closing an open back combo amp

DannySnyder

Joined: Mar 02, 2006
Posts: 11079
Berkeley, CA
United States

Posted on Feb 18 2008 09:16 PM

Has anyone done this? Any issues to be concerned about? Does it improve the sound in any way?

—

Danny Snyder

"With great reverb comes great responsibility" - Uncle Leo

I am now playing trumpet with Prince Buster tribute band 'Balzac'

Playing keys and guitar with Combo Tezeta

Formerly a guitarist in The TomorrowMen and Meshugga Beach Party

Latest surf project - Now That's What I Call SURF

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Sonichris

Joined: Mar 06, 2006
Posts: 1912
Wear gloves - I'm in the Rockies
United States

Posted on Feb 18 2008 09:24 PM

I'd be worried about heat build up - if you could seal just the speaker cabinet portion, then it would probably work.

From what I've read - there was some actual math used when Fender designed the closed back cabinets. Air displacement and so on.

Still - I'd be interested to hear how it works.

—

"You can't tell where you're going if you don't know where you've been"

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JakeDobner

Joined: Feb 26, 2006
Posts: 12159
Seattle
5 News Pins

Posted on Feb 18 2008 09:31 PM

I wouldn't seal a combo for the same reason Chris suggested. There is a chance it won't be very bad but there is also a chance it could get really intense in there.

Also, it probably only improves the sound if you are into surf music. I prefer combo amps for non-surf but I am no fan of combo amps for surf. That is for my own specific tone. I can think of great examples with combo amps, but they are great for reasons other than tone.

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diceophonic

Joined: May 20, 2006
Posts: 2174
PacNW (Vancouver, Wa U.S.A.)
United States

Posted on Feb 18 2008 09:53 PM

Sonichris
I'd be worried about heat build up

I would not recomend it to a combo tube amp, but if it was a solid state rig then go for it. It would sound just like your current single 12 2x12 2x15 cab minus no chassis above

—

-Kyle

Beyond The Surf YouTube channel
Beyond The Surf Instagram
The Verbtones @ Instagram
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DannySnyder

Joined: Mar 02, 2006
Posts: 11079
Berkeley, CA
United States

Posted on Feb 18 2008 10:10 PM

what if you left the top open and only closed up behind the speakers?

—

Danny Snyder

"With great reverb comes great responsibility" - Uncle Leo

I am now playing trumpet with Prince Buster tribute band 'Balzac'

Playing keys and guitar with Combo Tezeta

Formerly a guitarist in The TomorrowMen and Meshugga Beach Party

Latest surf project - Now That's What I Call SURF

Top

diceophonic

Joined: May 20, 2006
Posts: 2174
PacNW (Vancouver, Wa U.S.A.)
United States

Posted on Feb 18 2008 10:26 PM

I don't think having the top exposed will help, everything being sealed up but only the top of the chassis exposed but then there wouldn't be any ventilation for the tubes, the top of chassis is not what needs air but the tubes, hmmm maybe a cooling fan inside the cab but then I would be paranoid every time I played out my amp with "I hope the fan is on and working" and that's if its a silent fan

—

-Kyle

Beyond The Surf YouTube channel
Beyond The Surf Instagram
The Verbtones @ Instagram
The Verbtones @ Facebook
The Verbtones @ bandcamp

Top

ozboomer

Joined: Sep 27, 2006
Posts: 81
Blackburn, Australia

Posted on Feb 18 2008 10:49 PM

DannySnyder
what if you left the top open and only closed up behind the speakers?

I might be talkin' through my hat here... but aren't you almost talking about a vented (ported) cabinet? Like you would need to install a tube in the back of the cabinet that needs to 'tune' the resonant frequency and such of the closed cabinet?

I've forgotten all my infinite baffle enclosure design studies(!)

—

I'm as free from money as a frog is from feathers

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Rio

Joined: May 22, 2006
Posts: 500
Hamilton, Ontario
Canada

Posted on Feb 18 2008 11:30 PM

I have an old Traynor Guitar Mate combo from the late '60s or early '70s, where there the speaker is fully enclosed, but an opening above that, where the chassis is located-- there must be other amps like that too?

—

http://www.facebook.com/?sk=lf#!/rockinrio.delrosa

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estreet

Joined: Mar 17, 2007
Posts: 839
United Kingdom
1 POTD Pin

Posted on Feb 19 2008 01:00 AM

ozboomer

DannySnyder
what if you left the top open and only closed up behind the speakers?

I might be talkin' through my hat here... but aren't you almost talking about a vented (ported) cabinet? Like you would need to install a tube in the back of the cabinet that needs to 'tune' the resonant frequency and such of the closed cabinet?

I've forgotten all my infinite baffle enclosure design studies(!)

A closed-back box would need to be deeper than a standard, say Fender combo, is. I have a Peavey 'convertible' extension speaker where the top half of the back panel is removable and that's quite a deep box. Although it's probably true that a cabinet would need to be ported for a full-range use, I suspect that it isn't essential for guitar purposes. From what I remember, I'm pretty sure the old 4x12s like Marshall etc - were not ported.

One difference that you get with a closed-back speaker is that the sound becomes more local and more directional; whereas with an open-back cab the reverse phase sound from the rear of the speakers is reflected from the wall behind you giving a much bigger 'spread' to the sound. Therefore, a small 1x12 closed-back cab, can be deafening to those in its aim, whilst being much quieter 'off-axis'. Not something you'd want but obviously not a problem you get with the huge Dual Showman cabs because they are moving more air in the first place.

—

http://www.myspace.com/thepashuns

Youth and enthusiasm are no match for age and treachery.

Last edited: Feb 19, 2008 04:39:33

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WR

Joined: Feb 27, 2006
Posts: 3832
netherlands
2 Link Pins

Posted on Feb 19 2008 02:36 AM

this is how the fedner studio bass did it...

—

Rules to live by #314:
"When in Italy, if the menu says something's grilled, don't assume it is."

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Rio

Joined: May 22, 2006
Posts: 500
Hamilton, Ontario
Canada

Posted on Feb 19 2008 06:40 AM

That's also more or less how the Traynor I mentioned was constructed as well, except the metal chassis (with switches, jacks etc) is visible (and accessible) at the very top. But basically, same idea with the speaker enclosed in a box.

—

http://www.facebook.com/?sk=lf#!/rockinrio.delrosa

http://www.facebook.com/?sk=lf#!/TheHighTides

http://www.facebook.com/?sk=lf#!/pages/The-Blue-Demons

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planish

Joined: Jan 09, 2008
Posts: 473
Sackville, New Brunswick
Canada

Posted on Feb 27 2008 11:36 PM

My understanding was that sealed cabinets were meant to use acoustic suspension speakers, with (I think) a softer/looser roll where the cone attaches to the basket.

—

I'm not a complete idiot. Some parts are missing.

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DannySnyder Joined: Mar 02, 2006 Posts: 11079 Berkeley, CA	Posted on Feb 18 2008 09:16 PM Has anyone done this? Any issues to be concerned about? Does it improve the sound in any way? — Danny Snyder "With great reverb comes great responsibility" - Uncle Leo I am now playing trumpet with Prince Buster tribute band 'Balzac' Playing keys and guitar with Combo Tezeta Formerly a guitarist in The TomorrowMen and Meshugga Beach Party Latest surf project - Now That's What I Call SURF Top
Sonichris Joined: Mar 06, 2006 Posts: 1912 Wear gloves - I'm in the Rockies	Posted on Feb 18 2008 09:24 PM I'd be worried about heat build up - if you could seal just the speaker cabinet portion, then it would probably work. From what I've read - there was some actual math used when Fender designed the closed back cabinets. Air displacement and so on. Still - I'd be interested to hear how it works. — "You can't tell where you're going if you don't know where you've been" Top
JakeDobner Joined: Feb 26, 2006 Posts: 12159 Seattle	Posted on Feb 18 2008 09:31 PM I wouldn't seal a combo for the same reason Chris suggested. There is a chance it won't be very bad but there is also a chance it could get really intense in there. Also, it probably only improves the sound if you are into surf music. I prefer combo amps for non-surf but I am no fan of combo amps for surf. That is for my own specific tone. I can think of great examples with combo amps, but they are great for reasons other than tone. Top
diceophonic Joined: May 20, 2006 Posts: 2174 PacNW (Vancouver, Wa U.S.A.)	Posted on Feb 18 2008 09:53 PM Sonichris I'd be worried about heat build up I would not recomend it to a combo tube amp, but if it was a solid state rig then go for it. It would sound just like your current single 12 2x12 2x15 cab minus no chassis above — -Kyle Beyond The Surf YouTube channel Beyond The Surf Instagram The Verbtones @ Instagram The Verbtones @ Facebook The Verbtones @ bandcamp Top
DannySnyder Joined: Mar 02, 2006 Posts: 11079 Berkeley, CA	Posted on Feb 18 2008 10:10 PM what if you left the top open and only closed up behind the speakers? — Danny Snyder "With great reverb comes great responsibility" - Uncle Leo I am now playing trumpet with Prince Buster tribute band 'Balzac' Playing keys and guitar with Combo Tezeta Formerly a guitarist in The TomorrowMen and Meshugga Beach Party Latest surf project - Now That's What I Call SURF Top
diceophonic Joined: May 20, 2006 Posts: 2174 PacNW (Vancouver, Wa U.S.A.)	Posted on Feb 18 2008 10:26 PM I don't think having the top exposed will help, everything being sealed up but only the top of the chassis exposed but then there wouldn't be any ventilation for the tubes, the top of chassis is not what needs air but the tubes, hmmm maybe a cooling fan inside the cab but then I would be paranoid every time I played out my amp with "I hope the fan is on and working" and that's if its a silent fan — -Kyle Beyond The Surf YouTube channel Beyond The Surf Instagram The Verbtones @ Instagram The Verbtones @ Facebook The Verbtones @ bandcamp Top
ozboomer Joined: Sep 27, 2006 Posts: 81 Blackburn, Australia	Posted on Feb 18 2008 10:49 PM DannySnyder what if you left the top open and only closed up behind the speakers? I might be talkin' through my hat here... but aren't you almost talking about a vented (ported) cabinet? Like you would need to install a tube in the back of the cabinet that needs to 'tune' the resonant frequency and such of the closed cabinet? I've forgotten all my infinite baffle enclosure design studies(!) — I'm as free from money as a frog is from feathers Top
Rio Joined: May 22, 2006 Posts: 500 Hamilton, Ontario	Posted on Feb 18 2008 11:30 PM I have an old Traynor Guitar Mate combo from the late '60s or early '70s, where there the speaker is fully enclosed, but an opening above that, where the chassis is located-- there must be other amps like that too? — http://www.facebook.com/?sk=lf#!/rockinrio.delrosa http://www.facebook.com/?sk=lf#!/TheHighTides http://www.facebook.com/?sk=lf#!/pages/The-Blue-Demons Top
estreet Joined: Mar 17, 2007 Posts: 839 United Kingdom	Posted on Feb 19 2008 01:00 AM ozboomer DannySnyder what if you left the top open and only closed up behind the speakers? I might be talkin' through my hat here... but aren't you almost talking about a vented (ported) cabinet? Like you would need to install a tube in the back of the cabinet that needs to 'tune' the resonant frequency and such of the closed cabinet? I've forgotten all my infinite baffle enclosure design studies(!) A closed-back box would need to be deeper than a standard, say Fender combo, is. I have a Peavey 'convertible' extension speaker where the top half of the back panel is removable and that's quite a deep box. Although it's probably true that a cabinet would need to be ported for a full-range use, I suspect that it isn't essential for guitar purposes. From what I remember, I'm pretty sure the old 4x12s like Marshall etc - were not ported. One difference that you get with a closed-back speaker is that the sound becomes more local and more directional; whereas with an open-back cab the reverse phase sound from the rear of the speakers is reflected from the wall behind you giving a much bigger 'spread' to the sound. Therefore, a small 1x12 closed-back cab, can be deafening to those in its aim, whilst being much quieter 'off-axis'. Not something you'd want but obviously not a problem you get with the huge Dual Showman cabs because they are moving more air in the first place. — http://www.myspace.com/thepashuns Youth and enthusiasm are no match for age and treachery. Last edited: Feb 19, 2008 04:39:33 Top
WR Joined: Feb 27, 2006 Posts: 3832 netherlands	Posted on Feb 19 2008 02:36 AM this is how the fedner studio bass did it... — Rules to live by #314: "When in Italy, if the menu says something's grilled, don't assume it is." https://www.facebook.com/The-Malbehavers-286429584796173/ Top
Rio Joined: May 22, 2006 Posts: 500 Hamilton, Ontario	Posted on Feb 19 2008 06:40 AM That's also more or less how the Traynor I mentioned was constructed as well, except the metal chassis (with switches, jacks etc) is visible (and accessible) at the very top. But basically, same idea with the speaker enclosed in a box. — http://www.facebook.com/?sk=lf#!/rockinrio.delrosa http://www.facebook.com/?sk=lf#!/TheHighTides http://www.facebook.com/?sk=lf#!/pages/The-Blue-Demons Top
planish Joined: Jan 09, 2008 Posts: 473 Sackville, New Brunswick	Posted on Feb 27 2008 11:36 PM My understanding was that sealed cabinets were meant to use acoustic suspension speakers, with (I think) a softer/looser roll where the cone attaches to the basket. — I'm not a complete idiot. Some parts are missing. Top

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closing an open back combo amp