The Case for Mounting Speakers Diaphragm-out

[peteski]

Like I said, our tiny speakers and enclosures (and limited audio amplifier power) severely limit what can be accomplished to maximize the low frequency (and even overall) sound quality.

[lashedup]

I did an impromptu test with an 11x15 speaker that I temporarily "mounted" (used modeling clay as the sealer base) with the speaker out/up and then with the speaker in/down and the speaker firing down into the enclosure was noticeably better. Part of what I wonder with these "cell phone" speakers is how the designers are envisioning their usage. These are often rectangular in shape and many have a foil-type material for the speaker which you'll sometimes see in tweeter designs. It makes me wonder if part of the assumption is that there isn't much room for any enclosure in a cell phone due to lack of depth and maybe the downward firing that is affixed to the case or PC board in the phone is using the surface mount as an amplification for sound. If you hold the speaker in the air with nothing around it and play sounds through it they are tinny and sound lousy. But if you take the speaker and hold it down to a table facing down the sound is far, far better.

- jamie

[peteski]

If you hold the speaker in the air with nothing around it and play sounds through it they are tinny and sound lousy. But if you take the speaker and hold it down to a table facing down the sound is far, far better.

- jamie

Jamie,  what you said applies to all the sound transducers (speakers). all shapes and sizes..  If there is no separation of the front and back of the speaker cone then the sound waves produced by the front facing side of the speaker cone are 180 degrees out of phase with the sound waves generated by the rear facing side of the speaker cone. Since there is nothing blocking those sound waves from combining, they cancel each other out, causing the speaker to sound shitty.    The process is a bit more complex that that (depending on the size of the speaker and the frequency of the sound waves, but the bottom line is that if you don't separate the air between the front and back of the speaker (by placing the speaker in enclosure), it will sound really bad.  As far as which side of the cone faces the enclosure, it is not all that important.

I think most of us, as young adults, either by ourselves or had a friend with a car and couple of 6 x 9 oval speakers, hooked up to a 40W booster-equalizer, sitting loosely on top of their car's package shelf. The bass sounded like crap!  Well, until we smartened up and actually mounted them in the package shelf where the back of the speaker was facing the trunk (suddenly the speaker was in an enclosure). That dramatically improved the sound quality.

[lashedup]

Ah, the old 6x9 mounted to a piece of plywood...   Those were the good ol days.

[peteski]

Ah, the old 6x9 mounted to a piece of plywood...   Those were the good ol days.

Actually, that small piece of plywood the speaker was mounted to provided a tiny baffle which provided a small improvement of sound quality.  What I was talking about is just the bare speakers themselves plopped down on the package shelf, siting on their magnets (which held them down to the metal shelf) with the speaker cone sitting up in the free air.  You couldn't do any worse than that. I had few friends with that type of "installation".  And yes, those were the days . . .

I posted this link earlier, but again, if someone is even a bit curious how all of this works, read through https://en.wikipedia.org/wiki/Loudspeaker_enclosure

[jdcolombo]

I did an impromptu test with an 11x15 speaker that I temporarily "mounted" (used modeling clay as the sealer base) with the speaker out/up and then with the speaker in/down and the speaker firing down into the enclosure was noticeably better. Part of what I wonder with these "cell phone" speakers is how the designers are envisioning their usage. These are often rectangular in shape and many have a foil-type material for the speaker which you'll sometimes see in tweeter designs. It makes me wonder if part of the assumption is that there isn't much room for any enclosure in a cell phone due to lack of depth and maybe the downward firing that is affixed to the case or PC board in the phone is using the surface mount as an amplification for sound. If you hold the speaker in the air with nothing around it and play sounds through it they are tinny and sound lousy. But if you take the speaker and hold it down to a table facing down the sound is far, far better.

- jamie

Actually, cell phones use enclosures.  They are not boxes, however.  They are injection molded to fit around the electronics at the bottom of the case, and in the case of the iPhone, at least, are mounted at the bottom of the phone with the speaker at one end, and sound exiting from the other.  If you do an internet search for "iPhone 4 speaker" you'll see a number of images for the enclosure (I didn't want to repost them here, because they may be copyrighted).  Ditto for the Galaxy Note II.

It's hard to tell which way the speaker is "facing" in these enclosures; the photos I have seen for the Galaxy Note II seem to indicate that the speaker faces up, but is sealed off by the back, so that the sound comes from the rear of the speaker, which is routed through the plastic enclosure out the bottom of the phone.  But whether facing out or facing in, cell phone speakers (and tablet speakers) use enclosures . . .

John C