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RME User Forum → ADI-2 & 2/4 Pro series, ADI-2 DAC series → ADI-2 DAC FS Stereo RCA to Single RCA Subwoofer
Anyone using this type of connection?
Subwoofer manufacturer advise me NOT to do this, they told that it may harmful the sub, and suggest me to use only single channel from RME.
Any experience? Any other solutions?
You should not do this. It's not how it's designed to be used.
You should not do this. It's not how it's designed to be used.
So how should I connect it?
User's Guide, page 55:
30.5 Connector Pinouts
XLR Connectors
The XLR sockets of the analog outputs are wired according to international standards:
1 = GND (Shield), 2 = + (hot), 3 = - (cold).
The XLR outputs do not operate servo-balanced! When connecting unbalanced equipment,
make sure pin 3 of the XLR output is not connected. A connection to ground might cause
higher THD (distortion) and power consumption!
What do you want to achieve? Want is your setup?
And yes: Just don't do it.
I use a 2-into-1 "Y" cable from RME to REL sub (a very very old model REL) - is there a reason why I should not do this?
I use a 2-into-1 "Y" cable from RME to REL sub (a very very old model REL) - is there a reason why I should not do this?
This works for lower levels only (due to the 100 Ohms ADI-2 built in resistors), with higher levels you get distortions.
CORRECTION: according to my own later measurements a simple Stereo-to-Mono Y-Cable works up to full level!
See my posting below for details:
https://forum.rme-audio.de/viewtopic.ph … 05#p186505
The good: nothing will break.
You need a stereo to mono “matrix“ (too big a word for a simple thing) y-cable with built in resistors according to this schematic:
I tried to find one online, but no avail.
Maybe you have some soldering skills?
Else, Pro Audio shops have people who can do this for you.
mediummanting wrote:I use a 2-into-1 "Y" cable from RME to REL sub (a very very old model REL) - is there a reason why I should not do this?
This works for lower levels only (due to the 100 Ohms ADI-2 built in resistors), with higher levels you get distortions.
The good: nothing will break.
You need a stereo to mono “matrix“ (too big a word for a simple thing) y-cable with built in resistors according to this schematic:
I tried to find one online, but no avail.
Maybe you have some soldering skills?
Else, Pro Audio shops have people who can do this for you.
KaiS, seems this is the product available commercially.
https://www.bhphotovideo.com/c/product/ … l/overview
https://www.rdlnet.com/downloads/datasheets/tx-j2.pdf
KaiS wrote:mediummanting wrote:I use a 2-into-1 "Y" cable from RME to REL sub (a very very old model REL) - is there a reason why I should not do this?
This works for lower levels only (due to the 100 Ohms ADI-2 built in resistors), with higher levels you get distortions.
The good: nothing will break.
You need a stereo to mono “matrix“ (too big a word for a simple thing) y-cable with built in resistors according to this schematic:
I tried to find one online, but no avail.
Maybe you have some soldering skills?
Else, Pro Audio shops have people who can do this for you.KaiS, seems this is the product available commercially.
https://www.bhphotovideo.com/c/product/ … l/overview
https://www.rdlnet.com/downloads/datasheets/tx-j2.pdf
These one uses audio transformers:
“...Inputs 1 and 2 are combined and balanced through audio transformers...”
They definitely NOT suited for subwoofers, as transformers compromise the bass:
Even their specs clearly mark that, lower frequency range 30 Hz only.
Johannes AU wrote:KaiS wrote:This works for lower levels only (due to the 100 Ohms ADI-2 built in resistors), with higher levels you get distortions.
The good: nothing will break.
You need a stereo to mono “matrix“ (too big a word for a simple thing) y-cable with built in resistors according to this schematic:
I tried to find one online, but no avail.
Maybe you have some soldering skills?
Else, Pro Audio shops have people who can do this for you.KaiS, seems this is the product available commercially.
https://www.bhphotovideo.com/c/product/ … l/overview
https://www.rdlnet.com/downloads/datasheets/tx-j2.pdfThese one uses audio transformers:
“...Inputs 1 and 2 are combined and balanced through audio transformers...”They definitely NOT suited for subwoofers, as transformers compromise the bass:
Even their specs clearly mark that, lower frequency range 30 Hz only.
KaiS, I see, then that one could be has an isolated transformer inside which limits the LF.
Then the option is by soldering in line resistor to the wire, or use small terminal strip with resistors and hard wiring same as your schematic (which is much cheaper as what we did in the old days for cassette deck stereo inputs accepting mono source).
It doesn't look nice but works.
Another option is build a block (which I built many years ago, resistors inside the box and sealed, offer Stereo to Mono and Stereo pass through.
One could do it like you proposed, with a terminal strip and cut cables, if no soldering skills are at hand.
The easiest way is:
• Use a cable with RCA connectors with screw-on housing,
• unsolder the center wires from the RCA’s center pins,
• solder the inline resistors to the center wires,
• isolate with e.g. shrink tube or anything,
• then solder the resistors to the RCA’s center pin connections,
• put a label on the cable to later identify it from others.
Old electronic devices can source the resistors, if non are at hand.
Watch out for the color ring code to identify the value.
Anything in the range of 1-10 KOhm works for a sub.
You need 2 identical resitors.
A useful online tool for resistor color ring code.
https://www.digikey.com/en/resources/co … color-code
How about if I use only RME RCA Left channel to REL?
How about if I use only RME RCA Left channel to REL?
Then you miss the bass signals from the other channel.
Let‘s put it this way, and to bring the topic further:
As it’s not possible to easily source a cable with built-in resistors, I did a measurement.
ADI-2 has 100 Ohm resistors built into the output, to my surprise these seem to do the job already:
For output levels up to +15 dBu the simple RCA Stereo-to-Mono Y-Cable works without distortions!
This is just about the highest level ADI-2 DAC is capable of ( +13 dBu + 2.5 dB headroom), see manual pages 38, 31, 54.
So go for it, use an RCA Stereo-to-Mono Y-Cable, nothing will break or distort.
Use the XLR Outs then to connect your main speaker’s amp.
REMARK:
The ADI-2 Pro is capable of +21.5 dBu at it’s unbalanced output (manual page 51).
When using a simple Y-Cable to combine left+right signal into mono, one shouldn’t use above -9 dBr Volume to avoid distortions.
For signals that are in phase (aka mono) the Pro's full output level is reached without added distortion (the sum even has 2.5 dB less noise). Arguing that music usually does have mono bass as highest level the simple parallel solution might be possible even at full level...
Edit: I usually only use XLR in parallel mode, which has a higher output impedance. With the Pro's TRS rear jacks in parallel unbalanced connection, monaural signals stay undistorted up to +21.5 dBu. Single channel signals stay intact up to +19 dBu. The worst case is identical signals but 180° out-of-phase, so both outputs work against each other. The max level before internal clipping is about +14 dBu. So with the DAC, where the TRS output level is limited to +13 dBu, it is indeed possible and no problem to just sum the two outputs directly.
Now I've just gone back to connecting my sub to only one RCA out.
It sounds better somehow without the Y splitter, and I don't think there's much sub-bass on one channel that there isn't on the other, as usually bass is pretty central in the soundstage (kick drum in the middle of the band, bass notes in electronic music).
...I don't think there's much sub-bass on one channel that there isn't on the other, as usually bass is pretty central in the soundstage (kick drum in the middle of the band, bass notes in electronic music).
Certain instruments are usually centered in the mix, like bass and bassdrum.
Others are not, like low toms, double bass (usually one-sided) - electronic bass instruments, acoustic piano, room ambience (mostly stereo), etc.
So there’s no generalization.
A Sub feed from the mono sum is more universal, specially now that we have the connection problem out of the way.
"Localization" is the Term fellas... This term refers to the listener's ability to detect where the Subwoofer is. We want none of that.
LF Percussive Instruments do not emanate Pure Tones. Rather, they have Transient Content of much higher frequency that is quite easily located by the Ear. (I'm trying to recall the Allison Krauss Album that contains some of the JUICIEST TOMS!) The "Stereo Bass" issue gives me pause. Ex: The Wavelengths involved with an E1 on a Bass Guitar (28 feet) are simply too great for our Our ears to localize. Mains on the other hand DO convey the Snap, and Pluck that DO help us know WHERE the Upright Bass is...hopefully not our Subs.
That said...
TWO (2) Subs is my solution to Mono-Sub Summation networks, Boxes of Resistors, etc. Unless we ALWAYS sit with our Ears in one place, one Sub is a no-go for me. Any Sub worth consideration already has such "summing" built-in to allow Single Sub Users to function...at least until they can buy the Second Sub. 
Why are Two Subs better?
Thanks to Overlapping in-room Modal Behaviors, Two (2) Subs broadens the "best" listening area substantially, yielding a better, overall "even-ness" of the Bass Response in the Room. Go ahead! Argue, and Nit-Pick all you want, but I do believe the Data is on MY Side regarding this!
@VFTS...Give it some consideration! Unless you're listening in a Broom Closet, 2 Subs widens the listening area, increases Headroom, etc.
*Unlimited Thanks to my Dear Friend Ed Mullen at SVS who has over many years, shared with me his Boundless knowledge of Audio.
Do it!
Curt
"Localization" is the Term fellas... This term refers to the listener's ability to detect where the Subwoofer is. We want none of that.
LF Percussive Instruments do not emanate Pure Tones. Rather, they have Transient Content of much higher frequency that is quite easily located by the Ear. (I'm trying to recall the Allison Krauss Album that contains some of the JUICIEST TOMS!) The "Stereo Bass" issue gives me pause. Ex: The Wavelengths involved with an E1 on a Bass Guitar (28 feet) are simply too great for our Our ears to localize. Mains on the other hand DO convey the Snap, and Pluck that DO help us know WHERE the Upright Bass is...hopefully not our Subs.
That said...
TWO (2) Subs is my solution to Mono-Sub Summation networks, Boxes of Resistors, etc. Unless we ALWAYS sit with our Ears in one place, one Sub is a no-go for me. Any Sub worth consideration already has such "summing" built-in to allow Single Sub Users to function...at least until they can buy the Second Sub.
Why are Two Subs better?
Thanks to Overlapping in-room Modal Behaviors, Two (2) Subs broadens the "best" listening area substantially, yielding a better, overall "even-ness" of the Bass Response in the Room. Go ahead! Argue, and Nit-Pick all you want, but I do believe the Data is on MY Side regarding this!
@VFTS...Give it some consideration! Unless you're listening in a Broom Closet, 2 Subs widens the listening area, increases Headroom, etc.
*Unlimited Thanks to my Dear Friend Ed Mullen at SVS who has over many years, shared with me his Boundless knowledge of Audio.
Do it!
Curt
Curt, I am using a single Sub with mono RCA input at the moment, I do consider to add one more Sub (same model), so each Sub serves each channel and place below the main speaker makes it like a tower with 3 drivers, no idea how it will sounds like. 
But then the pre-amp of the existing TEAC single Sub out became useless, all goes to RME Dac as a pre-amp,
TEAC only works as a power amp.
Very interessting! I have the sub setup to UCXII. I summed the channels into a mono channel in TMfx. Main and sub channel faders are linked with a -6db offset for subwoofer channel. Sub handles x-over.
In a "voltage dividing perspective" Geez 
,wouldnt the -6 db offset do the same as resistors. Is there a problem with this setup? I get great sound except theres a lot of ground noise.
Very interessting! I have the sub setup to UCXII. I summed the channels into a mono channel in TMfx. Main and sub channel faders are linked with a -6db offset for subwoofer channel. Sub handles x-over.
In a "voltage dividing perspective" Geez
Yes and no, the resistors in ADI-2’s output (or a special made cable) serve for summing left+right in an analog, passive Y-cable configuration.
-6 dB is a side effect of one side loading the other.
Is there a problem with this setup?
Perfectly fine.
I get great sound except theres a lot of ground noise.
If you have a possibility to reduce main amp’s and sub’s level, compensated by sending more from UCX II, the ground loop noise would be reduced too.
Passive Attenuators come into mind if there are no built in volume controls.
The hum can be largely reduced by laying ALL interconnect cables, INCLUDING the mains power cables, very close to each other into one cable loom, like a tree with branches.
Power would be distributed from one central point only, to achieve that.
The goal is, to minimize the area that is covered by the ground loop built from audio and mains interconnects.
This size of this area is responsible for the amount of ground loop effect.
BTW: The effect of stray interference between adjacent mains and audio cables is much lower, usually negligible for line level on well-screened audio cables.
Thnx KaiS! Im gonna try to adjust the levels like you said. The sub gives a better experience overall, but in the long run its hard to neglect something that sounds like an old refrigerator.
Happy_amateur wrote:Very interessting! I have the sub setup to UCXII. I summed the channels into a mono channel in TMfx. Main and sub channel faders are linked with a -6db offset for subwoofer channel. Sub handles x-over.
Happy_amateur wrote:In a "voltage dividing perspective" Geez
Yes and no, the resistors in ADI-2’s output (or a special made cable) serve for summing left+right in an analog, passive Y-cable configuration.
-6 dB is a side effect of one side loading the other.Happy_amateur wrote:Is there a problem with this setup?
Perfectly fine.
Happy_amateur wrote:I get great sound except theres a lot of ground noise.
If you have a possibility to reduce main amp’s and sub’s level, compensated by sending more from UCX II, the ground loop noise would be reduced too.
Passive Attenuators come into mind if there are no built in volume controls.
The hum can be largely reduced by laying ALL interconnect cables, INCLUDING the mains power cables, very close to each other into one cable loom, like a tree with branches.
Power would be distributed from one central point only, to achieve that.The goal is, to minimize the area that is covered by the ground loop built from audio and mains interconnects.
This size of this area is responsible for the amount of ground loop effect.BTW: The effect of stray interference between adjacent mains and audio cables is much lower, usually negligible for line level on well-screened audio cables.
KaiS, do you mean the Y cable summing with resister will lower the output by -6dB?
KaiS wrote:Happy_amateur wrote:Very interessting! I have the sub setup to UCXII. I summed the channels into a mono channel in TMfx. Main and sub channel faders are linked with a -6db offset for subwoofer channel. Sub handles x-over.
Happy_amateur wrote:In a "voltage dividing perspective" Geez
Yes and no, the resistors in ADI-2’s output (or a special made cable) serve for summing left+right in an analog, passive Y-cable configuration.
-6 dB is a side effect of one side loading the other.Happy_amateur wrote:Is there a problem with this setup?
Perfectly fine.
Happy_amateur wrote:I get great sound except theres a lot of ground noise.
If you have a possibility to reduce main amp’s and sub’s level, compensated by sending more from UCX II, the ground loop noise would be reduced too.
Passive Attenuators come into mind if there are no built in volume controls.
The hum can be largely reduced by laying ALL interconnect cables, INCLUDING the mains power cables, very close to each other into one cable loom, like a tree with branches.
Power would be distributed from one central point only, to achieve that.The goal is, to minimize the area that is covered by the ground loop built from audio and mains interconnects.
This size of this area is responsible for the amount of ground loop effect.BTW: The effect of stray interference between adjacent mains and audio cables is much lower, usually negligible for line level on well-screened audio cables.
KaiS, do you mean the Y cable summing with resister will lower the output by -6dB/
Same as without external resistors, using ADI-2‘s built in resistors only.
Only for single-sided left OR right signal the level is - 6 dB.
It’s exactly same way as if this signal is reproduced on the left OR right main speaker only.
A centered signal will be 100 % / 0 dB, as left+right is added.
So all normal and correct using a simple Y-cable for a mono sub.
RME User Forum → ADI-2 & 2/4 Pro series, ADI-2 DAC series → ADI-2 DAC FS Stereo RCA to Single RCA Subwoofer
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