While waiting to buy/build/develop the hardware and software to acquire a full polar frequency response on the dipole baffles some limited investigation of their off-axis response is feasible. In this case we'll take a look at the amplitude response in the plane of the 1S6T baffle.
With a dipole baffle we expect to see significant reduction in frequency response amplitude in the plane of the baffle. Additionally, with a one-sided baffle, such as was tested, we expect to see some differences in the dipole cancellation effects when the 'speaker-side' is compared to the 'baffle-side' edge response.
The most important significance of these plots is the demonstration of the side-attenuation that is obtained with the dipole baffles. In the lower frequency range the signal levels are seen to be less than 1/100th (-40dB) of the on-axis response. This has clear implication for room interaction effects - which, of course, is one of the reasons to use a dipole baffle.
The following overlayed plots have amplitude scales that are extremely compressed compared to all other plots in the Study. Please pay close attention to the amplitude scales, as the edge responses are very low compared with the on-axis response.
Speaker-side versus Baffle-side Edge Comparison. 1/12 Octave smoothed.
The baffle-side edge response is seen to be significantly lower than the speaker-side edge response, which might be expected from a one-sided baffle. Over the range of low and mid-frequencies the difference in attenuation approaches an additional -10dB for the baffle-side. This baffle has been listened to in both orientations in the Listening Room, that is, with either the speaker edge or the baffle edge closest to the sidewalls.
The orientation which sounds best is with the baffle-edge closest to the sidewalls. Is this any wonder, since the baffle-edge presents even less sound energy to be reflected from the sidewalls.
The two overlayed plots below present 1m, 2m and 3m distance measurements for the two different speaker edges.
Speaker-side Edge Comparison. 1/12 Octave smoothed.
Baffle-side Edge Comparison. 1/12 Octave smoothed.
The Gymnasium Measurements - Over the Top.
The Gymnasium Measurements - Let's Get Foamed.
The RD75 Dipole Baffle Study - Table
of Contents
Acoustic Line Source Research - Table of Contents.
