Turning two combos into a combo and ext cab

[Diablo]

The observant among you will have seen my various threads and comments about being lost in the mix, having funny burning smells from my Laney RB7 (300w, 2x10 kickback combo) and needing another solution. Volume + clarity = happy me.

I realised that the first thing I needed as a decent amp. Without that I was wasting my time with anything else. A trawl of the for sale section on here, a few PM's here and there and finally I did a deal with Kev for his PJB M500 head with 6x 5" piranha speakers. 700W at 2ohms and a very high quality cab on wheels seemed a good buy.

As standard that is a 12 ohm load so only ~200W output. The Laney RB7, although sold as a 300W is only actually an 8ohm load at 200W. For the full output you need an extension cab, but at full volume it smelt VERY hot pulling only the standard cab speakers so no way would that pull an extension cab and be happy.

So here I am with the PJB and the RB7. I need to get more air shifted, and get the PJB M500 onto more load. It seems crazy to buy an ext cab when I already have a 2x10 albeit currently a combo. So it was time to do some DIY cab mods and here is what I got up to.

First was to order a 2 pols speakon male-male cable and two 2 pole speakon female sockets from fleabay. My RB7 still works, just smells a lot when at high loads, so I did not want to bin it all. But it has no method of isolating the speakers from the amp. So I took it to bits, popped out the speakers and saw they are two 16ohm units in parallel giving the 8ohm total load. They use simple wiring and push on 3/16" connectors. It is therefore a very easy job to choose a place in the back of the cab to drill two holes and fit a speakon socket into each. One speakon is connected to the RB7 amp output wires, the other speakon was connected to the pair of speakers in the cab. Now by using the speakon external cable I can complete the link from the RB7 amp to the 2x10's, so in effect operates as it did.

BUT - I now I have a speakon cable that I can connect from the second output of the PJB M500 amp to the RB7 speakers, so in effect it gives a 2x10 8 ohm extension cab when connected in this way.

I ran this setup tonight at rehearsal, the PJB M500 amp, 6x5" pirhana speakers in the PJB cab, and the RB7 2x10 as an extension cab. Wow, what a difference. The 2x10's give really meaty bottom end, trouser flapping E and A strings, and the upper levels are taken care of by the piranhas. Sound quality of the laney speakers when run from the PJB are a different world to the RB7 amp. The RB7 amp would get very muddy and distort at moderate volumes, but drive the same speakers from the PJB and you get lovely clear sound as far as 7 out of 10 on vol, which was as far as I needed to go to drown everyone else out. I actually backed off the vol from there, it was just a test.

The mods cost me a total of £20 and half an hour of time. A very easy and cheap way of getting an extension cab that seems to really bring life, clarity and volume to the whole mix. The speakers in the RB7 actually seems pretty good for budget stuff but the amp is clearly no where near as good.

The advantage is that by taking both cabs to a gig I end up with a spare amp head that will run either speaker cab so redundancy on both sides if something goes belly up at a gig.

You will see the red/black wires as the orginal wires from the amp to the speakers, which I redirected to the speakon "out" socket. The purple and brown wires as the ones Iadded from the speakon "in" to the speakers. I fixed the two speakon sockets into a flat area at the back of the amp where they won't get bashed and are out of the way. I also marked the back so I know which is which!



Here should be some pics of the mods.


Cheers,
Rich

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[gjones]

Great stuff. I'm surprised that your new Phil Jones wasn't loud enough without using the Laney as an extension cab.

[Diablo]

With the 6x 5" the sixpak only puts out about 190W as it is a 12ohm speaker setup, so you need an extension cab to get the power up. Two guitarists each running 60-80W amps at full chat means 400W or more required on the bass, and not being into turning things up to max, it does make more sense to run more speakers and a lower vol on the amp. Either way, gig last night I had the sixpak and 2x10 extension cab sat on top with volume set on 6 out of 10 and I could hear myself nicely but without drowning anything else out. Must have sounded okay, the bassist from the pro band who followed us on stage came up to me afterwards and asked to buy my setup! "not for sale" says I.

Cheers,
Rich