Cloth Ears said:
Where in the original papers by Thiele and Small is there any emphasis on the analysis of a loudspeaker enclosure by listening to it ?? Can you explain how Theile or Small derived the small signal electro acoustical system response function by listening to various different speaker systems ??
To really understand the details in Thiele or Small's papers requires understanding of engineering circuit analysis and the dynamics of mechanical and acoustical systems. To say otherwise is just displaying your ignorance.
huh?? Thiele & Small correlated measurable electrical and mechanical driver parameters into a basis for predicting loudspeaker behaviour......
What an oddity this has become.......
What an oddity this has become.......
jlharden said:
They didn't derive the parameters from listening tests as some people are implying.
Hi
The sub as tested Did Not use the servo feedback loop to reduce distortion. The one he tested used the Linkwitz Transform circuit only.
Quote from the Rythmic web site
"The kit consists of a 370w amp (A370 SE) with a Linkwitz transform circuit a board, and a DS12 driver without servo feedback. With the Linkwitz Transform circuit we can get a better bass extension than what natural physics gives us. "
The LT circuit places great demands on excursion and amplifier power (ie potentially higher IMD) and trading this for a limited amount of frequency extension.
Besides it's normal for marketing to make broad sweeping statements or puffery of their products. You cannot use these statements in a technical argument unless lawyers are involved.
Cease fire now folks, hahaha.
The sub as tested Did Not use the servo feedback loop to reduce distortion. The one he tested used the Linkwitz Transform circuit only.
Quote from the Rythmic web site
"The kit consists of a 370w amp (A370 SE) with a Linkwitz transform circuit a board, and a DS12 driver without servo feedback. With the Linkwitz Transform circuit we can get a better bass extension than what natural physics gives us. "
The LT circuit places great demands on excursion and amplifier power (ie potentially higher IMD) and trading this for a limited amount of frequency extension.
Besides it's normal for marketing to make broad sweeping statements or puffery of their products. You cannot use these statements in a technical argument unless lawyers are involved.
Cease fire now folks, hahaha.
I was under the impression, having read the ht shack bit, that the sub was one using the servo feedback. Rhythmik offers both, and I would have thought that would have been made clear in the review. In fact, the tester makes the claim that the servo does appear to be working, so again, I must assume it was a servo unit.
I still stand by that the claims made my Rhythmik are perfectly acceptable given that they dont ever state the conditions for which it must be true. They do sell a subwoofer, in fact, more than one subwoofer which I would wager can do what they claim. It just so happens that the single 12" subwoofer with servo, in a sealed enclosure, under these particular test conditions (completely free air-no loading) could not meet the claims. However, as has been mentioned, they don't make this claim as something that must be met free air. The claim is less specific, so if, for instance, they were to be sued for false advertising, they could easily argue that the claim was meant to include in room loading.
As I've mentioned numerous times, I don't care what type of technology you use, a normal vented or sealed enclosure with a 12" woofer can not easily achieve 100db's at 20hz, in free air, with low distortion without a lot of amplifier power. This also means that the speaker must be capable of huge amounts of linear cone travel, and have huge thermal limits. A servo can help make a cones travel more linear, but I would argue that, in a real room, there are better ways to achieve it. As Zaph mentions in one of his writeups, low excursion woofers have less distortion than long excursion woofers. This of course means, used within their linear range, but still, if you need more linear range, just use more woofers.
If you did have a ported enclosure, that would change things some. At the port tuning, 20hz in the case of this argument, the cone would be at minimal motion, and thus, minimal distortion. This is actually seen very easily in the distortion graphs on the HT Shack website, as the ported units generally have a notch in the distortion around the same area as the tuning frequency. This is how my subwoofer achieves this claim. I special version of the TC 3000 subwoofer in a 5 cubic foot enclosure tuned to around 20-21hz. In my particular enclosure it only requires roughly 75 watts to achieve 100db's at 20hz, but if I seal the enclosure, that number increases by close to ten fold. As I recall I measured over 50 volts when I ran some tests a while back, at the time trying to show the efficiency difference of a ported system at low frequencies. This Rhythmik sub, which I believe at least used to have its drivers made for them by TC Sounds, would be in a similar boat. However, as I recall, they were based on the TC2000 not 3000, and would have been of the more typical small box parameters, and thus more limited.
oh and there is nothing unmusical about a ported subwoofer tuned to 20hz. In car audio competitions you tune to the cars resonant frequency, typically between 50 and 70hz. This makes for a peaky response, which is what you are referring to, but is quite different from a subwoofer tuned to 20 hz. The Bandpass designs only take this further by tuning to a very narrow point, especially the 6th and 8th order designs, which allow roughly 6-10 db's of gain at that point, but very sharp fall off on either side. That is nonmusical.
I still stand by that the claims made my Rhythmik are perfectly acceptable given that they dont ever state the conditions for which it must be true. They do sell a subwoofer, in fact, more than one subwoofer which I would wager can do what they claim. It just so happens that the single 12" subwoofer with servo, in a sealed enclosure, under these particular test conditions (completely free air-no loading) could not meet the claims. However, as has been mentioned, they don't make this claim as something that must be met free air. The claim is less specific, so if, for instance, they were to be sued for false advertising, they could easily argue that the claim was meant to include in room loading.
As I've mentioned numerous times, I don't care what type of technology you use, a normal vented or sealed enclosure with a 12" woofer can not easily achieve 100db's at 20hz, in free air, with low distortion without a lot of amplifier power. This also means that the speaker must be capable of huge amounts of linear cone travel, and have huge thermal limits. A servo can help make a cones travel more linear, but I would argue that, in a real room, there are better ways to achieve it. As Zaph mentions in one of his writeups, low excursion woofers have less distortion than long excursion woofers. This of course means, used within their linear range, but still, if you need more linear range, just use more woofers.
If you did have a ported enclosure, that would change things some. At the port tuning, 20hz in the case of this argument, the cone would be at minimal motion, and thus, minimal distortion. This is actually seen very easily in the distortion graphs on the HT Shack website, as the ported units generally have a notch in the distortion around the same area as the tuning frequency. This is how my subwoofer achieves this claim. I special version of the TC 3000 subwoofer in a 5 cubic foot enclosure tuned to around 20-21hz. In my particular enclosure it only requires roughly 75 watts to achieve 100db's at 20hz, but if I seal the enclosure, that number increases by close to ten fold. As I recall I measured over 50 volts when I ran some tests a while back, at the time trying to show the efficiency difference of a ported system at low frequencies. This Rhythmik sub, which I believe at least used to have its drivers made for them by TC Sounds, would be in a similar boat. However, as I recall, they were based on the TC2000 not 3000, and would have been of the more typical small box parameters, and thus more limited.
oh and there is nothing unmusical about a ported subwoofer tuned to 20hz. In car audio competitions you tune to the cars resonant frequency, typically between 50 and 70hz. This makes for a peaky response, which is what you are referring to, but is quite different from a subwoofer tuned to 20 hz. The Bandpass designs only take this further by tuning to a very narrow point, especially the 6th and 8th order designs, which allow roughly 6-10 db's of gain at that point, but very sharp fall off on either side. That is nonmusical.
pjpoes said:
His first post under test conditions, he talks about eq settings which says he has the kit with the LT option, and this option does not use servo feedback according to the vendor.
I missed the part where the tester claims about the servo working, besides how would he know unless he disconnected it or compared it to a similar setup without it.
Regards,
infinia said:
I still think you are incorrect. What I see him talking about is the dampening and extension switches, which are a feature of the servo system, not the LT. I believe this was a servo sub tested, not an LT. However, your main point about the LT is still true of the servo. When it comes right down to it, a servo is nothing more than an active "smart" LT.
infinia said:
I still think you are incorrect. What I see him talking about is the dampening and extension switches, which are a feature of the servo system, and the LT. I believe this was a servo sub tested, not an LT. However, your main point about the LT is still true of the servo. When it comes right down to it, a servo is nothing more than an active "smart" LT.
pjpoes said:
Wow I really cannot believe this, now you want to argue with me.
Some peoples kids.... just can't let it go. Now I remember why I took 6 mo. away from this forum.
Hey don't take it personally, I don't like what Snoopy has been doing here, I'm just saying, I think this was a servo sub. The person who tested it appears to have owned it, he claims it was a servo sub, and there is nothing about its features that suggest otherwise. The only mention of an eq feature I saw was the dampening extension switches, which are available on both the LT and Servo units.
snoopy said:
Where in my post did I say that they listened to the speaker drivers for the purposes of writing their various papers? They "listened" to their lecturers and teachers and to the wisdom of those who came before them (Rice, Kellogg, Thuras, Beranek and especially Novak in the case of Theile, and all of these plus Benson in the case of Small). They learned from these people and their papers.
You deliberately misunderstand any post that doesn't agree with your stated position and then attempt to denigrate that person from an incorrect position.
In answer to your post:
No. It is not fair to use claims of this type in order to sell your products. And, if you read the Rythmik site with an unbiased eye you will see that this is not the case. Almost every seller of parts for speakers does not benefit from this type of advertising hyperbole, as the people who buy their products use them to make real products (see also PHL, SEAS, Scanspeak, etc).snoopy said:
The hyperbole comes from end-product manufacturers (see anyone selling a pair of speaker cables or interconnects for over $5000 per pair). A person selling the parts for a subwoofer for under $500 is not in this category at all.
pjpoes, Infinia
It is my impression that Ikkla tested the servo system.
Ikkla seems technically competent, and he claims it was the servo version. F3 and damping options are available to both the servo and LT system.
I believe the Rythmik system uses both a sensing coil and a resistor for the servo. Since it is a diy kit, he needed to attach wiring to the sensing coil.
I would have liked to seen Ikkla test the system with and without the servo though.
It is my impression that Ikkla tested the servo system.
Ikkla seems technically competent, and he claims it was the servo version. F3 and damping options are available to both the servo and LT system.
I believe the Rythmik system uses both a sensing coil and a resistor for the servo. Since it is a diy kit, he needed to attach wiring to the sensing coil.
I would have liked to seen Ikkla test the system with and without the servo though.
infinia said:
That is totally absurd !! What would a lawyer know about technical issues anyway
This issue could have easily been resolved by the manufacturer right from the start 🙁Why use a Linkwitz transform when a properly designed servo could be use to extend the frequency response and to reduce distortion as well !!
Also it's not normal for marketing to make false and exaggerated claims about a product unless they are trying to profit out of peoples ignorance 🙁
Cloth Ears said:
It doesn't make any difference what price something is. There are many people that have been scammed by low cost items which weren't fit for their intended purpose or didn't meet the advertisers claims.
Like I said before there has been an exaggerated claim made for this subwoofer which has been contradicted by the test results from an independent tester.
Now either back up this claim or have it removed from the website !!
Alternatively if you don't agree with these test results then please provide alternative test results and state the conditions under which they were made.
Go here if you really want to get more info on this sub. Engage here, and you will get the owner involved, and his uses, and his distributors
http://www.audiocircle.com/circles/index.php?topic=47310.0
http://www.audiocircle.com/circles/index.php?topic=47310.0
Again go to the AC thread if you really want more info. Why dont you ask all your questions there. You WILL get a response from the owner of Rythmik
barfind said:
I've got a better idea, since you are a member of that forum why don't you ask on our behalf 😉 Alternatively ask him to come here and to kindly resolve the issue as I believe he is already a member of this forum. That would save having to re-register on another forum just to ask a simple question 😉
Aren't you interested in finding out as well ??
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