Why can't front panels be aluminium?

andyjevans · 14th September 2004, 04:14 PM

I'm sitting down to design a small box for an LS3.5A combination 2 way bookshelf. I can see how to quickly make a box glued together on all sides with only the front open. If the front was aluminium it would screw straight onto the thick sides+top+bottom (40mm). Such a removable front would make it easy to change speaker configurations. I haven't seen anybody do this - is there any reason why not? What are the considerations for a front panel - rigidity, lack of resonance..... Surely a 4mm or 5mm aluminium plate would have those qualities? Should mate well to the driver chassis too, and even look cool. Does this sound OK to you DIY people? Any examples of this? Andy

rchua77 · 14th September 2004, 04:18 PM

aluminium isnt a good absorber of sound. Bang a piece of wood and compare it with you bang a pot. Same theory applies, hope this helps.

rcavictim · 14th September 2004, 04:23 PM

I don't see why that wouldn't be fine. I'd go 1/4" thick aluminum though or 3/8" if the baffle is large. Any resonance issues could be dealt with by laminating a piece of MDF or something on the inside surface with a slightly elastic adhesive like Liquid Nails.

UrSv · 14th September 2004, 04:30 PM

Plenty of speakers around that do that. Check Dynaudio recent bigger models. Check Intertechnik who sell ready made panels for some drivers. Etc etc...

Don't see why not. How hard would it be to try and thorugh away if no good...

andyjevans · 14th September 2004, 05:33 PM

Check Intertechnik>>

I don't speak much German, and when I went through their site looking at the pictures I couldn't find anything - where is it on their site? I was going to make the panels and I wondered how exactly to cut out a large round hole - bigger than all my hole saws. I suppose a jig saw. Mine says up to 8mm aluminium. Any other ideas?

tktran · 14th September 2004, 05:42 PM

laminating something on the inside isn't going to deal with the high acoustically reflective surface on the outside? the first reflections would come off the baffle...

OTOH there are some speakers that use felt on their baffles.

to me these two opposites can be likened to the way speakers don't sound so good in a tiled kitchen compared to a carpetted lounge.

rcavictim · 14th September 2004, 05:54 PM

Quote:

Originally posted by tktran
laminating something on the inside isn't going to deal with the high acoustically reflective surface on the outside? the first reflections would come off the baffle...

OTOH there are some speakers that use felt on their baffles.

to me these two opposites can be likened to the way speakers don't sound so good in a tiled kitchen compared to a carpetted lounge.

I never suggested that it would. The laminate on the inside was to dampen vibrations in the panel (ringing). Plenty of baffles are made from hard acoustically reflective surfaces. Dealing with the edge shape and applying wool felt to the outer baffle surface are some ways to deal with the effects you mention.

andyjevans · 14th September 2004, 06:16 PM

Plenty of baffles are made from hard acoustically reflective surfaces>>

Some sides of the box would be made from solid mahogony, 32mm thick. Is this also "hard acoustically reflective" - i.e. a bad thing? I see cabinets made in all kinds of natural woods. On the other hand, I read in the BBC instructions for their speakers (LS3.5A e.g.) that they used birch because they found that hardwood sounded worse with the mid-bass unit. This discussion could include the question "what are the desirable properties of panels for building speaker boxes" - this includes aluminium, hardwoods etc etc. What about steel? Is this bad because it rings or because it's magnetic?

andyjevans · 14th September 2004, 06:23 PM

laminating something on the inside isn't going to deal with the high acoustically reflective surface on the outside>>

How about a sandwich? Two alu sheets with something like bitumen in between? I remember the designer of Totem speakers saying that dampening between two surfaces was much more effective than dampening on one surface alone.

qxlxp · 15th September 2004, 04:06 AM

andyjevans: tktran's posts make no sense to me. he seems to be intermixing principles of speaker building and small room acoustics and coming up with some "unique" theories of his own.

a 3/4" x 12" x 30" aluminum baffle looks like it would cost about $125- $150 usd each before machining. compare that to about $5 for mdf. there may be other issue regarding why aluminum is not the best baffle material, but i suspect there is not a lot of experience in the diy community because of its relatively high cost and the need to have it professionally machined (for most people). i have a pair of jbl lsr 25p's and their entire enclosure including baffle is aluminum. i think genelec is the same way. the infinity prelude mts has an extruded aluminum enclosure, but i am not sure what the baffle itself is made of. doesn't dynaudio's flagship speaker have an aluminum baffle?

14th September 2004, 04:14 PM	#1
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	Why can't front panels be aluminium? I'm sitting down to design a small box for an LS3.5A combination 2 way bookshelf. I can see how to quickly make a box glued together on all sides with only the front open. If the front was aluminium it would screw straight onto the thick sides+top+bottom (40mm). Such a removable front would make it easy to change speaker configurations. I haven't seen anybody do this - is there any reason why not? What are the considerations for a front panel - rigidity, lack of resonance..... Surely a 4mm or 5mm aluminium plate would have those qualities? Should mate well to the driver chassis too, and even look cool. Does this sound OK to you DIY people? Any examples of this? Andy

14th September 2004, 04:23 PM	#3
rcavictim diyAudio Member Join Date: Jun 2004 Location: Cool end of a soldering iron NW of Toronto	I don't see why that wouldn't be fine. I'd go 1/4" thick aluminum though or 3/8" if the baffle is large. Any resonance issues could be dealt with by laminating a piece of MDF or something on the inside surface with a slightly elastic adhesive like Liquid Nails. __________________ I.Q.Test. Have you ever purchased a recreational snowmobile?

14th September 2004, 04:30 PM	#4
UrSv diyAudio Member Join Date: Jan 2002 Location: Sweden	Plenty of speakers around that do that. Check Dynaudio recent bigger models. Check Intertechnik who sell ready made panels for some drivers. Etc etc... Don't see why not. How hard would it be to try and thorugh away if no good... __________________ UrSv Those who say it can't be done should not stop those who are doing it.

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14th September 2004, 04:18 PM	#2
rchua77 diyAudio Member Join Date: Jul 2003 Location: Back in Singapore	aluminium isnt a good absorber of sound. Bang a piece of wood and compare it with you bang a pot. Same theory applies, hope this helps.

14th September 2004, 05:33 PM	#5
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	Check Intertechnik>> I don't speak much German, and when I went through their site looking at the pictures I couldn't find anything - where is it on their site? I was going to make the panels and I wondered how exactly to cut out a large round hole - bigger than all my hole saws. I suppose a jig saw. Mine says up to 8mm aluminium. Any other ideas?

14th September 2004, 05:42 PM	#6
tktran Account Disabled Join Date: Mar 2003 Location: Perth	laminating something on the inside isn't going to deal with the high acoustically reflective surface on the outside? the first reflections would come off the baffle... OTOH there are some speakers that use felt on their baffles. to me these two opposites can be likened to the way speakers don't sound so good in a tiled kitchen compared to a carpetted lounge.

14th September 2004, 06:16 PM	#8
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	Plenty of baffles are made from hard acoustically reflective surfaces>> Some sides of the box would be made from solid mahogony, 32mm thick. Is this also "hard acoustically reflective" - i.e. a bad thing? I see cabinets made in all kinds of natural woods. On the other hand, I read in the BBC instructions for their speakers (LS3.5A e.g.) that they used birch because they found that hardwood sounded worse with the mid-bass unit. This discussion could include the question "what are the desirable properties of panels for building speaker boxes" - this includes aluminium, hardwoods etc etc. What about steel? Is this bad because it rings or because it's magnetic?

14th September 2004, 06:23 PM	#9
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	laminating something on the inside isn't going to deal with the high acoustically reflective surface on the outside>> How about a sandwich? Two alu sheets with something like bitumen in between? I remember the designer of Totem speakers saying that dampening between two surfaces was much more effective than dampening on one surface alone.

15th September 2004, 04:06 AM	#10
qxlxp diyAudio Member Join Date: Jun 2004 Location: Ohio	andyjevans: tktran's posts make no sense to me. he seems to be intermixing principles of speaker building and small room acoustics and coming up with some "unique" theories of his own. a 3/4" x 12" x 30" aluminum baffle looks like it would cost about $125- $150 usd each before machining. compare that to about $5 for mdf. there may be other issue regarding why aluminum is not the best baffle material, but i suspect there is not a lot of experience in the diy community because of its relatively high cost and the need to have it professionally machined (for most people). i have a pair of jbl lsr 25p's and their entire enclosure including baffle is aluminum. i think genelec is the same way. the infinity prelude mts has an extruded aluminum enclosure, but i am not sure what the baffle itself is made of. doesn't dynaudio's flagship speaker have an aluminum baffle?

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