Make Rumble 800c a cab

[toughluck]

If OP does this without fully and completely disconnecting the speaker from the amp in the broken combo, there will be two broken combo amps.

Very true.

Not to mention it won't even work before it breaks.

 

[agedhorse]

First thing: the internal speaker is rated for 300 W.
Second thing: 800 W vs. 300 W is just a +4.26 dB difference

There are two scenarios you can have:
1. You have two working Rumble 800 combos. Use the FX send jack from the master amp to the FX return jack on the slave amp. Set all the dials the same on both.
2. You have one working Rumble 800 combo, the other has a faulty amp and you want to use it as a passive cab: Use the Speakon output from the working combo. On the cab, you'll have to connect speakers to the connector, at least both woofers. Set the output impedance on the combo to 4 Ω and make sure not to exceed the maximum power of the cab (300 W).

The first way will use 600 W out of 1,600 W total. The second one will use 600 W out of 800 W total.

Neither way allows you to get the full potential of the Rumble 800 combo amp. AND THAT'S PERFECTLY OKAY!

Let's get a few things correct in scenario 1:

First, the rated power at 8 ohms of the amp and speakers is 400 watts not 300 watts.

Second, when using the effects return, the ONLY control that is active on the slave amp is the master volume control.

 

[Bass Jones]

If OP does this without fully and completely disconnecting the speaker from the amp in the broken combo, there will be two broken combos.

It appears he did this some time in the future and discovered it was a bad idea. Then traveled back in time to ask here to avoid the mistake. Clever.

This whole thread will disappear once time catches up to him and he makes the right decision...

 

[G-Dog]

First thing: the internal speaker [of the Rumble 800 combo] is rated for 300 W. ... ... ...

No, the standalone R800c can output up to 400 watts into its internal speakers. I would expect any actual rating to be at least that, if not more.​

... ... ... There are two scenarios you can have:
1. You have two working Rumble 800 combos. Use the FX send jack from the master amp to the FX return jack on the slave amp. Set all the dials the same on both. ... ... ...

Let's get a few things correct in scenario 1:

First, the rated power at 8 ohms of the amp and speakers is 400 watts not 300 watts.

Second, when using the effects return, the ONLY control that is active on the slave amp is the master volume control.

Of course, you're right on both counts, Andy.​

... ... ... The first way will use 600 W out of 1,600 W total. ... ... ...

No, this first way of connecting two working R800 combo amps can output up to a total of 800 watts, at 400 watts each. The only way to get up to 1,600 watts would be to add an extension cab to each combo amp!​

... ... ... 2. You have one working Rumble 800 combo, the other has a faulty amp and you want to use it as a passive cab: Use the Speakon output from the working combo. On the cab, you'll have to connect speakers to the connector, at least both woofers.

No! Better to completely remove the faulty amp chassis (including the Extension Speaker connector) from the prospective "cab" first, and make sure the two 10" speakers are disconnected from everything else but each other. That's to avoid any dangerous accidental connections. Then install a new speaker jack into the "cab" back and connect it to one of the two connected 10" speakers.​

... ... ... Set the output impedance on the combo to 4 Ω and make sure not to exceed the maximum power of the cab (300 W). ... ... ...

No, not unless you just want to reduce the output! The new "cab" can handle the full 400 watts it may receive. And, since it is 8 ohms, that's where to set the Impedance Switch on the working combo for optimal output. Both the Rumble 800 combo and the Rumble Stage 800 work this way.​

... ... ... The first way ... .... The second one will use 600 W out of 800 W total.

No, this second way of connecting one working R800c to a another, converted to a speaker "cab", can output up to 800 watts total.​

... ... ... Neither way allows you to get the full potential of the Rumble 800 combo amp. AND THAT'S PERFECTLY OKAY!

No, both ways allow the full potential out of the working equipment being used without additional equipment, which is the best to be hoped for!​

 

[toughluck]

Let's get a few things correct in scenario 1:
First, the rated power at 8 ohms of the amp and speakers is 400 watts not 300 watts.

You're right, I got that confused with the Rumble Stage 800, I think. Or something else. It seems Stage 800 has the same configuration.

Second, when using the effects return, the ONLY control that is active on the slave amp is the master volume control.

I didn't bother checking the schematics, sorry. But setting the dials exactly the same means that regardless of where FX Send is tapped and where FX Return is fed, it will have the same sound (within factory tolerance). If the EQ is before the FX tap, the settings on the slave amp will have no effect on the sound, and if FX tap is before the EQ, then it needs to be the same.

No, the standalone R800c can output up to 400 watts into its internal speakers. I would expect any actual rating to be at least that, if not more.​

The rear panel states 400 W/8 Ω and 500 W/4 Ω. If the internal speakers are 8 Ω total, the effective impedance is 2⅔ Ω with 500 W going to the external cab and the internal speakers limited to 250 W for 750 W total.

No, this first way of connecting two working R800 combo amps can output up to a total of 800 watts, at 400 watts each. The only way to get up to 1,600 watts would be to add an extension cab to each combo amp!​

OP asked about using the full potential of their two 800 combos. I meant that in scenario one, if OP has two working 800Cs, he has 1,600 watts available from the two amps, but will only be able to use 800 watts of them (400 watts per amp).

No! Better to completely remove the faulty amp chassis (including the Extension Speaker connector) from the prospective "cab" first, and make sure the two 10" speakers are disconnected from everything else but each other. That's to avoid any dangerous accidental connections. Then install a new speaker jack into the "cab" back and connect it to one of the two connected 10" speakers.​

ABSOLUTELY! I don't know what the internal layout is like and whether it's even feasible to disconnect the speakon connector from the amplifier or if it's soldered onto the amp's PCB (which is possible given the position of the impedance switch). Removing the amp would definitely be the best way to go about it.

And then yes, setting 8 Ω on the working amp allows the owner to access to the full potential of the single working amp

 

[G-Dog]

Greetings. ... ...Can I take an old repaired Rumble 800c and turn it into a cab for my Rumble 800c? ... ...

... ... Will be repairing old amp and giving it a go soon

I was posting from the future.
I'm back now, thanks for holding everything in place for me.

Welcome to TalkBass in general and to the TB Fender Rumble Club in particular!

Oops! Excuse me. I was also posting from the future, after you go/went to the TalkBass Fender Rumble Club and posted something about your Rumble(s) there. Man! That was quite a reception you get/got there!!

 

[toughluck]

Welcome to TalkBass in general and to the TB Fender Rumble Club in particular!

Oops! Excuse me. I was also posting from the future, after you go/went to the TalkBass Fender Rumble Club and posted something about your Rumble(s) there. Man! That was quite a reception you get/got there!!

Man, what if WE'RE in the future and HE'S in the PAST??? You'll have to retroactively renumber everyone's club numbers, or he'll get number zero or negative one!

 

[G-Dog]

The rear panel states 400 W/8 Ω and 500 W/4 Ω. If the internal speakers are 8 Ω total, the effective impedance is 2⅔ Ω with 500 W going to the external cab and the internal speakers limited to 250 W for 750 W total.

You obviously didn't read, or understand, the rear panel where it says, "Set Switch To Match Ext. Speaker Impedance" (emphasis added), nor the link to Fender's explanation of the Impedance Switch.​

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Man, what if WE'RE in the future and HE'S in the PAST??? You'll have to retroactively renumber everyone's club numbers, or he'll get number zero or negative one!

I've been feeling like I'm in the future ever since that night I survived Y2K at work checking some of our systems!​

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But, if he took an R800c, or two, back before #1 was established in 2013, then he must've created a new timeline separate from this one. Hmmm ... I wonder if he also went to Stephen Hawking's party in that one? ​

 

[toughluck]

You obviously didn't read, or understand, the rear panel where it says, "Set Switch To Match Ext. Speaker Impedance" (emphasis added), nor the link to Fender's explanation of the Impedance Switch.​

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I've been feeling like I'm in the future ever since that night I survived Y2K at work checking some of our systems!​

​

But, if he took an R800c, or two, back before #1 was established in 2013, then he must've created a new timeline separate from this one. Hmmm ... I wonder if he also went to Stephen Hawking's party in that one? ​

I didn't miss the description, but I didn't visit the link. It says basically the same thing as I did. With one difference: the actual supplied wattage will be 266⅔ W to the internal speaker and 533⅓ W to the external speaker. Total of 800 W right there

 

[G-Dog]

I didn't miss the description, but I didn't visit the link. It says basically the same thing as I did. With one difference: the actual supplied wattage will be 266⅔ W to the internal speaker and 533⅓ W to the external speaker. Total of 800 W right there

No, you're overthinking it. Forget about the internal speakers for now. With just 8 ohms of external speakers, from the faulty combo converted to a "cab", set the Impedance Switch to 8 ohms. Then the message near the working combo's speaker connector saying "400 W 8 Ω Min" applies to that external speaker. That is all you need to consider in this case. (But, of course, the internal speakers also can get up to 400 W for the total 800 W nameplate power.)​

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Only IF you connected a 4 Ω load to the External Speaker connector, such as two 8 Ω cabs or a single 4 Ω cab, which was not being discussed, does the "500 W 4 Ω Min." message apply to the external speakers only. Then you "Set Switch to 4 Ω to Match Ext. Speaker Impedance". In that case you would be right, you could get up to 267 W to the 8 Ω internal speakers and 533 W to the 4 Ω external speakers for the total 800 W nameplate power.​

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Fender thought they were simplifying things by referring only to the external speakers on the Ext Speaker connector. But, for people that realize there is another 8 Ω speaker load internally (but don't really understand how it works), it can get confusing. Further, the message about "500 W 4 Ω Min." is rounded down from the calculated 533⅓ W for ⅔ of the total 800 W power externally. ​