SUBS/SPEAKERS AREN'T WORKING!?!
Double Agent HT
Joined: Nov 2004
Posts: 5,518
Likes: 0
From: Installing Your Theater
Re: SUBS/SPEAKERS AREN'T WORKING!?!
That's not true. If you put amps in an enclosed area with no way for them to convection cool, you need forced airflow. Doesn't matter how they're tuned, etc. I've done more than a few installs that I designed using fans because I knew the amps would get too hot otherwise. It's easy to do and it's often impossible to do the install without them because of the heat rejection.
Class A/B amps need airflow. How they get it is half the fun.
Class A/B amps need airflow. How they get it is half the fun.
Racetracks
Joined: Nov 2002
Posts: 15,668
Likes: 0
From: How long is a piece of string?
Re: SUBS/SPEAKERS AREN'T WORKING!?!
Class D amps don't have the audio bandwidth for anything but subs, unless they're running at much higher switching frequencies than a few years ago. There are two amps in the system, one for the sub and one for other speakers, so only one could be a class D. I was talking in a fairly general sense about fans though.
Edit: I see Alpine is doing full audio bandwidth class D stuff now. Pretty cool, I was hoping that would happen sooner or later.. There are probably other brands that do too, but I have no interest in car audio anymore so I'm not going to find out.
Edit: I see Alpine is doing full audio bandwidth class D stuff now. Pretty cool, I was hoping that would happen sooner or later.. There are probably other brands that do too, but I have no interest in car audio anymore so I'm not going to find out.
Last edited by Fabrik8; Jun 24, 2009 at 02:41 PM.
supermoto or bust
Joined: Mar 2008
Posts: 8,500
Likes: 0
Re: SUBS/SPEAKERS AREN'T WORKING!?!
im not that big of a fan of having a class d for the mids and highs. class d's are meant to play hotter and normally the door speakers cant handle it for long periods of time. some can but im just sticking to class a/b.
Double Agent HT
Joined: Nov 2004
Posts: 5,518
Likes: 0
From: Installing Your Theater
Re: SUBS/SPEAKERS AREN'T WORKING!?!
Class D amps don't have the audio bandwidth for anything but subs, unless they're running at much higher switching frequencies than a few years ago. There are two amps in the system, one for the sub and one for other speakers, so only one could be a class D. I was talking in a fairly general sense about fans though.
Edit: I see Alpine is doing full audio bandwidth class D stuff now. Pretty cool, I was hoping that would happen sooner or later.. There are probably other brands that do too, but I have no interest in car audio anymore so I'm not going to find out.
Edit: I see Alpine is doing full audio bandwidth class D stuff now. Pretty cool, I was hoping that would happen sooner or later.. There are probably other brands that do too, but I have no interest in car audio anymore so I'm not going to find out.
supermoto or bust
Joined: Mar 2008
Posts: 8,500
Likes: 0
Fidel runs VBPD
Joined: Oct 2004
Posts: 2,101
Likes: 0
From: Norfolk, VA
Re: SUBS/SPEAKERS AREN'T WORKING!?!
A completely new technology for audio amplification has been evolving during the last 15-20 years that has a clear benefit over current widespread Class-A, and AB topologies. We are talking about the so-called “Class-D”. This benefit is mainly its high power efficiency. Figure 1 shows typical efficiency curves vs. Output power for Class-B and Class-D designs.
The theoretical maximum efficiency of Class-D designs is 100%, and over 90% is attainable in practice. Note that this efficiency is high from very moderate power levels up to clipping, whereas the 78% maximum in Class-B is obtained at the onset of clipping. An efficiency of less than 50% is realised in practical use with music signals. The PWM amp's high power efficiency translates into less power consumption for a given output power but, more important, it reduces heatsink requirements drastically. Anyone who has built or seen a high-powered audio amplifier has noticed that big aluminium extrusions are needed to keep the electronics relatively cool. The loading on the power transformer is also reduced by a substantial amount, allowing the use of a smaller transformer for the same power output.
These heatsinks account for an important part of the weight, cost and size of the equipment. As we go deeper in the details of this topology, we will notice that a well behaving (low distortion, full range) Class-D amplifier must operate at quite high frequencies, in the 100KHz to 1MHz range, needing very high speed power and signal devices. This has historically relegated this class to uses where full bandwidth is not required and higher distortion levels are tolerable - that is, subwoofer and industrial uses.
However, this has changed and thanks to today's faster switches, knowledge and the use of advanced feedback techniques it is possible to design very good performance Class-D amplifiers covering the whole audio band. These feature high power levels, small size and low distortion, comparable to that of good Class-AB designs. (From now on, I will refer to Class-A and AB topologies as “classical”).
Racetracks
Joined: Nov 2002
Posts: 15,668
Likes: 0
From: How long is a piece of string?
Re: SUBS/SPEAKERS AREN'T WORKING!?!
you shouldn't believe all that you hear...
A completely new technology for audio amplification has been evolving during the last 15-20 years that has a clear benefit over current widespread Class-A, and AB topologies. We are talking about the so-called “Class-D”. This benefit is mainly its high power efficiency. Figure 1 shows typical efficiency curves vs. Output power for Class-B and Class-D designs.
The theoretical maximum efficiency of Class-D designs is 100%, and over 90% is attainable in practice. Note that this efficiency is high from very moderate power levels up to clipping, whereas the 78% maximum in Class-B is obtained at the onset of clipping. An efficiency of less than 50% is realised in practical use with music signals. The PWM amp's high power efficiency translates into less power consumption for a given output power but, more important, it reduces heatsink requirements drastically. Anyone who has built or seen a high-powered audio amplifier has noticed that big aluminium extrusions are needed to keep the electronics relatively cool. The loading on the power transformer is also reduced by a substantial amount, allowing the use of a smaller transformer for the same power output.
These heatsinks account for an important part of the weight, cost and size of the equipment. As we go deeper in the details of this topology, we will notice that a well behaving (low distortion, full range) Class-D amplifier must operate at quite high frequencies, in the 100KHz to 1MHz range, needing very high speed power and signal devices. This has historically relegated this class to uses where full bandwidth is not required and higher distortion levels are tolerable - that is, subwoofer and industrial uses.
However, this has changed and thanks to today's faster switches, knowledge and the use of advanced feedback techniques it is possible to design very good performance Class-D amplifiers covering the whole audio band. These feature high power levels, small size and low distortion, comparable to that of good Class-AB designs. (From now on, I will refer to Class-A and AB topologies as “classical”).
A completely new technology for audio amplification has been evolving during the last 15-20 years that has a clear benefit over current widespread Class-A, and AB topologies. We are talking about the so-called “Class-D”. This benefit is mainly its high power efficiency. Figure 1 shows typical efficiency curves vs. Output power for Class-B and Class-D designs.
The theoretical maximum efficiency of Class-D designs is 100%, and over 90% is attainable in practice. Note that this efficiency is high from very moderate power levels up to clipping, whereas the 78% maximum in Class-B is obtained at the onset of clipping. An efficiency of less than 50% is realised in practical use with music signals. The PWM amp's high power efficiency translates into less power consumption for a given output power but, more important, it reduces heatsink requirements drastically. Anyone who has built or seen a high-powered audio amplifier has noticed that big aluminium extrusions are needed to keep the electronics relatively cool. The loading on the power transformer is also reduced by a substantial amount, allowing the use of a smaller transformer for the same power output.
These heatsinks account for an important part of the weight, cost and size of the equipment. As we go deeper in the details of this topology, we will notice that a well behaving (low distortion, full range) Class-D amplifier must operate at quite high frequencies, in the 100KHz to 1MHz range, needing very high speed power and signal devices. This has historically relegated this class to uses where full bandwidth is not required and higher distortion levels are tolerable - that is, subwoofer and industrial uses.
However, this has changed and thanks to today's faster switches, knowledge and the use of advanced feedback techniques it is possible to design very good performance Class-D amplifiers covering the whole audio band. These feature high power levels, small size and low distortion, comparable to that of good Class-AB designs. (From now on, I will refer to Class-A and AB topologies as “classical”).
http://sound.westhost.com/articles/pwm.htm
.
Last edited by Fabrik8; Jun 26, 2009 at 06:45 AM.