Richard Rajchel wrote on Tue, 05 February 2008 16:11 |
One last thing about "punchy" bass. What the heck does that mean in reality? Most people, including a lot of engineers think to get a great kick drum sound you need subs that go to 20Hz flat(OK I'm exaggerating a little), but that "kick in the chest" feeling is usually in the 60-80Hz range, and in all actuallity the first harmonic of 120-160Hz is where most of that feel comes from. you can EQ the crap out of a kick to get it to feel where ever you want I suppose, and kick drums obviously get tuned different and can be as big as a house or smaller than most floor toms, but this dream that you need to go super low to feel the kick in a live sound application is just flat out a lie. Compressed recordings are a completely different animal, so if you're a DJ don't listen to me...heh.
|
To this I agree. For me QSC 3602s dont get it for low frequency use below 100hz. Mine shut down under low voltage conditions, generate tremendous amounts of heat and my subs don't respond as well as they do using QSC 4050HDs. I'm not going to perform any analysis to prove my point to myself or anyone else. The 4050 has more in reserve than the 3602 and runs better under less than perfect conditions even though the specs are almost identical. However, if I roll the specs up and put the specs for the 4050 in one ear and the the specs for the 3602 in the other I don't hear any difference. But, when I pull that paper out of my ears and listen to them side by side the difference is night and day.
To be kind though, the 3602 is a perfect amp (IMO) for a JBL SRX725 (with that extra 15" speaker helping to reproduce the in the 100-160hz range.)
I read the statement linear in a response. By default power amplifiers are all linear. The job of a power amplifier used for radio, sound, etc. is to faithfully reproduce the input signal at an amplified (larger) level, be it 10, 100, 1000 times larger or more. I tend to think that class of service is what the post was meant to state, examples below as applied to ham radio. The same applies to audio;
The class A amplifiers are very inefficient, they can never have an efficiency better than 50%. The semiconductor or valve conducts throughout the entire RF cycle. The mean anode current for a valve should be set to the middle of the linear section of the curve of the anode current vs grid bias potential.
Class B amplifiers are more efficient, they can be 60 to 65% efficient. The semiconductor or vacuum tube conducts through half the RF cycle.
Class AB1 is where the grid is more negatively biased than it is in class A.
Class AB2 is where the grid is often more negatively biased than in AB1, also the size of the input signal is often larger. When the drive is able to make the grid become positive the grid current will increase.
In a class B amplifier the grid current drawn will be large, and a large drive power will be required.
Class C amplifiers are still more efficient, they can be about 75% efficient with a conduction range of about 120o but they are very non linear. They can only be used for FM or CW use only. The semiconductor or valve conducts through less than half the RF cycle. The increase in efficiency can allow a given valve to deliver more RF power than it could do so in class A or AB. For instance two 4CX250B tetrodes operating at 144 MHz can deliver 400 watts in class A, but when biased into class C they can deliver 1000 watts without fear of overheating. Even more grid current will be needed.
A side effect of improving the efficiency is that the current drawn from the high voltage supply will vary more as a function of the power input into the amplifier, this can result in unwanted effects such as the output of the HT pack being modulated by the audio modulated RF driven into the amplifier.