Rythmik L12 Subwoofer Review

[Frank Dernie]

Where is all that extra weight coming from?

Cabinet, driver "motor" and amplifier.
Super high quality drivers have hugely heavy motors and a big solid cabinet is not light!.
My REL Studio which has 2 10" Volt drivers weighs over 200lbs. It has been moved once since I got it and it won't be again!

 

[hardisj]

FWIW, I reviewed the Rythmik FG12 in 2013. I did a full analysis of the drive unit itself as well as the loaded enclosure and all the amp's various features/settings. It was quite an extensive review, taking me about 2 days' time to go through all the various settings of the amplifier as well as the 'raw' drive unit performance.

Anyway, it might be fun to compare this guy against that one...

https://www.erinsaudiocorner.com/loudspeakers/rythmik-f12g-direct-servo-subwoofer/

It's a lengthy read but I think there's a lot of valuable information, if I say so myself. But here's a few nuggets since I know most won't bother to go there...

From the above, using the prescribed Bl, Cms, and Zmax (Le(x)) values for linear excursion limits, the driver’s linear Xmax measures at 17.8mm, limited by Bl. That’s quite impressive.

Loaded suboowfer/enclosure test results sample

Cabinet resonance testing:

Variable Phase Example in-room use:

 

[Frank Dernie]

It seems subwoofer has spawned a second meaning since the arrival of inexpensive home theatre.
A couple of decades ago it would have literally been for sub-bass, mine crosses over to the main speakers at 22Hz and just extends the bass down to full level at ~18Hz and increases the maximum bass volume a fair bit.
Nowadays there are boxes with 8" units in which go nowhere near as low as my main speakers, or as loud, described as subwoofers but really intended to add a bit of normal bass to teensy home theatre speakers.

 

[Hidde]

No and no.

The amplifiers are sourced from a manufacturer and then a daughter card added to implement the servo within the existing circuitry. The transducer has a small voltage feedback coil to provide the servo input, and there is also a small value resistor in series with the woofers driven coil (which is monitored across) to provide another input to the servo.

Brian Ding considers the specifics of all this proprietary. Suffice it to say, there's nothing fancy going on here at all. The concept is ages old.

Dave.

You can make any amplifier a transconductance amplifier (current drive). This CAN be done (there are multiple ways) by a sensing resistor in series with the actuator, in this case the woofer.

Shame they don't use accelerometers and an analog controller. Secondary windings on the woofer suffer severly from magnetic coupling of the woofer. On the otherhand I can understand, because good accelerometers are expensive (for instance the ACH-01 is about 50$ alone!). Though Rythmik has probably found that a sense coil is relatively cheap performance gain compared to no feedback at all.

 

[Bhh]

Nowadays there are boxes with 8" units in which go nowhere near as low as my main speakers, or as loud, described as subwoofers but really intended to add a bit of normal bass to teensy home theatre speakers.

One Two words, Bose Accoustimass. Forever changed WAF and what we can get away with in their living rooms as well. My dad’s 20+ year old set in his garage still get brought up in “debates” about what we “should” have.

 

[Deleted member 2944]

You can make any amplifier a transconductance amplifier (current drive). This CAN be done (there are multiple ways) by a sensing resistor in series with the actuator, in this case the woofer.

Shame they don't use accelerometers and an analog controller. Secondary windings on the woofer suffer severly from magnetic coupling of the woofer. On the otherhand I can understand, because good accelerometers are expensive (for instance the ACH-01 is about 50$ alone!). Though Rythmik has probably found that a sense coil is relatively cheap performance gain compared to no feedback at all.

A small value series/sensing resistor doesn't make the amplifier current-drive. From what I gleaned from Brian Ding's vague explanation regarding this, the series resistor used is only 0.1 ohms.

The amplifiers used by Rythmik here are voltage sources.

Dave.

 

[GD Fan]

I believe Amir had more thorough battery of tests planned but unfortunately I need the sub returned soon as the home audition/return window is closing and I‘d like to test at home and return or pick up a second one before any more supply chain disruptions if this first one works out.

Everyone can direct their complaints about insufficient tests at me.

Thanks for sending it in for review - I've been considering this one myself.

 

[thefsb]

Now I'd like to see the cheap Dayton 12".

 

[MZKM]

Now I'd like to see the cheap Dayton 12".

Yeah, and compared to the BIC F12, as they are my go-to recommendations on a budget (and the 15” Dayton).

 

[jhaider]

To be useful a sub needs to have little to no output above its operating range, otherwise it starts to cause problems with localisation - that is you can localise it.

Unlike the rest of your post, I disagree with this statement. Ideally any drive unit will have flattish and smooth response above and below its passband. A subwoofer should be flat smooth and clean at least an octave above its intended range. I like to use subwoofers higher than standard to gain headroom and extend the response smoothing benefits of spatial distribution. That means flattish and smooth FR out to 300+ Hz.

Also, bass management should be centralized, not ad hoc cast out to individual components. Decentralization just makes it harder to optimize the system response. If a subwoofer amp has a low [corrected] pass, it must be defeatable for the subwoofer to be generally usable.

I consider this subwoofer and the one Erin measured borderline unusable due to the limited bandwidth imposed by very poor design choices.

 

[MetalheadRich]

Unlike the rest of your post, I disagree with this statement. Ideally any drive unit will have flattish and smooth response above and below its passband. A subwoofer should be flat smooth and clean at least an octave above its intended range. I like to use subwoofers higher than standard to gain headroom and extend the response smoothing benefits of spatial distribution. That means flattish and smooth FR out to 300+ Hz.

Also, bass management should be centralized, not ad hoc cast out to individual components. Decentralization just makes it harder to optimize the system response. If a subwoofer amp has a high pass, it must be defeatable for the subwoofer to be generally usable.

I consider this subwoofer and the one Erin measured borderline unusable due to the limited bandwidth imposed by very poor design choices.

"Poor design choices" according to you. Proper design choices to the rest of us.

 

[jhaider]

"Poor design choices" according to you. Proper design choices to the rest of us.

Do you have a substantive critique to my post or are you just being doltishly contrarian for the hell of it?

Please explain how you imagine confederating (as opposed to centralizing) bass management makes the optimization task easier.

Here, the unfortunate part is that except for the stupid design choice of a non-defeatable lowpass [corrected] the thing seems otherwise good enough.

(Yes, I realized I poked a wasp nest here. This is one of those firms with a large hive of internet drones ready to sting anyone who dissents from their hive mind.)

 

[Thomas savage]

"Poor design choices" according to you. Proper design choices to the rest of us.

Well a debate is what we are here for, hopefully a constructive one .

 

[Prana Ferox]

The big "did I get what I paid for" metric for DACs, amps etc is SINAD within audible band.

For full-range speakers the big one is frequency response / deviation. ASR focuses on dispersion / spinorama.

For subs it's LF extension and max SPL. FR is largely expected to be bludgeoned into shape with DSP, and some subs (horns) have quite bad FR 'out of the box'. Max SPL tells you how many subs you need to keep up with your mains, noting many run their sub channels deliberately hot. LF extension is frequently fibbed.

Testing a big subwoofer for max SPL in your garage will get old for you, your belongings and house structure, and your neighbors pretty quick.
RE room gain, in real life it obviously matters but it is 100% dependent on factors the subwoofer designer cannot control.

 

[Prana Ferox]

It seems subwoofer has spawned a second meaning since the arrival of inexpensive home theatre.
A couple of decades ago it would have literally been for sub-bass, mine crosses over to the main speakers at 22Hz and just extends the bass down to full level at ~18Hz and increases the maximum bass volume a fair bit.
Nowadays there are boxes with 8" units in which go nowhere near as low as my main speakers, or as loud, described as subwoofers but really intended to add a bit of normal bass to teensy home theatre speakers.

The units you're referring to for sub-bass, are generally referred to as LFE (low frequency effects) subs. Very little music has content that far down but many movies do. Below a certain point these usually transition to a bass shaker directly conducting to the listening area seats or floor.

Subs can have 8" or smaller drivers and still be real, it's just a matter of how big you want the passband to be and what SPL to maintain across it.

Please explain how you imagine confederating (as opposed to centralizing) bass management makes the optimization task easier.

Here, the unfortunate part is that except for the stupid design choice of a non-defeatable highpass, the thing seems otherwise good enough.

I assume you mean non-defeatable lowpass. Keep in mind most of the plate amp subs out there were designed years ago and assume a minimally sophisticated AVR providing .1 signal, if the sub isn't doing 100% of the crossover. This sub would work reasonably well as sold, plugged into an old receiver and never optimized. Centralized, sophisticated bass management is still uncommon in the AV world and even more niche in 2-channel.

Also, you may call it a sub but if you're above the point of localization (certainly at 300hz) you're in mid-bass module / kick bin territory.

 

[mitchco]

Love those Rythmik subs! Like @Ron Texas I have a pair of L12's and LS50's mains, sound great. Like @Olli I have a pair of F18's with my JBL 4722's:

I cross the subs at 46 Hz, between room modes. Seamless integration using digital XO and room correction. My measurement mic is calibrated to 5 Hz. Using REW's default window of 500ms with no smoothing:

I am also a fan of time aligning drivers to get as best step (transient) response as possible:

5Hz to 24 kHz sweep at the LP. The Rythmik subs go very deep, as they should. You know, subs are supposed to "sub"

The F18's are 900 watts aside and the JBL cabs with the dual 15" gets 575 watts a side, so just shy of about 3000 watts of power for 630 Hz and below. They sound super tight and deep, with no overhang and huge transient punch. Lots of fun for music and movies.

 

[BurgerCheese]

Also, bass management should be centralized, not ad hoc cast out to individual components. Decentralization just makes it harder to optimize the system response. If a subwoofer amp has a high pass, it must be defeatable for the subwoofer to be generally usable.

I consider this subwoofer and the one Erin measured borderline unusable due to the limited bandwidth imposed by very poor design choices.

I agree that bass management should be centralized if possible, and that the high pass filter should be defeatable. But to call it "borderline unusable" is not very constructive. It might be borderline unusable for you, but for most others it will probably be "fine".

Personally I wouldn't want a puny 12" subwoofer (or multiple for that matter) in the first place. But others might, and this seems like one of the better ones, although with some minor flaws.

 

[jhaider]

I assume you mean non-defeatable lowpass.

Yes, thanks. Will correct.

Keep in mind most of the plate amp subs out there were designed years ago and assume a minimally sophisticated AVR providing .1 signal, if the sub isn't doing 100% of the crossover.

That was bad design years ago, too.

Also, you may call it a sub but if you're above the point of localization (certainly at 300hz) you're in mid-bass module / kick bin territory.

That is my expectation for the bass subsystem (implying global low pass at or below 150Hz for a multiple sub system that will itself likely be optimized with additional low pass filters on a sub by sub basis) not the bandwidth used. Any good sub driver can do that bandwidth.

 

[Frank Dernie]

The units you're referring to for sub-bass, are generally referred to as LFE (low frequency effects) subs.

Well I am old and they were originally referred to as subwoofers because they were dedicated to reproducing sub-bass.
Now they are used because so many speakers can't reproduce the bottom couple of octaves so are strictly separate woofers IMHO.
Not that that is necessarily a bad thing but a "sub" which doesn't go down to 20Hz is hardly a "SUB" as far as I am concerned. I have organ recordings with 16Hz in them which I can feel using my sub.
I do realise that most music is between 32Hz and 7kHz though.
Film sound effects are admittedly the main function of a sub for most people, organ music is scarcely typical music.

 

[Ron Texas]

Lowpass on Rythmik subs is defeated by using LFE input. On the Rythmik site they say subs in general should not be crossed over higher than 120 hz even if the lowpass filter on the sub allows it. I would also mention the higher the crossover frequency, the greater the need for time alignment as the wavelength gets short enough to be large compared to any delay in the Sub.

Does it bother anyone around here that some members quote your post for the sole purpose of disagreeing? Can't they just state their opinion without being a PITA?