Nope, in a sealed speaker the same amount of air is in the enclosure regardless if the speaker cone is moving in or out. What you are confusing is displacement. The measurable area, not air volume, inside the speaker changes but not the volume of air. Air easily compressed and decompresses, that does not decrease the volume of air.
Yes, speaker cone movement in a sealed enclosure neither creates or eliminates air. It simply compresses and decompress the air.
AKA Air Suspension speakers.
Not really Leon. The front of the speaker enclosure is open - or else you wouldn't hear the sound. Volume does change instantaneously as the cone moves. When you are pushing air out, you can't be sucking air in at the same time if the enclosure is sealed and the only opening is where the air is being pushed out. Compressing air if it can't escape to the outside world would not create sound in the outside world.
Naturally the front of the speaker cone is open, but the back is/was often ins an air tight environment.
I hate looking the info up but this kinda supports my comments.
Well... not so much. If I understand your earlier comments correctly, you are interpreting a sealed chamber to mean an completely sealed chamber. That's the point I commented on. It's not completely sealed as long as the front of the speaker is open. The balance of the speaker cabinet is neutralized to atmospheric pressure by that opening. It's only that sound is directed by that sealed back. Not that volume and/or pressure remain constant.
No the front of the speaker is open, obviously but the box in many cases is air tight. You probably came into the conversation late and are missing the key points.
Previous posts indicated the need for a vented port so that the speaker would operate. I said that this was not true. There seemed to be some thoughts that a speaker would not operate if it had a sealed compartment behind it, which is not true.
Agreed Leon - I did come into it late and maybe I misunderstood some points from the time I came in. I picked up on it where I thought I read that a sealed cabinet had a constant volume and that's where my initial comment entered. Sealed backs are one thing but there is no such thing as a speaker cabinet with a sealed compartment. At the very least, atmospheric pressure enters the chamber through the speaker cone.
On second thought - maybe I really do not understand enough about speaker design to make the statement that I made above...
BUT!!! ....we cannot possibly extend such an equally forgiving POV to ol' notbob. He's obviously wrong and not deserving of our forgiveness. Die, notbob! Die!
(c'mon, Mike, ya' know you wanna say it)
We having fun, yet? ;)
nb
Dude - you are one sick puppy.
Mike - I'm too old to be a "Dude" and I've never been a "puppy". I will admit my being "sick" is still in question, though. OTOH, if you wanna dog me in this newsgroup, I'm up for it.
Despite having givin up this nonsense, years ago, the diminishing size of usenet has made me long for more interaction. Wanna be my dance partner? ;)
nb
Leon wrote in news:RZadnZ9w85XqcWbLnZ2dnUU7- snipped-for-privacy@giganews.com:
Not to beat a dead horse, but you are the one confused. Go look up Boyle's Law on Wikipedia.
John
If there is no vent, of course the volume changes. The speaker cone moves, so the volume *has* to change. The air trapped inside the box is the spring for the cone. This is an "acoustic suspension" speaker (and they work quite well).
The same "amount" of air is in the box but the *volume* is not constant. The pressure is the inverse of the volume (for the given "amount" of air trapped in the box.
Mike Marlow wrote in news:ndhkeb$39k$ snipped-for-privacy@dont-email.me:
I do know that Soundtraxx Mini-oval speakers have an enclosure that the speaker fits tightly into, magnet side out. There is no hole for a vent in that enclosure, nor is one needed. At the same time, though, realize the dimensions of the speaker & enclosure are only about 8mm by 20mm. Sometimes rules change as things get smaller.
Puckdropper
Regardless, boules law has nothing to do with a speaker working correctly whether it is ported or whether it is an air suspension/acoustical style speaker. Your earlier comments indicated that speakers had to be ported to equalize air pressure on both sides of the speaker unless the enclosure was large and the speakers were small. That simply is not true.
Yep, and I built my own bass cabinets, as well as a few for others back when I was young, and sexy, enough to lug an Ampex SVT head around. ;)
Most of the speaker cabinets I built contained 15" woofers, moved a lot of air, and were baffled/ported" very precisely according to speaker cabinet gurus I knew when doing studio work, as well as some being direct copies of well known speaker cabinets ... much like I would reproduce a chair for someone these days.
There is ton of physics that goes into designing a pleasing sounding speaker ... with a bit of magic thrown. My studio was a (paid) test bed for many of the more well known studio speakers down through the years.
I can say yeah or nay for the sound, but certainly wouldn't presume to expound definitely on the physics, particularly when it comes to the highly dynamic volume/pressures of air, inside and out, therefore the precise "porting" requirements, in order to tune certain types of speakers to a very specific frequency for desired bass reproduction.
Yep ... the idea of sealed enclosure speakers, a very specific type of speaker design, is to allow the air behind the speaker to act pretty much like a spring, which helps control the movement of the speaker within its design limits.
It would have to be (relatively) "sealed" in order to do so.
Leon wrote in news: snipped-for-privacy@news.giganews.com:
What I actually said (regardless of what you think I "indicated") was that you won't get as much sound if the case isn't vented. Which is simply true and always will be (except, as krw pointed out, in the special case of air suspension speakers).
Actually, there is another special case - if the enclosure is thin enough to flex. In that case the enclosure itself will act like a slave speaker. This tends to sound really awful.
John
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