TLDR: Should i trade 350W of power for adjustable phase and crossover freq?
Hello, I'm planning to building my first subwoofer but I'm a bit stuck when it comes to picking the amplifier, right now I'm pending between a the 250W plate amp SAM-500D or the 600W rack amp Samson Servo 600 combined with a 250Hz passive crossover. Where I'm buying them the latter alternative ~18$ cheaper.
So the question is: Should i trade 350W of power for adjustable phase and crossover freq? The way I see it you only set the crossover freq once and stick with it and phase control can be accomplished by moving the sub around the room? Is 250W too underpowered for my woofer? And by the way, aren't plate amps supposed to be cheaper?
rgrds
Fun facts!
Woofer: 600W Eminence Kappa-15LFA
Total budget: ~440$
Favorite color: Orange
Currency: USD
Enclusure type: Sealed
All ohm values: 8Ω
Hello, I'm planning to building my first subwoofer but I'm a bit stuck when it comes to picking the amplifier, right now I'm pending between a the 250W plate amp SAM-500D or the 600W rack amp Samson Servo 600 combined with a 250Hz passive crossover. Where I'm buying them the latter alternative ~18$ cheaper.
So the question is: Should i trade 350W of power for adjustable phase and crossover freq? The way I see it you only set the crossover freq once and stick with it and phase control can be accomplished by moving the sub around the room? Is 250W too underpowered for my woofer? And by the way, aren't plate amps supposed to be cheaper?
rgrds
Fun facts!
Woofer: 600W Eminence Kappa-15LFA
Total budget: ~440$
Favorite color: Orange
Currency: USD
Enclusure type: Sealed
All ohm values: 8Ω
1)350 watts compared to 600 watts is less than a 3 dB difference, assuming the "watts" are equivlent.
2) Question # 2 is quite similar to #1, would you trade a car with a 3 speed transmission and good steering for a car with a four speed transmission that falls over on turns?
3) You see it rather differently than measurement would suggest.
4) "Underpowered" is a b.s. description, one's subs either reach the desired SPL or they don't.
5. Cheaper than watt?
6. Sweet.
Cheers,
Art
Folks on the sub forum favour unrealistically high powered amps. Can't recall any post that measured or observed peaks on a scope, except by inference from specs. I'd like to see somebody post, "I played my system almost as loud as I'd ever want, and the highest brief peak voltage I ever saw going into my 7-Ohm driver was 14 volts".
Likewise, using the usual wannabee engineering, folks choose a crossover frequency and build from there. In reality, you can't be smart about your crossover freq (which is sometimes arbitrarily too low even for mixed bass subs) until you are setting up your system in your room.
You'd start with say 100 Hz and see how the sub plots and then the mains. At those freq the room plays havoc on the curves and differently for each location.
While adjustable crossover point is an important control to have, a plate amp is not certain to have good circuits and with a choice of slope. Anything less than 18dB/8ave is going to be too mild a slope to keep the bands out of the wrong drivers. So you'd want a DSP or at least some purpose-built unit.
Phase (and often even polarity) are factors that seem essential in grade-school theory but are fairly unimportant in practice with a sub box separated from the main speakers (or if your theory goes beyond textbook pictures).
B.
Likewise, using the usual wannabee engineering, folks choose a crossover frequency and build from there. In reality, you can't be smart about your crossover freq (which is sometimes arbitrarily too low even for mixed bass subs) until you are setting up your system in your room.
You'd start with say 100 Hz and see how the sub plots and then the mains. At those freq the room plays havoc on the curves and differently for each location.
While adjustable crossover point is an important control to have, a plate amp is not certain to have good circuits and with a choice of slope. Anything less than 18dB/8ave is going to be too mild a slope to keep the bands out of the wrong drivers. So you'd want a DSP or at least some purpose-built unit.
Phase (and often even polarity) are factors that seem essential in grade-school theory but are fairly unimportant in practice with a sub box separated from the main speakers (or if your theory goes beyond textbook pictures).
B.
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2000 watts (but less if that isn't RMS volts).
Silly math aside, what is your rail voltage(s)?
B.
The amp claims 3100 watts at 4 Ohms which is a roughly 110 vrms for a total rail voltage of maybe 200 vdc. So your observation is plausible if Behringer's figures are trustworthy.
But just what are you powering that can handle 2000 watts... even in short bursts? And are you wearing ear plugs to preserve your hearing?
These are just my Acoustics 101 figures. I hope others will wade in.
B.
B&C 15TBW100 4ohms in 2.5 cubes net, tuned to 35hz. Compact PA subs. I almost always max out the amp and the system hits about 115 db at 20 feet.
OK, it looks like your data might possibly be coherent. But your ear-destroying levels in a large room or out of doors is hardly meaningful to those who are playing in more modest spaces indoors and at levels which are only ear-destroying if played for a while*.
Which you should have noted earlier, in fairness to others.
Now, can somebody please provide a peak reading in an environment resembling home audio?
Ben
*and in homes that do not have a special industrial electric supply needed to adequately power even a single channel of your amp.
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OK pal. You're the one who wanted people to post how much power/voltage the were putting out when playing loud enough. My amp hits limiter at a bit over 90V, (instant peak) RMS voltage. As confirmed by voltmeter testing with no load, and bench testing.
How much power you need depends very much on the efficiency of the subwoofer. I often run out of power with my two slewmasters with +-72V supplies driving two lab 12s in sealed enclosures in my living room.
If I built horns instead, I probably wouldn't need much power.
Ben,
1)Behringer's specifications are worthy of trust. Although I did not test the peak level of my several NU-4 6000, I did test the average output with all four channels loaded equivalent to 2 ohms, using two pairs of the channels bridged mono into load resistors.
Just before the 2015 Christmas holidays I conducted a battery of tests on some old amplifiers and a new Behringer NU4-6000 four channel amplifier. To my surprise, the NU4-6000 performed as well on low frequencies as on mid/high frequencies, and is capable of near full power sine wave output with all four channels driven to rated output at two ohms, or two bridged mono pairs driving four ohm loads each. The $350 NU4-6000 appears to be within 3 dB of the $5500 Powersoft K10 published rating on sustained (more than 1 second) output.
The NU4-6000 with two bridged mono pairs each driving four ohm loads just below the illumination of the clip/limit light each put out 85.5 volts at 60 Hz (1828 watts), 84.6 volts at 30 Hz (1789 watts), dropping the mains voltage on a 100' 10AWG 120V line from 118.1 volts down to 107.2 volts, drawing 31 amperes.
Using just one bridged mono pair, the amp ran for 40+ seconds before I terminated the test, as the amp was drawing 19.8 amperes, and the "tired" 20 amp mains breaker had popped several times in various tests already. The amp would have put out more power given a full 120 volts, but the test represents a "real world" situation, we don't generally plug our amplifiers in to an outlet two feet from the mains transformer.
I also tested my old "heavy iron" bass favorite, a Crest CA9. Bridged mono into a 4 ohm load it dropped the mains to 99.6 volts, drew 37.8 amps but only put out 80 volts (1600 watts).
The NU4-6000 put out more power, and drew only 50% of the power from the mains compared to the CA9, and weighs a small fraction of the "heavy iron".
My back (and bank account) are very pleased with the NU4-6000, after the testing I have continued to purchase more, and have been happy to find my only complaint, the noisy fans, have been "fixed" in the later units with no price increase.
2) The B&C 18SW115-4 (four ohm) can effortlessly handle the short term 3000 watt peaks the NU4-6000 can deliver, and can handle the "full tilt boogie" sine wave output for several seconds before the voice coil starts to stink badly.
A pair of relatively inexpensive Dayton PA385S 15" 8 ohm drivers in parallel can handle the "full tilt boogie" sine wave output of the bridged NU4-6000 for longer, but don't sound as clean as the B&C 18SW115-4.
3) Now that I have my waders on, any more questions ;^) ?
Good day,
Art
Art -
Well, that's quite definitive. Good thing your 20 amp circuit breakers let you pump out 30+ watts... briefly, I suppose. Until the burning smell from the VC is too awful.
I own a few Behringer things and trust their specs.
For testing my sets of puny Kenwood Basic M2 650 watt Class G amps, I have a wood dowel about 4 feet long holding a series of 100 watt resistors and some heavy wire leads. Wish I could photograph it today.
But the real question for OP is still how many dBs would your B&Cs at 3000 watts produce in his room. Or even out of doors (which allows indoor loudness to be approximated).
If you can produce that figure (which you easily can), I suspect we'll all have a chuckle.
Ben
Ben,
Room questions are best resolved with measurement and listening, it makes little sense to worry about the speakers if the room rattles louder than the bass..
For comparative testing the NU4-6000 and several other amps, I simply wound about 100 feet of baling wire around bricks to make two four ohm loads. I also had several resistive only space heaters to use as loads.
I have measured the level of the B&C18SW115-4 loaded Keystone Subs on many indoor and outdoor venues, with and without extenders.
Working back from my usual mix location at 20 to 45 meters from stage, the "real world" (what you see from a typical SPL meter on "fast", "C" or "Flat") outdoor output for a pair is in the 136 dB SPL peak range at one meter without exceeding Xvar over the pass band of 35 to 100 Hz. In the upper end of the pass band, levels above 140 dB are easily attainable, and 3 dB average SPL can be added to the above when the extenders are used.
Cheers
Art
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That's swell, but OP wants to know what power to buy.
Despite all the loose talk on this forum forever about power, nobody has the data to post an answer so far. I have a feeling we aren't going to hear from anybody who knows how to convert spec's to loudness in a room.
Ben
Folks on the sub forum favour unrealistically high powered amps. Can't recall any post that measured or observed peaks on a scope, except by inference from specs. I'd like to see somebody post, "I played my system almost as loud as I'd ever want, and the highest brief peak voltage I ever saw going into my 7-Ohm driver was 14 volts".
This premise is incredibly biased and what you are asking is a pointed question that you are hoping will yield answers that you expect but that doesn't consider context at all.
Sure, in your system with a single antique 12 inch sealed sub with 2 mm xmax that can't play any real bass within it's xmax limits, 14 volts might produce a nice result in your small apartment which looks like it's got concrete walls, floor and ceiling. But it will be a modest spl level and won't have any low bass - otherwise the system would defy the laws of physics and you would have been kicked out of your apartment.
Some people want more than that so let's have a big heaping dose of context please.
Here's your requested data on measuring amps on a scope. Note that this is only the most recent in an ongoing series of threads in which most (if not all) of the popular amp models have been tested.
Measuring Amplifiers - AVS Forum | Home Theater Discussions And Reviews
This is the type of data that is measured (along with a lot of other things). This is the Behringer EP4000 (which is of interest because I have one) and we can see that at 10 hz it can do 1327 watts sustained and it can burst about 60 watts more than that. While it can burst it's rated 4000 watts at some mid khz frequencies, in the bass where it really matters it's a 1500 watt amp.
This is just one of the reasons why you might see a lot of amp power in a room. And by reading through that thread and it's predecessors you can find out intimate details of how most of the popular amps perform.
This provides some form of context for amps. Even the upgraded LG FP14000 clone will only do 3800 watts continuous. People that play media with continuous tones (more than 1 or 2 seconds in duration) will need a lot of amp regardless of the burst number printed on the amp case.
Next let's look at trends in home audio. There's a big push towards putting the largest possible drivers into the smallest possible sealed enclosures and using brute force power to move the cones. This is incredibly inefficient and it's the reality shown in data-bass testing. He routinely dumps 5000 or so watts into a single 18 inch driver in a 4.2 cu ft sealed box.
And what do you get for the effort? About 100 db / 10 hz / 1m max spl when measured outside. 100 db at 10 hz is barely perceivable. So you need multiple subs and multiple amps.
This chart is showing some aspects of some avs forum member's systems.
This is just a small sampling of avs users and these systems are nothing extraordinary, look at how many people are using eight 18's for subs. And they are mostly all using them in small sealed boxes.
If you want more context into that chart (and to see many more charts like that with avs user systems), check the thread. It's a bit flawed in it's premise but it's very interesting.
Your Home Theater ULF Score - AVS Forum | Home Theater Discussions And Reviews
And here's just a couple of random avs posts I found in a 24 second search, just copied and pasted here to show some context of the new normal, which is diametrically opposite of your system, Ben.
too much bass???!!!! - AVS Forum | Home Theater Discussions And Reviews
Here's a lil tease of what's to come - AVS Forum | Home Theater Discussions And ReviewsScott you have somewhere between 26 to 28kW there, if I counted it correctly.
Big-Iron Class-A/B/H too, so it likely does a solid 18kW RMS, with another 10kW burst power in the capacitors from an idle-start.
And here's a recent HT of the month featuring a dozen 24 inch subs powered by 4 of the best amps on the planet, SP2-12000.
HT of the Month: The Hahn Theater - AVS Forum | Home Theater Discussions And Reviews
These systems all use the necessary equipment to achieve the design goals - low distortion, high spl at very low frequencies, usually using very inefficient bass enclosures.
Sure, you can go deaf with a couple hundred watts worth of PA equipment playing at typical 1970's PA frequency range (no low bass), but that's not the context of today's home reproduction systems built by people that understand the entry fee and appreciate the results.
System like the ones shown here can do maybe 120 - 140 db at 5 hz in room at the listening position with eight fully powered high excursion 18s, but that depends a lot on the room too. These are systems doing what they are designed to do, and it takes a lot of power.
Your home system would have been pretty nice in the 1950s but it's a far cry from what people with different goals are able to achieve.
We are not too stupid to look for or understand power data, we know all about power data. We just need lots more than you do to power your small antique system in what amounts to a concrete bunker.
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