A 4ohm driver that is specified as 90dB/2.83V @ 1m is actually drawing 2W for that 90dB.
An 8ohm driver that is specified as 90dB/W @ 1m is also 90dB/2.83V @ 1m.
The 8ohm driver is delivering twice the volume for 1W as the 4ohm driver is when actually supplied with 1W = 2V i.e. 4ohm should be specified as 87dB/2V @ 1m to show true sensitivity to power input.
An 8ohm driver that is specified as 90dB/W @ 1m is also 90dB/2.83V @ 1m.
The 8ohm driver is delivering twice the volume for 1W as the 4ohm driver is when actually supplied with 1W = 2V i.e. 4ohm should be specified as 87dB/2V @ 1m to show true sensitivity to power input.
Andrew, the convention is mostly per 2.83V so we have a single yardstick. DCR for an 8 ohm driver is rarely more than 7 ohms in any case (if one can find an 8 ohm driver). And even then it's probably only actually 8 ohms in 3 places.
No, this convention works in a voltage driven world. The designers can decide on whether their amps an manage it (and how they are going to spec their power output.
No, this convention works in a voltage driven world. The designers can decide on whether their amps an manage it (and how they are going to spec their power output.
On that basis every manufacturer that makes available both 4ohms and 8ohms drivers will show the 4ohm driver as twice as efficient. Balderdash.
No, the manufacturer will show the sensitivity in manner that allows the user to decide which he/she requires and select the power to be delivered to that choice of driver as appropriate.
It can only be done by comparing apples to apples, i.e. dB/W
No, the manufacturer will show the sensitivity in manner that allows the user to decide which he/she requires and select the power to be delivered to that choice of driver as appropriate.
It can only be done by comparing apples to apples, i.e. dB/W
No, not balderdash! It has been thus for at least 35 years. I suggest you go back and look at spec sheets from Seas, Vifa, Tang Band, Scan Speak and even KEF if you can find them. All set to 2.83V, precisely so you can compare apples with apples (being voltage driven devices powered by voltage amplifiers).
And yes the lower Z ones show up as more efficient, though rarely by 6 dB because the magnetic circuit is usually saturated.
And yes the lower Z ones show up as more efficient, though rarely by 6 dB because the magnetic circuit is usually saturated.
Andrew, you really are a frightful know-all aren't you?
F=BIl, f=ma, a determines level. Halve the resistance, double the I, level doubles, Ie.6dB.
Works the same way when you put drivers in parallel.
My comment was that the magnet does not usually allow you to realise the full 6dB.
F=BIl, f=ma, a determines level. Halve the resistance, double the I, level doubles, Ie.6dB.
Works the same way when you put drivers in parallel.
My comment was that the magnet does not usually allow you to realise the full 6dB.
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Because we buy our equipment by power ratings.
The amplifier is power rated.
The speaker output is power rated.
If, as I have suggested a few times on this Forum, that we specify amplifiers by Vout into rated load, then it would make a lot of sense to use a voltage sensitivity.
But, that is not the way we specify amplifiers. We insist on using power ratings instead of voltage ratings.
The amplifier is power rated.
The speaker output is power rated.
If, as I have suggested a few times on this Forum, that we specify amplifiers by Vout into rated load, then it would make a lot of sense to use a voltage sensitivity.
But, that is not the way we specify amplifiers. We insist on using power ratings instead of voltage ratings.
While reading this I couldn't help but notice some similarities between Rick's plans and the 537 prototype I have been working on for some time now. The 537 consists of a fully discrete 3way subtractive filter, motional feedback correction, limiter and a 3886 trio with dc protection. The subtractive filter is based upon the 22AH587 Philips MFB enclosure. The whole project gets discussed over here , for those who's Dutch tends to be a little rusty, feel free to try the googleated version 
Component side
Schematic
xover print w/ limiter & mfb correction.
Component side
Schematic
even the woofer looks similar be it this is an 8 inch driver
An externally hosted image should be here but it was not working when we last tested it.
Component side
An externally hosted image should be here but it was not working when we last tested it.
Schematic
An externally hosted image should be here but it was not working when we last tested it.
xover print w/ limiter & mfb correction.
An externally hosted image should be here but it was not working when we last tested it.
Component side
An externally hosted image should be here but it was not working when we last tested it.
Schematic
An externally hosted image should be here but it was not working when we last tested it.
even the woofer looks similar be it this is an 8 inch driver
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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Nope, the LM3886 is a single channel amp, in order to do stereo you need two sets, i.e. 2 xover boards and 2 amp boards. The 537 is still very much in beta, once things are ready for production I'll move into the vendor area.
Yes it does require using a modified piezobuzzer mounted on top of the voicecoil, and yes, but it's fun to decomplicated it
see mfb.piratelogic.nl
This was an interesting proposition from Jeff Macaulay published in Electronics world years ago using a dual voice coil spkr: http://www.macaulayaudio.co.uk/roaring sub.pdf
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