Another driver can't be represented by an "equivalent" resistor.
It doesn't matter what you wire in series with a speaker driver.....a resistor...a capacitor...or the kitchen sink....it doesn't change the Qes of the individual driver itself....only (potentially) the larger system.
You can visualize this by using any of the many speaker/box simulation programs and looking at the response shape of a single driver versus two identical drivers wired in series. (Simulate an infinite baffle by making the box really big.)
Cheers,
Dave.
It doesn't matter what you wire in series with a speaker driver.....a resistor...a capacitor...or the kitchen sink....it doesn't change the Qes of the individual driver itself....only (potentially) the larger system.
You can visualize this by using any of the many speaker/box simulation programs and looking at the response shape of a single driver versus two identical drivers wired in series. (Simulate an infinite baffle by making the box really big.)
Cheers,
Dave.
Quote
You actually both double length of wire in the magnet field and double the magnet field itself because there's two air gaps
B is the value of the induction flux in which every little bit of wire is immersed. With two identical drivers in series or in parallel, B is not doubled.
The initial question is not precisely defined. Most arised questions can easily be answered in thinking that :
- when the distances between the two drivers and their emitting areas are sufficiently small compared to the wavelength, the whole can be considered as a new loudspeaker having a doubled emitting area and a double motor.
- whatever the frequency, the acoustic pressure on the axis between the two drivers is always doubled compared to when only one is driven. Doubling acoustic pressure, expressed in SPL, undoubtedly corresponds to +6 dB.
You actually both double length of wire in the magnet field and double the magnet field itself because there's two air gaps
B is the value of the induction flux in which every little bit of wire is immersed. With two identical drivers in series or in parallel, B is not doubled.
The initial question is not precisely defined. Most arised questions can easily be answered in thinking that :
- when the distances between the two drivers and their emitting areas are sufficiently small compared to the wavelength, the whole can be considered as a new loudspeaker having a doubled emitting area and a double motor.
- whatever the frequency, the acoustic pressure on the axis between the two drivers is always doubled compared to when only one is driven. Doubling acoustic pressure, expressed in SPL, undoubtedly corresponds to +6 dB.
Saturnus, Davey,
I am going to partially eat my hat.
Just measured two drivers (Dayton ND105-4) in series, a single driver, and a driver through a 4Ohm resistor.
In the latter case, Qes doubles, as expected.
Two drivers in series, however, only cause a moderate rise in Qes, about 10 %.
Thank you for correcting a misconception I held for decades.
vac
I am going to partially eat my hat.
Just measured two drivers (Dayton ND105-4) in series, a single driver, and a driver through a 4Ohm resistor.
In the latter case, Qes doubles, as expected.
Two drivers in series, however, only cause a moderate rise in Qes, about 10 %.
Thank you for correcting a misconception I held for decades.
vac
😕 What resources are you refering to?
I was not comparing Focals to Seas. Like I said earlier when my wife and I were looking (not yet hearing) for speakers we like the look of the Focal Chorus 800 series (the Electra had better finish but was beyond our budget).
Speaker we saw for the living room were
Focal Chorus, Kef Q, Montior Audio Silver, and Dali Ikon
for the bedroom were
Heco Celan XT, Elac 180, Triangle Esprit and Morel Signature
Of all of these the Focal's looked nice and fit best into our enviroment.
I have DIYed a few pairs of speakers in the past. I used to have access to LEAP/LMS and can still get this access to measure the drivers once I decide on a general design.
Since I do not have the luxury of improting and returning drivers I needed to fist choose the drivers. I first considered Morel and SEAS drivers but could not get them locally. Wavecor is available locally. So thats why I ended up looking at Wavecor. After all atleast one manufacturer uses Wavecor http://hometheaterreview.com/audio-physic-avantera-floorstanding-loudspeaker-reviewed/?page=2
This is what I felt. Hence I saw no harm in putting 3 drivers in series. AVR amps are poor when it comes to dumping current so i figured a higher impedance (12 ohms dropping to 8 ohms above 200Hz or so) would relieve the AVR of this stress.
The other option would have been to put 3 8ohm woofers in parallel and use a 4 ohm mid-bass there by having an impedance of less than 3 ohms below 200hz or so. Matching sensitivities would be another issue.
Q: Why is there a moderate rise in Qes?
Compared to what? The original information is not complete. Probably the two in series had a moderately higher Qes than ONE of the drivers. But supposing the other driver had a higher Qes by itself, we'd expect a moderate rise in Qes.
Plus, let's get real, parameter measurement has a significant amount of fuzziness, and is not ultra-consistent over time even with the exact same setup measuring repeatedly.
And maybe the drivers were not mounted exactly the same way between the compared measurements.
"People" connect drivers in parallel just for convenience... 8 Ohms drivers. That's why you got it. Call it a myth or superstition if you want. Welcome to the club.
Head_unit, Vacuphile stated that when 2 drivers were connected in series there was only a moderatre rise in Qes. I wonder why the rise was only 10%. Was it only part of the Qes that got added?
In theory, Qes should have remained the same and not increased by 10%. But as head_unit noted, there is "fuzziness" and other variables like measurement error, small difference between the two drivers, etc, etc, that affected the outcome. Extracting T/S parameters from measured data is.......fun. 🙂
Cheers,
Dave.
Cheers,
Dave.
I am not sure if what I'm saying is applicable.
If you are using a solid state amp, and that amp doubles it's power into half as much impedance, then you should go for a lowish impedance. This would suggest parallel wiring.
With a tubed amp, power increases slightly with higher impedance. All woofers in series would be best.
If you are using a solid state amp, and you wire them in series, you will NOT get +6dB.
If you are using a solid state amp, and that amp doubles it's power into half as much impedance, then you should go for a lowish impedance. This would suggest parallel wiring.
With a tubed amp, power increases slightly with higher impedance. All woofers in series would be best.
If you are using a solid state amp, and you wire them in series, you will NOT get +6dB.
You are right when it comes to dedicated power amplifiers but I wont have that opportunity. This application will use an AVR like the Marantz 6006, Pioneer LX75 or Denon 3312Ci.
Most AVRs cannot dump current like a good solid state power amp. Hence they have trouble dealing with low impedace loads (even more true in the bass where the reactive part of the impedance is siginificant).
Yes I wont gain 6db but this is fine by me. In Post 26 (on this thread) I calculated that the sensitivity of 2 90db/2.83V 4ohm woofers in series is still 90db/2.83V.
The sensitivity of the woofer and midbass I intend to use are about the same and I would not want the combination of multiple woofers to increase the sensitivity of the woofer section (3 woofers).
In like to the original question. I see where you get the +3 dB increase from doubling the piston area. I see where you also can get double the output of the amplifier. But here is where I've been scratching my head. Say you have a driver @ 8ohm with an 150watt amp. You add another in parallel, you'll get +3dB for the added driver, +3dB for doubling the amp output (now a total of 4 ohm at ~300watts). Ok, understood. Now say you still have the same two drivers, but they each get their own 150watt amp. Do you still get your +6dB? 2 drivers on the same amp would yield you the ~300watts, but wouldnt half the total output of the amp be going to each driver? so 150+150=300w amp output. If voltage is constant, a driver will never draw more power than it's impedance will allow. So there should be no difference between two 8ohm drivers in parallel, vs two 8ohm drivers backed by equivalent amps. How-ever Im getting a conflicting response from another Audiophile. He's saying with using 2 amps to run 2 drivers, you dont get your 'amp gain' and you can only get the +3dB gain. Is this true? Can someone explain this for me? Thanks!
Voltage squared divided by speaker impedance (which varies with frequency) = watts.
It makes no difference in level whether two speakers get 300 watts/"X" voltage from one amp or 150 watts/ "X" voltage each from two amps, watts are watts.
No difference. You get the same 6dB SPL and +3dB power delivered to the load given the same input signal at the driver terminals whether you use one amplifier, two, or four in a pair of full-bridge configurations.
My active tri-amp main system output doesn't change if I run the two bass drivers per side off their own amplifier channels or parallel them and use a single stereo amplifier.
There is no such thing as amp gain, the 6dB increase with a doubling of speakers (keeping the watts to each speaker the same) is just the result of the efficiency of a speaker being directly related to Vas: Eff=(27E-6 x (Fs^2))/Qes. With doubling the number of speakers, you also double the Vas and hence the efficiency. This is how stacks of subwoofers can get to over 50% efficient, whereas each speaker would only be a couple of % by itself. Also the trick behind column arrays, the Bose 802, etc.
If you go from one speaker to two, and at the same time maintain the same voltage at each woofer, then you will be doubling the power consumed. If the two speakers are connected to the same amplifier then they are cutting the load the amp sees to half impedance, causing twice the current to flow and so doubling the power. If you connect a seperate amp to each woofer then whatever the first amp was delivering to the first speaker has now been duplicated in the second pairing. That is clearly a doubling of power.
Instead of seeing a 3dB gain from the two speakers we usually see a 6dB gain. The first 3 comes from the power doubling and the second is usually referred to as mutual coupling. If the drivers are close together relative to the wavelength then the extra +3 is achieved in all directions and our true efficiency has doubled. If they aren't so close then we still get the 6dB, but it is only on axis and amounts to a directivity (d.i. +3dB) gain.
There is no direct connection of efficiency with Vas. The efficiency constant equation may imply it but it isn't really an answer to the woofer doubling situation. For example, putting a single woofer into double the box will not change efficiency, but some might think the equation implies it. It doesn't.
David S.
Instead of seeing a 3dB gain from the two speakers we usually see a 6dB gain. The first 3 comes from the power doubling and the second is usually referred to as mutual coupling. If the drivers are close together relative to the wavelength then the extra +3 is achieved in all directions and our true efficiency has doubled. If they aren't so close then we still get the 6dB, but it is only on axis and amounts to a directivity (d.i. +3dB) gain.
There is no direct connection of efficiency with Vas. The efficiency constant equation may imply it but it isn't really an answer to the woofer doubling situation. For example, putting a single woofer into double the box will not change efficiency, but some might think the equation implies it. It doesn't.
David S.
No, but two woofers in a box double the size will. S'pose thats understandable to most readers. And it is the answer to the question where this magic doubling of efficiency comes from.
Even if that were "understandable to most readers" it is incorrect. The issue is not tied to box volume but relates to the use of two sources and their intereactions.
The magic doubling is, as I explained, a combination of mutual coupling or the rise in radiation impedance, and the increase in directivity. The two factors always combine for a broadband +3dB (added to the power +3 dB).
David S.
The magic doubling is, as I explained, a combination of mutual coupling or the rise in radiation impedance, and the increase in directivity. The two factors always combine for a broadband +3dB (added to the power +3 dB).
David S.
I agree it is not linked to box volume, but that is not what I said, it is about Vas. For two identical drivers combined, double the Vas. Double the Vas (look at #55 for formula), and you double the efficiency. We are speaking sound power here, so issues like 4pi or 2pi radiation or the trajectory in between do not come into play.