y doesnt anybody like rockford ive got 2 12" hx2 subs powered by a 1001bd amp and i have db levels of close to 175 and spl of 145 and they sound sclean all the way threw rockford are awsome subs but u have to use a really good amp to get the best out of them i use the 1001 digital mono block amd thats 2000 watt max at 2 ohm and ive had no problems theres enough bass in my car the cars around me can feel vibrations and all ive done is dynmatted the under area of my box and got good weather stripping for the hatch and a really good custom non ported box my whole system is a kenwood deck 1001 bd amp for the 2 subs another 2 channel amp from rockfod that runs my two spekers in the fron all ive got for speakers is mids and twweters by infinity custom mounterd in the kick panels and u can hear my car clearley outside it souds perfect i admit rockford sucks for deck and speakers but for amps and subs mtx jl and alot fo other companies dont have a comparision

The show was kind of lame and worst of all
they bumped Hogans Heros for it on TV land.

huh?

Rockfords quality has really went down in the last few years as many will attest to. I agree that the hx2's will shake your brains loose. But there are other products(which sound better IMO) i would buy before i spend money on Hx2's.
Glad to here you enjoy them.

db levels and spl are the same thing...that 175 sounds awfully made up to me because in order to hit 175 with 2 12's you'll need to invest about $30k+ into installation etc

HX2s can get very very loud, but they're overpriced and have NO sq to them at all. Ive heard them in 5 different setups in two different cars with a bd1500 per sub and you cant make those woofers sound good.

also RF decks and speakers really arent that bad, infact i would say that their decks are better quality than their subs or amps. Of course i still would never own one

and saying that mtx and JL dont compare with RF amps and subs is just silly. Have you ever heard of the W7?

blyth18md is right, the quality on RF products has greatly decreased in the last few years. Back in the day they used to be the only brand to use.

Punctuation and spell check rock

I've read this post three times now and im like this

I'll give it a go......

Can't say I agree with 90% of it, but then again, that's bassed on if I understood 90% of it correctly.

I love it when people toss around terms they don't know the meaning to.

Anyway, I don't like rockford because frankly, there isn't much to like anymore. 10 years ago they had some of the best car audio stuff around, but they've fallen victim to the "marketing instead of quality" philosophy that so many other companies have had sucess with.

My friends old punch 60 will out pound my 360a2 all day long. My HE2 subs sound like a fart caught in a tin can.

i agree, the new fosgate stuff is getting worse by the minute, and COME ON, i cant stand these new amp ratings.




adam

i think the way to go is with the new upcoming companies that really need to make good products to make a name for themselves.

adire
RE
ED
blueprint
many many others

it is hard for me to spend my hard earned money on equipment whose sound has never touched my ears.
in fact, it isnt hard, it just doesnt happen
adam

ROCKFORD FOSGATE :rockon: Some of the best audio gear on the market and the planet.The older gear the all black Punch 45 75 100 150 were all good stuff.
http://members.sounddomain.com/seelo

UMMMMM, lets just say rockford 900 watt four channel amp for $179?

RMS power ??? MAX power ??? ILS power 900 watts maybee more

If Lighting Strikes (ILS) and a lighting rod must be installed pursuant to national electrical codes...lol!

a JBL 40.4 RMS amp for $225 is more like it! 40 watts RMS per channel...REAL POWER...not some fictional bs

has anyone heard of the 6000 watt JBL GTI Crown amp? And yes that is 6000 watts RMS, it has a deadly yellow electrical shock label on it to remind you that the output power will kill you! I saw it in JBL's Engineering Mayhem tour, it wasn't powered becasue the demo vehicle wasn't wired yet. This RAV-4 had the most insane fiber glass and amp racks I have ever seen btw....anyways..that's only 6000 watts output if you can power it, I'd like to see how they do that!

JL amps seem to be a win win situation, if I have the cash next time I see someone letting go of a JL 500/1 in the paper, I'm all over it. I had one in my car before it was stolen, that is a ballzy amp.

the JBL Crown hybrid amp is rated at 6000 watts but apparently its pushing 6800 rms. I dont think they've been released to the public yet but some people can get their hands on them. For the price though, you could get 5 or 6 us amps 4000x's and have four times the power...i think that JBL amp is more for audience appeal rather than reality

as for JL amps...from my experiences (1000/1 in a few installs) they're good amps that put out rated power with excellent features. Just a bit pricey i think, and a little too mainstream for me

The 6000 watt amp is on display at Discount Auto Sound at 812 S. Lynnhaven in Va Beach........Don't shop there though, I'll tell you why:

they low ball even the most experienced installers and offer everyone $6.50/hour they will pay more once they say something, but the installers will either join the ranks of suckerhood or find a job that can pay the bills in the next month.

They unlawfully conduct 'payroll deductions' from thier employees for unintentional damages to vehicles in the shop, a practice not acceptable for any automotive professional without consent...especially those with a familly to support. This shouldn't be a problem if they had the capability to train and hire all professionals in the first place.

This company can't possibly take car audio seriously, I feel bad for the real installers who work for them. The owner is a typical Virginia greedy short sited pig, don't give them business, just look at the amp


anyways.....yes that is a bad as can be amp, no surprise that it's really cranking out 6800 watts. JBL is just on of those companies, no fluff just power. there are some crazy SPL people who will wind alternators and power that beast up, it wieghs one hundred something pounds and comes in a crate. it looks just like the smaller crown series with the plexi glass to show of it's circuitry.


2000 watts MAXIMUM power.......add it up, can your electrical system even support 2000 watts even for peak notes?

any JL amp will shake that rockford into pieces, pricy but they will deliver bass in a whole new diminsion if the installer can tune it, most can't.

I'd like to see one of those US amps in real life, they look good on paper for thier price. As an electronics tech, I often see products that look great on paper, but what they can do in real life fall under a different set of rules.....ohms law to name one.



JL amps are pricy because they are precision designed to delver a solid output with a wave consisting of highs and lows only produced by high current switching output transistors. Class D baby!
:hail: D (digital) _-_--__--_--_-_-


has anyone heard of Memphis amps or something like that? They only sell them in certain states, I honestly don't know what thier quality is, but I hear they deliver some power and are very small for what they do.

i used to own 4 us amps vlx400s...the best thing about us amps products isnt their rated power because its nothing special. But they're easily modded to drop down to insane impedence levels (my amps ran at 1/4 ohm just fine) and take up to 18 volts. With the increase in voltage and the decrease in impedence you get some huge power numbers. The amps are very current hungry though thats a main concern.

class D doesnt mean the amp is digital in any way

memphis amps are pretty good quality. I got to play with some std1500s last year sometime and liked them. The make the infamous "Memphis Belle" amps the biggest of which puts out 75X4+300X1 underrated watts.

You are correct, an ability to feed an amp 18 volts and drop to .25 ohm output impedence will workout to some power....and suck up some current. Please tell me why class D amps aren't digital in any way though,




Class A : hi-fi, 100% (360*) signal reproduction
Class AB: stereo, clear enough for most people, most common
Class B: I forget at the moment but it only outputs the + or - side of the signal, SSB RF transmissions

Class C: extreem distortion, useful in RF transmitter to save power, acceptable for non-audio outputs.

Class D: Pulse Width Modulation, DC Electric motor speed controls or acceptacle for sub level amplification in the home or car, usually single channel, extreemly efficient.


even the remote wire function can be considered digital, it's like a 12v AND gate (2 input required)


Memphis Belle, that's the one I saw at Cash Converter's (pawn shop chain store) It was selling for $499, one gentleman wouldn't stop raving about it and said it would sell for $1300 new. That's about perfect power for most any reasonable application too! I'm surprized that the amp is as small as it is, they have good integrity to deliver a product and not exagerate it's presence, like...........SONY.......KENWOOD....

Rockford Fosgate has become too generic. It's like the euro-market...The only reason they do it is because they think it looks cool, when in actuallity its fugly and sounds like poopoo. Wow, sometimes I even amaze myself with my analogies!

It's ALL Alpine for me. I love thier equipment (even though I've found some components don't have as long a life as I'd like them to) and it sounds crisp as all get out. My $.02

Bruce (90RS305)

http://www.teamrocs.com/technical/pages/classd.htm

there are some class d amps in the world that are digital but they are very very rare...less than a handful of models ever made

Right from the link you yourself provided....
If you find a way to digitally amplify an analog signal, you let me know, ok?

I bought my g/f a Rockford Fosgate setup when I worked at Best Buy... only because it's (well, was if it isn't now) made in the USA! I got her this:

Rockford Fosgate 200M amp
Rockford Fosgate RFZ3812 PunchZ 12" Sub

In a Q-Logic wedge box.

Well, it was about $200 for all of it (damn I miss working there!!) but it sounds as good as my 6x9"s... I guess it isn't as great as I thought lol

"Similarly, cheaper digital class D's (such as Sony S-Master and TI's) go on to show that at practical price and complexity levels, performance is quite abysmal (better than 0.1% THD is unusual and be sure it aint just third harmonic!)"

taken from another website

all that did was call it digital. It didn't explain what makes it a digital amp. Those are still class D amps. The reason that some people call them "digital" is because of how the class D amps operate.

Instead of constantly amplifying an analog signal, a class D amp uses a power supply that can be switched on and off very fast. So rather than provide power all the time at a level below maximum output (and therefore below maximum efficiency), a power supply is switched on and off very quickly, or almost pulsed. That "full power or no power" type of switching is sometimes called digital switching. Anyway, this pulsed output is then filtered (capacitors) to reconstruct an analog sine wave, much in the same way that a digitally reconstructed audio signal is filtered to reconstruct an analog sine wave.

That still doesn't mean that it's digital amplification, at least not in the actual sense of the word. Digital amplification implies that the digital signal is amplified, then converted back into an analog signal post-amplification, which isn't what's happening.

Jim85 has it as right as can be, he even mentioned the filtering capacitors which reconstruct the wave....or just 'average it out'

I guess it depends on your definition of digital, as far as logic circuits...it probably has none of those, but the function is digital in a sense. it works much like a modem (modulator-demodulator) the incoming signal is analouge, becomes digital and then analouge again.

I will now check out that link and be schooled......

sure, the International Electrical & Electronic's Engineer's Association has an identifier for every standard out there, but D still conveniently stands for DIGITAL.

The D amp does not out put DC only, that is preposturous!
it is pieced into a full AC signal with a push-pull configuration, how would the DC voltage be made into an anolouge signal with a capacitor?

I'm a little foggy on even some basic electronics, but I know non-sense when i see it.

I give the writer an A for effort, but I think there is a descrepency in there.

60 Hz cannot make a 500 Hz frequency....unless we're talking about a frequency multiplier circuit. I think he simply has it backwards, 500 Hz is necessary to make a 60 Hz signal

for the each side of the 60Hz wave, there are many 'pulses' condensing more frequently in the time where the higher peaks are, this averages out to higher voltages. it's kind of tough to break this down with all words, so I'm not going to keep on top of this one, you would have to see the schematics and waveforms to put it all together. I'ts a shame that someone can spew out such misinformation with such authority for anyone to read.

Apparently, you don't. An a/c signal can be very easily reconstructed with a bunch of DC signals. If it couldn't be, we wouldn't have digital technology. We wouldn't have cds. Have you ever heard of "sampling"? You can put together an analog sine wave with a series of finite DC signals, one after the other, of varying amplitude.
Here's a pic:

Let's say that the red line is your analog AC signal.

Now, let's see how we can make that AC signal with a bunch of DC signals.

Every one of those green bars represents a short-term DC voltage, each one with an amplitude closest to what that AC signal needs at that particular moment in time. That choppy reproduction of an AC signal is then fed through a capacitor which smooths it out, making it virtually identical to the original analog signal that it's designed to represent.

Yes Virginia, you can make an AC signal out of DC. That class D amp is simply making a whole bunch of DC signals (i.e. the green bars) that are filtered and sent directly to your subwoofer.

Anyway, what makes a cd a "digital" media isn't so much the method of reconstructing the sine wave, but the fact that each individual DC voltage (44,100 per second) is represented by a 16 bit digital number. THAT is what makes cd a digital media. THAT is also why a class D amp is not truely a "digital" amp. It just happens to construct the sine wave in much the same way that a cd does.

All I have to say is, damn Jim... you never cease to amaze me with your knowledge on electronics! You should be rich or something lol :hail:

Nice grafix and thanks for the refresher!

But as you mentioned yourself, those DC pulses which occur 44,100/sec (depending on the circuit) at 65,536 different DC voltages end up being an AC signal even within the second in which it was sampled. So it's not even a DC output long enough to be concerned with. Even analouge amps start with DC voltage and manipulate it into an AC signal across the load.

If you can prove that this sampling technology is what the class D amps actually use, then I will give you more credit. For the time being, I'm having trouble understanding why an engineer would want such a complex process used in high powered cicuitry, it seems so much more inefficient to me. It's different when it is my Sony discman turning lands and pits into audible music with milliwatts of power inside of a microprocessor, it seems completely impractical when you want to digitally similate a 1000 watt audio sine wave.

Sure, there are some rationalizations as to why class D doesn't mean it's D for Digital. It may not have been intended, but it's been adopted. It's like the BNC conector, no one quite knows what that stands for, nor can they trace it back. A true class D pre-filter output looks nothing like those green bars. That graph looks more like a Vermont cow pasture than any kind of a frequency shifting square wave I've ever seen.



And What does VA have do do with anything? I live here because I was in the Navy, I just don't like snow shoveling much, so I haven't returned home to NH.....see ya later

A power supply is most efficient at full power. A class D amp has the power supply on at full power, or off. Nowhere inbetween. Comparing it to the sampling of a cd is the closest way to describe it without going ***-deep into electronic babble, but it's not quite how it works. The amount of power needed to properly reproduce the amplitude of the sine wave isn't being made by the amplitude of the output signal from the power supply, but instead is being produced by the pulse width. Once you filter it, varying the pulse width of the signal has pretty much the same effect as varying the amplitude.

Clear as mud?

I'm going to let somebody else explain it, since he'll do a better job than I can. These images don't show up well on a light colored background, so here's a link to the original:
http://www.soundillusions.net/module...howpage&pid=96

Here's a cut & paste from soundillusions.net:

OK, now to the point. A class 'D' amplifier, which may also be known as a switching amplifier or a digital amplifier, utilizes output transistors which are either completely turned on or completely turned off (they're operating in switch mode). This means that when the transistors are conducting (switched on) there is virtually no voltage across the transistor and when there is a significant voltage across the transistor (switched off), there is no current flowing through the transistor. This is very similar to the operation of a switching power supply which is very efficient.


Output transistor switching:

In the diagram below, there are 3 waveforms. Point 'X' is the point where the transistor would be fully 'on', it would be conducting the full power supply voltage.This is the same as taking a piece of wire and connected the rail voltage to the speaker output of the amplifier. Point 'Y' shows that the transistor is fully 'off' and the output voltage is effectively 0 volts. This is the same as completely disconnecting the speaker from the amplifier. The 'duty cycle' of waveform 'A' is approximately 10%. If you averaged the voltage over time, the effective output voltage would be approximately 10% of the power supply voltage. Waveform 'B' has a 50% duty cycle. Waveform 'C' has a 90% duty cycle.

Note:
This diagram (below) shows the effective D.C. output from the respective waveform. Please keep in mind that the effective output voltage is represented as it would be while there isa 'load' on the amplifier's output transistors. If there were no load, the output voltage would stay at the full power supply voltage because nothing would pull the voltage back toward the reference (ground).

Averaged DC voltage:
You should notice that the longer the output transistors are 'on', the higher the effective output voltage. From a purely mathematical stand point, the output of the top waveform is at 100% of the supply's output voltage for 10% of the time and at 0% (0 volts) for 90% of the time. If we assume that the amplifier has a rail voltage of 40 volts, the output is at 40 volts for 10% of the time and at 0 volts for 90% of the time. This would give you ((10*40)+(90*0))/100 or 4 volts of average output voltage.




In the diagram below, waveform 'A' is the pulse width modulated portion of an audio signal. Notice that it switches between the yellow reference line (ground) to the rail voltage (white line).




Waveform 'B' shows how the voltage is stepped up as the width (time on) of the pulse increases. This part of the signal is not really present at any point in the amplifier. It is simply included for clarity. You should notice how the effective voltage is stepped up as the pulse width increases.


Waveform 'C' is a portion of the sine wave output signal, after passing through a low pass filter. Keep in mind that the pulses are a high frequency square wave, it may be as high as 500,000 hertz. A low pass filter which will allow a 20,000 hertz signal to pass (the highest frequency needed to reproduce the audio spectrum) will have virtually no effect on the audio output signal and will completely filter out the switching pulses.




In the diagram below, notice the circle on the sine wave at the bottom of the drawing. It shows the portion of the sinewave that is being reproduced in the example.

I believe I've read that article before, good stuff.

Looks like I woke you up Jim! Now you are making perfect sense! No need to read that artical at this time, I'm familliar with PWM.

An electronics discussion is like a flower garden...it must have variety and color and grow into a beuatiful boque of confusion for anyone one else besides us reading this.




Thanks, us electronics techs can always use more pay!

I was making sense before... I just didn't go into such depth.

I tend to take things very literally when it comes to electronics, I like to just get to the point. Too me, it's more confusing to leave stuff out and go of course with explaination.

Alot of people here in these boards like to talk with authority but don't seem to have real life experience. I think you obviously know what's up.

In conclusion....i will have to say the same thing you said about rockford....they are just weening of of thier name. it is a 'legend in the streets' and marketing propaganda that keep these kinds of things going.