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  Topic Review (Newest First)
04-18-13 04:50 PM
Re: Rythmik Audio/GR Research F12G Direct Servo Subwoofer

Photo of our Rythmik F15HP in the office.....might seem a little strange, sub is sitting on top of two bass traps (with pair of Chris Pelonis speakers on either side).....we do a lot of measuring and testing here in the office, and there was simply no other place to put the traps when we got them in....interestingly, the sub works well in that location and with some other traps around a pretty much square room, the low end response is very good.
04-18-13 04:40 PM
Re: Rythmik Audio/GR Research F12G Direct Servo Subwoofer

Excellent review. I have a Rythmik F15HP and have also used several of them in studio setups we specify. All happy clients. I've worked with a lot of subs and the Rythmik line is at the top. Add in "value" at the price point and there's almost no other choice in this price range and performance.
04-17-13 05:13 PM
Re: Rythmik Audio/GR Research F12G Direct Servo Subwoofer

Sonnie wrote: View Post
Excellent work Erin... very detailed and informative.

Maybe we should make it a prerequisite that all reviewers have a Klippel system.
We are very fortunate to have one with the capability to measure and skill to interpret the data.

Good work, Erin!
04-12-13 10:58 AM
Erin H That would be quite a task. Lol.
04-12-13 09:22 AM
Re: Rythmik Audio/GR Research F12G Direct Servo Subwoofer

Excellent work Erin... very detailed and informative.

Maybe we should make it a prerequisite that all reviewers have a Klippel system.
04-12-13 08:53 AM
Erin H Keep in mind, if you want to save money you can buy the sub and amp separately and build your own enclosure.
04-12-13 12:35 AM
Re: Rythmik Audio/GR Research F12G Direct Servo Subwoofer

Thanks for the thorough testing and evaluation.
This Rythmik sub is excellent and only a small 1.5sq. ft. box, heavy but small.
It's price is significant but not the most expensive
04-11-13 11:10 PM
Erin H
Re: Rythmik F12G Direct Servo Subwoofer


  • Low distortion subwoofer driver with nearly 18mm one-way linear excursion
  • Sturdy and very robustly built enclosure that shows no real signs of audible panel ringing
  • Excellent features allowing the user to tailor the response to his room and tastes and achieve response below 20hz if so desired
    • Low frequency extension settings
    • Damping of low frequency extension
    • Low pass filter options
    • Parametric EQ (a very nice added bonus)
    • Phase adjustment is an absolute treat

All in all, a very solid product with focus on not only quality but, most importantly, providing the user with the ability to tailor the sound to what works best for them.
04-11-13 11:09 PM
Erin H
Re: Rythmik F12G Direct Servo Subwoofer

In-Room Use

I truly believe the most important factor in a great sounding system is smooth response. That's pretty much a de facto standard. However, the next important item on my list is good, clean bass response. When bass is bloated and fat, plagued by improper phase alignment and modal issues, everything above it gets covered up. If you strive for detail and articulation in music or theater, you have to focus on the low end response and working to get it to sync well with the rest of your system in time and amplitude. This is why I was very happy to see the plethora of settings available on the F12G. I've covered most of these settings in the post above but it is worth looking at the real world application of a certain few. Below I have illustrated the Phase Delay setting as well as practical use of the Parametric EQ.

To perform these tests, I placed my test microphone approximately 2 meters from the speakers. The sub was placed on the floor between my pair of Kef Q100 bookshelf speakers and the volume was set to a typical listening level at 10pm.

Phase Delay:

Most subwoofers have a polarity switch that will reverse the signal so it can be better aligned with your speakers. This is not a trivial topic and much goes in to getting this dialed in just right. When you factor in the effect of the environment, typically due to placement, it becomes even harder to properly align the wavefront of the subwoofer to that of the other speakers in the room. While the 0/180 degree polarity switch on most amps helps somewhat, it leaves a wide range of potentially better fitting phase adjustments on the table. The F12G subwoofer picks up the slack where most other subwoofers leave off. The F12G permits the user the ability to fine tune the phase of the subwoofer so it can be closely matched to your other speakers. You can set the phase as 0 or 180, of course. However, the key feature here is you can also set the phase to any number between these two points. If you want to adjust the phase angle so it is 22 degrees, you can. Every system is different, so time and care should be taken to determine where this dial should be placed for your own system. As an example, I have highlighted the measured difference at 0, 90, and 180 degrees.

As you can see, each setting results in a different measured response. One might look at the 180 degree result and say it's the most "in phase" with my Q100's because it has the most amplitude. However, one thing to keep in mind is the fact there are always tradeoffs in home audio. In this case, I'd say the 90 degree measurement may be better because it still has close to the same amplitude as the 180 degree measurement. However, it doesn't have the bump at approximately 56hz like 180 degrees does. This may be a way to get the best of both worlds: modal control and phase alignment. Of course, as I said above, every room is different and since bass is so dominated by the room the listener will have to decide what works best in their room. Who knows, there may be a phase angle between the (3) I've displayed that provides a smoother response.

Parametric Equalizer:

As I noted above, there's an apparent modal issue at 56hz. The only real way to know for sure is to measure at different spots in the room, and perform decay (waterfall) measurements. Compare these to your frequency response and you'll get a good idea of what's a modal issue and what is not. Also, be careful not to confuse a peak in response with modal ringing in the room simply because of a peak. A dip in response can often fool you in to focusing on the peak next to it, rather than realizing the null itself is the real problem. (side note: it's not wise to try to boost a null with EQ as often this is a cancellation that cannot be corrected via EQ)

Since I had frequency response measurements already, I performed decay analysis and found 56hz is indeed a lingering note in my room.

Since the modal issue has been verified, let's use the amplifier's built in parametric EQ to see if we can knock this down a bit and clean up the low end response.

As you can see from the above, the center frequency was placed at approximately 56hz, a narrow Q was set, and the level of EQ applied was -12dB. What does the decay look like now?

The ringing was decreased by roughly 50ms which helped to clear up the bloat occurring in the low frequency response.

When used properly, this kind of feature can do a lot to improve the clarity of your sound system.
04-11-13 11:09 PM
Erin H
Re: Rythmik F12G Direct Servo Subwoofer

F12G Subwoofer Testing

Thanks to its patented Direct Servo System, the F12G has numerous settings which allow the end user to tailor the sound to their own tastes or to blend better in their own setup. These settings can be found in detail on Rythmik's site here. In a nutshell, however, you are able to choose how low you want the response to extend and how the low end response will be shaped, parametric EQ capability, and a "rumble filter". I find these features very useful. However, simply knowing they are available isn't quite enough. I am a visual learner so I wanted to share the measurements I obtained. Here are close ups of the amplifier's settings:

  • All the following tests were done with the amplifier's crossover set wide open to 120hz/12dB.
  • I did not test the crossover settings as crossovers are a well understood idea.

Low Frequency Extension and Damping (Q) adjustments:

As shown above, you have (3) frequencies you can choose from: 14hz, 20hz, and 28hz.
You also are able to choose from (3) different damping (Q) methods: low, mid, or high.

First, the damping switches. I set the extension frequency to 14hz and measured the response as I adjusted the Q from low, to mid, and to high. Here are the comparison results:

Next, I fixed the Q and altered between the (3) extension frequencies:

Parametric EQ:

Another feature of the F12G is the amplifier's parametric EQ. This feature is very useful to help adjust for the in-room response (ie: to tame a modal issue). The user is allowed to set the center frequency anywhere between 20hz to 80hz and an associated bandwidth. The bandwidth, or Q, dictates how wide or narrow the cut is. "Minimum" would be a narrow adjustment and "maximum" would be a very wide adjustment. The level of cut or boost is between -12dB to +3dB. Below are some examples of the various settings, compared to a 'baseline' frequency response to illustrate the adjustments' effect.

+3dB Setting:

-12dB Setting:

Rumble Filter:

The F12G also comes with a rumble filter switch which helps to limit cone excursion if so desired. The picture below compares the response with a Mid Q, extension frequency at 20hz setting and filter on vs filter off.

Phase Adjustments:

Please see the below "In-Room Use" section for discussion on this feature.

Enclosure Resonance:

One test I like to see on loudspeakers and subwoofers is an accelerometer test. So, I wanted to present that here.

I measured the subwoofer's response and normalized the SPL to 1m, giving about 92dB at 1m (referencing 50hz) using the measurement mic. The dashed lines represent the accelerometer response with the accelerometer placed at the side and then at the top of the enclosure. Comparing the two indicates a modal ringing around 310hz which is also verified by the CSD plot. Though, comparing to the frequency response of the subwoofer, there is no indication in this showing up. Furthermore, phase measurements don't indicate a strong correlation between measured acoustic response vs structural response. So, while there is modal ringing measured, there's no real indication this will be an audible detriment.

I lost my calibration sheet for my accelerometer so the level at which the accelerometer results are given below are not absolute.

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