I realized when looking at these photos that a 304th as size reference just doesn't do these horns justice. They are massive... and beautiful... Construction is also superb. His new guy obviously knows wood...
So the first round is finally here. We held off on sending the second shipment until we finished a trial run... and I am glad we did. We will use the same company, but the routing was, well, illogical... we will correct that this time...
Got the field coil Alpair 12's finished late Friday night and Saturday was dedicated to getting them mounted in a pair of Bob Spence's enclosures designed by Johan van Zyl. It was Bob who originally contacted me about this project and he introduced me to Mark Fenlon. JJ hauled these cabinets up to me last July and we barely had enough time to compare the Neo, alnico, and field coil 5" lowthers. I lived with the field coil 5" units for about three months and the alnico ones ever since. Here is what the cabinets looked like before the "swap" started.
OK I'll be the first to admit it was a hack job, but the hole was 6" so it needed to be sized down for the 5" driver. The Alpair 12 required a 6.5" hole and while I was at it I decided to open it up to 7.5" so I can also mount an 8" lowther. I did a marginally better job with the new adapter plates but when it comes down to it, time is more important to me than looks so they were MDF lightly sanded and painted with 1/4 a rattle can of black gloss paint. (I was not running out to get another can)
I typically would take the copper of the motors dark, but for this I liked the feel of the copper motor and the copper colored cone so I just worked the finish slightly to give a bit of feel to it and moved on.
By about 5PM I had one driver mounted and playing and I started working on the other cabinet. It would have been about 4pm but I decided to try out Gorilla Glue to hold the motor support in place instead of 5 minute Epoxy and I didn't realize the 1 hour clamp time.
Driver upright and playing and the other was in place about an hour after. Of course the $64K question is how is the sound and I'll have to take a pass on that for the moment for three reasons. First, these basket structures need to be treated gently during the first 20 hours of play and then gradually ramped up during the next 80 or so hours. Apparently hitting them hard out of the box leads to interesting deformations of the cones. Mark's "break -in" instructions found here If not followed,
The second reason I cannot comment on the sound even though I am past the 20 hour mark is I need to swap in some bigger tubes. I suspect some severe 2nd order distortion (clipping) will not help the cause and since 2A3's barely cut it with the lowthers so I'm going to need to swap in 75TL's or triode wired 4-65's at some point next week.
The final reason I cannot comment on the sound is because I am using iTunes through a crappy DAC. There is no way I'll ever get these things broken in attempting to cue up vinyl 24/7.
I did stay up late last night and played with a variac on my lap adjusting the field strength while listening. I was shocked even at low levels how much the tone could be changed by twiddling the knob. It reminded me of how when Bob was here with the permanent magnet Alpair 12's how we had to adjust the position to tune the corner loading except I was doing it with current through the field coil rather than placement of the speaker with relation to the room corners. I'll update things in a week or so after I get 100 hours of random digital into it and let you know how things are going.
During a recent plating episode I became fairly bored watching the copper grow and I started having some fun. The results were astonishing! I want to introduce you to the newest product from the Emia Mint.
The copper quarter was the result of the combination of mindless hours of watching copper grow and beer. At some point during the process, one of the spectators asked the benign question "where does the copper come from?" This seemingly simple question brought forth the second product from the Emia Mint and that is the Copper Quarter / Silver Penny tandem. To our knowledge, the picture below represents the first know case of all of the copper form a penny being electrically removed and deposited on a quarter.
For a limited time The Emia Mint will perform this miracle of nature for free. (plus a small processing fee of $72.26) For an additional $50 surcharge we can actually preform this process on coins you supply and offer a generous 26 cent discount for coins supplied with sentimental value.
Enough fun... The coins above are indeed what I say but in the interest of full disclosure (and to keep my friend Roy happy) I am forced to publish the never seen before images of the above coins before a slight amount of treatment with some #0000 steel wool to polish them up.
First of all, I am not a “Guest” blogger. I told Jeffrey that I was compelled to write about his latest creation, and his response was, “Great! You’ll be our first guest blogger.” It’s sort of like the obnoxious people at the insurance company who refuse to list me as the insured person on the health insurance policy even though I am the one who pays the bills and the one who signed us up in the first place… sexism, pure and simple! He may build the amplifiers and speakers, but who has to live with them all while they are in development? Who has had sawhorses in her living and or dining room for nearly two years now while we “finish” the speaker design? The “Guest” blogger… that’s who! So… last night, I walked out into my garage to ask my husband a question, and here is what I saw:
I know!!! Any normal person would wonder what in heaven’s name that Unabomber look-alike was cooking up in my garage. Sadly, I don’t have to wonder. You see my husband has a sincere devotion to practicality that combined with a lack of concern for public opinion results in little “fixes” like this one. Jeffrey sees a need to be able to talk to Dave while he is out working, but doesn’t want to be restricted by having to stay near the phone, so he straps himself up with packing tape, and … voila… he has solved the problem without any notion that he looks like he’s headed into a crowded street in Fallujah. This is totally characteristic of the man that I love… The last time we were flying to New York, Jeffrey had a few items that he wanted to take to Dave. Now, any normal person might recognize that a bag full of unidentifiable mechanical/electronic equipment might not be the thing that you want to be carrying onto your plane in the current climate… especially when we were at Code Level Orange…
but my husband is not any normal person. No, Jeffrey, who has probably not looked into a mirror in at least 10 years, thinks that carrying this stuff onto the plane is the only way to ensure that it will safely reach his darling Dave, and so off we go… I try in vain to explain to him that perhaps if he were willing to shave, he might be a little more likely to avoid the full-body cavity search, but he won’t hear a word. So we get to the airport and, by this time, I am glistening all over (Southern women don’t sweat) because I know what’s coming. I’m absolutely positive that my husband is going to become a “person of interest” in some underground prison somewhere… but I’ll be darned if he doesn’t manage to sweep right through security and on to the plane without a single problem! Seriously!!! Would you want this man on your plane with a bag full of wired equipment?
In honor of Papa Joe's "Meet the Tube" series from Sound Practices, (You *ALL* have a copy of this, correct?) I would like to offer up "From the Stash."
I have mentioned our Stash tube today quite a few times over the years, yet I have not seen anyone using it. Maybe it is just too rare, but I think it is more that people just don't recognize it.
So what is this tube? Well, it is an indirectly heated triode. Rarely will you see me write about an indirectly heated tube, but this one is nice... maybe my favorite indirectly heated tube. The gain, at about 13, is high for an ancient tube (1920's), but it is certainly not high by even 1940's standards. The plate resistance is low enough to load with a nice nickel plate choke or even a nickel bifilar 1:1 interstage transformer. For full specs and plate curves, just use the 56 numbers as they nearly overlap. I really consider this tube a 3V type 56.
To the best of my knowledge, the tube was made by Sparton, Cardon, Tung-Sol, and Sylvania. I have only seen the old globes from Sparton/Cardon. I think that Tung-Sol and Sylvania just made them as replacements for Sparton sets after they went under. The early versions are also seen under the number 484, and often have a longer plate.
The catch, if there is one, is that they are often used pulls that are worn out. I have about a one in three or four success rate with them. So even though they are dirt cheap, you do need to be prepared to stalk eBay for a year or so to gather up the six or eight to build an amp around them.
So where to use a tube with some gain, but not much? Well, I have used it as phono stage output, just don't strap a fifty foot interconnect to it. I have also used it as a driver with high mu output tubes like the 304tl, which itself has a gain of 12. But I think the best application for this tube is in the input slot of a three stage amplifier. I rarely build three stage amps, but if you have a speaker that is not 110dB horns, you may need that third stage of gain. It allows for a really beefy driver for that transmitting tube output stage, and makes up the gain difference of the speakers.
So, as is always the rule with rare and precious things, no hoarding, but please buy and try.. these make music...
So it appears that over Spring Break Dave made progress. Lisa will say that I also made huge progress, but it doesn't feel like it yet. I spent at least a few hours each day rearranging the shop. It had been growing out of control for years. Not controlled growth; it looked like the street map of downtown Boston. So it was time...
Now my racks are all along the side walls and the back wall. I have a huge "U" shaped work area. Four large solder/construction/measurement/work areas. This will lead to progress.
The front wall is being reserved for HiFi gear. As such, I have just been stacking some of the extra "stuff" along this wall. It is now out of hand again. I will have to do some serious arranging of this mess... listen to parts of it... learn what is doing which parts well... then rework.. fix.. arrange.. maybe even attic or junk some of it... I would put good money on a four way horn system very soon... but here it is now:
At this point, I was soothed... no, motivated, by this photo of Jucifer.... the thought of the Dead's "Wall of Sound"... maybe I should just hook all this stuff up and have a raging Spring... Tool, Dead Kenny G's, Motorhead, Biscuits... even Mahler would love this much moving air...
So until the next shop photo in which everything is arranged perfectly and I can float a tonally perfect Coltrane out in front of my workbench, I will enjoy this new monster... the horn rig inside is still prim and proper..
I finally have some hard flux measurements on a filed coil project we have been working on. The request was for a field coil version of an existing commercial driver and the first step in the process was to tear apart an existing unit to get the needed measurements for an apples to apples comparison. Somehow I get great pleasure from tearing things apart to see how they work. You never know what surprises you might find.
I just love that wire and as you can see the cone has been removed from this driver to allow me access to the gap. The big surprise came when I would place the cone on a flat surface and how it acted like a suction cup and would not let go. The surround is so soft and pliable that it creates such a suction that it must be slid of the edge to remove it. It will slide freely across a flat surface but the minute you try to pull upward it grabs on and will not let go. I actually put this to good use when I had to replace the hard drive in my imac. The plexi screen protector is held in place with magnets and to remove it you are instructed to use rubber suction cups to pull. Having the Alpair 10 basket handy a quick pull liberated the plex and I was free to proceed with the drive replacement. I know the verbal account doesn't really illustrate how cool this "basket as suction cup" really is so here is a picture to show my faith in the strength of the bond.
Enough with the destruction and onto some production. I guess this means that the cat is officially out of the bag so it is safe to say we are working with Mark Fenlon to come up with an affordable field coil. The projected debut of the prototype driver will be at the Lone Star Audio Fest in a few weeks.
At the fear of becoming overly technical, I will close with the plots of the gap flux density of the motor in question both measured and simmed. The target flux is about 1.3T and things are looking good.
I spent much of the day playing with measurements and chasing ugly things. Since it kills me to pull down the system to go to the bench to make measurements, I simply take the lazy approach and bring the measurements to the system. This way while I am contemplating the meaning of life, I can have music to help me think.
The ugly part comes in when you look at the mess of wires I create when attempting this task.
OK, I'll admit that isn't really that bad compared to my earlier works so I guess that means I am growing as an individual. The goal for the day was to chase down some noise, compare the output and frequency response of a few cartridges and try to peer inside a sealed up Tannoy crossover.
The Good part is that all of the above has been made reasonably easy and affordable with the slew of audio measurement software and hardware out there. I'll be the first to admit, I do not have Audio Precision quality or even Tek bandwidth but my humble measurement suite gets me the information I need.
The most important thing to me is to be able to capture and save the data. I have a data capture device that samples at 1mhz. It has the ability to oversample to give (according to nyquest) 5mhz bandwidth which gives an acceptable live look at a 10K square wave. It also has FFT capability as well as the ability to measure various aspects of the waveform. The trace on the above picture is actual music and is something you will not ever see on anything other than a storage scope. This is really important to me since I feel much of what we are looking for has to do with dynamics and to me, using a 100mhz scope to view a static signal is like watching paint dry.
This is the little beast that does it all. It comes from usb-instruments and costs about $200. I find the datalogger function really helpful and they even have a higher sampling rate unit that only has a single channel for about the same price. I guess you need to pick your battles first, then choose your tools.
In reading back I have covered the Good and the Ugly, In order to make this post complete, I will leave you with the bad.... and when I say BAD, I mean sorta kinda really mis-behavin'
All these posts on tubes and iron and horns... but not even *one* on drivers!
The first driver post should be a post on either the WE555 or the big Fletcher compression driver, but they take time as they deserve a proper post... and I need to go solder.. so here is something few people have seen.. Goto guts...
and lastly... what happens at my house when you leave a driver on the kitchen table.. (yes, I had taped over the gap)..
nope.. actually not... Mr. McFeely would be faster than customs.. horns flagged for x-ray inspection??!!
but it has made me think about delivering.... crating.. shipping.. but how cool would it be to have an old school delivery truck? So here's me in my truck.. delivering tubes and horns around the neighborhood... (this picture looks so much like me that it weirds Lisa out.. no photoshopping at all)... and check out the sweet phone number.
That leads to this unbelievable ride. It has been Spring Break for the kids all week. I was taking them (and I cannot lie, I love to skate, so me as well) to the skatepark. We passed this cool car shop... and right out front they have the coolest Divco I have ever seen... I braked, swerved, and managed not to crash...
The pink just makes it straight out of Dr. Seuss. I love how the windows arc *out* as they rise from the hood to the roofline. I know of no other car that does that. I am not sure my daughter would ever talk to me again if I actually tried to pick her up from school in this, but man it would be awesome to load it up with gear and go cross country cruising...
"TVC's" are all the rage. (We have already discussed how Inductive Volume Control is the proper term as it covers transformers and autoformers.) So who invented this new ingenious device? S&B? Sowter? Thorsten? nahhh... it was our own Slagle, right? No way! But certainly it was invented in the last decade or so....
Oh, no... not this radio, again... yep, this radio, again.. Of the dozen or so patents on the (brass) badge, the most recent is 1921. So, not a recent invention. But why did it disappear for eighty years? As is typically the case, probably simply due to cost. I admire dave for keeping his autoformer volume control costs down, but they are still an order of magnitude greater than that of a simple resistive potentiometer.
But I honestly do not know the modern history. Dave, we both preach about credit where it is due, so who resurrected this idea?
(Dave chiming in here)
My introduction to the inductive volume control came from the pages of Sound Practices and the Ads for the Silver Rock. My interest in the idea was started in the late 90's by Thomas Mayer's praise of an "Autoformer Silver Rock" he had Serge wind for him. With that inspiration, I tried a pair of 2A variacs as volume controls and as wrong as it seems, there was some magic. The discussions on the topic were going back and fourth on the Joenet and it was at this time that I decided to strip some little nickel Lineouts I had and give it a go. Around the same time people were commissioning Sowter to do the same. A short time after that S&B got into the game and then a number of others showed up.
Aside from the Western, Luxman made an inductive control in the 80's and there have also been reports of a few German schematics using inductive attenuation. About 5 years ago I met Serge at RMAF and took the opportunity to thank him for the inspiration and apologize for "stealing" his idea mentioning that I could not afford his product. He simply replied his entry into this area was when he was in college and couldn't afford the Luxman so he wound his own.
I don't think the important thing here is who invented something or who did what first. What is important is paying respect to the people who help you generate your direction.
(Dave chiming out and feelin' kinda blue :-)
An update for 2K14. Stefano tracked down the Luxman unit.