Thursday, November 19, 2015

New Folded Bass Horn - Testing The Two Found Drivers

Today, I removed the eight inch drivers from the New Folded Corner Horns and set up to measure the Thiele-Small parameters.  The two drivers that I found that worked the best in these horns were removed from subwoofer cabinets, one made by Altec Lansing and the other by Boston Acoustics.  I thought it would be interesting to try these two drivers in the Hornresp simulator but, before I could do that, I needed to measure Thiele-Small for both in order to input the driver parameters for the simulator.

Here is the setup for testing the Altec Lansing eight inch woofer.

New Folded Corner Bass Horn - Altec Lansing Driver Setup
New Folded Corner Bass Horn - Altec Lansing Driver Setup
I used the Lepai 2020A amplifier to drive the speaker under test through a series-connected power resistor.  The power resistor measures 10.0 Ohms on my Fluke 87 volt-ohmmeter.  Sine-wave levels during testing are all under 400mV so a power resistor is probably not necessary.  For a variable-frequency sine wave source, I used a function generator app on the iPad Air.  I also used an old Southwest Technical Products function generator I have had for a long time.  The SWTP one is easier to use to quickly find null points at resonance.  The iPad App allows very precise frequency settings via touch keypad.  I use a freeware program called DPC to calculate the T-S parameters from measurements made with the above setup.

After completing the simulation in Hornresp, it is interesting to find that the two different drivers appear to perform nearly identically in the simulated horns.  However, there are some important differences that we will get into later.

You can listen to how the horns sound at the following blog post:
http://paulsherman.blogspot.com/2015/10/new-folded-bass-horn-more-progress-5.html


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