tinitus said:
Two wrongs don't make a right !! Anyone who profits by making false claims should be exposed to prospective purchasers so they can make informed decisions. Sure it's not fair to single out one individual when others do it, but there is nothing stopping others from posting on this and other forums to alert others about the potential pitfalls or limitations of particular products so long as they back up their claims with evidence which I have done.
But the way you lot carry on defending the indefensible makes me wonder that it must be normal practice to stand by a let other people get duped 🙁
Snoopy,
This is a naive crusade against rogue traders. Even the law cannot stop these guys; that's why most countries practise 'caveat emptor'. Consumers are not all ignorant; a huge number of them undertake due dligence before they buy anything. It is a responsibility we all have prior to purchasing anything. And many countries have consumer advocates, and even more have reviews of products which measure one against the other - Choice in Oz, for example.
I suspect you have too much time on your hands.......
Hugh
This is a naive crusade against rogue traders. Even the law cannot stop these guys; that's why most countries practise 'caveat emptor'. Consumers are not all ignorant; a huge number of them undertake due dligence before they buy anything. It is a responsibility we all have prior to purchasing anything. And many countries have consumer advocates, and even more have reviews of products which measure one against the other - Choice in Oz, for example.
I suspect you have too much time on your hands.......
Hugh
AKSA said:
Likewise you must have equally as much time to make replies 😉
If the Internet and chat forums are just about patting each other on the back then I think it is a wasted resource. Most of the people I know and including myself usually do research on the Internet before making a product purchase just to see the opinions of others. That's what's good about the Internet 😉 And consumers are not all ignorant provided they have done their due diligence beforehand 😉
PS I thought you weren't going to reply anymore 😉
snoopy said:
You've definitely got your posts in this thread summed up correctly with that quote 😉.
I count 2 views only... maybe you should re-read the thread.
Hello again snoopy
Yes, over 2000 views, maybe several 00 folk.
For one comparison, Geddes on Waveguides has about 120,000 views, so as yet it’s not the hottest topic around.
What was that definition again? 😉
I think your point may have some validity in specific isolation.
But in the bigger picture of the Rythmik range, it would be wrong to suggest either relative quality and/ or price that they are “unfair”.
If Rythmik were misleading, why has no one chimed in?
By all means, get stuck into false claims, 🙂
but of all the advertised products and services in all the woild, I suggest there would be many better candidates to rail against.
Good evening, sir
Yes, over 2000 views, maybe several 00 folk.
For one comparison, Geddes on Waveguides has about 120,000 views, so as yet it’s not the hottest topic around.
What was that definition again? 😉
I think your point may have some validity in specific isolation.
But in the bigger picture of the Rythmik range, it would be wrong to suggest either relative quality and/ or price that they are “unfair”.
If Rythmik were misleading, why has no one chimed in?
By all means, get stuck into false claims, 🙂
but of all the advertised products and services in all the woild, I suggest there would be many better candidates to rail against.
Good evening, sir
Interesting argument, if a bit overwrought. =)
I think I'll have to come down on Snoopy's side. The claim he quotes from Rythnik's website does seem to imply that their subs are much better than others.
When independant tests show this may not be true, it's well worth asking why. (And there have been some good answers.)
I've read most of the Rythmic site, some time ago, because it's well written and offers a good look at an unusual technology. There are a lot of claims on the site for how much better servo subs are than non-servo. If this turns out not to be true, or even if some tests indicate it might not be true, it's nice to know why. And to know if the tests are valid.
Nothing wrong with that.
I think I'll have to come down on Snoopy's side. The claim he quotes from Rythnik's website does seem to imply that their subs are much better than others.
When independant tests show this may not be true, it's well worth asking why. (And there have been some good answers.)
I've read most of the Rythmic site, some time ago, because it's well written and offers a good look at an unusual technology. There are a lot of claims on the site for how much better servo subs are than non-servo. If this turns out not to be true, or even if some tests indicate it might not be true, it's nice to know why. And to know if the tests are valid.
Nothing wrong with that.
panomaniac said:
That wouldnt be the first time someone makes claims like that, but who believes it anyway
Seems someone will be very busy fore a long while
It has long been my view that the servo is mostly to the benefit of the company, making it possible to deliver very good sound quality with relatively cheap drivers, resulting in rather low bargain prices
It could be entertaining though with a thread collecting the many funny unrealistic claims from different companies
Is the winter weather in Melbourne making everyone down south touchy lately??... 😀
I have built a couple of the Rythmik subs and although they are not the last word in subs, for the money the quality is excellent, far exceeding what we can buy in the shops in Oz for the same price.
I have not tested their distortion, but it is the only subwoofer I have tried that can integrate reasonably seamlessly with my mains (Dunlavy IV-A's, no slouches) and do double duty for a good HT rumble. They do however take some tuning to integrate (filters, delay).
I have built a couple of the Rythmik subs and although they are not the last word in subs, for the money the quality is excellent, far exceeding what we can buy in the shops in Oz for the same price.
I have not tested their distortion, but it is the only subwoofer I have tried that can integrate reasonably seamlessly with my mains (Dunlavy IV-A's, no slouches) and do double duty for a good HT rumble. They do however take some tuning to integrate (filters, delay).
the winter in Melbourne is not as bad as at latitudes of say 45 degrees, but I find it somewhat a downer 
(disclaimer: an ex Sydney person)
On topic . .
> the only subwoofer I have tried that can integrate reasonably seamlessly with my mains (Dunlavy IV-A's, no slouches) and do double duty for a good HT rumble
which Rythmiks are you using?
Cheers
(disclaimer: an ex Sydney person)
On topic . .
> the only subwoofer I have tried that can integrate reasonably seamlessly with my mains (Dunlavy IV-A's, no slouches) and do double duty for a good HT rumble
which Rythmiks are you using?
Cheers
Snoopy I don't see anywhere in the Rhythmik site where specific claims about the quantity of distortion reduction or particular frequencies where the technology is most effective. I may have missed it, but my argument, which I think you have missed, is that the independent tests you show are misleading and irrelevant.
First, there is a big difference between distortion and IMD and THD. What I was saying was not that distortion is unimportant, but that using totals like THD and IMD were unimportant, as they are non-representative. Different techniques at different distances with different signals under different conditions will all show different results. Best that I can tell from the Rhythmik site, they seem to feel the tecnology is most effective from around 50hz on up. That would imply to me that to make meaningful comparisons, you need to look at that particular area.
Now before you fly off the handle on this one, keep in mind that work such as Dr. Geddes showed that masking effects would make distortion below that 50hz point inaudible up to a very large amount, and...that THD, IMD, and even his metric did a poor job of correlating with what people hear. It seems very clear from your posts that you do not understand what THD is, and feel that its a very concrete and real metric. It is not, it was a metric developed to get percentage thresholds of audibility for these distortions. I.e. instead of having to search through hundreds of graphs across broad frequencies and figure out whats really going on, you get one graph and one number that tells you all you need to know. The problem is that its an incorrect metric, and the distortions it totals do not reflect audible distortion well.
First, there is a big difference between distortion and IMD and THD. What I was saying was not that distortion is unimportant, but that using totals like THD and IMD were unimportant, as they are non-representative. Different techniques at different distances with different signals under different conditions will all show different results. Best that I can tell from the Rhythmik site, they seem to feel the tecnology is most effective from around 50hz on up. That would imply to me that to make meaningful comparisons, you need to look at that particular area.
Now before you fly off the handle on this one, keep in mind that work such as Dr. Geddes showed that masking effects would make distortion below that 50hz point inaudible up to a very large amount, and...that THD, IMD, and even his metric did a poor job of correlating with what people hear. It seems very clear from your posts that you do not understand what THD is, and feel that its a very concrete and real metric. It is not, it was a metric developed to get percentage thresholds of audibility for these distortions. I.e. instead of having to search through hundreds of graphs across broad frequencies and figure out whats really going on, you get one graph and one number that tells you all you need to know. The problem is that its an incorrect metric, and the distortions it totals do not reflect audible distortion well.
snoopy said:
You are incapable of understanding these distortion curves, and of reading this thread. I have already posted on this but will summarize and quote my previous post. You have misrepresented the performance of the product--it is better than its peers and the servo accomplishes two useful mechanisms:
-It extends the bass and allows control over the shape of the frequency response
-It reduces distortion compared to comparable subs - when compared correctly
The charts posted from HTShack measure the distortion versus INPUT level not output level. The X db increments of the line refer to the output level for a given input level above the subs rolloff. Because the Rythmik is generally flat to 20hz because of the servo -- the graph makes the subwoofer preformance appear worse than it is in a simple graph A vs. graph B comparison. The publisher of these test has changed the presentation of the results because many people make the same mistake you have.
My original post on this
seanzozo said:
I would add that below 50hz, in many cases, amplifier clipping becomes the predominant distortion. Even the guy measuring indicates this in some cases (Including the Rhythmik tests). In fact, read correctly, the measurements, within the subs limits, are impressive.
tinitus said:
That's not true. There are no bargains in the Velodyne HGS or DD, Infinity IRS, Paradigm range etc. Show me a bargain priced mass produced servo subwoofer system that uses an el-cheapo driver and an actual mechanical or acoustical transducer device to provide the feedback ??
pjpoes said:
Not at 90 dB @ 1 meter
If amp clipping dominates at this level then the customer has been short changed 😉seanzozo said:
The Velodyne sub is 3db down at 22Hz according to the specs. You can then assume that its almost flat at 30Hz give or take half a dB. For this case it is possible to do a direct comparison at 30 Hz between the two subwoofers 😉 I leave the conclusions for yourself 😉
pjpoes said:
You're just splitting hairs. You might argue that one device that measures 3% THD is actually better than the one that only measures 1% because of its harmonic distribution of distortion components. But we are talking about 20 to 30% THD levels. Surely you don't mean to tell me that you can explain this away !!
Also if the distortion performance is not that relevant then why make the claim at all which is essentially what this thread is all about ?? This thread is not about the subjective merits of low bass distortion. That's another topic all together !!
snoopy said:
According to the same tests you present the velodyne is 12db down at 20hz, and 6db down at 22hz (note that +/-3 here = 6)
I will not "assume"" the velodyne is flat to 30hz when the graphs demonstrate that it is in fact 2db down at 30hz.
You are being dense. The velodyne limits at 98 db at 30hz at that point its distortion is 4% higher than the Rythmiks.
you continue to miss my point. You seem think that the percentage number means anything, even objectively, and I keep telling you, it doesn't. The only reason you see it so often is that its easy to measure.
I also didn't see 20 and 30% distortion in those graphs until the point where I would argue xmax and signal clipping would likely be equal culprits to a poor design. Given that this was a sealed subwoofer, it would not surprise me at all if, at 20hz, 90db's was more than it was capable of. You might think this sounds bad, but for comparison, an Adire Audio Brahma in a 1 cubic foot enclosure would require 350 watts to hit 91db's at 20hz free air. Thats with no equalization added.
Now add in an eq boost, which I believe these designs use, and the amplifier demands sky rocket. The sub can never produce, using a servo or not, more than its power handeling and xmax can allow at any given frequency. The amplifier can never give more either, so in the end, your probably seeing a reflection of speaker compression and/or amplifier clipping. I think the point is further realized when you see just how sharp an increase of distortion these subs, all of the subs measured, show, that implies clipping of something.
Now, as for the audibility of distortion. Well yes, research on this subject has shown that even 20 percent can be inaudible if at the right frequency and of the right order. As I recall from Geddes and Lee's work, some people could accurately detect and found objectionable distortion which measured a thd of just .1 percent. Yet other signals as high as 20-30 percent were found to be non-significant. That was why he made the claim, as have I, that no metric accurately reflects what we hear when distortion becomes that high.
When I looked at the Rhytmik subwoofers distortion above 50hz, and looked at its harmonics, they were as low as any I saw for the most part, with the exception of some more robust and better designs, such as the LMS TC-5400's.
I also didn't see 20 and 30% distortion in those graphs until the point where I would argue xmax and signal clipping would likely be equal culprits to a poor design. Given that this was a sealed subwoofer, it would not surprise me at all if, at 20hz, 90db's was more than it was capable of. You might think this sounds bad, but for comparison, an Adire Audio Brahma in a 1 cubic foot enclosure would require 350 watts to hit 91db's at 20hz free air. Thats with no equalization added.
Now add in an eq boost, which I believe these designs use, and the amplifier demands sky rocket. The sub can never produce, using a servo or not, more than its power handeling and xmax can allow at any given frequency. The amplifier can never give more either, so in the end, your probably seeing a reflection of speaker compression and/or amplifier clipping. I think the point is further realized when you see just how sharp an increase of distortion these subs, all of the subs measured, show, that implies clipping of something.
Now, as for the audibility of distortion. Well yes, research on this subject has shown that even 20 percent can be inaudible if at the right frequency and of the right order. As I recall from Geddes and Lee's work, some people could accurately detect and found objectionable distortion which measured a thd of just .1 percent. Yet other signals as high as 20-30 percent were found to be non-significant. That was why he made the claim, as have I, that no metric accurately reflects what we hear when distortion becomes that high.
When I looked at the Rhytmik subwoofers distortion above 50hz, and looked at its harmonics, they were as low as any I saw for the most part, with the exception of some more robust and better designs, such as the LMS TC-5400's.
pjpoes said:
Then look at its components. A good servo should reduce distortion by at least one order of magnitude !! This is not even happening at 40 Hz which is way above the amplifier limit and displacement limit for the driver. This means the servo is really doing nothing and the claims about distortion reduction on the website are not justified !!!
An externally hosted image should be here but it was not working when we last tested it.
well I think the servo does appear to be doing something for the higher order harmonics, which are the ones that matter. Again, if you would take the time to educate yourself on distortion, you would realize the lack of sense in your claims. I'm not arguing that the servo is a good thing or that this is even a good product, just that you don't seem to understand distortion. I had played around with servo subs once a while back, and my end conclusion was that a well designed driver in the right enclosure was a better idea. Thats my opinion, not everybody will agree.
Also, 1 percent distortion at 40 hertz would be completely inaudible to anyone when its of the 2nd harmonic nature.
Also, as I had mentioned earlier, these distortion graphs are not right. The person taking the measurements isn't clear with the harmonic distortion what frequency he is using, or how he is measuring it precisely. I read his posting, and all I can say is, he doesn't really know what he is doing, and these aren't right. The level of the 2nd harmonic is going to vary greatly depending on what frequency is used. He appears to be using an antiquated method for harmonic distortion measurements, using only a single sine tone of unknown frequency.
Also, 1 percent distortion at 40 hertz would be completely inaudible to anyone when its of the 2nd harmonic nature.
Also, as I had mentioned earlier, these distortion graphs are not right. The person taking the measurements isn't clear with the harmonic distortion what frequency he is using, or how he is measuring it precisely. I read his posting, and all I can say is, he doesn't really know what he is doing, and these aren't right. The level of the 2nd harmonic is going to vary greatly depending on what frequency is used. He appears to be using an antiquated method for harmonic distortion measurements, using only a single sine tone of unknown frequency.
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