Film-Tech Forum ARCHIVE: Smart CS-3X

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Posted by Raymond Massard (Member # 2300) on 07-15-2006, 05:33 PM:

Hi. Is anybody out there using a Smart CS-3X Center surround decoder. We've just installed one and there is a distinctive hiss on the surround speakers if the CS-3X is turned on. I hope that this is not "normal". Any experience with that equipment ?

Posted by Steve Scott (Member # 630) on 07-15-2006, 10:05 PM:

We have several older SMART decoders. The center-surround usually outputs a discernable level of hiss, but not to the degree that it sounds like RF interference or distortion. The Ultra Stereo C-S units also put out some hiss when idle, but SMART units are a bit more pronounced.

Is it a steady hiss, or a cycling noise?

Posted by Ron Curran (Member # 3631) on 07-15-2006, 11:34 PM:

Yes, we had the same problem with 2 of those units and finally replaced it with another decoder. I have heard that Smart has tightened up their QC lately. Is this an older unit?

Posted by Gordon McLeod (Member # 33) on 07-16-2006, 04:37 AM:

Never saw a UltraStereo Ex surround adapter

Posted by Mark Gulbrandsen (Member # 72) on 07-16-2006, 07:27 AM:

I typpically find in most systems this is caused by the sound system not having been calibrated properly to begin with. Most if not all processors will exhibit at least some background noise....USL=JS processors are among the hissiest of them all but this can be somewhat controled by lowering the amp gains and increasing the output of the processor. This effectively increases the signal to noise ratio and masks at least some of the processors noise. Forr instance Dolby has certain average output levels for certain processors that produce the best S/N ratios and you may have to experiment with other units a bit to find an optimum point. It is effected by speaker efficiency, EQ levels, amp gain, and the actual S/N ratio of the processor. Most inexpensive processors will have poorer S/N ratios than the more expensive unitts will. You can also send your unit back to Smart and have Don check it out to see if it meets specs or not. It might be bad or that might also just be the way they are.

Mark

Posted by Raymond Massard (Member # 2300) on 07-16-2006, 11:24 AM:

The unit is quite new and the hiss is also clearly present in the left/right surrounds.

Posted by Louis Bornwasser (Member # 3063) on 07-16-2006, 11:29 AM:

I agree with Mark that this is a gain structure problem. Experiment with driving it harder and reducing the input level at the amp. Maybe you can get an acceptable operation. Louis

Posted by Steve Scott (Member # 630) on 07-16-2006, 04:13 PM:

True Gordon. Wouldn't the process of the new Back Surround decoders for digital soundtracks be somewhat along the lines of the process used in the older SMART's which were for SVA tracks? What if any is the significant change in processing?

Just asking, not debating.

Posted by Gordon McLeod (Member # 33) on 07-21-2006, 01:56 PM:

The back surreound decoding is the same as any matrix decoder
The CS unit is DSP based I believe and as such may have a bit more digital noise than an analogue one Typically Smart stuff tends to be quiet
grounding and setting up the gain structure of the system is important to maintain a quiet sounding system

Posted by Demetris Thoupis (Member # 833) on 07-21-2006, 03:41 PM:

Back Surround is like the Digital Cinema. It won't survive [Smile]

He he he

Posted by Oscar Neundorfer (Member # 458) on 07-22-2006, 08:44 PM:

quote: Raymond Massard
The unit is quite new and the hiss is also clearly present in the left/right surrounds.

These are what I would call NOS (New Old Stock). They have not been made in several years, unless SMART made a new run which I seriously doubt. However, that should be no problem at all.

One thing to check is to make certain that the surround EQ in the regular processor has been set to be flat, or completely bypassed if possible, and do the EQ in the CS-3X. For proper decoding, the LS and RS signals feeding the CS-3X need to be as well matched in level and as flat in frequency response as possible. Since noise in a system is cumulative, it would be preferable to bypass the processor surround equalizers to eliminate a source of noise. This is not always feasible.

Setup can be pretty critical on these in order to get the best performance. When properly set up, hiss should really not be a problem.