Rythmik 12 or 15

[azanon]

Brian (or anyone else),

I was wondering if I could get a bit of advise on subs.

I'm in an approximately 3700 cubic foot room, but will have a "near-field" sub placement (sub directly behind couch on one side directed in - me sitting on the couch ~ 5ft away). Though my room is large, my entire 7.1 setup is on one end (one, 1/3rd of the room), and I don't really care about the sound performance on the other 2/3rds of the room.

Would a 12" be sufficient without anything nasty (like clipping) for up to about 100db? Technically, I have space for the 15", but I'd really prefer to not go that large unless you just think that's what I need in my case? FWIW's, my SB12+ doesnt have any issues playing to my demands, but I believe it has a bigger amp? (425 bash)

Also.... I own a SB12+. Are you pretty confident that when I compare your sub to my current one, that the end result is that my SB12 will go on ebay, and I wont return the Rythmik? :-) To be real, could I tell a difference? I do have a HSU test tone disk, btw.

Thanks,

Az.

[RythmikAudio]

Brian (or anyone else),

I was wondering if I could get a bit of advise on subs.

I'm in an approximately 3700 cubic foot room, but will have a "near-field" sub placement (sub directly behind couch on one side directed in - me sitting on the couch ~ 5ft away). Though my room is large, my entire 7.1 setup is on one end (one, 1/3rd of the room), and I don't really care about the sound performance on the other 2/3rds of the room.

Would a 12" be sufficient without anything nasty (like clipping) for up to about 100db? Technically, I have space for the 15", but I'd really prefer to not go that large unless you just think that's what I need in my case? FWIW's, my SB12+ doesnt have any issues playing to my demands, but I believe it has a bigger amp? (425 bash)

Also.... I own a SB12+. Are you pretty confident that when I compare your sub to my current one, that the end result is that my SB12 will go on ebay, and I wont return the Rythmik? :-) To be real, could I tell a difference? I do have a HSU test tone disk, btw.

Thanks,

Az.

I believe Ilkka has measured SB12+ and our 12" has better output and better extension. Furthermore, there are customers of ours who had SB12+ and they not only comfirmed the above two points, they also commented ours sound better. If you are happy with SB12+'s output, our F12 won't disappoint you. If you'd like to have something that is 3db or more higher output than SB12+, then I would recommend 15" sub to be on the safe side. The main downside with SB12 (hopefully SVS understand it) is the enclosure size is just too small. This is because internal volume of enclosure does not scale down well with external volume. So when a manufacturer uses an overly small enclosure, we can expect the output takes a toll because internal volume (the number that really affects low frequency efficiency) will look even much smaller. So advantage of that 425WRMS is completely evaporated with a smaller enclosure. Another victim of overly small enclosure is Velodyne DD12.

[azanon]

I believe Ilkka has measured SB12+ and our 12" has better output and better extension. Furthermore, there are customers of ours who had SB12+ and they not only comfirmed the above two points, they also commented ours sound better. If you are happy with SB12+'s output, our F12 won't disappoint you. If you'd like to have something that is 3db or more higher output than SB12+, then I would recommend 15" sub to be on the safe side. The main downside with SB12 (hopefully SVS understand it) is the enclosure size is just too small. This is because internal volume of enclosure does not scale down well with external volume. So when a manufacturer uses an overly small enclosure, we can expect the output takes a toll because internal volume (the number that really affects low frequency efficiency) will look even much smaller. So advantage of that 425WRMS is completely evaporated with a smaller enclosure. Another victim of overly small enclosure is Velodyne DD12.

I did stop by Ilkka, and there's one graph I'm assuming I'm not understanding based on what others have said.

On the Total Harmonic Distortion (THD) graph of the Rythmik 12, it shows it going "off the chart" (above 30%) at 24hz and anything below that frequency and 100db. When I pull up the same graph by Ilkka for the SB-12, it shows approximately 22% THD, then distortion actually falling for frequencies lower than that, at 100db/24hz. I assuming I'm reading that wrong somehow, because that graph would tell me that below 24hz, there's major distortion issues with a Rythmik?

Re: the extra 3db with the 15, I might just have to risk it with the 12. Seems like mathematically (from a stats point of view), there's no significant difference in volume between a sub that can play with negligible distortion at >100db, and one that can do an extra 3db more. I'm equating significant difference with > 5% difference in clear volume.

If my numbers are right here, that's an extra 69% in volume (size) for <3% increase in clear volume (between an F12 and 15). From my point of view, that seems like bad scaling the other way around (internal enclosure vs. external volume). Somewhere along the way, seems like enclosure size has to go up exponentially for a linear (or worse) increase in clear volume.

Your thoughts?

[Mike^S]

azanon, those graphs can be tricky to read. You must look at both the THD graphs and the output sweeps graphs at the same time to properly interpret them. Or you could just look at this chart:

http://www.hometheatershack.com/foru...formation.html

That chart tells you the maximum clean output for each sub at various frequencies.

Also, a 3dB increase is no joke. Since sound is logarithmic, 3dB does not correlate to a 3% increase in volume. It's actually much more than that. If you double the amount of amplifier power a sub has, you get a 3dB increase. It takes two identical subwoofers placed next to each just to get a 6dB increase.

[azanon]

azanon, those graphs can be tricky to read. You must look at both the THD graphs and the output sweeps graphs at the same time to properly interpret them. Or you could just look at this chart:

http://www.hometheatershack.com/foru...formation.html

That chart tells you the maximum clean output for each sub at various frequencies.

Also, a 3dB increase is no joke. Since sound is logarithmic, 3dB does not correlate to a 3% increase in volume. It's actually much more than that. If you double the amount of amplifier power a sub has, you get a 3dB increase. It takes two identical subwoofers placed next to each just to get a 6dB increase.

Thanks Mike. I knew the output for the SB-12 was a lot lower at those low frequencies. I just didn't know if those THD graphs were saying - "not a lot of output with SB-12 at lower frequencies, but for what there is, its low(er) distortion".

But yeah i see on that "compliation" graph, it clears that up for me.

I also knew, more or less, that you had to double amp power just to get a small increase in decibels. But I always concluded from that the opposite way of thinking - get a reasonable amount of watts, then don't worry about it anymore because the returns are diminishing.

I googled and found a site here that says a roughly 10db increase will be perceived by us as doubling the sound volume. http://www.windpower.org/en/tour/env/db/dbdef.htm So about 33% more volume for that increase in size. That seems more reasonable.

[azanon]

Hmm, maybe I didn't interpret that graph as wrong as I thought. Found a clip of Ilkka's quick comments:

DIY Rythmik Audio Direct Servo 12" sealed 56L
Extremely good extension. Very versatile frequency response adjustments. Can be used in larger and also in smaller rooms. Upper end of the frequency response rolls off above ~70 Hz. Quite high max SPL, but high deep bass distortion due to amp clipping. Brian says that he doesn’t want to use any limiters, but lets the amp clip/limit the output instead, so it doesn’t limit the dynamics. Low upper bass distortion, so the servo does its job well. Upper bass distortion mainly 2nd order distortion. Quite high deep bass power compression. Low group delay and fast decay. Good price/performance ratio.

http://www.hometheatershack.com/foru...html#post45289

BTW, I'm going to Iilka because you guys keep bringing him up.

So which is it, extremely low as Dave says in the product listing or is it high? I'm really just trying to understand, this is not a troll attempt. I'm asking because I'm actually considering this product.

[jbjb]

azanon, those graphs can be tricky to read. You must look at both the THD graphs and the output sweeps graphs at the same time to properly interpret them. Or you could just look at this chart:

http://www.hometheatershack.com/foru...formation.html

That chart tells you the maximum clean output for each sub at various frequencies.

Can someone enlighten me on how to interpret the chart?

Firstly, what is "max clean output"? Is clean defined by reference to % distortion or something else?

I assume the figure in each column is in dB units?

[curtis]

Can someone enlighten me on how to interpret the chart?

Firstly, what is "max clean output"? Is clean defined by reference to % distortion or something else?

I assume the figure in each column is in dB units?

Unless Brian(RythmikAudio) sees this thread again...I suggest you contact him and ask.

But for the second two questions...the answer is yes and yes.