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Help with BFD initial settings - Attn: Wayne A. Pflughaupt and others (1 Viewer)

WarnerL

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I have a single SVS PCi 20-39 subwoofer and a Yamaha receiver (fixed crossover at 90 Hz). Using the radio shack SPL meter and sine wave test tones I came up with the following readings:

and the resulting graph:

My home theater room is Length= 26.5 ft, Width= 11.0 ft, and Height= 8.67 ft (i.e. 2527 cubic ft). The subwoofer is sitting in the right front corner along the shorter wall. There is a 12 ft opening at the back left corner along the length and another 3.3 ft opening at the back left corner along the width. The seating position is 17.5 ft back from the front wall.
I have a BFD 1124p on backorder at a store so I have not received it yet but hope to get it some time next week. I was hoping that Wayne A. Pflughaupt and/or other experts could give me some suggested settings/adjustments for the BFD in advance to give me a starting point to work with and also a suggestion for the amount of house curve recommended.
Thanks all for any help,
Warner Lee
 

Wayne A. Pflughaupt

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This is pretty rough response, Warner. I suggest moving the sub to the other front corner and post some new readings. We’ll proceed from whatever position gives us the best unequalized response.

Regards,
Wayne A. Pflughaupt
 

WarnerL

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Hi again, Wayne,
Thanks very much for your offer to help. I moved the subwoofer to the front left corner as you suggested and here are the readings:

with the resultant graph:

It looks to me that this might be a better location to start. Do you agree?
I haven't got the BFD as of yet (it is still on back-order) but I still plan to purchase it when it comes in (hopefully by this Friday). I have read your previous posts to others when you helped them with their initial equalizer settings and I understand how to input them into the BFD so what initial settings would you suggest? Also, again, what kind of house curve based on my room size as posted previously or am I getting ahead of myself?
Thanks again,
Warner
 

Geoff L

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Being that you have the time while you wait for your BFD I'd keep experimenting with placement.

Is one graph better than the other?

Well this depends on what ou looking for...?
Do you want a flat or as flat as possible freq response, or a house curve...?

With a small to med House Curve, (my preferance) due to our hearing lose in the lower freqs, Greaph 2 would be better.
At this point!

But moving the sub while in that position as little as a foot one way or the other (out, over to the left, over to the right, etc) can change the responce.

As I said above, I would continue to experiment with that and or other locations, if you have them, to see what you can come up with. Remeber, you can boost a null till your blue in the face and just suck amp power and make little or (NO gain usually). Cutting freqs is your best bet, pulling them into line with the curve you would prefer.

You might do a search for ~{house curve eqing}~ to get more information on this.
It's been discussed allot.

Nice easy to read graphs by the way....

Cheers
Geoff
 

Wayne A. Pflughaupt

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Warner,
Both these curves are difficult. I experimented with both, and the second gets a better “finished product,” albeit with an extra filter. So I’d go with the second placement.
Geoff is correct that you can’t effectively boost a null. However, not all under-represented areas of a response curve are nulls.
The following filters should give you very flat response. However, the result will be that the sub’s output will be fairly low after equalization, so you will have to boost the gain to compensate (say goodbye to the “free” headroom!). If there are any nulls, they will re-appear when you boost the gain, but it’s nothing to worry about. As Geoff noted, you can’t do anything about them anyway.
  • 1/3-octave, centered on 20Hz, cut 20dB.
  • 1/6-octave, centered on 40Hz, cut 12dB.
  • 1/6-octave, centered on 50Hz,cut 13dB.
  • 1/2-octave, centered on 60Hz, cut 6dB
  • 1/6-octave, centered on 70Hz, cut 14dB.
I’ve tried to allow for “drag up” at the fringes of the filters with these recommendations (“Drag up” is when the filter affects a wider area than its set bandwidth. It’s more of a problem with extreme gain adjustments, as we have with most of your filters.) So you should end up with very flat response. If you find “bumps” or “dips” in response, they will be centered between the filters. If this is the case, try fine-tuning (widening or narrowing) the filter’s bandwidth instead of applying more filters.
As noted, response after equalization will be very flat, so you will have to get your house curve by overlaying another filter. The nice thing about this is that you can dial in a very precise curve. When you get to this point, let me know and I’ll give further instructions.
Regards,
Wayne A. Pflughaupt
 

WarnerL

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All right,
I got the BFD today for $229 CDN + tax. Hooked it up, and tried the filters and settings suggested by Wayne starting with the 20 Hz filter. After applying the first filter I retook the SPL readings and regraphed everything and then tweaked it and regraphed until I got it to what I wanted. I then moved on to the next filter, new SPL readings, new graph, tweaked it, and so on and so on until all five filters were applied.
Here are my before and after readings:

and the graph:

My 5 filters ended up to be:
20 Hz, 17/60 octave, cut -20dB
40 Hz, 4/60 octave, cut -7dB
50 Hz, 7/60 octave, cut -8dB
60 Hz, 7/60 octave, cut -6dB
70 Hz, 4/60 octave, cut -11dB
Wayne, the biggest change I made from your initial suggestions was with the 60 Hz filter. As I was going along, after the 20, 40, and 50 Hz filter was applied and I looked at the graph, a 1/2-octave 60 Hz filter would have been too wide so I shrunk it down to below a 1/6-octave bandwidth.
Anyway, now I'll move on to making a house curve but that will have to be another day (probably tomorrow).
Thanks again, Wayne
Warner
 

Wayne A. Pflughaupt

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Hi Warner,

Your curve ended up very much like I expected, expect for the slight rise between 50-56Hz and at 22Hz. I’m glad to see you took my advice only as starting points and tweaked from there to get the best curve. For instance, I notice the filters you used are a bit narrower than I recommended – no doubt to the “drag up” situation I mentioned. It’s hard to predict precisely, and indeed it appears it was worse than I anticipated.

I am puzzled by the 20Hz filter, which was cut 20dB yet shows up as almost 23dB of gain reduction. Makes me wonder how accurate the settings on the BFD actually are.

If you want to flatten things a little more before applying a house curve, try a filter a little tighter than 1/3-octave at about 53Hz, cut 2-3dB. Keep an eye on the fringe readings at 45hz and 63Hz. Adjust the filter so that those frequencies result in no change.

Another filter a little under 1/6-octave at 22Hz cut about 5dB will take care of that bump. Again, watch the readings at 20Hz and 25Hz. We don't want them to change.

The 22Hz filter is the most important of these two additions. If left the way it is now, it could give us some unwanted rumble after the house curve is applied.

Post the results, then we’ll move on to the house curve.

Regards,
Wayne A. Pflughaupt
 

WarnerL

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Hello again, Wayne,
OK, this is what I did now: I bumped up the overall level of the subwoofer using AVIA as a guide to where I had it before (about 2-3 dB above the mains) and took new readings and made a new graph with my previous 5 filters still intact. I then took your suggestions along with looking at my graph and altered slightly a couple of the original 5 filters and added 3 more.
Now my filters are:
20 Hz, 17/60-octave, cut -20dB
22 Hz, 3/60-octave, cut -5dB
40 Hz, 4/60-octave, cut -9dB
50 Hz, 7/60-octave, cut -8dB
53 Hz, 6/60-octave, cut -4dB
60 Hz, 7/60-octave, cut -6dB
70 Hz, 3/60-octave, cut -14dB
88 Hz, 5/60-octave, cut -3dB
which resulted in the readings:

and the graph:

Now Wayne, I tried fooling around with another filter in order to form a house curve that only affected from 31.5 Hz and higher but I couldn't seem to do it properly yet. I am having difficulty getting the slope to start at the 31.5 Hz point and also getting the 100 Hz point down sufficiently. Could you go over the method with the BFD as you know it again?
Warner
Update: Wayne,
I've been trying to create a house curve using the BFD according to Ken Bruce's instructions that I found and I think I am in trouble. I am following his instructions in using the BFD design software and inputting my existing filters and trying to find the additional filter that will impart the house curve from 32 Hz to 100 Hz, but I think that because I have so much cut in all the previous filters, I cannot find a suitable filter/bandwidth/cut that will create a house curve. Help please if you can. I guess it would be possible to have a certain house curve in mind and start from scratch with all my filters and try to create a house curve that way, but that seems like a lot of work and I spent so much time on getting it flat now. Again, help if you can.
Warner
 

Wayne A. Pflughaupt

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Warner,
Are you following the instructions Ken noted at this link?
If not, I need to know exactly what you’re doing – center frequency, bandwidth, amount of boost or cut.
Regards,
Wayne A. Pflughaupt
 

WarnerL

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Wayne,
I was following the instructions at the link you gave.
I initially tried the same settings he did, that is:
366 Hz, 120/60, -15dB
There was no change in the graph.
Then:
366 Hz, 120/60, -23dB
with absolutely no change in the graph.
Then I tried:
366 Hz, 120/60, -40dB
and got this:

There is barely any change at all and I am getting to the limit of the cut that the BFD can do (-48dB is the limit I believe). Do you think it is because of the huge cuts in all my previous filters that it is not possible to create the house curve using this Ken Bruce method?
Do you think I would be able to get a house curve by having a filter raise up the 32 Hz area?
Do you think I would have to start from scratch and use the initial filters with a house curve in mind?
I know I am setting the filters properly. Not sure what to do now?
Warner
 

Wayne A. Pflughaupt

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Warner,
This is peculiar indeed. You may well be right that it has to do with the fact that we have applied reduction filters to such a wide frequency range. It may be that the DA converter is no longer getting enough signal to function. Ken would be a better source for what’s happening here – he’s more familiar with the workings of digital equipment than I am.
I agree that the thing to do at this point (before calling in Ken and his brain trust  ) is to apply a boosting filter to get our house curve. However, 32Hz would not be a good turn-over frequency. The idea is to shelve at that point. It will take a wide filter to do this, so it will have to have a lower frequency setting, so that response starts to fall at about 30Hz.
I’d say start with a 2-octave filter centered on 20Hz and boost as needed. That should start to roll down around 32Hz and end around 100Hz. If you need the curve to end at a lower frequency (some people like to begin their curve at 80Hz), tighten up the filter.
Rough guidelines for boost:
6dB for a total room volume of 7000 cubic ft.
9-12dB for a room 6000 cubic ft.
etc.
Here are a few links to help you determine how to get a good house curve.
http://www.hometheaterforum.com/htfo...918#post499918
http://www.hometheaterforum.com/htfo...014#post530014
http://www.hometheaterforum.com/htfo...958#post464958
Regards,
Wayne A. Pflughaupt
 

WarnerL

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OK, Wayne,
This is what I have been doing. First off, I decided to further tweak my flat response. The filters I used include your original suggested 5, your next suggested 2, and a couple more that I added myself:
20 Hz, 17/60-octave, cut -20dB
22 Hz, 3/60-octave, cut -5dB
25 Hz, 3/60-octave, boost +2
40 Hz, 3/60-octave, cut -9dB
50 Hz, 7/60-octave, cut -8dB
53 Hz, 6/60-octave, cut -4dB
60 Hz, 7/60-octave, cut -6dB
70 Hz, 3/60-octave, cut -15dB
88 Hz, 5/60-octave, cut -2dB
This gives the readings:

and the graph:

I tried to get rid of the 16-18 Hz peak but I was not able to no matter what I tried, but I am still happy with the resulting flat response that I achieved.
Now, the house curve was another problem as the Ken Bruce method did not work for me as I mentioned before. I tried your suggestion with a 20 Hz boost to create the house curve but when I did that, the 16-18 Hz also shot way up (understandable since it was already a peak there) and the 20 Hz was also above the 31.5 Hz which I didn't want. It resulted in house curve that went up from 100 Hz all the way to 16 Hz and I wanted it to be flat from 16 to 31.5 Hz.
I had to decide whether I wanted to start from my before-BFD curve and work toward a particular house curve or use my existing flat curve which I had worked so hard to get thus far. I decided to try to work with what I had. For the amount of house curve, I decided on 11 dB for now. I listened back and forth to the 100 Hz tone and the 31.5 Hz tone and decided that an 11 dB difference sounded like equal loudness. My main boosting filter that I used to try and create the house curve was a boost at 31.5 Hz. From further SPL readings and graphs, I altered my 22 Hz filter slightly, and then added 3 more filters for a total of all 12 filters that the BFD can use.
My final filters (with the changes and additions from my flat curve filters bolded are:
20 Hz, 17/60-octave, cut -20dB
20 Hz, 2/60-octave, boost +4dB
22 Hz, 3/60-octave, cut -4dB
25 Hz, 3/60-octave, boost +2dB
31.5 Hz, 45/60-octave, boost +11dB
39.2 Hz, 2/60-octave, cut -3dB
40 Hz, 3/60-octave, cut -9dB
50 Hz, 7/60-octave, cut -8dB
53 Hz, 6/60-octave, cut -4dB
60 Hz, 7/60-octave, cut -6dB
70 Hz, 3/60-octave, cut -15dB
88 Hz, 5/60-octave, cut -2dB
This gives the readings:

and the graph:

The good thing now is that the peak from 16-18 Hz is now gone.
Now how does it sound? The funny thing is I don't even know yet. I did all this tweaking late last night while the baby was asleep so I can't test it out quite yet. It is now the next morning and the wife and baby are still asleep so I'll have to wait until later to listen to actual movies and music. I think that if I have to adjust the amount of house curve later that I should be able to by moving the 31.5 Hz filter up or down as needed and fine tuning the other filters after. Now with the BFD I would be only able to boost the 31.5 Hz filter a maximum of +16 dB so hopefully I won't have to get to that limit.
I know I used a lot of filters (all 12 of them) and that I might be able to get a similar house curve with fewer filters if I started from scratch but it was just so much work from before and I don't know if I have the will to do it all over again. What are your thoughts on this?
Anyway, thanks again for your help and I'll post opinions of how it actually sounds when I get a chance to listen.
Any other suggestions/criticisms, feel free to post them.
Warner
 

Wayne A. Pflughaupt

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Werner,

Yeah, I knew the 16Hz area would be a problem, since the BFD’s lowest set frequency is 20Hz.

Your new flat curve certainly looks better, but I doubt you would be able to hear a difference between it and the curve from your Nov. 21nd post. That’s why I didn’t attempt to flatten it further

Looks like I made a bad call with the 20Hz filter. Looking again at your Nov. 21st curve, a 1-octave filter at 25Hz would have probably worked better for the lower end (below 40Hz) response, but not the upper end. That still would have been a problem, based on your experiences using further cuts. Your experiences with the house curve filter should certainly give the “cut everything in site and boost nowhere” proponents something to think about!

The 11dB differential between 100 and 31Hz is probably a good indication of where to begin for your house curve. Let us know how that sounds. If I’d had an indication going in of the house curve you needed, I would have recommended totally different filters. For instance, “filling up” the hole between 22 and 45Hz would have eliminated the 16Hz hump, and a second filter set to cut at 45Hz would have gone along way towards achieving a 32Hz plateau. After that, probably a couple more filters at 63Hz and 88Hz would have put you in the ballpark for better response with a house curve built in.

If you’re not happy with the way it sounds now, I recommend we take that tact next. You can always save your current settings to memory and compare the two.

By the way, it looks like 111Hz is the only null you have – that depression has stayed fairly constant throughout, both in amplitude and bandwidth.

Regards,
Wayne A. Pflughaupt
 

WarnerL

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Wayne,

I listened to some movies and music. I'm still not sure. When you have a proper house curve, if you set the level of the subwoofer to be equal to the mains using AVIA, should the level of bass sound adequate. I found it didn't so I then set the level of the subwoofer to be 3dB above the mains which I always did before when I didn't have the BFD and it sounded better for movies. For music, 1-2 dB above the mains sounds good.

If I increased the house curve, would it sound like adequate bass if I set the subwoofer and mains levels equal according to AVIA. How is the subwoofer/mains level set up with yours? I also find that what is adequate for movies is too much bass for music. If I set out to make an increased house curve and it sounded good with movies then I have a feeling that music would sound too bass heavy. Maybe I would need a separate smaller house curve for music. But again, if I just boost the level of the subwoofer above the mains like described above then it sounds good so I'm still not sure how much of a house curve I am supposed to have.

I went back and listened to the 100 Hz tone and the 31.5 Hz tone again, and now I'm not really sure if the 11dB difference makes the tones sound the same loudness. When the 31.5 Hz tone plays, there are some parts/objects in the room that are vibrating and that makes it a bit confusing to tell whether the sounds are equal loudness.

I think I might want to try again, with your help, using the November 20th initial before-BFD curve (you were mentioning the Nov. 21st curve but I think you meant the 20th as it has the before-eq curve) and build in a house curve from the start. Not exactly sure how much of a curve this time. Maybe 14-15 dB. This might depend on your answer to my question about the sub/mains level relative to each other. I know I do have a big null at 111 Hz as can be seen on the graphs, but I also think I have a smaller null (if this is possible) at 45 Hz because in the course of trying to set up the house curve, at one point I had this valley at 45 Hz but when I tried to boost the 45 Hz, it didn't seem to budge.

Anyway, at this point what filters would you start with using the Nov. 20th unequalized curve to start?

Warner
 

Wayne A. Pflughaupt

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Warner,

I think I might want to try again, with your help, using the November 20th initial before-BFD curve and build in a house curve from the start. Not exactly sure how much of a curve this time. Maybe 14-15 dB. This might depend on your answer to my question about the sub/mains level relative to each other. At this point what filters would you start with using the Nov. 20th unequalized curve to start?
First we need to establish just how much house curve you need. The filter settings will be tailored to smooth response and achieve the curve at the same time, so you have to know the curve going in. See if you can eliminate the rattling objects and decide what dB figure gives the same perceived volume at both 32Hz and 100Hz.

Regards,
Wayne A. Pflughaupt
 

WarnerL

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Hello Wayne,
I have been working on my new house curve on my own. I decided on a 14-15 dB house curve from 100 Hz down to 32 Hz. Starting with the November 20th posted unequalized graphed response, I brought down all the peaks to the level that I wanted. I was then left with a bunch of valleys that I brought up to where I wanted and then any other filters to smooth things out.
I ended up using 11 filters. It seemed like a lot but like I said, once I brought down the various peaks, it left all these valleys which I had to smooth out plus any other peaks which showed up.
The filters used were:
20 Hz, 10/60-octave, cut -10 dB
32 Hz, 5/60-octave, boost +8 dB
40 Hz, 6/60-octave, cut -5 dB
50 Hz, 4/60-octave, cut -6 dB
70 Hz, 2/60-octave, cut -19 dB
59 Hz, 5/60-octave, cut -7 dB
88 Hz, 2/60-octave, cut -4 dB
22 Hz, 2/60-octave, cut -4 dB
45 Hz, 2/60-octave, boost +6 dB
35.8 Hz, 2/60-octave, boost +6 dB
26.3 Hz, 6/60-octave, boost +6 dB
This gave the SPL readings:

and the graph:

I adjusted my subwoofer level about 3dB above my mains according to AVIA. I haven't listened to a wide range of movies yet but I love how it sounds so far.
Any comments, Wayne?
Thanks again for all your help. I hope I did things correctly.
Warner
 

Wayne A. Pflughaupt

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It’s virtually a picture-perfect curve, Warner – I’m impressed with how you’ve mastered both the BFD and finer points of parametric equalization. If you’ve dialed in the right house curve (and it sounds like you got that down, too) I’m sure you’ll be very happy with the way it sounds.

I do recommend using music for your critical listening, however. Your curve should sound very flat and natural, with the lowest and upper bass notes at equal volume.

After you’ve had some evaluation time, get back to us here and let us know what you think.

Regards,
Wayne A. Pflughaupt
 

WarnerL

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Aarrrggghh!
I was listening to some music, then some sine wave test tones and sweeps, and something didn't seem right. I decided to regraph my current frequency response. This time I took SPL readings with the subwoofer and front mains and this was the result:

Where did that giant hole at 63 Hz come from? The graphed response was also very bumpy as you can see. Also my nice 15 dB house curve was wrecked. Now at first I thought it might have something to do with the interaction with the mains especially around the crossover area (90 Hz) which might reduce the slope of the house curve but I didn't think it would have caused the 63 Hz dip nor that "wiggle" from 36-56 Hz.
Now the things I had changed in my set-up since my last graph on Nov. 27/02 which might have caused this change was an alteration in my receiver's subwoofer level and the subwoofers own level control. During the viewing of a few DVDs, I noticed the red clipping lights coming on quite strong on my BFD on some heavy bass sections of the movie. This indicated that the input level into the BFD was too strong. I retested the input levels into the BFD and changed my receiver's sub out setting from -4 to -8. I then recalibrated with AVIA (again setting the sub 3dB above the mains which is how like it) which meant the subwoofers own level control had to be boosted since I had reduced the receiver's sub out level. These are the only changes which I think could have caused this drastic change in response.
I decided to start from scratch again and redo the EQ and house curve again. This time I decided to take SPL readings with the sub and front mains both on since I figured this is how I actually listen to things.
I ended up using 11 filters and was aiming for a 12-13 dB house curve. The results were:


I then wanted to see what happened when I reduced the receiver's sub out level by 3dB since this is what I usually have to do when listening to music as opposed to DVD movies. I wanted to see if the reduction in the receiver's sub out level was responsible for the drastic change in response from before and whether the results would be just as drastic again. So with the receiver's sub out level changed from -8 to -11 (the setting I use to listen to music), I then took new readings. When taking the readings, I also adjusted the overall master receiver volume so the starting (16 Hz) subwoofer tones were about the same as my previous readings. Here are the results:


I noticed a little dip starting at 63 Hz again although not too severe. Also, my previous 13dB house curve was now only 12dB which was caused by a slight boost that occurred from 71 Hz to 100 Hz as can be seen in the graph. Overall the response was altered to some extent but I think still fairly close and not enough to worry about so this is how things will stay for now.
Warner
 

WarnerL

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Hello again, Wayne,

I'm not sure if you saw my last post on December 1/02 but I was wondering if you could comment on my change in graph response and my subsequent need to re-equalize my response as seen in the post mentioned above. Again, the only thing I had changed was both the subwoofer's own level control and the receivers subwoofer out level control. Also, as can be seen in my last graphs on Dec. 1/02, I started graphing the response with both the front mains and subwoofer together as I figured this is how I listen to things and if the mains were going to affect the response curve I was aiming for, then I wanted that taken into account. Is this incorrect thinking on my part and if so, why?

Thanks again for all the help. I am very happy with how things sound both with music and movies and I believe I dialed in the right amount of house curve for my room.

Warner
 

Wayne A. Pflughaupt

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Hi Warner,

I must have forgotten to respond to the December 1st post. Sorry for leaving you hanging. :b

Since you asked me to comment on that post, I’ll be happy to:

I am very happy with how things sound both with music and movies...
Excellent! That is the final goal, after all!

Regards,
Wayne A. Pflughaupt
 

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