My sub measurements are a mess will a BFD help and where the hell do I start

[cam]

I always thought my sub was pretty flat in my room, was I ever fricken surprised. I down loaded some test tones and I started making some measurements with my digital rad shack sound pressure meter. I did not use my reference volume because the test tones were just to dam loud, I picked a volume I could stand and was consistent throughout. My tests consisted of 18 hz to 85 hz. If I had a BFD, could it help me and where would I start. Here are my results.

18hz-77db
19hz-79db
20hz-83db
21hz-83db
22-83
23-91
24-94
25-95
26-95
27-95
28-95
29-94
30-94
32-94
33-93
34-92
35-91
36-90
37-89
38-89
39-90
40-91
41-93
42-94
43-95
44-97
45-97
46-98
47-97
48-96
49-95
50-94
51-92
52-90
53-88
54-86
55-82
56-79
57-73
58-71
59-72
60hz-78db
61-81
62-83
63-85
64-87
65-87
66-87
67-87
68-86
69-85
70-84
71-81
72-76
73-76
74-80
75-84
76-86
77-87
78-88
79-90
80-91
81-92
82-92
83-93
84-94
85-94
I start getting some good output starting at about 23 hz but look at 58hz, it just dies. And look at 72hz, It's 1 db lower then at 18 hz which to tell you the truth, when I started at 18 hz I could barely hear anything, if it wasn't for my meter I would have swore my 18 hz test tone wasn't even playing. Between 23hz and 80 hz I could be as low as 71 db and as high as 98db at 46 hz. That is a 27 db difference with alot more differences in the 15 db range. If these were your measurements, what would you do and where would you start.

[kexodusc]

Camster, don't feel bad...I have a +/- 14 difference in my room, though peaks and dips are bit different. It's sick.
Err...you have the PW-2200 as well, right? You actually get better results below 23 Hz than I do, but my room is 20 X 24, I don' think that's helping me.

A BFD is DEFINITELY in your future if you want great bass. Leveling even half of that variance out will produce stunning results.
You should even go higher, some people I know report peaks in the upper bass region up to 120 Hz and beyond as well...you wouldn't Parametric EQ those frequencies, but rather setup bass traps or something.

With the subwoofer you have you owe it to yourself to fork out that $100 USD ($160 CDN plus tax is the best price I've seen in Canada so far) and get a BFD...don't pass up on this while they're still cheap.

Mine's already on the way. I've heard first hand what a good flat bass response sounds like when this unit does it's trick. It's really like getting a new subwoofer...you won't be disappointed.

[Sir Terrence the Terrible]

Mr. Cam type individual,
I would try moving the sub around a bit. A BFD or any eq cannot really help you with nodes, their speciality is modes(peaks) You have a broad node centered around 58hz, try and move the sub around a bit, take more measurements, and see what you can come up with.

[Woochifer]

Wow, that's quite a response curve you got there! Have you also corrected the readings to compensate for the SPL meter mic's inaccuracies? Here's a couple of links that give you the correction values for the Radio Shack SPL meter.

http://www.svsubwoofers.com/faq_rscomp.htm
http://www.audioc.com/library1/testcd/testcd.htm

For your setup, Terrence is right in that repositioning is probably where you should start. The rule of thumb that's worked for me is to setup the subwoofer at the seating position and play a test tone (or even music) through it. Go low to the ground and crawl around the room until you locate the spot where the bass seems fullest and most even. Once you reposition it, then remeasure it, and do the necessary corrections with the BFD. Extremes as big as the ones in your room are very common. The BFD will help with the peaks, but it won't do much for the cancellations, so try to find a location for the sub that minimizes the dips.

[cam]

Thanks for your responses. I guess I can't brag to anyone about how my sub is +/- 27 db from 23hz up to 85hz. What a joke. This 27db swing was really bugging me all day and then I got to thinking, when I was using my test tones I forgot to turn off my mains. Paradigm states that my monitor 7's are +/- 2 db down to 47hz. So somewhere around 47hz or even lower maybe I had my test tones outputing from my sub and my mains. Probably was getting some bass cancellations at certain frequencies. I will redo my results and Wooch thanks for the links for the compensations for my spl, I did not take that into consideration with my first test. I will post my new results tonight with my sub in the same location and if they still suck I will have to move my 69 lbs monter around.

[Woochifer]

Thanks for your responses. I guess I can't brag to anyone about how my sub is +/- 27 db from 23hz up to 85hz. What a joke. This 27db swing was really bugging me all day and then I got to thinking, when I was using my test tones I forgot to turn off my mains. Paradigm states that my monitor 7's are +/- 2 db down to 47hz. So somewhere around 47hz or even lower maybe I had my test tones outputing from my sub and my mains. Probably was getting some bass cancellations at certain frequencies. I will redo my results and Wooch thanks for the links for the compensations for my spl, I did not take that into consideration with my first test. I will post my new results tonight with my sub in the same location and if they still suck I will have to move my 69 lbs monter around.

Are you running the mains at full range? With a subwoofer, you should use the crossover to cut off the mains at roughly either 60 or 80 Hz. The mains should not have a huge effect except right around the crossover point.

If you were running the mains at full range, then the dip might actually come from the main speakers, since they are just as susceptible to room effects as the subwoofer.

[kexodusc]

Yikes, I did more measurements I have 2 peaks about +12 to +14 dB and couple of dips about -6 dB...I'm running out of placement options, but I'll try a few more, maybe closer to the front wall or in a corner or something.

Just curious, will the BFD help at all with nodes? Or do I have a good reason to build a second sub now? :)

[cam]

Are you running the mains at full range? With a subwoofer, you should use the crossover to cut off the mains at roughly either 60 or 80 Hz. The mains should not have a huge effect except right around the crossover point.

If you were running the mains at full range, then the dip might actually come from the main speakers, since they are just as susceptible to room effects as the subwoofer.
I did it all over again. I had my response on fast the first time so I changed to slow. I added all the compensation factors for my spl and guess what I got from 23 hz- 85 hz. Drumm roll please +/- 27 fricken db's. The same as before. The first time I had my mains at full range the second time with them off. From 23hz to 50hz I am +/- 7 db, If I bump it to 20 hz I am still only +/- 8db. My problem is from 51hz to 80hz +/- 20 db's. The biggest dip I have is between 56 hz and 60 hz and if I was to remove those numbers I would be +/- 10 db's. My average db's between 23 and 50hz is 92 db's to 99 dbs. Between 51 and 80hz I get a low of 72dbs and a high of 92 dbs. If I remove 51 hz which is 92db's and the 56hz to 60 range which runs from 72dbs to 79 dbs I can then get an average range between 80 dbs and 90 dbs. Much less then the 92 to 99 db range I was getting between 23 and 50hz. I guess this weekend I will have to try a different location for my sub and then do it all over again. Sigh!

[Woochifer]

Yikes, I did more measurements I have 2 peaks about +12 to +14 dB and couple of dips about -6 dB...I'm running out of placement options, but I'll try a few more, maybe closer to the front wall or in a corner or something.

Just curious, will the BFD help at all with nodes? Or do I have a good reason to build a second sub now? :)

The BFD is great for dialing down the peaks, but won't help with the dips. Believe me, just eliminating the peaks makes a huge improvement in your overall system performance. Like toenail indicated on another thread, evening out the bass has benefits that extend beyond just the low frequencies.

Placement is the first thing to try, and once you've got a better location picked out, then use the BFD to take care of any remaining problems.

Yet, something tells me that you won't need a reason to build the second sub. :D

[cam]

Yikes, I did more measurements I have 2 peaks about +12 to +14 dB and couple of dips about -6 dB...I'm running out of placement options, but I'll try a few more, maybe closer to the front wall or in a corner or something.

Just curious, will the BFD help at all with nodes? Or do I have a good reason to build a second sub now? :)
Hey Kex, I'm thinking about packing it in and just locating my sub right at my listening spot. I will just throw a pillow on it and build a backrest to it and Bob's your uncle. What do you think?

[kexodusc]

Yet, something tells me that you won't need a reason to build the second sub. :D

I don't think you get it Wooch...I got a new table saw and plunge router for christmas, and I have 6 sheets of 4' X 8' 3/4" MDF sitting in my garage waiting for me to chew up I got at a closeout sale. I'm not building the first sub because I "need" it...just something to do. :D

So, looks like I'll have to rearrange some of the furniture along the perimeter of my room to locate some better position options. Mind you -6 dB ain't that bad for a dip...the peaks are annoying, and the range of +4 dB's or more is quite long in some of them... more than 8 Hz... I've got a few minor peaks too, +5 or + 6 dB in the 40's and 60's I think(recalling from memory)...I still have no doubt the BFD is gonna do wonders.

So, alternative placement is really the only option for a room node, then? Am I correct in assuming that moving the sub just moves the node somewhere else in the room?

[kexodusc]

Hey Kex, I'm thinking about packing it in and just locating my sub right at my listening spot. I will just throw a pillow on it and build a backrest to it and Bob's your uncle. What do you think?

Cam...try this...go to the local hardware store, buy some dry-wall anchors or plant hangers and hang the sub off the ceiling...maybe buy a nice vine or something to make it look cozy...

Let's be fair though Cam...you're not really +/- 27 dB...you're total deviation from peak to dip is 27 dB, right? A BFD will still make it sound 50% better, I'm thinking...Lots of DIY-ers make end-tables out of their subwoofers for a variety of reasons...maybe you could whip something up.

What an eye opener, eh?

[toenail]

I just wanted to chime in and add my .02. I've had me BFD for 3 days now and can't say enough about it's ability to tame sub curves. I've not tried to raise any of the serious dips, but have leveled off all the serious peaks. Despite the fact that I only had limited time to work with it initially and response is far from ruler flat the improvement in sound quality cannot be overstated. I can't wait to see what happens given more time and fine tuning. For $100 you can make no larger improvement in the audio chain.

[swgiust]

If you can find an Infinity RABOS test kit, use it.
This is probably one of the best Sub test kit's available.
It has a test disc and a sound level meter that is set
up just for bass. Way more acurate than a Radio Shack
meter.

[Sir Terrence the Terrible]

If you can find an Infinity RABOS test kit, use it.
This is probably one of the best Sub test kit's available.
It has a test disc and a sound level meter that is set
up just for bass. Way more acurate than a Radio Shack
meter.

I am not aware that they sell RABOS seperately from the infinity sub system. Besides they would probably sell it at a premium, making it more expensive than just buying a RS meter, get the correction values off the net as well as the bass test disk. Besides there is nothing in that test kit has that sets it head and shoulders above what is already out there.

[kexodusc]

The Rat Shack meter with compensation values is actually pretty darn close. I've compared my old Rat Shack meter to my Erikson and Galaxy Audio SPL meters...the differences are +/- 1 to 1.5, but that's rarely, most of the time they're the same or closer.
I think a test such as the Infinity unit mentioned above are also helpful, but for those who already have SPL meters, no need to buy another.

[swgiust]

You can buy the RABOS kit for $ 79.00 direct from Infinity, but I have
seen them on e-bay for much less. Many sub reviewers in the magazines
use this system (even when not testing an infinity sub). Iv'e had mine for
about 4 years and have used it in many other friends set-ups. It may
not be the end all, but it sure is the most acurate sub set up system
I have used.