I don’t see much topic on this what’s the idea of having drivers butted up against a sidewall? Say the frame is truncated so the sidewall would be right of on the frame of the speaker. What does this do for sound?
Same with an internal divider for woofer/midrange if it’s right in between the truncated frames so the drivers are still close but there’s a wall dividing them. A lot of speakers I’ve bought have the drivers mounted very close to a sidewall or brace so I’m guessing it’s fine to do?
Same with an internal divider for woofer/midrange if it’s right in between the truncated frames so the drivers are still close but there’s a wall dividing them. A lot of speakers I’ve bought have the drivers mounted very close to a sidewall or brace so I’m guessing it’s fine to do?
I do not think putting a driver close to the side walls of the box will cause much harm if there is plenty of space around the driver elsewhere, worst nightmare would be putting the driver at the end of a small diameter pipe
It's fine for the most part. Just don't put any damping material too close to the driver.
You don't want the damping to sympathetically vibrate with the cone.
You don't want the damping to sympathetically vibrate with the cone.
Now i deal mostly with fullranges which are likely more sensitive to nearwall palcement than a bass driver but i have found that too close is not good introducing midrange/voice colouration (cupped sound) from early reflections back thru the cone.
And i almost always make sure surfaces near te driver are lined with natural felt (usually 12mm cotton) to help minimize reflections as much as possible.
dave
And i almost always make sure surfaces near te driver are lined with natural felt (usually 12mm cotton) to help minimize reflections as much as possible.
dave
I used to think that and I remember discussing it with Earl Geddes and he explained to me how it doesn't actually happen, sound doesn't pass through the cone and any modulation is physically and electrically damped.
From Fs up to the first break up mode, I believe this is true. The voice coil is controlling the motion of the cone, and the force that the acoustical energy inside the box exerts on the cone is very small compared to the force that the motor generates.
Above the first mode cone resonance, the voice coil is not in complete control of the cone motion, so there is some possibility of internal cabinet energy to affect the cone's complex motion above break up.
Now of course there will always be ordinary sound transmission through the cone, just as there is sound transmission through the cabinet walls, but I do not know how much of an affect this is.
With a full range driver, there is a whole lot of important upper range frequency that is above the break up mode, and usually the first break up mode is well controlled. So Dave might have to do things differently than I would... I don't use a cone driver above 2k usually.
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I think the sound transmission through any substance is due to it being moved (modulated) by the pressure on the other side? Anyway here is an explanation https://www.diyaudio.com/forums/mul...ned-layer-damping-mdf-ply-35.html#post6514534
Which from the perspective of a neutral observer is a trifle difficult if the driver, to quote the first post, is 'butted up against a sidewall'. Which is, objectively speaking, further ignoring the potential for the proximate air to mass-load the moving components.
Personally I tend to follow the approach of 'don't risk the potential for issues if you don't need to'. Rarely a major issue in the LF; as frequency increases, such things can become increasingly important. Context is the key here, so as ever YMMV.
Personally I tend to follow the approach of 'don't risk the potential for issues if you don't need to'. Rarely a major issue in the LF; as frequency increases, such things can become increasingly important. Context is the key here, so as ever YMMV.
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How would you achieve that with the driver 'butted up against the sidewall'? Unless you are taking damping material as a synonym for 'sidewall', which is not universally accepted as being grammatically or practically the case.
There would still be plenty of space away from that small area for the damping material and any reflections would be at an angle and be reflected away from the cone, not that such high frequency reflections would have much energy to modulate the cone. I don't think there is an issue, I would be interested to see or hear any evidence to the contrary.
Those are assumptions on your part that would depend on the angle of the sidewall and the location of the drive unit, nor consider any potential for proximity mass-loading of the moving components under certain conditions (note caveat). I suggest you try running a few FEM simulations with different types of loudspeaker, drive unit &c.; it can be quite interesting for many different aspects of design.
As noted, I have no particular truck in this race -quality design is about selecting what compromises, or potential compromises, are likely to suit a given set of requirements. In this particular case, as I said, my take is simply that it is sensible to avoid potential issues if there is no need to do so. Generally speaking I've not found it to be a major issue in the LF (not with most modern drive units anyway); as frequency increases, such things may, or can become increasingly important depending on what you are doing. Context as always comes into play, so YMMV.
As noted, I have no particular truck in this race -quality design is about selecting what compromises, or potential compromises, are likely to suit a given set of requirements. In this particular case, as I said, my take is simply that it is sensible to avoid potential issues if there is no need to do so. Generally speaking I've not found it to be a major issue in the LF (not with most modern drive units anyway); as frequency increases, such things may, or can become increasingly important depending on what you are doing. Context as always comes into play, so YMMV.
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Yes they are assumptions, but reasonable ones I think. I was presuming the side wall was at 90 degrees to the baffle. The question seems how much energy is directed towards it, close to the driver, and reflected directly back towards the cone?
I don't know why there is the impression that the driver's cone is somehow magically opaque to sound waves. No matter how rigidly the voicecoil holds the cone, it might as well be made of fresh air, as far as all but the lowest frequencies are concerned. Hence the need to obviate internal reflections and standing waves.
Different matter at low frequencies of course.
Different matter at low frequencies of course.
I don't think anyone has given that impression, I also don't think there's evidence that it's completely transparent.
- completely agree. A tried-and-true configuration that has been valid for 40 years is still valid. Now is not the time to go wobbly [a very wise woman once said].
A cone does not need to be "magically opaque" to sound waves. The energy radiated into the cabinet is exactly the same as the energy radiated to space. Naturally some of the internal cabinet sound is transmitted through the cone, just as it is also transmitted through the cabinet walls. The sound coming out of the cabinet is not corrupted or "un-pure". Unless there is an acoustical resonance (uncontrolled standing wave), there is not difference between the sound inside and outside the cabinet. Acoustical resonance is easy to control with acoustical damping.
j.