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Thread: Differences between Rythmik FV15Hp and F25

  1. #21
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    Default Re: Differences between Rythmik FV15Hp and F25

    Quote Originally Posted by RythmikAudio View Post
    F25 has absolutely the least amount of phase shift or group delay (even though group delay is meaningful only for low pass filter). But it is large because it is a sealed design.

    FV15HP has all the characteristic of ported subs. It is more efficient and hence output more. Normal nonservo ported subs give us this boomy bass sound. Our servo ported subs greatly reduces that signature and gives us a bit of more "fully body" sound. The instructment may sound slight larger compared to the sound from F25. For anyone with HT application, we recommend FV15HP. For anyone with music as a higher priority, F25 is a better candidate. That does not mean F25 will be bad for movies. It is just that it has less coloration associated with other nonservo subs and can really "disappear" a bit better.
    Brian,

    I have a couple more questions:

    According to your measurements the FV15HP has a 1.5 dB advantage at 20 Hz over the F25, in terms of maximum output. Would you say that this is about the same from 15 Hz to 80 Hz, generally speaking, or does the FV15HP have a larger advantage over other frequency ranges?

    We can see the detailed measurements of the FV15HP on data-bass. It appears that the THD stayed well under control (basically under 10% from 30 to 35 Hz and up depending on one port or two port mode), even while it is pushed close to its output limit. We also see that the dominant component of the THD is the second harmonic from 80 Hz until about 28 Hz in both modes. Going lower in frequency, the 3rd order harmonic becomes the dominant component and rises rapidly. This is when the sub is pushed close to its output limits. It seems that this was likely by design, because when we get below 30 Hz we are less hearing the sound and more feeling it and the 3rd order harmonic in that range shouldn't stand out to us like it would at higher frequencies. People find the 2nd order harmonic distortion, less objectionable and some even find it pleasing. Was the F25 designed with a similar approach to the distortion curves, keeping THD under 10% until close to the output limits and the second order distortion being the dominant component from 28 to 30 Hz and up, except distortion being larger than the FV15HP from 40 Hz and below when the F25 is pushed close to its limits (due to the fact that it is a sealed design)?

  2. #22
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    Default Re: Differences between Rythmik FV15Hp and F25

    Quote Originally Posted by N Boros View Post
    According to your measurements the FV15HP has a 1.5 dB advantage at 20 Hz over the F25, in terms of maximum output. Would you say that this is about the same from 15 Hz to 80 Hz, generally speaking, or does the FV15HP have a larger advantage over other frequency ranges?
    I'm not Brian, but I can answer at least some of this.

    The greatest advantage of the FV15HP is at the tuning of the port. Above that, the advantage diminishes, and the F25 probably has an output advantage at some point.
    Last edited by curtis; 07-24-2015 at 12:56 PM.
    -curtis

  3. #23
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    Default Re: Differences between Rythmik FV15Hp and F25

    Quote Originally Posted by N Boros View Post
    Brian,

    I have a couple more questions:

    According to your measurements the FV15HP has a 1.5 dB advantage at 20 Hz over the F25, in terms of maximum output. Would you say that this is about the same from 15 Hz to 80 Hz, generally speaking, or does the FV15HP have a larger advantage over other frequency ranges?
    F25 actually has slightly more output above 50hz. But as you know the lowest output point of any sub is at the lowest frequency and I really think at subwoofer should at least reach 20hz and that is why we use 20hz as the reference point. Very often you will expect the sealed sub to have output when frequency increase from 20hz to 40hz, more so than a vented counterpart.



    We can see the detailed measurements of the FV15HP on data-bass. It appears that the THD stayed well under control (basically under 10% from 30 to 35 Hz and up depending on one port or two port mode), even while it is pushed close to its output limit. We also see that the dominant component of the THD is the second harmonic from 80 Hz until about 28 Hz in both modes. Going lower in frequency, the 3rd order harmonic becomes the dominant component and rises rapidly. This is when the sub is pushed close to its output limits. It seems that this was likely by design, because when we get below 30 Hz we are less hearing the sound and more feeling it and the 3rd order harmonic in that range shouldn't stand out to us like it would at higher frequencies. People find the 2nd order harmonic distortion, less objectionable and some even find it pleasing. Was the F25 designed with a similar approach to the distortion curves, keeping THD under 10% until close to the output limits and the second order distortion being the dominant component from 28 to 30 Hz and up, except distortion being larger than the FV15HP from 40 Hz and below when the F25 is pushed close to its limits (due to the fact that it is a sealed design)?
    You have been correctly pointing out the 3rd order harmonic distortion is due to the fact output is approaching its limit. In fact, it can be proven that a symmetric transfer function with F(-x)=-F(x), there is no even order harmonic distortion. So F(-x)=-F(x) meaning they are symmetric around orign point (x=0). It is largely true when the signal is large that when it approach limit, the characteritic is more similar. Among all odd order harmonic distortoin, 3rd order is the lowest one. So ideally we hope all odd order harmonic distortion will be mainly 3rd order. The 5th and above should be kept minimal.

    As we talk about odd order harmonics which are caused by symmetric F(x) and F(-x) curve, we can imagine all even order harmonics should be caused by F(-x)!=-F(x). Sometimes you can interpret this as the curve has a bit offset at the origin point. This is almost inevitable, in particular at small signal level of speakers. Again what is important is keep 4th order harmonic distortion and above minimal.

    Servo helps to keep higher order harmonic distortion reduced in level and what we should really see is mainly either 2nd order or 3rd order harmonic distortion.
    Last edited by RythmikAudio; 07-27-2015 at 10:54 PM.

  4. #24
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    Default Re: Differences between Rythmik FV15Hp and F25

    Quote Originally Posted by RythmikAudio View Post
    F25 has absolutely the least amount of phase shift or group delay (even though group delay is meaningful only for low pass filter). But it is large because it is a sealed design.

    FV15HP has all the characteristic of ported subs. It is more efficient and hence output more. Normal nonservo ported subs give us this boomy bass sound. Our servo ported subs greatly reduces that signature and gives us a bit of more "fully body" sound. The instructment may sound slight larger compared to the sound from F25. For anyone with HT application, we recommend FV15HP. For anyone with music as a higher priority, F25 is a better candidate. That does not mean F25 will be bad for movies. It is just that it has less coloration associated with other nonservo subs and can really "disappear" a bit better.

    I think this and everything else you mentioned is finally helping me understand why you suggest the FV15HP with HT as the main priority and the F25 with music as the main priority.

    I plan to have a pair of subs to help even out the seat to seat variation. So as long as I can integrate them well, either sub should disappear well regardless of if I go with a pair of F25s or a pair of FV15HPs. But, the F25 has the advantage of having faster transient response. This should likely give (as you say) the ability for the sub(s) to disappear more, but also perhaps wring out a slight bit more detail here and there. Both of these characteristics are big priorities for music. One Downside is that the F25 (since it is sealed) will have more distortion, as it is pushed hard below 40 Hz. This isn't important for music applications, since people will rarely listen to music at the same demanding level as for HT. So the F25 won't likely get into the larger distortion with music, as much, if at all. The other slight downsides are the larger size, larger weight and larger price.

    The FV15HP has the advantage of having more output from 50 Hz and below, at lower distortion (at same SPL level when the FV15Hp and F25 are pushed harder). Many movies have quite a bit of content below 50 Hz. Many people enjoy the ability for the subwoofer to give a "gut punch", when a large peak at around 40 Hz occurs and the you get the rapid punch from the sub that you can feel in your chest, when the sound in the movie calls for it. Having a sub that can have more clean output is a priority for home theater, when for example, there can be 115 dB peaks in LFE channel, when the volume is set to reference level of 85 dB. While the F25 may have faster transient response, some may actually prefer the "fuller" sound on movie soundtracks. In comparison, the FV15Hp is slightly smaller in size, slightly smaller in weight and slightly cheaper.

    I guess, I'm starting to understand that there is not really a better (in terms of accuracy) subwoofer between the two in general, but it really depends on the application. The faster transient response comes with a price, of less output and higher distortion over the lower half of the frequencies (roughly). The only way we could avoid this is if we were able to buy several F25s to ensure that we have clean output levels needed for the application. In this case, if two FV15HPs would give the clean levels of output, it might take 4 F25s to match the output, while keeping the distortion to the same threshold as the FV15HPs below 40 Hz.
    Last edited by N Boros; 12-10-2016 at 09:44 AM.

  5. #25
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    Default Re: Differences between Rythmik FV15Hp and F25

    If I were contemplating that much output, I would much rather pay the extra cash for two F12's or F15's so I can place them in the room appropriately rather than having a solitary high output F25. Placement is key with bass. If you're pairing them with Sierra-2's, I have to assume you're not trying to fill a huge room.

  6. #26
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    Default Re: Differences between Rythmik FV15Hp and F25

    Quote Originally Posted by bkdc View Post
    If I were contemplating that much output, I would much rather pay the extra cash for two F12's or F15's so I can place them in the room appropriately rather than having a solitary high output F25. Placement is key with bass. If you're pairing them with Sierra-2's, I have to assume you're not trying to fill a huge room.
    You have a very good point, but I have a somewhat odd setup. I have a large open finished basement. Part of my basement I am using as my home theater area. Although it is quite a large open space (about 6500 cubic feet), my home theater area is in a corner of that and I have the Sierra 2s and surround speakers pretty close to my couch. I am probably about 8 feet away, roughly from each speaker. So the smaller bookshelf speakers give me more than enough output how I have them setup right now.

    However, I currently have an Outlaw LFM1 subwoofer, that I am using, that was originally purchased for a much smaller room at a previous house. It is way too small to pressurize this large of a space. I have it placed quite close to a corner to help a bit with output, but it is still lacking until I can get a couple of serious subs. I was thinking either a pair of FV15HPs or a pair of F25s would be necessary to pressurize, the space. One would probably be fine, but I want to have good bass at more than one seat, so I plan to get a pair to get more uniform seat to seat variation.


    By the way, my listening space is actually closer to about 10,000 cubic feet, until I actually put up wall and doorway to make the room a more manageable size (of about 6500 cubic feet). Right now my Outlaw sub is seriously lacking the impact I would like, when one actually pressurizes the room with it.

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