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Wednesday, September 30, 2009

Second Part - Marshall 1960B 4x12" cabinet modified with X-pattern speakers combination

Disconnect all the cables which are connected between four G12T-75 speakers.

Remove two speakers of them. Bear in mind to keep these screws and washers carefuly. You need to use them later.

Finally became like this.

Stock Celestion G12T-75 and Vintage 30 speakers.
Which one is the Vintage 30 ? Ans : Left one.

Here is the picture of Bogner Uberschall 4x12" cabinet(from Bogner Amp Forum)

Even though this modification which is using the same speakers combination from Bogner Uberschall cabinet,
but you won't get the exactly Bogner cabinet tone from Marshall cabinet.
It is because the cabinet structure, size and material are also the major parts which affect cabinet sound character.

Two types of "X-pattern" wiring -
Series-Parallel "X pattern" wiring diagram

Parallel-Series "X pattern" wiring diagram

I followed the Series-Parallel "X pattern" wiring diagram.
Attention !
Reconnect all the speaker cables. Red speaker cable connects to "+" terminal of the speaker and
Black speaker cable connects to "-" terminal of the speaker.

Put back the back panel of the cabinet.
Reconnect the speaker cables onto the jack plate.

Congratulation ! Mission completed !
Marshall 1960 Lead cabinet - X pattern speakers combination modification

=Mono Mode=
Left input jack (Total impedance : 4 ohm) became "Parallel-Parallel X-pattern wiring"
Right input jack (Tota impedance : 16 ohm) became "Series-Parallel X-pattern wiring"

=Stereo Mode=
Left side input jack (Total impedance : 8 ohm) became TWO Vintage 30 speakers wired together in "Diagonal" position.
Right side input jack (Total impedance : 8 ohm) became TWO stock G12T-75 speakers wired together in "Diagonal" position.

You will need to break-in the new speakers.
Suggestion from Celestion website :
Or using "Variac" to break-in.

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