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Natural extension of driver + enclosure VS increased extension via EQ

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  • Natural extension of driver + enclosure VS increased extension via EQ

    Coming from a pure audiophile (is that the right word?) stand point. How would these two systems compare? One system reaches 35hz f3 via enclosure and driver. Second system has a f3 of 55hz via enclosure and driver but eq is used to increase extension to match the first system f3 of 35hz. Headroom and excursion is not a limiting factor in this experiment.

    I am asking because in all my experience, boost eq has been 2nd to cutting. Boosting would be the main function to extend a woofers response, though the corrective curves would not exactly be narrow, broad curves being more transparent in this case.

    How do you guys feel about this? Acceptable? Does System one have the advantage sonicly?

  • #2
    Headroom and excursion is a limiting factor, because EQ eats up both in large amounts.
    www.billfitzmaurice.com
    www.billfitzmaurice.info/forum

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    • #3
      If the EQed system uses a sealed woofer alignment, it would be the superior system, in my experience. Headroom is usually not big a problem for most music playing systems. 85db out of just about any reasonable flat system in a reasonable size room is going to be pretty damn loud.

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      • #4
        Just based off of who replied.....I should just walk away lol! Please allow me to play devils advocate, something I do well, only for the intentions of learning.

        Lets say "Yes"....is the general consensus...which it seems to be regardless of what I say. Lets talk about the cons of using eq. Not all eq is created the same nor is eq perfect. In particular, boosting can create aliasing but for what I've just learned, low register boosting will not be an issue. "If you need to use high-Q (narrow-bandwidth) filters, the ear seems to be very sensitive to their effect when boosting, but surprisingly oblivious when cutting." - Thats well known but once again, in the lower register, for this task, broad-bandwidth filtering (1/3rd octave or lower) spear head the task, thus, once again, a non issue, as long as good technique is applied.

        Unless using linear phase filters (which usually result in too much latency for multimedia) minimal phase filters are going to change the curve, up register, sympathetically, but maybe not to a detrimental degree, but still phase conflicts might increase in total.

        Thats all I got, which means I probably don't have much of an argument, which is a good thing.

        This conflict of thought came about as I design my latest, as some of you know. I have a group of woofers narrowed down, all which can have enough headroom room and xmax to reach desired design spec; f3 (30's at a particular volume) but some of the woofers need eq to get there while others can reach without eq.

        So in order to screen out some of the choices, this aspect needed to be discussed. The less eq needed, the better, is generally the ultimate truth, regardless if an acceptable method to increase extension, I tend to believe some type of side affect will result, even if minuscule in amount, but hopefully not enough to affect woofer choice.

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        • #5
          If you take a woofer in a bass reflex alignment and the same woofer in a sealed alignment with EQ to boost and match the response, the bass reflex will win just about every comparison except for enclosure size (assuming smaller is preferred). The sealed alignment will have more output capability below the bass reflex low frequency roll-off (due to unloading of the cone below tuning), but it's usually not significant at that point anyway. The bass reflex alignment is more sensitive and more efficient in the low frequency, which means less power required, less excursion, and therefore lower distortion. Some will argue that the bass reflex system will be "boomier" and "slower" and will relate it to higher group delay, but the reality is that after applying the EQ to the sealed system, you have a system with the same group delay. As Bill already alluded to, EQ eats up excursion and power VERY quickly. A 6 dB boost will require 4x the amplifier power and double the cone excursion.

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          • #6
            Why are you boosting low frequencies rather than decreasing higher frequencies; and are you considering the Fletcher Munson curve that describes our perceived loudness with regard to the frequency range you're designing for? https://ehomerecordingstudio.com/fletcher-munson-curve/

            Physical box design influences energetic efficiency. But you're trying to make your brain happy not the energy and air molecule gods. Or a microphone generating a frequency response graph, for that matter.

            I'm sticking my flag in the EQ camp. Use the box -- or no box -- to get you in the range where you can EQ your brain into a happy place.

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            • #7
              The drivers I find acceptable have enough xmax and power to accomplish the task.
              This is for a dual 15, 2 way project, so excursion is to be minimized, taking sealed woofers out of the equation, all the woofers I've entertained have equal or less than ~6mm excursion above port tuning (35hz or lower) at high spl, a strict requirement for limiting IMD.
              In particular with the high efficiency drivers, 4x 34 watts, for example, isn't a challenge, so once again, xmax and power handling hasn't been a limiting factor for the drivers I've chosen. I model the driver, and if it can't perform the task then, it is screened out.

              There are drivers with specs that I admire, the AE15m for example, that do not reach intended bass extension. A dual 15" config with said driver, has a F3 of ~52hz, port tuned to the 35hz. The speaker also has enough power handling and xmax to be eq'd flat to 30hz. I am trying to figure out would I rather take a driver like the Faital FH500 16ohm version, for example, which also has admirable specs but specifically, has an f3 in the low 30hz's as a better pick for the task vs the AE15m.

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              • #8
                I’d pick the AE everyday of the week. The AE drivers I heard in the Vapor audio speakers are the cleanest and quickest 15s I’ve heard.

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                • #9
                  Just to clarify, You'd rather take your preferred driver, and use eq to extend its low end to desired depth, vs using a your 2nd pic driver that naturally has the extension without eq, with an application that has final frequency response accuracy as its final destination. Meaning I intend to room eq the system flat to about 35hz, give or take a few, meaning that the AE is going to use up a couple more eq points vs the Faital pro..... If you are down...I'm down. The AE15m, modeled, is within XMAX specs at desired peak volume, and thats all I can ask for. Excursion is below 6mm peak to peak, above 35hz port tuning at peak volume. I'll never actually listen to them at peak volume =) so the system should perform un-strained at normal volumes.
                  I just sourced some JMLC horns from Germany at a very reasonable price, way under Auto-techs crazy shipping. I dunno how Shipping from Poland would be 10x the shipping from Germany....

                  Anyone looking for Tractrix/JMLC horns, check ebay.de The seller is hospitable and has experience, some 40 years worth of building horns.

                  So unless I can find a reason to not get the AE15M's my design is complete as far as driver selection goes.

                  Now I need to figure out how to create some enclosures that aren't just another pair of rectangles =|
                  Not sure if want vertical or horizontal woofer config.

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                  • #10
                    Yes, bass boast, or really a treble cut via DSP is nothing different than listening to bass heavy music. As long as you are inside of the better drivers happy zone it will still be the better driver. I run a ton of boost(18db at 20Hz) with my DEQX system to push my 4 10 inch tc sounds sealed subs in small boxes, and they sound very clean still. I’m trading headroom for extension, but they still play loud enough for the iluminator mids in my system to run out of steam before they do.

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                    • #11
                      The end result is still under the influence of the quality of filters and applied technique. No different than creating a passive crossover I guess. Filters are not exactly always(ever) transparent. For this reason certain principles are abided by for room correction eq higher than about 200hz. Another unique phenomena I've noticed is that when using eq for room correction in the bass region, in particular to correct a sharp null, the sound pressure level may be equalized to a balanced result, but the tactile feedback derived from the speaker working harder in that area of frequency, is offset from the rest of the frequency response and draws attention to itself. So even though the majority of potential issues of eq do not seem to be an issue with the voicing stage, it would of been foolish of me to just assume, rather than verify. Hence my skepticism. So thank you guys for your input!

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                      • #12
                        I don’t do any room correction, just speaker correction. A flat well designed speaker with good placement should not need any tweaking with EQ regardless of the measured response at the listening position. You will never EQ SBIR, or floor bounce out, and trying will leave a sloppy mess.

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                        • #13
                          Well I'm using room eq correction right now, and its improved clarity of the signal, especially in the absence of the optimum room acoustics. Using it to its best ability takes skill, just like anything else, theres a wrong way and a right way to do it. In a perfect world I'd just set my monitors up in the perfect acoustical space.

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                          • #14
                            Originally posted by camplo View Post
                            ...
                            Another unique phenomena I've noticed is that when using eq for room correction in the bass region, in particular to correct a sharp null, the sound pressure level may be equalized to a balanced result, but the tactile feedback derived from the speaker working harder in that area of frequency, is offset from the rest of the frequency response and draws attention to itself.
                            ...
                            You can't correct a sharp null with eq. Sharp low frequency nulls are caused by the interaction of the MLP, speaker placement, room size and lack of room treatment.

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                            • #15
                              IMHO the "natural" solution (without EQ) that provides the most extended response is best. Here's why:

                              First, we assume the driver is the same one in both cases.
                              If a more extended "natural" or un-EQ'd response can be had, this will be typically via a larger enclosure. Larger enclosures will have lower Q, which will lead to slightly better transient response. The enclosure volume can be stuffed with more stuffing and will absorb the backwave more effectively, which means less re-radiation through the cone. The enclosure walls must be braced sufficiently in order for them to not become an undesired secondary radiation source when they are excited by the backwave.
                              So far, so good.
                              What about EQing a smaller box to the response of a larger one?
                              Since the driver is the same, and I will assume a sealed enclosure, the excursion is NOT a limitation; it's just the same excursion limit as in the "larger enclosure" case, so no advantage or disadvantage.
                              EQing will mean boosting power, which will mean the power dissipated in the voice coil will be higher, which may mean that power compression might be of concern.
                              The larger problem I envision is that the EQ curve will likely be based on the small-signal, cold voice coil response of the driver, e.g. the Thiele-Small parameters that we all can measure. But as more power is applies the V.C heating will cause a drift in these parameters and sometimes this is not at all insignificant. So the EQ'd response is then not really correct, either. While the same phenomenon will happen in the "larger enclosure" case, it will be to a much lesser degree because there is no "extra" power being applied.
                              Finally, the smaller the box compared tot the total driver displacement the higher the distortion level. This was shown by Siegfried Linkwitz and there is a "closed box" Excel spreadsheet on his web site where you can calculate the effect.

                              The trend of larger drivers in a small box with low frequency EQ (thinking about subwoofers here mainly) is mostly out of convenience. It is definitely not moving in a more "high performance" direction.
                              Charlie's Audio Pages: http://audio.claub.net

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