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The Audio Critic

Home Theater BIG Screen, 2000 watts

MP3's v.s CD's, DTS v.s Dolby and other Stuff

Macrovision and how you can avoid it

Read this article for some Sound Advice

Build your own set of biline speakers

Spherex 5.1 (Home Theater in a box) Speaker Review

Proview RX-326 32" LCD HDTV Review

LG LDA-371 DVD Player Review

A Computer for the Living Room, a look at HTPC's

Spyder3TV Review

ATSC: what is it and why should you care

Boxee Box Review

2000 watts, 3 Subwoofers and 6 Speakers

QSC Amps

I still remember the first time I saw the Qsc 1700 I asked what the hell it was supposed to be, it had no volume controls just an On/Off rocker switch in the front with LED's that indicated 'Clipping' and Power. I was introduced to the world of Industrial or 'DJ' Amps, these puppies draw a staggering 15 amps of juice at full power (one per household breaker only please) in fact the output/speaker binding posts have an electrical warning sticker right on them! You needed a pre-amp to use them, (basically a volume control/mixer) I quickly discovered they were also very sensitive as it was difficult to play them at anything other than LOUD. it weighed a staggering 57lbs and the transformer alone took up half of the case. Industrial was a good choice of word as they looked like they could survive being dropped down the stairs and the stairs would be damaged not the Amp!

I did have it serviced once because one channel was weak, the tech couldn't believe how easy it was to work on and he went on to add it will last forever, it was the most robust amp he had ever worked on! These things were meant to be abused at full volume for hours at a time everyday!

It was originally purchased from a store called 'Used Sound' they had instruments, speakers, amps and more, it was purchased for $800 in 1992 that makes it over 12 years old. it still works and kicks the crap out of anything else sold on the High-end consumer lines. the USA 370 amps were purchased new from ADD Electronics for $700 each in 1994 and these amps provided much more power than even the THX standards demanded (THX is 100 per channel). The specifications chart is below.

USA 370 USA 1700
Output Power: (typical, both channels driven)
4 ohms, 1 kHz, 1% THD
8 ohms, 1 kHz, 1% THD
8 ohms, 20Hz to 20 kHz, o.1% THD

2 ohms, 1kHz, 1% THD
(typical, single channel driven)


Power Bandwidth: 5 Hz to 60kHz 5 Hz to 70kHz
Distortion (8 ohms): THD, 20 Hz -20 kHz
at rated power <0.1%
SMPTE-IMD <0.025%
THD, 20 Hz -20 kHz
at rated power <0.1%
SMPTE-IMD <0.01%
Dynamic Headroom: 2 db at 8 ohms 2 db at 8 ohms
Sensitivity (with gains at max): 29 db voltage gain 1.12 Vrms for rated power at 8 ohms 34 db voltage gain 1.13 Vrms for rated power at 8 ohms
Power Consumption: 4.4 Aoc at 120 V 14.7 Aoc at 120 V
Damping factor: Greater than 200 at 8 ohms Greater than 200 at 8 ohms
Noise: -100 db full output A weighted. -100 db full output A weighted.
Input Impedance: 20k Ω balanced and unbalanced noninverting or 10k Ω unbalanced inverting. 20k Ω balanced and unbalanced noninverting or 10k Ω unbalanced inverting.
Dimensions: 5.25'' (13.3 cm) tall
19" (48.3 cm) wide
9.5" (24.1 cm) deep
7" (17.8 cm) tall
19" (48.3 cm) wide
10.8" (27.4 cm) deep
Weight: 28 lbs (12.7 kg) 57 lbs (25.9 kg)

While on the subject of QSC amplifiers I saw this article on James Randi's site about one of QSC's R&D guys named Paul Lerymenko it's very interesting as it shows his thoughts on building a quality product.

Paul Lerymenko once said 'people who claim supernatural powers never seem to be able to make them work in the presence of magicians' Paul Lertmenko is now the head of R&D at QSC Audio (one of the makers of the ABX Comparator- see more below). I remember talking with him, back then, about the differences between the sound quality of various audio devices, especially amplifiers. Paul maintained that any reasonable quality amplifier, operating within its specified limits, is acoustically indistinguishable from any other. Ditto for many other devices as well. He had nothing but contempt for the claims of manufacturers of high end speaker cables and other magical crap!

The ABX Comparator is the ideal setup to test audio devices and systems. It generates a random "A or B" switching signal, so that the user does not know whether the item or variable being examined is in or out of the circuit, and it accepts the user's decisions and stores them. When the Moment of Truth arrives, the user sees the results of a proper double-blind test. This is a setup that the audio quacks strenuously avoid, in fear that their fakery will be exposed.

To read what Sterophile magazine has to say about the ABX Comparator click Here

This is an Isobaric subwoofer (dual 12" drivers face to face)

This odd looking Isobaric sub-woofer is a marvel of technology and research, basically every speaker needs a certain volume of air in an enclosure to perform correctly, this calculation is based on the driver specifications, what makes Isobaric enclosures really neat is by placing another driver inside the box facing the driver outside the box (which is wired out of phase). The two drivers act like a piston, working together to create twice the sound in a box half the size required by a single driver. Yep that's right, 3db louder in a small compact package 1/2 the size of the box required for a single driver! Now you can understand why this design is winner, in addition to the benefit of a smaller size the drivers work together to cancel distortion at loud levels enabling them to play distortion free and loud at high power levels! Trust me I use one of these sub's in my car with a Hi-Fonics 35 watt amp (yeah just 35 watts) and my teeth are rattling along with the bass, in fact my wife won't sit in the car at full volume because the bass pounds so hard it gives her a headache! Even my buddy with dual 15" drivers is amazed at the amount of bass this sub makes.

Now remember we have a dual voice coil 15'' subwoofer hidden in the wall under the amps, another subwoofer (the Isobaric 12'') tucked in a corner and for good measure there is a 10'' dual voice coil subwoofer directly behind the seating area. These are all connected to one channel of the QSC 1700 for a total load of 2 Ohms enabling the amp to produce around 1,250 watts of power (good thing the foundation is reinforced).

The rest of the speakers have 185 watts per channel to use but because 90% of a movie is dialogue and it needs to be clearly heard we used 2 speakers for the center channel to ensure the voices could be heard crystal clear over the environment noises. Remember to try to set the volume so dialogue is heard at a normal speaking level or the characters will be YELLING all the time!

I should point out here that this is major overkill in the power department I doubt even 1/4 of the actual power available has ever been used, Hey will you turn off that Jet engine so I can hear myself think! Did I mention that this system is LOUD!!!

Just remember for the sane individual even a paltry 25 watts can be extremely loud if paired with efficient speakers, only the bass channel or sub-woofer channel needs a good amount of power, thankfully most subwoofers bought commercially have built in amplifiers to provide adequate amounts of power for the task.

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