Closed back vs open back unmiced gigs

billando · July 2022

For those who gig unmiced do you prefer to use closed back cabs?

I used to use a marshall 1960a with g12t75s from the 1980s. Through this was a jcm 800 2204 with gain full, master barely above 2 and treble booster on about quarter way just to add something. Lately i have been using 1x12 or 2x12 open back combos for easiness to carry. Hearing some clips back the combos seem to be a bit mushy and lost in the mix with similar settings (never used the treble booster though). Bit surprised since these are two good vintage marshall combos, jcm 800 4010 and jmp 2104. Both have g1265 speakers.

Is the 4x12 just providing more punch than the open back combos for unmiced gigs? Would the g1265 speakers be contributing to a weaker sound? Maybe the treble booster not being used is contributing...by the way i play in a 5 piece with a loud drummer, bassist and second guitarist.

Cirrus · July 2022

Here's what happens:

An open backed combo pushes as much sound out the back as out the front. The sound out the back is out of phase with the front sound, but takes some time to get round to the front of the cab. Practically speaking, the resulting blend of front and rear sound will cancel out bass and give a more vocal midrange vowel voice, as the time for the rear sound to make it round the front means that the cancellation will be frequency dependent - some midrange frequencies might even end up boosting rather than cancelling out.

When you're close to the front of the cab, the sound coming out the front is proportionally louder than the sound coming out the rear.

As you get further out front, the front and rear sound you can hear gradually approaches a 50:50 split.

The result: To a mic right on the speaker or a player standing near the amp, there will be bass. But as you get further from the cab, you find this bass does not project into the room and the cab's tone gradually gets more shouty/ midrangy.

A closed back cab is more consistent with distance, but the closed back usually resonates with the bass so there is still some low end drop off with distance. It's just not as severe.

ElectricXII · July 2022

I gig with an AC15 and most of the time it's mic'd, but it does seem more "directional" than my open-backed Deluxe Reverb. If I stand too close in front of it the other guitarist sometimes struggles to hear me unless it's in his monitor. The DR spreads the sound out more, but for our material the Vox tone works better. I can't say the closed back sounds mushier than the open back in clips I've listened to, but they're mostly smartphone videos.

billando · July 2022

Ok so would the 4 speakers and closed back give a bit more clarity and punch at the same settings compared to the 1x12 open back combo given that my old jcm 800 2204 and jcm 800 4010 combo are basically the same amp?

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Closed back vs open back unmiced gigs

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