Saturday, March 28, 2015

The Sound Transformer Gets A Bass Driver With Two Voice Coils - STEREO

By replacing the bass driver with an Altec Lansing bass driver from a computer sound system subwoofer, it is now possible to hear stereo recordings by combining the bass signals from the left and right crossover networks in a single bass driver.  Here is the back chamber held on with stretch rubber cords.

Sound Transformer Back Chamber
Sound Transformer Back Chamber
With the back chamber removed, you can see the KLH 12-inch driver used in the original design for this bass horn.

Sound Transformer With Back Chamber Removed
Sound Transformer With Back Chamber Removed
With the KLH driver removed, you can see the horn throat.


Sound Transformer With Back Chamber Removed
Sound Transformer With Back Chamber Removed
Finally, here is the Altec Lansing 8-inch driver installed.


Sound Transformer With Altec Lansing 8-Inch Driver Installed
Sound Transformer With Altec Lansing 8-Inch Driver Installed
This is a much smaller bass driver but seems to be an even better match for the bass horn.  The stereo is quite good, even though I have no tweeter for the left channel.  Here is what the stereo setup looks like.

Sound Transformer Now In Stereo
Sound Transformer Now In Stereo
I still plan to make two bass horns.  Probably, I will make two more identical horns using the one pictured here as a mold former.

The smaller, 8-inch driver appears to be superior to the larger 12-inch driver for a number of reasons.  With the 12-inch driver, the low frequency falls off abruptly below about 45Hz.  There is also a sharp notch at between 72Hz and 80Hz depending upon microphone placement and/or horn placement in the room.  While listening to low frequency sine waves, I discovered that there is quite a bit of nonlinearity in the 12-inch woofer revealed by harmonics clearly audible at low frequencies below cutoff.  With the 8-inch woofer installed, I get useful output down to about 35Hz with much less harmonic distortion.  There is also less of a peak around cutoff frequency.  I believe the moving mass is lighter in the smaller driver.  In addition, the smaller cone is likely to be moving more as a unit than the large cone is able to especially with the horn load.  The bass is cleaner overall from the 8-inch driver while loaded by this horn.

It helps a lot that the Altec Lansing driver has dual voice coils because, at least above 400Hz, we can get an idea how this system will sound in stereo.

No comments:

Post a Comment