1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Passive Sub Output Way To Low

Discussion in 'Subwoofers' started by u32t5645, Jul 12, 2005.

  1. u32t5645

    u32t5645
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    There is enough experience and brainpower here to know what the problem is. I just got a new passive subwoofer, VMPS 215. Not getting enough output from it. Actually, I’m getting next to no output. Same results with either balanced or unbalanced interconnect between the pre/pro and the amp.

    Pre/pro – Parasound C2
    - subwoofer enabled
    - crossover set at default 80hz (also tried 50, 60, 70, 90hz)

    Amp – Parasound 5-channel A52 driving mains, center, and surrounds.
    Amp – Parasound 2-channel A23, bridged mono w/400w (8ohms), driving the sub
    Sub – 8ohms, w/built in 50hz passive crossover
    CD – Denon 3910

    For the last 24hrs the folks at VMPS put the sub thru a break in routine, so we know it worked at that time. I’m presuming either a pre/pro soft switch isn’t set properly, or I have a functional problem with the pre/pro, or somewhere in the interconnect cabling, or...

    Been swapping cables around for the last couple of hours. Also tried running the sub off one of channels of the A52 5-channel amp. Neither one made any difference.

    I tried the music channels on satellite, CD via PCM (digtal) and direct (analog). Didn’t make any difference.

    Any and all ideas of what it could possibly be would be very much welcomed.
    :confused:
     
  2. Ultra2man

    Ultra2man
    Active Member

    Joined:
    Dec 19, 2003
    Messages:
    923
    Products Owned:
    1
    Products Wanted:
    1
    Trophy Points:
    43
    Location:
    Biggleswade, Bedfordshire
    Ratings:
    +130
    Try subwoofer disabled. Normally Subwoofer enabled sends al the l.f. to a powered sub. Also setting the mains to large will allow the full range signal to pass through the sub.
    Hope tis helps,
    Mike
     
  3. u32t5645

    u32t5645
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Mains are set to large. The sub is essentially a powered sub…it’s just that the amp isn’t stuffed in the same cabinet as the driver. Nonetheless, I tried your suggestion (thanks!), no difference.

    I did find a settings menu page in the pre/pro for THX. It was set for the sub with a filter on and a sub filter limit of –50db. I turned the sub filter off, and enabled the LF test freq from the pre/pro, then started upping the filter limit. Somewhere around –30db the dog went ballistic. At around –25db I could not only hear the low rumble but I could also feel a pressure in my ears. By –20db the pressure was getting close to painful and plaster started falling off the walls and ceiling. So, the sub definitely works! I left the filter disabled, and set the filter limit at 0db (just in case). I tried a music cd and still no improvement…virtually no sub output.

    Any more ideas?
     
  4. wookie

    wookie
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    try it with all speakers set to small and a 60 - 80 Hz xover.

    The Sub should then work with all sources.
     
  5. Ultra2man

    Ultra2man
    Active Member

    Joined:
    Dec 19, 2003
    Messages:
    923
    Products Owned:
    1
    Products Wanted:
    1
    Trophy Points:
    43
    Location:
    Biggleswade, Bedfordshire
    Ratings:
    +130
    I must learn to read peoples posts properly.
    Yes obviously as you are using a power amp your sub is effectively active so you need sub enabled on the processor. As the other guys have said try setting the speakers to small and play around with the crossover on the processor.
     
  6. u32t5645

    u32t5645
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Got it! Thanks for the help, guys.

    It was a combination of 2 things, both ignorance on my part. (1) That THX filter was suppressing the low end by 50db so it imperative that I disabled that filter. Alternatively, I could have specified a THX-Ultra2 sub in the speaker setup and it would override that filter. (2) Setting ALL of the speakers to small was necessary. Without doing that the pre/pro was trying to cram the bass info thru whatever speaker was set as ‘large’.

    I’ve been playing around with the bass crossover freq a bit but haven’t figured it out, yet. Don’t know why but setting the pre/pro’s crossover between 60hz and 90hz seems to affect the sub’s output, even tho the sub has a built in 50hz cross over. Or maybe I'm not hearing it right and what it is really doing is changing the mains.

    Thanks, again!
     

Share This Page

Loading...