SVS and eq

[gtDark]

So I burned a cd with some test tones Saturday. From 10Hz up to 100Hz in 5Hz increments and from 100Hz to 200Hz in 10Hz increments to see/hear frequency response in my room and make sure the SPL level is approximately maintained when I crossover from mains to sub. Well everything is pretty good, except at 90 Hz and 35 Hz where I get no response at all. At 40Hz I'm fine, and at 30 Hz I'm fine, but like no reading at all at 35Hz. Do you think an equalizer could give me the flat response I'm looking for since this is a room acoustics problem (is this a room acoustics problem)?

P.S. Anyone have trouble getting the top of the SVS off to access the ports? I'm afraid if I force it too much I will break something.

[Bruinsrme]

Ron S talked about this over in the avsforum click for the link

SVS Instructions

[gtDark]

Thanks for the link bruinsrme. I actually started reading that thread a while ago, never got to page 60 though! I tried using a flathead screwdriver, but decided to stop before I did something I might regret later. I'm definitely going to plug one port, I have no output to speak of below 20Hz, and total output level isn't as important to me (multifamily dwellings).

On an somewhat unrelated note, I'm still playing with sub settings to get a seamless integration into the system so I don't notice the sub's presence so much when I play music. Still not happy with that though, any suggestions? I'm going through the AVS Forum thread again now.

[tankhokie]

Dark,

I have the almost identical setup as you (minus the 20-39PC+ I am ordering today) and just wanted to ask you about your testing.

Not being too familiar with checking my room response, are you simply measuring dB's at different freq's? That is where I assume you found your null. My limited understanding is that an EQ will only flatten out peaks in response--not fill nulls.

That aside, how do you like that sub with your Ref 3's?

[formica]

You are correct in thinking that these nulls are part of the room response... as well as the inversed peaks (although you didn't mention them). Are you using the RS SPL meter? Don't forget to add the correction factors, as the meter's response isn't flat either.

If you would like to tune your room, I'd recommend 1/6 octave test tones or even all the frequencies rather than 5Hz steps, as your nulls seem to be a little off from each other (but I may be wrong). I'm just mentioning this because if the first measured null is at 35hz my guess is the second one would be at 70hz if you have one predominant effect... (or 45hz and 90hz... ) . Nulls and peaks are very room/placement dependant... and an easy way to see this is take all the readings at the centre of the room, and then again up against one wall. Notice how the nulls/peaks change frequencies? The same is true if you leave the meter in one place and move the sub around the room to different locations (corner, mid wall, etc...)

You are also correct that a EQ can't fill a null efficiently... to increase output by, lets say 15db in the null, you will need 16 times more power at that frequency!! (ie: 500W versus 31W) Given that the nulls will vary according to location in the room, over EQ'ing will make you sub sound very boomy everywhere else in the room. BUT if you reduce the main resonant peaks, you will notice that the nulls will also decrease, as they are all associated through wave physics.

To get a flatter response, I'd recommend EQ the sub's peaks for an average listening area.. and the rest will balance out.

Don't be shy to post more questions...

Rob

[Bruinsrme]

For music I usually set the receivers sub output level 3 to 5 clicks up, meaning

If the sub output level is +3 for movies I will bump it up to +6 or 7.

These are hypothetical numbers but I do bump it up.

I too was not impressed witht he level of bass during the music experience but bumping up the level definitiely helped.

also haveing 2 PC+2039s I calibrated them with the receiver setting a little at -4 and used the gain on the subs to achieve the reference level, the sub gains were at 45% and 52% now they are at 55% and 65%.

The SVS compliment the RF7 in the low end nicely, but the SVS seems to need an little power help when it comes to music.

scott

[gtDark]

tankhokie:

To be honest the SVS wasn't all I expected, but I'm sure this is just because of my setup. I have wood floors, and it just seems to me that I get too much vibration under my feet and occasional boom instead of clean audible bass (even in music). Nevertheless, with that said, I'm very hesitant to make condemnations/strong opinions at this point because I firmly believe that I am not giving the SVS a "level playing field" to demonstrate its capabilities. I feel I can get the problems worked out through a combination of settings and room issues.

I have my sub in the second best position I found using the "crawling for bass" method. The primary/best sub position was in a corner, but it transmitted too many vibrations to the neighbor (townhouse) and got the cops called on me multiple times.

I personally preferred the RSW subs to the SVS I hear now. Notice the emphasis is that the RSW12 might give me the same problems I have now if placed where the SVS sits.

formica:

I also have a peak at about 55Hz. I am using the RS SPL meter and know about the adjustments, at this point though I don't really know what I can do with them since I don't have an EQ; all I can change is gain on the sub, gain on the sub via receiver, XO point, and maybe phase. I was just playing around to see what I could see.

I appreciate your insights into using EQ's; I am quite ignorant on the subject so I've learned quite a bit already in this thread.

"If you would like to tune your room, I'd recommend 1/6 octave test tones or even all the frequencies rather than 5Hz steps ".

Maybe I'll re-test tonight after work, what frequencies occur at 1/6 octaves? I should know this, but Tech doesn't teach me anything useful. All I know is how many octaves are in a certain frequency range given its highest and lowest frequencies .

[Bruinsrme]

be sure to add/subtract the SPL corrections provided by SVS

[formica]

As far as i know, these would be the 1/6 octave frequencies between 10hz and 20khz while the 1/3 octave ones would be every second one. Unfortunately i don't have a text book handy to check these...

1/6 Octave

10

11.2

12.5

14

16

18

20

22.4

25

28

31.5

35.5

40

45

50

56

63

71

80

90

100

112

125

140

160

180

200

224

250

280

315

355

400

450

500

560

630

710

800

900

1000

1120

1250

1400

1600

1800

2000

2240

2500

2800

3150

3550

4000

4500

5000

5600

6300

7100

8000

9000

10000

11200

12500

14000

16000

18000

20000

The RS correction factors, when added to your SPL readings, will give you what the actual frequency responce is. This is important in the bass region as the little meter will read 7.5db lower at 20hz than the actual volume at that same frequency. The lower you go, the more it is off... but what do you exect in an instument which is so inexpensive?

10Hz +20.5

12.5Hz +16.5

16Hz +11.5

20Hz +7.5

25Hz +5

31.5Hz +3

I still think it's a bargin.

I once posted a series of 1/6 octave test tones in the "Technical Questions" forum... its the "test CD" thread...

keep us up to date...

Rob