View Full Version : How best to connect my sub to amp?
ciderman9000000
21-06-2018, 17:38
Hi,
I'm in the process of upgrading my hifi. I have a NAD C326BEE stereo amp with Mordaunt Short 902i bookshelf speakers. It sounds good, but wanting some extra bass I took a look in Cash Converters today and found myself a Cambridge Audio SX120 active sub woofer for £49.99.
I haven't any cables for it yet, and am a little confused as to how best to set it up. The amp has single Sub1 and Sub2 outputs and the sub just two RCA inputs. The sub's manual suggests two different connection options (see pics below), but does it make any difference which I use? Since the amp has dedicated sub output ports, am I better using the 1x phono cable as per the diagram suggestion for AV equipment, or is it necessary that I use the amp's pre-out ports and a 2x phono cable as suggested for use on 2-channel systems?
Any help much appreciated, thanks.
https://uploads.tapatalk-cdn.com/20180621/97844def510e89db420544225955b6b8.jpg
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I think the white one on the sub is mono connector. the amp may run 2 active subs i think. thats how i see it.
use both sub out sockets on the amp, connect one to white socket on the sub, one to red. Then spend several days getting the position of the sub and the levels just right.
You'd really be better off buying bigger speakers, but it should be possible to get it to work well, it just takes a lot of trial and error.
by looks of the amp out they are mono outputs as they are not colour coded.
Doesn't matter, it will still work fine.
walpurgis
21-06-2018, 18:27
That's what I thought. I dare say both can be connected to the sub L/R inputs, which are summed to mono anyway.
Stryder5
21-06-2018, 19:04
As the sub output of the amp is summed L&R there is no benefit of using 2 sub RCA's, extra cost for no benefit.
You have pre-outs in the amp, but if you use these you loose the power side of the amplifier, to the main speakers, so you would only feed the sub.
Doesn't matter, it will still work fine.
it might cause phase issues if you connect both
ciderman9000000
21-06-2018, 19:43
As the sub output of the amp is summed L&R there is no benefit of using 2 sub RCA's, extra cost for no benefit.
You have pre-outs in the amp, but if you use these you loose the power side of the amplifier, to the main speakers, so you would only feed the sub.
So you're saying that the correct solution is a single phono lead from Sub1 to the white input on the sub, yes? As per the manual's AV connection suggestion.
My understanding of pre-out is limited at best, but my intuition was that connecting anything there might compromise power to the main speakers. But if so then why does the connection diagram in the sub's manual suggest such a setup?
Stryder5
21-06-2018, 19:54
So you're saying that the correct solution is a single phono lead from Sub1 to the white input on the sub, yes? As per the manual's AV connection suggestion.
My understanding of pre-out is limited at best, but my intuition was that connecting anything there might compromise power to the main speakers. But if so then why does the connection diagram in the sub's manual suggest such a setup?
Point 1. Sub 1 or 2 will work, so the answers yes.
Point 2. Some amplifiers have pre outs to feed a seperate power amp. The internal power amp is still connected. That is what's suggested in the second diagram. On the NAD there is a jumper that feeds the pre amp to the internal power amp but by using this you disconnect the power amp therefore the main speakers.
Hope that makes sense.
Gary
Point 1. Sub 1 or 2 will work, so the answers yes.
Point 2. Some amplifiers have pre outs to feed a seperate power amp. The internal power amp is still connected. That is what's suggested in the second diagram. On the NAD there is a jumper that feeds the pre amp to the internal power amp but by using this you disconnect the power amp therefore the main speakers.
Hope that makes sense.
Gary
Yup. That's my take too
I agree with Gary, you can use just one lead to either the left or right on the sub. I've done that in the past and that works fine. Leads tend to come in pairs though.
You can't use the pre out.
Remember......you should not be able to hear the sub....at all.
To little output is MUCH better than too much.
If its up too high, it will impress at first, but trust me, after a while you will notice the bass dragging the impact and speed of replay back.
Get a friend to sit in your hotseat and listen while you twiddle (ooh err missus etc), your back will thank you.
Stryder5
21-06-2018, 20:48
I agree with Gary, you can use just one lead to either the left or right on the sub. I've done that in the past and that works fine. Leads tend to come in pairs though.
You can't use the pre out.
Sub leads come as singles ( no difference in construction to normal RCA's though) and are generally longer than normal RCA's to let you place the sub where you want. To a degree you can place the sub anywhere to suit your setup.
ciderman9000000
21-06-2018, 21:41
Remember......you should not be able to hear the sub....at all.
To little output is MUCH better than too much.
If its up too high, it will impress at first, but trust me, after a while you will notice the bass dragging the impact and speed of replay back.
Get a friend to sit in your hotseat and listen while you twiddle (ooh err missus etc), your back will thank you.
Yeah I don't need/want the sub up high. It'll hopefully just be a little extra meat to compliment the brightness of the 902i's. Thanks for the advice.
ciderman9000000
21-06-2018, 21:46
Point 1. Sub 1 or 2 will work, so the answers yes.
Point 2. Some amplifiers have pre outs to feed a seperate power amp. The internal power amp is still connected. That is what's suggested in the second diagram. On the NAD there is a jumper that feeds the pre amp to the internal power amp but by using this you disconnect the power amp therefore the main speakers.
Hope that makes sense.
Gary
Yeah it makes sense, cheers. I knew that the NAD came with external jumpers connecting the pre-out to the main-in, whereby removing them cuts sound output to the speakers. That's why I was confused by the connection guide in the sub's manual — I didn't think it would work that way.
maxrob200
22-06-2018, 01:05
Is ther a filter on your amplifier's sub-out. If not, your main speakers will be running full range, so you will need to adjust the crossover point on your sub and match level so that the bass is not overwhelming the sound from your speakers
ciderman9000000
22-06-2018, 05:27
Is ther a filter on your amplifier's sub-out. If not, your main speakers will be running full range, so you will need to adjust the crossover point on your sub and match level so that the bass is not overwhelming the sound from your speakersThe speakers are rated to 55hz and the sub 34hz with crossover controls from 50hz to 150hz, so I set the controls to 55hz, right? This instructs the sub to only play bass sound that my speakers are unable to reproduce?
Stryder5
22-06-2018, 07:03
The speakers are rated to 55hz and the sub 34hz with crossover controls from 50hz to 150hz, so I set the controls to 55hz, right? This instructs the sub to only play bass sound that my speakers are unable to reproduce?
It's a starting point, you have to use your ears. Try setting the sub to 55hz and turn the sub volume till its intrusive, then back off the volume slowly till the sub disappears. The speakers may not output to 55hz tho so you may have to play with that setting.
As has been said before its time consuming but worth getting it right
Gary
walpurgis
22-06-2018, 08:30
It's a starting point, you have to use your ears. Try setting the sub to 55hz and turn the sub volume till its intrusive, then back off the volume slowly till the sub disappears. The speakers may not output to 55hz tho so you may have to play with that setting.
As has been said before its time consuming but worth getting it right
Gary
That's right. Basically, disregard the figures and listen to what the speakers and sub are doing. It will become evident what settings work best.
Andy, I have pondered thus question too and although your sub woofer is not a REL have a look on their website as they have some very clear instructions on how to connect a sub to an amp and set it up.
Stryder5
22-06-2018, 10:24
Andy, I have pondered thus question too and although your sub woofer is not a REL have a look on their website as they have some very clear instructions on how to connect a sub to an amp and set it up.
I havn't looked at the REL site, but it may refer to high level inputs (basically using the speaker terminals) you don't have this option on your sub as far as I can see, so don't let it throw you.
ciderman9000000
22-06-2018, 15:24
I've installed the sub now, thanks. I just got a stereo 2x phono to 2x phono cable from the local sound and lighting store and have connected it mono with a single terminal either end. I've spent about an hour fiddling with the dials but I've got it sounding pretty good to my ear now.
maxrob200
26-06-2018, 00:42
In agreement with other comments, adjusting crossover point of the sub and levels with main speakers is a time consuming process. It is also dependent on the sub placement and room interactions with bass nodes. I find that a good sub setup fills in the lower registers and does not intrude/congest the mid-range. Personal preferences of course...
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