Thursday, April 28, 2016

Progress On Construction Of The New Straight Midrange Horn

With the large flares of the New Straight Midrange Horn construction essentially completed, I begin construction of the smaller flares of the horns.  Using the same techniques employed on the Sound Transformer Bass Horns, a pair of flanges of the same dimension as the smaller flange on the larger flare are cut out on the table saw.  By beveling the edges of the square opening in the center, I will have the flange interior edge flush with the faired exponential expansion.  Four pairs of ribs are cut at the proper angle on the chop saw.  The ribs will be scribed to the exponential curve using a plywood pattern but only after they are fastened into position between the flanges.  To get the ribs to fit, it is necessary to cut away a bit at the small end of the horn.  Here is one of the horns set up for marking with the pattern.

New Straight Midrange Horn - Throat Flare Progress
New Straight Midrange Horn - Throat Flare Progress
After marking all four of the ribs for the curve as well as numbering the matching parts so they can be reassembled later, the rib curve is cut out on a band saw.


New Straight Midrange Horn - Throat Flare Progress
New Straight Midrange Horn - Throat Flare Progress
The series of small cuts to the line make it easier to "leave the line" without cutting away too much.  Here are the four ribs after cutting the curve.


New Straight Midrange Horn - Throat Flare Progress
New Straight Midrange Horn - Throat Flare Progress
Now, the horns are reassembled so the other two pairs of ribs can be positioned and marked.


New Straight Midrange Horn - Throat Flare Progress
New Straight Midrange Horn - Throat Flare Progress
All eight rub curves are sanded by hand to the line using a sanding block.


New Straight Midrange Horn - Throat Flare Progress
New Straight Midrange Horn - Throat Flare Progress
Here are the horns with all eight sanded ribs fastened in.  The cardboard trapezoid will be used to mark four plywood sides.


New Straight Midrange Horn - Throat Flare Progress
New Straight Midrange Horn - Throat Flare Progress
Here is one of the throat flares set on top of a mouth flare.


New Straight Midrange Horn - Throat Flare Progress
New Straight Midrange Horn - Throat Flare Progress
Tomorrow, I will cut the sides for the throat flare.

Monday, April 25, 2016

Latest Progress On Construction Of New Straight Midrange Horn Pair

Today, I cut out the last four flare sides and custom fit each one into its respective horn.  Following that, I "dry-assembled" the horns several times, refitting here and there, until I got a reasonably good fit for the joints.  After cutting out "throat square" blocks to hold the sides in place, here is what the horns looked like.


New Straight Midrange Horns - Sides Dry-Assembled
New Straight Midrange Horns - Sides Dry-Assembled


New Straight Midrange Horns - Sides Dry-Assembled
New Straight Midrange Horns - Sides Dry-Assembled

With all of the sides marked for proper positioning, I applied adhesive to the joints.  It is necessary to keep the adhesive away from the square blocks so they will come out tomorrow after the glue dries.


New Straight Midrange Horns With Adhesive Applied
New Straight Midrange Horns With Adhesive Applied
It will get quite cold in the barn attic overnight so I have moved the horns inside so the glue can set under more ideal conditions.


New Straight Midrange Horns With Adhesive Curing
New Straight Midrange Horns With Adhesive Curing
Tomorrow, I will start on the smaller portions of the horns.



Sunday, April 24, 2016

Still More Progress On The New Straight Midrange Horn Pair

Because the Lauan plywood is 1/8" thick, I can cut out the horn flare sides with a utility knife.  As in the Sound Transformer Bass Horns, the first two sides for each horn are trapezoids and fairly simple to cut even without a straight edge.  Here is an image of two of the trapezoids ready for fitting.  The only dimension that needs to be trimmed is the length.  Each end of the side needs a beveled edge that I can easy machine with a sanding block.


New Straight Midrange Horn With Two Trapezoids
New Straight Midrange Horn With Two Trapezoids
Here is a horn with trapezoids in position.


New Straight Midrange Horn And Two Trapezoids
New Straight Midrange Horn And Two Trapezoids


New Straight Midrange Horn And Two Trapezoids
New Straight Midrange Horn And Two Trapezoids
The next thing to do is to fit a corrugated cardboard pattern for the other two sides.  Here is the cardboard pattern being fitted by scribing, cutting, and sanding the edges until the pattern fits.


New Straight Midrange Horn - Fitting Cardboard Pattern
New Straight Midrange Horn - Fitting Cardboard Pattern
The cardboard pattern will be used to mark the first side on the Lauan panel.  The first plywood side will be cut slightly larger than the cardboard pattern for a more accurate fit than can be achieved with the cardboard.

More Progress On New Straight Midrange Horn Pair Construction

I cut two smaller square flanges for the smaller end of the horns.  The square hole in each flange is too small to be cut out with the table saw so I used a scroll saw with the shoe set to an angle to match the flare angle.  I made the square hole a little smaller than it needs to be so I can fair it to the horn sides after they are in.


New Straight Midrange Horn With Small Flange
New Straight Midrange Horn With Small Flange


New Straight Midrange Horn With Small Flange
New Straight Midrange Horn With Small Flange
I am playing some music here through the original Sound Transformer Horn Stereo Pair and have to turn the volume way down because I am standing right in front of the horn while attaching the small flange.

Thursday, April 21, 2016

Progress On New Straight Midrange Horn Pair Construction

Today, I cut the plywood square frames to make the large flanges for the pair of New Straight Midrange Horns.  All I had to do is set the table saw fence for the right width and carefully lower the plywood squares onto the blade to start the cut at the right position so as not to overcut each of the four edges.  I completed the cutting with a scroll saw.  Here are the two horns, each with eight ribs tacked in place so I can position the smaller flanges and correctly align everything before drilling and screwing the flanges to the ribs.


New Straight Midrange Horns - Ready For Small Flange Alignment
New Straight Midrange Horns - Ready For Small Flange Alignment


New Straight Midrange Horns - Ready For Small Flange Alignment
New Straight Midrange Horns - Ready For Small Flange Alignment
Tomorrow, I will cut the smaller flanges.  I have already purchased a Lauan plywood sheet for the curved walls of the horn.


Wednesday, April 20, 2016

New Project - A Pair Of Matching Straight Midrange Horns

I built the New Folded Corner Midrange Horn with the intent of eventually building a second matching one for stereo. However, I have decided to build a pair of Straight Midrange Horns with the same flare rate as the original New Folded Corner Midrange Horn. The main reason for this is that I want to compare the New Folded Corner Midrange Horn with a Straight Horn version. The second reason is that the New Folded Corner Midrange Horn is so efficient, being corner placed, that it is several dB louder than the New Folded Corner Bass Horn with the KLH CL-3A woofer. The third reason is that I want to apply the same construction technique to a stereo pair of Straight Midrange Horns that I used with the Straight Bass Horns, otherwise known as the Sound Transformer Stereo Pair. I decided to build all of the parts at once for two Straight Midrange Horns. Here is the progress so far.

Pair Of Matching Straight Midrange Horns - All Sixteen Ribs Cut Out On Band Saw
Pair Of Matching Straight Midrange Horns - All Sixteen Ribs Cut Out On Band Saw

The band saw curved cut requires some attention to "leave the line" and not take too much.  Actually, before cutting the curved sides, I cut both ends of the identical ribs at the correct angle on a chop saw.  I used pine scraps I have had here for quite a long time.  After cutting the sixteen ribs, I clamped four at a time and sanded the curves to remove variations due to a "wandering" band saw cut.  Here is the setup using clamps and a sanding block.


Pair Of Matching Straight Midrange Horns - Four Ribs Clamped For Sanding
Pair Of Matching Straight Midrange Horns - Four Ribs Clamped For Sanding
These ribs will hold the sides of the mouth flare of the Straight Midrange Horns.  The mouth flare length is one-half of the Straight Midrange Horn total length.  The mouth flares will have a square flange at each end.  The smaller, narrower "throat" portion of the Straight Midrange Horns will also have a flange at each end.



Monday, April 4, 2016

New Folded Corner Bass And Midrange Horns Play - "Walking On The Moon"

Here is a recent recording of the New Folded Corner Bass and Midrange Horns playing "Walking On The Moon" by The Police.  A Sony F-97 measurement microphone captures more of the bass than the camera microphones do.  A crossover removed from a Pioneer CS-88A loudspeaker has been converted from four-way to three-way.  The magnificent Pioneer SX-1280 receiver provides amplification, although it does not have to provide very much as you can see in the video.  The output meter for the right channel doesn't read above 0.1 Watt.