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


Thursday, November 5, 2015

Sound Transformer Plays "Comrade Down" by Eoto

Break-in and testing continues with "Comrade Down" by Eoto.

Sound Transformer With New Bass Drivers - More Testing

Here is a video of Herbie Hancock's "Vein Melter" playing on the Sound Transformer with new bass drivers.  This track has strong bass and percussion, perfect for breaking in the new drivers.  I used Howard Leight hearing protectors during this test because the sound level is quite high.

While shooting the video, I moved around the room to demonstrate how the sound is dispersed by the horns as well as how each individual horn in the system sounds.  Unlike the right channel, the left channel does not yet have a midrange horn so you get to hear how the bass horn sounds driven directly from the speaker output terminals without any crossover.  The right channel horns are connected through a simple L-C network with crossover at about 300Hz.  This video is ten minutes and fourteen seconds long.



If you stay with it long enough, you will see that the power level meters stay between 0.01 Watt and 0.1 Watt.  Even with that small input power, I had to use the Howard Leight hearing protectors.  These horns "throw" the deepest bass out in front and you can clearly hear that in the video every time I position the camera in front of the bass horns.

Wednesday, November 4, 2015

Sound Transformer Gets New Bass Drivers - Preliminary Test Results

A couple of weeks ago, I began to wonder how the Sound Transformer might sound with a set of new twelve inch drivers for the bass horns.  Having read that guitar speakers make great horn speaker drivers, I ordered a pair of guitar speakers from MCM Electronics that looked as if they might work well in this application.  The speakers were really affordable and arrived really quickly.  Here is the new Sound Transformer with MCM guitar speakers playing B. B. King's Bad Case Of Love:



New Folded Bass Horn - More Progress 6

Yesterday, I constructed a couple of corner reflectors for the New Folded Bass Horns.  Each reflector is intended to fit into the room corner and provide a reflective boundary that will change the direction of the sound radiating from the back of the main folded horn assembly and direct it out into the room through the matching pairs of horn flares on each side of the main assembly.  While the assembly is being modified with the addition of the corner reflector, the polyester fill is removed from the back chambers that were used with the original Sound Transformer bass horns and installed in the back chamber for the New Folded Corner Horn driver.

Here are some photos of the corner reflector being set up behind the folded horn assembly for the right channel.

New Folded Corner Bass Horn - Corner Reflector In Place
New Folded Corner Bass Horn - Corner Reflector In Place
Viewed from above, the shape of the twin side horn flares can be seen in the following photo:

New Folded Corner Bass Horn - Corner Reflector In Place
New Folded Corner Bass Horn - Corner Reflector In Place
With the corner reflector in place and the main folded horn unit repositioned to provide the proper dimensions for the side flares, the 4' x 4' plywood sheet is placed over the top of the horn.  As you can see, the plywood also happens to be a yard sale sign we have used several times.

New Folded Corner Bass Horn - 4' x 4' Top Panel In Place
New Folded Corner Bass Horn - 4' x 4' Top Panel In Place
Here is one of the back chambers from the Sound Transformer with KLH driver and polyester fill removed.  The back chamber will serve as a stand for the midrange horn, also from the Sound Transformer, currently being tested with the new folded bass horn.

New Folded Corner Bass Horn - Stand For Midrange And Poly Fill
New Folded Corner Bass Horn - Stand For Midrange And Poly Fill
The back chamber made from part of an old Technics speaker is now stuffed with the polyester fill.
The empty Sound Transformer back chamber is now the stand under the midrange horn.

New Folded Corner Bass Horn - Back Chamber With Poly Fill
New Folded Corner Bass Horn - Back Chamber With Poly Fill
The back chamber is now positioned at the correct height for the eight inch driver presently being used with the folded bass horn.  By the way, this eight inch speaker was removed from a Boston Acoustics Unity subwoofer cabinet.

New Folded Corner Bass Horn - Back Chamber And Eight Inch Driver
New Folded Corner Bass Horn - Back Chamber And Eight Inch Driver
Now the right channel has a corner reflector and polyester fill in the back chamber.  The stack of weights on the small square of plywood are intended to correct a little warping in the "Sale New And Used" cover panel.

New Folded Corner Bass Horn - Corner Reflector And Stuffed Back Chamber
New Folded Corner Bass Horn - Corner Reflector And Stuffed Back Chamber
The same changes have also been made to the left channel folded bass horn.  Now for more listening tests!