Speaking of speakers...

[Brad1]

Here's something I've wondered.

I have several amps that can be used with any of several cabs. I have a Marshall 1960 Vintage cab which, of course, has the Mono/Stereo switch/jack panel on the back. I also have a vertical slant 1/2-open/1/2-closed 2-12 Mesa Boogie cab. I added an aluminum plate inside the upper (open) section with two 1/4" jacks, paralled and connected to upper speaker. That would allow me to run two amps, or just run a cable from output of one amp, then a cable from the other paralleled jack to the lower speaker's stock input jack.

I can use the JCM800, a BF Bandmaster, a Marshall 9000 power amp...whatever...to either of those cabs. Normally, with one amp, I'd just plug one cable from the head to a cab, and with the Marshall, just run it mono, or with the Boogie plug into the upper, then run another cable from that down to the bottom.

I'm wondering? Are there any advantages...safety or soundwise...to running two speaker cables from any of the heads' extra speaker out(s) to (either) the two inputs of the Marshall cab (set to stereo and ohm-considered), or directly to the Boogie's top and bottom inputs?

Safety, maybe if one speaker cable went bad, at least there'd be SOME load present...I'd probably notice it to deal with it fairly quickly...possibly saving the amp from a no-load meltdown? Soundwise? In the case of the Boogie, if running top-to-bottom, the cable from the top to the bottom adds a bit of extra cable that the top doesn't see? As in, signal split right at amp out, traveling through two identical cables to their respective destinations?

In the case of both cabs, there is always some form of parallel connection, either way, so one blown (disconnected voice coil) speaker wouldn't severe the entire load, so that isn't my main concern. My main concern would be relying on only one cable from amp to cab.

So, good idea to run two cables? No difference, in functionality? Possible difference/absolutely no difference, in sound? Who cares, and why am I asking such a goofy question?

Just wondering.

Brad1

[soundguruman]

NEVER run an amp into a blown or damaged speaker. The impedance must match the amp exactly.

[Rhodesplyr]

Personally, I'm having a hard time trying to follow your description of your speaker setup and its relation to the question you're asking. On one hand, it sounds like you're creating individual connections to each driver in the cabinets, but, on the other hand, you're saying that "there is always some form of parallel connection." Perhaps a diagram might help...

[soundguruman]

That's right. The description makes no sense.

[Chuck H]

What the OP is suggesting is that with an amp that has two outputs and a cab that has two inputs one could run a cable from each output to each input and possible reduce the likelyhood of an ope or shorted load.

I wouldn't bother. If your THAT cogniscent of the issue, your not likely to have a problem with one cable. And two cables is just twice the possibility that the amp ends up into an incorrect load or a short, right?

[Brad1]

Chuck got it. And, this is all actually just more of a curiousity than a worry, anyway. I had too much time on my hands last week, and started thinking. I do inspect my cables regularly, so I'm fairly certain they won't fail...but...

The Mesa Boogie cab and the Marshall cab can both be "split", or they can run "mono".

The Marshall can be done with a simple switch, and I can plug it in for 4 or 16 ohms mono, or 8 ohms split.

The Boogie cab was a bit modified. It was originally just 4 ohms mono (two EVM12L-8 ohm speakers), plugged into the jack on the bottom covered-back portion (the top is open-back). I added an aluminum "L"-shaped bracket inside the top, and paralled two 1/4" jacks. I can run it split (two 8-ohm), or plug a cable from amp into one of the jacks on the added plate, and run another cable to the bottom, to parallel it for "mono".

Basically, on that one, I'm plugging into the top and adding an extra 3-foot of speaker cable to get to the bottom speaker.

I know if a speaker "shorts" that no matter how it's connected, it's going back to the amp output. That wasn't really my question.

Now that I think about it, in any combination I could do, if one speaker blows (open) there will always be at least one other paralleled to the amp's output to keep it from a complete "no-load" situation, even though the impedance will then be wrong. But, if only one cable is used, and the cable happened to "open", it could cause a "no-load" situation. Using two cables won't keep things from going wrong, but it may save a complete "no-load" situation, since two cables are likely to fail at exactly the same time?

I realize no amp wants to see a sudden drastic impedance change. I also realize some amps, like Marshalls are a lot more fussy about wrong impedance, than others...like Fenders that can usually run fine at one-off, from the "Ext Spk" jack.

In the case of the Boogie, since I've made it so I have to use two cables, anyway, may as well run the cables straight from the back of the amp to the top and bottom? It'll split the power out from the amp through two cables to the respective speakers. As it is, since I've ran the amp to top, then top to bottom, I'm pushing all the power first through one cable, a short run to the top speaker, then 3 ft. extra of cable to the bottom speaker. May as well just run two cables from amp?

So, there were really kinda two questions in there. Would the sound be affected in even a minute way (good or bad) running one cable vs. two? Would splitting the power right at the output make difference as run through two cables, instead of squeezed through one? In the Marshall's case, would the extra 3 ft. cable actually hinder the signal, as opposed to one? (The Boogie HAS to use two cables, anyway. I did that because I WAS using it with a Marshall 9005 power amp in stereo mode). And, could it even 'possibly' avert a potential no-load situation, and if something DID happen (like one of the two cables opened, or a speaker opened) what would an amp running at the time think about it?

As I said, just curious. Nothing's ever happened...yet (knock on wood). Just wondering.

Brad1

[g1]

Yes it would prevent a no-load condition if one cable failed, the second would still be connected. Otherwise sound wise etc. you are basically doing the same as if you were to run thicker cable. For the amount of power you are running it would probably not be noticeable.
Here's a chart showing power loss for different gauge of speaker cable:
wirechart.pdf

[Chuck H]

On that subject, isn't it true that LF is really what gets bumped since HF doesn't occupy that much of the power? In other words, doesn't the HF suffer less power loss than the LF???

[g1]

On that subject, isn't it true that LF is really what gets bumped since HF doesn't occupy that much of the power? In other words, doesn't the HF suffer less power loss than the LF???

For equal impedances the percent of power loss would be the same, but as you say, when the LF is hogging more power that percentage will mean more wattage lost in the low end.
The impedance curve of the speaker involved will be the big factor, dips in the impedance will have higher % of power loss.