GlassWolf Or any one else with input.


Bronze Member
Username: Avalanche

Post Number: 29
Registered: Nov-04
I currently have a US Amps 3000.
the thing that is bothering me is that it needs a
450 amp fuse.
My vehicle comes with a 105 amp alternator.

This thing requires alot by itself. What type of alternator would you recommend to power it up plus the additional 4 amps that I have.

With this type of Amps you can weld with. Wanted to see what Glass or anyone else had to input on this.
I put the specs of the amp here so you see what they are.

Two Channel Class AB Amplifier
Total Power Output: 3000 Watts RMS
THD at Rated Power: 0.1%
Signal/Noise Ratio: >105dBA
Frequency Response: 5Hz-50KHz
Damping Factor: >2200
Fuse Rating: 450 Amps
62mm / 2.44in High
229mm / 9.0in Wide
629mm / 24.75in Long

Weight: 7.26kg / 16.00lb
Variable 24dB Low-Pass Active Crossover

One Ohm Stable
1500 Watts x 2 into 1 Ohms
3000 Watts Bridged into 2 Ohms
Available in Black or Chrome

Oh just curiouse what does this mean.
Damping Factor: >2200

Thank you in advanced.

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 5882
Registered: Dec-03
umm two or three 300A alternators.. at least. heh
that, lots of 00ga cable, and a bank of deep cycles

Bronze Member
Username: Lbeckner

Tulsa, Ok Usa

Post Number: 59
Registered: Oct-04
450 amps is a lot of power!! To bad its not a class D amp then you would have less of a problem. Geeze can you put two alternators in you car? Are you going to compete? If so just add extra batteries. Otherwise a 10k farad capacitor should do the trick. What speaker r u using?

Bronze Member
Username: Avalanche

Post Number: 30
Registered: Nov-04
Well I have 2 4k farad caps already plus 2 optima Yellows.

I have a Avalanche. I was thinking that maybe I could add a second alternator and make it 250 - 300 amps just for the system. Do you guys think this would work. That way I also Isolate all of the audio equipment from the rest of the truck.

and can any one answer this.

Oh just curiouse what does this mean.
Damping Factor: >2200

Oh about the subs I am debating between 2 RE X.X.X 15 at 1500 rms apiece or 2 TREO SSX 15
any other sugestion would be good. And I know No Audiobahn.
I am really looking for a sub that can be both SQ and SPL. Mainly SQ though.

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 5889
Registered: Dec-03
the single 300A alternator would be good as a dedicated one if the system isn't run at full volume much with the engine running.
if you want SPL burping, do it off the deep cycles with the motor shut off and it should be fine for brief burping.

as for damping,

Damping factor is rarely published with low to medium grade amplifiers but it is almost always published with high end American amplifiers. And even when it is published, it is rarely published correctly. The damping factor is the ratio between the load impedance and the amplifier's internal impedance (load impedance divided by internal impedance). Like output power ratings, the damping factor is an amplifier characteristic that cannot be represented by a simple number.

An impedance value is a complex number made up of a real term and an imaginary term. The real term comes from the resistance of the object being measured. For example, if you measure the resistance of an 8 ohm driver with an ohmmeter, you will find that it is around 6.3 ohms. Some times, this is referred to as the DC resistance, but this is being redundant because a resistance value by its nature must be taken at DC. The imaginary term is from the inductance and reactance of the object being measured. A driver's voice coil, for example, is made up of winds of wire. The resulting effect is an inductor contributing a significant amount of inductance to the impedance value. There is also a bit of reactance caused by inherent capacitance between parallel wires in the driver assembly but it is usually small enough in a driver that its value is negligible.

Those familiar with a complex value will know that its behavior is dependent on the frequency of the source signal. The impedance of a driver might be 8 ohms at say 100Hz but it could be 30 ohms at 1kHz. Thus any measurement taken that is dependent on the complex impedance of a driver will also be dependent on the frequency of the source signal. So the damping factor of an amplifier will be dependent on the frequency of the signal that the amplifier is generating, which is the reason why you can't just give a single number as the damping factor like most manufactures do.

As if that isn't complicated enough, keep in mind that the impedance graph is different for each driver, the amplifier's internal impedance is also complex, and you have to figure in the impedance contributed by the wires and connectors used in the signal path. In other words, it is impossible to accurately specify a damping factor. This is all fine, but what bothers me is that most high end amplifier manufacturers just publish a number with no indication to the uselessness of such a simple representation of what is a complicated relationship between the amplifier and the load.

Not all amplifier manufacturers are lazy so some come up with ways to specify the damping factor. One way manufacturers specify it is to limit the various conditions that the damping factor is dependent on. Thus they may specify a damping factor of "200 at 1kHz with a 4ohm impedance load at the amplifier output terminals". So in other words, if you put a load with an impedance of 4 ohms at 1kHz across the amplifier's output terminals and the frequency generated by the amplifier is 1kHz, the ratio between the load impedance and the amplifier's internal impedance is 200. Which means that the amplifier's internal impedance at 1kHz is 0.02ohms. The amplifier's internal impedance at 1kHz will stay the same but damping factor will fluctuate depending on the load impedance used and the wires/connectors used in the signal path. For example, if you use a driver with an impedance of 8 ohm at 1kHz instead, then the damping factor becomes 400. Conversely, if you use a driver with an impedance of 2 ohm at 1kHz, the damping factor will be 100.

For reasons that I will indicate later, the damping factor is mainly significant for amplifiers used to power sub woofers. Given that, a damping factor given at 1kHz is pretty much meaningless since sub woofers are usually limited to producing frequencies below 100Hz. How do you get around this then? Well some manufacturers publish damping factors as "greater than 200". What this means is that provided a load with a constant impedance of 4ohms across the frequency spectrum, the damping factor measured at the amplifier's output terminal is greater than 200. Which is the same as saying that the internal impedance of the amplifier will never rise above 0.02ohms from 20Hz to 20kHz. This is the best solution to the problem that I've seen so far since it specifies everything the amplifier's manufacturer can specify. The damping factor specified this way is only dependent on variables controlled by the consumer such as the driver, wire and connectors used. Usually, a damping factor of greater than 50 is considered adequate, though most high end amplifiers have a damping factor of greater than 200.

With that said, why should you care about the damping factor at all? If it is so complicated to specify, why would we want to know it in the first place? Well, the significance of the damping factor is twofold. First, and perhaps more obscure and lesser well known, the damping factor indicates the efficiency of the output device (transistors) used in the amplifier. Second, the damping factor indicates the amplifier's ability to control the motion of a driver.

The load and the output device of an amplifier makes a complete circuit and whatever current flows through the load also flows through the output device. Thus if the amplifier is putting out 2 amperes of current, then the same 2 ampere of current is flowing through the load and the output device of the amplifier. The total power dissipated in the complete circuit is then the current squared multiplied by the total impedance in the circuit. Lets assume a damping factor of 200 for a load impedance of 4ohms. Thus the amplifier's internal impedance is 0.02ohms. The total impedance in the circuit is then 4.02 ohms. Multiplying 2 squared and 4.02 together we get 16.08 watts. Of this power, 0.08 watts is dissipated by the amplifier's output device and the rest is delivered to the load. Thus about 0.5 percent of the power is wasted by the amplifier's output device. Because this percentage of wasted power is rather small compared to the overall wasted power in the whole amplifier (around 50 percent), it is rarely mentioned. But it is nonetheless indicated by the amplifier's damping factor.

The damping factor is most often used as an indication of the ability of an amplifier to control the motion of a driver. When a signal sent to a driver is suddenly stopped, the driver's cone continues moving back a forth for a short period after the signal has stopped. A driver with a cone that stops quickly is said to have a good transient response while a driver with a cone that does not stop quickly is said to have a bad transient response and thus is described as inaccurate.
I think it goes without saying that most people would prefer a driver with good transients and thus would prefer that the cone of the driver stop quickly after the source signal stops.
With tweeters and mid-bass drivers, this not a hard task since the cones of these types of drivers are relatively light and a relatively large motor structure can be used to control the motion of the cone. However, the cone of a low frequency driver is quite sizable and it is physically impractical to use a motor assembly large enough to obtain transient responses as good as that of a tweeter or a mid-bass driver. Thus low frequency drivers usually have relatively poor transient responses.
This is really not too much of a problem since humans are less sensitive to distortion in the low frequencies. In fact, THD of 3 to 6 percent from a low frequency driver is considered acceptable. Low frequency distortion only becomes objectionable when it gets close to 10 percent.
Since drivers are just electric motors, they become generators when their terminals are shorted. If you place an ammeter across the leads of a driver and push the cone up and down, you will see a current flowing through the ammeter. The higher that current is, the more difficulr the cone becomes to move. Thus, if a driver's cone is moving, the quickest way to stop it is to place a dead short across its leads.
The internal impedance of an amplifier is usually very small and in the absence of a source signal, it is like a short across the leads of the driver. The amplifiers with a higher damping factor will have a lower internal impedance so it will be closer to a short, thus the amplifier with a higher damping factor will cause the driver to stop quicker than the amplifier with a lower damping factor. Since low frequency drivers need all the help they can get to stop their cone from moving when the source signal stops, a high damping factor is desirable for an amplifier intended to power low frequency drivers. The damping factor is not as relevant when the amplifier is used to power mid-bass and tweeter drivers since those drivers already have pretty good transient response due to their relatively small cone size.

and more on the subject

Damping Factor degradation: Using super low impedance loads on an amplifier will degrade the system's damping factor (discussed in detail below). Degradation of damping factor means that the amplifier will have less "control" over the speaker system, possibly resulting in "boomy" bass response.

So, just because an amplifier has a super powerful 2 ohm rating, don't look for ways to wire up multiple speakers in order to "use" this power! Treat the 2 ohm rating as "headroom" and know that your amp has the ability to more easily handle the most difficult "normal" speaker loads that you are likely to ever encounter. If you need more power, get a second amp. Two medium powered amps are better than one monster (what if your one big amp dies? With two smaller amps at least you can still run!).

All amplifiers generate a certain amount of electrical noise. Generally, the more powerful the amplifier, the more noise. If you turn on an amplifier (with the input jacks disconnected) and listen to a speaker you can clearly hear a hissing sound. This pretty much represents the noise floor of the amplifier. For a powerful system, the noise might seem pretty obvious; however when actual music is playing the noise will be totally masked.

All electrical circuits generate a certain amount of noise. Better designs minimize the amount of noise, however no matter how good the design there will always be some. The noise is generated by the movement of electrons in the system and cannot be eliminated (unless you chill your equipment to absolute zero!). The noise floor of an amplifier by itself is usually not obviously audible in a typical car (unless you are sitting right next to a speaker). However, the remaining components in a system (preamp, equalizer, processors, etc.) each add in some noise. So, the total system noise (when no music is playing) might be objectionable. If this is a serious problem, a device called a noise gate can be used. Such a device is essentially a "squelch" which is wired in just before the power amps (or electronic crossover in multi-way systems). The device basically cuts noise from upstream components when no music is playing. Most noise gates have adjustable controls to set the threshold at which noise cut begins and also to set the amount of desired noise cut.

The noise floor of an amplifier is relatively constant, meaning it does not increase with increasing output signal (unless the amplifier has a poorly regulated power supply). In other words, the amplifier's noise floor is pretty much the same whether or not music is playing loudly or softly. So, when music is playing softly, the noise will be proportionally larger. When music is playing loudly, the noise is essentially "buried" or masked.

As stated, an amplifier with a poorly regulated power supply can create some additional noise. If the filtering of the power supply is marginal, the "smoothness" of the DC power supply voltage will be degraded when the amplifier is playing loudly. This will result in additional noise being added to the system (generally in the form of alternator whine). This type of noise isn't really part of the noise floor. Such noise is often inaudible when music is playing loudly. It can be clearly heard however when playing test tones at levels near the output limit of the amplifier (don't try this unless you are thoroughly familiar with testing practices... blown speakers will otherwise be the result!)
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