That's 2 watts vs. 1 watt. 2nd line down is "Amplifier power of EACH loudspeaker" so each speaker gets 1 watt, 2 watts total.
Ah, I see what you mean. That calculator is indeed tricky. When you have two drivers, the sensitivity raises 3dB, like I explained earlier. So if you fill in two drivers you have to correct the sensitivity figure manually.
I don't think so.....LOL.
One speaker with 10W gives 100dB @ 10m
Two speakers each with 5W gives 103dB @ 10m over the frequency range defined by the cone, or mouth, separation.
Two speakers close coupled each with 10W gives 106dB @ 10m
double the power and you get +3dB.
double the mouth & cone area and you get +3dB.
double the power and double the mouth and cone area and you get +6dB.
Add second speaker to an amplifier and you do not get double the power. Some amplifiers will go into protective limiting, some will give 40% to 60% more power, some will give 60% to 80% more power, none will give 100% more power, none!
Two speakers each with 5W gives 103dB @ 10m over the frequency range defined by the cone, or mouth, separation.
Two speakers close coupled each with 10W gives 106dB @ 10m
double the power and you get +3dB.
double the mouth & cone area and you get +3dB.
double the power and double the mouth and cone area and you get +6dB.
Add second speaker to an amplifier and you do not get double the power. Some amplifiers will go into protective limiting, some will give 40% to 60% more power, some will give 60% to 80% more power, none will give 100% more power, none!
Not necessary. Just read their website more carefully. But I agree that they could have been more clear with their explanation.Can you email those guys with the calculator page and tell them they are wrong.....?
If you look to the equations involved one can find out that they are based on incoherent sources (uncorrelated sound sources). In other words, they are not acoustically coupled and each sound source (loudspeaker) plays a different sound signal. When you add two incoherent sound signals of the same sound levels the sum is +3dB, like the calculator shows.
Coherent sound signals (correlated sound sources) in phase and within the ¼ wavelength of the sound will acoustically couple. When you add two coherent sound signals of the same sound levels the sum is +6dB.
Quote from their website LINK :
Adding of two incoherent sound pressure levels or voltage levels:
Adding of two values of the same level give an increase of the total level of (+)3 dB.
This equation is used for electrical adding of incoherent signals,
and for the calculation of the energy level of two loudspeakers.
Adding of two coherent sound pressure levels or voltage levels:
Adding of two values of the same level give an increase of the total level of (+)6 dB.
This is obtained by feeding two side-by-side loudspeakers with the same signal.
ok , so in the case of the SS15's
what is the best way to stack them
suppose you have 8 ss15's
does you lay them in the floor in line ( horizontally )
standing in front of them cab1 will be your leftmost and cab 8 your rightmost
or
4 cabs in the floor side to side and another row in top of them
or if you have just 4
4 in line in the floor side to side or 2 in the floor and 2 in top of them
also... i heard that some guys raise them with "mini" stage structures
the put like some kind of table 5 to 6 feet from the floor and put the subs there and the rest of the setup in top of the subs
does raising the height of the cabs affect for good or worse the spl's ?
what is the best way to stack them
suppose you have 8 ss15's
does you lay them in the floor in line ( horizontally )
standing in front of them cab1 will be your leftmost and cab 8 your rightmost
or
4 cabs in the floor side to side and another row in top of them
or if you have just 4
4 in line in the floor side to side or 2 in the floor and 2 in top of them
also... i heard that some guys raise them with "mini" stage structures
the put like some kind of table 5 to 6 feet from the floor and put the subs there and the rest of the setup in top of the subs
does raising the height of the cabs affect for good or worse the spl's ?
That depends on surrounding structures. As a general idea, moving away from walls and boundaries decrease levels, but without knowing for sure what the surroundings are, it's difficult to tell if it'd be a positive or negative change as far as linearity is concerned.
I'll throw this into the mix:
Voltage sensitivity is what gets lost in most of the how loud the speakers become in comparisons people make.
Any given loudspeaker motor has a finite voltage sensitivity. Adding two motors together in any configuration does not change that sensitivity.
A 50% drop in the lowest impedance point does not give you double the power available over the speakers usable bandwidth as Andrew pointed out. A care examination of the impedance of the boxes in question will show you that where the tuning points are they are indeed very high in impedance. Therefore where the lowest and highest tuning points are placed is where it is most difficult for a normal amplifier to pour on the watts.
Remember that amplifiers are actually voltage sources. Given a steady state input signal an amplifier attempts to drive an equal amount of voltage into a varying impedance by fluctuating the amount of current. The available current has limitations based on the power supplies rating and a number of other factors.
Mutual coupling between drivers does change the expressed output level for a certain bandwidth, not across the board.
And a stack of boxes can help in more ways than one thinks. Take a look at Arts measurements with the wings on the sides of the boxes. the launch of the wavefront off of a larger baffle increases the efficiency of the system.
Voltage sensitivity is what gets lost in most of the how loud the speakers become in comparisons people make.
Any given loudspeaker motor has a finite voltage sensitivity. Adding two motors together in any configuration does not change that sensitivity.
A 50% drop in the lowest impedance point does not give you double the power available over the speakers usable bandwidth as Andrew pointed out. A care examination of the impedance of the boxes in question will show you that where the tuning points are they are indeed very high in impedance. Therefore where the lowest and highest tuning points are placed is where it is most difficult for a normal amplifier to pour on the watts.
Remember that amplifiers are actually voltage sources. Given a steady state input signal an amplifier attempts to drive an equal amount of voltage into a varying impedance by fluctuating the amount of current. The available current has limitations based on the power supplies rating and a number of other factors.
Mutual coupling between drivers does change the expressed output level for a certain bandwidth, not across the board.
And a stack of boxes can help in more ways than one thinks. Take a look at Arts measurements with the wings on the sides of the boxes. the launch of the wavefront off of a larger baffle increases the efficiency of the system.
Thinking about how to stack multiple speakers can be done from two directions.
Line array for long distance listening:
stack the speaker mouths in a tall column to simulate a line array and the "sound" will travel farther out into the distance due to the different "line array" drop off of level with distance.
Wide bandwidth for closer listening:
where distance is less important there is a small gain in LF bandwidth in grouping all the mouths together so that the corner to corner extremities of the mouth group is as short as possible.
Line array for long distance listening:
stack the speaker mouths in a tall column to simulate a line array and the "sound" will travel farther out into the distance due to the different "line array" drop off of level with distance.
Wide bandwidth for closer listening:
where distance is less important there is a small gain in LF bandwidth in grouping all the mouths together so that the corner to corner extremities of the mouth group is as short as possible.
I was just pulling your chain a little bit about this:
"Add second speaker to an amplifier and you do not get double the power. Some amplifiers will go into protective limiting, some will give 40% to 60% more power, some will give 60% to 80% more power, none will give 100% more power, none!"
Krell has been making amplifiers that double perfectly into halving impedance for a long while now, unless that's not what you're talking about.
I disagree.
As far as I know all Krell amplifiers do not have an infinite damping factor. This indicates that no Krell amplifier has zero output impedance.
In addition no unregulated PSU has zero output impedance.
Combine these two effects and you will find that all amplifiers do not double their output current when the load value is halved. None.
I agree with you, but for an amp like the SpeakerPower SP1-4000 which is rated (and delivers) 1300W/ at 8 ohms, 2400W/4, 4000W/at 2 ohms, the difference between a perfect voltage source and that amp is only about 1 dB going from an 8 ohm to a 2 ohm load.
That said, there are many amps on the market that have so much current limiting they actually put out less power at 2 ohms than 4 ohms.
As usual, testing the amp's output SPL with the actual speaker load is always important, specs often don't tell the real story of what will happen with low frequency signals.
Art
2400W ref 1300W is a 0.7dB reduction when load value is halved. That is a very good figure.
4000W ref 2400W is a 1.6dB reduction when load value is halved. That is a mediocre figure.
The total reduction is 2.3dB when the load is quartered. For a 4ohms rated amplifier that is a very good figure. I would be more than happy with that "stiffness" of supply.
But I would need 1r0 data to assess if this amplifier is rated for 2ohms use.
Yes, I need to see performance into lower resistances than nominal speaker load to complete this part of the assessment.
But for this example where 1.6dB has been lost just going down to 2r0, I would put my experience forward and suggest this amplifier will lose more than 2.5dB when trying to drive 1r0. That for me would be a failed 2ohms capable amplifier specification.
4000W ref 2400W is a 1.6dB reduction when load value is halved. That is a mediocre figure.
The total reduction is 2.3dB when the load is quartered. For a 4ohms rated amplifier that is a very good figure. I would be more than happy with that "stiffness" of supply.
But I would need 1r0 data to assess if this amplifier is rated for 2ohms use.
Yes, I need to see performance into lower resistances than nominal speaker load to complete this part of the assessment.
But for this example where 1.6dB has been lost just going down to 2r0, I would put my experience forward and suggest this amplifier will lose more than 2.5dB when trying to drive 1r0. That for me would be a failed 2ohms capable amplifier specification.
Although the discussion is on doubling of P.A. amplifier power into every halving of load impedance, just wanted to say that Elektor had many years ago published 'A Medium Power A.F. Amplifier' by T.Giffard which doubled power down to 2 ohms. I repeat, it was a 'medium power' amplifier.
So to say, no amplifier can do that is taking the generalization a little too far. It can be done upto a certain power, but perhaps, practically impossible for powers involved in P.A.
So to say, no amplifier can do that is taking the generalization a little too far. It can be done upto a certain power, but perhaps, practically impossible for powers involved in P.A.
It quickly becomes a very expensive enterprise to put together an amplifier that is a true voltage source. Either very large transformers or very robust switching systems, both limited to what can be drawn off of the wall outlets.
It is not an engineering impossibility.
As for the Speaker Power amplifier.
About 3 years ago I did an exhaustive study on available plate amplifiers for a client. At least then Speaker Power was using ICE modules. They were supposed to be changing over to Pascal modules. I don't know that for a fact by the way.
Pascal I have used extensively.
Really good amplifiers, but they do not double power down to 2 ohms.
Just to continue being difficult on this issue because I'm a little bored, here's a snip from an old KSA-250 review. Really old, but still fun.
"Looking at the KSA-250's maximum output power into varying impedances (see Sidebar "Class-A?") with one channel driven with a 1kHz probe signal (fig.5, which plots THD+Noise vs output power), we can see it clips (1% THD) at 325W into 8 ohms (25.1dBW), at 635W into 4 ohms (25dBW), and at over 1000W into 2 ohms (actually 1066W at 0.97% THD, or 24.3dBW). When driving 1 ohm, the KSA clipped at 1548W (22.9dBW). This is approaching perfect voltage-source behavior, and could be expected to be closer to the ideal of a doubling of power with each halving of impedance if the AC line voltage were held constant. The AC line voltage sagged during these tests to 116V (8 ohm testing), 114V (4 ohm testing), 112V (2 ohm testing), and 106V (1 ohm testing), from 117V at idle. All maximum power output measurements exceeded Krell's specifications except the 1 ohm measurement, which is a result of the line voltage dropping so low. With a regulated AC voltage, the KSA-250 could probably be expected to put out 2kW into 1 ohm. Although Krell specifies a 4kW output rating in 0.5 ohms, I didn't have a half-ohm resistor that would handle such power."
It would appear that if you're going to do testing on an amplifier like this, you should probably have a 0-0 gauge mains cable and be less than 50 feet from the power substation.