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Discussion Starter #1
Please excuse if this is an OT that has been discussed in the past.


I have just acquired a Crown K2 to power this driver and it seems that there are three possible ways to connect the two:


1) 2-channel mode, one into each VC.

2) Bridged mode into VC's in series.

3) Bridged mode into VC's in parallel.


The K2 is rated to 2 ohms so option three may not be desirable.


My question is which configuration is best and why?


Doug
 

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Doug, I have a K2 feeding a dual HE 15 cabinet, and I run one driver on each channel, with the 2 voice coils in parallel on each driver. If I were to run a single HE 15, I would run one voice coil on each channel in order to keep distortion and noise to a minimum, as well as maintaining the most stable load presented to the amp.
 

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I would start with one channel of the K2 connected to each voice coil, with the inputs "Y'd" together (a switch on the back). This gives you and expected 1600W into the HE15 which you can see if you ever get close to clipping the amp. I know of others who have sucessfully bridged the K2 into the 2 Ohm load, and you can likely get a near 2500W output, but distortion increases with such a low impedance load. I would stick with one coil per channel.


Mark Seaton

Sound Physics Labs, Inc.

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Thanks for the replies Bob and Mark. Hopefully the PR18's will get here soon so I can finish the cube and do some experimenting with this. That's the part of a DIY project that I like the best.


BTW: Am I reading your messages correctly, that the two 3 ohm VC's wired in parallel yield a 2 ohm load? If so then I guess DCR doesn't exactly follow impedance.
 

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As much as I respect Bob and Mark, I have to disagree with running 1 voice coil on each channel. In simple terms, if the output of the 2 sides of the amplifier is not identical, you could run into the situation where one voice coil is pushing the diaphragm out, while the other is pulling it in causing the signals to cancel each other out.


I have my HE 15 wired in series, with a Crest 901 bridged, presenting the amp with an 8 ohm load. With this configuration, I am giving up 6 db's * of headroom, for having the voice coils always in phase with each other. Even with 500 watts, this thing is still loud enough to rattle the snares on a drum 50 feet away.


The question you need to answer is are you looking to squeeze every last db out of your sub at the expense of long term wear on your amplifier. A 2 ohm bridged load will produce more output, but will make the amp run hotter. An 8 ohm bridged load will make the amp run cooler, in theory last longer, but at the expense of 6 db's * max output.


* Based upon the assumption that doubling the power, increases output by 3 db's, and the amplifier doubles down with impedance.
 

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Jim's point is true, presuming there is significant differences between the channels of the amplifier. In a stereo amplifier, I'm not too worried about this.


What is incorrect is to think that one coil would be pushing while the other is pulling. 2 amplifiers of the same design won't have different phase, but they may be slightly mismatched in gain. This would mean that one coil will recieve a scaled signal relative to the other. Again, not something I see anything to be concerned about. For peace of mind, and minimzing wires, feel free to connect the coils in series and drive the K2 in bridged mode. This will result in the same output as driving one coil per channel. In short, you ARE NOT going to burn up your HE15 from driving it one coil per channel. In fact, if you were to turn one channel completely off, all you would be doing is changing the parameters of the driver, while giving it less power. No damage done.


Mark Seaton

Sound Physics Labs, Inc.

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I would run it one channel per coil. In bridging the amp, you also inherently increase distortion by ~3-5 times (according to what I've read). To balance the levels, you can simply hook up one side of the woofer, measure the level with a test tone (or use several tones and average the results) then do the other side and set the gain accordingly. I *think* that it is the case that a bridged situation into 8ohms is equivilant stress wise to running a channel per coil, but with the expense of more distortion. I think that if you trust the amp's symmetry enough to bridge it at all, then you should trust it to run "stereo."


Just my .01


Vince
 
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