User:Saul/guitar

Cab

- Beginners Building Guide - Celestion's Own Recommendations

Amp

My amp supports 8 & 16 ohm impedance and 100W or 50W output.

The amp should not be connected to speakers with less impedance than the output of the amp, it is better to have the impedance higher than the amp.

Wiring

• Speakers impedance should be matched.
• Parallel wiring of speakers halves the impedance.
• Series writing of speakers doubles the impedance.

Speakers

It is generally accepted that 16 ohm speakers sound a little better, Celestion has mentioned that they tried to engineer their 8 ohm V30 to sound like the 16 ohm V30.

I would like to use a mix of both the greenback and the V30 to provided a good range of sound.

• G12H30 Greenback heavy magnet 30W speaker (8 or 16 ohm)
• V30 Mesa Celestion Vintage 30 (8 or 16 ohm)

Wattage Calculation

Multiple speakers wattage is calculated as w = n * min(s.1, s.2... s.n) where w = total wattage, n = number of speakers, s.1 = speaker 1, s.n = speaker n

That is to say that the total wattage of the cabinet is rated at the number of speakers times the wattage value of the smallest speaker. This make intuitive sense since the the power is shared among the speakers and the smallest speaker can not handle and more than 1/n of the total power.

Examples:

• 60w, 30w = 60w
• 60w, 25w = 50w
• 60w, 60w = 120w
• 60w, 60w, 30w, 30w = 120w

Speaker failure

• Series w/ internal short: other speaker is driven at double power and might fail at high power.
• Series w/ wiring failure: other speaker will not be driven at all (no sound) and will be safe.
• Parallel: other speaker is driven at double power and might fail at high power.

Multiple Cabs

• https://support.bluguitar.com/en_US/amp1-mercury-edition/connecting-multiple-cabinets-to-the-amp1

Multiple cabs can be done with much of the same rules and failure issues as individual speakers. There are two options for connecting them regardless of series or parallel:

• Daisy chained (guitar into cab-1, cab-1 into cab-2...)
• Y-Cables (guitar cable splits into 2 and plugs into both cab-1 and cab-2)
  • Can come in series or parallel wiring.

Plan

• 2x cabs
  • Can run 1 with the 50W mode of amp.
  • Easy upgrade path.
• Y-cable (Series) wiring between cabs
  • Daisy chaining would be a bit of a pain here.
  • If one cab fails or the cable falls out the other will not produce sound and will not blow.
• Parallel wiring between cabs
  • This is the standard practice.
  • Makes daisy chaining easier.
  • If one cab fails/cable unplugs, other will run but might blow at high power.
• Each cab has 1xV30 & 1xG12H for good blend.
• Each cab will have 2 16 ohm speakers wired in parallel
  • If the GB fails the V30 should be safe.
  • If the V30 fails the GB could blow.
• Each cab will have 2 8 ohm speakers wired in series
  • If either speaker in the cab fails the other should be safe.
  • Impedance of the cab will be 16 Ohm meaning that 2 cabs will be 8 ohm.
  • Amp should be safe if one of the 2 cabs fails - impedance jumps from 8 Ohms to 16 Ohm which is safe.

Possible Features

• Switch between the V30, GB or both?
  • Impedance would go from 16 Ohm to 8 Ohm
    • This is NOT safe for the amp if the switch is bumped.
  • Power would be 60W for V30 or both but 30W if GB is set.
    • This is unsafe if the amp is turned up to much on the GB setting.
    • Maybe omit GB mode from the switch?
    • Does having one speaker turned off in a sealed system damage the other?

• Switch to change between series and parallel wiring?
  • What would the benefit be for me?

• Removable backplate?
  • Doesn't take much effort to add.
  • Not that useful in my usecase.

Physical Construction

• Does volume matter?
• Does depth matter?
• Does shape matter?
• Do Thiele matter?
  • No, apparently not for guitar frequencies. See https://celestion.com/blog/thinking-of-using-thiele-small-parameters-to-design-a-guitar-speaker-cab-think/