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wide baffles and baffle step

Lengthy quotation from Peter Comeau, designer at Wharfedale.  Makes a lot of sense to me...

"Th[e] larger ported box, with its subsequent increased baffle size, helps solve a major problem in modern speakers, namely, the baffle step.

I grew up with large speakers with wide baffles, but, as speakers reduced in size over the years I noticed that something was missing from the sound and, when I stuck my head firmly into speaker design, I began to understand the acoustic problems caused by the baffle step.

Put simply, as the baffle size decreases, the point at which the acoustic radiation changes from hemispherical to spherical goes up in frequency. It also becomes sharper and narrower in bandwidth as the sides of the cabinet, and the walls and floor of the room, are further removed from the equation. So, this 6dB step in the power response becomes acoustically more obvious.

I believe that a thin speaker always sounds thinner throughout the midrange when directly compared to a speaker with more generous baffle width. Of course, as designers of modern, slim speakers, we compromise by adjusting for the baffle step in the crossover, but in doing so, we also compromise sensitivity. What starts out as a 90dB at 1W drive-unit often ends up as an 85dB system once we have adjusted for the power loss due to the baffle step."



128x128twoleftears
audiokinesis
2,746 posts
 
Tomic601, my understanding is that sound waves are longitudinal pressure fluctuations, not transverse waves (even though we tend to draw them that way), and therefore there is no phase change when they reflect or diffract.   

There is of course a time-delay built into the path length to the reflecting or diffracting discontinuity, and that time delay works against preservation of time and phase coherence.   

Imo the solution is to minimize edge diffraction effects either by having  minimal baffle dimensions or large-radius roundovers or sufficient directivity to avoid significant cabinet edge interaction in the first place.  Since I like the other benefits which come with having a wide baffle, I try to figure out ways to minimize the downsides. But it's a juggling of tradeoffs, and arguments can be made for either side.   

Duke
wolf_garcia
6,711 posts
 
For the record, around 100% of interior designers prefer ceiling speakers...sadly.
wolf_garcia
6,711 posts
 
For the record, nearly 100% of interior designers prefer ceiling speakers. Sadly.
twoleftears's avatar
twoleftears OP
5,318 posts
 

This is what I think is sad.

https://www.bluebirdmusic.com/edit/files/images/gallery/spendor_str_nov_18.jpg

avanti1960
1,482 posts
 
@audiokinesis
With respect to baffle step compensation, unless the baffle is wide enough to impinge on the limits of room space and physical practicality there will be an audible 3db loss of all frequencies below the baffle step frequency. For example the baffle would need to be 33.76 in. wide for a frequency of 400 hz. With that width, frequencies below 400 hz will drop off by 3db relative to frequencies above 400 hz.
Lower baffle step frequencies will require a wider baffle (increasingly less practical), the baffle can decrease in width for higher baffle step frequencies (increasingly practical).
Example, 9 in. width for a 1500 hz. baffle step frequency, easily managed physically and electronically).
With the loss in output of all frequencies below the baffle step frequency, some form of compensation will be required. A BSC circuit is a popular and effective method for doing so.

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