I have read that Class AB amps produce better bass notes tnan Class D's. Why is that? I know of the effiency factor but what about cleaner notes between the two?
Replies (12)
UKinstaller on 12/15/2004 19:32:09
i really haven't heard too much about that. i know that class d is all about raw power, so i don't see why they wouldn't be as loud on the bass. somebody else on here will probably be able to respond to that. do you have a specific setup in mind or are you just curious??
-UK
SeJae on 12/15/2004 19:58:08
Well it's a little of both. I read it on the ecoustics.com forum and I have a Hifonics BX100D and my friend has a 300 watt amp (i dont know what) with a ported enclosure and it hits twice as hard.
swez on 12/15/2004 20:27:47
Class D is not a new idea. It was developed back in the 1950's or so. It uses high speed switching power circuits (high efficiency) to reproduce low frequency bass notes. Most Class D's are good up to about 300 Hz.
Class A/B amps are now typically high speed mosfets amps. They are very clean signals in the whole audio frequency spectrum, but are much less efficient in power. (typ. 50-60%)
If you took a Class D amp and a Class A/B amp, gave it a bass tone sine wave of say 50 Hz., and compared the two on a 2 channel Osciloscope, you might be able to detect minor variations off the Class D amp VS the Class A/B amp. However, to the human ear, most cannot hear any audible differences.
But, if you measured the wattage (power) draw from each amp at the same SPL, the power consumption of the Class D amp would be notably less.
Swez
SeJae on 12/15/2004 20:37:09
I have also heard that Class D's actually run at ~60 to 70% effiency @ it's lowest impedance. Is this true?
swez on 12/15/2004 20:41:55
That may be true in some designs. But in most bass engines that use Class D amps, they are pretty close to 90% efficiency.
A little comparative reseach would give you a good grasp on what brands are very efficient (JBL is ~89%) and ones that are not as efficient.
Swez
SeJae on 12/16/2004 15:37:21
Well, I looked at Elemental Designs 9.1 and it's specs read the effiency rate is 68% and I know ED isnt BS. Also, I looked at the old Memphis amps and their effiency ratings were like 64 or 70%. And that is a recomended brand of amp.
uochronos on 12/16/2004 18:13:07
ED is also a fairly new amp company.. they make good amps but dont haev the tech that alot of the ones who have been doing it for decades do...
JBL
Phoenix gold
JL Audio
Alpine
all make some very effiecient class D amps 85-90% effiecient also the new class T amps can be as much as 95% effiecient.
Chronos
SeJae on 12/16/2004 18:32:32
I remember you having a Avionixx 1200.2. And how's that working for you? But what are some other name brands that carry the high effiency ratings, thanx...
uochronos on 12/16/2004 18:39:39
ya i have a Avionixx 1200.2 AXT its a great amp... only running it at half power though around 600watts. i have had no problems with it though.... and it runs great. very pleased with it,...
i would think just about any company that is higher end and has been around for awhile would have good ratings... i know the ones i listed all have good efficiency ratings on most amps but i havent looked into others.
Chronos
swez on 12/16/2004 18:44:21
OK, you have made a good point.
To determine efficiency rating of an amp, we power coming out and divide by power consumed. That is the efficiency rating. But to do this correctly, we have to measure the Voltage x Current (ExI) to get power in watts. That also accounts for what load the amp is running too. Efficiency is output watts/input watts.
Power output: 100 watts @ 2 ohm load (nominal)
JBL BP-300.1 Amp
Measured output: (extrapolated)
Ohms = 2
Volts = sq rt P x R= 24.49 volts AC
Current = Volts/R = 12.24 amperes
Power = 300 watts
Voltage in:
Volts = 12.9 volts DC (specs)
Current draw: 28.5 A @ full power (max draw)
Watts = E x I = 12.9 x 28.5 = 367.65 watts (consumed)
Eff rating = 300/367.65 = 0.816 = ~82%
Note: These are extrapolated values. The actual measurments of voltage and current output will change at various frequencies, when we measure voltage off the sub coils.
Here, we hypothetically used a non-inductive resistor that does not change value (like a speaker will) and a constant input signal (50 Hz, O VU) from a signal generator, the resultant voltage and current numbers will be different using a sub as the load. The actual output watts to the sub will be lower as inductive resistance changes with frequency.
Finally, we know the new CES-2006 specs rate amp power off a 14.4 volt input source. That changes the actual output ratings to a higher number. (less current draw at higher voltages, same watts rating) However, if output voltage goes up and current remains constant, we have a larger RMS output to the load
In this case, 14.4 volts x 28.5 amperes = 410.4 watts (~10.4% increase of power consumed at this voltage level) The output watts will also go up in a predictable manner, based on amp efficiency ratings.
Swez
PS JBL has under-rated the BP series based on 12.9 volts input. As we increase input voltage, maintain same load and current draw, the output watts will be higher in proportion to new voltage and efficiency ratings.
SeJae on 12/16/2004 18:44:27
Just trying to narrow it down. I would like to find one that is in the 250 to 300 dollar range. And I want to make it a worth while deal that will last for a long time, if you know what Im saying.
swez on 12/16/2004 18:50:20
Sure, we all try to do the most with how much we have to spend. Just realize that you will generally get more RMS watts per dollar spent, using a Class D or T amp. Less circuits used in both cases, compared to Class A/B amps (2 channel VS Mono) That translates to more bang for the buck when we shop well.
Good luck!
Swez
Replies (12)
UKinstaller on 12/15/2004 19:32:09
i really haven't heard too much about that. i know that class d is all about raw power, so i don't see why they wouldn't be as loud on the bass. somebody else on here will probably be able to respond to that. do you have a specific setup in mind or are you just curious??
-UK
SeJae on 12/15/2004 19:58:08
Well it's a little of both. I read it on the ecoustics.com forum and I have a Hifonics BX100D and my friend has a 300 watt amp (i dont know what) with a ported enclosure and it hits twice as hard.
swez on 12/15/2004 20:27:47
Class D is not a new idea. It was developed back in the 1950's or so. It uses high speed switching power circuits (high efficiency) to reproduce low frequency bass notes. Most Class D's are good up to about 300 Hz.
Class A/B amps are now typically high speed mosfets amps. They are very clean signals in the whole audio frequency spectrum, but are much less efficient in power. (typ. 50-60%)
If you took a Class D amp and a Class A/B amp, gave it a bass tone sine wave of say 50 Hz., and compared the two on a 2 channel Osciloscope, you might be able to detect minor variations off the Class D amp VS the Class A/B amp. However, to the human ear, most cannot hear any audible differences.
But, if you measured the wattage (power) draw from each amp at the same SPL, the power consumption of the Class D amp would be notably less.
Swez
SeJae on 12/15/2004 20:37:09
I have also heard that Class D's actually run at ~60 to 70% effiency @ it's lowest impedance. Is this true?
swez on 12/15/2004 20:41:55
That may be true in some designs. But in most bass engines that use Class D amps, they are pretty close to 90% efficiency.
A little comparative reseach would give you a good grasp on what brands are very efficient (JBL is ~89%) and ones that are not as efficient.
Swez
SeJae on 12/16/2004 15:37:21
Well, I looked at Elemental Designs 9.1 and it's specs read the effiency rate is 68% and I know ED isnt BS. Also, I looked at the old Memphis amps and their effiency ratings were like 64 or 70%. And that is a recomended brand of amp.
uochronos on 12/16/2004 18:13:07
ED is also a fairly new amp company.. they make good amps but dont haev the tech that alot of the ones who have been doing it for decades do...
JBL
Phoenix gold
JL Audio
Alpine
all make some very effiecient class D amps 85-90% effiecient also the new class T amps can be as much as 95% effiecient.
Chronos
SeJae on 12/16/2004 18:32:32
I remember you having a Avionixx 1200.2. And how's that working for you? But what are some other name brands that carry the high effiency ratings, thanx...
uochronos on 12/16/2004 18:39:39
ya i have a Avionixx 1200.2 AXT its a great amp... only running it at half power though around 600watts. i have had no problems with it though.... and it runs great. very pleased with it,...
i would think just about any company that is higher end and has been around for awhile would have good ratings... i know the ones i listed all have good efficiency ratings on most amps but i havent looked into others.
Chronos
swez on 12/16/2004 18:44:21
OK, you have made a good point.
To determine efficiency rating of an amp, we power coming out and divide by power consumed. That is the efficiency rating. But to do this correctly, we have to measure the Voltage x Current (ExI) to get power in watts. That also accounts for what load the amp is running too. Efficiency is output watts/input watts.
Power output: 100 watts @ 2 ohm load (nominal)
JBL BP-300.1 Amp
Measured output: (extrapolated)
Ohms = 2
Volts = sq rt P x R= 24.49 volts AC
Current = Volts/R = 12.24 amperes
Power = 300 watts
Voltage in:
Volts = 12.9 volts DC (specs)
Current draw: 28.5 A @ full power (max draw)
Watts = E x I = 12.9 x 28.5 = 367.65 watts (consumed)
Eff rating = 300/367.65 = 0.816 = ~82%
Note: These are extrapolated values. The actual measurments of voltage and current output will change at various frequencies, when we measure voltage off the sub coils.
Here, we hypothetically used a non-inductive resistor that does not change value (like a speaker will) and a constant input signal (50 Hz, O VU) from a signal generator, the resultant voltage and current numbers will be different using a sub as the load. The actual output watts to the sub will be lower as inductive resistance changes with frequency.
Finally, we know the new CES-2006 specs rate amp power off a 14.4 volt input source. That changes the actual output ratings to a higher number. (less current draw at higher voltages, same watts rating) However, if output voltage goes up and current remains constant, we have a larger RMS output to the load
In this case, 14.4 volts x 28.5 amperes = 410.4 watts (~10.4% increase of power consumed at this voltage level) The output watts will also go up in a predictable manner, based on amp efficiency ratings.
Swez
PS JBL has under-rated the BP series based on 12.9 volts input. As we increase input voltage, maintain same load and current draw, the output watts will be higher in proportion to new voltage and efficiency ratings.
SeJae on 12/16/2004 18:44:27
Just trying to narrow it down. I would like to find one that is in the 250 to 300 dollar range. And I want to make it a worth while deal that will last for a long time, if you know what Im saying.
swez on 12/16/2004 18:50:20
Sure, we all try to do the most with how much we have to spend. Just realize that you will generally get more RMS watts per dollar spent, using a Class D or T amp. Less circuits used in both cases, compared to Class A/B amps (2 channel VS Mono) That translates to more bang for the buck when we shop well.
Good luck!
Swez
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