June 2, 2017 at 6:06 pm #2568761
Hi guys, I am thinking of getting a PA system. I was reading the editorial on “Beginners guide to pa systems” and have a few questions.
Lets say Im looking at 100 people so I think 500 watts should be good. Now is that cumulative lets say four speakers at 125(lets say) or each speaker has to be 500 watts. I also want subwoofers. What wattage should they be and the amplifier. I know it has to be more than the speakers but not too high so what is an appropriate wattage for the amp. Hope I dont sound too confusingJune 2, 2017 at 11:33 pm #2568801
Your budget will dictate a lot and dependent on how heavy your tracks are you might be able to get away without a sub.
This is all my personal preference but for a group of 100 where I’d be playing bass heavy track (EDM , hiphop, etc.) I’d probably do two 10inch tops and an 18inch sub.
Your probably better off 10 watts per person for tops and 20 watts per person for bass. Just to be safe 🙂June 5, 2017 at 3:17 pm #2569101
thanks manJune 5, 2017 at 10:09 pm #2569241
Chuck Van EekelenModerator
In my personal opinion, you can add the wattage of the subwoofers to the total wattage when it comes to calculating the average group size you could cover. In that scenario I would agree with a 10W (RMS!) per person indoors to get a good volume going without pushing your PA too hard.
The other thing is that Wattage is only part of the equation. The other part is the effectiveness of the speaker, usually rated as SPL (Sound Pressure Level). It’s the amount of dBs a speaker produces (pink noise) at 1 meter from the speaker when fed 1 Watt of RMS input. Another measure is the max. SPL, which is the amount of decibels produced at maximum amplifier output (often the point just before the limiter/protection kicks in).
Why are those important? Let me tell you a bit about our ears. We don’t hear in a “straight” line. Our hearing is logarithmic, meaning it has a curve, instead of a line.
If you were to double the amp power, that would get you a 3dB increase in volume. This is just above the level a human ear can tell the difference. However, it takes 10dB for your ears to perceive it as TWICE as LOUD (+10dB). That requires 10 times the amp power!
Ok, now add the fact that sound loses 6 dB! (which is 4 times the amp power) for each doubling of the distance.
This is why it actually IS a good idea to have 4 speakers firing inward to the center of the dance area, instead of using two up front by the way!
Your dancefloor is 20 meters deep and start 1 meter from your speakers. Your speakers have a 125dB max. SPL at 1 meter. Let’s also assume the 103dB at 10meter maximum “rule” (depends on local rules, laws, regulations).
Half the distance = 5 meters = 103 + 6 = 109dB
Half again = 2,5 meters = 109 + 6 = 115dB
Half again = 1,25 meters = 115 + 6 = 121dB
At 1 meter this means you would be running very very close to maximum on your speakers all night long. And still the people at the back of the floor would be listening to sound with a level of (double 5 = 10, double 10 = 20, total deduction of 2x 6 = 12dB) 103dB -/- 12dB = 91dB. 90dB is the inside of a bus!
Should you use 4 speakers, you could have 103dB in the center, getting stronger in all directions moving closer to one of the 4 speakers, instead of the strong tapering off in a 2-speaker front setup.
1) Amp power (Watts RMS) doesn’t tell the whole story. You need massive power increase (10x) to make things sounds twice as loud to the human ear (+10dB).
2) Speaker efficiency counts. How much dBs does the speaker produce based on the amp input. If a speaker gives you 5dB more of SPL, your are halfway to that 10dB increase.
3) Using 4 speakers on the corners does indeed give a more even volume spread, contains the sound on the dance area more and you can keep your speakers a tad lower than full force.
Back to your example of 100 people, that would mean about 1.000Watt RMS. Let’s say you have two subs and 4 tops, I’d say about 150-200W per top and somewhere in the 300-400 range for subs. You won’t need that much, but low end requires a bit of amp power to move those bigger speakers. Also don’t try to get 18″ subs with only 300W. You are better off with 12″ at that amp level. An 18″ sub driven by a 200W amp is like a lame duck.
If money is no option, you could look at the RCF EVOX 5. Great sound, great sound dispersion (front-back spread) due to array-like tops, small, compact and highly portable. At 400W a piece, if you have 2 you can do an easy 80-100 people. Go for 4 and it’s up to 150-200 people very comfortably.
Final point I’d like to make, if you want serious bass, the kind you can feel in your gut rather than hear, all the previous stuff goes out the windows and you will need to get some very serious subs (18″ with matching amp power). At the end of the day that much low energy is all about moving vast amounts of air. That means big drivers with lots of power. Question is, if you have a 100 people party, is that what you and (more importantly) what they want? I have been to house parties with 15″ tops and 18″ subs in a living room blaring in my ear at 6 feet away. Not fun, I left within 30 minutes.
Lots of text, but I thought maybe some other people struggling with this stuff might be helped by this. Hope your are too.June 6, 2017 at 5:27 pm #2569651
Thanks man. already copied everything to my notesJuly 21, 2017 at 4:54 pm #2593231
Another question. If I have an Active sub and i want to connect a pair of passive midrange speakers to the sub but im concerned that the sub output cant push the midrange speakers, could I place an amp between the powered sub output and the passive speakers?July 22, 2017 at 11:01 pm #2593541
Chuck Van EekelenModerator
An active sub only has an amp for the sub. The high-pass outputs just send the XLR signal on minus the very low frequencies. From there you either go into an amp and then to passive speakers (not what I would recommend) or to active speakers (often called “tops” or satellites).
So yeah, you would HAVE to place an amp between sub and passive speakers, but easier to use active speakers. Lot less cabling too.July 24, 2017 at 8:25 am #2593751
As recommended by Vintage, I’d advocate going for powered speakers…
There have been quite a few models put out lately that are way beyond what most amplifier and passive speaker setups can do as far as EQ options, and other flexibility that is built into the DSP in the active speakers.
For instance, I have a pair of EV ZLX 12″ powered tops as part of my setup. These have proved very flexible for a number of different scenarios, put out quite a bit of sound for their price, are easily portable, and to me they offered a great compromise between the budget options available and the higher end gear.
There are quite a few options out there which would offer similar power and features, so going to a store which has PA gear on display is definitely advised, have a listen to a few sets and decide for yourself which sounds better. I did this at a Guitar Center, I listened to some EV, JBL, Behringer, Mackie, etc… and picked what I thought was the best fit for my needs and budget.
Give us a bit more info on what your use scenarios will be, your budget, etc… and we can likely give you more specific input. If you’ve already picked up some PA, let us know what it is and how it’s working out for you so far. Best of luck!
MoonshadowAugust 3, 2017 at 8:05 pm #2599481
I’ve just bought my first PA system and will share my findings with you.
I chose 2 powered speakers Alto Professional TrueSonic TS212 and one active subwoofer Alto TS212S. They’re incredibly great value. I had the opportunity to listen to them before buying.
You should consider them. They sound like the EV ZLX12 but are cheaper.
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