Servo 15

Discussion in 'Speakers & Subwoofers' started by Lee Batchelor, Feb 10, 2006.

  1. Lee Batchelor

    Lee Batchelor Auditioning

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    Greetings all. I'm knew to the group and many thanks for having me. This looks like a great place to ask questions and already I feel at home!

    Anyway, I have a rather large home theatre system and need some help on integrating my Paradigm Servo 15 with my L/R channels. The L/R speakers are Altec A-7-800's in 10 cubic foot domestic cabinets. (15" LF units). I'm driving these with a 6 year old Sony amp; 110 watts per channel. The L/R are set to "large" while the rest of the system is set to "small". The room is 22'x34'. I sit about 16 feet back from the system. ( When I sit at the 32' mark it sure sounds good. Perhaps the wavelengths of the Servo 15 are too long for the 16' mark.) It is in the basement but completely finished with drywall, carpet and suspended ceiling. The room is quite "dead". My problem is that when the sub kicks in it does the tricks it's supposed to do but it just isn't what I classify as "musical", either on movie or CD playback. I've gone through the exercise of placing the Servo 15 where I sit and listening for the smoothest bass response and then moving the sub to that spot. The controller unit for it has a variable phase dial and frequency cutoff. I currently have it cutting off at 100 Hz. The sub is fairly close to a corner. I had a PSB Sub-Sonic 6 (12" driver, vented) prior to the Servo 15 and it sounded much better. I'm I getting too much bass? Perhaps I'm saturating the room despite its large size. Having read some of the fine articles on this site the only thing I think I could try is to set all the speakers to "small".

    Your help and input would be very much appreciated. Many thanks folks!......Lee
     
  2. Greg_R

    Greg_R Screenwriter

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    Greg
    Nope. Room size and audible frequency have little to do with each other in this situation. You can hear/feel 10Hz in a small compact car and that wavelength is much longer than the vehicle.

    It sounds like you've been listening but have you measured? If you have not analyzed the response by using a SPL meter and test tone source (CD, etc.) then you are operating blindly. Also, if the sub is set too 'hot' it will sound bloated and boomy (because it is overpowering the upper frequencies).

    Problem A) You have 3 LF sources in the room, 2 of which are likely placed symmetrically (your mains). This can create a difficult calibration situation. I would suggest having the mains and sub cover different frequency ranges. If this means setting your mains to 'small' then I would try that. Don't worry about "wasting" your mains... a crossover is not a brick wall and your mains will still need to play strongly down to 40Hz or less.

    Problem B) 32' in a 34' room is WAY to close to the rear wall for good imaging (unless the last 2 feet is sound absorption). Yes, it is quite possible to have standing waves in a room but that can be fixed by moving the sub around. Your mains should be at least 3' off the front and side walls.

    Problem C) If you are not using the crossover in the sub then set the 'cuttoff' to the maximum position (i.e. no cutoff).

    Problem D) Is the phase set correctly? Play with the phase knob while viewing your SPL meter (you want max output).
     
  3. Lee Batchelor

    Lee Batchelor Auditioning

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    Hi Greg and thanks for the reply. The mains are fairly tight to the wall beside the big screen so yes, I can pull them out a bit. The Altec forum guys said they should be toed in slightly which should offset the symetrical geometry you mentioned. I have used a test tone for setting the phase relative to the mains. It would seem that the Servo 15 has to be out of phase by 120 degrees to achieve maximum output. (I do own one of those SPL meters from Radio Shack.) You mentioned about not cutting the Servo 15 off at all. Did you mean to let it fill the frequency range right up to 150 Hz, its maximum setting? I am also running the sub pretty hot, thinking that it has to rise over the mains but like you said, I'm probably drowning out some of the main's frequencies thus losing the musical characteristics of the VOTT system. Thanks again for the help. I'll try out your ideas and post back...Lee
     
  4. Lee Batchelor

    Lee Batchelor Auditioning

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    Hi again guys,

    I did some fiddling today. I hooked the system up to an older model Yorkville powered mixer. (I'm also a keyboardist with several bands.) This is only good for stereo CDs but I couldn't believe the difference! I used two mono channel strips for the L/R in from the CD player and the monitor send to the X-30 Paradigm processor for the Servo 15. The Servo 15 sure knows what to do with the spectrum if you give it half a chance. My conclusion: the Sony amp I'm using is crap. Its bass re-direction circuitry is poorly designed and probably ment for the $399.00 HT in a box type of system you would use in a den or small living room. Since I'm using Altec VOTT drivers, it's time to purchase a decent amp for large home theatre.

    Thanks again guys and I'll keep you posted as to the progress. Any other VOTT users out there?..........Lee
     
  5. Andrew Pratt

    Andrew Pratt Producer

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    Hi Lee welcome to the forum! My parent used to live in Port Hope but are not in Port Perry.

    You mention owning the SPL meter but didn't mention if you'd calibrated the speaker levels...and if so with what?
     
  6. Lee Batchelor

    Lee Batchelor Auditioning

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    Hi Andrew! Small world.

    Yes, I did some calibrating before Christmas using a downloaded tone generator and spectrum analyser. The analyser is a freebie and only calibrated by 1 octave increments but it is probably close enough. I also used it for checking the alignment of my Altec LF and HF drivers in the new boxes I designed. I found a pretty severe gain just above the x-over frequency of the horn/LF driver which I was able to correct by tipping the horn forward. (It sits on top of the cabinet.)

    As for the overall bass response of the room I used tones from 150 Hz and lower to get the phase correct on the Servo 15. As I mentioned in my last post, I hooked it all up to my Yorkville mixer and what a difference. The folks at Whitby Audio (where I bought the Servo 15) indicated that the Sony may be the weak link. I think they're right. Maybe time to go shopping, pending a WAF hearing.[​IMG]

    Thanks and regards Andrew......Lee
     
  7. Randy C Sr

    Randy C Sr Stunt Coordinator

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    I would also suggest to move the crossover point to 80hz instead of 100hz. That will eliminate some of the boominess you were getting. If that Sony has a pre out you may be able to get away with just purchasing a good power amp for the fronts. Whatever you do, make sure you at less double the power output. You said yoy have 100 wpc, so get something with a minimum of 200 wpc.
     
  8. Andrew Pratt

    Andrew Pratt Producer

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    I purchased a Marantz CD changer from Whitby Audio a few christmas's ago. Which Sony receiver do you have?
     
  9. Lee Batchelor

    Lee Batchelor Auditioning

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    Hi Andrew,

    I'm using the Sony STR-DB840. I believe it's 110 watts/channel.

    One thing I've done and it's seemed to help a lot was to tip all three speakers back a little bit, in effect, uncoupling the bass from the floor, which is carpeted. There now seems to be better definition between the mains and Servo 15. The ports on the mains and the Servo 15 driver are directly aimed at the sitting area.

    What do ya think?.......Lee

    Also, how does one post pictures on this site?
     

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