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ATTENTION: Continuum Builders
I have received three complaints of the Continuum being too bright in the treble. Two of these units were measured, and their results were essentially identical - showing the entire tweeter level about 1.5-2 dB higher than flat for the summed response. However, my sample, and Jim Salk's sample measured much flatter through the treble, as I intended the speaker to be.
It makes me wonder if the RS28a varies in sensitivity a couple of dB. I know I have heard four other versions of the speaker from other builders and never noticed a high frequency over-emphasis in them, but the I believe the reports and measurements from the ones that have contacted me about it, as it was enough of an emphasis that they noticed it, and the measurements appear to confirm it.
As a result of the first person to request a way to lower the tweeter I did a little modeling to come up with the best solution. Since the entire tweeter level is high and not just a certain region (more evidence for varying sensitivity), the best solution is to leave the series resistor in the RC circuit unchanged and instead add a parallel resistor (like you see on an L-Pad) between the RC contour circuit and the tweeter. In fact, this resistor could be placed directly across the tweeter's terminals if that works best. We found that a 15 ohm resistor was perfect for the amount of change needed and lowers the overall tweeter level by 1.5dB based on measurements.
So, if you have felt that the Continuum was bright, but haven't said anything, you may be affected in the same way as these others. Add the 15 ohm resistor and it should correct the issue. The response of the Continuum above 500Hz was designed to be extremely flat as a reference.
For what it's worth, a 20 Ohm would trim the highs a bit less and a 10 ohm a bit more. Feel free to tweak as desired for the balance that seems right in your room and system.
Jeff B.
It makes me wonder if the RS28a varies in sensitivity a couple of dB. I know I have heard four other versions of the speaker from other builders and never noticed a high frequency over-emphasis in them, but the I believe the reports and measurements from the ones that have contacted me about it, as it was enough of an emphasis that they noticed it, and the measurements appear to confirm it.
As a result of the first person to request a way to lower the tweeter I did a little modeling to come up with the best solution. Since the entire tweeter level is high and not just a certain region (more evidence for varying sensitivity), the best solution is to leave the series resistor in the RC circuit unchanged and instead add a parallel resistor (like you see on an L-Pad) between the RC contour circuit and the tweeter. In fact, this resistor could be placed directly across the tweeter's terminals if that works best. We found that a 15 ohm resistor was perfect for the amount of change needed and lowers the overall tweeter level by 1.5dB based on measurements.
So, if you have felt that the Continuum was bright, but haven't said anything, you may be affected in the same way as these others. Add the 15 ohm resistor and it should correct the issue. The response of the Continuum above 500Hz was designed to be extremely flat as a reference.
For what it's worth, a 20 Ohm would trim the highs a bit less and a 10 ohm a bit more. Feel free to tweak as desired for the balance that seems right in your room and system.
Jeff B.
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