View Full Version : Wmtm
10-03-2005, 12:21 AM
I Wnt to do a three way using the RS270 for the woofer and 2 RS150's for the mids. I am thinking 2 RS150's because their spl is slightly lower than the RS270. If I use 2 RS150's as the mids I would not need all of their combined gain and will have to pad them down. My question is should I connect them in Parrallel or Series? I do not know what the gain would be in series. I know it will be 6db in parrellel. I do not know how 16 ohms will affect my amp which is rated at 4 and 8 ohms.
10-03-2005, 01:10 AM
If you wired them in parallel there would be a 6dB gain (+3dB from double the power and +3dB from double the cone area).
If they were wired in series the spl would stay the same because there is only going to be half the power flowing through the drivers due to the doubling of resistance (8ohm to 16ohms= twice the resistance therefore -3dB) and a +3dB gain from cone area esentially cancellling each other out.
The RS 270 does have slightly greater spl than the RS150, but there is also an spl rolloff in the bass region starting below 100hz or so and getting down -6dB near the lowest end of the spectrum, that is why people usually wire 2 woofers in parallel for a 6dB gain.
In your case you should use 1 RS270 1 RS150 and 1 tweeter, and you would still have to pad down the RS150 by -4dB to match the RS270's spl in the lower bass region, and appropriately pad down the tweeter as well, or wire 2 RS270's in parallel for a gain to match the woofer region with the mid and tweeters efficiency, however doing that would yeild a +2dB in the woofer region over the mids and tweet but you would probably end up liking that anyways if you like bass.
10-03-2005, 01:11 AM
> I Wnt to do a three way using the RS270 for
> the woofer and 2 RS150's for the mids. I am
> thinking 2 RS150's because their spl is
> slightly lower than the RS270. If I use 2
> RS150's as the mids I would not need all of
> their combined gain and will have to pad
> them down. My question is should I connect
> them in Parrallel or Series? I do not know
> what the gain would be in series. I know it
> will be 6db in parrellel. I do not know how
> 16 ohms will affect my amp which is rated at
> 4 and 8 ohms.
If you connect them in series, your theoretical gain would be zero. You get +3dB gain from using 2 drivers, but lose that gain due to doubling of the impedance.
BTW, the theoretical gain for drivers in parallel or in series assumes the following:
1) the operating frequency of the drivers are "low enough"
2) your amplifier is a perfect voltage source
Usually, neither conditions are true. So in reality, usually you wind up somewhere in between.
(Originally posted by: kyle)
Go with one RS150 or wire them in series.
I am running a pair of RS180's (lower sensitivity) in series in a WWMTM with two RS270's on the bottom end.
I would propose you consider a pair of RS225's with the RS150 (same basic box size) as they'll allow you to let the woofers cover ALL the baffle step and cross to the mid(s) and tweeter without much (if any) tweeter padding. The RS270's break-up early enough that contribution up to 1000Hz may not be desired.
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