[Ovation]

Here is a plot of my bass response curve. I used the Snapbug Excel worksheet with the Radio Shack corrections. The blue line plots my response from the listening position, vol. set to 0dB (the automatic reference volume of my Integra receiver--my speakers are calibrated to 75dB (also the recommended setting for my receiver as per its manual). I ran the test tones from my laptop to my receiver via analogue stereo phono plug to rca plug cable, with full output from the laptop volume setting.


The sub is a Boston Acoustics PV900. Crossover was set in the receiver at 80hz and the crossover bypass input was used in the sub. Phase was set to 0 degrees and gain was set at about 40% (no numbers on the dial).


Edit:


Can't find way to post the graph so here are the corrected numbers



FREQ RAW SPL SPL (comp)

16 68 79.5

18 79.5 87.5

20 88 95.5

22 92 98.5

25 97 102.0

28 101 105.0

31.5 100 103.0

36 101 103.5

40 102 104.5

45 96 98.0

50 94 95.5

56 91.5 93.0

63 67.5 69.0

71 90 91.5

80 90.5 92.0

89 86 87.5

100 83 85.0

111 77 78.0

125 75.5 76.0

142.5 65.5 66.0

160 59.5 59.0


Any suggestions?

 

[bpape]

Looks like in general, the sub is a bit hot. However you have a pretty serious dip around 63Hz. That is probably room induced. Did you measure this at your seating position?

 

[Ovation]

You're right, the sub is a bit hot (I should have reset it to it's normal gain position before testing). The dip is the main problem, I think and yes, I did measure from the listening position (meter mounted on tripod at proper height, facing up as per many sites' recommendations).

 

[BasementBob]

Ovation


Did you measure from multiple positions in the room? If not, then beware of modes affecting your results.

 

[bpape]

I'd almost guarantee it's mode related. It's so deep and so narrow, there's almost no other cause for it.

 

[fatbottom]

I'll be buying a BFD soon. I would appreciate it recommendations at what frequency, width, and gain to set filters. see pic.

thanks

 

[bpape]

Ovation, I'd try moving the sub around a bit to see if you can smooth it out a bit.


Fatbottom,

Is that a composite of your mains and your sub? If so, your sub is set way too high in level.

 

[fatbottom]

Test is with subwoofer only switched on, all other speaker poweramps switched off. All crossovers to 80hz, subwoofer to 80hz (sub xover disabled) set to 2 channel mode. No need to worry about burning the VC's out- the sub is only 6' away. I needed to set it a bit high because it trails off abruptly (crossover set to 80hz) and wanted to be sure the RS meter will pickup at a decent level (doesn't seem too accurate to sub 60dB) Once I bring down 20hz area I'll re-test at a lower level.


btw I can't get the latest BFD software to work (version 2)- double clicking on the EXE just does nothing. Version 1 works though. Also laptop doesn't have joystick connector- any USB/pararel/serial to joystick/Midi adapters?


My guess is a 7dB cut at 21.5hz should be OK? Not too sure of bandwidth. Don't know what to do about 53hz-63hz dip.

 

[bpape]

6db boost @ 60Hz, 2db cut @ 70, 4db boost @ 80. Make the 60 fairly narrow, the 70 narrow, and the 80 a bit wider. Leave it alone from 30+ down. It's really not that bad, especially if its smooth among seats. A little extra between 20 and 30 never hurt anyone.


No way in #(*%& would I put in a 7db cut @ 20Hz. Leave it alone. You're lucky if that's half way accurate and repeatable among all the other seats.

 

[HT-DJ]

Fatbottom:


Your graph looks a little too smoothed... is it possible to re-run that at 1/12 octave resolution? If you can, my guess is that you'll find that it's not quite as smooth as it appears in that graph. If you use a Behringer to flatten that out using 1/6th resolution, you could very well be just covering up problems that are invisible on the graph, but audible nonetheless.

 

[fatbottom]

I've got all of snapbug's tones, however I can give you the value on the RS meter for every tone (all upto 160hz should do), but how can I plot a accurate graph if I don't have correction values for each one?


This is all so confusing :-(

 

[Ovation]

I have the same question, as I would like to re-run my measurements at each frequency.

 

[fatbottom]

I think purchasing a calibrated microphone would make sense; that way can measure in much higher detail, and just plot without any corrections at all.


Once that's done though need to take into account mains interaction...seems a bit too complicated- if meter is off, or incapable of plotting detailed grapg then could make it worse. I think. ;-)

 

[Ovation]

Of course, as I contemplate all this tweaking, I remind myself that I've never had sound as good as I have now, and how much better does it have to be? The eternal question around here, I suppose.

 

[warnerwh]

Go to realtraps and rives audio and read. Learn about room acoustics and your system will sound much better. Also room treatment is very cost effective when you consider the large gains.

 

[bpape]

Not so much how much better does it have to be as


How much better could it be for what I've already invested.

 

[Ovation]

I re-ran the frequencies (started at 20hz this time) with mains on, at 60, 80, 100 and 120hz xovers. (-20dB from reference to avoid running the sub hot again. Gain settings are still the same as last time). Still haven't figured out how to post graphs. Sorry about the messy numbers layout, it looks alright when I'm typing the message but not after it's posted.


FREQ RAW 80hz SPL (comp) RAW SPL 100hz SPL (comp)

16 0 11.5 0 11.5

18 0 8.0 0 8.0

20 69 76.5 68.5 76.0

22 74 80.5 74 80.5

25 79 84.0 79 84.0

28 80.5 84.5 81 85.0

31.5 81.5 84.5 82 85.0

36 82.5 85.0 82.5 85.0

40 83 85.5 83 85.5

45 78.5 80.5 78 80.0

50 70 71.5 71.5 73.0

56 73.5 75.0 73 74.5

63 64.5 66.0 66 67.5

71 73.5 75.0 73.5 75.0

80 75 76.5 76 77.5

89 74 75.5 75.5 77.0

100 77.5 79.5 78 80.0

111 80 81.0 79.5 80.5

125 72 72.5 74 74.5

142.5 75 75.5 75 75.5

160 75 74.5 74.5 74.0




RAW SPL 120hz SPL (comp)

0 11.5

0 8.0

69 76.5

74 80.5

79.5 84.5

81 85.0

82 85.0

82.5 85.0

83 85.5

78 80.0

72 73.5

73.5 75.0

66 67.5

73 74.5

76 77.5

76 77.5

78 80.0

79 80.0

74 74.5

74 74.5

74 73.5



RAW SPL 60hz SPL (comp)

0 11.5

0 8.0

68.5 76.0

73 79.5

79 84.0

80 84.0

81.5 84.5

82 84.5

83 85.5

79 81.0

70 71.5

70.5 72.0

59 60.5

72.5 74.0

74 75.5

72 73.5

78 80.0

80.5 81.5

72 72.5

76 76.5

74.5 74.0

 

[Ovation]

I have graphed them, but the system won't let me attach the graph (it's in Excel). At least I haven't found a way to post the graph. RAW 80hz SPL (and the others) means crossed over at 80 hz (or 100hz etc.). I ran the test tones at -20 dB from reference (which on my receiver is 75 dB via the internal test tones at a setting of 0 on the volume control) to avoid potential damage. My very first run was done at the 0 setting (hence the higher spl numbers).

 

[HT-DJ]

Ovation:


While the graph is on your screen, press Alt-PrtScr, then open MSPaint, and paste the graph into MSPaint. Save it as a .jpg, and try to attach it again.

 

[Ovation]

Thanks, will post them as soon as I've prepared them.