So why do I need 1000s of watts to drive a subwoofer?

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I'm building a 18 inch subwoofer with a dayton ultimax 18 inch driver, everybody tells me I need a inuke 6000 which outputs 2000 watts per channel? Why do I need that many watts?
My previous subs a pair of 12 inch sealed I ran from a Anthony gallo amp which had a built in crossover and was rated at 250 watts and seem to drive the 12 inch drivers fine ?
 
You only need large power inputs when efficiency is low and high SPLs are desired.

A lot of modern subs are very small sealed boxes, and Hoffman's Iron Law states that those subs must be very inefficient at low frequencies. As a result, if you want useful volume levels from such a subwoofer, you're going to have to dump lots of power in there.

Chris
 
I blame it on the scarcity of otherwise authoritative-sounding people owning oscilloscopes. Because that's the way you see how many volts are going into a speaker instead of all this hypothetical chit-chat.

Funny thing, nobody seems to mention that one acoustic watt will destroy your hearing. And work the efficiency formula from there. Assuming you could produce one acoustic watt at home.*

As far as sizing amps, the real criterion is instantaneous (or momentary) voltage peaks and how you feel about the audibility of flubbing an occasional peak, say once every 10 minutes while you are blasting you and your neighbours? There's no objective answer to that question (and the answer is different for tweeters). But in many spheres of design where rational people work, the thinking is sort of "OK to have floods every X years....".

B.
* 120 dB
 
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A bit off topic, but WHY is there a need for such wattage and high DB thumping bass in a vehicle?
I'm sure the replies will be varied, but to me it's annoying and inconsiderate, to say the least.
To me, the resulting sonics inside the vehicle are pure vibration of everything that can rattle, not to mention damage due to hearing loss.
And it's not an enjoyment of music, particularly the vile lytics that I've heard quite clearly from hundreds of feet away while relaxing on my sofa.
What is the attraction?
 
I once ran mono, one old beat Karlson K15 re-tuned to ~28Hz per Exemplar with a bit of boost at fb and Altec 416z(? - qts ~0.23) off one channel of a weak JC Penney receiver (maybe 20w/channel) with the receiver's other channel driving a Karlson 12 with vintage weak-motor Allied Knight coax (maybe Jensen) and 80Hz xover. The sound was fabulous on theater organ cds. Perhaps the old Altec's low mass and good linearity had something to do with the lack of muddiness or droning.
 
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What is the attraction?

Because it's fun!

A little while ago, I experienced a system with 16x horn-loaded 18" drivers, with kilowatts behind them.

I had earplugs in, of course. The thing was this - at that sort of level, the bass was as much felt as heard. The sensation is like nothing else, and can be very addictive - just as some people like rollercoasters or sky diving, some people like to seek the most intense bass they can find.

Chris
 
Car is a bit different.

Otherwise, I plan on 100 watts per driver, thats about it, +20db.

Even then, a 100 watt amp into 8ohms, that's tested into a resistor.
A speaker is more of an inductor, so there is a phase angle to the power.
100 watts really is more like 50 watts through the speaker.
 
I once ran mono, one old beat Karlson K15 re-tuned to ~28Hz per Exemplar with a bit of boost at fb...

+1

Another funny thing is that if you have overwhelming power, you might be dragged into the mud at normal listening levels. Even with a good S/N, you might start hearing the noise.

That is related to a new set of issues people face today regarding bits and gain management.

Makes 1000 watts start to think not so smart.

B.
 
You don't but keep in mind that 10x the power is an increase of only 10 dB which translates to 2x perceived loudness. I think they are recommending the amp as it's hard to beat the price point and it will offer you a good amount of headroom.


grahamricho :

For example

10 to 20 watts = + 3 Db
20 to 40 watts = + 6 Db
40 to 80 watts = + 9 Db
80 to 160 watts = + 12 Db
160 to 320 watts = + 15 Db
320 to 640 watts = + 18 Db
640 to 1280 watts = + 21 Db
1280 to 2560 watts = + 24 Db
2560 to 5120 watts = + 27 Db
5120 to 10240 watts = + 30 Db
 
In any case, it is better (especially in SS and AB class) to have more power, so that you never reach the clipping area.
That requires a basic education but very important for the operator of the volume knob, especially if you want to keep your acoustic cabinets healthy
A good valve amplifier and high sensitivity cabinets do not fall within this description.
With 38 watts in PP and 95 db sensitivity of the speakers, my ears ask for clemency !
But there is no audible distortion. So the measurements are relative to how we interpret them and what we are measuring.
 
offer you a good amount of headroom.

so that you never reach the clipping area.

Mod hat off.

Too bad our friend Ben doesn't realize this was a rather elementary question from a member looking for a nice easy to understand answer and therefore felt the need to join in and pontificate.

Once again.

Must have been those days at Bells Labs.

Ben, give it a rest would ya? Go pick on someone your own size. Your expertise is being wasted here.
 
It's about normal loudspeakers rather than subwoofers, but still you might find this thread interesting:

A Test. How much Voltage (power) do your speakers need?

For what it's worth, I have a two times 20 W amplifier with a clipping LED in my living room and used to have 86 dB at 1 W, 1 m loudspeakers connected to it (full-range electrostatic speakers in fact). The LED turns on for a second after a few microseconds of clipping, but that almost never happened during normal use.
 
Mod hat off.

Too bad our friend Ben doesn't realize this was a rather elementary question from a member looking for a nice easy to understand answer and therefore felt the need to join in and pontificate.

Once again.

Must have been those days at Bells Labs.

Ben, give it a rest would ya? Go pick on someone your own size. Your expertise is being wasted here.

I don't think your ridicule and abuse are appropriate.

Perhaps I was being dim-witted. Perhaps you can restate the simple question and I'll offer any reply that might advance the discussion.

B.
 
Why do I need that many watts?

Do you want it louder, deeper, or in a smaller box than your previous build? If so then you need more watts. Probably not 4000, though. Those Ultimax drivers are designed to hit their thermal and mechanical limits at the same time, somewhere in the neighborhood of 800 watts. If you had enough output at 250 watts the original amp may be just fine until you decide you want a bigger one. The iNukes were suggested because of bang for the buck, but you really do have to baby them or they blow up eventually. Using it with the limiters set at 800 watts would qualify.
 
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