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View Full Version : Advantages of mono amp as opposed to bridging



bokdaddy
03-07-2006, 10:54 PM
Hey guys, I recently got an Infinity Reference 10" sub and am looking for the best way to amp it for cheap. I've heard that the Profile amps are decent for being such a low price but I have a question. It seems like bridging and 2-channel amp would be cheaper than buying a mono amp. This is the amp I was looking at:

http://www.crutchfield.com/S-Nu4Rp7sMVbu/cgi-bin/ProdView.asp?g=120&I=489AP600

Would this be adequate or are there advantages to paying for the mono amp that I just haven't heard about?

MacLeod
03-07-2006, 11:05 PM
The only real differences would be that the Class D amp will be smaller for the given power output.

That being said, a 2 channel is always a great way to go. Theyll make just as much power at usually a much cheaper price.

neomagus00
03-07-2006, 11:21 PM
it's concievable - and i make no judgement on this one way or the other at the present time - that a mono amp will sound a little better... consider if that possibility is worth it to you... if it is, go mono, otherwise, don't bother...

MacLeod
03-07-2006, 11:30 PM
Oh thats BS (BArbara Streisand)!!

600 watts from a Class D amp will sound exactly the same from 600 watts from a Class A/B amp.

AustinKP
03-07-2006, 11:47 PM
Agreed. Especially for subs, just go with the quality* amp that is the cheapest.

*Referring to build quality. Wal-Mart amps don't put out their rated power and tend to die quickly.

Greg Peters
03-08-2006, 03:42 AM
Oh thats BS (BArbara Streisand)!!

600 watts from a Class D amp will sound exactly the same from 600 watts from a Class A/B amp.

While 600 watts may sound the same from a class A/B or a class D amplifier, the class A/B amp will produce more heat, occupy more space, and draw more current to produce those 600 watts compared to a similarly rated class D.

If you plan to run multiple amplifiers in a higher wattage system, it may be best to plan for a class D amplifier to power your subwoofers. The class D is more efficient by nature, and better suited to reproduce the extended bass frequencies (and often includes features more appropriate for powering subwoofers such as low pass x-over, subsonic filter, bass boost, EQ etc).

If you only want a modest system, many 4 channel A/B amplifiers provide low pass filters on two channels for use with a subwoofer, will bridge nicely to power a sub as well as a front stage with no problems.

If you intend to run two class A/B amplifiers in this power range- one for mids & tweeters and a second for subwoofers, you should be careful of your combined current draw. This may exceed the output of your alternator when the class A/B amplifier powering your subs is reproducing heavy bass passages, resulting in dimming headlights and strain on the electrical system due to high current consumption of amplifiers.

As a general rule, it takes a lot more amplifier power to reproduce lower frequencies compared to highs/mids at a given volume level. A class A/B amplifier powering subs will be easier to drive into thermal protection mode if playing subwoofers at high volume for extended periods.

Both types of amps have their benefits and drawbacks- it depends on what type of system you ultimately want to build, and whether or not you are willing to upgrade your vehicle's battery and alternator in the process. Personally, I'd spend the money for the class D, as it would be easier to integrate with future upgrades if you want to power the rest of your system.

PoweredByDodge
03-08-2006, 01:30 PM
i agree with Greg above.

bokdaddy
03-08-2006, 04:53 PM
Well thanks guys, as usual this forum has proved to be a great resource, I'm gonna think about it for a couple days before I make my decision. I didn't know I might have to worry about the battery and the alternator if I was to add more amps. And my next step is to finally get a four-channel amp to juice up my db series speakers, so I guess that's something I'll have to think about. Thanks again.

neomagus00
03-08-2006, 04:58 PM
despite the fact that my response was ripped a new one, i'm still curious which you'll choose (more specifically, why)... make sure you update when you make your choice!

Greg Peters
03-08-2006, 06:04 PM
despite the fact that my response was ripped a new one

No-one needs "a new one".

IMO, a class D monoblock has the potential to sound better than a class A/B amplifier when powering subs, but a lot of that depends on the features included in the amplifier you end up choosing, and whether or not your vehicle's environment really requires those features to produce the best sub-bass it possibly can.

A lot of vehicles have things which get in the way of excellent sound. Picking a devoted monoblock amplifier is probably a little easier to match correctly with the woofer you intend to power. The plus side is the specifications for that amplifier are given by the manufacturer assuming it will be reproducing only those power hungry bass notes, giving you a realistic expectation of how it will perform in your application.

Many "full range" amplifiers are spec'd with a 20hz-20khz (or better) range of output in mind, and it takes far less clean power to drive the upper ranges of that spectrum properly, within a class A/B's ideal comfort zone. If you then use a class A/B to reproduce only the lower end of the musical spectrum (20-100hz or so) with a lower efficiency speaker such as a subwoofer, the class A/B amplifier may be working much harder than the published spec's will lead you to believe. The manufacturer probably intended for you to look at the specifications with regard to a typical use of their amp, such as powering higher efficiency upper- or full-range speakers.

While it is perfectly OK to bridge a typical class A/B amplifier for use with subwoofers, unless the manufacturer gives you specifications for that use, the true behaviour and output of the amplifier may be less predictable in that application if driven hard.

exalted512
03-08-2006, 06:48 PM
If anything, a class AB would sound better than a class D. They generally have better damping factors, amongst other things that i would list if i didnt have a test in an hour.

If youre only going to power one sub, theres no doubt in my mind that i would go with a 2-channel and bridge it if youre running a 4 ohm sub. If youre running a singe "dual-4" ohm sub then i would get a monoblock and run it at 2 ohms. Or even better, a dual 2 and a 1-ohm stable monoblock amp. Why? Because of the price.

Basically, if youre running a sub, or multiple subs at 4 ohms, its more cost effective to run a 2-channel and bridge it, if youre running below that ohm load, I'd recommend a mono-block amplifier
-Cody

1996blackmax
03-08-2006, 10:14 PM
I am running two class A/B amps in my car, one is a 4ch, and the other a 2ch. I am very happy with the peformance that I get from them. My 2 channel amp has a high/low/full range selector switch, a mono/stereo/bridged select feature, 18dB bass control at 45Hz, all this tells me that it is also made to drive subwoofers. On top of this, in the owner's manual it has a section on using this amplifier for subwoofer applications.

neomagus00
03-08-2006, 10:34 PM
If anything, a class AB would sound better than a class D. They generally have better damping factors, amongst other things that i would list if i didnt have a test in an hour.
better damping factors at 4 ohms, sure, but once bridged, all that goes to $hit... i'm now curious just how different AB and D are when used for a sub...

exalted512
03-08-2006, 10:43 PM
not much of a difference, but then again when you go to an sq competition, there arent too many class d's around
-Cody

neomagus00
03-09-2006, 04:23 AM
not much of a difference, but then again when you go to an sq competition, there arent too many class d's around
-Cody
hmm... something to investigate over spring break... if i don't have some sort of work to do, i'll seriously self-destruct... sounds like a worthy research project...

Greg Peters
03-09-2006, 04:56 PM
I am running two class A/B amps in my car, one is a 4ch, and the other a 2ch. I am very happy with the peformance that I get from them. My 2 channel amp has a high/low/full range selector switch, a mono/stereo/bridged select feature, 18dB bass control at 45Hz, all this tells me that it is also made to drive subwoofers. On top of this, in the owner's manual it has a section on using this amplifier for subwoofer applications.


Yes..but those are not garden variety amplifiers- ARC makes some great stuff and the people behind it really now what they're doing.

Greg Peters
03-09-2006, 05:29 PM
not much of a difference, but then again when you go to an sq competition, there arent too many class d's around
-Cody

My previous comments were made "for the masses", a general rule of thumb. If the original question was something like "what would the ultimate sub amp for x application be", I would not be chiming in. For a drop-in type of audio upgrade, a class D is not inappropriate.

The down side with most class D amps is distortion. Making one for a full range application with low distortion is cost prohibitive, so most on the market are for subwoofer applications (usually outside of discernable hearing range compared to distortion from a tweeter). This would not lend itself to competition level amplifiers, but is good enough for people wanting good sound/bang for the buck. A quality class D amp driving a 2ohm (or even 1ohm) load can give some pretty impressive output for the money spent.

As for damping factors, a reputable amp manufacturer usually has worked out the details before putting the product out there. Many manufacturers (even Polk) do not readily list damping factors in the published specs, so you may not even have those numbers at your disposal to make an informed buying decision. A super-high damping factor can give you some very punchy bass response, but usually is directly related to the amp's price tag, too.

If competition were the goal, it would be better to run some high current monsters like Zapco or US Amps (for the dynamic range), or at least upper end amps from the quality manufacturers...combined with some top shelf speakers, of course.

Someone serious enough about audio to compete with it would not likely be put off by upgrading the vehicle electronics (or even stripping down his truck to bare metal inside for sound damping, like cody there).

1996blackmax
03-09-2006, 07:52 PM
I believe that I am serious about my car audio. I've worked through the night installing gear in my car on several ocassions. I also have no desire in competing. Not really my type of thing. The two do not have to go together.

MacLeod
03-09-2006, 08:01 PM
Id have no problem running a Class D amp at my next compy, especially if its one of these:
http://xtant.com/html/images/largePictureXtant1.1i.jpg

I am considering an amp upgrade tho. My beloved Crossfires are powerhouses but for SQ music (jazz and mostly accoustic stuff) I need power; lots and lots of power. Not big sub bass power but big dynamic power.

Kirk Proffit's Acura uses big Zapco amps and he has power to spare and his system sounds unreal.

Greg Peters
03-09-2006, 08:47 PM
I believe that I am serious about my car audio. I've worked through the night installing gear in my car on several ocassions. I also have no desire in competing. Not really my type of thing. The two do not have to go together.

Your sig says it all- high quality stuff, not to be taken lightly.

I would love to be more serious about car audio (also without the desire to compete). Without a bottomless bank account, or the time to completely gut my car for sound deadening, it'll have to wait. One piece at a time.

1996blackmax
03-09-2006, 08:57 PM
I hear you. Little by little has worked for me as well :).

exalted512
03-09-2006, 09:01 PM
ill be able to resume sound deadening tomorrow!!! yay for spring break!
-Cody

1996blackmax
03-09-2006, 11:38 PM
That reminds me, I still have to do my rear doors on my car. My buddy gave me a good amount of Dynamat when he moved. I will put it to good use :D.

AustinKP
03-10-2006, 01:35 AM
ill be able to resume sound deadening tomorrow!!! yay for spring break!
-Cody
You have a new truck, or are you still driving the same one? Also, who did you go with for dampening? SecondSkin?

exalted512
03-10-2006, 08:12 PM
sold the old one, sound deadening the new one. I dropped about a grand into sound deadening, all from second skin.
-Cody

username
09-02-2006, 04:26 PM
Oh thats BS (BArbara Streisand)!!

600 watts from a Class D amp will sound exactly the same from 600 watts from a Class A/B amp.


And I suppose two sony xplod subs will sound exactly the same as two rockford p3 12's, if the ohm rating was the same.......

if its for subs mono amps are the way to go, they are designed to handle the one way of sub freq.'s better then bridging two channels down. Think about what happens when the gain is all the way up, notice the sound distorts at lower levels? By jacking the system you also jack any signal flaws, so 4 times the seen power (bridged 2 channel to mono) is going to read more interference then a single mono 600 watt is. Do some reading, if its strictly for subs get a mono amp, thats what they are designed for.

By the way i put my money where my mouth is... i run (caps, crossovers blah blah left out) a rockford t100001bd mono (thats 1000 rms ;) and two 12'' punch power t2's.

MacLeod
09-02-2006, 06:40 PM
And I suppose two sony xplod subs will sound exactly the same as two rockford p3 12's, if the ohm rating was the same.......

If you suppose that, then youre stupid.


if its for subs mono amps are the way to go, they are designed to handle the one way of sub freq.'s better then bridging two channels down.

Subs only have one way frequencies?


Think about what happens when the gain is all the way up, notice the sound distorts at lower levels?

By cranking the gain all the way up, you push the amp into clipping which is not only pure distortion but more than double the amps rated power and a good way to blow speakers sky high! Class AB or Class D, you set the gain to max and turn up the volume, youll get clipped signals, distorted signals and blown speakers.

Bridging an amp is NOT the same thing as setting the gain all the way up.


By jacking the system you also jack any signal flaws, so 4 times the seen power (bridged 2 channel to mono) is going to read more interference then a single mono 600 watt is. Do some reading, if its strictly for subs get a mono amp, thats what they are designed for.

Maybe I should do some more reading cause I dont have a clue what youre talking about? Jacking the system? 4 times the seen power?

If an amp is stable to 4 ohms mono, itll handle the 4 ohm mono load all day long and will be as clean and pure as the wind driven snow, assuming you dont crank the gain to max.

The ONLY benefit of a Class D amp is effeciency. They will make more power with less input voltgae. Thats it. They dont play 40 Hz better than an Class AB amp. They dont handle the "one way frequencies" of sub bass better than Class AB.

And you wanna know why Class D amps arent used for mids/highs? Because they have about 3 times the distortion of a Class AB amp.

PoweredByDodge
09-02-2006, 07:03 PM
what does light sound like?

exalted512
09-02-2006, 07:36 PM
And I suppose two sony xplod subs will sound exactly the same as two rockford p3 12's, if the ohm rating was the same.......

if its for subs mono amps are the way to go, they are designed to handle the one way of sub freq.'s better then bridging two channels down. Think about what happens when the gain is all the way up, notice the sound distorts at lower levels? By jacking the system you also jack any signal flaws, so 4 times the seen power (bridged 2 channel to mono) is going to read more interference then a single mono 600 watt is. Do some reading, if its strictly for subs get a mono amp, thats what they are designed for.

By the way i put my money where my mouth is... i run (caps, crossovers blah blah left out) a rockford t100001bd mono (thats 1000 rms ;) and two 12'' punch power t2's.
i dont even know where to start...ill just leave it as you dont know what youre talking about, so please dont misinform others. By the way, fosgate doesnt make a t100001.
-Cody

MacLeod
09-02-2006, 07:43 PM
what does light sound like?

It depends. Is light a one way or two way frequency?

exalted512
09-02-2006, 08:22 PM
It depends. Is light a one way or two way frequency?
depends on if its red or blue light, and if you can bridge them to make purple
-Cody