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Sonnie in your set up manual you suggest adding a house curve to the response. I wonder how much of a boost to the bottom end do you suggest in relation to the top end? i.e. how many dB's higher is 20 Hz then 80 Hz?
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Andrew,
Typically you would level off from 20hz to about 35-40hz then gradually drop about 8-10db from 40hz to 80hz. But this is not a chiseled in stone approach. Just from many I've seen this seems to be a popular trend. Probably the second most common house curves I've seen start at about 25hz and slope 10-12db to 80hz. Some I've seen even boost the 30-35hz range a few dbs before sloping. I suppose it might depend on how much umph you really want or need. I've also read where some didn't seem to like to house curve at all and like the ruler flat better, especially for music.
Now, I believe it is Wayne P. or Ken Bruce that can take your room dimensions and calculate a more precise and proper house curve.
My settings were based on trial and error. I tried several different settings and switched between them watching the same 30 minute segment of U-571. I set up my relatively flat curve and 3 different house curves. I used presets 4, 5, 6, and 7 with the 4 different curves. I watched that segment 6 times on one day. Not my idea of a fun 3 hour time slot of trying to be focused on listening, but I could definitely tell a difference between the flat and house. The more difficult part for me was telling the difference between the house curves, not so easy for me.
It just so happens that I had a null around 50hz or so and it worked out good for the slope to start at about 40hz and pass through that null. I've got one of those weird looking house curves. I think the null was a little misleading in that my ears were not hearing it as much as my SPL meter was reading it. I could get rid of the null and really do a good job of making the line look good but it didn't sound right...so, I left it as was and it sounds good and right.
SONNIE
Cedar Creek Cinema
DVD Collection
BFD Comprehensive Setup Guide -
Alright BFD experts I need some guideance. I have a huge hole at 31 hz that I can't seem to fix with what limited sub positions I have. I've tried moving the subs around a little but other then a few dB's here and there its always still there.
This is a plot of the subs to give you some idea of what I'm facing. (both sub's 80 hz XO)
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Got an eraser? :LOL:
Man, I feel so bad, I haven't even played with my BFD, just no time for it.
LexDoug
"I'm out there Jerry, and I'm loving every minute of it!" - KramerComment
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Andrew, I think Lex has a good idea.....use the eraser! Nah!
I'm assuming this is pre BFD. No adjustments made.
I'm assuming you are using the Tempest subs.... what about the one in the side wall?
It would be nice and probably eliminate some of that dip if you could get them shoved up into the corner. You've got a pretty solid room with no openings so you shouldn't have much escaping out. This makes me think you may have some standing waves in that area. Just a thought, especially if you are using the side wall sub too.
That dip is not nearly as wicked as mine was. I would think you could get most if not all of this worked out.
Assuming again, you can't or don't want to move the Tempest subs, I would start out trying to bring down the peak 20-22hz. I believe in using the trial and error method. Try 21hz with a bandwidth of 4, then 6 (maybe even 8, but 8 may get into cutting your frequency below 20hz even more).... cut about 4db (maybe 5db)....remeasure each time and see what kind of response you get.
A small bandwidth (2 or 4 as you don't want this too wide because it will further your problems at 32hz) cut of 2-3db at 45hz should flatten out that small peak and again a 1-2db cut (2 or 4 bw) at 56hz. Remember to remeasure after each adjustment to see what has happened and make necessary changes before proceeding problem area.
You will have started a house curve except for the huge dip.
That dip looks like a huge problem, especially if it ends up being a null. Anyway, go ahead and try to boost it up. First I'd try 32hz or 34hz with bw at 6 or 8 and boost gain about 8db. See if it works. Also check a good movie scene and see if your sub amp seems like it's straining and see if it sounds right.
You may can try 2 filters, one very narrow bw of 2 at 31hz with a boost of 6 or 7db, and another bw of 6, 8, or even 10 at 36hz with a boost of 5 or 6db. The higher the bw the more overlap you will get with the other filter at 31hz, which may or may not help. Also the wider bw used could cause too much of an overlap and cause too much of a boost in that 30hz to 32hz range.
If you can't boost that dip area to any success you might try cutting a larger bw area of say 10 or 12 at around 22hz or 23hz with a cut of say 7db. Then try working on the area right of the dip at say 36hz to 40hz to at least narrow up the dip where it may not be as noticeable.
As you enter filters you might have to go back and add more filters around those filters with minute bw's to level off that area a little flatter.
It is normal for this to be a lot of trial and error setting and experimenting. Taking numerous measurements is sometimes painstaking but necessary. This is why some use Spectra Plus or ETF software to speed up the process. Another steep learning curve IMO.
Keep in mind though, sometimes there's just nothing you can do about those dips. You might can adjust them a little but not always perfectly. As I'm sure you already know the bottom line is how it sounds to you.
And +/- 3db or so is not a bad line IMO. You are not too terribly far from this.
SONNIE
Cedar Creek Cinema
DVD Collection
BFD Comprehensive Setup GuideComment
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I tried adding two filters the other day to boost the two dips (32,80) and had some progress. The 32 hz dip didn't respond that well but the one at 80 came up more easily. I am not using the inwall sub anymore it got replaced with the two subs shown on my website. I have tried moving them around to have the drivers facing the corner of the room but it didn't change the hole at 32 that much so I'm not sure what I can do to fix that null. I also thought about running just one sub to see if it was an interaction between the two subs but other then over all SPL been lower the plot looked very similar to the one above.
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When you faced the subs into the corner did you have them as close as a few inches (say 1-2 inches) from the corners? And then try measuring.
It's just surprising with your room that you would have that kind of null.
I know the ultimate measuring location is your sweet spot too but have you move around in a few other sitting spots to see what that area around 32hz measured?
SONNIE
Cedar Creek Cinema
DVD Collection
BFD Comprehensive Setup GuideComment
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Sonnie I moved one so that it was a few inches from the side wall and about 10" from the back corner. I only tested one sub though since they are very heavy and hard to move around. I'll try and do some more testing this weekend...
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Andrew,
I was going to suggest using a single sub and see if the second was causing cancellation, but I see you’re already tried that. That is a really big null, as Sonnie noted. I’m going to hazard a guess that your length and width dimensions are similar? That would probably explain it.
You’ve mentioned moving the subs around a little – have you tried the corner? Running a single sub corner-loaded would let us know if your null is placement or room induced.
Also, in your situation I suggest getting head start on a house curve. As Sonnie noted, you have something of a built-in curve, so knowing the curve you need will help recommend suitable filters, either to EQ with the curve in mind, or EQ for flat response and add the curve after-the-fact.
To calculate your house curve, put the meter aside and play test tones at 100Hz and 28Hz. They should subjectively sound like they are at the same volume. Once you achieve this, take separate SPL readings. The difference between the two (typically between 6-15dB) is the curve we will shoot for i.e., a slope of xxdB from 100Hz to 28Hz. (Normally I use 32Hz as the reference point, but obviously we can’t in your case.)
Once you get a chance to put in Sonnie’s filter recommendations, perhaps you can put up another graph so we can see how things are going.
Regards,
Wayne A. Pflughaupt
My Equipment ListComment
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Hey Andrew, when you gonna show your new graph? I know you been working on it.
SONNIE
Cedar Creek Cinema
DVD Collection
BFD Comprehensive Setup GuideComment
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opps I'd forgotten about that
ops:
Wayne
"I’m going to hazard a guess that your length and width dimensions are similar? "
Room is 12' wide by 23' long by 7' high so while not a square the room lenght is a function of the width...
Here's the current plot...still needs little work but its sounding MUCH better.
Before
After
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Wow, that dip is gone. Looks pretty good.
I'd probably throw some more filters in (maybe one wide one) past 80hz to get that area lower.
So, how does it sound?
SONNIE
Cedar Creek Cinema
DVD Collection
BFD Comprehensive Setup GuideComment
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Its a night and day difference. Remember I said I wasn't quite finished with it? Well that dip at 80 is the one thing I have left to tweak since that's the crossover point to the M8a's
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That's great Andrew!
Amazing what a $130 piece of equipment in the chain can do.
Another BFD success story.
SONNIE
Cedar Creek Cinema
DVD Collection
BFD Comprehensive Setup GuideComment
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