Why Are Standards Necessary?
Besides inflated claims of amplifier power output, it’s just as easy to claim that a loudspeaker has "frequency response down to 20 Hz" when in fact the speaker’s cone may move slightly at 20 Hz, but if the speaker’s real-world output at that frequency is –15 dB from its output at 100 Hz, you won’t hear the 20-Hz tone. That’s why standards of frequency response qualified by a dB specification are essential to accurately represent real performance in a loudspeaker or a subwoofer.
Axiom at the Cutting Edge of Standards
With Tom sitting on the R3 board as a voting member, Axiom helped set global standards adopted by the IEC (International Electro-technical Commission) and other technical organizations on loudspeaker measurement, amplifier testing, and defining multi-room wiring. For example, one of the issues currently facing the board is establishing real amplifier measurement standards for the Federal Trade Commission (FTC). How many channels do you measure? Five? Seven? Do you apply the same measurement standards used for the front channels to the surround channels and measure all channels at full power output? "Probably not," says Tom, "because it’s not realistic to expect the surround channels would have to deliver the same high power output as the front left, center and front right. If not, then what weighting do you give to each channel?"
When the new standards are in place, then a manufacturer who claims he has a "3,000-watt" Home Theater in a Box or subwoofer will have to prove such outlandish claims or withdraw them. (Long-term AudioFile readers will know the example is impossible because you can’t draw that much power from a domestic wall socket).
Another standard being developed by the speaker output working group is the all-too-common "20 to 20,000 Hz" frequency response, which is essentially unqualified. The unqualified 20 to 20,000 Hz will be replaced by frequency response specifications qualified by + or - dB, and any claims about high SPL (Sound Pressure Levels) will have to be measured with a new set of standards.
New Standards for Grounding
Tom is also pushing to limit the source output impedance of components between 60 and 100 ohms. Currently some components have output impedances as high as 1 kOhm (1,000 ohms) which can trigger interconnection anomalies. And his participation on the audio board is to encourage the industry to understand that HD is not just about video; the HD experience is greatly enhanced by high-definition multi-channel audio, as any Axiom home theater system owner can attest. Next on the list - educating consumers about why 128-kbps music downloads are not only uncool - they're un-hi-fi. At Axiom, we feel that's just plain wrong . . .
No complaints – just wondering.
A. You will find that the deep bass content will vary considerably from one recording to the next. Some CDs I own have poorly recorded bass or virtually none at all, so I have to increase the subwoofer volume level to hear what little bass is present on the recording. Others have way too much bass and I have to lower my subwoofer level to get a natural balance.
You will also find that the EP350 may sometimes reproduce some sub-sonic rumbles that are on the original recording but were not audible to the recording or mastering engineer because their monitor speakers didn't have deep enough bass response to reproduce it. For example, typical annoying deep bass such as the sound of the blower on pipe-organ recordings, air-exchange rumble from poorly isolated air-conditioning systems in recording halls and studios, subway sounds on recordings done in large cities where the studio, church, or concert hall isn't well isolated, footfalls on the stage in live opera recordings, etc.
You will need to adjust the subwoofer level in any of these situations. Fortunately they're fairly rare, except for the wide differences in bass content from one disc to the next.
There is a tendency at first to run your subwoofer volume too loud, so that you can hear its effects. You shouldn't "hear" the sub's contributions as such. The sub should just fill in the lower octaves, add a powerful sense of bass instruments when present, and remain sonically unobtrusive. Try turning down the sub level somewhat. Your EP350 may also be located in a "null" where there is a lot of bass cancellation so you've turned the volume up too high to compensate; or it may be the opposite. If the sub is in a spot where there is a lot of bass emphasis--a standing wave--it may seem boomy at one or two frequencies. I think when you find the ideal spot, you shouldn't have to adjust it so often.
Keep in mind too that all turntables generate some rumble and that a subwoofer may make it all too audible depending on the quality of the turntable and the frequency of its rumble component. In the era of vinyl and stereo, many preamps were equipped with a handy switchable rumble filter that rolled off deep bass below 30 Hz or a bit below to prevent power-wasting pumping of the woofers from turntable rumble. LPs with ripple warps may also contribute to pumping of the woofer.