Do i need phase control and alterable crossover? - diyAudio
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Old 7th January 2017, 06:31 PM   #1
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Default Do i need phase control and alterable crossover?

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
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Old 8th January 2017, 07:02 AM   #2
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Quote:
Originally Posted by AlbatrossPasta View Post
1)Should i trade 350W of power for adjustable phase and crossover freq?
2)So the question is: Should i trade 350W of power for adjustable phase and crossover freq?
3)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?
4)Is 250W too underpowered for my woofer?
5)And by the way, aren't plate amps supposed to be cheaper?
5)Favorite color: Orange
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
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Old 8th January 2017, 01:27 PM   #3
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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.
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Last edited by bentoronto; 8th January 2017 at 01:42 PM.
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Old 9th January 2017, 01:32 PM   #4
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Every time I run my pair of subs, I hit about 90V+ peak into a nominal 4ohm on each of them.
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Old 9th January 2017, 02:52 PM   #5
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Originally Posted by turbodawg View Post
Every time I run my pair of subs, I hit about 90V+ peak into a nominal 4ohm on each of them.
2000 watts (but less if that isn't RMS volts).

Silly math aside, what is your rail voltage(s)?

B.
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Old 9th January 2017, 04:13 PM   #6
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Originally Posted by bentoronto View Post
2000 watts (but less if that isn't RMS volts).

Silly math aside, what is your rail voltage(s)?

B.
It's with a nu6000dsp that can definitely exceed 90v at the outputs.
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Old 9th January 2017, 07:34 PM   #7
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Originally Posted by turbodawg View Post
It's with a nu6000dsp that can definitely exceed 90v at the outputs.
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.
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Old 9th January 2017, 07:57 PM   #8
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Originally Posted by bentoronto View Post
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.
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Old 9th January 2017, 08:06 PM   #9
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Originally Posted by turbodawg View Post
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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Last edited by bentoronto; 9th January 2017 at 08:17 PM.
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Old 10th January 2017, 03:26 AM   #10
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Originally Posted by bentoronto View Post
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.
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.
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