It's not difficult, just hook them up with proper crossover more or less. Be aware that driving two different drivers with completely different (mainly mechanical) specs will create two different sounds, a timbrel change coloring the true sound. There were several speakers in the late 70's that used this approach and have for the most part been abandoned for good. Today we do know that this causes issue and can be measured so is not normally done unless drivers are the same.
Hi,
No.
FWIW the sensitivity specification of a driver is dB/2.83V/1m/2pi
space. That is 1W into 8ohm, 2W into 4ohm, 0.5W into 16 ohm.
This is the figure used in design software and for level matching.
Sometimes sensitivity is specified as dB/1W/1m/2pi. What
this means is the nominal impedance is taken ito account
and is 3dB lower for 4 ohms and 3dB higher for 16 ohms.
You can call this the nominal efficiency of a driver
but you don't use that figure in design software.
(Its the same as sensitivity for a nominal 8 ohm driver.)
Two identical drivers in series or parallel have identical
efficiency, +3dB over one driver, but the proper design
sensitivities are +6dB for parallel and same for series.
Note that this is all into 2pi (half) space. Into 4pi (full)
space you lose 6dB sensitivity and efficiency at low
frequencies. At higher frequencies as the radiation
moves to 2pi due to the baffle size, it moves up 6dB.
This is the so-called baffle step, that usually needs
some form of compensation, often not the full 6dB.
So take a typical 88dB 6.5" 8 ohm driver. In a two
way the sensitivity will be 84dB with 4dB of BSC,
(baffle step correction) with a 8 ohm impredance.
In a 2.5 way you usually get the full BSC of 6dB
the sensitivity will be 88dB, but 4 ohm in the bass.
rgds, sreten.
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Hi,
Extremely difficult. Try high passing any woofer at
60Hz, it's impedance peak simply won't let you.
What you need to do is split the box volume and
/or arrange suitable driver parameters, such that
both drivers are effectively used, and reach their
limits moreorless at the same time. It can get
very complicated to model, lots of options.
rgds, sreten.
Hello ...
Now for my example, assuming you had an amp that put out 100 watts at 4, 8 and 16 ohms, and a woofer that had an spl or whatever it called at 100 db 8 ohms at 1 metre with 1 watt
Now say we wire one speaker to the amp, its sensitivity will remain 100db/8 ohms/1 meter
Now say we wire 2 of the speakers in parallel making a 4 ohm load, I assume the sensitivity now rises to 103 db because a doubling of cone area at the same watts
Now say we wire 2 in series causing a 16 ohm load, I assume again that the spl now rises to 103 again because of the doubling of cone area,
Based on that does parallel and series sensitivity go by what the amp can out put at certain ohm loads....
Thanks
Did anyone notice that this thread was STARTED in 2008?
The above suggestion is in error. In Parallel, both speakers get the same voltage and have the same output, but combining them should give you a roughly +3db boost.
However, in Series, each speaker gets HALF the voltage, you get more output because of two speakers, but with each getting half the voltage, the output drops back. So it is +3 -3 = 0db. The output for two speakers is the same as the output for one speaker (more or less).
However, each speaker will consume half the power and have half the excursion. Typically given a boost in sound quality and low distortion.
If we assume this is ultimately a 3-way with a Midrange, then there are two ways to do this.
1.) At the lowest of the low frequencies, both bass drivers run in parallel. That would be a 3.5-way system.
2.) Build the equivalent of a 4-way system - Low-Bass, Mid-Bass, Midrange, tweeter.
I've considered doing something similar with a 10" and a 8". Using not the same size drivers is unconventional, but it can be done.
Now, I used 3-way and 4-way in my examples because I already had those graphics. The absents or presents of a Midrange is up to you.
Though I think the 60hz and 200hz crossovers are bit unrealistic. Though what the precises crossover would be would depend on the rest of your design.
In a 3-way, the Low-Bass crossover could be in the 100hz to 300hz range, and the Mid-Bass to Midrange crossover would likely be in the 500hz to 1000hz range, though 500hz and 800hz are common in a 3-way.
With a Parallel configuration you get more output but at the cost of lower impedance and higher current. Higher current means more heat in the amp.
In Series you get greater power handling, but less output.
Also, in a multi-way system, where each driver has its own individual selected range of frequencies, their impedance does not combine.
As an example, if the Low-Bass covers 0hz to 200hz, and the Mid-Bass covers 200hz to 800hz, those impedance are not combined. Each has the impedance of a single speaker in their Pass-Band.
In a 2.5-way or a 3.5-way the Low-Bass would cover, just as an example, 0hz to 200hz, and the Mid-Bass would cover 0hz to 800hz. So, both are in parallel between 0hz and 200hz with a combined parallel impedance of 4 ohms. Above 200hz, the speaker system would be 8 ohms.
So, to make any sense of this, we would not only need to know about the woofer, but the vision for the complete system.
Does he plan to overlap the speakers, or does he plan to give each bass driver its own personal frequency range to deal with?
The OP is saying that the speakers will be in Parallel or Series, that implies that they can only cover the same frequency range. That's not really good design.
So, if the Original Poster is still around, he would need to give us his overall vision for the full speakers system. Then we can evaluate the possibilities. But without that, he will get nothing but speculation about what we think his vision of the speaker system might be.
But to his basic question, 2 speakers in Parallel will have higher output but lower impedance. Two speakers in Series, will have the output of one speaker, but each speaker will have half the voltage and half the excursion boosting power handling and lowering distortion.
That said, as he stated it, I don't think this is a realistic design. Perhaps he has no design and was simply wondering about the possibility of combining two speakers, but my interpretation of what he described is unrealistic in a real speaker design.
Just a few thoughts.
Steve/bluewizard
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There is a difference between sensitivity and efficiency. Sensitivity does not change but power conversion changes (that is, efficiency) with how you connect drivers together.
In a series connection with 2 drivers of the same impedance.... efficiency remains the same. Power conversion to SPL is the same as a single driver but the dynamic range of the 2 driver combination has now doubled. With similar drivers of the same cone area (Sd) the two drivers in series have twice the surface area of a single driver but being in series the current (the motivating force) is only half of that for a single driver. So 2 x Sd (cone surface area) x 1/2 of I (current) = 1 x Sd x 1 x I (current) for a single driver. So the efficiency doesn't change thus the SPL doesn't change for a series combination over that of a single driver of the same make.
Of course the impedance does change and is now double for the series combination relation to that of a single driver, but, the series combination does preserve Xmax over that for the single driver. This is important if the loudspeaker is to be driven to high levels.
With the combination of parallel drivers, the Sd is doubled and the total current flowing via the both drivers combined is double that for a single driver. Consequently, 2 x Sd x 2 x I (current) is equal to 4 times that for a single driver. Now 4 times in efficiency equates to a 6 db increase in SPL but the overall impedance of the parallel combination is now halved which puts a greater load on the amplifier's output. In the parallel combination Xmax is not preserved but is used up with the greater efficiency provided by this combination.
C.M
Edit: This is an old thread !
In a series connection with 2 drivers of the same impedance.... efficiency remains the same. Power conversion to SPL is the same as a single driver but the dynamic range of the 2 driver combination has now doubled. With similar drivers of the same cone area (Sd) the two drivers in series have twice the surface area of a single driver but being in series the current (the motivating force) is only half of that for a single driver. So 2 x Sd (cone surface area) x 1/2 of I (current) = 1 x Sd x 1 x I (current) for a single driver. So the efficiency doesn't change thus the SPL doesn't change for a series combination over that of a single driver of the same make.
Of course the impedance does change and is now double for the series combination relation to that of a single driver, but, the series combination does preserve Xmax over that for the single driver. This is important if the loudspeaker is to be driven to high levels.
With the combination of parallel drivers, the Sd is doubled and the total current flowing via the both drivers combined is double that for a single driver. Consequently, 2 x Sd x 2 x I (current) is equal to 4 times that for a single driver. Now 4 times in efficiency equates to a 6 db increase in SPL but the overall impedance of the parallel combination is now halved which puts a greater load on the amplifier's output. In the parallel combination Xmax is not preserved but is used up with the greater efficiency provided by this combination.
C.M
Edit: This is an old thread !
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Interesting.
- WinISD still calculates for my 2 midranges in parallel with +3dB (I'd like to believe you 'cause I plan with +6dB lift in mind. If +3dB is the reality I have to re-think..)
- preserving Xmax: I thought series connection halves Xmax and parallel retains it (seen for 1 driver of 2, compared to 1 single driver). It should behave like light bulbs in series: half the light in series, while both at full light in parallel. Or I'm really misunderstanding something.
Old thread but there was still no final consent about it, everybody told their assumptions and I was just wondering like hmm, either half of the guys don't know physics or physics is cheating on us. I'm not an engineer, so I was hoping for a reliable statement but lots of people here seemed to make a final statement , fully contradicting to eachother.
That's why I google'd a bit and then it showed me this topic here, hey I'm registered anyway, let's ask again..
This shouldn't be that much of a rocket science I assume and if your +6dB theory is right, we can say WinISD's box simulation is wrong at that point, especially the SPL curves. They lift for 2 parallel speakers by 3dB only.
- WinISD still calculates for my 2 midranges in parallel with +3dB (I'd like to believe you 'cause I plan with +6dB lift in mind. If +3dB is the reality I have to re-think..)
- preserving Xmax: I thought series connection halves Xmax and parallel retains it (seen for 1 driver of 2, compared to 1 single driver). It should behave like light bulbs in series: half the light in series, while both at full light in parallel. Or I'm really misunderstanding something.
Old thread but there was still no final consent about it, everybody told their assumptions and I was just wondering like hmm, either half of the guys don't know physics or physics is cheating on us. I'm not an engineer, so I was hoping for a reliable statement but lots of people here seemed to make a final statement , fully contradicting to eachother.
That's why I google'd a bit and then it showed me this topic here, hey I'm registered anyway, let's ask again..
This shouldn't be that much of a rocket science I assume and if your +6dB theory is right, we can say WinISD's box simulation is wrong at that point, especially the SPL curves. They lift for 2 parallel speakers by 3dB only.
+3dB because you have input twice as much power to the pair of speakers.
The extra +3dB due to coupling ONLY applies where you have constructive interference, i.e. where the listener is in line with the interference peak/s AND the frequency is low enough that the two drivers can be considered to be coupled (close together).
The extra +3dB due to coupling ONLY applies where you have constructive interference, i.e. where the listener is in line with the interference peak/s AND the frequency is low enough that the two drivers can be considered to be coupled (close together).
1/4 to 1/2 wavelength apart loses the +3dB coupling effect.
1/4 wavelength of 125Hz is ~0.68m
Two 15" bass drivers sitting at 500mm Centre to Centre (C/C) will be coupled for the whole of their frequency range up to 125Hz.
Whereas the Mid Drivers operating at <2.5kHz have a 1/4wavelength of 34mm. Two Mid drivers in MTM format would need to have C/C <34mm to be considered coupled. Instead they are more likely to be 200mm C/C and for most of their frequency range they will beam with a narrow lobe where you are inline with the constructive interference. When you move out of that narrow lobe/beam the volume drops off rapidly.
1/4 wavelength of 125Hz is ~0.68m
Two 15" bass drivers sitting at 500mm Centre to Centre (C/C) will be coupled for the whole of their frequency range up to 125Hz.
Whereas the Mid Drivers operating at <2.5kHz have a 1/4wavelength of 34mm. Two Mid drivers in MTM format would need to have C/C <34mm to be considered coupled. Instead they are more likely to be 200mm C/C and for most of their frequency range they will beam with a narrow lobe where you are inline with the constructive interference. When you move out of that narrow lobe/beam the volume drops off rapidly.
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Wow. Good explanation. I think I'm better off then with a stronger 1-midrange solution matching the tweeter and woofer than with 2 or 4 smaller midranges.
How about power and excursion ?
According to this page click also in parallel there's a 50% drop in speaker power (each), halving the common impedance while draining 2x as much from the amp - and producing a +3dB lift (and another +3dB if acoustic coupling works). Correct ? Just asking this because this could be a way of power distribution among separate speakers (if needed).
In series they also play at half power (each) but there's no lift in SPL - some say at least.. (?) ..
How about power and excursion ?
According to this page click also in parallel there's a 50% drop in speaker power (each), halving the common impedance while draining 2x as much from the amp - and producing a +3dB lift (and another +3dB if acoustic coupling works). Correct ? Just asking this because this could be a way of power distribution among separate speakers (if needed).
In series they also play at half power (each) but there's no lift in SPL - some say at least.. (?) ..
Let's take a different approach: 2 drivers = double the cone size = double efficiency (which is acoustic/electric power). This normalized to power gives +3dB but normalized to voltage gives +6dB because power is proportional to voltage^2 . Connecting a second speaker to the original in parallel with leaving everything else as it was before, power doubles because I halved the impedance. At the end, double power + double efficiency = 4x acoustic power which is then +6dB lift.
True or false ?
True or false ?
Hello
I need to clarify these rules, I know how to wire in series and parallel like anyone would but I don't know how this affects sensitivity's
Now for my example, assuming you had an amp that put out 100 watts at 4, 8 and 16 ohms, and a woofer that had an spl or whatever it called at 100 db 8 ohms at 1 metre with 1 watt
Now say we wire one speaker to the amp, its sensitivity will remain 100db/8 ohms/1 meter
Now say we wire 2 of the speakers in parallel making a 4 ohm load, I assume the sensitivity now rises to 103 db because a doubling of cone area at the same watts
Now say we wire 2 in series causing a 16 ohm load, I assume again that the spl now rises to 103 again because of the doubling of cone area,
Based on that does parallel and series sensitivity go by what the amp can out put at certain ohm loads
Or give me a realistic exmaple
Thanks
May I suggest you grab a copy of XSim??
You can simulate this all for free. +3db is the theoretical boost, and is likely what you would get in a Anechoic Chamber. However, with pretty much every speaker there is some room boost. But, again, that applies to all speakers.
No that covers it.
I'm pretty sure there was consensus, though not 100%, but generally everyone seemed to agree on the basics.
This shouldn't be that much of a rocket science I assume and if your +6dB theory is right, we can say WinISD's box simulation is wrong at that point, especially the SPL curves. They lift for 2 parallel speakers by 3dB only.
WinISD is correct, as explained. Every time you double or half the power the output changes by 3dB. But other factors come into play. You can boost the bass tremendously by simply placing a speaker in the corner, but when you do that, it tends to muddy the Mid/High. So, there are trade offs to every design based on the priorities of the designer.
Steve/bluewizard
Perhaps a simpler way of looking at this is -
Efficiency is Power Out vs Power In, or perhaps, Energy Out vs Energy In. No 'engine' is 100% efficient. Your car engine is about 20%, that is about 20% of the Energy available in the fuel is made available from the actual engine. Speakers are the same, only about 20% of the Electrical Energy is converted to Acoustical Energy.
Sensitivity is about the acoustical output of a speaker relative to a fixed standard input. A fixed standard input is used so that all speaker can be fairly compared.
Though relative to Sensitivity, there is some controversy about where all speakers should get the same standard Voltage Signal, or the same standard Power signal. Since Amplifiers are really Voltage devices, I say they should be fed the same Voltage, but others disagree. However, that is a separate topic that has been discussed many times.
Steve/bluewizard
Hmm. Thank you for your time & explanation.
So what if I take a midrange and drive it with 1 watt-ish power or even with a different one, doesn't matter. I measure the SPL at let's say, 600 Hz, on axis, 1m distance. This will give me some kind of result, X dB. Now I connect another driver parallel with it, no MTM, no magic, just put onto the floor close to the first one - will I measure X+3 dB for this parallel connected 2-speaker set ?
Where I want to get is: for a passive box it's a good general rule that we're trying to use drivers of the same sensitivity, to avoid situations like using a 88dB midwoofer with a 94dB ribbon (just an example) without any correction (no L-Pad). This would cause a too bright sounding system. But when I take the same woofer 4 times (2 in series and these to parallel), I should gain some efficiency ("loudness") so I have a more balanced sound (made some SPL increase which is matching better to the tweeter). The only question is by how much and you say +3dB (anechoic room).
Same applies if I want to make correction by using 2 other types of woofers in parallel again which are in general a bit more sensitive than the original one.
The point again is: if there weren't this controversy you mentioned above, one could easily think about the needed increase in midwoofer SPL to match that tweeter and avoid a too bright sound. In this case if a +6dB theory could work, I could use more woofers in parallel to the tweeter and we're fine (except that I would take 16 ohm models to stay at 8 ohm - or 4x 8 ohm like written above, if size allows).
If the gain would be +3dB only, I would look for another woofer model, which has ~91dB basis and then build with these (in parallel) to get to the tweeter, and fully skip the 88dB ones.
I know in reality a lot more effects are coming into play but on paper at least it would be important to strive for a balanced perceived loudness (which translates to SPL if I would like to name it).
So what if I take a midrange and drive it with 1 watt-ish power or even with a different one, doesn't matter. I measure the SPL at let's say, 600 Hz, on axis, 1m distance. This will give me some kind of result, X dB. Now I connect another driver parallel with it, no MTM, no magic, just put onto the floor close to the first one - will I measure X+3 dB for this parallel connected 2-speaker set ?
Where I want to get is: for a passive box it's a good general rule that we're trying to use drivers of the same sensitivity, to avoid situations like using a 88dB midwoofer with a 94dB ribbon (just an example) without any correction (no L-Pad). This would cause a too bright sounding system. But when I take the same woofer 4 times (2 in series and these to parallel), I should gain some efficiency ("loudness") so I have a more balanced sound (made some SPL increase which is matching better to the tweeter). The only question is by how much
and you say +3dB (anechoic room). Same applies if I want to make correction by using 2 other types of woofers in parallel again which are in general a bit more sensitive than the original one.
The point again is: if there weren't this controversy you mentioned above, one could easily think about the needed increase in midwoofer SPL to match that tweeter and avoid a too bright sound. In this case if a +6dB theory could work, I could use more woofers in parallel to the tweeter and we're fine (except that I would take 16 ohm models to stay at 8 ohm - or 4x 8 ohm like written above, if size allows).
If the gain would be +3dB only, I would look for another woofer model, which has ~91dB basis and then build with these (in parallel) to get to the tweeter, and fully skip the 88dB ones.
I know in reality a lot more effects are coming into play but on paper at least it would be important to strive for a balanced perceived loudness (which translates to SPL if I would like to name it).
Btw I'm still wondering how the hell is this an issue at all, even if we take an anechoic chamber. Isn't there anybody who tried this small experiment of measuring sound pressure for 1 speaker driver and then connect a second one to it in parallel, leaving amp & volume settings the same.. ? I mean our ears don't know about Volts, Power or whatsoever. Irrespective of what power or voltage I feed 1 speaker with, AT THE SAME SETTINGS there should be a quite good measurable gain in pressure levels at a given frequency of either +3dB or +6dB, without knowing the math.
Brrrrr.. physics.
Brrrrr.. physics.
