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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."



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Showing 3 responses by avanti1960

avanti1960
1,532 posts
 
wide baffles reflect more midrange back into the room because the larger wavelengths cannot disperse around to the back of the enclosure.
this creates an uneven response at midrange frequencies that must be filtered with a BSC circuit in the crossover to yield a neutral frequency response.
all things being equal it is better to have a narrower baffle and reduced BSC filterig.
avanti1960
1,532 posts
 
the excellent wide baffle designs succeed in spite of the wider baffle not because of it.  
wider baffles create the need for additional crossover components and complicate the voicing recipe.  
wider baffles do allow for larger woofers and enclosure volumes which enables excellent low distortion bass.  
imaging and high frequency dispersion is handicapped as well by wider baffles.  they require more care and precision in placement and have a more difficult time disappearing than narrow profile speakers.  
in other words more expense in design, engineering and user effort are needed for a successful wide baffle system.  
avanti1960
1,532 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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