Owners
Darkmatter - Single KK DXD808
Recruit - Single KK DXD808
Audiofan1 - Single KK DXD12012
Kenny Powers - Single KK DXD12012
Asere - Single KK DXD12012
13T - Quattro KK DXD12012
Compilation of Kens Responses
About Sub Placement and the Benefits of DUO Configurations
The Difference between the XLR/RCA inputs
A question about the XLR Pass through if using an unbalanced XLR connection from the AVR
Darkmatter - Single KK DXD808
Recruit - Single KK DXD808
Audiofan1 - Single KK DXD12012
Kenny Powers - Single KK DXD12012
Asere - Single KK DXD12012
13T - Quattro KK DXD12012
Compilation of Kens Responses
About Sub Placement and the Benefits of DUO Configurations
Thanks for the kind words, they are always appreciated.
Further to our discussion, I just posted the following on another Home Theater Shack thread that perhaps is better suited posted here:
The side of the DXD cabinet with the side driver is designed to be optimally placed 2-4" from the wall, preferably in a good solid corner of the room. For most rooms, I usually recommend first locating the DXD in the closest solid corner to your primary listening position. So, if the closest solid corner (no nearby openings like an open door) is in the back of the room, try it there first.
Every room is different and needs some experimentation with subwoofer placement. But, after measuring literally hundreds of studios and rooms with very sophisticated TIME DOMAIN measurement equipment with the world's best laboratory measurement microphones, and my own proprietary analysis technique (which measures and computes very much like our ear/brain mechanism interprets the spectrum of sound energy heard over time including and especially transients), the closest solid corner has the best chance of giving you the best and most accurate "out-of-the-box" results, in my humble opinion and experience.
The DXD's are specifically designed for corner placement which normally will give you the least room mode problems, especially if you are using the stacked DUO configuration which is technically a whole new subwoofer for a host of technical reasons.
Here is what I just wrote in another Home Theater Shack thread about this:
"Yes, a DUO will be AUDIOPHILE BASS NIRVANA for you, I guarantee it! As good as single DXD-808's and DXD-12012's are, it is a whole new experience in the DUO configuration because they are technically a whole new type of subwoofer from the single cabinets, I designed it that way.
Once you stack at least one pair, you have my full BALANCED 3D HIGH VELOCITY PUSH-PULL-PULSAR DEEP BASS PRESSURE WAVEFRONT LINE ARRAY NEARFIELD technology operating in all its glory!!!"
The DXD's can be placed anywhere in a room, but optimum performance in most rooms will be achieved in a corner placement, again, I designed it that way for all the good reasons.
Also worth noting, the DXD's performance secret (please don't tell my competition this secret) is they are very specifically and deliberately and scientifically designed to give optimum bass performance in a real room or studio with real walls, not in a parking lot outdoors where a lot of review measurements are made for subwoofer comparisons. The same holds true for close-up type measurements where only part of a DXD's output is actually measured.
The DXD's put out a sound pressure wave in multiple directions and cannot be properly measured outdoors or close-up, this is a big mistake some reviewers are making. It is somewhat analogous to trying to measure the horsepower on the ground of an ALL WHEEL DRIVE vehicle with a dynamometer, but only measuring the horsepower at one wheel.
I actually get a big kick at the outdoor and close-up review measurements which show the DXD's appearing to have unusual output levels and response, and then when a reviewer listens and measures in a room they usually comment they cannot believe how much pants flappy energy and impact is heard and felt in their real listening room with real walls and how low the DXD's measure in the room. Remember (another top secret not to tell my competitors), I don't use high pass protection filters in my subs (they ruin the bass impact) so they will go all the way down in a real room with real walls.
My mentor, Dr. Lester M. Field, used to say "the device is the perfect analog of itself!"
GOOD SOUND AND GOOD BASS TO YOU...ALWAYS...KEN
The Difference between the XLR/RCA inputs
I have seen several thread discussions and several thread speculations about the level sensitivity difference between a DXD sub's RCA input versus the XLR input when using an unbalanced RCA to XLR signal adapter to the XLR input (instead of using a normal professional balanced XLR input signal) and why sometimes the XLR input either sounds better or has less hum in some situations.
The DXD's RCA and XLR inputs are calibrated to a particular professional standard (can I say THX?). The RCA's input REFERENCE LEVEL to achieve a certain dB SPL (known as the REFERENCE LEVEL) is 100mv (.1 volt). The RCA has a ground connection and a hot connection, and the .1 volts is measured between the hot and ground connection.
To achieve the same dB SPL output level from the XLR input, the XLR needs to see 200mv (.2 volts) on its input (twice the voltage). The XLR has a ground, a hot terminal (pin 2) and a negative terminal (pin 3). So, pin 2 sees +.1 volts and pin 3 sees a -.1 volts. The +.1 volt plus the -.1 volt gives a voltage potential of .2 volts at the balanced input of the XLR, which is 6dB (twice the voltage gives +6dB) more signal level than the .1 volts seen on the RCA input. This means that technically the XLR input needs 6dB more input signal drive level (twice the voltage) to get the same dB SPL output from the sub.
So, if you use the XLR inputs unbalanced with an RCA to XLR adapter, you are only feeding a signal to pin-2 of .1 volts as there is no voltage on pin-3, so the XLR input with .1 volts on pin-2 will have -6dB SPL output level below the same .1 volts on the unbalanced RCA input.
So again, technically, on the DXD, if you use the same unbalanced signal from your surround processor to feed either the DXD's RCA input (only one RCA input) or the XLR input using an unbalanced RCA to XLR adapter, you will have a signal level sensitivity of -6dB SPL lower on the XLR inputs, again when using an unbalanced signal into the balanced XLR input.
If you happen to be using a Y-connector to feed both RCA input's, and then try the single XLR input with an RCA to XLR adapter, you will see a +12dB SPL difference between the two RCA inputs versus a single XLR input. This is because feeding both RCA inputs (.1mv LEFT input + .1mv RIGHT input) with a Y connector feeds twice the voltage (+6dB) to the DXD compared to feeding a single RCA input.
As to the reduced hum using the DXD's XLR input there can be two reasons. One, using an RCA to XLR unbalanced adapter to feed the DXD, the DXD will require 6dB more signal drive level to get the same output, so if you increase the subwoofer output drive signal of your processor by 6dB, you will reduce any hum by 6dB compared to the RCA input. Secondly, as mentioned on the description page for the DXD's it states "The balanced XLR input uses a High Performance Professional Instrumentation type balanced circuit design, which can even help eliminate hum in some unbalanced situations were a ground loop exists..."
Hope this answers the question...KEN
A question about the XLR Pass through if using an unbalanced XLR connection from the AVR
A question on max output of 808 and 12012 subsThe XLR PASS-THRU will not change anything.
As it is marked on the back panel of the DXD, the XLR OUT is a passive "DIRECT PASS-THRU (UNBUFFERED)" so whatever type signal (balanced or unbalanced) is at the XLR IN appears identically on the XLR OUT. It is the same as if you were using an XLR Y-adapter, which is a totally passive PASS-THRU.
As to the TRIM issue, I would need more specifics about your AVR and what levels you are actually measuring. You could also buy my upcoming STUDIO BASS OPTIMIZATION & CALIBRATION BOX and not worry about it...KEN
First let me say that you don't have to worry about damaging a DXD-808 or DXD-12012, they can take just about anything you can throw at them. They are built for continuous, year in and year out, heavy duty studio use where you cannot imagine what is both deliberately and unintentionally sent to the subwoofer during major blockbuster film sound design sessions, I assure you it is far beyond your wildest sonic imagination. Also realize that the DXD's can take all of this even though they do not have the usual high-pass protection filter (which ruins the transients and impact) used by most subwoofer manufacturers (out of fear of damage to their amp and/or driver with high level subsonic signals).
The only caveat is if you have line voltage in excess of 240 volts and do heavy duty subsonic testing with test tones or accidently or deliberately do a high level auto calibration sweep (usually below 10Hz), there is a remote possibility you might fatigue the AC power fuse which is there to protect the amp from abuse or from large power surges from lightning storms or extreme power line surges, and the fatigued fuse might blow when the DXD is turned on due to an excess power surge on turn-on, again usually only if your line voltage is in excess of 240 volts (I have only seen this issue with a handful of owners in the UK and Singapore where they have all measured their line voltage in excess of 240 volts). A new line fuse takes care of it.