posted
I have recently learned the basics of AC in my electrical science class. I am curious whether or not some of the things I've learned could be applied to the SPL world. After modeling my box in WinISD, I saw that the impedance phase was around 25-30 degrees. I know that this gives a pretty good power factor, but could it be improved by adding an appropriately sized capacitor (or inductor) across the terminals? It obviously won't help a ton since the power factor is around .85-.9 or even better already, but for people looking for every tenth, another 5-10% extra power might help out. Is this possible, practical, and/or within the rules? I'd like to hear what everyone thinks about this. Comments? Opinions? Testing?
posted
id say that it isnt a good idea. if you did that your amp would not like the capacitive or inductive reactance at all.
Posts: 24 | From: nyc | Registered: May 2004
| IP: Logged |
quote:Originally posted by chemid51: isn't that called a low pass x-over. (a coil in series with the voice coil)
"series" that is the key word that is wrong here
What is wrong with series here. Chemid51 is right in what he said. Or do you mean about the power factor part where it would be in parallel.
A capacitor wired in parallel with a speaker would get the power factor closer to unity, but it would also act as a low-pass filter.
I am not an electrical engineer, so I don't know too much about power factor, but I don't think it is too much of a concern for audio systems. The major place where it is important is with power companies where there are long distances for the power to travel. Along with these long distances there is also a somewhat significant loss of power through the wires resistance (around 10% loss), which is made worse with power factors which are not one. For a speaker system however, the wire runs are fairly short (especially compared to the power companies), so the added power loss caused as a result of the power factor of the speakers is not really significant.
Posts: 327 | From: Pleasanton & Sacramento Ca | Registered: Dec 2001
| IP: Logged |
posted
a coil wired in series with a driver would result in a 6db low pass filter
the original poster stated "across" the terminals which would mean it is wired in parallel with the driver
Posts: 3421 | From: Owosso MI, USA | Registered: Apr 2001
| IP: Logged |
posted
I know that this would not make a difference in a daily system as it would provide MAYBE 10% more power max provided my assumptions are correct. The difference would depend entirely on the particular setup.
As far as the amp "[not liking] the capacitive or inductive reactance at all" as daillengineer said, that's my whole point. A sub is not purely resistive. There is some reactive component to the impedance. If you can place the appropriate capacitor or inductor in parallel with the sub, I believe you might be able to reduce the reactance of the sub, bringing the power factor closer to 1. Like I said before, I don't believe that the increase in power would be more than 5 or 10% at best, but sometimes that small percentage can make a difference between 1st and 2nd. Serious competitors are looking for every tenth they can get and I thought this might be of use to someone if it actually works.
On a related note, is there anything in the rules that would prevent this? I don't recall anything, but I don't have time to dig through the rules again right now to see.
I'm in a high-voltage class for the next couple of days as part of my internship, so hopefully I can learn a bit more about power factors. It's an issue where I work because there are a lot of electric motors as big as 5000hp, which are obviously fairly inductive.
I'd like to hear what everyone else thinks about this idea. I only have internet access for the night, so I don't know when I'll see this again, but I'll check back in ASAP.
![[Wink]](wink.gif)
Printer-friendly view of this topic