When two drivers are used over the same frequency range their efficiency goes up 3db, but in a 2.5 way 2 drivers are being used for low end but 1 is for mids, does this mean that the speaker would have 88db from 400Hz up but have 91db 400Hz and below... does this mean padding is needed? please explain this to me becuase i really dont get 2.5ways.
the output does not rise below the .5 cutoff frequency. That is the point of 2.5 ways. The .5 compensates for the "baffle step" - the drop in response when the speaker transitions from 2 pi to 4 pi radiation.
You may end up padding the .5 if your room setup balances out the baffle step loss, but if your speakers are away from teh walls it is unlikely to be much padding, if any.
For planning purposes, treat your system sensitivity as a single woofer, minus a bit for losses in the crossover.
Did I get this one right, Sreten? 😉
You may end up padding the .5 if your room setup balances out the baffle step loss, but if your speakers are away from teh walls it is unlikely to be much padding, if any.
For planning purposes, treat your system sensitivity as a single woofer, minus a bit for losses in the crossover.
Did I get this one right, Sreten? 😉
michael said:
When two drivers are used in paralell output goes up 6dB but
efficiency only goes up 3dB as 3dB more current is being drawn.
You need to understand Baffle Step Compensation. In simple
2 ways that only account for crossover, or fullrange drivers,
output rises 6db due to as said to the change from driving a
spherical field to a hemispherical field.
The transition frequency range is dependent on the baffle width.
Full baffle step compensation can be achieved by rolling in the
extra bass unit at the transition frequency with a 1st order filter,
the expected fall of 6dB output is cancelled by the baffle step rise.
The only disadvantage of doing a 2.5 way speaker like
this is you can only have full baffle step compensation.
If its done in the crossover network with an EQ circuit
you can have partial step compensation or none at all,
for use near walls and near corners respectively.
Lots of bad designs have no BSC at all.
http://sound.westhost.com/bafflestep.htm
🙂 sreten.
Re: Re: 2.5 way efficiency
This is kind of a confusing way of saying it. And not completely accurate.
By adding a 2nd driver you double the sensitivity (ie 3dB).
The potentially different output power of the amplifier into half (wired in parallel) or double (series) the impedance also affects output.
A "perfect" solid state amp (not completely attainable in practice) would have double the power output into half the impedance giving a gain of 3 dB -- conversly it would put out half the power into double the impedance and would put out 3 dB less power.
So you get 3 dB with the 2nd driver & any other is dependent on your amp. An article on Baffle Step is in the Wiki.
dave
sreten said:
This is kind of a confusing way of saying it. And not completely accurate.
By adding a 2nd driver you double the sensitivity (ie 3dB).
The potentially different output power of the amplifier into half (wired in parallel) or double (series) the impedance also affects output.
A "perfect" solid state amp (not completely attainable in practice) would have double the power output into half the impedance giving a gain of 3 dB -- conversly it would put out half the power into double the impedance and would put out 3 dB less power.
So you get 3 dB with the 2nd driver & any other is dependent on your amp. An article on Baffle Step is in the Wiki.
dave
Sorry but it is entirely accurate.
I only put it this way because the original post said :
Which is true, but not the relevant issue / parameter.
Two drivers in parallel :
voltage sensitivity (dB/V) goes up 6dB.
Impedance is halved.
Efficiency is doubled.
Two drivers in series :
voltage sensitivity (dB/V) stays the same.
Impedance is doubled.
Efficiency is doubled.
Sorry but the amplifier does not affect the above at all.
Note that when matching drivers, e.g. tweeter to midrange,
with different impedances, its the voltage sensitivity that
counts. dB/W doesn't. dB at 2.83V does (1W 8R).
🙂 sreten.
in my limited opnion i never use the lower impedance as a sign of increased efficiency on the speakers side, just look at the speakers efficiency and how much power the amp can deliver at the speakers impedance, not unrealistically double it...
The other "side effect" of using a lower impeadance driver is often increased distortion (from the amp). At least that is what I have been led to believe 🙂
Tony.
Tony.
If you compare a MTM d'Appolito configuration (2 way),
to a 2.5 way of doing it (MTM or TMM) the amplifier
issues you are all bringing up are just not relevant.
Adding a extra driver to a MT is a completely different issue.
Don't shoot the messenger ..........
🙂 sreten.
to a 2.5 way of doing it (MTM or TMM) the amplifier
issues you are all bringing up are just not relevant.
Adding a extra driver to a MT is a completely different issue.
Don't shoot the messenger ..........
🙂 sreten.
In the bass the same.
If the 2 way has full BSC very similar in the midrange too.
Efficiencies and voltage sensistivities will be the same too.
🙂 sreten.
If the 2 way has full BSC very similar in the midrange too.
Efficiencies and voltage sensistivities will be the same too.
🙂 sreten.
Our ears do not hear voltage directly. They hear Power, which is a function of the voltage into an impedance, therefore power sensitivity of the system is the final relevant mater. Thinking in terms of voltage sensitivity can lead to all sorts of confusion. For one thing not all amplifiers are constant voltage source. Valve amps lean toward constant current source & with impedance matching transformers to allow matching of output impedance of amp to load impedance to deliver constant power. Power here is the issue, & voltage is merely a part of it's equation.
Acoustic sensitivity mimics electric power sensitivity ( + factored efficiency quotient).
Electric power = V^2/R
1 x 8 ohm speaker driven from 2.83v = 1 watt
2 x same speaker in parallel = 4 ohm
4 ohm driven by same 2.83v = 2 watt
Increased power output from same voltage =
2/1 log 10 = 3dB.
Increased voltage sensitivity (if you must) = +3dB but the power sensitivity stays the same & will stay the same no matter how many speakers are connected in parallel or series.
2 speakers in series would yield -3dB change in voltage sensitivity & as stated, power sensitivity remains the same.
Yes voltage sensitivity changes with multiple speakers in different series/parallel combinations but is merely a function of the impedance change this poses to the amplifier
Acoustic sensitivity mimics electric power sensitivity ( + factored efficiency quotient).
Electric power = V^2/R
1 x 8 ohm speaker driven from 2.83v = 1 watt
2 x same speaker in parallel = 4 ohm
4 ohm driven by same 2.83v = 2 watt
Increased power output from same voltage =
2/1 log 10 = 3dB.
Increased voltage sensitivity (if you must) = +3dB but the power sensitivity stays the same & will stay the same no matter how many speakers are connected in parallel or series.
2 speakers in series would yield -3dB change in voltage sensitivity & as stated, power sensitivity remains the same.
Yes voltage sensitivity changes with multiple speakers in different series/parallel combinations but is merely a function of the impedance change this poses to the amplifier
Stephen D
Simply put, you do not understand acoustics issues,
only electrical issues.
2.5 ways work in the manner I describe based on the
principles as described.
According to your version of reality they simply wouldn't
work, so how come reputable manufacturers make them ?
(and horn loading wouldn't work either)
eggs and suck come to mind......
😉 sreten.
Simply put, you do not understand acoustics issues,
only electrical issues.
2.5 ways work in the manner I describe based on the
principles as described.
According to your version of reality they simply wouldn't
work, so how come reputable manufacturers make them ?
(and horn loading wouldn't work either)
eggs and suck come to mind......
😉 sreten.
Stephen D
On the contrary.
The principals I've stated above are in perfect compliance with acoustic principle & though I'm not all that well acquainted with 2.5 I don't think as I understand it contradicts it. It is you who seem to not understand acoustic or electric principal on this issue. You should surely know that horn loading increases Power efficiency by better marching the acoustic air load (impedance) to the drivers drive impedance. It is in essence an acoustic transformer. The equivalent effect in electronics would be the proper matching of transformer output impedance of a valve amp to the speaker load. Try driving a speaker directly from the output of the valves without a transformer in line & see how much power you get out. There is no acoustic transforming impedance matching involved with multiple speakers though I suppose there is a certain amount of baffle effect which is frequency dependant.
Can you point to one principle of the physics, computation/statement/conclusion in my previous post that is in error?? If so how should it be corrected? I have an open mind.
Gotta run, I'm late for work.!
How do you like your eggs....?
😉
On the contrary.
The principals I've stated above are in perfect compliance with acoustic principle & though I'm not all that well acquainted with 2.5 I don't think as I understand it contradicts it. It is you who seem to not understand acoustic or electric principal on this issue. You should surely know that horn loading increases Power efficiency by better marching the acoustic air load (impedance) to the drivers drive impedance. It is in essence an acoustic transformer. The equivalent effect in electronics would be the proper matching of transformer output impedance of a valve amp to the speaker load. Try driving a speaker directly from the output of the valves without a transformer in line & see how much power you get out. There is no acoustic transforming impedance matching involved with multiple speakers though I suppose there is a certain amount of baffle effect which is frequency dependant.
Can you point to one principle of the physics, computation/statement/conclusion in my previous post that is in error?? If so how should it be corrected? I have an open mind.
Gotta run, I'm late for work.!
How do you like your eggs....?
😉
Ever wondered why guitarists like 4 x12's ?
(series/parallel wired, same driver assumed)
Even though they can't get a single watt more
out of their amplifier compared to a 1x12 ?
Two reasons :
1)
The acoustic efficiency of a 4x12 is 6db higher than a 1x12.
this is due to the 4 drivers coupling to the air load in parallel,
consequently they each encounter 1/4 of the 1x12 airload,
each thus encounters 4 x times the acoustic impedance.
The improved impedance matching causes the 6dB increase.
2)
The baffle step occurs an octave lower as its twice as wide.
So the 4x12 sounds richer in balance than the 1x12.
So their 100w Marshall with a 1x12 sounds like a 400w
Marshall with the 4 x 12, and with a richer sound.
Lets consider a 100w-1x12 versus 4x(100w-4x12's.)
Just on power the difference is 6dB.
On SPL the difference is 12dB equivalent to 1.6Kw. Baffle step is
now barely an issue (for guitarists) being two octaves lower,
the sound is full, the bass range being 6dB higher than the 1x12.
So the bass range is improved by 18dB, equivalent to 6.4kW !
🙂 sreten.
(series/parallel wired, same driver assumed)
Even though they can't get a single watt more
out of their amplifier compared to a 1x12 ?
Two reasons :
1)
The acoustic efficiency of a 4x12 is 6db higher than a 1x12.
this is due to the 4 drivers coupling to the air load in parallel,
consequently they each encounter 1/4 of the 1x12 airload,
each thus encounters 4 x times the acoustic impedance.
The improved impedance matching causes the 6dB increase.
2)
The baffle step occurs an octave lower as its twice as wide.
So the 4x12 sounds richer in balance than the 1x12.
So their 100w Marshall with a 1x12 sounds like a 400w
Marshall with the 4 x 12, and with a richer sound.
Lets consider a 100w-1x12 versus 4x(100w-4x12's.)
Just on power the difference is 6dB.
On SPL the difference is 12dB equivalent to 1.6Kw. Baffle step is
now barely an issue (for guitarists) being two octaves lower,
the sound is full, the bass range being 6dB higher than the 1x12.
So the bass range is improved by 18dB, equivalent to 6.4kW !
🙂 sreten.
stephen & sreten:
I think you are both right, in your own way!
If you keep the impedance the same, the voltage sensitivity gets 3 dB more with driver doubling (as long as coupling of all the drivers within the wavelength is still possible off course).
So with the guitar amp: 1x 12"@8 ohms, or four 12"@8ohms (ser. ser. par.) is 6 dB more voltage sensitivity.
Compared to the 1x12", in the 4x12" cabin. each driver gets 1/4 of the power (same voltage @8ohms) wich is the same as a -6 dB output for each driver (compared to 1x 12"). So the powersensitivity per driver has not changed, but for the sum it has changed....
In my view this means that the benefit of multiple drivers is because of the doubling of radiating surfaces or sources....
And about the 2.5 way: I dont know exactly about the baffle step correction compensation, but if you adjust the series inductor (for the bottom bass-driver) to the baffle size it must work, very interesting issue....
But another reason is also very important: preventing vertical dispersion getting too small. In a passive way: as long as you keep it 1st order its allright, but also not very effective:
In PA applications the same is often done, with much higher order FIR filters, then you have much more profit (bandwidth) with the extra driver. The main reason there is for the vertical dispersion control in the step to the high frequency driver....
I think that if you use the basic baffle compensation inductor (passive application), you do not make enough use of the extra driver, except in the situation where you have a very small baffle.......
But then: the small baffle is less efficient in he lower octave, so first you make a less efficient small speaker, and then compensate with an extra driver.... and if you make the baffle bigger the bandwith of the extra driver decreases, to keep the baffle correction lineair.... hmmmm
but in the bass region you'll have the higher sensitivity anyway off course......boem boem
I think you are both right, in your own way!
If you keep the impedance the same, the voltage sensitivity gets 3 dB more with driver doubling (as long as coupling of all the drivers within the wavelength is still possible off course).
So with the guitar amp: 1x 12"@8 ohms, or four 12"@8ohms (ser. ser. par.) is 6 dB more voltage sensitivity.
Compared to the 1x12", in the 4x12" cabin. each driver gets 1/4 of the power (same voltage @8ohms) wich is the same as a -6 dB output for each driver (compared to 1x 12"). So the powersensitivity per driver has not changed, but for the sum it has changed....
In my view this means that the benefit of multiple drivers is because of the doubling of radiating surfaces or sources....
And about the 2.5 way: I dont know exactly about the baffle step correction compensation, but if you adjust the series inductor (for the bottom bass-driver) to the baffle size it must work, very interesting issue....
But another reason is also very important: preventing vertical dispersion getting too small. In a passive way: as long as you keep it 1st order its allright, but also not very effective:
In PA applications the same is often done, with much higher order FIR filters, then you have much more profit (bandwidth) with the extra driver. The main reason there is for the vertical dispersion control in the step to the high frequency driver....
I think that if you use the basic baffle compensation inductor (passive application), you do not make enough use of the extra driver, except in the situation where you have a very small baffle.......
But then: the small baffle is less efficient in he lower octave, so first you make a less efficient small speaker, and then compensate with an extra driver.... and if you make the baffle bigger the bandwith of the extra driver decreases, to keep the baffle correction lineair.... hmmmm
but in the bass region you'll have the higher sensitivity anyway off course......boem boem
sreten said:
Simply because there are 4 x as many drivers... the amp is going to put out the same power because it sees the same impedance... Net gain 6dB.
Baffle step has nothing to do with the number of drivers, but the width of the baffle, 1 12 on the same baffle as 4 will have the same baffle step.
dave
planet10 said:
A) 6db in efficiency agreed. two drivers 3db more efficient.
B) show me a 1x12 guitar cab the same size as a 4x12.
🙂 sreten.
i dont think planet10 was saying that there was a single12 cab same size as 4 12 cab but that the theory was the same for the bafflestep
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