Notes on Amplifiers for Driving SVS CS-Ultra

Discussion in 'Archived Threads 2001-2004' started by Lee Whitney, Dec 4, 2001.

  1. Lee Whitney

    Lee Whitney Auditioning

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    When I first listened to my CS-Ultra, I knew it was a great choice, and in fact posted here about how impressive it was even being driven by a 9-year old Technics receiver.

    I just upgraded the Technics receiver to a Samson S700 amp, and thought some might be interested in hearing comments on the comparison.

    I hate to say this, but after just now running through the TS2 and TPM intros, my first impression was to be under whelmed.

    The Ultra sounded excellent and quite powerful with the Technics. Honestly, it is difficult for me to tell the difference between it and the stand alone, 350w Samson Pro Amp. I'm trying to make some sense of why this is, and admittedly pilot error is a possibility, but for now it has me wondering if I should have gone with an amp that could have delivered a clean 600-800 watts to the Ultra.

    If anyone has comments on their own experiences comparing amps in a similar scenario I'd be interested in your feedback here.

    Before anyone replies with a lesson in loudness theory, I do understand the basic non-linear relationship between power and sound, namely I am aware of these simple facts:

    - You need to double the power to get a 3db increase

    - 1db increase is the smallest perceptible change in loudness

    - Thought I also heard that a 10db increase is often perceived as "twice" as loud, but not sure on this one.

    Also, some things that may be a factor in the Samson being unimpressive:

    - I didn't use an SPL meter. I assumed that a 5db increase would be easily noticeable but maybe my mind is playing tricks and I need to measure it both ways.

    - Not sure if the levels are set right. I run the Samson level with the notch pointed at 3 o'clock (looks like about 75-85%), and I bumped the Denon 1801 SW output to +6db (it had been +3db with the Technics). At +6db, the Samson subjectively sounded *slightly* louder.

    - My room is huge because its an open family/kitchen/living space. But I wouldn't expect this to lessen the distinction between amps.

    - The receiver in question is the Technics SA-GX650. It's rated at 100w/c x 5. Maybe while driving only one channel this receiver well exceeds its rated output? This could narrow the expected delta with the Samson.

    - The Technics (released in '93) seems more ruggedly built than newer receivers. For example it is significantly heavier than a Denon 1801. Maybe since surround sound was newer at the time manufactures didn't yet realize they could lie silly about rated power by not driving all channels (like all manufactures do today)?

    - One unfortunate aspect of the Samson is that it cannot handle a 2ohm load well enough to drive the Ultra in bridged mode (1x700w/c), at least not without voiding the warranty. This is my own screw up for not realizing this in advance - I normally expect high quality amps to be able to drive tough loads, most high-end amps can, but I mistakenly did not do enough due diligence on the S700. Also in retrospect I think I assumed since SV sells a bridgeable amp, and that most of their sub customers would have use for bridging, that the Samson could handle this. Maybe I should have gone for the Crown?

    Regards,

    Lee
     
  2. John Cain

    John Cain Second Unit

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    Lemme take a stab at this one..

    1) The Ultra is a very efficient Subwoofer and makes better use of lower power than does other similar class Subs..

    2) More power really buys you more headroom and dynamics, not necessarily more "slam".

    3) I'm also going to guess that music would be where you would notice more headroom, not sound effects from movies necessarily.

    I'd say trot out some top-notch well recorded orchestral music that features a large pipe-organ.

    -- John
     
  3. John Cain

    John Cain Second Unit

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    Oh yeah, thanks for the post, it reminded me I have been so busy I had forgotten to order my CS_Ultra !!!

    -- John
     
  4. Ned

    Ned Supporting Actor

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    You'll notice a big difference when the Technics clips. Below that level I would expect absolutely no difference.

    Just play the Phantom Menace THX trailer at reference level and you'll probably see it happen.
     
  5. Tim_S

    Tim_S Stunt Coordinator

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    What is going wrong I can't say. My guess would be a level adjustment. I can tell you that when I got my Ultra, I was initially driving it with a channel off of my Anthem MCA-5 S2 amp which is a very nice amp and rated around 200 WPC (well, ok with all channels driven closer to 180 I think). The Ultra was very nice.

    When I hooked it up to the Samson 1000 it was an astounding difference. Not just in volme, but in overall presence. The fact that you are not noticing anyhing between a receiver and the Samson strikes me as something being wrong. I would say the most likely cuplrit is a level adjustment being needed.

    Tim
     
  6. RichardH

    RichardH Supporting Actor

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    Run the Samson wide open, or close to it, and throttle back on the Denon's sub output. You don't want to be sending any distortion to that Samson.

    As to the loudness issue, I think you pretty much know what's going on. Below a certain point, there's just not going to be that much of a difference. If you weren't pushing the Technics before, and you're only bumped up a little from that, you're not going to hear the headroom the Samson got you.

    Hook the Technics back up, and gradually play stuff louder and louder, until it gives up. Note where that was using an SPL meter. Then go back to the Samson, and see where *it* gives up.
     
  7. ling_w

    ling_w Second Unit

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    I thought the Technics had the Class AA amplification circuitry, which produced infinite headroom into vanishing impedence?

    I think if you peel off the sticker that is to the left of the SAMSON logo, you would see the letters ITE.
     

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