Sub measurements with graph....suggestions?

Discussion in 'Archived Threads 2001-2004' started by Sonnie Parker, Feb 25, 2002.

  1. Sonnie Parker

    Sonnie Parker Second Unit

    Joined:
    Dec 11, 2001
    Messages:
    407
    Likes Received:
    0
    Trophy Points:
    0
    [​IMG]
    [​IMG]
    Crossover is 80hz. Results are for sub only. Mains off.
    Values are compensated with corrections. (RS SPL Meter)
    Sub is shoved up in the front corner of a 4300 cubic feet room with a large 5 foot X 9 foot opening into another room with approximately 6000 cubic feet. (I should probably install some french doors in this opening but it wouldn't pass the WAF.)
    I have already set up a couple of presets on my BFD to smooth out this response but am always open to other suggestions that I might input into another preset. Then I can switch between the presets and determine what sounds best to me. I'd like to end up with 3-4 presets total.
    I believe I would favor a house curve rather than flat. I believe this will help me when I get to the 50hz dip as well.
    I have had some strange experiences with this 50hz dip. I tried boosting it up about 8-10db and got rid of a good bit of it. But, when I was running my test tones with the boost, that 50hz tone sounded really strange, as if the amp was struggling. The tone did not sound smooth like the other tones. It sounded too loud althought the reading only increased 8-10db. I suppose the headroom was sucked up, even though I was playing only the one tone. This really doesn't make sense to me. I might would understand it if I were playing several octaves of tones but this is just 1/6 octave playing. I tried +6db and got the same. When listening I noticed the same thing, so I notched the boost back down to +3db and it sounded much better. It didn't sound like I was missing anything, but I still have a huge dip at that range. It actually made me wonder if I was getting the right reading at 50hz. But I've always measured this dip in that range, even when I ran the sweep on Spectra Plus.
    At any rate, I'm open for suggestions and am curious as to how others might set up their BFD if they had this same response and set up (obviously without the benefit of a listen).
     
  2. Wayne A. Pflughaupt

    Moderator

    Joined:
    Aug 5, 1999
    Messages:
    6,208
    Likes Received:
    56
    Trophy Points:
    9,110
    Location:
    Katy, TX
    Real Name:
    Wayne
    Sonnie,
    Sorry to take so long to get to this – those other threads are keeping me pretty busy (I know you know which ones!). [​IMG]
     
  3. Sonnie Parker

    Sonnie Parker Second Unit

    Joined:
    Dec 11, 2001
    Messages:
    407
    Likes Received:
    0
    Trophy Points:
    0
    Thanks Wayne, no big hurry, I plan on setting up a couple of filters on Wednesday (my day off).
    You have been pretty busy lately. And helpful as usual.
    I suppose I should mention that I have one wall full of windows and french doors to the outside. Probably one of the worst setups for home theater you could be faced with. It sounds respectable though. I'm mainly a movie buff so it makes it a little easier....I don't have to be so precise for music listening.
    If you have time, you can get an idea of what my room looks like here:
    Pictures
    But warning, I haven't mastered imaging on the web too well yet, nor my digital camera. I plan on having some better photos up soon. You can still get a good idea of what my room looks like though. The htpic4 will show you the large opening and htpic5 will show you part of the windows. In htpic6 you see another opening which I included in as part of the main room.
    I did reduce the subs volume but then it didn't sound loud enough on movies. The drop to +6db did have a small effect but the drop to +3db sounded better, on the test tone.
    I really probably wasn't fair on stating that when listening it sounded better because I only watched part of a movie. The tone sounded better but maybe I should watch a couple of movies to make absolutely sure.
    Any maybe I should try out some filtered pink noise tones.
     
  4. Patrick Sun

    Patrick Sun Studio Mogul

    Joined:
    Jun 30, 1999
    Messages:
    38,779
    Likes Received:
    493
    Trophy Points:
    9,110
    Room suckouts are pretty tough to fix with simply boosting those frequencies because you are fighting audio physics, and that's why the goosing that trouble spot frequency range taxes the amp because "it's giving it all she's got, captain!" but you just aren't getting the acoustical energy for the input power applied at your listening position.

    If you tried the sub in different locations (if possible), then you might fix the suckout problem, and may create some humps that are easier to fix.
     
  5. gomez_a

    gomez_a Stunt Coordinator

    Joined:
    Nov 14, 2001
    Messages:
    119
    Likes Received:
    0
    Trophy Points:
    0
    Sonnie,

    i'm trying to post my chart as well, but everything I try fails,I posted the link to my free web host site (angelfire), but the site gives a message that it doesn't allow remote linking. The site works because when I click on the link outside this forum, all the data clearly comes up.

    I tried to cut and paste into this windo and that doesnt work either - anyhelp would be appreciated :)
     
  6. Wayne A. Pflughaupt

    Moderator

    Joined:
    Aug 5, 1999
    Messages:
    6,208
    Likes Received:
    56
    Trophy Points:
    9,110
    Location:
    Katy, TX
    Real Name:
    Wayne
    Sonnie,

    I’m with Patrick: This is going to be a tough one to smooth out. Is there another corner available – preferable one with maximum uninterrupted wall length in both directions?

    If not, we’ll just do the best we can.

    Regards,

    Wayne A. Pflughaupt
     
  7. Sonnie Parker

    Sonnie Parker Second Unit

    Joined:
    Dec 11, 2001
    Messages:
    407
    Likes Received:
    0
    Trophy Points:
    0
     
  8. Sonnie Parker

    Sonnie Parker Second Unit

    Joined:
    Dec 11, 2001
    Messages:
    407
    Likes Received:
    0
    Trophy Points:
    0
    gomez....
    E-mail me your chart... are you using the excel workbook?
    If so, e-mail me your entire sub test file and I'll put it up for you here and the fellows can look at it. I'll even stick it up on a webpage for ya so you can do whatever you wish with it.
    Send it to [email protected] don't use the e-mail here because I'm about to head home....the e-mail link here is to work and I won't be back here til Thursday.
     
  9. Wayne A. Pflughaupt

    Moderator

    Joined:
    Aug 5, 1999
    Messages:
    6,208
    Likes Received:
    56
    Trophy Points:
    9,110
    Location:
    Katy, TX
    Real Name:
    Wayne
    Okay, Sonnie, I think the following adjustments will give you much (read audibly) improved results.
    Starting at the upper end, set a filter for 1/3 octave bandwidth, centered on 71Hz, and cut 6dB.
    The outer parameter of the filter will be 63Hz and 80Hz. However, it is common for a filter to “spill over”, or affect an area a little wider than it’s “supposed” to. I’m counting on this effect to make needed adjustments to 63Hz and 80Hz. If you find the BFD’s outer parameters are rigid (i.e., no change at 63Hz and 80Hz), then tweak the filter a little wider – in addition to the –6dB at 71Hz, we need a 2dB cut at 63Hz and 80Hz.
    Next let’s tackle the hump at lower end. I think a filter set for 1/2-octave, centered at 34Hz and cut 4dB will do nicely there.
    That leaves us with that pesky situation at 50Hz. As Patrick noted, room nulls can be a problem. However, room-induced nulls are usually pretty narrow, typically 1/6-octave or so. Your problem is fully an octave wide, Sonnie. In my opinion this is too wide for null. A null may be aggravating it, but I think much of the problem is the response characteristics of the sub.
    I’ve already made it know what I think of equalizers and headroom. For those who missed it, you might want to check my third post at this thread(
    http://www.hometheaterforum.com/htfo...threadid=52092), but this excerpt pretty much summarizes:
     
  10. Sonnie Parker

    Sonnie Parker Second Unit

    Joined:
    Dec 11, 2001
    Messages:
    407
    Likes Received:
    0
    Trophy Points:
    0
    This should be interesting Wayne. I wish my wife and daughter were away for awhile tonight and I'd go set it up and take a listen.
    Under-woofed.......hmmmmm! You mean I might need 2 of those expensive HGS-15's?[​IMG] Ouch! Or 3? Triple ouch! You would think at 1200 watts nominal and 3000 watts peak I'd have enough, but then again, my open area is quite large. Heck, I haven't turned the volume on the sub past 3 dots yet.
    I did read your post that you summarized above on the other thread. As a result of your commments about this I have started re-wording my BFD page somewhat. I believe instead of advising someone not to boost frequencies because they may be sacrificing headroom, I would rather explain to them what you stated. Then they can listen and hear for themselves if they like it. I think they can notice if they are pushing their amp too hard, or at least I hope they can.
    Look, if you retire on the account of me, I'm gonna send you some get well pills because you will have to be sick. lol No way I can handle this gig. That's a funny one Wayne.
    Now, it's quite possible I may like the sound from my own settings but that would be because of what I'm accustomed to hearing or because I don't know any better.
    Believe it or not, I haven't listened to many home subs in my lifetime. There are none to be found in these parts. I can't say that I have ever heard a properly setup sub in a home, so I don't really know what it is suppose to sound like. As my profile says...I live in the boondocks, always have....I am truly a country hillbilly redneck. I wear overalls and dip snuff. It's all very true. I look out my window and see cows. There are no dealers with any kind of respectable home theater stuff even remotely close to me (not that it would matter because it's not a home environment). The folks living in the counties I live and work in would pure laugh if I suggested they purchase a $2000 sub. Most folks around here go to Wal-Mart and purchase the all-in-one systems and are completely happy. They laugh at me all the way to the bank. Yeah, my friends love my HT setup and believe it sounds great, wish they had one, but ain't gonna spend the money.
    I'll let ya know how it turns out.
    Thanks for taking the time to work on this. You are most kind.
     
  11. Wayne A. Pflughaupt

    Moderator

    Joined:
    Aug 5, 1999
    Messages:
    6,208
    Likes Received:
    56
    Trophy Points:
    9,110
    Location:
    Katy, TX
    Real Name:
    Wayne
    Sonnie,
     
  12. Sonnie Parker

    Sonnie Parker Second Unit

    Joined:
    Dec 11, 2001
    Messages:
    407
    Likes Received:
    0
    Trophy Points:
    0
    Okay, Here's what I did:
    I got everything (environment,etc.) setup as I did when I made my measurements for the first graph in this thread. I realize now I had forgot to shut my bedroom door previously so I left it open. I was wondering why that dip was about 3 db lower than what it had been once before. And two of the peaks were a few db less than previously. Anyway I ran a pre-filtered measurement and actually came up with the same response. I was expecting to be off a db or so here and there, but not so.
    I input the 3 filters you suggested and took more measurements and this is what I came up with:
    [​IMG]
    [​IMG]
    [​IMG]
    There doesn't appear to be much difference in the response lines here. I thought there would be. Reckon why this is?
    Then, I shut the bedroom door and made an input level adjustment (increase from +3 to +5 on my pre/pro) and turned the volume on the sub down a tad. I felt my level had been a little low.
    I took raw pre-filtered measurements again and got a little different response. The peaks rose a db or two and the dip rose as well by about 3db. Amazing what one shut door will do. Then I made some adjustments (8 filters) and came up with this:
    [​IMG]
    [​IMG]
    [​IMG]
    I watched about the first 5-10 minutes of Swordfish (throught the first explosion of the girl and the 2 swat team fellows that get blown to pieces...ooh) as follows:
    BFD off...
    BFD set to preset 6....
    BFD set to preset 7....
    I really couldn't tell much difference between off and preset 6, but I could tell a slight difference in preset 7. It was a tad softer, the explosion didn't hit quite as hard (I'm sure attributed to the 31.5hz peak being cut). But they all sounded good. I should probably watch a few movies in each setting, but I'll probably forget from one to the next what it sounded like.
    There has to be a rhyme and reason to this.
     
  13. Wayne A. Pflughaupt

    Moderator

    Joined:
    Aug 5, 1999
    Messages:
    6,208
    Likes Received:
    56
    Trophy Points:
    9,110
    Location:
    Katy, TX
    Real Name:
    Wayne
    I didn’t use the graph - I find 5dB readings too coarse. I put the corrected readings on graph paper and adjusted the relevant, specific readings for the effect a filter would have. Makes it tough, though, when the parameters change (open vs. closed doors ), etc.
    I assume the magenta line is the EQ’d response? How does a 4dB cut at 34Hz end up as a 2dB boost...? Similar with the 71Hz filter – a 6dB cut shows up as a mere 1-2dB reduction. What’s up with that?
    At least the 45Hz filter worked as it was supposed to, closing much of the 1-octave valley.
    Nevertheless, it looks like you’ve done a great job on your own, congratulations! I’m ready to give you the gig. [​IMG]
     
  14. Sonnie Parker

    Sonnie Parker Second Unit

    Joined:
    Dec 11, 2001
    Messages:
    407
    Likes Received:
    0
    Trophy Points:
    0
    What amplitude readings would you suggest? I felt 5db increments causes the graph to look more proportional and not so crowed.

    I didn't do you wrong on the parameters, I kept them the same on that graph. Yes, I did change them for my graph but that would not effect the first one.

     
  15. Wayne A. Pflughaupt

    Moderator

    Joined:
    Aug 5, 1999
    Messages:
    6,208
    Likes Received:
    56
    Trophy Points:
    9,110
    Location:
    Katy, TX
    Real Name:
    Wayne
    Sonnie,
     
  16. Sonnie Parker

    Sonnie Parker Second Unit

    Joined:
    Dec 11, 2001
    Messages:
    407
    Likes Received:
    0
    Trophy Points:
    0
    I appreciate you taking the time to work on this with me. I believe this is really helping me understand this stuff much better. After your last post I did go back and double check to make sure I didn't accidentally input something wrong and it looked right. Of all things I hope I know how to input the settings for the filters...lol....but anyone can make an input mistake.
     
  17. Wayne A. Pflughaupt

    Moderator

    Joined:
    Aug 5, 1999
    Messages:
    6,208
    Likes Received:
    56
    Trophy Points:
    9,110
    Location:
    Katy, TX
    Real Name:
    Wayne
    Sonnie,
     
  18. Sonnie Parker

    Sonnie Parker Second Unit

    Joined:
    Dec 11, 2001
    Messages:
    407
    Likes Received:
    0
    Trophy Points:
    0
    Here's what the 10db boost would look like with the squares fairly square:
    [​IMG]
    Using the bandwidth example chart in my last post, and a Q factor vs. Octave chart, it appears this peak on this graph has a Q factor of 2.65 which translates to approximately 35/60. So you are not off much at all on the 2/3 octave (40/60). That's using the +3db points of the peak. If the peak stretchs out to 80/60 (1 1/3 octave) then the beginning and ending points at flat should be very close....wouldn't that be 30hz and 60hz?
     

Share This Page