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Behringer DSP1100P advice needed...

Discussion in 'Archived Threads 2001-2004' started by Jones_Rush, Mar 8, 2001.

  1. Jones_Rush

    Jones_Rush Stunt Coordinator

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    My sealed subwoofer project is not even finished yet, but I'm already sure that I'll be in great disappointment unless I'll find some way to efficiently EQ it for use with my hellish small room. My small room (13x9x8feet) gives some very NASTY peaks below 80hz especially at the room modes.
    From subjective tests made at the listening position, I can only hear peaks but no nulls (tomorrow I'll make some objective tests with an SPL meter and some sine waves).
    These under 80hz peaks really lower my enjoyment out of my HT (even without a sub). The plan is to cross all the speakers at 80hz (for HT) and let the sub do all the work below this frequency. The problem is, unless I'll find a way to tame it's response at the room modes, I'm in BIG trouble.
    Can the Behringer cure this problem ? I mean, some of my peaks should be about 8-9db (at least), so it will have to be quite good in order to help me.
    What do you think ?
     
  2. Jack Gilvey

    Jack Gilvey Producer

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  3. Deane Johnson

    Deane Johnson Supporting Actor

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    From what you describe, the Behringer DSP1100P wouldn't even work up a sweat on your project. I have an 18" Velodyne and had a 16db peak at 42 Hz and the BFD took it out on the first try. You can't go wrong with this unit.
    If you'll do a search in this section (Avanced)for BFD, you'll find a number of detailed threads on how to use the Behringer.
    Deane
     
  4. Jones_Rush

    Jones_Rush Stunt Coordinator

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    I think I'll go with the Shiva, I can get it for a great price ($106). I figured that the bass driver is not going to play a major role in my room, and the Shiva is pretty good. Currently the major role belong to the room modes,
    I'm currently negotiating with Behringer's agent to see if he can take their place as leading star... :)
     
  5. Jones_Rush

    Jones_Rush Stunt Coordinator

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    Say Deane,
    Do you feel that,subjectively, after using the Behringer, you now have a flat response below 80hz ?
    Have you felt, prior of using it, that your bass response was a "living hell" ? (sort of like I feel now).
    Did it completely fix it ?
     
  6. Deane Johnson

    Deane Johnson Supporting Actor

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    What happened with my 16 db spike is that my sub ended up turned down to accomodate it. Sort of an average between it and the lower levels. As a result, when a sound was comprised of a spike frequency, it sounded pretty loud. If not, it didn't.
    Smoothing out the response made the sub sound significantly more powerful. After all, I'm now getting bass response fairly flat all the way down to 20 Hz and below.
    One of the major differences is that before the BFD equalization, it was obvious when the sub seriously kicked in and you thought, wow, listen to that sub.
    Now you don't realize it's a sub, it just sounds like that corner of the house fell off. It's so solid and big it almost hurts. Of course, I'm using an 18" Velodyne servo. You mention a $106 Shiva. I'm not familiar with what that is, but I don't think anything that costs $106 will break your windows or anything, BFD or not.
    "Completely cure" is a relative term. Completely cure would be a flat response line that looked like a highway across Kansas. The fact of the matter is that when you run the AVIA sub frequency sweep from 200 Hz down to 20 Hz, the idea is to try and get it to not swing more than 4 or 5 db either side of center. That would be a victory.
    Don't try to take out nulls of more than a couple of db or so. Serious room nulls don't move, but you can sure mess up a good sub trying. If there is a room cancellation, it's going to cancel no matter how much you try to pour out of your sub. Just live with them or rearrange the room. They pretty much go by unnoticed.
    I never previously described my sub experience as a living hell, but I can tell you that by comparison with how it now sounds with the Berhinger it was pretty bad and I didn't even know it. I thought subs were supposed to sound thumpy instead of powerful.
    Deane
     
  7. Jones_Rush

    Jones_Rush Stunt Coordinator

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    I have just measured my room, here are the results:
    [​IMG]
    The rough data:
    90hz= +2```````59hz= -2
    89hz= +1```````58hz= -2
    88hz= +1```````57hz= -2
    87hz= +0.5`````56hz= -2
    86hz= +0.5`````55hz= -1.5
    85hz= +1```````54hz= -1
    84hz= +2```````53hz= +0.5
    83hz= +3```````52hz= +3.5
    82hz= +5```````51hz= +6.5
    81hz= +6```````50hz= +8
    80hz= +7```````49hz= +9
    79hz= +7```````48hz= +8
    78hz= +5.5`````47hz= +7.5
    77hz= +4```````46hz= +8
    76hz= +3```````45hz= +9
    75hz= +1.5`````44hz= +10
    74hz= 0````````43hz= +11
    73hz= -1```````42hz= +12
    72hz= -2```````41hz= +11
    71hz= -1```````40hz= +9
    70hz= 0````````39hz= +8
    69hz= -1.5`````38hz= +7
    68hz= -3```````37hz= +5.5
    67hz= -2```````36hz= +5
    66hz= +1```````35hz= +4
    65hz= +0```````34hz= +2
    64hz= -3```````33hz= +1
    63hz= -4```````32hz= 0
    62hz= -3
    61hz= -2
    60hz= -1.5
    I made the measurments using a Radio Shack SPL meter,
    I positioned it exactly where my head suppose to be at the sweet spot. The SPL meter was dialed to 80db, and all the db variations are from that level.
    I didn't use the RadioShack correction values.
    I made all the measurements twice, they all came out the same +/- 1 db.
    I used computer generated sine waves for signals.
    Since I don't have a subwoofer yet, I used my bookshelf speaker as a sub, my bookshelf speaker is rated to be
    -3db at 33hz unechoic, it had no problems playing down to 32hz, I placed it exactly where my sub is going to be.
    (the bookshelf speaker is the nOrh 9.0)
    Do you think that the Behringer can help in my situation?
    I mean, It can only EQ 12 frequencies, will it suffice ?
    Btw, look at the 40hz - 50hz response, like I said, hellish room...
     
  8. Deane Johnson

    Deane Johnson Supporting Actor

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    This is a typical looking response curve for a sub and better than some. The Behringer is perfect for this correction. You won't need more than 4 to 6 of the 12 filters.
    Remember, not only do you select the center frequency for the filter, but you can also vary the width of the notch. I would find the exact center frequency of those two biggies in the 40hz to 50hz range. Assign a filter to the center of each one. Remember, you can literally move the center frequency of the filter up or down one Hz at a time. Apply the required cut and run another curve and see what happened.
    You have something going on around the 80 Hz crossover point. I'm not sure what, but hopefully you can drop the sub level a little there to bring it in line. If it's coming out of the receiver to the mains, you can't drop that, but I rather think it's just the sub and mains combining levels and dropping the sub should make a big improvement.
    You can play around a little with boosting the nulls in the 55 to 75 range, but I'd be real careful not to add much more than 2 or 3 db. Then, if it doesn't help, take it out. No use in driving the sub harder than necessary for results.
    The Berhringer takes some learning and if you haven't done so I would urge you to do a search in this section for BFD and read other posts.
    The instruction book is not great in some respects, having been translated to English from German. One thing that is wrong is that the 1100P is in the circuit when the green in/out light is on. I think the book states it opposite. This has thrown a few people for a little while.
    It's probably best to use pre-set memory position #4 or #5. The others have other programs in them that have to be un-done, so I just stay away from them.
    I would look at center frequencies available on the Behringer and assign a filter number to each frequency. I'm using something like filters #2, 3, 6, 7, and 8. I have the others in reserve. Any filter is assignable to any center frequency.
    I'm sure you'll have more questions once you get your machine.
    Deane
     
  9. Sundar Prasad

    Sundar Prasad Stunt Coordinator

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    Jones,
    The BFD will do everything you need to get done and quite a bit more (if you want it to). Check out the graph below for a sealed Shiva in a 100 litre box (the box is stuffed nearly full and so its effective volume may be about 115 litres). All measurements are made in the listening position. The sub is corner loaded. Main speakers are PSB 500s driven by Marantz MA-700 monoblocks.
    The test CD is a homebrew collection of sine and warble tones generated by CoolEdit. The peak level of all the test tones as recorded on the CD is a constant -6 dB. Test tones are played through a Pioneer PD-65 CDP (used as transport) and pre-pro/bass management duties are handled by a Denon 3300. The mains are set to 'Small' in the 3300 and so all bass below 80 Hz is directed to the sub.
    The sub itself is driven by my older NAD 7240PE receiver. Individual voice coils of the Shiva are driven by the 7240's amps which can get to about 45 RMS/ch, but they have access to headroom of 6 dB before they clip. The total transient power available for the sub is about 350 W.
    Calibration was done at an SPL of 80 dB. The curves have been corrected for the roll off in the RS meter's LF response.
    [​IMG]
    As you can see, the sealed Shiva's response rolls off fairly quickly below 35 Hz (the F3 point in my room). I used 5 filters on the BFD to tame the room peaks and push up frequencies below 35 Hz. The equalized response is quite good. The warble tones yield a slightly better response curve. I have since dropped one filter to bring the total filters in use to only 4, and the listening position response has been smoothed out a bit more at about 55 Hz.
    I realize I have lost amp headroom by not going with a ported design and chosen to boost low end response by EQing, but don't care. Ported designs are more complicated and I prefer the sound of a sealed sub. The NAD amplifiers haven't shown any sign of stress before my ears have. My listening is 80% music & 20% HT and I love what the sealed Shiva has done for the low end in my fairly small room.
    I don't care if this configuration will reach 120 dB peaks at the listening position as my target was quality first. Note that the BFD alters the phase of the frequencies it is processing (an unavoidable side effect of the way these real-time filters are designed). I found that I had to set my sub's phase back to 0 degrees (I can use only 0 or 180 deg by flipping speaker cables to the sub) after I started using the BFD to get an extra couple of dB in the 20 - 30 Hz region.
    I am quite happy with what the el-cheapo BFD has done for my listening experience. I am very sure it will do a great job for you too.
    Sundar
     
  10. Richard Greene

    Richard Greene Stunt Coordinator

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    I recently decided add an external 30 band 1/3 octave equalizer to supplement the 5 band 1/2 octave bass
    equalizer included in my Audio Control Richter Scale
    active crossover.
    The Alesis #230 was only $219 at a local Mars audio store (a national chain I believe).
    Using the Alesis allowed me to reduce my bass variation from +/10dB (unequalized) to +/-6dB (and perhaps to +/- 5 dB with a little more experimentation).
    My floor-to-ceiling bass resonance is in the 40-50Hz. range and looks somewhat like your room resonance when charted. The 40Hz. and 50Hz. Alesis controls were effective. If the fixed equalizer controls of a graphic equalizer are in the right place for your room, it's not necessary to buy a more expensive parametric equalizer.
    I have experimented with using the Alesis equalizer with my
    satellite speakers but it's not clean enough to produce
    high end sound, so I recommend it only for subwoofers, where
    a little noise will be completely inaudible.
    I hope you realize an equalizer does not eliminate room standing waves -- they just allow you to launch less bass
    into a room at frequencies that make the room "ring" --
    but the room resonance is still there -- so you have deliberately created a frequency response error by reducing the amount of energy launched from the subwoofer at certain frequencies (NOW) so the effects of the room (LATER) are
    less audible (but still there).
     
  11. Jones_Rush

    Jones_Rush Stunt Coordinator

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    Sundar,
    The Behringer (at least accroding to the graph) has done miracles in you room, WoW, you get -3db at 20hz!!! that's great!, have you checked the validation of this graph at higher SPL's (like 95-100db) ?, if it is valid, I don't understand why you are only "quite happy" with it and not
    VERY VERY happy...
    I am pretty shocked at the relative bad response you are getting without the BFD, -19db at 20hz ??? how is that?,
    I talked with Dan Wiggins from Adire regarding a sealed 88.5 liter enclosure using the Shiva driver, and he told me that I will be getting -8db at 20hz UNECHOIC!, meaning,
    that with room gain, I should easely get -3/4 db at 20hz without any EQ at all. You said that your room is quite small, what is it's HxWxD ?. Another thing I don't get is your flat graph above 35hz without the BFD, you are getting -3/+6db all the way up, how is that possible in a small room ?.
    Your graph shows a classic behaviour of bass in a large room, where at least one wall is missing (meaning open).
    Another thing which could explain the high F3 is the extra stuffing you did, usually what it does is to flat the higher frequencies (above 40hz) on the expense of a higher F3, but MAN, -19db at 20hz just can't happen only due to stuffing.
    The Behringer gave you an increase of 16db at 20hz,
    I've heard a lot of people saying you shouldn't try to raise db levels above 3-6db with the Behringer, because it will lead to overdriving the amp too much, how did you solved this problem ?
    For measuring my room I used my bookshelf speaker as a sub (placed it at the sub position, since I don't have a sub yet), my speaker has a 5.5" driver, and at the listening position I measured it to go down to 30hz -2db. I just can't figure how you, with a 12" driver get only -8db at 30hz, True, my bookshelf is a ported design (norh 9.0) and it uses the best 5.5" woofer there is, but still, a 12" driver in a sealed design in a small room should beat it without a problem.
    I am totaly confused...
     
  12. Jones_Rush

    Jones_Rush Stunt Coordinator

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    Hi Richard!
    +/- 6db bass response is quite good, I'm happy the EQ helped you.
    I don't want to rub salt on your wounds, but the parametric EQ I'm talking about (the Behringer) cost around $150.
    So apparently you paid for your regular EQ more... (stil, +/- 6db is great).
     
  13. Sundar Prasad

    Sundar Prasad Stunt Coordinator

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    Jones,
    Lot of questions from your end [​IMG] and I will try my best to answer them.
     
  14. Jones_Rush

    Jones_Rush Stunt Coordinator

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    Sundar,
    Thanks for your answers, I am looking forward for you additional tests.
    You said:
    "good performance from audio gear is a basic requirement and not a cause for celebration ".
    Let me show you my side of this story. Before purchasing my new main speakers, I used some mid/low-fi bookshelf speakers, I was quite satisfied with their performance, but still, something told to upgrade. When I got the new speakers (norh 9.0) the difference in quality was really big, but I wasn't using "excessive superlatives" to describe it, the reason is, I never suffered with my last speakers, so even though I now have improved sound, I can't say I haven't enjoyed the sound before. ON THE COMPLETE OTHER HAND, I am suffering, in every single movie I see, from the lousy,horrible,boomy bass response of my room, and I thought that there will be no solution unless moving to another room (which is far from me now),now, it seems that there is a product which can solve this bass problem, and for cheap. This IS a BIG cause for celebration. You on the other hand, never really suffered from bad bass, your frequncy response above 35hz is an audiophile's wet dream.
    So you didn't get less than 30hz response, so what? how can you miss something you are not familiar with (let's see you loose it now...).
    Anyways, I must figure out what is going on with your sub at 20hz without the BFD. There is one thing you can check to find out if your listening position is inside a 20hz null. You need to do as follows:
    1)Choose a frequency which correlate with the 0db SPL in your graph, for example, I can see that 60hz is one of them.
    2) set the volume of your system to play a frequency sine wave of this frequency (60hz) at 80db, measured at your listening spot.
    3) Once you do it, take the SPL meter from your listening
    position and put it very close to the sub's driver (5 inch), the SPL level will be much higher than 80db, of course, write the SPL level you get on paper (for that matter, let's say you'll get 100db SPL).
    4) Move the SPL meter back at your listening position and play a 20hz sine wave without changing the volume of your system, the SPL meter should read -19db = 61db SPL.
    5) move the SPL meter once again close to the driver
    (5 inch) and check the SPL level.
    If the level you'll get will be close to 92db ( around
    8db lower than the 60hz read), then you are in fact sitting inside a null, on the other hand, if the SPL meter will show a reading around 81db , then your sub is definitely the problem. (the SPl meter, in case you are sitting inside a null, will only show around 92db (not 100db) since the Shiva is rated in your enclosure to go down to 20hz -8db, and no, these are real measurements not just sims)
    If you can make this test and post the results I would be grateful.
     
  15. Sundar Prasad

    Sundar Prasad Stunt Coordinator

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  16. Jones_Rush

    Jones_Rush Stunt Coordinator

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    "Jones - It was Deane who said that the 'thumpy' bass from his Velodyne became much better and controlled after he put the BFD in the signal path.".
    A brief moment after you post this message I finished editing mine, and hoped you havne't read the old one. Guess NOT! :)
    But I wrote something different, you may want to check it.
     
  17. Sundar Prasad

    Sundar Prasad Stunt Coordinator

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    Jones,
    Can't post more curves yet, but I confirmed that the listening position is in a pretty nasty hole for frequencies below 35 Hz. Near-field tests of the sealed Shiva show that it is about -8 dB at 20 Hz. This means that both the sub and the enclosure are doing their job. Since the room null at my listening position was taking away a whopping 15 dB or so, I have ended up moving the sub to another corner of the room. At the listening position, I am down by about 4 dB at 20 Hz instead of 19 dB down earlier (room gain is working for me this time). Hell I am down only 8 dB at 14 Hz. This will be very easy fodder for the BFD to correct.
    Thanks for making me think about this one. I'll equalize the room tonight and post some curves in the next couple of days.
    Sundar
     
  18. Jones_Rush

    Jones_Rush Stunt Coordinator

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    Sundar,
    You had me scared there for a moment, when seeing your
    -19db at 20hz for a 100 liter closed Shiva, I almost gave up my closed sub project. I too have a small room, even smaller than yours, but still, -19db at 20hz is well beyond my room's gain capabilities to recover.
    -4db at 20hz sounds really good, heck, you can now enjoy both worlds, having the high SPL levels (down low) of a good ported design, while having the great quality bass of a sealed design.
    One thought crossed my mind, when you EQ'ed your room to be flat at 20hz (actually doing the unthinkable, impossible task of filling a nasty null) you actually added +15 db at 20hz to other palces in your room, which were -4db at 20hz.
    When watching movies, you probably got 100db of bass extension at your listening spot, which mean, at other places in your room, the SPL level was 115db at 20hz!!!
    That puzzles me a bit, how is it possible for one place in a small room to have +15db at 20hz while at the other 0db? 20hz frequency is all about "feel", huge amounts of air moving in your room, shaking everything inside it. Actually, this is the first time in my life I hear/read that someone had large deep at 20hz.
     
  19. Sundar Prasad

    Sundar Prasad Stunt Coordinator

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    Jones,
    Here's the latest results with the BFD and the Shiva in a new corner of the room:
    [​IMG]
    I ended up using 4 filters on the BFD for toning down the huge room mode around 48 Hz and lifting the response below 30 Hz. As you can see, after equaliztion, jacking up the sub to 91 dB at the listening position produces a curve that behaves pretty much like the 81 dB curve. This shows good linear behaviour of the sub and the Behringer box.
    One of my favourite test CD's for deep bass is Enya's Watermark. She uses gobs of low frequency synthesized notes in her songs. Needless to say, the sound was superb with excellent balance between midrange and bass, and just the right amount of kick down low. Also listened to U2, Lenny Kravitz, Limp Bizkit, Metallica S&M, and Rage Against the Machine. Flat bass is to die for. When I switch the BFD filters off and listen to the same music, the first impression is wow - really heavy bass. But this gets tiring after a while and switching the filters on brings back significant clarity to the sound.
    Anyone with a sub and room modes that go up beyond 6 dB will do themselves a huge favour by getting some kind of EQ unit to flatten the hump. The BFD adds serious value to a sub - be it a DIY or a commercial one.
    Sundar
     
  20. Timmy

    Timmy Stunt Coordinator

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    Sundar
    Perfect implementation of the BFD. I also liked your graph showing plus/minus. Your BFD corrected curves all fall inbetween plus/minus 3 db; which is a great place to call it a success.
     

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