Saturday, December 19, 2015

Latest Find: Pair Of Altec Lansing Corona 893A Acoustic Suspension Loudspeakers

These turned up at the local transfer station.  Someone had left them at the edge of the small covered storage area and they were getting wet from rain blowing in from the East.  This is a quality design from about 1969 with treated cloth surrounds instead of the molded foam ones.  They are finished in the original black walnut.

Pair Of Altec Lansing Corona 893A Acoustic Suspension Loudspeakers
Pair Of Altec Lansing Corona 893A Acoustic Suspension Loudspeakers
Of course, I had to try out the woofers in the Folded Corner Bass Horns.  They worked quite well.  The upper frequency cutoff of these ten inch woofers on this horn appears to be a little over 250Hz.

Altec Lansing Corona 893A Woofer #1
Altec Lansing Corona 893A Woofer #1


Altec Lansing Corona 893A Woofer #2
Altec Lansing Corona 893A Woofer #2
Here is one of the woofers mounted on the New Folded Corner Horn.


New Folded Corner Horn - Altec Lansing Corona 893A 10" Woofer
New Folded Corner Horn - Altec Lansing Corona 893A 10" Woofer
It appears as if any reasonably good woofer works well as a driver for this horn.  Of course, "power handling" is not really a consideration because the music playback is pretty loud at input power levels of less than 1/100th to 1/10th of a Watt.

I now have the KLH CL-3A 12" woofers back in the horns.  The upper frequency cutoff for the KLH 12" woofers is around 350 Hz.  The Altec Lansing 893A pair have been reassembled and cleaned up and are near mint.



Friday, December 18, 2015

New Folded Corner Midrange Horn - Twin Back Chambers

Back chambers for the twin drivers in the New Folded Corner Midrange Horn should help to improve overall performance of the horn.  PVC pipe and 1/8" Masonite form the mounting flange and walls of the back chambers while a disc of mahogany plywood provides a cover.

First, it is necessary to plug all of the holes in the throat flange:


New Folded Midrange Horn - Throat Flange
New Folded Midrange Horn - Throat Flange
 A new flange is cut out of 1/8" Masonite.  Four flat-head wood screws fasten driver, flange, and pvc pipe together.  The assembly is pictured below set upside down on the throat flange.  It is necessary to chamfer the edge of the flange to allow clearance for the driver surround.


New Folded Midrange Horn - Flange-Driver-PVC Pipe Assembly
New Folded Midrange Horn - Flange-Driver-PVC Pipe Assembly
 The assembly is positioned over the throat flange for drilling and countersinking.


New Folded Midrange Horn - In Position For Drilling and Countersinking
New Folded Midrange Horn - In Position For Drilling and Countersinking
 Two 1/16" holes are drilled through the PVC for the driver leads.

New Folded Midrange Horn - Holes for Leads
New Folded Midrange Horn - Holes for Leads
Wires are fed through the holes and ends stripped.

New Folded Midrange Horn - Lead Ends Stripped
New Folded Midrange Horn - Lead Ends Stripped
 The back chamber assembly is now in position and fastened.

New Folded Midrange Horn - Back Chamber Assembly Fastened
New Folded Midrange Horn - Back Chamber Assembly Fastened
 The mahogany plywood disc is provided with black electrical tape as a gasket for a reasonably tight fit in the PVC pipe.

New Folded Midrange Horn - Back Chamber Cover
New Folded Midrange Horn - Back Chamber Cover
The twin driver and back chamber are already installed.  Here is the setup to test impedance as a function of frequency.


It will be interesting to see how the measured impedance vs frequency plot compares with the one predicted in Hornresp.

Sunday, December 6, 2015

New Folded Corner Bass Horn - Installing KLH CL-3A Woofers In Both Horns

During folded bass horn testing so far, I have been using two different eight inch woofers, one by Altec Lansing and one by Boston Acoustics.  Today, I decided to get an idea how the two horns might sound with matching drivers.  The KLH woofers removed from CL-3A acoustic suspension boxes are a good enough match for testing purposes.  I already have matching back chambers cut away from a pair of old Technics boxes.  Here is the right channel getting the 12 inch CL-3A woofer:


New Folded Corner Bass Horn - KLH CL-3A Woofer & Technics Back Chamber
New Folded Corner Bass Horn - KLH CL-3A Woofer & Technics Back Chamber
New Folded Corner Bass Horn - KLH CL-3A Woofer & Technics Back Chamber
New Folded Corner Bass Horn - KLH CL-3A Woofer & Technics Back Chamber

Here is the left channel being set up with an identical woofer and back chamber:


New Folded Corner Bass Horn - KLH CL-3A Woofer & Technics Back Chamber
New Folded Corner Bass Horn - KLH CL-3A Woofer & Technics Back Chamber
I also put an equal amount of polyester fiber fill into both back chambers.  Now for some listening tests!