https://store.miscospeakers.com/6-5...MH*MTcwMTMxNjI5My4zLjEuMTcwMTMxNjMwMC4wLjAuMA..
A pair of these in parallel would be really nice.
A pair of these in parallel would be really nice.
Wow these are really cool! Great find!
The sensitivity is 85db though, so I would have to probably run more power to them. Definitely writing the link down though I like these lol
The sensitivity is 85db though, so I would have to probably run more power to them. Definitely writing the link down though I like these lol
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@BKr0n, don't mistake sensitivity with efficiency.
Take a single woofer as our baseline. We'll use an infinite baffle to avoid complicating the situation with changes in the box loading. We'll use a fixed voltage from the amp - no touching the volume knob here!
Add a 2nd, identical, woofer in series. SPL stays the same, but current & power drop 50%, because the impedance doubles. Same SPL at the same voltage = same sensitivity. Because power is only half, however, the 2nd woofer provides a 3dB efficiency improvement.
Now, change the woofers' wiring to parallel. Impedance becomes 1/4 the series connection's (half the baseline's), so current & power increase by 4x (double the baseline). 6dB more SPL at the same voltage = 6dB higher sensitivity. Compared to the series connection, the efficiency does not change, because that extra 6dB SPL requires 6dB more power.
Take a single woofer as our baseline. We'll use an infinite baffle to avoid complicating the situation with changes in the box loading. We'll use a fixed voltage from the amp - no touching the volume knob here!
Add a 2nd, identical, woofer in series. SPL stays the same, but current & power drop 50%, because the impedance doubles. Same SPL at the same voltage = same sensitivity. Because power is only half, however, the 2nd woofer provides a 3dB efficiency improvement.
Now, change the woofers' wiring to parallel. Impedance becomes 1/4 the series connection's (half the baseline's), so current & power increase by 4x (double the baseline). 6dB more SPL at the same voltage = 6dB higher sensitivity. Compared to the series connection, the efficiency does not change, because that extra 6dB SPL requires 6dB more power.
Thank you for that. It seems I was mixing the two up. So in the case of a Linkwitz Transform, would that be more related to efficiency or sensitivity? Also, is the overarching goal for flat response more related to one or the other? Or is it both?
I suggest taking sensitivity data from a microphone, not from paper work. Or at least use WinISD or Basta!, that calculate sensitivity from the TSP and thus regard Hoffmann’s law, as opposed to bespoke paper.
It might come in handy to spec required bandwidth (low end mainly) and max SPL required. People here could assist on it with sim apps, but we have to have a clear design goal.
It might come in handy to spec required bandwidth (low end mainly) and max SPL required. People here could assist on it with sim apps, but we have to have a clear design goal.
Not quite correct, this. Coherent identical sources add up to +6dB. Radiation impedance is a funny thing.
No, actually two identical and coherent sources (loudspeaker units) closely spaced will double the sound pressure level at some distance. So +6dB with the same current through each of the two voice coils as with one coil (in parallel the total current doubles).
In series the current halves, (Impedance doubles) but since both sources still are coherent, half that total current will lead to the same SPL as that of one source. That is to say, as long as you can argue sources are coherent, which likely is the case at low frequencies with wavelengths being bigger than the speaker system as a whole.
That is why I mentioned radiation impedance. Quite basic acoustics btw.
In series the current halves, (Impedance doubles) but since both sources still are coherent, half that total current will lead to the same SPL as that of one source. That is to say, as long as you can argue sources are coherent, which likely is the case at low frequencies with wavelengths being bigger than the speaker system as a whole.
That is why I mentioned radiation impedance. Quite basic acoustics btw.
ie 3dB
2 drivers run in parallel give 6 dB increase. +3dB from having 2 drivers and 3dB due to the halving of the impedance.
2 drivers run in series give0 dB increase. +3dB from having 2 drivers and -3dB due to the doubling of the impedance.
dave
Both or neither, depending how you look at it, I guess. Whatever EQ you run, the speaker/amp combination needs to be able to reach the SPL you require. There are WAY too many variables to tie that down to only one.
E.G., put 4x E150HEs in 20L & connect in series, and the amp probably clips at its maximum voltage before approaching any current/power limits. Change to parallel, and it's probably the other way around. Swap to 2S2P in a 200L box, and the woofers probably bottom before the amp gives up. Etc.
Spend an hour in VituixCAD's enclosure tool. Try different #s of drivers with different wiring. Change Vb & BR tuning frequency (watch the max-SPL line here!). Play with EQ options. Most of the time, you can put the cursor over a parameter, then watch the graphs while spinning the mouse wheel. That's going to help you understand the interactions a LOT better than anything I can write.
Same answer.
@markbakk, while I posted very late last night, I can't understand what detail(s) you disagree with. We (all) seem to be posting in circles, claiming the same differences between series/parallel & sensitivity/efficiency. If you disagree, that's fine, but please explain why.
Sound pressure level is a 20log function, whereas sound power level is a 10log. So doubling peff/p0 gives you +6,02 dB. I like the acoustic approach.
Put otherwise, why would halving the impedance lead to more SPL with a voltage source? Because it’s the current that matters.
Put otherwise, why would halving the impedance lead to more SPL with a voltage source? Because it’s the current that matters.
Halving impedance leads to more SPL with a voltage source, because if the voltage stays constant into a lower impedance then current necessarily increases. Same voltage but double the current leads to a doubling of power, which is 10log10(2) = 3dB more output. Then the benefits of improved radiation impedance comes on top of this, yielding 6dB increase in total.
The loudspeaker system has in other words become 3dB (or 100%) more efficient, and 6dB more voltage sensitive.
If the drivers are connected in series rather than parallel to each other, then impedance doubles, which means current halves. This way we lose 3dB sensitivity, but gain 3dB from improved radiation impedance. The end result is a system that has become 3dB more efficient, but with equal voltage sensitivity as the single driver case.
The loudspeaker system has in other words become 3dB (or 100%) more efficient, and 6dB more voltage sensitive.
If the drivers are connected in series rather than parallel to each other, then impedance doubles, which means current halves. This way we lose 3dB sensitivity, but gain 3dB from improved radiation impedance. The end result is a system that has become 3dB more efficient, but with equal voltage sensitivity as the single driver case.
Lotsa good stuff here... still don't know what driver I'm using lmao. One thing I've noticed as a constant theme in DIY audio is the more questions you answer, the more questions crop up. 
Hopefully this adds some clarity rather than confusion. I understand what @markbakk and @planet10 are saying, and I think perhaps they are talking past each other.
The simple case of 2 drivers in series, close enough to be coherent, there is a + 3 dB increase in efficiency because the surface area has doubled. The voltage seen by each driver is reduced by half. The net result is no change in sensitivity, but + 3 dB in efficiency.
While the end result numerically is not wrong, it is eminent we distinguish sound power from sound pressure. You cannot add 3dB SPW and 3dB SPL, just like you cannot add Volts and Watts. Our perception of sound is all sound pressure, so let's stick to SPL. Sound power isn't that relevant in our 'business'.
If you do the acoustic math, you will see that the SPL summing is both position and frequency dependent. So it is not always +6 or even +3dB. If you had true point sources spaced apart, even minus infinity dB would be possible at a given position and a given frequency.
The right driver to fit in a smaller box and go deep is possible
the tradeoff is low sensitivity.
Passive crossover be more a issue.
If system is active, your just relying on the gain
your able to add. none the less will make
a low sensitivity woofer / sub work.
the tradeoff is low sensitivity.
Passive crossover be more a issue.
If system is active, your just relying on the gain
your able to add. none the less will make
a low sensitivity woofer / sub work.
At no point did I do this. I didn't even talk about sound power, only electrical power. All the dB figures are in dB SPL, but the source of the sound pressure increase is two distinct phenomena: increase in electrical power fed to the speaker (equivalent to a 10log10(2)=3dB increase in SPL) and an increase in the radiation impedance (equivalent to a 3dB increase in SPL under the assumption that the drivers are coherently summing).
The increase in dB SPL is 2x, while the increase in sound power would be 4x in this case.
If we instead look away from the passive case of connecting a two woofers in parallel or series, let's look at two subwoofers closely spaced together, each with their own amplifier that puts out 2.83Vrms to the driver (for a nominal 1W). The output of the two subwoofers together will be 6dB SPL louder than of a single one. 3dB of this is is the improved radiation impedance, and 3dB of this is because the input power has effectively doubled, as both subs are now receiving 1W of power (again, I'm not talking about sound power). If you fed the drivers 1W in total, the end result would be 3dB more output compared to feeding 1W to a single driver.
It is remarkably easy to test this yourself in simulation software (or in real life, if you want to make it more work).
Yes, thanks. A table's definitely better than paragraphs of text here. If I'd only realized how much debate would follow...
This looks helpful. Faital Pro designed speakers that traded high efficiency for low frequency extension. Choose the driver sizes you're interested in and see what efficiency/LF extension suits your needs the best.
https://faitalpro.com/en/products/LF_Loudspeakers/
https://faitalpro.com/en/products/LF_Loudspeakers/