Originally Posted by Ricci
The reason you often see a drop off below 10hz is probably because of the stack up of electronics roll off from all the equipment in the chain. The receiver, the EQ unit, the amp, etc...take that DCX measurement. That's actually a fairly decent extension only 3DB down at about 4.5Hz. Now consider if the receiver also has the same roll off...Now you are down 6dB. Lets assume the amp also rolls off the same so add another 3dB to that and we are now down 9DB at 4.5Hz. It adds up quick and acts like a high pass filter for <10Hz. It takes some effort to get a signal chain that is not down 10dB at 5Hz. My own drops off a cliff below 6 or 7 Hz which doesn't bother me enough to try and do anything about it. Anyway I suspect that is what you see in the omnimic graphs.
Here is a good visual for that: courtesy of bosso
9db's down at 4.5hz is ok, but seeing Eric and my graphs, it still seems strange that others with almost identical signal chains and just as capable systems can measure flatter, lower. Just sayin. I tried the exact same signal chain as Not and stil had the same rolloff. The denon 4311, LG clone, and nothing else, very little rolloff in that chain, and even with the DCX, you arent down as far as our graphs show. I dont want to chase sub 7hz, and frankly don't care or are even "OK" with the rolloff falling hard at that point, but I would really like to get flat to that point before it falls off hard like I am seeing.