SUBWOOFER CONNECTION

[GETTING OLD]

Hi

Apologies for yet another - "Subwoofer connection" question, but after scouring the internet, this, and other forums, I have yet to find an answer that confirms one way or the other.

I have an old REL sub that I used to connect using REL's preferred connection method - via the high level neutrik cable from my old integrated amplifier - red wire to right "+", yellow wire to left "+", and the black wire to either left or right "-", and the neutrik end into the subwoofer's HIGH input ...simple, and without problems, but that was back in the day and things have moved on , equipment changes, etc, I changed my integrated and now use a pre-amp plus two bridged amplifiers as monoblocks (one for left and one for right - fully balanced), but re-connecting the sub has proven somewhat difficult, and very frustrating with the new equipment.

In short, after numerous calls/e-mails to REL and the amplifier's manufacturers it has been established that the amps (temprimental) should not be connected via the HIGH level method and that the LOW level method should be used, so my question(s) are -

1. Given that I have XLR balanced outputs on my amplifiers*, is it a simple case of running two cables (XLR to RCA) from each of the amplifiers XLR outputs (Left channel and Right channel) into the subwoofers left and right RCA inputs?

2. Assuming that the above is the way to connect, the fact that I require 10 metre lengths, so would this create problems - noise, hum, etc.

3. Is there another way to connect them?

* I cannot use my preamplier's output as it only has two outputs - 1 XLR and 1 RCA but unfortunately they cannot be used simultaneously.

Many thanks

 

[andyjm]

Hi

Apologies for yet another - "Subwoofer connection" question, but after scouring the internet, this, and other forums, I have yet to find an answer that confirms one way or the other.

I have an old REL sub that I used to connect using REL's preferred connection method - via the high level neutrik cable from my old integrated amplifier - red wire to right "+", yellow wire to left "+", and the black wire to either left or right "-", and the neutrik end into the subwoofer's HIGH input ...simple, and without problems, but that was back in the day and things have moved on , equipment changes, etc, I changed my integrated and now use a pre-amp plus two bridged amplifiers as monoblocks (one for left and one for right - fully balanced), but re-connecting the sub has proven somewhat difficult, and very frustrating with the new equipment.

In short, after numerous calls/e-mails to REL and the amplifier's manufacturers it has been established that the amps (temprimental) should not be connected via the HIGH level method and that the LOW level method should be used, so my question(s) are -

1. Given that I have XLR balanced outputs on my amplifiers*, is it a simple case of running two cables (XLR to RCA) from each of the amplifiers XLR outputs (Left channel and Right channel) into the subwoofers left and right RCA inputs?

2. Assuming that the above is the way to connect, the fact that I require 10 metre lengths, so would this create problems - noise, hum, etc.

3. Is there another way to connect them?

* I cannot use my preamplier's output as it only has two outputs - 1 XLR and 1 RCA but unfortunately they cannot be used simultaneously.

Many thanks

Assuming your XLR amp outputs are line level, you can connect those to the RCA inputs on your REL. A few issues though:

1. 10M is a long length for a sub cable, 50Hz mains is slap bang in the middle of a sub's response and any mains hum will be a pain.

2. Generally grounding works best when it radiates out through equipment from single point in a star arrangement, if you connect the signal ground of the two amps together at the REL, you will have created a loop and you may have hum issues on your main speakers.

3. You will need to convert from a balanced signal to unbalanced to connect to the REL.

I would recommend running balanced xlr (pro mic cables are cheap and good quality) from the amp all the way to the sub and then unbalance the signal using a balun transformer just prior to connecting to the REL via RCA. Jensen transformers have a good range of balanced to unbalanced transformers. This will also solve your grounding issue as the REL can float relative to your amplifiers, and running the signal balanced for the 10M run will avoid any mains hum. If you search around, you can find baluns built into the connectors themselves, but be careful about frequency response - good LF response usually means more expensive transformers.

You could investigate whether you could get a way with only connecting to left or right instead of both. In the days of LPs, LF was mixed to both tracks to give the stylus a chance of staying in the groove - the LF was not stereo. I believe that this approach was continued for CDs, but I couldn't say whether that is true for every CD or not.

 

[GETTING OLD]

Andyjm

Thankyou for taking the time out to reply - very helpful.

Yes I thought that the length - 10 metres may raise a few issues (hum, noise, etc). As far as I'm aware the amps XLR outputs are indeed "line level" so that shouldn't be a problem. Like you suggested, instead of running XLR to RCA, I had thought about running two lengths of balanced XLR to XLR (trying to avoid hum, etc) and then convert the signal, but I wasn't totally sure if this would be any different but going from your reply it would be.

As for converting/transforming the signal - would something like these work - http://www.decks.co.uk/products/Cables__Connectors/Die_Hard/RCA_male__XLR_Male_Adapter?gclid=CIDZ5Yrb1rcCFabLtAodO3gAyw#.UbRSGOfVCSp

or

http://www.hifi-tower.co.uk/Male-RCA-To-Female-XLR-Adaptor-Cable-DJ-PA_i1549.htm?etcc_med=STC_CC_ATTR_VALUE_SEA&etcc_cmp=DJ+Equipment&etcc_grp=Cables+%26+Adaptors&etcc_bky=%7Bkeyword%7D&etcc_mty=%7Bmatchtype%7D&etcc_var=pla&etcc_plc=%7Bplacement%7D&gclid=CK-E05rc1rcCFYTItAodTCwASw

or are they simply "too basic" (just adapters) and in effect be the same as a XLR to RCA cable? Would I need something more complex,(an actual transformer) like this - http://artproaudio.com/artcessories/audio_solutions/product/cleanbox_pro/ and then would I need two very, very short runs of rca cable?

Thanks in advance

 

[andyjm]

Andyjm

Thankyou for taking the time out to reply - very helpful.

Yes I thought that the length - 10 metres may raise a few issues (hum, noise, etc). As far as I'm aware the amps XLR outputs are indeed "line level" so that shouldn't be a problem. Like you suggested, instead of running XLR to RCA, I had thought about running two lengths of balanced XLR to XLR (trying to avoid hum, etc) and then convert the signal, but I wasn't totally sure if this would be any different but going from your reply it would be.

As for converting/transforming the signal - would something like these work - http://www.decks.co.uk/products/Cables__Connectors/Die_Hard/RCA_male__XLR_Male_Adapter?gclid=CIDZ5Yrb1rcCFabLtAodO3gAyw#.UbRSGOfVCSp

or

http://www.hifi-tower.co.uk/Male-RCA-To-Female-XLR-Adaptor-Cable-DJ-PA_i1549.htm?etcc_med=STC_CC_ATTR_VALUE_SEA&etcc_cmp=DJ+Equipment&etcc_grp=Cables+%26+Adaptors&etcc_bky=%7Bkeyword%7D&etcc_mty=%7Bmatchtype%7D&etcc_var=pla&etcc_plc=%7Bplacement%7D&gclid=CK-E05rc1rcCFYTItAodTCwASw

or are they simply "too basic" (just adapters) and in effect be the same as a XLR to RCA cable? Would I need something more complex,(an actual transformer) like this - http://artproaudio.com/artcessories/audio_solutions/product/cleanbox_pro/ and then would I need two very, very short runs of rca cable?

Thanks in advance

It all depends. To get the full benefit of running balanced all the way to the sub, you need to unbalance the signal in a way that preserves the noise cancelling topology. The adaptors you link to wont do this - the issue isnt the shape of the plug, it is the way the signal is transmitted. The final link to the cleanbox seems overkill (and I think the flow is the wrong way - from unbalanced to balanced?). To do the job properly you need a 'balun' (balanced / unbalanced) - simply a transformer will do the trick.

There are tricks to unbalance a balanced signal without using a balun, but this will lose any noise cancelling benefits and without knowing how your amps drive the balanced links, it is difficult to be conclusive about the way to do this.

If you have a mildly technical background, have a look at the white papers on the Jensen Transformers site, they have a pretty good 'how balanced works' and a number of diagrams on how to balance an unbalanced signal, and also unbalance a balanced signal.

Edit: Here is the link. You want diagram 3.1 - this should be available either built in to a adaptor, or as a separate box to plug into

http://www.jensen-transformers.com/an/an003.pdf

I found a boxed transformer that looks as if it will do the job. I have no experience of this firm, and it looks a bit pricey - but this is the sort of thing that should solve your problem.

http://www.markertek.co.uk/Catalog/Audio-Conversion/TX-AFC1F?gclid=COKv38Pr2LcCFdLItAodfFgASQ

 

[GETTING OLD]

Thanks again - ANDYJM

Whilst I'm not that technical minded your explanation and examples have made it clear what I need to look for.

Cheers