If you invert one driver (out of two) in a ported enclosure will you still get the advantage of lower distortion and nonlinearities? I know if it's the clamshell config. or sealed, but what about proted?
yup! you achieve a degree of 2nd order cancellation by by having the drivers work in opposing direction (<>), and recieve the benifit of about a 20% decrease in volume. Additionally there is a loss of 3db for the acoustic coupling and a gain of 3db (assuming your using a good solid state amp) for parralleling the drivers and halving the impeadance. Physically speaking the drivers must be coupled in their own chamber (i.e. normal execution except in the enclosure you have another box/tube behind the driver at about the size of the drivers diameter where another driver is coupled to this chamber so that the rear radiation of the first driver, or the driver facing into the room, is enclosed in this small chamber - and the 2nd driver takes its place in the normal box chamber.)
I noticed that ds21 and scottg may have a bit of a communication error. Ds21 was not clear as to whether the speakers will be Isobarik or normal 2x mounting. The cancellation will only occur if they are isobarik. I don't know the effects of just inverting one driver when not set up isobarik. Beware; port length must be doubled and box volume halved in an isobarik setup. If you use box programs you double the Vas for a clamshell configuration.
Anyone know how much the volume of air in between the drivers matters? In a clamshell this volume is small enough to be rather insignificant. Other isobarik setups may be affected by this though as 10L+ of air can couple the subs. I've tried to find this out but to no avail.
Anyone know how much the volume of air in between the drivers matters? In a clamshell this volume is small enough to be rather insignificant. Other isobarik setups may be affected by this though as 10L+ of air can couple the subs. I've tried to find this out but to no avail.
ds21 said:
Termed push-pull loading, if the drivers are non-linear wrt how they move towards the motor vrs moving away, you can achieve some reduction (cancellation) of non-linear distortion.
This is really only effective at low frequencies and you may end up with complications from noise from the driver basket. If your driver has a pole-piece vent i wouldn't recommend it.
Drivers like Lambdas & Skannings will probably not gain anything from this technique as they are very linear already.
An example
dave
The reason I ask is because back in the early 90's I used to work in CA. selling these:
http://www.arsenal.net/speakers/allison/1989series.jpg
Notice the inverted woofer on the florr stand models, they told us it would lower distortion, just wondering if this was true?
http://www.arsenal.net/speakers/allison/1989series.jpg
Notice the inverted woofer on the florr stand models, they told us it would lower distortion, just wondering if this was true?
ds21 said:
In theory... the ones that run the inverted drivers up into the mids probably sacrifice midrange clarity.
dave
CarMan said:
Not having experimented on this in particular, but thinking of the concepts involved, I would think that the lower the volume of air enclosed between the two drivers the better.
The two drivers are coupled by the air mass enclosed, and as this increases, it will add compliance to the system, by acting like a damped spring. This will change the overall response of the system.
However, this may be a good thing if you like tweeking, yet another thing to play with to tune your box!😉
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