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Post subject: A Question Of Wattage Distribution
Posted: Sat Feb 15, 2014 10:32 am
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A seemingly simple question for our electronics experts. On another forum where they talk waaaaay too much about bass, a certain person is claiming that the wattage of the new Rumble 500 Combo (or any amp for that matter) would be neatly divided between the two 10's of the combo and the four 10's of the new 8ohm Rumble 410 extension cabinet. Thus yielding 250 watts into the combo's two 10's and 250 watts into the four 10's of the extension effectively starving them for wattage. This strikes me as insane. Won't the six 10's present a single (somewhat fluctuating 4 ohm load) with each woofer recieving roughly the same wattage? I realize that each driver is ever so slightly different and that ohm loads are somewhat dynamic and not totally static.

Please explain this to me in bass players language.

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Post subject: Re: A Question Of Wattage Distribution
Posted: Sat Feb 15, 2014 10:47 am
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linnin wrote:
..... effectively starving them for wattage.
Those 410 cabs are too heavy anyway. They could stand to go on a diet.
:lol:

Good question, Linn. I'm kinda curious about this myself. I've never really understood that bit about how the load the amp sees from a given driver not being consistent. You don't see those comments very often but when you do I try to wrap me head around it .... unsuccessfully.

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Post subject: Re: A Question Of Wattage Distribution
Posted: Sat Feb 15, 2014 10:54 am
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BOOM! BOOM! BOOM! BOOM! Just kidding. I don't have any numbers to back my opinion, but I would think with the 4 ohms matching up from two 8 ohms speaker groups, each grouping will get the power needed to drive each speaker to it's maximum wattage as needed. Each speaker group has it's maximum power wattage, so they will handle the power for each group. Any wattage not used is backed up. I don't think there are any speakers deprived of power. it puts out the power needed for all.

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Post subject: Re: A Question Of Wattage Distribution
Posted: Sat Feb 15, 2014 12:53 pm
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If all the speakers are the same impedance then the power would be split evenly between all the speakers. But you wouldn't be able to get a total 4 ohm load with 6 speakers that are all the same impedance (unless they were all some odd non-standard impedance).

The four speakers in the ext cab have to be 8 ohms each to achieve a total impedance of 8 ohms (two pairs each wired in series, with the two pairs connected in parallel; or, two pairs each wired in parallel with the two pairs connected in series). That complicates the split -- for all practical purposes you can consider the external cab to be a single load, not 4 separate loads connected together.

Let's imagine your combo had one 8 ohm speaker and you added a cab with a single 8 ohm speaker. It's easy to see that they would combine in parallel for a total of 4 ohms, and the amp's power would flow equally to them -- half to the combo speaker, half to the extension cab speaker.

That's effectively the same thing as what you want to do. Two internal 16 ohm speakers connected together to make a single 8 ohm entity, plus 4 external 8 ohm speakers connected together to form a single 8 ohm entity. The amp "sees" a total 4 ohm load, with that load consisting of two separate 8 ohm loads. So half the power will go to one 8 ohm load, and the other half will go to the other 8 ohm load.

Speaker arrays with even numbers of speakers can be wired so that you get a normal impedance and the power splits evenly. But with an odd number of speakers, you either get a normal impedance with the power split unevenly, or you get an odd impedance with the power split evenly.


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Post subject: Re: A Question Of Wattage Distribution
Posted: Sat Feb 15, 2014 1:12 pm
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BMW-KTM wrote:
linnin wrote:
I've never really understood that bit about how the load the amp sees from a given driver not being consistent. You don't see those comments very often but when you do I try to wrap me head around it .... unsuccessfully.


That's a completely different subject. The voice coil is effectively a wire-wrap resistor, and the DC resistance presented by the coil is constant. (The DC resistance of an 8 ohm speaker is somewhere in the 6 ohm range.)

But a speaker is more than just a wire resistor -- it's a motor. Besides the voice coil turning some electricity into heat (a pure resistor), the electricity is also causing physical movement, and overcoming the inertia of the cone and the friction of the surround and spider also convert some of the electricity into heat. The cone, surround, and spider resist some frequencies more than others so the AC impedance varies with frequency.


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Post subject: Re: A Question Of Wattage Distribution
Posted: Sat Feb 15, 2014 1:22 pm
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linnin wrote:
A seemingly simple question for our electronics experts. On another forum where they talk waaaaay too much about bass, a certain person is claiming that the wattage of the new Rumble 500 Combo (or any amp for that matter) would be neatly divided between the two 10's of the combo and the four 10's of the new 8ohm Rumble 410 extension cabinet. Thus yielding 250 watts into the combo's two 10's and 250 watts into the four 10's of the extension effectively starving them for wattage. This strikes me as insane. Won't the six 10's present a single (somewhat fluctuating 4 ohm load) with each woofer recieving roughly the same wattage? I realize that each driver is ever so slightly different and that ohm loads are somewhat dynamic and not totally static.

Please explain this to me in bass players language.


It sounds like this individual has too much time on their hands and likes to ramble about such anal retentive nonsense. When you really think about it, who gives a $@!& about the wattage in each speaker as long as the damn thing works and you can hear yourself on stage? Do you think Paul McCartney or John Paul Jones (to name a few) sat around worrying about this $@!& with their bass amps? No, they just did what this person should do and concentrate on their playing or song writing. I've never read any article where they'd obsess over something that trivial. In fact, I recall seeing an interview where they asked Paul McCartney what kind of strings he used and he was something like "Uh, long shiny ones." :P

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Post subject: Re: A Question Of Wattage Distribution
Posted: Sat Feb 15, 2014 1:29 pm
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OK, so in the Rumble 500 Combo + Rumble 410 (new 8 ohm cab) how many watts would each individual speaker get? 83-84 watts a piece?

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Post subject: Re: A Question Of Wattage Distribution
Posted: Sat Feb 15, 2014 1:44 pm
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CPL wrote:
It sounds like this individual has too much time on their hands and likes to ramble about such anal retentive nonsense. When you really think about it, who gives a $@!& about the wattage in each speaker as long as the damn thing works and you can hear yourself on stage? Do you think Paul McCartney or John Paul Jones (to name a few) sat around worrying about this $@!& with their bass amps? No, they just did what this person should do and concentrate on their playing or song writing. I've never read any article where they'd obsess over something that trivial. In fact, I recall seeing an interview where they asked Paul McCartney what kind of strings he used and he was something like "Uh, long shiny ones." :P


Well CPL as you know there is a tremendous amount of anti-Fender bias, and in many cases there are negative ninnies that live to spread manure and false information. I often wonder if they play bass at all. I am there to present a positive voice for Fender Rumble Bass Amplification, so I want to be accurate and pro-active. 8)

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Post subject: Re: A Question Of Wattage Distribution
Posted: Sat Feb 15, 2014 2:26 pm
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Yeah, I've been to where you speak and have noticed that. I think there is a bias because of the name "Rumble" and association with it's past as a budget line. I can understand someone having a beef if they had nothing but horrible experiences with the product all around and actually used it (this would be honest,) but I noticed a lot of the negativity seems to be superficial and really have nothing to do with reliability.

Meanwhile, most reviews who owned the second generation series I've ever read have been positive, including mine. This is was what made me take a chance on the amp and the reason I first came here to begin with. If there was a long list of those who had reliability issues, I would have thought differently. That's why I researched it for almost a year before I took the plunge. I don't really have the chance to go out and test drive stuff in music shops, so I have to gamble a little bit sometimes.

This just seems like an attempt to troll about the amp and grasp at straws. They should just wait and see when it comes out and put through it's paces and see how it performs. That will be the true test, not how much wattage goes into a speaker.

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Post subject: Re: A Question Of Wattage Distribution
Posted: Sat Feb 15, 2014 3:22 pm
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linnin wrote:
OK, so in the Rumble 500 Combo + Rumble 410 (new 8 ohm cab) how many watts would each individual speaker get? 83-84 watts a piece?


500 watts into 4 ohms, so 250 watts to the internal speakers (125 watts each), and 250 watts to the cab (62.5 watts each).

The relationship between wattage and sound is logarithmic, not linear. So while the cab speakers won't be pushed very hard they will make plenty of sound and the overall rig will be a bit louder.

Don't expect it to be anywhere near twice as loud as just running the combo by itself. Even if all the speakers got an even distribution of power, 500w@4 ohms is only a couple dB louder than 350w@8 ohms. With the uneven split you'll get less than a 2dB increase.


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Post subject: Re: A Question Of Wattage Distribution
Posted: Sat Feb 15, 2014 3:41 pm
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Thank you for your patient answers strayedstrater. So glad I'm a bass playing tonal Gestaltist. But the 610 combo moves 200% more air than a 210 combo. Soooo psycho-acoustically it will sound easily twice as loud even through a dB meter says nyet.

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