Extraordinary claims made about Rythmik Subwoofer !!

[snoopy]

Originally posted by seanzozo


I hate to get back into it, but at the time the marketing for rhythmik's website was written (years ago - and because it is one guy the site changes little) the 12" was available in a vented format. A vented 12" tuned to 20hz would use 1/5 the power and ~1/10 the excursion at 20hz and would likely hit 100db 1m with a ground plane at low distortion.

Fair enough Sean. Maybe he just needs to be a bit more careful in his wording or maybe he needs to provide some actual measurements of a typical system so people don't get the wrong idea

If you look at all of the tests done on the hometheatreshack forum there are not a lot of subwoofers that make the grade as far as low distortion is concerned

http://www.hometheatershack.com/foru...rer-model.html

[seanzozo]

Originally posted by snoopy


If you look at all of the tests done on the hometheatreshack forum there are not a lot of subwoofers that make the grade as far as low distortion is concerned

http://www.hometheatershack.com/foru...rer-model.html

You'll get no disagreement from me there

[Cloth Ears]

Originally posted by seanzozo
You'll get no disagreement from me there

Nor me !

[bossobass]

IMO, the 30 second reverse sine sweeps done progressively higher in 5dB increments is nothing more than a torture test. In no way does a test like this represent actual use with music program.

These tests are good only as a comparison to other tests done by the same tester, and, as he himself has told me, they even vary by ambient temperature according to what time of year he conducted them, so they can't even be compared to each other in some respects.

If you look at his CEA 2010 results, the Rythmik 12 is the highest rated 12" sealed sub he has tested to date by clean RMS output.

Its results put it neck and neck with the twice as large SVS 12" ported 20-39 cylinder sub (in 12Hz tune, the only tune with clean output that low), a truly remarkable achievement, as anyone who has ever built a 12" sealed subwoofer with a 350 watt power plant would know.

As was mentioned, the variable F3 and system Q make this little sub very versatile and the election to forego the use of limiters allows for the severe abuse it was subjected to in the test that resulted in the THD sweep posted above.

The youngster who conducts the tests and his avid fans tend to be young fellows who often engage in SPL race discussions, whereas the designer of the Rythmik 12" kit is a nuance designer who has a better grasp on the theories and mechanics of such a subwoofer than just about anyone I've met. He looks to a result of quality listening through a versatile machine, which his kit delivers in spades.

If quality and versatility are the primary concern, Brian's servo kits will fit the bill and live up to all of his claims. If dBSPL is what matters, build more than 1 kit, or move up to multiples of his 15" kit and have both bases covered (as was suggested).

Brian Ding is a first rate gentleman and an excellent engineer. His stuff is well worth the $$ and does exactly what he says it will.

Bosso

[snoopy]

Originally posted by bossobass

Brian Ding is a first rate gentleman and an excellent engineer. His stuff is well worth the $$ and does exactly what he says it will.

Bosso [/B]

There are a few on this forum that call themselves "gurus" yet have no engineering qualifications or even an understanding of basic circuit theory They do the diy community a disservice by spreading mis truths and encourage irrational thinking.

Also if something is bad it will measure bad. Likewise if something measures equally as bad then it will also be bad. To say otherwise is a complete fallacy.

[pjpoes]

Originally posted by snoopy


There are a few on this forum that call themselves "gurus" yet have no engineering qualifications or even an understanding of basic circuit theory They do the diy community a disservice by spreading mis truths and encourage irrational thinking.

Also if something is bad it will measure bad. Likewise if something measures equally as bad then it will also be bad. To say otherwise is a complete fallacy.

This assumes that the measurements are a valid method for a particular criteria. While it seems that a great many people outside the scientific community propagate this belief, those of us within understand that, quite simple, this isn't always so. To take from the mantra of the scientific method in statistics, you do not accept the null hypothesis, you reject it, or fail to reject it. Failing to reject does not mean something is "bad", it means that under your particular test conditions it "failed to make the grade." Generally the first thing a good scientist will look at is his testing method, not the subject under test, as you always want to assume your testing method is flawed first, and rule out any possibility that this is true.

THD measurements of speakers, as has been discussed numerous times here and other places, is a useless measurement, in and of itself, with no scientific evidence for correlation between numbers and perception. I.e. a high THD doesn't necessarily mean bad sound, and low THD numbers don't necessarily mean good sound. I would refer you to Dr. Geddes work for this particular issue.

Another thing to consider in the body of literature on this subject is the audibility of distortion compared with frequency. My understanding from gleaning through this material is that distortion is least audible at low frequencies and most audible at higher frequencies. This would mean that higher distortion in the bass region will be of no consequence to sound.

None the less, if you really want to compare distortion, you can't use useless figures like THD and IMD, but rather a look at the spectrum itself. The graphs shown do not imply to me that an accurate method of distortion measurement is being carried out, and would not be a comparable indicator of good or bad sound.

[badman]

Did you start the thread for pure bashing sake? By all accounts, both subjective and objective, the rythmiks are in the elite few for subs of this type. Once you bring horns into the picture, sure, you can get more clean output. But to dig nearly as deep, the cost and size of the horn itself is a lot more than a goodly number of the rythmiks scattered around the room, which would perform much nicer under the test conditions.

Comparing apples to apples, the rythmik is an excellent performer. I've only heard them a couple times, and unfortunately, never in a system where I could give them a fair shake. But I've recommended them based upon reputation and technology many times, and everyone always returns glowing reviews. One friend's complaint was that it had so much super deep output that he had to stack a lot of books on the sub to keep it from dancing around, even though it wasn't audibly distorting.

[jlharden]

Hi badman,

.......agreed! Yes, my horn subs will produce more output and diminishing distortion levels, but also in a cabinet of more than 10x the volume. As you say, apples to apples. For the footprint, the Rythmik's are nearly impossible to beat. Say, did you move? Were you not a Indiana neighbor not so long ago????

Jerrod

[snoopy]

Originally posted by pjpoes

THD measurements of speakers, as has been discussed numerous times here and other places, is a useless measurement, in and of itself, with no scientific evidence for correlation between numbers and perception. I.e. a high THD doesn't necessarily mean bad sound, and low THD numbers don't necessarily mean good sound. I would refer you to Dr. Geddes work for this particular issue.

No, High THD measurements just means the equipment is bad !! Whether you think it sounds better or not is just your opinion and is irrelevant. Would you buy an amplifier that measured as bad as this ??

Also if THD is irrelevant then why try and reduce it using a servo ??

[AKSA]

No, Snoopy, you are dead wrong and you dismiss pjpoes with appalling arrogance......

Most SET amps measure somewhere up to 5% THD, yet they have qualities which make them amongst the most expensive, sought after amps in high end. You are saying all these audiophiles are idiots, and have no right to enjoy what they clearly enjoy. An absurd, elitist, purist argument.

You should recognise that it is distortion profile which is important; read Geddes. Your argument is entirely academic. Some like it savory, some like it sweet..... that is the market.

Hugh