View Full Version : Any Class D amp with GOOD DAMPING FACTOR??? Please Help Richard!!
03-19-2000, 05:27 AM
Currently I am in search on a class D amp, because I want to avoid upgrading my electrical system in my car. The real problem I am having is that I cannot find any class D amp with good damping factor. I was reading the DEI class D mono amp with damping factor of 42 @100hz...come on...what's the point with all that wattage with no subwoofer control. I went to Cadence's web site, and they don't tell you the damping factor of their class D amps either, but they do tell the specs of the class AB switching stuffs. Please recommend me something with high efficientcy and good damping factor please! I have a feeling that US amps are ok...but no luck with specs either....Are the products on the current market not able to provide best of both worlds???
03-20-2000, 10:46 AM
Damping factor is nothing more than the internal resistance of the amplifier. This is in fact an advertising jolly, as a damping factor of e.g. 5000 at a 4 ohm load just means that the internal resistance is 4/5000 = 0.0008 Ohm. If it's 100 at 4 Ohm load, then the internal resistance is 4/100 = 0.04 Ohm. This does not severely affect sonic performance, as the resistance is in series with the resistance of the voice coil. So a voice coil with resistance 3.7 ohm will become in fact a voice coil with resistance 3.7008 (DF 5000) or 3.74 (DF 100). This is about a 1% change, hardly significant, and well within normal tolerances on voice coils. Even a damping factor of 20 means only a 0.05 ohm extra resistance, about the same as the speaker cable and terminal connections...The damping factor, as other series resistances, does affect T/S parameters, but so does humidity and temperature. There is nothing wrong with a huge damping factor (in fact most great amps have quite large damping factors), but buying an amp BECAUSE of the damping factor may be like buying expensive shoes.
Peace, and Joy with your system!
03-20-2000, 12:43 PM
PoundMutt: Thankyou for the informative advice you gave me. Right now, I am looking for a more powerful amp, and would like a Class D or T amp because it goes easy on my electrical system. What amp would you recommend? I need something in the region of 800watts RMS. Would Cadence Class D, Planet Audio's new Class D, US Amp's Class T do a good job? I really like Cerwin Vega products, but none of their amps are Class D, yet I heard they are pretty awesome. Anyhow, my car has a 90 amp alternator, I'll be running a Phoenix Gold ZX350 for the front components, and a new amp for the 2 12 Vega 4 ohms that I got in a ported box. Another thought is that I kind of want to get the ZX600ti, because the amp is the same brand, kind of looks better...but one problem is that how much power will it be putting out at 2ohm mono?? Also, I run a ported box tuned at 35hz...there is no Subsonic Filter on the ZX600ti...will it be a bad idea to choose that amp?? Lastly, I know the bass cube that Phoenix Gold makes have a subsonic filter on it, but it cost too much, are there any other cheaper products out there with a subsonic filter??
03-20-2000, 08:57 PM
That basscube may be expensive , but it is worth it.
A zx600 will put out the same power into 2 ohms bridged as 4 ohms bridged.600watts because it is current limited.
Your stock electrical system would power a ZX600ti and a ZX350 no problem.Just make sure you add some caps and 2 gage wire.
03-20-2000, 10:03 PM
I think the guys have you covered on the unimportance of damping factor. Anything more than about 20 will do nothing to help control the motion of a speaker. The only side effect is a slight change in frequency response but it is in the tenths of a dB for a damping factor change of over 100! It simply means nothing. As for the subsonic filter it is always a good idea with a ported box. We have seen several amps that have subsonic filters built in and i would reccomend one of them as a choice. Stick to the class D amps if yoou can, they make a lot of sense.
03-20-2000, 10:07 PM
If you want to have a good understanding of damping factor check out the Feb 95 issue of the tech briefs titled amplifier output regulation. It is a really in depth technical dissucion on effects of changes in damping factor. In fact it is the most complete article I have ever seen.
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