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General speaker questions for audio and home theater.

RE: JBL123-A/Klipsch 400 speaker build HELP

Baffle step is a decrease in on-axis response for frequencies below a cut-off point determined by the width of the baffle. For example, your cabinets there, if they are about 15" wide, will have a baffle step frequency of about 300hz.

To correct for this, they use a technique called baffle step compensation. Since in the passive domain we can only cut and not boost, the trick is to attenuate all frequencies ABOVE the baffle step frequency in order to get a smooth response.

Since you're using an active crossover at 600Hz with no DSP capabilities, you have no baffle step compensation. If you're trying to 'compensate' by adding "more bass" at 600 down, then you're ultimately going to be creating a midbass hump between 300 and 600Hz. This of course assumes your crossover to the midhorn is summing flat in the first place...

The big question is: Does this midhorn have a passive low/high pass or just a low-pass filter. Aka, was it designed with a specific woofer in mind (like the LaScala bottom end)? Likely so... and if that is the case, you need to "tune" the crossover for the 123A, or in other words, you need to get the acoustic response of the woofer to work with the acoustic response of the midhorn so that the response sums flat. If there is already a high-pass filter in place on the midhorn, this means the crossover point, slope and "Q" (shape) of the lowpass on the woofer is anything but arbitrary. If this is the case you can experiment with the knobs on the Urei for 100 years and never get a flat response.

Cheers,
Presto


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