KK DXD 808/12012 Owners Thread - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #21 of 365 Old 08-15-13, 09:42 AM
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Re: KK DXD 808/12012 Owners Thread

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Yes I did. I couldn't believe it when I was notified.
Lucky man indeed, well done mate
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post #22 of 365 Old 08-15-13, 09:48 AM
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Lucky man indeed, well done mate
Thanks
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post #23 of 365 Old 08-16-13, 12:30 AM
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Re: KK DXD 808/12012 Owners Thread

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Yeah i originally got the RCA-XLR connection as i much prefer XLR connections due to how snugly they fit together. It also seemed to reduce the slight hum the sub gave out when the AVR is not turned on. So i have been very pleased with it for that.

Maybe the reduced volume is because the if it was a XLR-XLR cable there would be two "hot" pins as such which would give the subs input more voltage which would generate a higher output. These are all wild guesses.

EDIT

An RCA-XLR is still unbalanced due to it only having a single hot pin.
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
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post #24 of 365 Old 08-16-13, 12:40 AM Thread Starter
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Re: KK DXD 808/12012 Owners Thread

Thank you for the reply ken, it was what it thought was going on even if I did not fully understand the technical reason as to why!

Does the DXD change the XLR out to be a fully balanced XLR so if I connect the second in a duo stack it will be louder as its getting 0.2v instead of the 0.1v of the first one?

Also what happens when you run out of trim on the AVR? How will I level match a Quattro stack then?
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post #25 of 365 Old 08-16-13, 01:43 AM
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Re: KK DXD 808/12012 Owners Thread

I think you can alter the balance yourself on this one, by using an SPL meter and just turning the speakers SPL down so that you can accommodate more SPL within your system.
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post #26 of 365 Old 08-16-13, 06:17 AM
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Re: KK DXD 808/12012 Owners Thread

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Yes, if you already own an 808 then the logical step would be to get a stack or DUO which will then give you the fully balanced sub and the benefits which Ken has discussed earlier which tbh I cannot wait to hear, as I know from experience, with his speakers and subs, when he creates something special, you really do need to hear it for your self to benefit it fully

It is also nice to have a proper discussion with people who are passionate about a subject that I also love and enjoy so much, other forums which I know to well always end up in arguments and I know those forums very well myself which is why I left them.
Hi John

I agree his speakers are bloody tremendous, his new range really need to be getting much more exposure than they currently are, hopefully that will change soon.

I don't have room for a second 12012 in my small room at the moment but we have just had planning permission to build our new home where I have a dedicated room big enough for another!

One day I shall have a duo setup!
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post #27 of 365 Old 08-16-13, 09:44 AM
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Re: KK DXD 808/12012 Owners Thread

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Hi John

I agree his speakers are bloody tremendous, his new range really need to be getting much more exposure than they currently are, hopefully that will change soon.

I don't have room for a second 12012 in my small room at the moment but we have just had planning permission to build our new home where I have a dedicated room big enough for another!

One day I shall have a duo setup!
Hi Andrew,

Yes mate, they certainly need more exposure in the UK for sure and all over for that fact, hopefully that will change soon !!

A second 12012 would be awesome mate, and that is good news about the house or maybe not Lol!

I think the DUO DXD808 will be the ultimate set up for me, for my usage anyway and will give me reference bass, well to my reference :lol:
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post #28 of 365 Old 08-16-13, 10:32 AM Thread Starter
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Re: KK DXD 808/12012 Owners Thread

I think that might be the same for me too recruit! Hopefully one will pop up second hand if not i will just have to keep saving!
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post #29 of 365 Old 08-16-13, 10:51 AM
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Re: KK DXD 808/12012 Owners Thread

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Thank you for the reply ken, it was what it thought was going on even if I did not fully understand the technical reason as to why!

Does the DXD change the XLR out to be a fully balanced XLR so if I connect the second in a duo stack it will be louder as its getting 0.2v instead of the 0.1v of the first one?

Also what happens when you run out of trim on the AVR? How will I level match a Quattro stack then?
The 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
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post #30 of 365 Old 08-16-13, 12:09 PM
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Re: KK DXD 808/12012 Owners Thread

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You could also buy my upcoming STUDIO BASS OPTIMIZATION & CALIBRATION BOX and not worry about it...KEN
I want one Ken, pop one in the post please?
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