baffle reflection

[Professor smith]

B&W use separate tweeter enclosures to address the issue of reflections off the baffle. Why do most other high end companies leave the baffle perfectly untreated and even in some cases with sharp edges?
There must be a good reason for not addressing this issue. Cost and aesthetics doesnt count as a good reason because the whole idea of high end audio is to achieve great sound at any cost. A small minority use felt. At least that's an attempt.There is no question that any design involving drivers on a flat baffle suffers from this problem.

[Professor smith]

Is it seen as an insignificant issue which would take too much effort to resolve?

[Rudolf]

Originally Posted by Professor smith

B&W use separate tweeter enclosures to address the issue of reflections off the baffle. Why do most other high end companies leave the baffle perfectly untreated and even in some cases with sharp edges?

Good question, but wrong understanding of the initial reason to use separate tweeter enclosures:
There is no such thing as baffle reflection from the tweeter. A reflection off the baffle would need a wave with an incident angle greater zero. Where should that come from
The purpose for separate (and small) tweeter enclosures is to avoid baffle edge diffraction and uneven polar response generated by any large baffle and/or sharp baffle edges.

But don't ask me, why manufacturers don't care about it

Rudolf

[Professor smith]

Originally Posted by Rudolf

There is no such thing as baffle reflection from the tweeter. A reflection off the baffle would need a wave with an incident angle greater zero. Where should that come from

Rudolf

can you explain this? Im imagining the sound from the tweeter spreading out and hitting the baffle then being reflected. Maybe I'm using the word reflection in an non technical way.

[mdocod]

Modern B&W jobs with those Ti job tweeters are not all that special. Honestly, I think a pair of 600 series from back in the 90s when they didn't have that "fancy" tweeter operation sounded far better. At the end of the day, speaker placement in the room you are listening in, will have more of a useful effect on things than the effect of the baffle anyways.

IMO: worry less about the speaker design related issues, and more about speaker placement and amplification quality.

[speaker dave]

I'd say that B&W is a bad example as the seperate "pods" create more acoustical problems than they could ever solve. I believe that some customers look at them and think there must be some issolation or perhaps an acousticaal benefit so they have created a perception of doing something. In truth they give an unbaffled tweeter an opportunity for reflections off of the cabinet below. No thank you.

As to "why not felt", some companies do add them. As a manufacturer, your first question has to be whether grilles will be included or not. If so, then the grille on and grille off issue would hae to be addressed. It is hard to get a treatment that works well for both cases (although we did a pretty good job at Snell on a few models).

Hard edges on a square box give effects that can always be measured, but if you scatter the driver to edge distances they start to minimize. If you assume the listener will be off of the exact axis of the driver, this will likely minimize the effect further. For this reason I think many manufacturers are willing to ignore them. foam o felt on a baffle isn't the best looking thing and I think that further drives companies away from attempting it.

On another site (Classic Speakers), when I bring up the AR acoustic blanket, I always get a number of experts who proclaim that only power response matters and that small aberations in the direct field can't be heard. I am convinced they are wrong but at the same time the effect can be minor if you are careful with mounting (even on a sharp edged untreated cabinet).

Other companies such as Genelec do a very good job of adding a directional flare that give a good blend to the cabinet with a little bit of directivity to make the edges harder to see.

David S.

[dewardh]

Originally Posted by speaker dave

I always get a number of experts who proclaim that only power response matters and that small aberations in the direct field can't be heard.

It's got to be a little of both, eh? I listen mostly in the far (diffuse) field, and for amplitude response "diffraction effects" hardly seem to matter. Localization and "imaging" is still determined by the direct sound, though, and maybe diffraction sends confusing position clues. In the near field, though, diffraction peaks (and nulls) are more audible. And more position dependent . . .

[Rudolf]

Originally Posted by Professor smith

can you explain this? Im imagining the sound from the tweeter spreading out and hitting the baffle then being reflected.

Sound is travelling radially in all directions from the tweeter. But it does not travel in curves. If you imagine concentric rings/spheres around the tweeter center, sound has to travel perpendicular to them, NOT along them.

[Professor smith]

Originally Posted by speaker dave

In truth they give an unbaffled tweeter an opportunity for reflections off of the cabinet below. No thank you.
David S.

So why are you telling me reflections off the cabinet below can occur yet Rudolph says it cant occur on a baffle?

[Keriwena]

Because the tweeter effectively has no baffle so it can occur.

With a typical speaker, the tweeter is mounted on a baffle wide enough to accept the midrange driver, if not the woofer as well. In this case, the sound from the tweeter expands as a hemisphere since the baffle constrains the pressure waves to the plane of the baffle. Once the wave reaches the edge of the baffle, it starts to expand as a full sphere, and now we are pressurizing air behind the plane of the baffle.

With the tiny B&W tweeter pod, the sound expands as a sphere almost immediately, and thus there will be reflections when the wave hits the top of the main cabinet. You'll note the top of the B&W 800's main cabinet is curved, so these reflections are diffused and any interference they cause reduced.