Re: I will tell you why...
What is the bone I have to pick ??
Instead of defending the indefensible why don't you ask the proprietor of the said product to step up to plate and offer a plausible explanation for all on this forum to see ??
That is not asking a lot is it !!!
moray james said:
What is the bone I have to pick ??
Instead of defending the indefensible why don't you ask the proprietor of the said product to step up to plate and offer a plausible explanation for all on this forum to see ??
That is not asking a lot is it !!!
yes you ask too much...
I have no interest in asking the designers anythig. You are the one who questions the product. You refuse to go to the source (the designer) and to discuss the issues that you have with this product with the one person who knows the product better than anyone else. This has become a strange mission, I do not see the point of this thread any longer. Perhaps the moderator would not mind stepping in at this point. A cooling off period might be useful.
I have no interest in asking the designers anythig. You are the one who questions the product. You refuse to go to the source (the designer) and to discuss the issues that you have with this product with the one person who knows the product better than anyone else. This has become a strange mission, I do not see the point of this thread any longer. Perhaps the moderator would not mind stepping in at this point. A cooling off period might be useful.
Re: Re: I will tell you why...
OK, the driver itself. To produce 100dB at 20Hz from this driver in a 56l sealed box would require a peak to peak excursion of around 36mm, slightly over xmax. It would also require a steady 400W to produce that much motive power, well over the drivers' claimed power handing ability. Thus, this driver would not be able to meet the "criteria" that you claim the manufacturer claims.
Try the DS1500 driver instead. To produce 100dB at 20Hz from this driver in a 125l sealed box would require a peak to peak excursion of around 23mm, roughly 2/3 xmax. It would only require a steady 120W to produce that much motive power, well within the drivers' claimed power handing ability. Thus, this driver may be able to meet the "criteria" - at least it certainly wouldn't melt.
You see, it appears to me that you want every driver/box/amplifer combination from Rythmik to meet the "criteria". It's quite possible that one or more of the larger combinations can meet that "criteria", but obviously they have not been tested - only the smallest box/driver/amplifier was.
I don't expect the 7" drivers on my Elacs to play flat down to 20Hz. I don't expect the 12" Lambdas that I have in my DIY sealed (spookily - 56l) bass boxes to play flat down to that level either. With a bit of EQ and not too much amplification, they will (+0/-2dB). But if I'm playing music (or have the HT up) loud, then I turn the EQ down (or off). There's only so much you can do with a 12" single driver. With a 15" reflex or 15" + PR, or 2x12 + PR (or 2) the 3% distortion @100dB @20Hz "criteria" might be achievable.
If you cannot see that the proprietor has absolutely nothing to gain from attempting to "defending the indefensible", then I guess you cannot. You could probably try mailing him to ask this question, but I would not be doing it myself, as all the people I know of are quite satisfied with his products (Ilkka included).
I hope this is a better debating type response!
snoopy said:
OK, the driver itself. To produce 100dB at 20Hz from this driver in a 56l sealed box would require a peak to peak excursion of around 36mm, slightly over xmax. It would also require a steady 400W to produce that much motive power, well over the drivers' claimed power handing ability. Thus, this driver would not be able to meet the "criteria" that you claim the manufacturer claims.
Try the DS1500 driver instead. To produce 100dB at 20Hz from this driver in a 125l sealed box would require a peak to peak excursion of around 23mm, roughly 2/3 xmax. It would only require a steady 120W to produce that much motive power, well within the drivers' claimed power handing ability. Thus, this driver may be able to meet the "criteria" - at least it certainly wouldn't melt.
You see, it appears to me that you want every driver/box/amplifer combination from Rythmik to meet the "criteria". It's quite possible that one or more of the larger combinations can meet that "criteria", but obviously they have not been tested - only the smallest box/driver/amplifier was.
I don't expect the 7" drivers on my Elacs to play flat down to 20Hz. I don't expect the 12" Lambdas that I have in my DIY sealed (spookily - 56l) bass boxes to play flat down to that level either. With a bit of EQ and not too much amplification, they will (+0/-2dB). But if I'm playing music (or have the HT up) loud, then I turn the EQ down (or off). There's only so much you can do with a 12" single driver. With a 15" reflex or 15" + PR, or 2x12 + PR (or 2) the 3% distortion @100dB @20Hz "criteria" might be achievable.
If you cannot see that the proprietor has absolutely nothing to gain from attempting to "defending the indefensible", then I guess you cannot. You could probably try mailing him to ask this question, but I would not be doing it myself, as all the people I know of are quite satisfied with his products (Ilkka included).
I hope this is a better debating type response!
Snoopy, I have no interest in Rhythmic subs, never owned one or have an interest in owning one (because I'm going to use something else).
However, I do find the quote you posted from their website unsettling, and if I were interested in the product and made the comparison on a tech basis as you did, I would be a bit shy about ordering one. I do not believe there is any malicious intent, just poor wording.
However, I do find the quote you posted from their website unsettling, and if I were interested in the product and made the comparison on a tech basis as you did, I would be a bit shy about ordering one. I do not believe there is any malicious intent, just poor wording.
Re: Re: Re: I will tell you why...
Sure I could have asked the proprietor and I originally was going to do that but then I thought someone on DIY forum would be able to clear it up quickly but as you can see it has become quite controversial.
And like you said to get a 12 inch driver to deliver the goods at high SPL in a sealed enclosure is no mean feat unless you use some sort of distortion reducing techniques such as a servo which is essentially the claim made by Rythmik.
Cloth Ears said:
Sure I could have asked the proprietor and I originally was going to do that but then I thought someone on DIY forum would be able to clear it up quickly but as you can see it has become quite controversial.
And like you said to get a 12 inch driver to deliver the goods at high SPL in a sealed enclosure is no mean feat unless you use some sort of distortion reducing techniques such as a servo which is essentially the claim made by Rythmik.
The truth is that the distortion plots are completely deceiving for an expensive driver with motional feedback and such a claimed lineal excursion capability, even if only results above 35Hz are considered.
However, given the extremely low sensitivity of such drivers, the problem is more likely to be that the 350W amplifier is running out of power below 50Hz at 105dB (example: 350W are 25dB, the driver may be 87dB/W and the sealed box may cause it to be already -7dB at 50Hz, 87-7+25=105dB).
Note that large bass horns routinely provide 105dB with less than 10 watts of input power and sub 1% THD down to 30Hz or lower. SPL over 120dB with THD in the 1% range is easily obtained. This really makes me ask myself if all this ultra-expensive long-excursion and servo technology is worth the effort. It has never been for me.
However, given the extremely low sensitivity of such drivers, the problem is more likely to be that the 350W amplifier is running out of power below 50Hz at 105dB (example: 350W are 25dB, the driver may be 87dB/W and the sealed box may cause it to be already -7dB at 50Hz, 87-7+25=105dB).
Note that large bass horns routinely provide 105dB with less than 10 watts of input power and sub 1% THD down to 30Hz or lower. SPL over 120dB with THD in the 1% range is easily obtained. This really makes me ask myself if all this ultra-expensive long-excursion and servo technology is worth the effort. It has never been for me.
Eva said:
I'd go along with that except at the 90dB and 95dB marks the performance is fairly ordinary which I wouldn't have thought to be attributable to amplifier overloading.
snoopy said:
Any sealed driver that is equalized (through servo, linkwitz transform or otherwise) flat to 20hz has VERY different power requirements at 20hz than in the midband. Thus 90-95db might require significant power ... in a sealed sub it is by no means "ordinary."
Using basta to simulate a 12" with the rhythmik parameters requires 24db gain over 2.83 V to hit 95db at 2m with a ground plane. (which is 400+ W)
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.
Snoopy - If you add the word vented to the statement that got your panties in a wad - the statement is accurate
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The sealed servo sub gets you a small footprint sub with reasonable distortion, low group delay and excellent extension.
The vented servo sub gets you a medium footprint sub with low distortion, high group delay, and excellent extension
A hornsub gets you enormous footprint, vanishingly low distortion, and moderate to poor extenstion unless equalized.
ALL OF THESE can be well engineered ... even if one statistic is better or worse than another... it is a question of tradeoffs ... or "horses for courses"
Sean
seanzozo said:
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/for...index-subwoofer-tests-manufacturer-model.html
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 $$ and does exactly what he says it will.
Bosso
These tests are good only as a comparison to other tests done by the same tester, and, as he himself has told me, they even vary by ambient temperature according to what time of year he conducted them, so they can't even be compared to each other in some respects.
If you look at his CEA 2010 results, the Rythmik 12 is the highest rated 12" sealed sub he has tested to date by clean RMS output.
Its results put it neck and neck with the twice as large SVS 12" ported 20-39 cylinder sub (in 12Hz tune, the only tune with clean output that low), a truly remarkable achievement, as anyone who has ever built a 12" sealed subwoofer with a 350 watt power plant would know.
As was mentioned, the variable F3 and system Q make this little sub very versatile and the election to forego the use of limiters allows for the severe abuse it was subjected to in the test that resulted in the THD sweep posted above.
The youngster who conducts the tests and his avid fans tend to be young fellows who often engage in SPL race discussions, whereas the designer of the Rythmik 12" kit is a nuance designer who has a better grasp on the theories and mechanics of such a subwoofer than just about anyone I've met. He looks to a result of quality listening through a versatile machine, which his kit delivers in spades.
If quality and versatility are the primary concern, Brian's servo kits will fit the bill and live up to all of his claims. If dBSPL is what matters, build more than 1 kit, or move up to multiples of his 15" kit and have both bases covered (as was suggested).
Brian Ding is a first rate gentleman and an excellent engineer. His stuff is well worth the $$ and does exactly what he says it will.
Bosso
bossobass said:
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.
snoopy said:
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.
Where is this going?
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.
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.
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
.......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
pjpoes said:
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 ??
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
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
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