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Thread: Yet another subwoofer integration question

  1. #1
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    Default Yet another subwoofer integration question

    Hi Alan,
    I would like to add a sub for my SHL5. From your previous posts, I learn that you recommended using external crossover on the sub to deliberately cut-off low frequency from reaching SHL5 such that the mid unit doesn't have to work hard to handle low frequency, and hence increase overall loudness and lower distortion.

    During sourcing an appropriate subwoofer, I come across a sub have this hand-pass filter feature, cutover frequency at 90hz.

    My fear is by cascading this external filter (assume is high quality one) to SHL5 internal crossover, will it affects the internal crossover of SHL5 and potentially affects the tonal of SHL5?s midband?

    Besides, the spec cutover frequency 90hz, a bit high IMO, by cascading this to SHL5's internal crossovers, will the cutover frequency point be further shifted to somewhere higher (or lower)?

    Attached pls see the freq. response (red line) of target sub. I was told the crossover is Linkwitz-Riley type, no idea what does it mean.

    Rgds,
    Kevin
    Attached Images Attached Images

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    Default Re: Yet another subwoofer integration question

    Is the subwoofer active? Does the full-range signal from the power amp pas into the sub, then on to the SHL5? Or is the sub somehow connected between the pre and power amps?

    90Hz probably is a bit high - I'd personally have preferred a lower frequency of (say) 50Hz.

    Linkwitz-Riley (LR) describes the shape and sharpness of the filters in the crossover region. As you can see from the graph, the filters have steep slopes (this is a confirmation of their LR nature). As to whether this will effect the overall sound in the all-critical midband, I can't be sure.

    One very important thing to keep in mind is this: if the subwoofer and main speakers are at slightly different places in your room (I'm sure that they will be) there will be time differences between the signals arriving at your ears from the sub compared with main speakers. This difference could be of loudness or phase - simply due to the longer/shorter path lengths to your ears and the slow velocity of sound waves equating to phase shifts in the audio band. I'd think that it would be really essential that the sub has a variable phase control that you can experiment with to bring the sound from the sub and main speakers into best possible phase (time) alignment.

    Be realistic about what can be achieved at low frequencies in a real-world living room.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

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    Default Re: Yet another subwoofer integration question

    The said sub is active. It takes full range L and R signal from preamp, strip away the low frequency, output only high band signal (>90hz) to poweramp and then main speaker.

    Yes the sub has continuous phase control from 0 to 180.

    While I also think 90hz is a bit high, having user selectable high pass cutover frequency will be perfect. But I wasn't aware any of such product exists in the market, most of product have fixed high pass frequency range from 80hz to 120hz.

    I have also googled a HHB brand sub (model Circle 1) that I am not sure whether it was your design? It has highpass frequency fixed at 120hz, maybe it was meant for small satellite spk. The product was unfortunately discontinued for long time.

    BTW, how don't BBC people think about sub? Do they use any with Harbeth monitor?

    Kevin

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    Default Re: Yet another subwoofer integration question

    I'm really surprised that there isn't an analogue active subwoofer with a variable subwoofer-cut off frequency - but after consideration I can see why. It would involve making many components that are normally fixed into variable ones, with all the resultant reliability and connection problems. But a digital subwoofer would allow total flexibility - is there one?

    Yes, I did design the active Circle 1 subwoofer. As you say, it took the line-level signal, stripped off the higher frequencies and passed only those to the satellite front channels. It may be of interest for you to look up Dolby's background research on why 120Hz was picked as a maximum turnover frequency: it was not a number plucked out of the air. I thought my cut-off frequency was lower than 120Hz but you might be right - it was about 10 years ago now.

    I don't know of any professionals using subs with our speakers.

    P.S. Out of respect to our forefathers we always capitalise the first letter of their name.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

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    Default Re: Yet another subwoofer integration question

    Alan,
    Thanks for the reply. It really helps to confirm that I’m heading the right path.

    And I should be clear that there are not many subwoofers with selectable high-pass output for connecting main speaker. Most subwoofers however have variable frequency control to stop the sub from giving mid-high band frequency.

    P.S. You are absolutely right, typing convenience shouldn’t be used as an excuse for not capitalising family name. Is it possible that I can modify my registered user name please?

    Rdgs,
    Kevin Tsang

  6. #6
    Vlado Guest

    Default Re: Yet another subwoofer integration question

    Quote Originally Posted by A.S. View Post

    I'm really surprised that there isn't an analogue active subwoofer with a variable subwoofer-cut off frequency
    Hello Alan, hello Kevin,

    please take a look at this: http://bryston.com/crossel.html - maybe will help.

    Kindly

    VA

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    Default Corrected link for Bryston sub controller

    Quote Originally Posted by Vlado View Post
    Hello Alan, hello Kevin,

    please take a look at this: http://bryston.com/crossel.html - maybe will help.

    Kindly

    VA
    I tried the link posted Vlado, but it didn't work. Perhaps this might help:
    http://bryston.com/products/other/10B-SUB.html
    Paul

    "If all else fails, read the instructions"

  8. #8
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    Default Sub with Monitor 30s

    I would simply run the SHL5 full-range and dial in the subwoofer to complement the SHL5 in the low frequencies (for example using a 40-50 Hz crossover). You don't get the benefit from taking bass out of the SHL5, but the simpler arrangement will probably still sound better and will leave the signal the SHL5 is getting well alone.

    I am doing the same with my Monitor 30 and it works like a charm. Be sure to get a subwoofer that can play very clean and with very low distortion, as distortion is the deciding parameter for sound quality in a subwoofer (apart from how deep it will go).

  9. #9
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    Default My sub with SHL5

    Quote Originally Posted by garmtz View Post
    I would simply run the SHL5 full-range and dial in the subwoofer to complement the SHL5 in the low frequencies (for example using a 40-50 Hz crossover). You don't get the benefit from taking bass out of the SHL5, but the simpler arrangement will probably still sound better and will leave the signal the SHL5 is getting well alone.

    I am doing the same with my Monitor 30 and it works like a charm. Be sure to get a subwoofer that can play very clean and with very low distortion, as distortion is the deciding parameter for sound quality in a subwoofer (apart from how deep it will go).
    Wouldn't the SHL5 start distorting sooner than a typical subwoofer at those low frequencies? (And therefore lose the benefit of that low distortion) Or does Harbeth integrate a high pass filter in the ported speakers?

    {Moderator's comment: No Harbeth do not implement a high pass filter since that would need very large, expensive components if possible at all.}

  10. #10
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    Default Not pushing power to the very limit

    Quote Originally Posted by TimVG View Post
    Wouldn't the SHL5 start distorting sooner than a typical subwoofer at those low frequencies? (And therefore lose the benefit of that low distortion)
    It totally depends on how loud you play (which itself is a factor of taste/habit, size of the room, amount of damping in the room and listening distance)... To make a SHL5 audibly distort is pushing the limits of the speaker anyway, so don't go there, with or without a subwoofer. With normal listening levels (so anything below 95 dB), running a SHL5 full-range will not pose any real problems. If you need higher SPL's, buy the Monitor 40.1 and a beefy amp... :)

  11. #11
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    Default Using a professional electrinic solution

    Quote Originally Posted by garmtz View Post
    It totally depends on how loud you play (which itself is a factor of taste/habit, size of the room, amount of damping in the room and listening distance)... To make a SHL5 audibly distort is pushing the limits of the speaker anyway, so don't go there, with or without a subwoofer. With normal listening levels (so anything below 95 dB), running a SHL5 full-range will not pose any real problems. If you need higher SPL's, buy the Monitor 40.1 and a beefy amp... :)
    I would recommend using a high quality electronic crossover with active subs if you play music with extreme low frequency content.

    a) you can select crossover frequency and slope to suit the room and your main speaker placement and the capabilities of your main speakers.

    b) by removing the heavier bass component from the main loudspeakers with a good high slope crossover at greater than 6dB/8ve you significantly reduce the power demand on both the main speaker and it's amplifier, allowing higher playing volumes before distortion. This has the additional advantage of reducing intermodulation distortions.

    I have B&W 12" subs which have their own electronic (low level) crossover built in. I discovered that my Monitor 30s sounded worse with the B&W crossover in circuit than when they were fed directly. So I installed a quality electronic crossover.

    My crossover is to my ears acoustically transparent both to the filtered (75Hz @18dB/8ve*) music minus low bass fed to the M30s, and to the (75Hz@12dB/8ve*) bass fed to the subs which, whilst sounding impressive on thunderously huge orchestral works never impinge on the enjoyment of a string quartet or piano solo, or voice. They did take a little setting up though but it's worth the time and effort as they integrate really quite well!

    *The crossover slopes are different for the HF and LF as the B&W has a low pass filter built-in.
    Paul

    "If all else fails, read the instructions"

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