DIY Series Box

[HRobert]

Here's a picture of the series box that I built so I can run two 4 Ohm cabs with my 67 Sentura II.  Since the Sentura II amp has a minimum load of 4 Ohms, I have to use this to put the two 4 Ohm cabs in series to get an 8 Ohm load. Otherwise I would get a 2 Ohm load and damage the amp.  

The box puts two like-load cabs in series - like wiring two speaker in series - and doubles the load. Here's how the box is set up.  There are three 1/4" female jacks;  The "AMP-IN" jack - which receives the output signal from the amp, and two Speaker Jacks - "A & B".  Please refer to the picture for the wiring.  The red wire goes from the TIP of the AMP-IN Jack to the TIP of Speaker Jack "A".  The green wire goes from the GROUND of Speaker Jack "A" to the TIP of Speaker Jack "B".  The black wire goes from the GROUND of Speaker Jack "B" to the GROUND of the AMP-IN Jack...thus completing the series circuit. The AMP-IN jack is mounted open frame down, and the two speaker jacks, A & B, mounted open frame up....that way there is no crossing of the connecting wires as the necessary connections are adjacent to each other.

The project box is from Parts-Express.com and is part #320-704.  It comes with a cover with 4 screws and costs $5.33.  The open frame 1/4" female jacks were about $.75 each, and the wire was about a dollar.  An easy and inexpensive solution for a speaker load problem.

[chev]

cool, that's just useful! nice job.

[JonO)))]

What a great idea!

I recently began building a couple of 112s to compliment my T50C and, having no knowledge or understanding of electronics, I had intended to create a thread to ask about this aspect of wiring...

Since the T50C can accomodate 3 additional 112s, I will have to parallel wire each of my cabs in order to run them together in series. I have spoken to a couple of people about how to do this, however if there is an electronics guru here who can draw a simple diagram for me I will be extremely grateful!

Cheers
Jon.

[HRobert]

First, you need to know the load rating for the speaker in you amp...is it 8 ohms or 16 Ohms.  Second, you need to know the minimum load that your amp will safely take; 4 Ohms or 2 Ohms.  Once You have that information someone on the site can advise you of the speakers you need and the best way to wire those speakers. Ex; If your amp has an onboard 8 Ohm speaker, and your amp has a minimum load rating of 2 ohms, you would use 3 more 8 Ohm speakers in seperate cabs.  The cabs then would have two input jacks wired in parellel so they could be stacked, or patched together. Four 8 Ohm speakers wired in parellel will give you a 2 Ohm load.

[JonO)))]

Thanks for your reply!

Each speaker will be 16 Ohms, and the total impedance with 2 additional speakers is 4 Ohms. The manual says that the T50C can handle 3 extension cabs in total, each rated 16 Ohms for a total impedance of 4 Ohms!

I'm not going to deviate from the design I am copying, therefore I will be using the Celestion G12T 75s.

[HRobert]

Thanks for your reply!

Each speaker will be 16 Ohms, and the total impedance with 2 additional speakers is 4 Ohms. The manual says that the T50C can handle 3 extension cabs in total, each rated 16 Ohms for a total impedance of 4 Ohms!

I'm not going to deviate from the design I am copying, therefore I will be using the Celestion G12T 75s.

 

Regardless of which brand of speaker you choose to use, they have to be all of the same impedence-16 Ohms, and the speakers cabs have to be wired so when they are patched together they are in parellel.

[JonO)))]

I think I may have been confusing terms (parallel vs. series)... Thanks for clearing things up for me!

I intend to follow the instructions in this youtube video regarding concerning parallel wiring: http://www.youtube.com/watch?v=y_HVgxUAVIU

[HRobert]

I think I may have been confusing terms (parallel vs. series)... Thanks for clearing things up for me!

I intend to follow the instructions in this youtube video regarding concerning parallel wiring: http://www.youtube.com/watch?v=y_HVgxUAVIU

Hopefully the information was usefull.  If you have any question about Sunn amps, you can probably find any answer on this site.  I watched the video on how to do parellel wiring.  It was very good.  I  do it differently...I run both of the speaker wires leads to the first input jack and then run a short pair of jumpers from the first jack to the second jack.  Both work equally well.

[Walt-Dogg]

With the intention of building one of these for my rig, for the life of me I can not get the search to work for the part on Parts Express, anyone got a direct link?

[HRobert]

With the intention of building one of these for my rig, for the life of me I can not get the search to work for the part on Parts Express, anyone got a direct link?

Try this http://www.parts-express.com/home.cfm?utm_source=google&utm_medium=cpc&utm_campaign=G+-+Brand+-+Main&utm_group=G+-+Brand+-+Main+-+Exact&utm_term=parts%20express&9gtype=search&9gkw=parts%20express&9gad=6888169393.1 It will take you the the PE home page. Use the search box in the upper right of the Parts-express home page and type in the part number. The box is part #320-704.  The rest is just regular 1/4" female jacks and some 16 or 18 gauge wire.  If you have any questions, ask.
Rob

[CLD]

You can find all the parts there. I did ... just haven't put it all together yet!

[buzzsunn]

Nice one HRobert. But I have a question... What kind of cable did you use for this box?? From the pic it seems that is simple cables (the one we use for building pedals for example). Since we are talking about speakers and ohm load I think you need "speaker cable". Be careful with that because the load is VERY different. Eg you don't use guitar cable to connect your amp with your cab  .

[HRobert]

Nice one HRobert. But I have a question... What kind of cable did you use for this box?? From the pic it seems that is simple cables (the one we use for building pedals for example). Since we are talking about speakers and ohm load I think you need "speaker cable". Be careful with that because the load is VERY different. Eg you don't use guitar cable to connect your amp with your cab  .

It's not shielded instrument cable - if that's what you're refering to. The wire is 16 gauge multi strand, same wire that would be used in speaker patch cables and shorter PA cables ( 30' or less).  I untwisted the wire and counted 18 strands.

[Walt-Dogg]

Finally ordered the box to get this project rolling now that I've bought extra speaker cables to connect the box to my amp and my cab to the box. Jacks and wire will be purchased tomorrow at RadioShack. Pressured to get this done in time for a gig on Jan. 8th, I only have my Studio Lead with me and I'll be borrowing a 4x12 to get more perceived volume with more speakers.