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FDP Forum / Performer's Corner / subwoofers



"The radio makes hideous sounds"-Bob Dyl
Jul 21st, 2017 04:27 PM   Edit   Profile  

In a 6 pce band playing small clubs. Is it of benefit to plug a subwoofer into our mixer sub output? Also can any sub work with a mixer (ie a home theatre sub even)?
If not, what spec's need to be checked to make it compatible. Sorry for all the supplementary questions.

Doug McQuaid
Contributing Member

Austin, Texas

Jul 22nd, 2017 06:22 PM   Edit   Profile  

Not enough info to make any recommendation one way or the other.

What genre of music does the band play?
What instruments?
What are you currently using for PA?
Do you need to run instruments through the PA?
How big are the clubs?

In just about every case I can think of, a home theater subwoofer would not be adequate for live performance reinforcement.

Tony Wright
Contributing Member

Stillwater, OK

I never met a calorie I didn't like.
Jul 23rd, 2017 06:38 AM   Edit   Profile  

Let's approach this in the way you presented it:

"In a 6 pce band playing small clubs."
What is the fire code occupancy rating for number of people in the small club...small means different things to different people. I would call a fire code of 150 people "small" but to someone from a larger city, 500 people might be small....

Regardless a "6 piece band" is rather large. Thus the stage volume is probably rather large. So my question back to you is two fold...what do you put in the PA now? IF everything goes in the PA and there are NO stage amps then I think the minimum I would suggest would be "dual 15 with horn" main speakers and the next logical step would be to simply add a pair of subwoofers that are single or dual 18 inch woofers rated at no less than the same power as your dual 15/horn mains. ON THE OTHER HAND, if all you plug in is the vocals and keyboard, you are probably adequate with a simple pair of "single 15 with horn" cabinets.

OR IN OTHER WORDS...if you are not putting instruments which require support for LOW FREQUENCIES, then you do not need subwoofers.

In my part of the world, 6 piece bands typically are more likely to want to control ALL the sources to lift the softer instruments to the levels of the louder instruments AND to reach those "small clubs" back corners with volume.

Next topic:
"Is it of benefit to plug a subwoofer into our mixer sub output?"

I do not know if that is the best way to send signal to your subwoofer because I do not know if there is a crossover or a low pass or high pass filter involved so that the lows-mids-and-high-frequencies ALL go to the mains and the "lows only" pass out of the mixer via sub out to the subwoofer...nor do I know whether you use powered speakers with a built in frequency filter (high pass or low pass) or if you use passive speakers, if the power amp you use has high/low pass filters.

TYPICALLY...I would suggest that you acquire a subwoofer that is rated for live music...not a home stereo/TV home theater subwoofer unless it was basically a powered subwoofer with a single 18 and around 700-1000 Watts OUTPUT

Too many people think the label near the AC power input on an electrical device tells you the power rating of the item. The problem is that is typically the POWER CONSUMPTION and NOT the device's OUTPUT.

Your last question:
"If not, what spec's need to be checked to make it compatible."

Well, can I assume this subwoofer has its own internal power amplifier or not? Does it get a full range of frequencies (probably from around 40Hz or 50Hz to 20kHz)...OR does it receive only the lower end frequencies (or perhaps has an internal crossover or filter?) in the lower range only (around that same 40-50 Hz to around 100-150 Hz)???

I would also question whether your mixer's "SUB OUTPUT" is a "sub-group" or whether it is intended for the signal to be sent to a subwoofer which may or may not be sent out of the mixer powered or Unpowered and additionally may be sent out of the mixer "lows only" or "full range".

And finally, does the home entertainment subwoofer have the ability internally to only amplify the low frequencies...meaning it can split the highs out of the speaker output.


Now here is the gotcha...

Low frequencies typically require MORE POWER than your mains.

Remember those old sci-fi movies with the evil mad scientist and the oscilloscope always lurking in the background showing sound waves (or sine waves). Well...

Sound really travels like that...in waves. Kind of...more or less....what happens is lower frequencies are less waves per given measurement but they are BIGGER waves due to the low frequency...get it? Frequency and how many waves? The problem is:

To get those low frequencies to be heard at rock band volume, you need a lot of power to reproduce those large "heavy" waves. Typically it takes "twice as much power as the mids and the highs".

So, if you are running speakers with 500 Watts output rating as main speakers, you will be looking for at least 1000 Watt speakers output rating for your subwoofers. Be sure you compare apples to apples. If the mains are listed at Program Rating, then you need to compare the Program Rating of the Home Theater subwoofer. You can compare any of the popular ratings...RMS or Program or Peak, but the ratio needs to be kept in order to get the level from the mains and subwoofer (sound pressure levels or "SPL" or Decibles shown as dB). To be more clear, if the main speakers produce 100dB then your target for the subwoofer is also 100dB. However, you will find that it typically takes "twice as many Watts to accomplish that goal".

Unasked: Can I get by? Maybe. Probably...for a short time at least. Short as in "a short period of time before the electrical short or other damage happens and the speaker fails if you push it too hard to get the volume you need/expect." In other words...Blown Speaker.

KEEP IN MIND...I am NOT a trained engineer and I am telling you things that I have mis-mashed together over the years.

Can it work? Well, if you were a "mostly instrumental with a few vocals folk music ensemble" or local "roots style" music ensemble and played mostly acoustic/electric instruments to an audience of 40-60 in a room about 6 Meters by 10-15 meters AND if you did not raise the volume level much louder than the volume it would take to "shout to the people in the back without any PA"...then I think you can get by with it for awhile...depending on the cost of the home entertainment subwoofer and the ease of repair or replacement.

I have seen bands take regular bass guitar amps and use them as subwoofers...I have also seen people take two matching bass guitar speaker cabinets and connect to a power amp (in that case it was a QSC GX-5 with built in crossover/filter) and that was their normal subwoofer rig. It worked.

Now "IF" this home entertainment subwoofer is rated at 2000 Watts and it has its own internal power amplifier, try to find the specifications and look for one that gives you "Maximum SPL). That is shown in Decibles. I would not want a subwoofer that could not provide 100-110 dB for the SPL rating. The more SPL, the LOUDER the subwoofer, regardless of the frequency range.

I am not overly excited that my subwoofer does not reach 30 Hz as long as it can hit around 120-130dB at 85-to-100 Hz. Granted, if the subwoofer can hit stronger at 40 Hz and even 50 Hz, I would probably consider it, if the price were right. MY band does not require that much low end. Low E on the bass guitar is 41 Hz. Kick drum hits the "feel it in your chest" around 85 Hz on the typical young adult male.

I simply do not know enough to tell you that "it should be OK" but I can tell you the likelihood of a rock band in a room of 200 people will get much benefit from a single 12 inch 300 Watt home entertainment subwoofer is about the chance of 2 ice cubes placed in a microwave set for 2 minutes on high. I would not expect significant audience satisfaction from the booming lows at the end of the night...but it can happen, if the home entertainment subwoofer is actually a single 15 or 18 woofer with a 1000 Watt power amp that produces 130 decibels and also has a frequency range of 40Hz to 200Hz. (A lower frequency range would be an improvement of significant proportions...say 35Hz to 120Hz.)


One thing that can help:

Corner loading the subwoofer.

Find a corner in the stage where the walls meet at 90 degrees. (It could also be just off the stage in the corner nearest the stage...what you are looking for is a wall that runs from the "front" to the "back" of the room with few obstructions such as "the bar" or other walls...tables and people's legs do NOT count)

Set the subwoofer at a 45 degree angle pointing the center of the woofer towards the intersection of the two walls. Leave "about" 30cm or 12 inches between the front corners of the subwoofer and the intersecting wall.

You will be using the room's walls to serve as a "horn loaded subwoofer". It can help indoors. Keep in mind that you might get low frequency feedback IF the kick drum mic is placed where it gets a lot of signal from that "short wall" in front of the subwoofer is the wall behind the drummer. If the stage IS in the corner, simply place the subwoofer behind the drummer in the same "stand off" from the corner. You should not run as much risk of low frequency feedback.


I know of some outstanding "automotive" Kicker "L-7" subwoofer made for car stereo systems. The world headquarters of Kicker is here in my town. Their sound system at work consists of four of the L-7 in four boxes powered by two QSC PLX-3602. That is ONE L-7 on each channel of two stereo amps. The PLX3602 produces 775 Watts at 8 Ohms. They handle bass guitar and kick drum quite well. Sorry, that band did not have any other low frequency producing instruments (keys, horns, etc).

So...it can work if the subwoofer can handle it...but if the subwoofer is too small (I would not waste the time on anything under 12 inches unless you are an acoustic group) or the amp section is too small (probably nothing below 500-750 Watts powered, 120dB SPL output) and especially if you can corner load the room...it "could" work for your needs.

Maybe. Perhaps. Above advice does not reflect the opinions of the FDP and Chris Greene...

Kicker L-7 12 inch SQUARE subwoofer speaker.

Mick Reid
Contributing Member


American-made in Oz!!
Jul 23rd, 2017 05:37 PM   Edit   Profile  

I was going to say *everything* Tony said but he beat me to it!!
NOT REALLY, Tony's the man when it comes to PA stuff!

All I will add is if you were originally thinking "home theatre", I'm guessing there may be budget concerns.
The lowest priced 15" sub I've seen is a Behringer 15"/500w powered unit for $695AU. (bare minimum size & wattage you'd want).
I for one don't knock the Behringer stuff, but I have no personal experience their subwoofers.

I'm also going to presume the "sub out" you mentioned is indeed the "sub group" as Tony mentioned.

You can think of using the sub group as a means of routing individual signals to a separate poweramp or powered speaker (say a mic'ed kick drum & DI bass to the subwoofer).
A powered subwoofer *should* have a "high cut" feature that will only let the selected low freq's pass. IMO this is the easiest method as you don't require a external poweramp, crossover or equaliser as with a passive subwoofer.

Other considerations before adding a sub(s) are:
Transportation - they're heavy and bulky.

Venues - I forget where in AUS you live, but a lot of small clubs (clubs in general) have become very sound level conscious (council regs etc). Pumping out low freq's can be problematic in some areas.

Just 2 more cents for you...



The radio makes hideous sounds-Dylan
Jul 23rd, 2017 08:44 PM   Edit   Profile  

Thanks guys,
Food for thought here.
Tony thanks for going "above and beyond" in that explanation. More questions to consider before I can make an informed decision though.
Anyway; thanks indeed.



Thank God for guitars!
Jul 31st, 2017 05:27 PM   Edit   Profile  

One other caution. If you haven't crossed over the sub with your mains, and both are trying to push the low end, the subwoofer can work against the mains and actually deplete the low end overall. It's all about the placement and phase relationship of the outputs.

FDP Forum / Performer's Corner / subwoofers

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