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In Reply to: RE: Do all wideband drivers have rising response? posted by PaulF70 on February 15, 2015 at 20:38:44
No. I have Lowther DX4s and on open baffle, yes there is a rising response wich required a crossover to correct.
However, if you mount the DX4s in a back-loaded horns (I have Hedlund Horns), the backloaded horns can be configured (based on the size of the compression chamber and the use of felt in the compression chamber and in the backhorn) to balance out the sound to something that resembles a flat frequency response. I say resembles a flat response because I never measured the response, but the high frequencies were clearly not overstated relative to the rest of the frequencies.
One issue is the infamous Lowther "shout." This most likely is a spike in output around 2k hz that exists for the 8 ohm drivers. The 15 ohm Lowthers do not have such a response, so the genre of Lowther drivers does make a difference.
Retsel
Follow Ups:
Back-horn-loading doesn't take care of the general rising response issue with widebanders, or Lowthers in particular. (That's why Beauhorn front-loaded the driver as well. They claimed that's how Lowthers were designed to be used, and I thought they had about the best implementation.)
I think the shout is caused by both the rising response (we're talking about a general, continuous rise from 100-200 Hz all the way up to 4K or higher) as well as peakiness caused by cone-breakup and/or whizzer interactions. In any case most seem to point the finger at the whizzer regarding peakiness.
"Back-horn-loading doesn't take care of the general rising response issue with widebanders, or Lowthers in particular. (That's why Beauhorn front-loaded the driver as well. They claimed that's how Lowthers were designed to be used, and I thought they had about the best implementation.)"
It does, but you have to know how to adjust the speakers to do it. The Hedlund Horns were designed for the Lowther DX2 and the frequency response was quite flat for that speaker. But when I purchased the DX4s, I needed to add a couple small bags of sand to the compression chamber to reduce its size and "tip down" the frequency response.
All speakers work the same way. The size of the box that a speaker is mounted in determines the system Q, which determines the frequency response. A speaker mounted in an open baffle does not change its Q, thus, crossovers must be used to adjust its frequency response, but the compression chamber does.
I suspect that Beauhorns were designed with larger compression chambers and relied on the front horn to balance the frequency response. Beauhorns very well may be the best implementation of the backhorn speakers, although I never understood how it could work because the front horn was too small to raise the lowest frequencies. I think that the lack of folds in the Hedlund Horn put it in the category of better backhorn designs for Lowthers.
However, Lowthers mounted on open baffles clearly outperforms all backloaced designs, but eliminates the possibility of using the Lowther as a full range, do it alone, speaker.
Retsel
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