Joined: January 19, 2003 Location: Bouvet Island Posts: 5,024
Posted: April 05, 2006 at 4:29 PM - IP Logged
I would use a 2 ohm to 16 ohm, 5 watt (or so), linear taper pot. (The resistance stated on any pot is the maximum resistance - so a 2 ohm pot, or a 16 ohm pot, or something between those values should be fine...)Probably wont HAVE to have a 5 watt power handling, but too small might burn out... I have never done any experiments to figure the actual power produced by a secondary voice coil. The lower the resistance the pot is, the more power it will need to be able to dissipate. ___________________________________ It all reminds me of something that Moliere once said to Guy de Maupassant at a cafe in Vienna... That's nice. You should write it down.
What about driving just a single coil, and leaving the other open? Well, as you would guess, the push is weaker. The system has a peakier resonance (for the techie types, Qts increases because Qes increases). BUT - let's drive one coil, and short the other. Guess what? Things change from the original (both coils driven) situation, but they also stay the same. The driven voice coil is pushing and pulling, as normal. But what about the shorted voice coil? Well, it's trying to keep things at rest - it's trying to resist ANY motion! The net result is the overall peakiness of the resonance is the same as it was when both coils were driven, even though we are only using half the motor (driving one coil). The other coil helps "tame" the driven coil, so that the system basically behaves the same as before.
He mentions driving a single coil and leaving one open and driving a single coil and shorting the other. What is the difference between the two?
Joined: November 06, 2003 Location: Oregon, United States Posts: 1,738
Posted: May 13, 2006 at 5:20 AM - IP Logged
Acutally power handling isn't halved. Here's a quote by Dan Wiggins on this topic:
"Lastly, power handling isn't compromised by a factor of 2; it's usually decreased 10-25%. The reason is that rarely are you current-limited by the gauge of the wire, and voice coils are wound concentrically so you still have the entire thermal mass working for you. Just that now all the power is dissipated in a single voice coil (typically two of four layers) so you may end up with an inert, non-conducting thermal mass insulating one side of the voice coil. This does not halve power handling, but can reduce it somewhat."
Joined: January 28, 2006 Location: United States Posts: 175
Posted: May 18, 2006 at 10:45 PM - IP Logged
good point but here is what you have to keep in mind. when you are selling equipment in a business type atmosphere you want to stock equipment that can be versatile enough to fit a bunch of different customer's needs. and it helps if you can show the customer that the equipment they are buying today will allow them to add to the system without having to get rid of the old equipment first. for example i usually mention that if they are getting 1 sub (maybe for a truck or something that has limited space) then they should choose a woofer with DVC and a slightly bigger amp so that they can later add another sub to the same amp if they move the system to a car or extended cab. then i explain that with the single woofer you can use one VC (4 ohms) and wire that into the bridged setting on the amplifier (mainly because everyone wants the amp in mono) and with 2 subs you can wire them into 8 ohms each and then mono that into the amp. this way they are always getting maximum performance out of the amp and the sub or subs. great solution and it so much easier to teach sales person which brand to sell versus having 4 or 5 different model number in each woofer line. ___________________________________ "I cannot teach anybody anything, I can only make them think."
Joined: May 10, 2006 Location: United States Posts: 5
Posted: May 19, 2006 at 9:00 PM - IP Logged
i do agree in the business world, that may be brought up. I can't say that I havent said that to a customer already but point being...its not the best route. For people that do want to keep that amp because they dont have the money for another one...that may be just fine :)
Joined: June 10, 2005 Location: United States Posts: 3
Posted: May 27, 2006 at 4:51 PM - IP Logged
Are any of the other Thiel Small parameters affected by running only one of two coils? Mainly concerned on how box calculations would be affected by running only one coil and if the published manufacturers recommended enclosure size would still be valid...?
Good topic, lots of snake oil going around about this....
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