Bottlehead Fix for Full Range Speakers

The Bottlehead Fix is a passive baffle step corrector and treble compensating device that sits between your source and your integrated amplifier, or between your pre-amp and amp. Baffle step correction (if the baffle is narrow) and treble compensation can benefit the sound of full range speakers in particular, so if you are into Fostex or MarkAudio drivers (or even Planet10 / Feastrex modified drivers), this is a great device to check out. Do note, in some cases, the compensation is already being handled by a network of capacitors, inductors and resistors within a full-range speaker.

There are four switches in total. As stated on the Bottlehead website: two of switches on the Fix controls the adjustable baffle step corrector that compensates for the bass roll-off in narrow baffled speakers. The first switch is used to set the bass turn-over frequency for the baffle width of the speaker you are using (selectable in inches). The second switch controls magnitude of the cutoff frequencies for passive bass compensation (which flattens a falling frequency response below baffle step frequency).

The third and forth switch compensate for treble roll-off with typical full range drivers. One switch selects turnover frequency, and the second switch chooses 0,2,or 4 dB of treble compensation above that frequency.

Curious if your speakers could benefit or not? The Fix is only $75 so it's not a big gamble, and given the popularity of full range speakers lately it wouldn't be a tough sell either. 

Normally, the Fix comes with a random colored piece of plexiglass (or similar material) and you either make the base yourself, or order one of Hammond or Bottlehead's for a few extra bucks. The build should be pretty quick as there aren't many parts, and would take the average person a couple of short nights to put together. 

Since I like everything on my rack to be "matchy matchy", I'll be using some alternative materials to put mine together, namely the typical copper leafed wood base and a copper plate. The copper plate I ordered was a remnant online, nice and heavy at 1/8" thick. I taped the plexi plate to the copper one and used it as a drilling template on the drill press. 

After drilling the holes, I sanded with 60, 180, 300 and 600 grade sandpaper, then spray painted it with a matte clearcoat from Krylon, otherwise it would be oxidized with hand-prints the very next day. 

Drilled copper plate

The base is made from 2 inch tall decorative molding from the local hardware store, cut with a miter saw, adhered with wood glue, and braced in the corners with square pieces of pine. It's then copper leafed using generic copper leaf and Mona Lisa Speedball base coat, adhesive size, sealer and antiquing glaze. These items can be found at your local Michaels craft store or online. 

Sitting in a copper leaf base

The first step in assembling the Fix is fastening on the switches and RCA female connectors. A socket wrench is especially handy in this step, however if using the plexi base, caution is advised in the manual as it can crack. In addition, the switches have plastic threading, so they could strip easily if too much pressure is used. 

Switches mounted

Once these items are secure, it's then time to mount the solder tabs. The manual shows corresponding letters and numbers for each solder point, so it's great to write these directly on the plate for ease of assembly. 

Labeling the solder points

I ran a solid piece of Cardas magnet wire for the ground plane and tied any solder tabs that needed to be grounded to it using bus wire. The polystyrene caps supplied are very nice quality. Polystyrene was commonly used for capacitors in the 50s up through the late 70s. You'll still find them today, many of them surplus from overseas. In vintage tube amps you may find them in glass-sealed tubes. This variety has the leads laid-in, and you need to be careful in higher values as they will create inductance based on the way they are built. Also polystyrene caps can melt, so don't put them in areas of high temperature! Those are the cons, but many feel that polystyrene caps are second only to Teflon in sound quality, so it may be worth it to experiment with them.

The 15,000pF caps in the Bottlehead kit are polypropylene, I opted to order some polystyrene to match the rest of the build. These came from Israel and are a little larger as they are 125V (no particular reason, just the smallest value I could find).

I opted to use some Cardas hookup wire and carbon film resistors for the build, just based on my own preferences. The ethernet wire that Bottlehead supplies is extremely high quality, so go with that unless you are a die-hard Cardas fan ;)

Bottlehead Fix interior

With the 15000pF caps installed

Bottlehead supplies a nice piece of black vinyl that has the functions printed on it, as well as an "I" and "O" for input and output. As a final touch, I added the iconic Bottlehead badge to the lower center.   

The completed Bottlehead Fix

I hope you enjoyed this post. Please visit Zynsonix if you need some sweet sounding interconnects for your Bottlehead gear, or any other custom audio cable. Until next time! 

The Fine Print:

The above steps detailing the build of a Bottlehead Fix are for entertainment purposes only, and not intended to be used as assembly instructions. Zynsonix Audio LLC is in no way affiliated with Bottlehead. The owner of this blog and all associated parties can not / will not be held responsible if you attempt the process posted and cause physical harm to yourself, your surroundings or your property. 

Steampunk Art & Design

I wouldn't necessarily call all of my electronics work my own creations; many of the amps and preamps were existing circuits or kits that I may have modified the parts list or made a few minor circuit changes. As enjoyable as it is to build them, it's preferable for me to stick with tried and true circuits created by the experts and not come up with new schematics of my own volition. There tends to be more enjoyment in the final presentation, the color scheme and the chassis work and even the way the inside looks. A number of people have told me that my builds have a Steampunk look to them. I'm familiar with the movement, and I wasn't even aware of the fact that my design choices tend to follow that look, but perhaps was subconsciously making the design decisions with Steampunk as an inspiration.

Steampunk?

I suppose my designers manifesto is that I feel that amplifiers with older technology like vacuum tubes should have a vintage look and patina, even if they are being assembled in the 21st century. Vintage has a different look for different people, but I tend to think of copper and polished brass, gold plating, brown and copper hues with a crinkled / hammered texture, wood and metal grating and leather. These seem to be the same facets that find themselves in the psuedo-Victorian era Steampunk movement of design. I'm not sure that future projects will have the telltale brass gears and non-functional pipes that Steampunk gear tends to have, but I may think up other embellishments as time goes on.

I think that the main inspiration for vintage electronics was a company called Moth Audio that produced a number of designs from 1996 to 2007. There are many purveyors of audio gear that make really beautiful work, but in my minds eye, the aesthetics of Moth Audio gear is second to none. Craig Uthus was the head of Moth and at the time, the work was considered to be "retro-styled", the designs were highly distinctive and still highly sought after today. Craig's partner at Moth was Joel Marshall, a Hollywood prop designer, who designed the beautiful chassis you'll see below. 

Moth Audio NiteLite with 15E Radar Tube

Moth Audio Sphinx balanced line-out amp and phono preamp

I almost feel that these amplifiers belong in an exhibit somewhere. Perhaps someone out there could open up an audiophile museum one day, the cable section alone could take up a whole wing ;)

There is at least a few audio builders out there that fully embrace the Steampunk aesthetic; Aevil at Coppersteam Labs put together the best looking S-5 Electronics K-12G I've ever seen. I'd imagine there's more money invested in the copper than the amp itself, it's a real beauty that looks like it came right out of Bioshock.

AEvilMike's K-12G Amplifier 

I also found a lovely "effect-pedal" if you will made by Peter Groenewoud at Hilltree Productions called the Steampunk Doomsday Machine. The top features two 230V DC bulbs that carry the music signal and create the effect. Lots of wood, brass and copper in this Steampunk design. Peter will not share a schematic on this device as the 230V DC going across those lightbulbs is fairly dangerous.

Hilltree Productions Steampunk Doomsday Machine

Also, a new addition after the 2012 Bay Area HeadFi Meet was Frank Cooters amazing looking headphone amplifier. I don't know too many details about this one, but the glorious copper piping and top-plate and nicely figured hardwood really set this apart from other builds. Evidently all the work inside this beast is point-to-point, and Frank has a matching one that powers electrostats. In this photo it looks like someone has an Audeze LCD-2 headphone plugged in.

Frank Cooter's steampunk-styled headphone amp

In conclusion, I'm not sure that my builds are Steampunk. They may look like it to a certain degree, but it's nebulous where the line of vintage and Steampunk merge, intersect and share common facets. What do you think?

Looking for some steampunk-esq audio cables and equipment? Contact your friends at Zynsonix Audio.