General tech questions

Closed Back vs. Open Back Question…

1

In layman's terms, what are the tonal differences of an open vs. a closed back amp? I'll phrase the question a different way. You have two identical amplifiers one has an open back one has a sealed cabinet. Using the same guitar with identical knob settings on the amp is there a noticeable difference in tone between the two, and what would those differences be?

2

Not a clue Bear. Maybe the open back would be lighter to carry? :)

3

i like closed back cabs seem to keep more of a solid bass sounds/tones

4

It seems to me that the closed back amps project better.

5

Lower and more powerful bass from the closed back cab.

It has to do with the fact that there are sound waves coming off of both sides of the speaker cone. The lower frequencies have an easier time wrapping around the open back and canceling out. They can't do that at all with the closed cab.

The closed cab may cause the speaker to be a little less efficient because of the pressure build up - hence bass reflex ports.

In my opinion, open back cabs would be ok in a band because you dont want to muddy the mix. If I'm playing alone, I feel like my guitar sounds thin through an open back. I can always turn the bass down on a closed cab.

6

Open back should be a little more, how to say - ambient? Because the sound is released equally in two planes, you'll get more natural reverb. People say it "fills up the room." Closed back, as well as giving a little more bass, will tend to project a little more in the direction your amp is aimed. Seems like a lot of stuff nowadays comes with a convertible panel on the back to allow for personal preference.

7

Love the way you broke that question down.. I noticed if it had casters, they'd need brakes if it was closed back

8

It really depends on how the cabinet was designed. There are resonance frequencies and other ways to tune a closed cabinet. The only real "convertible" cab I know of is one made by Dr. Z.

9

To me,closed-backs sound a little more scooped and a lot more directional.Open-backs project out the back(duh!) and there's more sound bouncing around the room.That seems to emphasize the midrange and slightly attenuate the low end.

10

Indoors I like open combo amps, so the drummer can hear.

Outdoors I like tiny combo amps, mic'd up and folded back through the monitors.

Back in the days before PA's were decent I used combinations (outdoors) of closed back 4X12's and combo amps (to let the drummer hear what was going on).

In my experience, open combos don't have the bottom closed back cabinets have, all else being equal (not that you can't EQ 'em some).

11

Closed back has more punch not just more bass but its punchy

12

Opening up my Pignose is the tone control :)

13

Playing an Allen Encore head through a closed back, 4x12 Marshall cab at the rehearsal space. Great punch and low end, that is true, but it is so directional, can be difficult to work with.

I prefer open back cabs. Or the closed back Forte 1x12 cab with side ports. MD

14

Thanks, this has been very helpful.

As many of you know, I recently converted my Kustom KB100 bass amp to a guitar amp by replacing the original 15" woofer with an Eminence Commonwealth (JBL D130F clone) and I really like the sound of it.

It is a closed back amp and my question was geared as to whether or not I should open up the back. Your answers have helped me to make the decision to leave it as a sealed unit. I appreciate your knowledge and advice.

15

Closed back = less moaning from the drummer.

16

Closed back = less moaning from the drummer.

– tonyb

Closed back = less moaning from the drummer.

– tonyb

:D :D :D :D :D

17

Hey Bear, some of it depends on the design specs of the speaker driver itself. Some are designed to be installed in a closed enclosure because they need that 'stiffness' to help the cone from turning into flabby paper. Others are specifically designed to be in open cabs with the magnet and surround/suspension made to keep the cone under control.

18

Hey Bear, some of it depends on the design specs of the speaker driver itself. Some are designed to be installed in a closed enclosure because they need that 'stiffness' to help the cone from turning into flabby paper. Others are specifically designed to be in open cabs with the magnet and surround/suspension made to keep the cone under control.

– Hermitt

Hey Bear, some of it depends on the design specs of the speaker driver itself. Some are designed to be installed in a closed enclosure because they need that 'stiffness' to help the cone from turning into flabby paper. Others are specifically designed to be in open cabs with the magnet and surround/suspension made to keep the cone under control.

– Hermitt

The Eminence Commonwealth is designed to work in either just like the JBL D130F it was reversed engineered from, so no issues or problems there, but a good point, thanks.

19

When I can I like to use one of each — an open-backed combo plus a sealed back 2x12 extension cab.

21

Open backs are good for combo amps, as they allow air to circulate better and help with cooling. On a separate speaker cabinet, it's more about tone. Most speaker cabinets designed for use with keyboards or bass are closed back (so are stereo speaker cabinets), because they have improved projection across the tonal spectrum --- fatter lows, punchier mids, and crisper highs. If the cabinet is only being used for guitar, the open back works, because the lower and higher frequency loss doesn't impact the tone of the guitar as much, since it's more of a mid-range instrument. I once had an opportunity to play through the same cabinet with and without a back. Without the back, the guitar (Gibson ES-175) sounded warmer in the mid-range and less defined on the low E and A strings. High notes projected well. With the back, the highs were crisper, the mid-range was more defined, and the lows were PHAT!

If I were going to do solo guitar a la Joe Pass, the closed back would have sounded better to my ears, but in a band context, the open back worked better for guitar.


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