Friday, July 29, 2011

What are these?

Every once in a while you need to do something different so I spun these upon request for a friend.  Some of you might be saying crossover inductors, others that know me better may be thinking super tweeter field coil or cartridge electromagnet.  Maybe showing the rest of the parts will let you in on the secret.

All joking aside, here they are assembled and ready to be installed under the cathode of a filament biased 104D. 

We should be able to listen to them this weekend in the land of walter and I will report back.  With an amp of current they drop 6.2V and hit a whopping temperature of 170F.  Funny thing is the first pair got so hot the bondcoat on the wire cut loose which is why a bit of aluminum and brass heatsinking was used.

Thursday, July 28, 2011

Just when I had cleared some space in the shop....

these crates arrived... but I am honestly very excited. It is extremely difficult to find a professional cabinet maker these days. This guy worked form my CAD drawings.. sent revisions... stain samples... can use whatever wood I specify.. timely.. just totally professional...

these were made to be "espresso".. always yummy in my book... and the wood is super high quality birch... very low voids... pre-veneered so that the veneer never peels away..

the corners are all mitered at 45's on a CNC so that it all fits together perfectly and the grain wraps around the cabinet.. a super nice touch...

bracing is set in with dado joints... very stiff and strong... all in all, I am very pleased...

oh, what goes in it? yes, I guess I should mention that.. basically just a generic woofer cabinet... designed around the Altec 604 and the Altec 416... these guys make great bass in all but the largest rooms... and some people just do not want nine foot straight basshorns... finally a nice option...

finished photos and plots soon...


Tuesday, July 26, 2011

The First Strain Gauge?

On a recent trip to NYC, Frank (the guy who suspends a broomstick from a piece of fishing line and calls it a tonearm) brought me a very special gift from the Pfanstiehl Chemical Company of Waukegan, Illinois.  Inside this box is to date the earliest sample I have seen of a strain gauge phono cartridge and matching power supply.

For one year in 1946 Capehart used a Pfanstiehl strain gauge cartridge in one of their high end 78 record changers before switching to a GE variable reluctance cartridge.

Since the phan-Tone is a flip-over cartridge (with two individual gauges) that can play both 78's and 33/45's it must date a few years after the Capehart misfire so there still may be earlier ones out there.   This one is still a very cool vintage mono cartridge with a sapphire stylus on either side that tracks at a mere 7 grams and I want to thank my brother for the wonderful gift.

Friday, July 22, 2011

Western Electric 9A Receiver


no.. not really like the NAD, Pioneer, or even Marantz receivers from back in the day... this one is WAY older...

super thanks to my friends from the "other South" for this fine specimen to scan and model... it really helps in getting it *just* right...

so what material do you think we should use? Bronze? Bronze sounds good, right? and this piece has to be strong - so Aluminum will just not do... and steel is out because it really should be non-magnetic when this close to the driver.. so, yeah.. let's cast this beautiful object in Bronze..

which gives away what I was doing in Hope, Arkansas at the Klipsch Museum.. taking some detailed measurements... PWK had one of these, too...


Wednesday, July 20, 2011

My Aida

 I love honest passion.
The audiophile nearfield version.
It rocked to Boston... or was it Journey... I get confused.
Apparently the "reallyreal deal" took too many D cells and was a bear to carry so we heard the box in the first pic with LED's pegged as a compromise.

At least one passionate person got it.

He inspired me.

Monday, July 18, 2011

Quad ESL 57 Eye Candy

While in DC for the CAF, I had the pleasure of meeting Wayne Piquet and Kent McCollom two of the guys who rebuild Quads here in the states.  On the last day we were able to hear Wayne's new panels in solid maple frames made by one of the "andy's" and I have to say they were a huge leap forward in both sonics and efficinecy over the stock panels they replaced.

We started setup with a pair of forward facing single panels and then put the doubles in front to confirm phase.

Then we returned to the original setup of the three panels with a single facing forward and the doubles facing the outer wall.

Saturday, July 16, 2011

Why do they call it a bug screen?

So I was pulling out a pair of the monster alnico JBL 2482's for a friend... these babies have a big 4" coil and can handle sixty watts at 300Hz... considering they are over 110dB/watt on a horn, that is, what? 130dB or so? crazy stuff.. so when I found this inside:

all I could picture were the bugs at a Black Sabbath show... headbanging away.. and trying to get closer to the speakers to make it louder and louder...


Thursday, July 14, 2011

The Book on the 301

I put this nice little book to good use last week and was amazed how far we have come (gone?) in our instruction manuals.

It was such a nice bound book that surely gave a pride of ownership.  Now I have to be honest in why I was actually drawn to it.  It had nothing to do with the fact that we were using a 301, that was just odd luck.  It just happened to be the right thickness to prop up the RS labs arm for a quick comparison. After we were done, I cracked it open to see all the nice stuff inside.

Wednesday, July 13, 2011

Capital Audiofest, Best room at the show.

I guess this is going to be a non-traditional show report and the best way to start it out is with a non-traditional room.  I skipped Axpona in my own backyard to mow my lawn, yet drove 300 miles to this show for one reason and that was to see old friends and make some new ones.

The first room I hit was the local DC audio guys and upon entering the room I saw my old friend Roscoe from joenet and the NYnoize shows, beyond that I met a few monikers I knew but no faces.  After enjoying a quick chat I moved on with a beverage in tow.

The best part of this room was the diversity and the non-commercial nature.  It was just a bunch of friends hanging out having a good time.  

On Saturday they were playing a pair of Basszillas and the next day new speakers appeared, not because the sound was bad but because it was a group of kids who could share their toys in the same sandbox.  Compare this to the tension and stress in rooms shared by manufacturers and they get an A+.

Every time I went into the room there was something different playing from both the music and equipment perspective.  The beauty of it all was for my tastes, the sound bettered the bulk of other rooms at the show. 

I regret not getting to hear any tapes, but just the presence of a deck screams passion from at least one member of the group.

Now to get back to my friend Roscoe and a story of poetic justice.

About 10 years ago Roscoe bought a pair of flying lead autoformers from me and on Saturday he admitted he had yet to wire them up.  I had given a pair of modules to Gary to give away in the raffle and the winner said he wasn't a DIY kind of guy and returned it to the pool. (cool move)  On Sunday everything needed ot go and Gary stated you needed to be present to win.  When the autoformers hit his hand, Gary asked all the DIY'ers to raise their hand to get a pool of possible recipients and only Roscoe replied.... perfect!

I am still saddened by the lack of creativity showing up at these kind of events but my hope that future promoters catering to a wider audience was encouraged by this show. 

Monday, July 11, 2011

The Complex Curve on a Rectangular Horn...

I have had a lot of people ask about making their own midbass horn - PLEASE DO!!!

My method for a quick single or pair is to build rectangular. You can build a horn like this in a very long weekend if all the steps have been carefully planned...

but how to cut that complex curve that is the intersection of the curved wall and the straight wall??? extremely difficult to plot... and even if we can plot it, how many of us have a large CNC 3D router?

so I cut the straight side walls out of 3/4" plywood or even doubled up to 1.5", depending on panel width... I then screw in a brace that is right down the middle... this is easy to plot as it is just the center axis of the horn expansion... you can remove the brace later or keep it in if you want.. your choice..

when you drop a yardstick/meterstick across the face you will instantly see the complex curve... how will you ever get a piece of bending ply to fit properly on that uneven surface? simple. make it flat...

I do this with a "contraption"... that is southern for homebrew tooling... jig... doohickey-thingamajig... whatever... belt sander screwed and clamped to scrap wood... pictures tell it all...

brace in place:


I clamped and screwed the sander to a piece of wood:

The actual setup for sanding.. you want this horizontal as your arms will be tired:

check your progress with that meterstick:

not quite:

yep, got it:

close enough.. remember that on a midbass horn, a cm or inch of error is lost to the wavelengths in use... do not go crazy with trying to keep extreme accuracy... quality of build is much more important! stiffen... listen... damp lightly... brace... lacquer... love.. listen... that is how you make great midbass horns.. and do not be afraid to say "that sounds terrible" if it does.. that is only motivation to make it better...

adding layers in the next installment.... i tried to start and finish on Father's Day weekend... I lost... so maybe one late night this week...


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