The pros and cons of aiming for a flat frequency response

Discussion in 'Archived Threads 2001-2004' started by Javier_Huerta, Jan 5, 2003.

  1. Javier_Huerta

    Javier_Huerta Supporting Actor

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    There are two camps in the battle.
    The first is the SVS camp. Their subs are aimed for a flat frequency response, which results in an in-room response with a hump in the lower frequencies.
    The second is the Tempest camp. Adire says there should be a "drooping" response in the bass to make it as flat as it can be.
    I'd suppose SVS has an edge in Home Theater, whilst the Tempests have the edge on accurate music reproduction, since a flat frequency response would also imply a worst transient response, plus the extra bass would muddy the lower frequencies.
    Am I right, or is it too early for me to think clearly? [​IMG]
    Javier.
     
  2. Robin Smith

    Robin Smith Stunt Coordinator

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    As far as I understand it, flat should be the goal of everything if you want accurate reproduction of whatever your source material is. Whether you want flat or not is a different issue.
    Boosting certain frequencies in a sub may make more of a punch in the gut enjoyable sound, and is more common with pre-manufactured subs. But be clear, it is not an accurate reproduction and as such is not replaying the sounds as intended by the source.
    Ultimately, go with what you enjoy the most, if you like the boost, then leave it, if you want accurate then go for accurate. I was initially let down when I removed the boost from my sub amp, but after a week or so, I felt it was better than before and less "obvious" that there was a sub there. It blended in well with my mains and was definetely there when needed for low end reproduction.
    I am pleased with my sound and have bought a BFD which I will be using to flatten things out even more when I get my new DVD player.
    My two cents
    Robin Smith
     
  3. Patrick Sun

    Patrick Sun Moderator
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    Caution: Do not turn this thread into a SVS-vs.-Adire thread. Neither companies are the be-all, end-all in bass reproduction. It's not fair to asbribe your bias of what these companies are about.

    Let's keep this thread on flat/accurate bass frequency response vs. "salted to one's taste"/personal preference bass frequency response. There are plenty among both of those camps.
     
  4. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    I say all speakers should be perfectly flat, and all rooms should be properly acoustically treated accomanied by high definition parametric equalization.

    Then if they don't like the way that sounds then keep on adding and removing items until satisfied.

    If people complain about the effects their room has on bass and can't get treatments, then they should get the sub with the abnormal response to compensate.
     
  5. Brett DiMichele

    Brett DiMichele Producer

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  6. Mark Seaton

    Mark Seaton Supporting Actor

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    Chris,

    Have you ever listened to a home theater subwoofer which is "flat" inside a car?
     
  7. Michael R Price

    Michael R Price Screenwriter

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    The SVS subs are overdamped just like a Tempest Adire Alignment or EBS, as far as I know. The published response graphs from the original subs show they are down 4-6db anechoic at tuning.
     
  8. Wes Nance

    Wes Nance Stunt Coordinator

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    There is also the issue of whether or not you want a "house curve" in your response, which basically tends to be a 12-15db rise from 100-30hz, and then flat down to tuning fz. The theory behind this is that for a lower frequency to "sound" equally loud to the human ear it has to be at a higher db level than a higher frequency. I'm not an expert, so do a search on "house curve" in the speaker forum for more info.

    In the speaker forum, there have been many very helpful BFD threads, and most folks end up dialing in a house curve on the BFD, rather than ruler flat. (Although a house curve could be considered a flat response that tips from 30 to 100hz or so). Those that managed a perfectly flat response felt the low bass sounded lacking.

    In my room without a BFD, I had 15db humps and dips in the middle of the response. I would bet any sub in your average room is so ragged that you want to EQ it anyway, at which point I would rather have some extra output to pull down rather than a dip to boost.

    Also, I have a medium to small room (15x22) with low ceiling (6'5") which is totally sealed off from the rest of the house, and don't notice appreciable room gain.

    My sub design models an F3 of 21hz or so, which should be a big rise with room gain, but for some reason I don't see that in my room.

    I think a BFD or other parametric EQ should be factored into the cost of the sub. . .

    Wes
     
  9. Greg Monfort

    Greg Monfort Supporting Actor

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    >There are two camps in the battle.
    ====
    What battle?!
    ====
    >The first is the SVS camp. Their subs are aimed for a flat frequency response, which results in an in-room response with a hump in the lower frequencies.

    >The second is the Tempest camp. Adire says there should be a "drooping" response in the bass to make it as flat as it can be.

    >I'd suppose SVS has an edge in Home Theater, whilst the Tempests have the edge on accurate music reproduction, since a flat frequency response would also imply a worst transient response, plus the extra bass would muddy the lower frequencies.

    >Am I right, or is it too early for me to think clearly?
    ====
    The goal is flat frequency response in-room (combined driver/room response) for music and flat amplitude response in-room for DD/DTS HT (gets louder with decreasing frequency to compensate for our hearing curve). Note too, that this curve applies to the HF response also, something that I've never seen mentioned/discussed on any of the HT forums.

    Based solely on your statements, the SVS might meet this criteria if there's enough room gain, and for music would then be EQ'd to a lower Q to be flat FR for music, so it may have both applications covered within its 'x' peak SPL capability without the need for any/much increasing boost with decreasing frequency.

    If a system is designed to account for any boundary/room gain to get an in-room flat FR, such as Adire espouses, then for HT it would need to have its FR boosted considerably to obtain a flat amplitude response, which it may not be able to handle, or at least do so at low distortion levels.

    Many folks can't do HT's flat amplitude at any appreciable volume due to being in an apt./condo, or so-so stick constructed house (I still haven't repaired all the tape joint cracks from my foray into high SPL flat amplitude response), so from a practical POV, designing an in-room response for music (or some point in-between) makes sense to me.

    So no battle IMO, only choose what suits your room/budget/listening preferences since it's just entertainment, not a religious dogma.

    GM
     
  10. Stephen Dodds

    Stephen Dodds Second Unit

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    I EQ my speakers for a dead flat in room response for both the highs and the lows. It doesn't sound as bassy as most full range systems I've heard, but it does sound very accurate, and the low notes are definately there.

    Steve
     
  11. Jack Gilvey

    Jack Gilvey Producer

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  12. Lewis Besze

    Lewis Besze Producer

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    Well let just say,that Tom's "philosophy" was always I paraphrase:"don't rely entirelly on room gain, designing a sub,but accept it as a possible extra good thing down on the road."
    Those of us who been around long enough remembers that Tom and Dan used to debate a lot of issues here,but they agreed on more things then dissagreed,and they always conducted themselves as gentlemean.
    It was fun!
     
  13. Aaron_Smith

    Aaron_Smith Stunt Coordinator

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    Makes me happy to have nice headphones. [​IMG] What room gain?
     
  14. Seth_L

    Seth_L Screenwriter

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  15. Javier_Huerta

    Javier_Huerta Supporting Actor

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    Just a quick footnote: no harm intended in my comments. Clearly, I always thought the SVS had flat frequency response and Adire used a drooping curve. I was just thinking which design would better be suited for music or HT. Clearly the issue of "house curves" and the like plays a big role in low bass reproduction.
    I don't have any intentions of turning this into an Adire vs. SVS thread. More like "what should I be aiming for, a drooping or a flat frequency response on a sub"? Sorry if the meaning came out like it did. [​IMG]
     
  16. For music, you'd rather have it roll off early than give you an exagerated low end responce. For HT, you'd rather have the extra slam and extension than an early roll off.

    I personally subscribe to the early roll-off/room gain camp. Every room I have been in has noticable room gain. Let the room flatten the roll-off and maybe have to EQ a little to flatten vs always have to flatten a pre-room flat responce with EQ since all my rooms have the gain.
     
  17. Seth_L

    Seth_L Screenwriter

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    It's easier to remove extra bass, than it is to try to fill a dip in the response though Anthony.

    Seth
     
  18. Mark Seaton

    Mark Seaton Supporting Actor

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    Mostly true Seth, but we aren't talking about a null at a listening position, but rather recessed response. Room gain is very real, and can be used to your advantage. This could be the difference in getting down significantly lower or making a box 1/2 as large.

    Obviously people missed my comment about car subs. If you designed a subwoofer to be flat anechoically for a car you will either have a huge sub or will be limiting the upper frequency efficiency severly.

    To get a rough idea of what you can expect, look at the ceiling height (shortest room dimension) and determine the associated quarter wavelength. This is where the room gain will start to be observed. A further gain will be seen corresponding to the other dimensions of the room, as well as the longest diagonal. The construction of the room determines how much gain will be observed. We have a prototype sub which is about -10dB at 12Hz which measured quite flat to below this frequency. Again, this is quite analogous to a car's cabin, yet there tend to be more losses due to construction of walls and openings in homes.

    Regards,
     
  19. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    Good point, Jack. Any extra output at 25Hz and below is gonna be all tactile for me. And my butt's just not calibrated well enough to care. That's right, I said "butt" and "calibrated" in the same sentence.

    I'd have to have a bloated response in the 35-40Hz range to actually notice the difference. So for large rooms I'd say design it flat.

    BTW, where do bass shakers fit into all this? I'd think they bloat the subsonics WAAAAAAAAAY out of proportion. Yet they get no disrespect from the gotta-have-it-flat camp. Or maybe I missed it.
     

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