HOLY MACKEREL!!!
I have never read such a confused bunch of stuff on the DIY Forum in my life!
No wonder Scott Wurcer is confused!
Bill Fitzpatrick is right. Mutual coupling really exists. Bill's explanation about an effective reduction in solid angle is spot on.
SY's explanation is wrong. As Cocolino pointed out, SY is counting the same thing twice.
I'm not going to explain further, as it's already been explained very well. Just go back and re-read Bill's posts and you'll know the answer to the original poster's question.
I have never read such a confused bunch of stuff on the DIY Forum in my life!
No wonder Scott Wurcer is confused!
Bill Fitzpatrick is right. Mutual coupling really exists. Bill's explanation about an effective reduction in solid angle is spot on.
SY's explanation is wrong. As Cocolino pointed out, SY is counting the same thing twice.
I'm not going to explain further, as it's already been explained very well. Just go back and re-read Bill's posts and you'll know the answer to the original poster's question.
Yes WinISD is flawed at very huge enclosure size.
But it would only take about 2300 Tumults to reach 120 dB/1w/1m in a vented enclosure of 300000 liters tuned to 22 Hz.
You get a very solid 120 dB/1w/1m down to 24.6 Hz.
So, you'll get at full excursion with a 7.6 MW amplifier, a really solid 188.8 dB.
But to benefit more of mutual coupling, better go with pro drivers with efficiency at around 99 dB/1w/1m, dropping the need to only 128 drivers to get the same 120 dB/1w/1m.
Sorry for so late reply, but I think after reading:
Loudspeakers, Mutual Coupling and
every think would be clear.
Loudspeakers, Mutual Coupling and
every think would be clear.
No, that's not a fact in the case of this "something" that we're talking about.
Consider two semi-trailer trucks driving down the road.
If you place one truck closely behind the other then you suddenly get this "something for nothing" - you get to move twice as much stuff for less than twice as much gas.
So, I don't have the proof, or article to site at the moment, but I do know that with two drivers operating in proximity (wired in series, for the sake of this argument) you do get increased efficiency ! :O
Can someone tell me what happens if I have a cab with 4 woofers inside and I place another cab with 4 more woofers alongside it. Would I get a +3db boost or the boost will be larger. Specs( 4 dayton classic subwoofers 89db sensitivity. 89 + 3 + 3 + 3 = 98db 1W/1m. 100Watts per driver = 118db spl. ). What happens if I add another cab with these exact specs next to my first cab. Do I get just 3db due to coupling?
Thx djk.....so if I want the +3db per driver effect would I have to put each woofer in its own cab then place them side-by-side on the floor? My target SPL is around 129-132db SPL and the drivers are very inefficient, 89db 1W/1m. My winIsd modeling of this driver gives me 190db 1W/1m spl from 28Hz up. So 100Watts per driver should give me 20db + 21(7woofers x 3db=21) + 190db = 131db spl. I really don't wanna build 8 cabs and the wife has divorce papers ready @ the first sight of any 5ft tall tower building inside her building. Any suggestions at achieving that 130db spl down to 28Hz with my 800watts and 8 woofers?
If two identical drivers in close proximity (distance << wavelength) are voltage driven by the same signal as it is usually done, the whole emitting is doubled, the excursion remaining the same.
That implies doubling the moved air volume and doubling sound pressure : +6 dB SPL.
So the sensitivity is enhanced by 6 dB (for the same driving voltage)
However, from the point of view of electrical power, the current in the circuit is doubled.
I leave you to calculate the gain in efficiency.
That implies doubling the moved air volume and doubling sound pressure : +6 dB SPL.
So the sensitivity is enhanced by 6 dB (for the same driving voltage)
However, from the point of view of electrical power, the current in the circuit is doubled.
I leave you to calculate the gain in efficiency.
Thanks for replying Forr. I made a typo in that last reply. The woofer sensitivity is 90db spl after modeling(90db + 20db(100watts per woofer) + 21db(7 x +3db)=131db spl. Forr is saying +6 db per woofer. I now re-calculate. 90 + 20 + 42(7woofers x +6db) = 152db spl. Forr, I don't quite understand the (current doubling) part. These woofers are 4ohm each and I have wired 2 in series then each pair in parallel to give 4ohms. Amp being used is Behringer EP4000. Can u explain the current doubling and is that enough power to produce spl I'm after.
With any sort of room gain you may be pretty close, without you are only 2 dB short (if your simulation is valid):
90 dB sensitivity (one speaker)
93 dB combined sensitivity (two speakers)
96 dB combined sensitivity (four speakers)
99 dB combined sensitivity (four speakers)
99 dB 1 watt
109 dB 10 watts
119 dB 100 watts
129 dB 1000 watts (800 watts would be 128 dB)
Hi Codefall,
Let's say the drivers are identical and having a sensitivity of 90 dB.
And let's stay with wavelengths greater than the distance between them,
If the drivers are in series, the voltage across each is halved,
each delivers -6 dB SPL. But their coupling gives +6 dB SPL.
So in series, the coupling of the drivers gives the same SPL
as one driver alone.
2 drivers in series -> 90 dB SPL
Despite the SPL has not changed,
the current in the circuit is halved,
and so the electrical power (-3 dB),
hence, there is an increase in efficiency.
When the two drivers are in parallel and the amp is a voltage source,
the voltages across them are equal, and the is a 6 dB SPL increase.
2 drivers in parallel -> 96 dB SPL
The current in the circuit is now doubled,
and so the electrical power (3 dB)
but the SPL has increased of 6 dB,
once again there is an increase in efficiency.
If you connect
two drivers in series (90 dB) // two drivers in series (90 dB SPL)
you get 96 dB SPL for the same amp output voltage and the same current in the circuit as for one driver only.
You get a significative increase in efficiency.
Nevertheless, do not think that's coupling a lot of drivers could be a mean to get a huge efficiency. The limiting factor is the distance between the drivers.
Let's say the drivers are identical and having a sensitivity of 90 dB.
And let's stay with wavelengths greater than the distance between them,
If the drivers are in series, the voltage across each is halved,
each delivers -6 dB SPL. But their coupling gives +6 dB SPL.
So in series, the coupling of the drivers gives the same SPL
as one driver alone.
2 drivers in series -> 90 dB SPL
Despite the SPL has not changed,
the current in the circuit is halved,
and so the electrical power (-3 dB),
hence, there is an increase in efficiency.
When the two drivers are in parallel and the amp is a voltage source,
the voltages across them are equal, and the is a 6 dB SPL increase.
2 drivers in parallel -> 96 dB SPL
The current in the circuit is now doubled,
and so the electrical power (3 dB)
but the SPL has increased of 6 dB,
once again there is an increase in efficiency.
If you connect
two drivers in series (90 dB) // two drivers in series (90 dB SPL)
you get 96 dB SPL for the same amp output voltage and the same current in the circuit as for one driver only.
You get a significative increase in efficiency.
Nevertheless, do not think that's coupling a lot of drivers could be a mean to get a huge efficiency. The limiting factor is the distance between the drivers.