Avia subwoofer/LFE frequency sweep - questions, help

Discussion in 'Archived Threads 2001-2004' started by ThomasL, Jan 1, 2002.

  1. ThomasL

    ThomasL Supporting Actor

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    Hi, I just did the LFE/subwoofer frequency sweep in Avia and have a few questions. Is this sweep supposed to produce the same db level throughout the entire sweep? So, if I set my volume at a level that I know produces 70db using the speaker balancing tests (the subwoofer/left front alternating test) in Avia, then the sweep should always stay around 0 on the RS soundmeter assuming I set it for 70, is this correct?
    Using my RS soundmeter, I got some interesting results with my small Sony subwoofer:
    100 - ~90 hz - weak response -8 db
    90 - ~68 hz - even response pretty much with some bouncing back and forth.
    ~67 - ~60 hz - serious drop off back down below -8 db
    ~60 - ~39 hz - boom! [​IMG] Went off the scale at +6 in the other direction.
    < ~38 hz - drops off rather rapidly as expected with a small sub such as this.
    Assuming my assumptions above are ok, does this mean that this subwoofer is what people would describe as "boomy" and is designed to give one a boom in the 40-60 hz range. The "hole" in the mid-60s is interesting though as is the weak response around 100 hz but what bothers me most is simply the poor consistency of the response through the entire frequency range.
    So, did I do this test correctly and if so, what are the best 8 inch subs in regards to consistent frequency response from 30 - 100 hz?
    thanks for any help!
    --tom
     
  2. Vasanth B

    Vasanth B Stunt Coordinator

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    Thomas, I can't answer all of your questions but it might help others if you posted the exact model of Sony sub, receiver/amp your using, room size and placement of the sub.

    Since you mention 8", I think you have the smaller Sony WA-SM20. The 12" WA-SM40 is supposed to be the best sub in this price class, so maybe you will get better performance with an upgrade. The 12" Sony is available for around $150.
     
  3. ThomasL

    ThomasL Supporting Actor

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    Hi, yes, I'm actually using the sub that came with the SA-VE315 Sony package. I believe it's probably comparable with the smaller Sony you mentioned. My room size is probably 13x13 thereabouts and the sub is positioned in the upper right hand corner from the listening position on the floor about 9 feet away (i.e. to the left of the tv in a corner up against the wall entertainment unit). Unfortunately this is the only location it can go. I'm mostly curious if I did the Avia test correctly and what subs are out there that produce a more consistent response to the frequency sweep.

    thanks!

    --tom
     
  4. ThomasL

    ThomasL Supporting Actor

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    Bump [​IMG] Anyone have any thoughts? Guy, are you out there?
    I forgot to mention that I'm using a "run of the mill" Pioneer D309 receiver with the crossover frequency set to 100 hz, the LFE setting at 0db and the rest of my speakers set to small (Newton M50 fronts, MC300 center and MC100s for rears). Also, I went to the following site that Guy wrote (and suggested in another recent thread) and based on what is written here, it seems that the LFE frequency sweep should give you the same db results as the other calibration test tones assuming you set the volume level to match that eariler calibration (i.e. -xx = 75 db from the listening position) http://www.svsubwoofers.com/usingavia.htm
    It also seems like I should be able to run the low frequency sweep for the other channels are everything should come out of the subwoofer and yield the same results. I will try that tonight.
    My main question/problem is determining if the Sony sub that came with the SA-VE315 should be upgraded to something better. I have limited space and a small room so I'm not looking for something bigger but just something better if it can be had for
     
  5. Jeremy Anderson

    Jeremy Anderson Screenwriter

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    Question: Are you accounting for the inaccuracy of the SPL meter for certain frequencies? The manual that came with your meter should have a correction chart that shows what number you should add/subtract to the meter's reading for these frequencies. I'm sure if you did a search here, you could find it as well.
    Otherwise, it may be a placement or room acoustics issue. It's near impossible to get flat response from a sub without equalization, so if I were you I wouldn't worry too much about it. But by all means, upgrade! There's no greater joy than having a movie rattle your teeth! [​IMG]
     
  6. Rick Radford

    Rick Radford Supporting Actor

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    Thomas,
    I think square rooms have specific acoustical problems. I have a small square HT room too.. about 12 x 12 x 8 which interacts with my SVS 20-39cs/S700 by generating some interesting peaks and valleys. My next step is to get a parametric eq and work on flattening the in-room response of the sub.
    From what I've read, a sub upgrade will greatly benefit you. Up the ante a $100 and get the HSU VTF-2. Or, better yet (if you have a spare amp), get the SVS 25-31 CS for $369.
    If you're interested in the eq approach, the Behringer BFD 1124p is going for ~$130. [​IMG] But my $$ would be on the sub upgrade first!
     
  7. Jason Wolters

    Jason Wolters Stunt Coordinator

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    Thomas,

    For what it's worth, your results sound pretty similar to mine. I don't think it is reasonable to expect the needle to hover around reference level all the way through the sweep. Perhaps some of the experts can best explain why, but that is my understanding. It is supposed to be fairly flat all the way through, but I think room acoustics and as well as bass management issues will alter this drastically. I have a Paradigm PDR 10 sub. Mine goes a little lower than yours. I just upgraded the sub from a little Aiwa 8". On the frequency sweep, I haven't noticed a huge difference on requency response on the PDR 10. I have however noticed a BIG difference in the quality of bass I get during a DVD. My layman's explanation is that the Paradigm seems to give more "percussion" (you can feel the bass) and the PDR 10 does not distort like you often hear a lesser sub do.
     
  8. ThomasL

    ThomasL Supporting Actor

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    Just to followup, I put my Sony sub on the music setting that helped to flatten out its response somewhat. There's still a drop off somewhere in the 70-60 Hz range and a "boom" in the 40-60 range but it didn't seem as dramatic on Music mode as opposed to Movie mode. I think Movie mode is going for the big boom between 40-60 Hz while Music gives one a little more of an overall even responses from 40 - 100 Hz.
     
  9. BruceD

    BruceD Screenwriter

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    A simple analogy will help explain why you have bass peaks and valleys in your specific room and why they are going to be different for every room with different dimensions.

    Think of a bath tub filled with water;

    1) drop the soap in the water and watch the ripples or waves (same as sound waves) evenly radiating out from the soap.

    2) Now watch what happens when these waves hit the side of the tub and reflect back.

    3) Some waves combine with other waves at the side of the tub and produce larger waves.

    4) Some waves meet other waves bouncing of the wall and cancel each other.

    So waves that cancel are valleys, waves that re-inforce are peaks.

    This is what the sound waves are doing in your room and the incresed SPL is a peak, the decreased SPL is a valley.

    Moving the speaker or the listening position will also change these values.

    Food for thought.

    BruceD
     
  10. JohnDG

    JohnDG Stunt Coordinator

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    FYI: I've really been working with the PDR-10 lately, and I've found something interesting: turning down the cross-over on the sub really allows you to boost the low-end, and flattens out the frequency repsonse curve (FR).
    I found this info at http://www.audio-ideas.com/reviews/h...gm-stylus.html . The FR chart shows that, by moving the sub's cross-over down to 90Hz (I use 100Hz), that you can turn up the sub, and thus the low ranges, without adding to the 40-100Hz range. I've checked this out on my sub, and the FR results are very flat, less a room induced lull at 45Hz that I would need an equalizer to remove.
    Now, this is not an SVS :) but for my room I've still only got the sub's power dial at 60% -- so it works for me. It also helps if your mains can go down to 40Hz, allowing you to set the receiver's cross-over at 80Hz. Per a previous post, it is my understanding that setting the sub's cross-over at 100Hz should not step on much of the LFE signal, as this (per specs) has a hard stop at 120Hz.
    jdg
     
  11. Shawn Shultzaberger

    Shawn Shultzaberger Supporting Actor

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    BruceD,
    I have long been trying to understand sound "waves" and how they interact with a room. Your explanation was just what I needed. Thanks! [​IMG]
     
  12. ThomasL

    ThomasL Supporting Actor

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    Thanks everyone...I see how much placement and room acoustics will cause havoc with a balanced response from anything that produces soundwaves.

    But I'm still left with the question of whether I should upgrade to a better subwoofer. The Sony sub that came with the SA-VE315 is listed as being a 6 3/8 inch woofer and my tests show it goes down to about 39 Hz before fading away. It also has very few features - no phase control, no crossover control (it says it has an internal frequency limiting circuitry of 200 Hz - i.e. I assume some circuitry that throws away everything above 200 Hz - but that's it). It just has 3 front controls, on/off, volume/level, and music/movies toggle.

    So, my main question now is if I spend $200-300 on another sub given my physical constraints (it can't be wider than 13 inches and taller than 15 inches), will I really be getting that much of an upgrade? it seems to me most 8 inch subs (besides the Energy S8.2) only go down to the 35-40 Hz range. All the rest of my speakers are rated down to 100 Hz - which is where my crossover is (see separate thread for that discussion) with my fronts being rated down to 70, the center is 80 and the surrounds are 100. So, I figured I want to get a sub that does best in the 30 - 100 range. Is that correct thinking?

    thanks for your thoughts!

    --tom
     
  13. Bob Christensen

    Bob Christensen Stunt Coordinator

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    Thomas: Did you take your measurements at the listening position, which would include hte room loading, or very close to the sub, which would give you a more "room free" response curve?

    If you took the measurements at the listening position, try walking around a little bit with the SPL meter and see if the readings change. This would indicate that the spike may be caused by room interaction. There is also a very good chance that the sub amp itself includes a 6db boost in this range.
     
  14. ThomasL

    ThomasL Supporting Actor

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    Bob, I took them from the listening position but thanks for the tip. I think I'll try from the front of the sub and just turn the volume down to get something within the range of the meter that won't make me go deaf [​IMG] I'm only interested in the seeing the relative peaks/valleys so that should work. It'll be interesting to see if its different.
    thanks,
    --tom
     
  15. Vasanth B

    Vasanth B Stunt Coordinator

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    Shawn
    Keep in mind the analogy of the bathtub ripples is 2D only. You must extend that to the actual three-dimensional nature of sound. So not only are there peaks and valleys on the same plane as the sub woofer, but moving up and down will affect the perceived bass amplitude. I imagine it is not as pronounced of a change as moving around x and y in the room.
     
  16. tommy_esq

    tommy_esq Stunt Coordinator

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    thomas- I believe I am using the same sub as you (the small Sony that came bundled with 4 satellites and a center channel, not sure of the model #). I too am considering upgrading to a bigger sub. I am looking at 10" models, especially the HSU and Rava. I use my system almost exclusively for movies/TV. What models are you considering?? Also, do you think watching movies in "music" mode is actually preferable to watching them in "movie" mode?
     
  17. Deane Johnson

    Deane Johnson Supporting Actor

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    Thomas:
    The Stryke test CD is much easier to work with than the AVIA for this purpose. Tones are stepped, and long enough to get a good reading. And it's reasonably priced.
    I discovered my problems with the AVIA sweeps, but then purchased the Stryke disc and really got a feel for what was going on. I made a chart in Excel, put in a column for the RS SPL correction factors, and an end result.
    I ended up purchasing a BFD to equalize out the peaks and now have by far the best sub performance I've ever had.
    I'm not sure how far you want to go, I just mention these things as some steps that can be taken.
    http://www.stryke.com/
    Deane
     
  18. Rick Radford

    Rick Radford Supporting Actor

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    ThomasL,
    I didn't note your space limitations before.
     
  19. Harold Leroy

    Harold Leroy Stunt Coordinator

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    How does a drop down/suspended ceiling impact all this, good or bad??
     
  20. ThomasL

    ThomasL Supporting Actor

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    Rick, the only place I currently have (without running a wire through a hole in the floor and under the basement out to the other side of the room [​IMG] ) is a small space between the entertainment center and the outer wall of the house. Our family room is small, 13 1/2 x 12 1/2, with the wall entertainment center really shrinking the width by about 18 inches or so. Even if I ran a cable, I don't have much in the way of completely open corners since the other side of the room is made up of an L sofa/loveseat combo with two end tables. It's a nice layout for us giving the room (in fact, it's the only layout since the final wall has a deck door that leads out to a deck) constraints.
    Tommy_esq, if you have the Sony SA-VE315 system then what I would recommend before upgrading the 6 3/8" sub is to upgrade the tin cans that came with it. No offense meant to people who have this system. I used it for 15 months and thought I liked it as well but there is simply no comparison between it and a set of real bookshelves (I have CSW Newton M50s fronts with a MC300 as a center now). The small Sony satellites are way too over-emphasized on the treble side with a huge gap in the lower midrange between them and the subwoofer. I didn't notice it until I played some music with the Sonys and then moved my M50s (from my office) down to the family room and listened. The difference was like night and day. So, my recommendation is to upgrade the Sony satellites/center first (I was going to toss them but a friend took them for free - we still haven't convinced him to invest some money in decent speakers [​IMG] ) and then upgrade the subwoofer after that. As for music/movie, I found that the Sony gives a more even response in the music setting but the differences were fairly minor in my room. If you like an extra "boom" around 45-50 hz before it drops off, then use Movie mode. I personally want my bass not to boom but to mesh "quietly" with the fronts so I can't even tell I have a subwoofer.
    And finally, I did upgrade my subwoofer. I've moved the Sony up to my office where it'll now take part in a computer/music 3 way setup with a 10 year old Pioneer stereo receiver, and a pair of Newton M50s. I figure it's not the best for that but it's a freebie. The subwoofer I bought to replace it is the Paradigm PDR-8. It's an improvement and the bass now meshes much better with the fronts for a better overall bass response. Less distortion and this goes about 10 Hz deeper than the Sony. Given my space constraints, I was really limited in my choices. My first choice was the Energy S8.2 but I could not locate a local dealer where I could listen to it and buy it. I also looked at the Mirage FRx-8 at Tweeter but I didn't like the look of it at all. Given the size of our room, an 8 inch does nicely but if you can, I'd recommend the 10 inch for $50 more, just to get more lower response.
    cheers,
    --tom
     

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