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More output for my rig wanted.


Tattoo

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I need more output from my bass rig.

I have an Eden WT550 apm plugged into an Ashdown ABM 410H cabinet.

Playing style is speedrock. And I like the sound I have now very much.

For practice and small gigs this is enough, but for larger gigs without PA this is not cutting it.

My instinct tells me to add an other ABM 410H.

But if I can do it with just 1 cabinet that would be better for my back.

What do you guy's think?

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I have the same amp, along with Eden D210XST, D210XLT and D115XLT cabs. So I can mix and match for different sounds and greater or less output.

 

With the two 2x10s, running the amp at 4 ohms, it pushes serious air.

 

Because of the amp's rating, I could actually use all three, although I never have. Kind of afraid to.

"Tours widely in the southwestern tip of Kentucky"
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I've used my GB ShuttleMax 12.0 with 2 ACME LowB-2s (vertical) for a while now...

600 watts per cab.

 

Blows the hair I have to cover the bald spot.

Moreorless...

 

http://i290.photobucket.com/albums/ll253/JBFLA/Genz-Benz%20ACME%20LowB2/Genz-Benz-ACME013.jpg

Jim

Confirmed RoscoeHead

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Hmmmmm. A pair of 2x10. Interesting. And likely easier to manhandle than the 4x10 - since I rarely (never) use the full stack anymore.

 

Yup -- more portable, more flexible.

 

Pardon me, lads and lasses, for I have an act of shopping to execute.

 

Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn

 

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Yeah the 210 vertical stack is the best config that I've ever used. I have a couple of Avatar B210 neos that I many times run under my Genz shuttle 6.2 or Carvin BX500. One trip in and out on the Magnacart dolly. JBFLA's rig pictured above looks absolutely killer! I've also the GK MBE212 cab in 4 ohm for super light/compact transport that I also use standalone with excellent results. I could actually run all three cabs under the Carvin because of that little 2ohm button on the back, but good grief already!

 

Tattoo already has the 410. If he's young and doesn't mind all that weight, then he would notice immediate and very positive results with a second 410 stacked on top if more output is needed. Happy Easter!

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I suppose it wouldn't be bad at this point to interject the boring science behind volume.

 

There are really a few things to consider that are all inter-related....Speaker Sensitivity, Size/Excursion, Load, and Power.

 

Sensitivity is very important (the cabinet you have is 103dB 1W/1M...more on that in a minute). This is how much Sound Pressure Level (SPL) is measured at a 1 Meter distance with 1 W input. Every 3dB increase require Double power. So 2W add 3dB, 4W add 6dB, 8W add 9dB, etc...then also consider, every time you double the distance away, you reduce the level by 6dB (unless it's a line array). What we would mostly perceive as "twice" as loud, roughly 10dB difference, is 100x the power (so in the SAME speaker, SAME distance, 100W sounds twice as loud as 1W). This doesn't seem right, but it's true. So the difference between 350W and 400W in an amp is negligible. You'll get more volume out of speaker efficiency than the amp any day of the week. 100W into a speaker with a 100dB SPL is equal to 800W into a speaker with a 91dB SPL (if it can handle it and actually do something with it...more on that).

 

So adding speakers also adds efficiency. Given the same speaker, doubling the number effectively adds 6dB max output (3dB sensitivity). So a 4x10 has 12dB higher max output,6dB higher sensitivity. So with no increase in power, you can get higher output with more speakers.

 

Displacement/Excursion: Speakers have a thermal limit, and a mechanical limit. Thermal limit is power handling - go beyond that, they overheat, and the voice coil melts and it's blown. Mechanical is how much air they can move. This is a factor of Surface Area (Sd) which is literally the measured cone area. So obviously a 15" cone has more area than a 10" cone. The other pare is excursion - linear movement, measured as Xmax. The end result is the VOLUME of air it can move before it's done. Areas times excursion. So the maximum SPL of any speaker is a combination of Thermal Limit, and Mechanical Limit. Usually at higher frequencies, you hit the thermal limit. At lower frequencies (since more air movement is required) you run into the mechanical limit.

 

So amplifiers put out a rated amount of power into a certain load. THEORETICALLY, ohms law would say it should put out twice as much power into 4 ohms than 8 Ohms, and twice as much into 2 ohms than 4 ohms. But real world amps don't work that way. Realistically, if it's 500W into 4 Ohms, rather than 250W into 8Ohm, it might be more like 350W. The reason being that there are INTERNAL resistances in the amp. So as it flows more current (lower load resistance means more amps - current), more power has to be dissipated along the way. So it get's lost as heat. SO if it's 350W at 8 ohm, instead of 700 W at 4 ohm, it might only be 500W because 200W is going into heating up the heat sink on the back of the amp. Also, amps have a limited range. Most are safe with 4-16 ohm ranges. Most USED to be optimized for 8 ohm loads, but more are not optimized for 4 ohms. Most are not safe at 2 ohms, but some are. Usually it's safe running higher, you just don't get much power. Running lower can damage the amp.

 

So there are 2 ways you can hook up speakers, series and parallel. For the most part, you'll only deal with parallel. IF you plug 2 cabinets into 1 amp, it will be parallel. The formula is Load = 1/(1/A + 1/B + 1/C + ...) To simplify, if they are ALL the same, you just divide by the number. Two 8 ohm cabinets are 4 ohm. Three 8ohm cabinets are 2-2/3 ohms. Four 8ohm cabinets are 2 ohms. To wire series, you have to take the wires and wire + to -....+ from one cabinet to the amp, it's - to the + of the other cab, that cab's - to the amp. Loads ADD in series. You can do a combination (series-parallel). SO two 8 ohm cabinets in series for 16 ohms, plus another pair in parallel with those to bring it back to 8 ohms. That's what's happening in your 4x10 cabinet. Each of the 4 speakers is 8 ohm. They are in a series-parallel configuration to make the system 8 ohms.

 

 

 

So in the recommendations to add another 8 Ohm, 103 dB, 4x10 cabinet, I can only speculate on a few things. Assume your 500W at 4 Ohm amp is putting out 350W into the current 8 Ohm Load. I would put that at a max output of roughly 128dB. So add another one, your base efficiency increases to 106 and you get the full 500W out. I would put that closer to 133dB max output, plus your MECHANICAL limit will be MUCH higher, so that low frequencies won't fart it out. But midband I'd put the max output 5dB louder which is pretty significant.

Dan

 

Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth.

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133 dB? That's about as loud as a jet engine from 100 feet away.

 

at a distance of 1 M. Remember it decreases 6dB every time you double that distance. So out in the crowd, say 8M away, that would be 18dB quieter, or in this example 115dB.

 

Plus it's unlikely it would actually get that loud. There's another thing called power compression. The response of the cone is not completely linear with added power. As it approaches the limit of it's excursion, it gets stiffer, moving less and less. Also, as the voice coil heats up, the resistance increases, resulting in less power being delivered. So as you approach the max output of a driver, you get less increase in output with more power.

 

But yes, that is very loud.

Dan

 

Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth.

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Also, as the voice coil heats up, the resistance increases, resulting in less power being delivered.

 

resistance decreases with temperature. the lower resistance causes more current draw and therefore more power, most of which is lost as heat. the heat generated actually causes the magnet to lose some of its magnetism. eventually a magnetic material will lose all magnetism when it reaches its cure temperature (mercí, pierre!), but a speaker magnet will not come remotely close to that point. it reaches a fraction of that, but enough to have measurable loss of magnetism.

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Thanks for the responses!

Especially J. Dan.

 

If I add an other cabinet, then power compression should be less than with 1 cabinet.

A bit of calculation: 350W into 4x10"= 87.5W per speaker is more than 500W into 8x10"=62.5W per speaker per speaker. So the voice coils should be cooler with 2 cabinets, resulting in less power compression.

 

The Eden cabinets are an option to, but I can't find their efficiency ratings anywhere.

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Also, as the voice coil heats up, the resistance increases, resulting in less power being delivered.

 

resistance decreases with temperature. the lower resistance causes more current draw and therefore more power, most of which is lost as heat. the heat generated actually causes the magnet to lose some of its magnetism. eventually a magnetic material will lose all magnetism when it reaches its cure temperature (mercí, pierre!), but a speaker magnet will not come remotely close to that point. it reaches a fraction of that, but enough to have measurable loss of magnetism.

 

You are correct about magnetism as well, but resistance DOES increase with temperature.

http://www.stereophile.com/images/archivesart/1106howardfig1.jpg

 

From the following article which describes both effects:

 

CLONK

 

 

NOTE: The physics behind that is that as the metal heats up, it expands, making the molecules further apart so that the electrons don't flow as freely from one to the next.

Dan

 

Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth.

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Thanks for the responses!

Especially J. Dan.

 

If I add an other cabinet, then power compression should be less than with 1 cabinet.

A bit of calculation: 350W into 4x10"= 87.5W per speaker is more than 500W into 8x10"=62.5W per speaker per speaker. So the voice coils should be cooler with 2 cabinets, resulting in less power compression.

 

The Eden cabinets are an option to, but I can't find their efficiency ratings anywhere.

 

Yes. 103 dB is pretty high for a 4x10 because in order to extend low frequency response in a 10" driver, they have to sacrifice efficiency. So I doubt you'll find much better than that.

Dan

 

Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth.

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the full 4ohm wattage

 

i don't mean to call you out specifically, but 4OHM POWER! is an aggravating misconception of how power works. for me it's like:

 

[video:youtube]

 

so here's some real science to explain why, because it's not entirely intuitive or obvious how power works.

 

let's assume we have two single cabinets that are identical except that one is 8Ohms and one is 4Ohms. it's true that the 4Ohm power draw will be greater than 8Ohm power draw. while theoretically it should be 3dB greater design limitations in reality reduce the difference to something less than that. at 4Ohms the WT550 outputs 500W, which is 2.2dB more than its 300W 8Ohm output. consider, though, that you need to increase the power by four times to double the SPL output (never mind the psychoacoustical rule that you need 10x power to double the perceived loudness). there will be an increase in SPL that will be noticeable, though not drastic. as mentioned in previous posts there are non ideal performance artifacts like power compression to contend with. but there is at least a theoretical opportunity to achieve performance improvement that can largely be described as headroom. it might allow improvement in low end reproduction or audibility in a tight, loud mix. but it won't be obviously louder.

 

now assume that you have two identical 8 Ohm cabinets. right away that doubles the SPL (assuming the same power input), meaning you have 6dB more output. that's equivalent to quadrupling your amplifier power with one cabinet. if you're keeping track at home that's the same as quadrupling the power.

 

the last little bit of slight of hand regarding 4OHM POWER! is that each cabinet actually draws a little bit less power compared to a single cabinet. think about it. you have 300W at 8Ohms for a single cabinet. two identical cabinets sharing 500W divides it equally to 250W per cabinet. it's less than 1dB difference, though, so it's extremely minor. but it shows what happens when you follow the numbers.

 

conclusion: using a single 4Ohm cabinet instead of a single 8Ohm cabinet because 4OHM POWER! makes very little sense in trying to get louder. what minimal gains you achieve in power output don't result in appreciable differences in loudness, and they are further limited by non ideal performance like power compression. using two cabinets makes you much louder because two cabinets. it does not make you louder because 4OHM POWER!.

 

as always i can expand on any of the math or theory behind all of this, so please ask questions or PM me.

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I have a WT-550. It can handle a 2 ohm load. They are 500w at 4 ohms but depending on year, 2 ohms will be 620w or 750w. My 2005 head is the 620 model. newer ones are 750.

Yup, my experience is that the 550 will run all day on a 2-ohm load.

 

The fan will run a bit more though.

 

And actually, I don't think they uprated the amp -- I think they just revised the specs.

"Tours widely in the southwestern tip of Kentucky"
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  • 2 weeks later...

1. First, what is speedrock? :confused:

 

2. Glad to hear 350W/4x10 is enough for rehearsal. ;)

 

When I tried more than that (with two guitars with full-stack Marshalls) the drummer gave up because he couldn't hear himself anymore. (Irreversible hearing damage, anyone?) :o

 

3. Why are you doing larger (outdoor, I hope) gigs without PA support?

 

I did a show once (indoors) with professional sound run by an engineer but the stage volume was so insanely loud that all I could hear was a swirling whoosh of incoherent sound. I had to literally watch the drummer hit his kit to find the beat. (Surprisingly I was going through a MarkBass combo with tilted 2x10 that somehow kept up.)

 

So, as you can imagine, I am now a big fan of lower stage volume with as big a FoH ("front of house": PA in front of the band facing the audience) as necessary to fill the venue.

 

You may be better off investing in some PA gear such as a crossover (to split the high and low frequencies) and either a powered sub(s) or, equivalently, a power amp and a passive sub(s). (Your drummer will thank you, too, since he can run his kick through it as well.)

 

4. Overly loud distorted guitar can make it hard to hear lower bass notes due to what is called "frequency masking".

 

If your guitarist plays a 7/8-string guitar or tunes down to drop-D or -C this will make things even worse for you. Maybe getting him to turn down (I know, I'm asking for miracles here :D ) can result in a better overall band balance. (Again your drummer will thank you as his kick is getting masked, too.)

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