SDA SRS1.2 with Erse SuperQ inductor modification

Recently I changed the stock 16.8 mH air core inductor in the 1.2's in favor of a 17 mH Erse SuperQ iron core inductor resulting in increased low bass, tigher bass, as well as unmasking some of the lower midrange.

However, my initial impression was the speaker sounded a little lean or thin in the warmth department so I took a look at what was going on with the SDA XO response.

I measured -20 dB tones at the output of the XO to the dimensional array produced by the Carver amp. The measurments with the stock inductor are the actual dB levels. The measurements for the Erse 17 and the modified Erse 17 are dB gains or losses referrenced to the stock inductor.

Note that above 80 Hz the XO really starts to roll off and attenuate the SDA. At 100 Hz the output to the array is down 6dB or 1/4 the power at 20 Hz.

With the 17 mH Erse, note the signal increase below 100Hz due to the much lower DCR. There is 3-4 dB of gain or more than twice the power below 100 Hz. Also note the reduced power above 100 Hz with 2-4 dB loss, or 1/2 the power between 100 and 800 Hz. I think this is the reason the speakers sound thin on some recordings.

I decided to remove coils of wire from the Erse and ended up taking off 16 turns (6'10") of wire until I reached a point where the frequency response above 100 Hz was in between the stock inductor and the Erse 17 mH. Note the lower bass increased just slightly (lower DCR) and above 100 Hz the response was only down 1 dB from the stock inductor.

Listening proved the modification was perfect. It added just a hint of upper bass to flesh-out the sound and maintained the super tight low bass and punch from the lower DCR erse coil.



Note I also measured the stereo array response in the far right column. It's running much more "full range" than the dimensional array. In the lower bass it has about the same output but as frequency climes it continues to produce a healthy signal.