simple amp question

[jnolte]

Can i wire a 1 channal monoblock amp to 2 subs? Can it be bridged and whatnot? I am a little ignorant when it comes to car audio. I was thinking 2 channels 2 subs right? 1 channel 1 sub?

or can i hood 2 subs up to a 1 ch amp

any help

[KenzBenz]

whats the specs of your amp?

[99amgc43]

if your subs are 4 ohm, then connecting them together would make a 2 ohm load, which is what a monoblock amp is made for. OR if you subs are 8 ohms, that would be a 4 ohm single load, which a monoblock or 2 channel amp(bridged) can do

btw: if you buy my box and amp ill cut a lil off the price, i am being offered $450 for my set up picked up locally so far for amp, subs, box, wiring

[thmsshaun]

Yes in short you generally can but check the ohms rating of your speakers and your amp.

I have the Vibe Monobox IV 2800Watt amp

This can be loaded down to 1Ohm

4Ohm 500Watt RMS
2OHm 850Watt RMS
1Ohm 1400Watt RMS

I am running 2 Vibe 12" Black Air subs in parallel with an impedence of 4Ohms each This i Belive leaves the amp running at 2Ohms

I can connect a furthur 2 of these subs providing they are connected in parallel thus loading the amp down to 1Ohm and allowing it to release all its power.

So in short you amp needs to be able to run at 2Ohms

[sleek_benzo]

what subs do you got?? and amp??

[martattack]

What do you have, and I can tell you more about it from there. It's usually possible, but how to wire it depends on the equipment.

Martin

[pnsji]

you can hook 2 subs to 1 channel mono amp.
Please read this:
http://jlaudio.com/tutorials/wiring/index.html

[jnolte]

its problay goint to be 2 JLw3 and a Hifonics Brutus Amp

[jnolte]

Originally posted by 99amgc43
if your subs are 4 ohm, then connecting them together would make a 2 ohm load, which is what a monoblock amp is made for. OR if you subs are 8 ohms, that would be a 4 ohm single load, which a monoblock or 2 channel amp(bridged) can do

btw: if you buy my box and amp ill cut a lil off the price, i am being offered $450 for my set up picked up locally so far for amp, subs, box, wiring

how much for just the amp?

[99amgc43]

160 shipped in orginal box and everything

[jnolte]

Originally posted by 99amgc43
160 shipped in orginal box and everything

youve got mail!

[sleek_benzo]

what kind of amp is it???

[neema12]

still need wiring help?

[jnolte]

okay this is my exact setup :

http://jlaudio.com/enclosures/CVS212GW3v2.html

what amp should i get?

THis one:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=18796&item=5771180932&rd=1

OR this one:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=18797&item=5772617502&rd=1


I am kind or new to stereo and all this Ohm talk and what not is making me confused.

Im thinking since the subs are 4ohm i should get a amp that is most powerful at 4ohms? Or when i bridge it, it goes to 2 ohms?

i am most confused! Please someone tell me which amp is best and some direction

thanks alot!:cool:

[neema12]

I would not get either the Hifonics amps or the JL subs, but if you already have the subs then you want to find an amp that can push ~600 watts rms in 4 ohms. Dont buy a 2channel amp if you want to use only 1 channel, bridged power will not be as clean and healthy as a single channel amp. I owned both the bx1500 and the zx6400 Hifonics amps. I bought them at an authorized dealer so I got warrenty. Ebay sellers, reguardless if the amp is new are not authorized dealers. If you have more questions, ask. As far as the amps working with the subs, the bx1500 will work, but dont pay that price.

[jnolte]

can you suggest some proper amp models?

[pnsji]

You need an amp that can output 4 ohm as the highest. From your two choices, the first one is better since it perform better in 4 ohm.

[99amgc43]

if you have that exact set up from JL, then it is repwired for a 4 ohm single load correct??? my monoblock amp pushes 500watts rms into a 4ohm load or 900watts rms into 2ohm


in your case, it will be pushing 500watts rms and 1000 watts max which should be plently of power without worrying about blowing them out, plus it is a class D amp which means cleaner power than normal class amps.

let me know if interested, i have it all packed in the original box with manual and high elvel inputs never used.... for $10 more ill include 20 feet of streetwires brand new never used for your power and ground, (you will need a inline fuse however)

[neema12]

Before I start, this better be made a sticky for anyone looking to buy an amp. If you have more questions, ask and I will answer.


in your case, it will be pushing 500watts rms and 1000 watts max which should be plently of power without worrying about blowing them out,

This is not true. First of all, this amp pushes around 500wrms at 4ohm, around 850wrms at most during 2ohm, and about 950wrms at 1ohm. This is with a stable voltage system that is installed properly, which I doubt most people do. Max power means nothing.



plus it is a class D amp which means cleaner power than normal class amps.

Class D does not mean cleaner power than a "normal class" amp. By normal you most likley mean a class A/B amp, which is commenly seen in multichannel amps. Most people think class A/B amps are least efficent than class D. Before we discuss this, let me define both of these for you.




Class A
Class A amplifiers amplify over the whole of the input cycle. They are the usual means of implementing small-signal amplifiers. They are not very efficient—a theoretical maximum of 50% is obtainable, but for small signals, this waste of power is still extremely small, and can easily be tolerated. It is only when we need to create output powers with appreciable levels of voltage and current does Class A become problematic. In a Class A circuit, the amplifying element is biased such that the device is always conducting to some extent, and is operated over the most linear portion of its characteristic curve (known as its transfer function or transconductance curve). Because the device is always conducting, even if there is no input at all, power is wasted. This is the reason for its inefficiency.


If we wish to produce large output powers from a Class A circuit, the power wastage will become significant. For every watt delivered to the load, the amplifier itself will, at best, waste another watt. For large powers this will call for a large power supply and large heat sink to carry away the waste heat. Class A designs have largely been superseded for audio power amplifiers, though some audiophiles believe that Class A gives the best sound quality, due to it being operated in as linear a manner as possible. In addition, some aficionados prefer vacuum tube designs over transistors, for a number of reasons. One is that the characteristic curve of a valve means that distortion tends to be in the form of even harmonics, which, they claim, sound more "musical" than odd harmonics. Another is that valves use many more electrons at once than a transistor, and so statistical effects lead to a "smoother" approximation of the true waveform—see shot noise for more on this. Field-effect transistors have similar characteristics to valves, so these are found more often in high quality amplifiers than bipolar transistors. Historically, valve amplifiers often used a Class A power amplifier simply because valves are large and expensive; Many Class A design uses only a single device. Transistors are much cheaper, and so more elaborate designs that give greater efficiency but use more parts are still cost effective. A classic application for a pair of class A devices is the differential long tail pair, which is exceptionally linear, and forms the basis of many more complex circuits, including many audio amplifiers and almost all op-amps

Class B and AB
Class B amplifiers only amplify half of the input wave cycle. As such they create a large amount of distortion, but their efficiency is greatly improved. This is because the amplifying element is switched off altogether half of the time, and so cannot dissipate power. A single Class B element is rarely found in practice, though it can be used in RF power amplifiers where the distortion is unimportant. However Class C is more commonly used for this.


A practical circuit using Class B elements is the complementary pair or "push-pull" arrangement. Here, complementary devices are used to each amplify the opposite halves of the input signal, which is then recombined at the output. This arrangement gives excellent efficiency, but can suffer from the drawback that there is a small glitch at the "joins" between the two halves of the signal. This is called crossover distortion. A solution to this is to bias the devices just on, rather than off altogether when they are not in use. This is called Class AB operation. Each device is operated in a non-linear region which is only linear over half the waveform, but still conducts a small amount on the other half. Such a circuit behaves as a class A amplifier in the region where both devices are in the linear region, however the circuit cannot strictly be called class A if the signal passes outside this region, since beyond that point only one device will remain in its linear region and the transients typical of class B operation will occur. The result is that when the two halves are combined, the crossover is greatly minimised or eliminated altogether.




Class D
A class D amplifier is a power amplifier where all power devices are operated in on/off mode. Output stages such as those used in pulse generators are examples of class D amplifiers. Mostly though, the term applies to devices intended to reproduce signals with a bandwidth well below the pulse frequency. These amplifiers use pulse width modulation, pulse density modulation (sometimes referred to as pulse frequency modulation) or some combination of the two. The input signal is converted to a sequence of pulses whose averaged value is directly proportional to the amplitude of the signal at that time. The frequency of the pulses is typically ten or more times the highest frequency of interest in the input signal. The output of such an amplifier contains unwanted spectral components (ie. the pulse frequency and its harmonics) that must be removed by a passive filter. The resulting filtered signal is then an amplified replica of the input.

The main advantage of a class D amplifier is power efficiency. Because the output pulses have a fixed amplitude, the switching elements (usually MOSFETs, but valves and bipolar transistors were once used) are switched either on or off, rather than operated in linear mode. This means that very little power is dissipated by the transistors except during the very short interval between the on and off states. The wasted power is low because the instantaneous power dissipated in the transistor is the product of voltage and current, and one or the other is almost always close to zero. The lower losses permit the use of a smaller heat sink while the power supply requirements are lessened too.

Class D amplifiers can be controlled by either analogue or digital circuits. A digital controller introduces additional distortion called quantisation error caused by its conversion of the input signal to a digital value.

Class D amplifiers are widely used to control motors, and almost exclusively for small DC motors. They are also used as audio amplifiers. While class D amplifiers with excellent audio quality do exist, the relative difficulty of achieving good audio quality means that the vast majority appear in applications where quality is not a factor, such as miniature audio systems and "DVD-receivers". An early and prolific area of application is high-powered, high-fidelity subwoofer amplifiers in automobiles. Because subwoofers are generally limited to a bandwidth of no higher than 150 Hz, the switch speed for the amplifier does not have to be as high as for a full range amplifier. They have become so inexpensive that a true 1 kW of power output can be had for less than 250USD (retail). Efficiencies are in the 80% to 95% range.

Basically, people want you to think that class A/B amps are less efficent, and class D is more efficent, or delivers cleaner power, which I will get into later.

Effiency is measured by how little current the amp needs to make more power, the class is how the amp is configured internally.

This is what you should listen to...
At full load, class D is typically 3-5% more efficient than class A/B. I've had A/B's that were more efficient than class D's. Class A's are usually 20-25% efficient, class A/B's are usually 63-65% efficient, and class D is usually 65-70% efficient.

Now, why dont they list efficiency? It's because its another number that people dont understand so they may choose another amp over theirs because its 1% more efficient (its a bigger number, must be better). Now consider this, what impedance is the efficiency rated at? MMats has advertised 92% efficiency in their class D's.... congratulations, my Tru Technology H1's were 94% efficient and it was class A/B. What MMats didn't tell you is that the 92% came from using it at 4 ohms instead of the 1 it was rated at. The Tru Technology was 94% at 4 ohms when I tested it, and 71% at the 1 ohm it was rated for.

Now, Birth Sheet can be abbreviated as "BS" because thats what they are. They are rated under test conditions you wont find in a car, so you can just throw those numbers out the window.

to calculate efficiency, you'll need an RMS reading Clamp ampmeter, and a digitial multimeter..

using a test tone (either at your resonant, or pick one) burp at full power, and measure current and voltage on the outputs

P = IV where P= power in watts, I= current in amps, and V = voltage

then repeat the test while measuring current and voltage coming into the amp..

do the same P=IV, and get the wattage spec for the input

then use this formula

efficiency = (power out / power in) * 100

just for example... Cadence A7

output I = 27, V = 45 1215 watts

input I = 128 V = 13.0 1664 watts

1215 / 1664 = .730168269 and change

.730168269 * 100 = 73.01

in that situation, the Cadence A7 was 73% efficient

You can't go off of THD. THD can be rated at any given power, at any given impedance, at any given voltage. THEY DONT SAY! They can rate THD at 1 watt and rate power at 50% THD if they want (not complying with CEA-2006 standards). Though something else to remember, anything under 5% THD you probably aren't gonna hear.

So if you have a 12v source and the amplifier can only draw 50 amps (before the fuse blows) then the maximum continuous power it can produce is 600w (this is neglecting the fact that amps are not 100% efficient).

I owned the bx1500 and several other Hifonics amps. This is how to calculate the rating of that amp, in 1 ohm load.
Power (watts) = Volts * Amps

by the calculations...

13.82v x 120amp = 1658.4watts..in theory

real world...amps say get an average 65% efficiency?

1658.4watts x .65 efficiency= 1077.96 watts real world sound with a very stable 13.8v system which most people on this fourm do not have?

When you say this amp is cleaner because its a class D amp, this is false. I will explain here.

Most people will tell you this, THD and S/N are how to tell a clean sounding amp. I thought so myself when I was a rookie too. BS

Lower THD (total harmonic distortion) the better.

Higher S/N (signal to noise ratio) the better.

There isn't a standard for rating THD or S/N. That means a company can take those ratings at 1 watt @ 1khz. That isn't listening power levels, or full range. You may see that cheap chrome POS amps have a better THD and S/N rating than a known awesome sounding amp, because there is no standard. Basically what I'm getting at here is, its BS so don't bother.

Here are 2 ways to tell if its a solid, clean amp.....

1) Is the amplifier power printed on the amp?
2) Does it have a bass boost?

If you answered yes to either of these questions, its probably not too good. There are few good amps with a bass boost, and when they gotta sell you the amp by reminding you how much power it isn't doing, not good.

Chances are if you audiobahn or sony amp claim or every other cheap POS chrome amp with 11 billion watts printed on it, its got 18-24 dB of bass boost, and is over rated.

If you dont mind me asking, 99amgc43, what amp do you have for sale?
;)

[99amgc43]

the definition of your class D states "The main advantage of a class D amplifier is power efficiency"

which is why i said it has "cleaner power" than class a/b amps

i have an older sony mobile es monoblock amp for sale

its states 500watts rms into 4 ohm at 14.4 volts and 900 watts rms into a 2 ohm load at 14.4... i have a digital cap on my system and with the car on it produces 14.1-14.3 volts

right now i have a mtx 81000d amp which retails for $730 and it has a bass boost as well and I dont think its cheap at all, its pushing my 3 jl 10w6v2's very well, I had to turn down the gain because it was pushing the subs too much

[pnsji]

Class D is the easy way to get alot of power for the money. If you are really serious about sound, you should have all class A equipment and beef up your alternator and battery.

As far as sony ES goes, you are really lucky if you could get their advertise power.

Gain is a way to match the voltage from your head unit to the input for your amp. Just because you turn down the gain, that does not mean anything.

If you want to see how much your amp is producing, use a voltmeter and bench test your amp.

[99amgc43]

i thought the gain adjusts the power to the subs, so a gain turned all the way down pushes the same watts into the speakers as much as the gain turned all the way up????

[sleek_benzo]

Originally posted by 99amgc43

which is why i said it has "cleaner power" than class a/b amps



gonna have to disagree with you there.. class a/b send cleaner power than class d.. but thats my opinion..

neema12 - think you forgot class T

all in all.. it does matter what class amp you have or what kind of woofer you have.. as long as they sound good to you thats all that matters..

you could spend thousands of dollars or a few hundred.. it all just depends on you..

another question:

i need some opinion on "tube amps"

[martattack]

Originally posted by 99amgc43
the definition of your class D states "The main advantage of a class D amplifier is power efficiency"

which is why i said it has "cleaner power" than class a/b amps


Efficiency is not the same as clean power. It is the nature of class D amplifiers to focus less emphasis on certain frequency ranges. The frequency ranges that is loses are typically the higher ones. By eliminating those frequency ranges, it makes the amplifer much more efficient at delivering the lower end frequencies. When I say efficient, I mean converting the power being drawn from the vehicle's electrical system to the power being delivered to the speakers.

Since certain frequency ranges are eliminated, it is not recommended to use a Class D amplifier to power any kind of midrange speaker or higher frequency speaker. Use Class D amplifiers only for subwoofer use only!

[neema12]

Class D is the easy way to get alot of power for the money. If you are really serious about sound, you should have all class A equipment and beef up your alternator and battery.

From above...
This is what you should listen to...
At full load, class D is typically 3-5% more efficient than class A/B. I've had A/B's that were more efficient than class D's. Class A's are usually 20-25% efficient, class A/B's are usually 63-65% efficient, and class D is usually 65-70% efficient.

Now, why dont they list efficiency? It's because its another number that people dont understand so they may choose another amp over theirs because its 1% more efficient (its a bigger number, must be better). Now consider this, what impedance is the efficiency rated at? MMats has advertised 92% efficiency in their class D's.... congratulations, my Tru Technology H1's were 94% efficient and it was class A/B. What MMats didn't tell you is that the 92% came from using it at 4 ohms instead of the 1 it was rated at. The Tru Technology was 94% at 4 ohms when I tested it, and 71% at the 1 ohm it was rated for.

Now, Birth Sheet can be abbreviated as "BS" because thats what they are. They are rated under test conditions you wont find in a car, so you can just throw those numbers out the window.


As far as sony ES goes, you are really lucky if you could get their advertise power.
True


Gain is a way to match the voltage from your head unit to the input for your amp. Just because you turn down the gain, that does not mean anything.



i thought the gain adjusts the power to the subs, so a gain turned all the way down pushes the same watts into the speakers as much as the gain turned all the way up????
Take a look at this...
Article: Correctly Adjusting Gain and Crossover Controls on your Amplifiers

This article has been written to help people tune the ‘gain’ and ‘crossover’ settings on their amplifiers.

Before leaping into adjusting the settings, first you should have a basic understanding of the controls and reasons behind proper adjustments.

Abbreviations used in this article:

*EQ = equaliser
*HP = highpass
*HU = headunit
*LP = lowpass
*RMS = root mean square
*W =watts

What is a gain control?

The gain control is NOT a volume control. Turning the gain up higher and higher does not produce higher ‘full-power’ output. If an amp produces a maximum of 100WRMS per channel, increasing the gain will not yield more than this.

Better to think of the gain as a ‘sensitivity’ setting: the higher the gain, the more sensitive the amp is to the signal fed into it.

As an example, consider three gain settings: A, B, C. A is ‘low’, B is ‘medium’ and C is ‘high’. The lowest possible setting would be fully anticlockwise and highest would be fully clockwise (where the gain control is a ‘knob’ or pot).

Now let us say the HU is delivering a 2V signal via the preouts and RCA cables. With the gain at B, the amp may be producing 100WRMS per channel. If the gain is now changed to A, the amp is less sensitive; in order to produce the 100WRMS as before, the HU must now deliver a higher voltage signal, say 3V. Setting the gain to C, the amp becomes much more sensitive; it now may require only a 0.5V signal to produce 100WRMS.

The purpose of the gain setting is to match the HU preout signal-voltage with the amplifier. A HU with a higher voltage signal will require a low gain/sensitivity setting; if the HU only produces a low voltage signal, the amp would need to be more sensitive to produce the same power.

What do the voltage markings on the gain setting mean?

Some gain controls have markings with ‘voltage’ to use as a guide. These voltage settings suggest to you what RCA input voltage is required to make the amp produce full power. You’ll note that with a high gain/sensitivity setting, the marking may read 0.5V; this makes sense because the amp needs to be more sensitive to respond to a low voltage signal in order to produce full power. Whereas a low gain setting may have a marking of 4V; with such a high input voltage, the amp needs to be far less sensitive to produce full power.



neema12 - think you forgot class T

I dident mention alot of classes, I like the Visonik amps tho.


Efficiency is not the same as clean power. It is the nature of class D amplifiers to focus less emphasis on certain frequency ranges. The frequency ranges that is loses are typically the higher ones. By eliminating those frequency ranges, it makes the amplifer much more efficient at delivering the lower end frequencies. When I say efficient, I mean converting the power being drawn from the vehicle's electrical system to the power being delivered to the speakers.

Since certain frequency ranges are eliminated, it is not recommended to use a Class D amplifier to power any kind of midrange speaker or higher frequency speaker. Use Class D amplifiers only for subwoofer use only!


Well put

[99amgc43]

so doesnt turning down the gain mean that it takes a higher signal (volume) from the unit in order to get the same watts as if the gain was at the highest setting and a low volume???