Shavano Music Online

    Copying Cabinets

    3/99 - Jens Moller - http://www.colomar.com/Shavano/copy_cabinets.html

    If you are looking for a specific sound, and you are playing a guitar or bass guitar, you may want to imitate an established guitar/bass cabinet design. The reasons for this will not be obvious to some people, unless they are familiar with the design techniques employed to create these particular tonalities.

    First off, these equipment designers were not attempting to faithfully reproduce a recording - this was one of the furthest things from their minds. guitar/bass amplifiers are supposed to color the sound - this also holds true for the speaker systems. Instead, they were attempting to fill a specific need for a product that produced a desired sound quality. A Guitar or Bass depend on their pre-amp/power-amp and speaker system to color the sound in some pleasing way (often with a microphone set 1 foot away from the speaker to pump this tone into the PA system or a recording console).

    Secondly, the sizing factors used to create some of these classic guitar/bass cabinets were not based on complex formulas or extensive modeling and testing, they were often done by estimating how much space was required to house the particular speakers that were planned; a few samples were built to see how they worked and adjustments were made from there. Sometimes a variety of common speakers were used, occasionally special modifications were made to the speakers to deal with any sonic issues. The sonic qualities were measured by the builders using just their ears. The goal was to conform to a specific sound and feel, along with a business need to reduce waste material from the lumber used to build them. The frequency response of a guitar or bass cabinet is highly restricted and often can be fairly uneven; this relates to what it is being used for. Guitars don't put out many frequencies above 6,000 Hz, and those that are above 6,000 Hz tend to be harmonics, not the fundamental notes. These sonic restrictions, which are optimal for a guitar or bass, are usually sub-optimal for vocals, keyboards or recorded music playback.

    Lastly, some designs use open backed cabinets to allow the guitar player to toss their cables and any other stuff they needed in the back for simple transport. It also allowed any heat building up in the power amplifier to escape. Often a few tweaks were necessary by the designers to make the cabinet more stable, or to alter the tone a bit more effectively. Open backed cabinets are louder than closed back cabinets, but tend to have less low frequency response. Definitely not rocket science, but at the same time requiring a lot experience and knowledge of the end use. There are many open backed guitar cabinet designs available from just about every guitar amplifier/cabinet manufacturer. I doubt that you'll find any audiophile quality full range speaker systems made like this - I also doubt that you'll find many pro guitar or bass players touring with audiophile speaker systems connected to their guitar amplifiers on stage. Each has its own place and purpose.

    In general, these designs were often hit or miss. Over the years certain combinations of things resulted in desirable tonal quality. Other designs were dropped because they didn't sound right, and as a result didn't sell very well. This evolution produced cabinet designs that are frequently copied. This article gives the dimensions of some of the popular production cabinets that I was able to locate on various Web Pages or in local music shops. If you have some additional guitar or bass cabinet dimensions, please send them to me with some additional information, such as manufacturer of the cabinet and any information that you have on the speakers used. I'll compile information here.

    Keep in mind that the qualities of the amplifiers pre-amp and power-amp stages also color the tonality, in conjunction with the speaker cabinets. Most tube style guitar amplifiers sound their best when the output transformer is driven into saturation - causing a mild compression of the tone. This, in conjunction with the natural enhancement of the even harmonics caused by tube amplifier biasing and feed back loops cause a mild level of pleasing distortion in the pre-amp stage. There is also evidence that interal capacitance (tho a very small amount) in the transistor has a subtle, yet noticable effect - this capacitance is measurable in a transistor and doesn't exist in a tube. Even the voltage rectifier used can change the tonality - there are tube based rectifiers and solid state rectifiers available for some amplifiers - swap them and listen for yourself - the results sound different. This is why powered tube amplifiers often have a very warm and aggressive sound as compared to solid state amplifiers (which accent the odd harmonics, and tend to sound harsher). This is why tube guitar/bass amplifiers are still very much in demand. For the bass guitar, often a solid State power amp will give you a more accurate tonal effect, yet many bass players prefer the subtle effects of tube amplifiers.

    Tonality is a very personal thing - what sounds good to me may not be the tone you are attempting to capture. You'll know what you like when you hear it. To learn more about tone, speakers and how that information relates to Guitars, see: Weber Vintage Sound Technology.

    If you find some combination of guitar/bass, amplifier and speaker system appealing, take the time to find out more about it. Don't hesitate to copy it as closely as possible if you can't find a set up just like it. Also, consider mixing and matching to accentuate the sonic qualities you are seeking.

    Fender

    Sealed Back

    • What the Bandmaster/Bassman cabinets look like:

      Bandmaster configuration:
      Speakers: Two 12 inch.

      Bassman configuration:
      Speakers: One 15 inch.

      Speakers used could be any of:

      • Alnico Magnet Jensens
      • Ceramic Magnet Jensens
      • JBLs

      Cabinet Info:

      Dimensions:
      31 3/4 inches (80.6 cm) x 20 3/4 inches (52.7 cm) x 11 1/2 inches (29.2 cm)
      3/4 inch (18 mm) thick Pine Sides with Dovetail Joints
      3/4 inch (18 mm) thick Front Panel (Early ones were Plywood, later use medium density particle board)
      1/2 inch (13 mm) thick Rear Panel - Plywood

    Open Back

    • What the '59 Bassman looks like:

      Speakers used were: Alnico Magnet Jensens

      '59 Bassman configuration: 4 X 10 inch speakers

      3/4 inch thick Pine Sides with Dovetail Joints
      3/4 inch thick Front Panel

      Dimensions:
      22 3/8" (56.8 cm) X 23 1/2" (59.7 cm) X 10 1/2" (26.7 cm)

    Marshall

    Speakers used are typically 25 or 75 watt (G12-75) Celestions.

    Sealed Back

    • What this cabinet looks like:

      Marshall 4 X 12 Sloping front Stacking Cabinets:
      Overall Dimensions: 30 in (76 cm) X 30 in (76 cm) X 14.5 in (36.8 cm)
      The upper sloped portion (top) is 11.5 inches (29.2 cm) deep. The slope runs down 15 inches (38.1 cm) from the top of the cabinet.
      The material is 3/4 inch (18 mm) thick except where the the grill cloth is attached - this is 1 1/2 inches (43 mm) thick. The grill cloth is recessed approximately 1/2 inch (13 mm).

      Marshall 4 X 12 Stacking Cabinets:
      Dimensions:
      30 in (76 cm) X 30 in (76 cm) X 14.5 in (36.8 cm)

    • What the 1922 and 1936 look like (1922 shown):

      Marshall 1922
      Speakers: Two 12 inch (Wired as a Stereo Cabinet)
      Dimensions:
      26.4" (67.0 cm) X 20.5" (52.0 cm) X 9.84" (25.0 cm)

      Marshall 1936:
      Speakers: Two 12 inch
      Dimensions:
      29.5" (75.0 cm) X 23.5" (60.0 cm) X 12.24" (31.0 cm)

      Construction appears to be medium density particle board.

    Rivera

    Open Back
    • What these generally look like (R100-212A shown):

      R30-112 and R55-112

      Height: 18 inches (45.7 cm)
      Width: 20-7/8 inches (706 cm)
      Depth: 9-3/4 inches (24.7 cm)
      Cabinet material: Solid lumber-core plywood
      Cabinet thickness: 3/4 inch (18 mm)
      Baffleboard: 3/4 inch (18mm) - thick medium-density fiberboard
      Construction: Dadoed joints
      Speaker: One 12 inch specially designed Celestion
      Speaker impedance: 8 ohms

      R100-212A

      Height: 18 inches (45.7 cm)
      Width: 26-1/2 inches (67.3 cm)
      Depth: 9-3/4" (24.7 cm)
      Cabinet material: Solid lumber-core plywood
      Cabinet thickness: 3/4 inch (18 mm)
      Baffleboard: 3/4 inch (18 mm) - thick medium-density fiberboard
      Construction: Dadoed joints
      Speakers: Two 12 inch Celestion G12T-85
      Speaker impedance: 8 ohms

    Demeter SSC-1

    This is a special cabinet that allows you to play at very high volume levels and still hold normal conversations with those around you. How? Simple, its a sealed cabinet, with the speaker entirely inside and not ported in any way to the outside. The cabinet is split into 2 equal sections Its also filled with acoustic material in both sections. A Speaker is mounted in on the middle speaker support and there is a door that allows access to a microphone that can be adjusted and aimed as needed. The door is closed and the microphone hooks to your PA system or mixer. Play as loud as you want - it won't be that loud outside the box - careful that you don't fry the speaker - you won't be able to tell just how hard you are driving it. Perfect for recording wild guitar work without upsetting the people around you. You may still need to throw a few blankets over top of it to further reduce the volume level if recording with other instruments (to prevent picking it up in the mix).

    • What it looks like:

      3/4" marine-grade plywood is used for the handmade box
      The dimensions of the SCC-1 are 20 inches (50.8 cm) x 30 inches (76.2 cm) x 20 inches (50.8 cm)

      You pick your own speaker and microphone for your own specific sound.

    NOTE: All trademarked product names are owned by their respective companies and corporations. They have become industry standards by virtue of their high quality and identifiable sound.

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