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Topic: Closed Back vs Open Back??? |
Sonny Jenkins
From:
Texas Masonic Retirement Center,,,Arlington Tx
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Posted 16 Apr 2017 8:06 am |
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| How does open or closed back speaker cabinet effect tone,,especially bass? or is there ANY effect? Maybe Brad or Ken or other experts could weigh in with an opinion. |
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Georg Sørtun
From:
Mandal, Agder, Norway
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Posted 16 Apr 2017 12:45 pm
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Depends entirely on actual - or "engineered" - cabinet size/volume.
- Open back cabinets have an increasing loss in efficiency towards lower frequencies, from the frequencies where waves coming from front and back of the speaker(s) start to cancel each other out as the travel around the outer sides of the cabinet.
Results for most open back cabinets used for steel, are an acoustic roll-off and loss of bass from around 150Hz down. Efficiency may be as low as 1-2% around 50Hz, while it may be about 25% above 200Hz.
As for "tone": open back cabinets "rumble" at lower frequencies.
- Totally closed cabinets of same size as the average open back cabinet, run into a "compression" problem for lower frequencies, as the speaker have to compress and expand the air inside the cabinet in order to move the membrane.
Totally closed cabinets have to be large in order to minimize this compression.
As for "tone": closed back cabinets "kick" at lower frequencies.
In reality few "closed back cabinets" are totally closed up, for the reason described above. Some form for ports to create suitable resonances and let the speaker "breathe" (reduce/eliminate compression), are "engineered" into the various cabinet designs. Good "ported" designs can show an efficiency of about 25% from 40-50Hz all the way up, and the very best "ported" designs can reach an efficiency in the low frequency range of up to 50%. |
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Ken Metcalf
From:
San Antonio Texas USA
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Posted 17 Apr 2017 3:52 am
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If you play at lower / reasonable volume levels I don't think it makes much difference.
As volume increases you will get more bottom end from a closed back.
A open back disperses sound around and behind more on stage. |
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Bill A. Moore
From:
Silver City, New Mexico, USA
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Posted 17 Apr 2017 6:53 am
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I have built several cabs now with an oval ported closed back. I've been making the port the same width as the speaker, and about a quarter of the width high.
I think it is the best of both worlds! |
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Ian Rae
From:
Redditch, England
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Posted 17 Apr 2017 8:22 am
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| Ken Metcalf wrote: |
| As volume increases you will get more bottom end from a closed back. |
Agreed, as long as you have plenty of amplifier power, as the closed cab is inherently less efficient. When I played bass I used a closed 2 x 12. I wish I still had it as it might well have been good for steel too.
_________________
Make sleeping dogs tell the truth!
Homebuilt keyless U12 7x5, Excel keyless U12 8x8, Williams keyless U12 7x8, Telonics rack and 15" cabs |
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Bruce Derr
From:
Lee, New Hampshire, USA
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Posted 17 Apr 2017 1:33 pm
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| Georg, thanks for that very clear overview! |
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Paddy Long
From:
Christchurch, New Zealand
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Posted 17 Apr 2017 7:33 pm
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Great description by George - in my rack setup I use one of each - both driving Telonics 15" speakers - 1 x Open backed and 1 x closed back, both cabinets are the same size. The result is very pleasing and very punchy in the bottom end.
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14'Zumsteel Hybrid D10 9+9
08'Zumsteel Hybrid D10 9+9
94' Franklin Stereo D10 9+8
Telonics, Peterson, Steelers Choice, Benado, Lexicon, Red Dirt Cases. |
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Bill L. Wilson
From:
Oklahoma, USA
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Posted 17 Apr 2017 8:50 pm Finding the Happy Medium.
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At this time, I have a 2-12 w/JBL D-120F 's and two single 15" JBL D-130F's that I use w/a Fender Twin Reverb head. The 2-12 cab. is not as boomy as the 15's even though both are open back. When I first built these they were closed back and quite boomy, but opened up made a big difference. The 15's will be powered up on three outside gigs this weekend, with guitar and steel blasting thru'em.
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