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Help - Decypher a SPL/Freq Graph??


tankhokie
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I got my sweaty hands on a RS analog SPL meter today and eagerly took measurements to calibrate my new SVS w/Klipsch's....now I got a cool graph and no clue what to do next. Normal graph? Bad peaks/nulls? I just dunno.

I did:

Slow response, C weight, at sweet spot, see below for speaks/amp, set my ref level to 00 and leveled all to 75dB using test tones, speaks to small, LFE cut at 80Hz, disabled SVS x-over, added in correction factors, and now what??

Do I need a BFD/EQ?

It feels like I am missing some ranges but this was before I calibrated with the new sub, can you tell if I need to calm down some of those peaks?

Thanks again guys.

post-10593-13819248820286_thumb.jpg

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Nice graph. Looks normal. You can't do much about the peaks. Maybe some room treatment.

But man you must be deaf if you did the full frequency at that level. The normal procedure is to set the 1k at 75 db.

Now you have 1k Hz at 100 db. Waaw.

I see 2 majure dips starting 60-400 Hz and 2500-20000.

Did you measure it with all 6 speaks operating!!

You should measuring just two speakers (+sub), not all of them.

They will cancel each other out or add up at some frequencies.

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Looks like you need to turn the subwoofer down. Also, look for distances that could cause reflections that reinforce/cancel the signal. For example 600 Hz is 1.9 feet. How far from the wall are your speakers?

Wavelength, in feet = 1130/Frequency.

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Thanks guys, so now I have just run the freqs again but:

1. I set 1000Hz at 75dB (easier on the ears too)

2. I only output through the 2 fronts and sub

I am putting the graph together now.

John, I do not follow about the distances and freqs. I have attached a sketch of my setup including all distances.

I will post the graph in a few, but in the meantime, do I need to worry about any of these distances?

post-10593-13819248821286_thumb.jpg

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Im sure many forum members know much more about subwoofers than I and all are willing to help you. Being a SVS sub owner like you I also made a graph. What I did with it was send it to Tom Vodhanel at techsupport@svsubwoofers.com including how I took the measurements. Take my word for it. They are not in the business to sell a lot of equalizers. Theyll tell you the truth concerning any improvements that can be made based on your graph, how you took the readings and the dimensions of your room. Based on SVSs response and the forum members opinions I think youll figure it out. Good Luck.

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Looks better now. I see directly that the sub is way to high. For music anyway. That is almost 20 db difference with the calibrated 1k at 75 db. For HT it can be desirable but for music it can be to boomy. The dip at just over the 80 Hz may indicate that the RF3's are canceling out the sub at that frequency. You should try switching the polarity of the sub.

For the other frequencies it is more difficult. That is just how the room sounds. You can change things and measure it over and over again till the peaks are somewhat flaten out.

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1'-8" is 1.67 feet. Rearranging the equation, 1.67 feet is the wavelength od 678 Hz. Isn't that just about one of your Dips? It would appear you are getting a reflection off of the wall that is canceling the energy radiated off of the front the speakers. A peak could be similarly caused by a reinforcement of reflections.

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hmmm,

Thanks John, there is more to this game than I thought, I will have to experiment with how close the mains are to the back wall.

The SVS has a phase knob that I can toy with, but will turning it effect the whole sub-spectrum of freqs?

IOW, will I have to re-run the freqs for the sub again each time I move the phase?

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----------------

On 8/20/2003 4:25:34 PM tankhokie wrote:

The SVS has a phase knob that I can toy with, but will turning it effect the whole sub-spectrum of freqs?

IOW, will I have to re-run the freqs for the sub again each time I move the phase?

----------------

The phase only matters when other speakers are producing the same frequency. So in your case it will only change around the cut-off frequency of 80Hz. Remeasure from 60 to 120 Hz.

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----------------

On 8/20/2003 4:25:34 PM tankhokie wrote:

hmmm,

Thanks John, there is more to this game than I thought, I will have to experiment with how close the mains are to the back wall.

The SVS has a phase knob that I can toy with, but will turning it effect the whole sub-spectrum of freqs?

IOW, will I have to re-run the freqs for the sub again each time I move the phase?

----------------

I've never done any testing to see how broad a spectrum of freq's the phase control can effect, but as USparc said it's centered around the x-over frequency . Instead of graphing the response at different positions of the phase knob, here's how it should be done before you take the mesurements.

With your SPL meter at the sweet spot, play a warble tone(sine will work if you don't have warble tones) at the subs crossover frequency(with Denon I think it's fixed at 80hz). With your meter in the sweet spot, turn slowly turn the phase knob and find the position at which the meter has the highest reading. When the level is at it's highest, the subwoofer is in phase with the mains. Now you can retake the measurements. Don't forget to disable the xover built into the SVS plate amp.

BTW, the RS SPL meter is useless above 8000hz so I wouldn't trust the measurements above it.

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Attached is my latest graph with these changes:

1. Set up video camera and monitor in next room to avoid my body reflections (mainly saw + or - 5dB on some higher freqs) yep I am a freak.

2. Set phase knob on SVS to proper setting to match the RF3-II's.

Seems like a smoother curve, I know I am running pretty hot below 50Hz but I like my clothes to flap during LFE. 6.gif

Here is what I would like to calm down --

56-100Hz that peak would be nice to level off some as it is more noticable during movies

125-200Hz that is a noticable null that I would love to lessen.

I am going to try some sub scootin' to see if that helps (closer/away from corner) Any advice other than this?

Thanks9.gif

post-10593-13819248823496_thumb.jpg

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Here is the best position, x-over, and level that I can get.

I ran a ton of freqs (117 I think) to see if any of those peaks/nulls were singular occurances.

So I looked for a wide freq range peak that may need taking down...but again I how flat of a response is "good"

It all depends on the perspective/height of the graph as to how "flat" it is.

So what do you think??

post-10593-13819248824506_thumb.jpg

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