# Class AB or Class D amplifier for subwoofer



## kaihoong (Dec 30, 2019)

Its it any different between class AB and D amplifier for 12'' subwoofer. What is the pros and cons?

My subwoofer provide 250w RMS, should I get a 4 channel amp use 2 ch bridged(220w rms) at 4 ohm or get a monoblock with 250w rms at 4 ohm output. Which is better, if get 4channel amplifier, I still can use for 2 channel more. 

Which is better way for subwoofer, class AB or D amp and bridged 2 channel output or monoblock?


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## Holmz (Jul 12, 2017)

At that's power level it is a wash.
At high power, even I would go Class-D.

So if you have an amp already, or find a cheap used one, then there should be a few at those power levels... in either Class-AB or D.
But if you are buying a the new Class-D makes sense, and probably somewhat higher power also makes sense.

Note: I have a 300W ([email protected]) Class-AB as a sub amp.


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## kaihoong (Dec 30, 2019)

Holmz said:


> At that's power level it is a wash.
> At high power, even I would go Class-D.
> 
> So if you have an amp already, or find a cheap used one, then there should be a few at those power levels... in either Class-AB or D.
> ...


that mean for class D monoblock for subwoofer is more powerfull and reliable


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## Bchester6 (Jan 15, 2020)

Class D is more friendly on your electrical system at higher power but if I was only looking to provide 250-300 watts as you're intending to do then an A/b amp would do just fine.


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## kaihoong (Dec 30, 2019)

Bchester6 said:


> Class D is more friendly on your electrical system at higher power but if I was only looking to provide 250-300 watts as you're intending to do then an A/b amp would do just fine.


I have a 4 ch amp but will use for 2 way front stage, I think I will go for class D monoblock for trunk subwoofer


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## kaihoong (Dec 30, 2019)

One more questions, I saw some person load 4ohm to 2ohm and get high watt for subwoofer. What is the different betweem 4ohm and 2ohm


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## syc0path (Jan 23, 2013)

2ohm speakers have lower resistance than 4ohm speakers, so they draw more power from the amp. That's normally a good thing, especially for subs, but only if the amp can handle the ohm load. There a lots of different ways to wire subwoofers, and each will affect the ohm load at the amp.


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## kaihoong (Dec 30, 2019)

syc0path said:


> 2ohm speakers have lower resistance than 4ohm speakers, so they draw more power from the amp. That's normally a good thing, especially for subs, but only if the amp can handle the ohm load. There a lots of different ways to wire subwoofers, and each will affect the ohm load at the amp.


This is the spec of amp that I plan to buy, how good is the subwoofer when running 2ohm


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## gijoe (Mar 25, 2008)

What subwoofer is it? You can't simply pick and choose if you want 4 ohms or 2 ohms, it will depend on the number of voice coils, and their impedance.


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## Holmz (Jul 12, 2017)

kaihoong said:


> that mean for class D monoblock for subwoofer is more powerfull and reliable


^Assuming there should be a question mark at the end?^

A 300w Class-AB is more puwerful than a 250W Class-D.
A 1000w Class-D would be more powerful than a 300w Class-A.

A content arguement for reliability can be made for a 15 year old Class-AB that works.

If you are headed to a new amp, then I would be looking at 500-1kW class-D

If you only need 250W, and have an existing amp or willing to get a used amp, then Class-AB makes sense. I would think a few people have lower power sub amps for sale?



kaihoong said:


> This is the spec of amp that I plan to buy, how good is the subwoofer when running 2ohm


That will make 400w into 2-ohms and 200w into 4-ohms...
And then at 4-ohms, the old 300w Class-AB has Personally I would rather have a 2x 4-ohm VC wired in parallel to 2-ohms... or run a 4-ohm sub.
But does it matter?


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## syc0path (Jan 23, 2013)

I think this is getting too complicated for a simple question. I don't think he cares about the sonic differences between Class AB and Class D.

Generally speaking, a Class D monoblock is the best choice for subs. If u have enough space in your vehicle, get 2 4ohm subs and wire them for a 2ohm load. That's how my system is set up. If u only want to run 1 sub, then get a DVC sub with 4ohm coils. The coils can then be wired to create a 2ohm load.


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## dgage (Oct 1, 2013)

As people have said, class D is more power efficient, which means it won’t waste as much electricity as heat like a class A/B will. And class D can be smaller while still putting out good power.

But 250w is a small amp for a subwoofer, which is why it doesn’t matter much whether you go with class A/B or D.

if you were to get a high excursion subwoofer (>20mm) then I’d suggest more power but for a subwoofer under 20mm, 250w is a little low but should work fine.


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## Bchester6 (Jan 15, 2020)

How about this.. If you decide to go with a 2 ohm load get a Class D. If you go with a 4-ohm final load get a Ab amplifier.


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## kaihoong (Dec 30, 2019)

gijoe said:


> What subwoofer is it? You can't simply pick and choose if you want 4 ohms or 2 ohms, it will depend on the number of voice coils, and their impedance.


My sub is mohawk classic mc.124


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## kaihoong (Dec 30, 2019)

Holmz said:


> ^Assuming there should be a question mark at the end?^
> 
> A 300w Class-AB is more puwerful than a 250W Class-D.
> A 1000w Class-D would be more powerful than a 300w Class-A.
> ...


I didnt know my specs of subwoofer since I was keep for more than 5 year, but I thinks it was 200-300w rms at 4ohm. 
I have a 4 channel AB amp for my front stage with 4x70rms, 2x220 bridged @4ohm.

Btw, what is the different between 4ohm and 2ohm, it is good? How to hook up


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## kaihoong (Dec 30, 2019)

syc0path said:


> I think this is getting too complicated for a simple question. I don't think he cares about the sonic differences between Class AB and Class D.
> 
> Generally speaking, a Class D monoblock is the best choice for subs. If u have enough space in your vehicle, get 2 4ohm subs and wire them for a 2ohm load. That's how my system is set up. If u only want to run 1 sub, then get a DVC sub with 4ohm coils. The coils can then be wired to create a 2ohm load.


Ya, I want to run one sub only. Which is the best way for I run it and how it hook up


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## kaihoong (Dec 30, 2019)

Bchester6 said:


> How about this.. If you decide to go with a 2 ohm load get a Class D. If you go with a 4-ohm final load get a Ab amplifier.


Is it 2ohm sound will be better?


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## dgage (Oct 1, 2013)

kaihoong said:


> mohawk classic mc.124


Looks like that is a dual 4 ohm sub with dual voicecoil. You have two options for wiring it if that is indeed the correct configuration; 2 ohms or 8 ohms. If those are the choices, definitely wire it to 2 ohms. Look at Crutchfield subwoofer wiring diagrams to get the proper way to wire your sub to the amp.


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## Holmz (Jul 12, 2017)

kaihoong said:


> Is it 2ohm sound will be better?


How are you defining better?
Loudness?
Distortion?
Something else?

They should about the in 1, 2 or 4 ohm.
Inthoery 4 or 8'ohm could sound better, but theory says it is still almost nothing one can hear.


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## kaihoong (Dec 30, 2019)

Holmz said:


> How are you defining better?
> Loudness?
> Distortion?
> Something else?
> ...


bass beat could be more deep, because I notice that when put a single sub in trunk at a sedan car, normally will listen bass is slow from rear


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## kaihoong (Dec 30, 2019)

dgage said:


> Looks like that is a dual 4 ohm sub with dual voicecoil. You have two options for wiring it if that is indeed the correct configuration; 2 ohms or 8 ohms. If those are the choices, definitely wire it to 2 ohms. Look at Crutchfield subwoofer wiring diagrams to get the proper way to wire your sub to the amp.


I am not sure it double coil or single, can u take a look to my photo


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## Holmz (Jul 12, 2017)

kaihoong said:


> bass beat could be more deep, because I notice that when put a single sub in trunk at a sedan car, normally will listen bass is slow from rear


I don't think 1-ohm is slower or faster than 8-ohm, and 2 and 4 are somewhere in between.
I don't think impedance affects the speed of sound.


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## kaihoong (Dec 30, 2019)

Holmz said:


> I don't think 1-ohm is slower or faster than 8-ohm, and 2 and 4 are somewhere in between.
> I don't think impedance affects the speed of sound.


I thinks my word make u miss understanding. I mean that I would prefer the bass enough stronger when going to driver side


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## Holmz (Jul 12, 2017)

It could also be that the bass is late...
Which needs TA on the other channels to even out the race.

Too quiet, could mean it needs more power or a different box.

Putting a 4-ohm sub on a brand new 1-ohm amp rated at 10000w will yield 250w. You can do as good, or better, with an old class-AB rated at 250W or more into 4-ohms..


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## dgage (Oct 1, 2013)

kaihoong said:


> I am not sure it double coil or single, can u take a look to my photo


Is that the only pair of speaker connections? If so, then it is a single voicecoil. You’d have to test with a multimeter to determine the impedance (2, 4?). Use method 1 with a multimeter to determine the rough impedance.









How to Measure Speaker Impedance (with Pictures) - wikiHow


Speaker impedance is a measure of a speaker's resistance to an alternating current. The lower the impedance, the more current the speakers will draw from the amplifier. If impedance is too high for your amplifier, the volume and dynamic...




www.wikihow.com





2 or 4 ohm doesn’t matter so much. You need to match the sub to the amp and make sure the amp puts out the power you want at whatever impedance the subwoofer is.


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## Holmz (Jul 12, 2017)

dgage said:


> ...
> 2 or 4 ohm doesn’t matter so much. You need to match the sub to the amp and make sure the amp puts out the power you want at whatever impedance the subwoofer is.


Yeah but...
For instance my 300w class-AB is rated 500W into 2 ohms.

That 1kW amp mentiomed way earlier should have the rating go down to 500w at 2-ohm and at 4-ohm it should be down to 250W.

I think that the specific amp he needs is dependent on what the impeedence of his sub is?
(Which you question also drives at)


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## kaihoong (Dec 30, 2019)

dgage said:


> Is that the only pair of speaker connections? If so, then it is a single voicecoil. You’d have to test with a multimeter to determine the impedance (2, 4?). Use method 1 with a multimeter to determine the rough impedance.
> 
> 
> 
> ...











Take a look here, have 2 pair connection. 

Mohawk "Classic" (MC-124)
Woofer size: 30cm (12")
Impendance: Dual 4 Ohm
Power handling capacity: 360watts rms
Frequency Response: 30 Hz - 3 kHz
Sensitivity: 86 /- 2dB

This is actual specs from internet. That way I want to ask for suitable amp to match this subwoofer. I have two subwoofer but I plan to use one only for saving place in trunk


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## kaihoong (Dec 30, 2019)

Holmz said:


> Yeah but...
> For instance my 300w class-AB is rated 500W into 2 ohms.
> 
> That 1kW amp mentiomed way earlier should have the rating go down to 500w at 2-ohm and at 4-ohm it should be down to 250W.
> ...


How was you justify the amp watt, looking at RMS watt or Peak watt. I am finding a suitable amp to match this sub


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## Holmz (Jul 12, 2017)

kaihoong said:


> How was you justify the amp watt, looking at RMS watt or Peak watt. I am finding a suitable amp to match this sub


That is a good question...
People run 100-200w up to thousands.
It totally depends on the volume you and SPL you want. Too little power and it is easy to clip and send a lot of DC to the sub, so more power is considered safer.

Personally I would be looking at 500w or more at 2-ohm (if it is a dual 4-ohm and running in parallel). Or a 250w+ 2 or 4 ohm used amp, if you are not playing it too loud.

But I am really not the right one to ask, so it is more of an opinion.


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## kaihoong (Dec 30, 2019)

Holmz said:


> That is a good question...
> People run 100-200w up to thousands.
> It totally depends on the volume you and SPL you want. Too little power and it is easy to clip and send a lot of DC to the sub, so more power is considered safer.
> 
> ...


That mean I run dual coil 4ohm subwoofer in parrallel series can get 2ohm output. So that, with the specs of my sub is 360w RMS then when I run 2ohm should get a amp that can provide more than 360w rms in 2ohm is more safer right. 

Anyhow, thanks for your opinion.


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## Bchester6 (Jan 15, 2020)

Get a mono class D amp that does 400-500 watts at 2 ohm and call it good. Set your gains correctly and you won't have any issues. If you want louder than go with a ported enclosure or hook up the other one.


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## kaihoong (Dec 30, 2019)

Bchester6 said:


> Get a mono class D amp that does 400-500 watts at 2 ohm and call it good. Set your gains correctly and you won't have any issues. If you want louder than go with a ported enclosure or hook up the other one.


Great idea. I will try to get a 500w at 2ohm mono amp


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## Holmz (Jul 12, 2017)

Bchester6 said:


> Get a mono class D amp that does 400-500 watts at 2 ohm and call it good. Set your gains correctly and you won't have any issues. If you want louder than go with a ported enclosure or hook up the other one.


If he did want to hook up the second sub, does he then need an amp with 800-1000w at 2-ohms?


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## sqshoestring (Jun 19, 2007)

I agree I would always buy a class D for subs but under around 300rms it doesn't really matter. 300rms does not take enough power to affect a typical car much, but larger amps will. A sub is going to notice the least what type of amp is on it, and so are you. While high side amps can sound different and run what you like. I run a class D on everything right now but have some class AB I would use no problem on highs and mids.

Your sub determines what ohms it has, what power it can handle, and you can series or parallel dual voice coils to half or double the ohms. Your amp can make its rated power into the ohms its rated for.


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