But you can't get a Faital with Fs below 60Hz until you go to 8".
Looks like Loudspeaker Database was updated recently, and it's a big upgrade. Lots of criteria to filter the list down to something manageable! The main drawbacks are that they don't have every driver (e.g., no Epiques yet) & you'll need to have some feeling for which criteria to prioritize. Seems that OP is still wrapping his head around that second part. @BKr0n, start with diameter & Vd.
Edit: And you can do the same with VituixCAD's enclosure tool, of course. That has a pretty broad database.
Looks like Loudspeaker Database was updated recently, and it's a big upgrade. Lots of criteria to filter the list down to something manageable! The main drawbacks are that they don't have every driver (e.g., no Epiques yet) & you'll need to have some feeling for which criteria to prioritize. Seems that OP is still wrapping his head around that second part. @BKr0n, start with diameter & Vd.
Edit: And you can do the same with VituixCAD's enclosure tool, of course. That has a pretty broad database.
I have been shuffling through that. I'll admit I still need to master vituixcad before I can reliably use it. It's a lot to take in, but there's help documents everywhere so I should be able to wrap my head around it sooner than later
Actually this discussion has me asking another question: Where do PRs fit into all of this in terms of sensitivity/efficiency?
You still are adding power and pressure.
10log and (sound pressure or electrical) level contradict. Electrically and acoustically. I’ll try one more time, at the risk of being pushy.
Two drivers in series compared to one. We will assume far field conditions, I.e. the sound source is small compared to the measuring distance. I will not touch the complicated subject of radiation impedance here, which in itself is a derivation.
The voltage and current per driver halve. Each driver at itself will generate a sound pressure at the reference point that is half that of the one driver (-6dB SPL) at reference point. Why? Because if current halves, cone movement (speed) halves. Which in turn leads to said -6dB (far field).
Now we have two coherent drivers. Coherent here means that, seen from the reference point, sources generate the same signal, just as strong and in phase. Sound pressure at the reference point doubles (simple gas laws), thus bring the level up with +6dB (=20*log(2*peff/peff), I skip the p0).
So instead of -3dB and +3dB SPL we get -6dB and +6dB. For the parallel drivers: each driver gets the original current, so only the last half applies and leads to +6dB SPL at reference point.
Long story short: in acoustic calculations, don’t use power as magnitude if you don’t have to. Power in acoustics is a rather dramatic phenomenon (hard to measure mainly) and not very relevant for us. Jim has kindly put it together in his cheat sheet, but if you go back to the acoustic basics, it’s really quite simple.
I am converting electrical power fed to the speaker to sound pressure and then adding them. A doubling in electrical power leads to a 20log10(sqrt(2)) increase in pressure from the speaker, or 3dB. You can state it this way if you want to stick to vector quantities. More commonly this is just referred to as 10log10(p1/p0). A doubling of electrical power leads to a doubling of sound power and a sqrt(2) multiplication of pressure. You can convert between the two. I feed a 85dB/W@1m speaker with 10W, what is the resulting sound pressure? 85 + 10log10(10) = 95dB. These 95dB are sound pressure, not sound power.
A quadrupling of input power leads to a doubling of sound pressure output. Converting between the two is simple. You can also convert between sound power and sound pressure, but that operation becomes a bit more complex. Sengpielaudio has a writeup and calculator specifically for this.
The voltage per driver and current in the circuit halve, which leads to a 2x drop in input power (the input voltage for the circuit as a whole remains the same, but the current is now halved). A 2x drop in input power leads to -3dB SPL output. It's true that two independent but coherently summing sound sources add up to +6dB SPL, but in these cases you have to realize that the energy/power driving the oscillation of these sound sources has also doubled.
In your above case that means that each driver is playing -6dB (it receives half the voltage and half the current, or 1/4th of the power). Then you double the power (+3dB) because there are two speakers with each receiving 1/4th of the original power, which comes out to a halving in total power (1/4 + 1/4). The radiation impedance improvement is then responsible for the remaining 3dB increase.
Another example: if two people equidistant from me strike a drum in the exact same way at the exact same time, the sound pressure will be +6dB compared to that of a single drum, where 3dB of increase comes from the improved radiation impedance and 3dB comes from the fact that "double the energy/power" has been put into the system (two people striking two drums instead of one person striking one drum).
No worries. I feel terribly combative when I get into arguments like this too. Perhaps we should just let it rest, seeing as this discussion has no practical implications (we both agree what the end result is, just not how we get there...) and it's not particularly relevant to this thread (sorry to the thread starter!)
