Differences between Rythmik FV15Hp and F25

[N Boros]

I know that in general the transient response of sealed subs are supposed to be better than that of ported subs and ported subs are supposed to have quite a bit more output at the lower end. But the output seems very similar between the FV15Hp and the F25 and the F25 should have better transient response than the FV15HP. According to the Rythmik website:

"Output comparison

At 20 Hz, our subs vary in their maximum output capability. The output at 20 Hz is shown relative to F12.

F12: 0db (baseline)
F15: +2db D15: +2db
LV12R: +2.5db
E15HP: + 3.5db
F15HP: +4db
FV15: +7db
FV15HP: +9.5db
F25: +8db"

So the FV15HP has a slight advantage of output at 20Hz. However, since the F25 is sealed it should roll off more gradually, so below 20Hz output should be higher on the F25. If the differences in output are only slight, will I hear much of a difference between the two with music? What about with movies? If a sealed sub has the same output capability as a similarly priced ported sub, wouldn't the sealed sub be the better of the two?

I compared my new Sierra 2s with other similarly priced speakers exhibiting flat frequency response on axis as well as quite far off axis. I could immediately hear the difference between the Sierra 2s and the other speakers and I attribute this mostly to the faster transient response of the ribbon tweeter in the Sierra 2s. A better comparison is the folks that have upgraded the Sierra 1 to the Sierra 2 and preferred the difference in sound quality for almost double the price. I wonder if the same will hold true in the below 80 Hz region with subwoofers?

[RicardoJoa]

With music, i would be more concern with the higher frequencies rather then the lowest, in which based on the discription of the f25, has more power than the FV15.
It will be most likely hard to hear the difference as frequencies below 20hz are rather sensational.

[N Boros]

With music, i would be more concern with the higher frequencies rather then the lowest, in which based on the discription of the f25, has more power than the FV15.
It will be most likely hard to hear the difference as frequencies below 20hz are rather sensational.

I guess the reason I was bringing up lower frequencies, is that sealed subwoofers will have the most difficult time getting the same output at 20 Hz in comparison to a ported sub in the same price class. So if the F25 and FV15HP have nearly the same output at 20 Hz then we could expect the same to be true up to around 40 or 50 Hz, where the F25 probably has a little bit more output than the FV15HP, as you mention. So the FV15HP has a slight advantage below 40Hz and the F25 has a slight advantage above 40Hz.

My concern is more with respect to home theater, as the F25 would likely have the advantage for music. If the frequency response is quite similar between the two, and I am okay with the size of the F25 and slightly higher price, then which of the two would have the advantage for home theater? Also, will I be able to hear faster transient response of the F25 and is this something more desirable for home theater use? I cannot see why a main speaker with faster transient response wouldn't be more desirable for home theater or music use, but there seems to be some who prefer the sound of ported subs for home theater use.

[RicardoJoa]

I guess the reason I was bringing up lower frequencies, is that sealed subwoofers will have the most difficult time getting the same output at 20 Hz in comparison to a ported sub in the same price class. So if the F25 and FV15HP have nearly the same output at 20 Hz then we could expect the same to be true up to around 40 or 50 Hz, where the F25 probably has a little bit more output than the FV15HP, as you mention. So the FV15HP has a slight advantage below 40Hz and the F25 has a slight advantage above 40Hz.

My concern is more with respect to home theater, as the F25 would likely have the advantage for music. If the frequency response is quite similar between the two, and I am okay with the size of the F25 and slightly higher price, then which of the two would have the advantage for home theater? Also, will I be able to hear faster transient response of the F25 and is this something more desirable for home theater use? I cannot see why a main speaker with faster transient response wouldn't be more desirable for home theater or music use, but there seems to be some who prefer the sound of ported subs for home theater use.

I cant say which to which as i dont own either ones. I own a F15 and im compleaty happy with it.
But you can take a look at the sealed version FR and i would assume that the F25 would have similar FR.
If you look at the ported version, the FR is faltter.


Shoot Brian your concerns,

[Audiolover458]

I am interested in the same thing. I am surprised though at the lack of interest in this thread :-).
Would love to know the answer and I did email Rythmik today so let us see if they answer. Maybe I can drive to Austin and find out for myself.

[Sivar]

I haven't heard the F15HP (or almost any subs in this class), but I got the F25 because it is sealed, has only slightly lower output around 20Hz and (I assume since it is sealed) higher output above and below that range, and was only a little more expensive.

I see it as this: If the huge size and slightly higher cost aren't an issue, why not get the sealed model? Other than low output, which isn't much of an issue in this case, I haven't heard any benefit of ported subs but have heard of many benefits of sealed.
As an aside, the F25s are tall enough to use as an end table, though you'll want to protect the finish.

[N Boros]

I know that in general the transient response of sealed subs are supposed to be better than that of ported subs and ported subs are supposed to have quite a bit more output at the lower end. But the output seems very similar between the FV15Hp and the F25 and the F25 should have better transient response than the FV15HP. According to the Rythmik website:

"Output comparison

At 20 Hz, our subs vary in their maximum output capability. The output at 20 Hz is shown relative to F12.

F12: 0db (baseline)
F15: +2db D15: +2db
LV12R: +2.5db
E15HP: + 3.5db
F15HP: +4db
FV15: +7db
FV15HP: +9.5db
F25: +8db"

So the FV15HP has a slight advantage of output at 20Hz. However, since the F25 is sealed it should roll off more gradually, so below 20Hz output should be higher on the F25. If the differences in output are only slight, will I hear much of a difference between the two with music? What about with movies? If a sealed sub has the same output capability as a similarly priced ported sub, wouldn't the sealed sub be the better of the two?

I compared my new Sierra 2s with other similarly priced speakers exhibiting flat frequency response on axis as well as quite far off axis. I could immediately hear the difference between the Sierra 2s and the other speakers and I attribute this mostly to the faster transient response of the ribbon tweeter in the Sierra 2s. A better comparison is the folks that have upgraded the Sierra 1 to the Sierra 2 and preferred the difference in sound quality for almost double the price. I wonder if the same will hold true in the below 80 Hz region with subwoofers?

With music, i would be more concern with the higher frequencies rather then the lowest, in which based on the discription of the f25, has more power than the FV15.
It will be most likely hard to hear the difference as frequencies below 20hz are rather sensational.

I guess the reason I was bringing up lower frequencies, is that sealed subwoofers will have the most difficult time getting the same output at 20 Hz in comparison to a ported sub in the same price class. So if the F25 and FV15HP have nearly the same output at 20 Hz then we could expect the same to be true up to around 40 or 50 Hz, where the F25 probably has a little bit more output than the FV15HP, as you mention. So the FV15HP has a slight advantage below 40Hz and the F25 has a slight advantage above 40Hz.

My concern is more with respect to home theater, as the F25 would likely have the advantage for music. If the frequency response is quite similar between the two, and I am okay with the size of the F25 and slightly higher price, then which of the two would have the advantage for home theater? Also, will I be able to hear faster transient response of the F25 and is this something more desirable for home theater use? I cannot see why a main speaker with faster transient response wouldn't be more desirable for home theater or music use, but there seems to be some who prefer the sound of ported subs for home theater use.

Brian,

Since you are here would you be able to enlighten us with the differences between the F25 and the FV15hp? Nobody was really able to answer the original thread questions.

[RythmikAudio]

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.

[N Boros]

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)?

[curtis]

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.