Dummy Load Products/8/16 ohm Head With Two 8 ohm Cabinents

J

Jeff5

New member
Hey guys.

I have an H&K Tubemeister 18 that I run with a Mesa mini-recto cabinet. I want to add another mini-recto cab for a mini stack (I found a good deal too) but I'm worried about the ohm ratings. The H&K is 8 or 16 ohms. If I hook up the two mesa minis (they are both 8, wired in parallel) it will be a 4 ohm load.

I know opinions vary about whether it is safe or not to do this (run a 4ohm load on an 8 ohm head), but I would rather not take the chance. Are there any relatively cheap dummy load or other product options that I can buy that can add the load I need? Any recommendations would be appreciated. Thanks!

Jeff
 
Re: Dummy Load Products/8/16 ohm Head With Two 8 ohm Cabinents

Easy. Make a series/parallel cable or box. A 3-ended device, or 3 sockets in a box, or on a panel in the back of one of your cabs. One connects to the speaker output socket on your amp. You plug your two cabs into the other two sockets, which are wired in such a way as to put the two cabs in series, which in your case would give you a safe 16 Ohms total load for the amp.

Obviously one of the sockets is dedicated to plugging in to the speaker output of your amp. The other two both have to have a cab connected, otherwise the series circuit is not complete. In other words, when you want to use one cab, you don't use this box/ cable, it is only used when you want to put two cabs in series.

It works great, i've done it many times, I mostly use a Y cable i made that has a plug to go into the amp's speaker socket, and two line sockets that each accept a speaker cable to go to the cabs. You could even build it into one of the cabs with a switch to select series or parallel operation.

Many options in how you create it, but always the same simple principle and construction.
 
Re: Dummy Load Products/8/16 ohm Head With Two 8 ohm Cabinents

Thanks guys! I definitely want to match the impedance, don't want to damage my amp.

Crusty, do you have any links or resources on how to make the cables? I'm fairly good at soldering, etc., so it shouldn't be that hard for me
 
Re: Dummy Load Products/8/16 ohm Head With Two 8 ohm Cabinents

Just a little bump. Does anyone have a resource on how to make a series/parallel cable? Thanks!

Jeff
 
Re: Dummy Load Products/8/16 ohm Head With Two 8 ohm Cabinents

u ll need somethin created like this;
impedance.png

all u need is 3 T-S sockets, and power wire. make note of how the tip/sleeve connections are made, or else u will end up with out-of-phase cabinets. couldnt get hold of anythin on web, so please wait for confirmation anyway. i m still not sure what is the parallel part here.

and DO NOT run this setup without both cabinets connected, or else the amp with be without load, bad news for OT :-(
 
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Re: Dummy Load Products/8/16 ohm Head With Two 8 ohm Cabinents

koshikas said:
u ll need somethin created like this;
View attachment 56164

all u need is 3 T-S sockets, and power wire. make note of how the tip/sleeve connections are made, or else u will end up with out-of-phase cabinets. couldnt get hold of anythin on web, so please wait for confirmation anyway. i m still not sure what is the parallel part here.

and DO NOT run this setup without both cabinets connected, or else the amp with be without load, bad news for OT :-(
Click to expand...

^ Yup, that diagram on the right is what I'm talking about (I inadvertantly called it a series/parallel arrangement in my previous post ... forget the 'parallel' bit, this is a device to put cabs in series, and as koshikas points out, it should only be used with two cabs connected to the two cab sockets.

That arrangement can be wired in many configurations using plugs, sockets or combinations of both to make a 3-ended cable or a box with sockets, but the electronic configuration is always the same. Depending on the configuration you opt to build, you may need one or two extra speaker cables.

If you wanted to actually build this arrangement into one of your cabs, you could add a switch to enable/ disable it, but i'd have to draw it up by hand and scan it to be able to post it. You only need basic soldering skills and a little care to make a version of a series cable/box/unit, and obviously the cost is minimal. If you need any more help, just ask here, but the principle is pretty basic, just looking at that diagram should make it evident as to what happens when the speakers are connected (and obviously you connect the device between the cabs and the amp before switching the amp on). When you only want to use one cabinet, you don't use this device, it's only used when you want to put two cabs in series.
 
Re: Dummy Load Products/8/16 ohm Head With Two 8 ohm Cabinents

Jeff5 said:
Also, while I still may make this myself, can I basically use any TS Y speaker cable? Such as this?

http://www.showmecables.com/product...1pS8k4o31C_AZ7EcPXa_bA8fJaOUJD4cizxoCN0bw_wcB
Click to expand...

Absolutely NOT. That is audio signal cable, which uses shielded cable, which is a big 'no-no' for speakers. I don't remember ever seeing a commercially-available series speaker connecting device (they may exist somewhere in some dark, dusty corner of the internet but i've yet to stumble accross them). Not to mention the possibility of the TRS (stereo) plugs possibly causing problems on some types of socket.

That's why the conventional wisdom (if there is such a thing on this topic) is to make your own. All you need is some standard 1/4" sockets or plugs, or both (depending on whether you plan to make a 3-ended cable, or a small junction box or panel) and some simple, reasonably heavy-duty speaker wire. And as i mentioned previously, you may need an extra speaker cable of two (so just a few more 1/4" plugs and a bit more speaker wire).

If you want, I could build you one and send it to you. It would be good if you could pay the postage (I'm in Australia), but if not, the postage should be reasonably cheap so i'd send it anyway at my own expense. I've been doing this kind of stuff for 40 years, so it's not a major problem. You'd just need to PM your name and address to me.
 
Re: Dummy Load Products/8/16 ohm Head With Two 8 ohm Cabinents

Crusty that would be great! PM sent. Thanks a ton!
 
Re: Dummy Load Products/8/16 ohm Head With Two 8 ohm Cabinents

No worries, we can make this happen. I'll probably have the device built sometime in the next few hours. I've sent you a PM.
 
Re: Dummy Load Products/8/16 ohm Head With Two 8 ohm Cabinents

Wouldn't a Tom Scholz PowerSoak work?

190131432053-1.jpg


One amp, two outputs, has a built in load and lets you select the ohm rating of the amp. I use it with tube amps with NO cabinets and it worked fine.
 
Re: Dummy Load Products/8/16 ohm Head With Two 8 ohm Cabinents

If these are 2x12 cabs (i have a feeling they are not) you could just wire the speakers in series.
That said, Every guitar player should have a series Y Cable handy.
good luck
 
Re: Dummy Load Products/8/16 ohm Head With Two 8 ohm Cabinents

Oh...OK...I see now.
Yep, Those guys ^^^^^^^ are right.....series cable. :)
 
Re: Dummy Load Products/8/16 ohm Head With Two 8 ohm Cabinents

Ok, here's the cable ....






The plug that goes in the amp is the big one with two cables coming out of it. The two smaller plugs with the blue markers are for the two cabinets. The two leads from the amp to the speakers are different lengths ... one is approx. 39" long (1 Metre) and the other is approx. 63" (1.6 Metres).

You'll need to ensure that this cable is only used when a cab is connected to each of the blue plugs. Never try to use it to power just one cabinet ... for that, use a regular speaker cable. you'll also need to ensure that no-one else ever mistakes this cable as a 'parallel' arrangement ... it is not. It is series.

Okay ... now i'm off to the Post Office. It is freezing up here but at least the sun is out, so a crisp walk along the river to town will wake me up, hehe.
 
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Re: Dummy Load Products/8/16 ohm Head With Two 8 ohm Cabinents

Aaaand .... it's in the mail.

btw, I tested the cable by measuring the total impedance with various cabs connected to this cable, and also with resistors substituting for speakers. It all checked out fine.
 
Re: Dummy Load Products/8/16 ohm Head With Two 8 ohm Cabinents

Crusty thank you so much you are awesome! Just sent you a PM too. Thanks again!

Jeff
 
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