DPDT Switches for Electrical Phase Reversals from a Crossover into Various Drivers - Page 2 - diyAudio
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Old 31st July 2012, 09:20 PM   #11
DrDyna is offline DrDyna  United States
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Quote:
Originally Posted by sreten View Post
Hi,

Driver polarity switches are a dumb idea, its either right or wrong.
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Old 31st July 2012, 10:42 PM   #12
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Originally Posted by sreten View Post
Hi,

Driver polarity switches are a dumb idea, its either right or wrong.
What is right or wrong sometimes is not as obvious as it seems.

rgds, sretem.
Yep. I get it. I just don't want to hear "I don't like the sound!"

I even offered to install the Xover on the back of the speaker, protected by a clear plastic casing, so he could experiment with polarity, crossing at 800/1600 and 5000/7000. But, nooooo, does not want that either.

He had better like the first and final result!
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Old 31st July 2012, 10:49 PM   #13
DrDyna is offline DrDyna  United States
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Originally Posted by PrecisionAudio View Post

He had better like the first and final result!
Well, the first result should be with correct phase, whether it's reversed or not. Whether a driver is connected in or out of phase is determined by the crossover. If it's in phase when it should be out, or if it's out when it should be in will result in a monstrous frequency response error, usually a suckout.

The basic lesson is there's really one way to do it, much like you wouldn't need a switch to make a fan spin backward, no matter how much you wanted to test the breeze on your face.
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Old 31st July 2012, 11:47 PM   #14
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Originally Posted by DrDyna View Post
As far as the receiver goes, older is probably better. A lot of the older receivers are actually much better at driving lower impedance than newer ones. They don't make em like they used to. It's most likely safe driving a 4 ohm load.
I have a couple older home receivers (late 80's early 90's) lying around which clearly state either 8ohm or 16ohm loads only. And, I have four 4ohm 6.5" carspeakers with 'built-in' tweeters. Running them wouldn't heat up the receiver's amp really fast??

It would add some sound to the garage area... Nothing loud. Radio would be nice!
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Old 1st August 2012, 05:45 AM   #15
AllenB is offline AllenB  Australia
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It is possible for phase to be 'in' or 'out' by any amount. Eg: If driver polarity were shown as two opposite points on a circle, phase could be anywhere on the circumference. The amount is also different at different frequencies.

This means for example that the phase of one driver might be in with the other driver near the crossover, but then overlap and fall out at higher frequencies, and vice versa at lows.

This is best adjusted using measurements but if you are patient, I'm sure you could stumble upon something that sounds good. So although you want the crossover on the back, you should be able to hide it later.

When you change the slope of a filter, you can reign back the phase shift to try to avoid one drivers phase crossing and overlapping the other. Eg. Changing from second order to third on just one of the drivers etc... and you still need to find the better polarity, but if you get the filters reasonably close and the response reasonably flat they should sound fine.
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Old 1st August 2012, 06:49 AM   #16
AllenB is offline AllenB  Australia
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Originally Posted by PrecisionAudio View Post
I have a couple older home receivers (late 80's early 90's) lying around which clearly state either 8ohm or 16ohm loads only. And, I have four 4ohm 6.5" carspeakers with 'built-in' tweeters. Running them wouldn't heat up the receiver's amp really fast??

It would add some sound to the garage area... Nothing loud. Radio would be nice!
Be sure the fuses in the amp are at spec and watch the volume setting Put pairs in series if interested.
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Old 1st August 2012, 08:38 AM   #17
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Originally Posted by AllenB View Post
Be sure the fuses in the amp are at spec and watch the volume setting Put pairs in series if interested.
My ignorance of electrical engineering again.

When you speak of putting the pairs in series, how would it work? I have reviewed diagrams of subwoofer drivers wired in parallel, series, and both combinations at once which present specific impedances. But, this is a bit different. As follows:

Each of the four Infinity 63.5i 4ohm driver units has the following: two terminals (pos/neg) to feed the 6.5" midrange and then just two terminals (pos/neg) to feed both the tweeter and super tweeter. These feeds come from the puny crossovers supplied. The crossovers present a 4ohm load to the amplifier...

I was wondering if there was a way that I could wire-up two drivers each (two drivers per channel then) so the load presented to the amplifier would be 8ohms yet not screw-up or fry anything.

And, if I did try this, would there be a way to test out the impedance using a digital multimeter before I connected it to the amplifier?
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Old 1st August 2012, 09:36 AM   #18
sreten is offline sreten  United Kingdom
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http://support.radioshack.com/suppor...oc65/65787.pdf

Hi,

You should add L-pads to the midranges and tweeters.

Whether the very simple (1st order) x/o works well
or not depends on the sympathetic choice of drivers.

rgds, sreten.

Wire the 4ohm car speakers in series for an 8 ohm load.
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Old 1st August 2012, 09:40 AM   #19
AllenB is offline AllenB  Australia
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A multimeter will measure resistance but not impedance. They are similar, but for a rule of thumb assume 3 ohms minimum for an average 4 ohm driver, where most of the range will be higher than this.

Putting two drivers in series will double this. You won't get any louder for the same volume control setting but the amp will be happier, and you may be able to turn it up just a little further.

About the tweeter and super-tweeter, if they are typical of these, they'll probably have little effect to the draw on the amp. Also they are not known for their sound. I'd prefer a good paper twin-cone.

For different reasons if you are going to run a pair of these in series then I'd disconnect one of the tweeter poles. Next, maybe an inductor on that woofer if they have a harsh top end.
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