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Sub high or low level input

Discussion in 'audio' started by Mat C, Mar 14, 2022.

  1. Mat C

    Mat C pfm Member

    Hi, in my previous post I mentioned I am about to upgrade from stand mounted speakers to floor standing speakers, and there are many advice to add a sub instead.

    I now use Luxman CL-38u and MQ-88u. The preamp has 2 output, one connected to the power amp.

    I had not played subwoofer for a decade since changed from 5.1 to stereo, and realize nowadays sub has high level input. I wonder for music would high level input be better than low level input? What is the advantage or difference?

    Thank you.
  2. H20GNA

    H20GNA pfm Member

    I’ve found that high level sounds better, allowing your active (presumably) subwoofer to decide level and crossover rather than a subwoofer output from amplifier deciding.

  3. Mat C

    Mat C pfm Member

    Thanks, Gary!
  4. ampedup

    ampedup Lost in audio

    As far as I know, the Luxman CL-38u preamp doesn't have a subwoofer output. What about using his second set of pre-outs into a sub, compared with using the speaker terminal outputs ? I think that's what the OP is asking.
  5. Greyandy

    Greyandy pfm Member

    The difference between the line level and speaker level inputs was night and day for me. The sub immediately fell into place with the system with speaker level. You probably don't need anything special in terms of cable either.
  6. Amber Audio

    Amber Audio This is the Day

    Pre outs work fine into a sub with built in amp.

    The general view seems to be High Level for music systems and Pre/LFE out for AV/movie systems. I have tended to use High Level with my Stand-mounts + RELs and Pre/LFE out for my AV surround speaker packages. REL have guides on how to connect High Level - different types of amps need different connections e.g. Class D
  7. Mat C

    Mat C pfm Member

    Thanks guys, I may look for a REL sub in pre-owned market.
  8. Beobloke

    Beobloke pfm Member

    Most subwoofer high level inputs merely put the input through an attenuator then pass the signal to exactly the same circuit as the low level input.

    Consequently, the differences between the two should be relatively minimal especially if the low level inputs are fed by a normal, unfiltered, preamp output.
    RJohan likes this.
  9. Greyandy

    Greyandy pfm Member

    I've read (somewhere...) that taking the speaker level connection is 'truer' to the sound of the amp than taking a line output from the pre. This does make some sense and was certainly my experience but YMMV etc.
  10. Waxxy

    Waxxy pfm Member

    My biggest concern with high-level inputs is the fact that the signal gets "amplified" twice. Any distortion coming from the power amp would be amplified further by the amp in the sub.
  11. rag987

    rag987 pfm Member

  12. Del monaco

    Del monaco Del Monaco

    To be honest, I tried both with my REL. I have stick with the high level though the difference was certainly not night and day. I may try it again as the Yamaha set up is useful.
  13. Greyandy

    Greyandy pfm Member

    I suspect that the merits of line v's speaker level inputs are very much system dependant so the only answer is to try it for yourself. As I said, in my case it gave a significant improvement in integration and a friend who has the same sub (but different source components) also reported the same favourable results.
  14. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Low level is ALWAYS best but should be "pre out" not a sub out if it's already EQ'ed.
    Del monaco likes this.
  15. Amber Audio

    Amber Audio This is the Day

    What is a high level connection and why does REL insist you use it?

  16. ToTo Man

    ToTo Man the band not the dog

    It's advisable to check if your amplifier employs a 'floating balanced' topology before connecting it to the high level input on the sub, if it does then you may end up releasing some magic smoke.


    Skip forward to 4min 12secs:
  17. Amber Audio

    Amber Audio This is the Day

    Well yeah as ever RTFM.
  18. IWC Doppel

    IWC Doppel pfm Member

    I still don't get this rationale, I don't buy the fact that you are listening to a speaker signal driving the input then stepped down is better than taking it from normal line level is anything to do with 'sound signature' the sub has different drivers a separate and different power amplifier and usually a different location anyway.... It might sound better or not connected this way but it isn't anything to do with matching the sound of your 'system'

    Logic would say, take the same pre output at the same time and feed it into similar power amplifiers wouldn't it .....? not going through two rather than one power amps having the signal designed to drive a speaker reduced to drive a power amp
    RJohan likes this.
  19. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Total bollox! Always use the low level inputs.
    RJohan likes this.
  20. Amber Audio

    Amber Audio This is the Day

    You forgot to add “in your opinion”. I’ll carry on connecting my Subs how their manufacturer recommends rather than how some random bloke on a forum tells me.

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