Acoustic gig: subwoofer yes or no?

[Scatcat]

I have the first gig with my new trio: acoustic guitar, electric guitar and female voice. I have two Montarbo speakers MN250A 250w rms 8’ cone and a sub behringer 500w. I play outside in a pub and I have to cover 13x6 meters. My idea is to use only the two speakers because I think without a drum or a bass that I don’t need a subwoofer. What do you think?
Thanks and sorry for my English.

[Tico]

Keep in mind the frequency of the lowest pitch on the standard guitar (the E on the unfretted 6th string) that's tuned to standard pitch is about 82 Hz.

Find out the frequency response of your PA, especially how far down (in dB) its flatness is on the low end and at what frequency.
Better yet see if you can find graphs of freq response.

If it's only 3 dB down at 80 Hz, I'd say you don't need a sub.
Keep in mind that ruler-flatness is very rare in PAs, especially affordable ones.
Also reputable accurate specs are more likely with only the most expensive equipment - then few even understand how to read and understand specs.
Even if you desired a PA with a flat response every user reaches for the bass and treble knobs anyway for rooms that are not perfect, and to suit personal taste.

Then consider the hassle, expense and weight of lugging around a heavy sub.
Especially since few will notice 3 dB difference in flatness up at 82 Hz.
IMO if you were trying to push 30 or 40 Hz out there then a sub might make more sense.

[Silly Moustache]

I simply don't see a need for a sub-woofer in any acoustic music.

[MikeBmusic]

Record an acoustic guitar with a decent microphone, then take a look at the spectrum analysis. Yes, there are harmonics lower than 80Hz! But in a live situation, no one is going to hear or notice them anyway, skip the sub unless the main speakers/sub system has a cutover frequency up in the 120Hz range, in which case the mains may be lacking for that lower frequency range.

[RockerDuck]

You don't need a sub for your voice or acoustic guitar. I tried playing with a sub before and it was useless, unless you are playing bass. You can buy a
"boss OC-3" pedal and enhance the bass of you guitar cheaper.

[ljguitar]

Hi SC

Overambitious use of sub-woofers is one of the reasons I use a sound-hole-plug (feedback suppressor) when playing at higher volumes in bands.

When there is a bass player, or a keyboardist then a sub may come into play. Even bass drum doesn't need a sub if you are going for a tight sound.

[Scatcat]

Thank you everybody for the answer.

[Kalani]

No subwoofer. You’ll just be inviting feedback problems from your acoustic guitar.

[pieterh]

I agree with the above posts, subwoofer (usually carrying frequencies under 100 hz) is unnecessary. For almost all acoustic gigs those frequencies would just get in the way, you would find microphone pop noise would be made worse, and very very few voices have those frequencies - unless you have a voice like Barry White. Even then I would as a sound engineer be cutting the low frequencies in order to make the mix cleaner.

A common trick of sound engineers is to actually roll off the low bass eq on bass guitar so it doesn’t compete with a kick drum. A couple of weeks ago I did the same on an electric bass as together with the acoustic guitar it was actually making the overall mix muddy. By reducing the low end on the bass the whole mix became much better balanced and more musical.

As others have said, in most situations a sub is going to be useful for chest hitting kick drum, 5 string bass low sounds and keyboards. Nearly all other instruments have no frequencies that would end up in the sub - I would argue that an acoustic guitar may possibly produce lower harmonics than its fundamental of around 82 Hz (by resonance maybe, not entirely convinced) but that doesn’t mean they are desirable.