, and what are the other players like? “Drummer” means anything from a real quiet and elegant jazz player with brushes to a Ginger Baker wannabe rocking powerhouse. What kind of gigs are you talking about – frat parties, etc?

The guitar you’re talking about: acoustic guitar, or miking an electric amp?

Here are a couple facts to keep in mind.

- Keeping speaker efficiency constant, it takes 10 times as much power to be twice as loud. (!) That’s a 10 dB increase in SPL.
- Double the power and you get 3dB more. That’s noticeable, but not extreme.
- With 4 times the power, you get 6 dB more. It’s significant.
- You also get a 6 dB increase if you duplicate the whole rig. But that only works if the two speakers are very close together, and you can’t keep doing it because eventually the distance between speakers starts causing phase cancellation, reducing the gains. But it’s always more than 3dB louder.
- Plugging two speakers into one amp has two benefits: twice the surface area (3dB) and almost twice the watts (because you’re cutting the impedance in half). However, you have to make sure the amp is rated for the impedance you’re plugging in, or lower. (More speakers, less impedance, more power, but also more heat.)

If you want the PA to carry bass, you need about 3 times the watts. (OK, I said power doesn’t matter, but I lied.) Bass is what really sucks down the power. Those efficiency ratings I mentioned were for 1kHz tones, and don’t extend all the way down to bass frequencies.

BTW, the drummer should learn to play quietly. It’s hard, but it’s a valuable skill, and one that other musicians really appreciate. But it’s not something mastered overnight, so meanwhile you need the PA. Plus, he should be playing the way he’d play at the gig. But most drummers hit far harder than necessary, and it drives all the other instruments louder, and seriously detracts from the sound in many cases. (Gee, am I sounding like an old fart?)

Typical stage volumes for a rock or blues band are in the 100 to 110 dB SPL range, with many going well over that, to the serious detriment of the players’ ears. This is loud enough for a small venue, with only vocals in the mains. Many small venues still mike everything; I guess it makes the sound man feel important but it’s stupid because most venues are too loud anyway and miking everything just makes it sound worse. You mike everthing when it has to be done to reach a big audience – and in that case the sound is LESS good than if they were hearing the instruments directly. Sorry, pontificating again! BTW, I do like to play loud, it’s fun. But the goal should be to please the audience.

Typical stage volumes for an acoustic act range from 80 to 100 dB.

Conversational level (in your living room) is about 60 dB.

Keep in mind that the amps are rated for watts based on the ohms of the speakers. Usually they’re rated based on 4 ohms, because they can give a higher number that way! But most speaker cabinets are 8 ohms, and you need to gang two of them together to get them to 4 ohms (this is a good way to increase volume!)

Oh wow – just read the Nady RPA-6 manual. They say it’s 130W, but into 4 ohms. Yet the built-in speaker is 8 ohms, so you really only get about half that (maybe more, specs don’t say so we have to guess). Of course, though, power doesn’t matter, SPL does, and they don’t give us a clue. You have to try it out at the shop and find out.

For the GEM PXA250, the specs say 100 dB sensitivity, which is decent, and a 15" speaker, which you’ll need if it’s carrying bass too. 60lbs and no wheels, but you’re young – just keep your back straight when lifting, and avoid body twists! Here’s how the SPL math works out:

100 dB SPL at 1 watt (according to specs)
110 dB SPL at 10 watts (10 times the power adds 10 dB)
120 dB SPL at 100 watts (ditto)
123 dB SPL at 200 watts (twice the power adds 3 dB)

That’s a respectable SPL level for a PA speaker for a small venue. And with a 15" woofer, it’ll carry bass if you need it. Hopefully it sounds good too (which we can’t tell from the specs). Even if the amp is rated for 4 ohms and it’s an 8 ohm speaker, you get 120dB or so, which should be good. Remember that these levels are just 1M from the speaker, and nobody should be that close. So it’s not quite as loud as it looks.

Finally, though, you have to listen to them and judge the quality of the sound, and I haven’t heard either of these. Don’t expect the sound to blow your socks off, but you don’t need pristine sound quality for vocals (unless you’re a freaking songbird, in which case more power to you!)

hey thanks for the explainations. I’m mainly going to use the system for practices, any gigs we do that the venue woulnd’t provide PA is going to be pretty small, so again it’ll probably be just a matter of matching up to the drums. the music style is alternative/indie rock and it could get heavy occasionally. Besides 2-3 mics I’m planning to run both my acoustic and electric in the PA, the electric is going through an amp simulator pedal first. I realize the power rating in itself doesn’t exactly tell you the loudness but I thought the sensitivity of most speakers are within similar ballpark so you can kind of compare the power ratings? the typical stage volumes you gave were very helpful, so 120dB would be 4 times as loud as an acoustic performance would sounds fine for an alternative rock band. I wasn’t sure how to the interpret the sensitivity spec they gave for the PXA250, is speaker sensitivity always given as reference to 1W and assuming constant efficiency up to the max power rating? to my experience with other electronics the efficiency usually drops noticebly as power goes up

what exactly does it mean to “tame” a piezo horn? how do piezo horns perform compared to compression cones in general

I like Dave, use the PMX2000. I use 2 PR15 Peavey’s out front and 2 more as monitors sounds great in my basement and anywhere else required.

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what exactly does it mean to “tame” a piezo horn?

I’m not sure exactly, and will have to ask him next time I see him. It was during a discussion while we were building a set of speakers for me that he explained a bit of the difference between a piezo driver and a standard driver. I know he does something with the electronics of the crossover to balance the piezo with the other drivers (speakers) in the unit. I also remember him saying that if the horn is of metal construction, he also wraps some absorbant material around the outside of the small neck of the horn to dampen the harshness.

I don’t know if you already understand that the piezo driver is mounted on the end of the horn. The horn is used to disperse the sound from the piezo. Standard drivers tend to be (but not always) surface mounted.

I’m probably getting into this deeper than I should. After talking with the “expert” I may need to come back here and correct what I just said. But this is my understanding at this point.

Paul

I don’t know if you’ve been to the Carvin site, but you should check it out:

Carvin mixers

Here’s some systems:

Systems

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I wasn’t sure how to the interpret the sensitivity spec they gave for the PXA250, is speaker sensitivity always given as reference to 1W and assuming constant efficiency up to the max power rating? to my experience with other electronics the efficiency usually drops noticebly as power goes up

Good point; the other spec you need to know is the power rating for the speaker. It’s supposed to be relatively flat frequency response up to that power level. If it’s not linear up to that point, it won’t be flat at all.

As you go over the rating, you definitely don’t get out what you put in, so to speak. Good speakers have two power ratings, max continuous and max peak. The first is how much it’s good for and still sound great, and the latter is how much it’ll handle without failing or sounding like a tortured duck.

Yes, the standard is 1kHz, 1w, measured at 1m from the speaker, dead center.

Carvin stuff is great and excellent value, but they don’t seem to have a combined unit like you want, and it’s a bit above your price point.

That Learjeff guy sure says some good stuff! :)

So, it aint as much as what you’ve got, as how you use it.

Filling a room is not only about SPL, but the frequency and power distribution of that SPL within the venue; and of course as always, EQ and dynamic range play a big part in that. Small low power reinforcement units can make you a lot more audible and fill the room more than just having a more powerful two speaker PA.

So basically, it’s not a simple subject, but luckily there’s a lot of books and other info out there, so tell your sound guy to study up on it. :D

lol by our sound guy do you mean me

only if we had a sound guy

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lol by our sound guy do you mean me

only if we had a sound guy


Then fire the drummer and hire a sound man instead. :D

But seriously, a good sound man is as important as anyone else in the band. Sure, you can do it yourself, but it’s not nearly as good, especially if you’re doing bars, which is what I do mostly, and if you’re doing a set of varying types of music.

The sound man needs to be looking at the audience as well as listening to the sound of the band. If the band is playing a good table banging number, and the audience is joining in, then crank it up, make it more ‘in your face’. But if you keep that up the whole set you’ll drive people away. People in bars need a chance to tell their girlfriend that she looks purty tonignt and to order beer, and a chance to ease off for a few minutes.

But it must be a good sound man. Too many bands have someone’s girlfriend or boyfriend standing in the corner fiddling with the mixer. They can’t hear sh1t there and they don’t really know what they’re supposed to be hearing anyway, and they’re not looking to see how the audience is reacting

And you have to spend money on equipment too, a three band paragraphic EQ on a cheap mixer is OK for starters, but think about better.

If you want jobs, you need to develop a rep. And if you want a good rep, you need a good sound.

A good sound man and a good PA won’t make a crap band sound good, but he can make a good band sound even better, and a bad sound man or no sound man can make a good band sound terrible.

Cool post, Gismo. Thanks. That’s what my passion is - doing top-notch sound for great bands. And the results is very evident, even though, for me its just a passionate hobby.

The biggest problem with the sound folks I encounter, in small venues, is they mike everything and then USE all those mikes, when the drums and guitars are too loud anyway! (Admittedly, that’s the band’s fault too.)

The good sound guys are the ones who let us know when we need to turn something down!

BTW, I find a good tip for good sound is for guitar amps to be slanted back at nearly 45 degrees, so they’re nice and loud for the player. Do that and as long as the drummer cooperates by playing at a comparable level (as good drummers do anyway), then the sound guy has a LOT easier job! (And can actually use those amp mikes as intended.)

I’ve done sound too. It’s really a glorious occupation. You’re the first to show up, the last to leave, and without the chicks. If the band sounds fantastic, nobody notices you’re there. If they sound like crap, it’s your fault. Like plumbing, nobody even thinks about it unless something stinks. A tip of the hat to all good sound guys – you deserve it! :D

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The good sound guys are the ones who let us know when we need to turn something down!

And it only the good musicians that listen when they’re told to turn it down. Thanks Learjeff.

And I totally agree about the guitar amps. Angle them up so the musicians can actually hear them.

For the bass, the musician needs to stand about 15-20 feet away from the amp in order to hear it (lower freq = loonnnggg wavelengths).

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For the bass, the musician needs to stand about 15-20 feet away from the amp in order to hear it (lower freq = loonnnggg wavelengths).

Wasn’t this disicussion on here before? :D

But when I was learning to be an FOH man (and still am learning), I was told it was bad for the band to hear too much bass.

The reason being relative pitch shift. If the band, especially the vocalist, ‘tunes’ to the bass notes he’s hearing, then he’s slighty out of tune in the actual range he’s singing in.

And it seems to be true in practice too. They usually hear too much bass on stage anyway, so I don’t do anything to give them more, and I try to give them less. We usually play the same group of venues, and in the bad ones with stages in the corner of the room, I have battens with 12 inch stand-offs already nailed to the wall.

Every sound guy needs several blankets to hang behind the band, and if the band’s name and pictures are silkscreened on them, they love them too. :;):

So what I do is try to let the band hear as little as possible of the bass amp, and give the bass player plenty of his instrument on his monitor, but cut out the fundamental and lower harmonics. He’ll still hear them in his head anyway even if he doesn’t hear them from the room, and the rest of the band don’t suffer the relative pitch shift thing.

A lot of great ideas and food-for-thot to chew on. Thanks Gizmo. What do you use for a monitor for the bass? I’m having trouble convincing them to use a monitor for the bass instead of the amp itself.

Paul