SVS questions..Why can't I turn it up? Speaker seems very fragile. 20-39 PC+ (1 Viewer)

[Richard_B]

Here is something off the SVS site about how to Calibrate the Sub. Hopefully it may help. I can't imagine that sub bottoming out. Maybe there is something out of Phase too.

FAQ # 10 http://www.svsubwoofers.com/faq.htm#meter

 

[RichardH]

*never mind, Ed explained it better than me*

 

[Tom Vodhanel]

Hi Brian,

That is sort of like asking...why a high performance engine can be *revved* to 7000rpm if I can't take off from every stop light at 6500rpm and not hear any funny noises from the clutch after a few hundred miles..

The amp power CAN be used, without any problems at all. BUT, the subwoofer has to be well matched to the listening environment and it has to be well calibrated. Believe me, if you aren't happy...we aren't happy. If you are still within your 45 day trial period email me at techsupport and we'll see if we can convince you to try out a PB-2 instead of the PC+...I think the larger PB-2 will be much better matched to 6000+ cu-ft. Even then, you'll need to calibrate the subwoofer for best performance though.

There is a saying in the industry..."idiot proof". This isn't directly at anyone in this thread of course...but this saying implies a subwoofer which cannot be damaged no matter what. So if someone calibrates the system and finds the subwoofer volume control only needs to be set at 10% to reach proper levels. Then they decide to set the subwoofer control at 50% just because it sounds better on WATERWORLD (for example). Now, with the subwoofer over calibrated by up to 9-15dBs..they pop in a DVD like the new Matrix or the Two Towers and wonder why the driver is making funny noises or the subwoofer keeps blowing its fuses. To counter this type of abuse, most subwoofer manufacturers use very restrictive limiters. The good news is...you can turn all the little knobs all the way up and you still may not damage anything. The bad news is...these same limiters are often filtering the most dynamic parts of the bass from those DVDs...even at moderate listening levels. Sort of like *midnight listening mode* on Dolby digital processors. We don't implement these restictive limiters at SVS because we feel it is important to allow as much of the true bass recording thru as possible.

So there are pros/cons to each way of doing things. The most important issue is for each customer to pick the subwoofer that works in the manner they feel is best for their particular situation.

Tom V.
SVS

 

[Chriss M]

what you're not grasping is that it's not a volume control, it's a gain. SVS does not know what receiver or pre-amp you will be using, and each one outputs from the sub-out preamp at a different level. The higher the output from your receiver, the lower you will need to set the gain on the SVS. The range of the knob is designed to handle a wide range of input voltages. It has nothing to do with how much "power" or amp wattage you are using.

 

[Geno]

"Ok Tom, I set it to 20hz, and no ports plugged. The sub is in a corner close to the listening position. I have calibrated every speaker. "

so how does it sound now?

 

[Frank Carter]

The PC line has a completely different woofer than the Plus. The db12 woofer in the Plus can handle the extra power.

Play some bass heavy material you're familiar with and try moving around the room while paying attention to what the bass sounds like. When you get to the main listening position does the bass decrease? If so, then your problem could be room acoustics. When I had my 20-39CS Plus and Samson amp I measured my frequency response after noticing a lack of impact, I found I had a 25dB dip in my response affecting the frequencies around 50-80hz. This made the sub sound very anemic and I found myself turning it up to get that extra oomph and I was finding the limits of the sub before I was satisfied. I moved the location of the sub and the problem went away. If this is your problem there are only two solutions, move the sub or move the listening position.

 

[Brian.Huep]

Thank you, I understand now!! Yes, I was thinking it was a volume control instead of a gain. I also was unaware my receiver was pushing any power to the sub from my preout. Thought those were unpowered.

It makes sense now.

I am headed home again shortly to make some more adjustments, and experement with locations.

Thank you all...

Brian

 

[Geno]

let us know how it works out!

 

[Rob Grim]

Hope everything works out Brian, if you have anymore questions, feel free to ask.

 

[ryan_kramer]

Good luck Brian and here's one more Johnson County, KS resident to add to the pile! (Though I spend most of my time over at AVS Forums... sorries!)

 

[terence]

Brian are you going to keep us waiting on your results? Come on.......give us something!

 

[Vince Maskeeper]

As others have mentioned, it is completely possible to be getting full wattage from the amp with the knob at 40%. This control is simply a gain attenuation that will reduce incoming signal.

Although this example is not 100% mathematically correct, it should help you understand: If the incoming signal is 200% of what it should be for the input sensitivity of the amplifier stage, putting the gain attenuation knob at 50% will result in a net gain of 100%-- giving you full amplifier output power.

An amplifier is an input/output device- at a certain level of input, you will get a certain level of output. All these device have what's known as "input sensitivity"-- which is basically how much incoming voltage do you have to send before getting full output wattage (so if an am has 1.23 volt input sens and 500 watt output- a 1.23 volt signal will, essentially, result in an output of 500 watts).

The knob on the back simply changes this sensitivity. It is not a volume control as you think of it- but a way to reduce the incoming signal-- or to think of it another way- to raise the input sensitivity...

So, if the input sens with the knob all the way up is X volts, now with it at 50% it might be twice as much (or more depending on the design of the attenuation knob). But that just means you'll need more voltage to get to max amplifier output. So, even though the amp is at 50%, it is still capable of full output level!!

Having the knob at 40% just means you'd have to push more signal into the unit to reach maximum-- and if your preamp device has a very high output level- chances are with it at zero- you're simply pushing the full level of voltage that will put the SVS at maximum wattage output...

The key to doing this right is to ignore these relative measures, like preamp setting and amp gain- as they are not standard -- and concentrate on output level-- and calibration is key for that. As has been said, you won't get ref level in that room (that TREATED room no less) in one unit.

You mentioned your old POS subwoofer didn't have this problem-- but the truth is, it did and you didn't know it. Most powered subs have built in limiters to prevent the drivers from bottoming. This is a good idea in theory- but it affects the quality of the sound and messes with the dynamics of the source. SVS decided early on that they would risk damaged drivers rather than put limiting circuitry in their products.

This is a wonderful notion, assuming that you are selling to an informed consumer, and not someone who's attitude is "let's see how loud this can go).

In the case of your old sub- you were getting loud bass from it without bottoming, because the signal was squashed all to hell by the internal limited. Those who have an ear for accurate bass (and not just the AMOUNT) have been buying SVS happily. If you're looking to just lay into it- you might be happier with a limited design, as it won't provide accurate signal- but will be fartingly loud.

-Vince