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#1 ·
 http://www.rythmikaudio.com/index.html


There never seems to be an 'Official' Rythmik thread so....


Hopefully members can post here and representatives from Rythmik (Brian) can more readily answer questions that are normally strewn about in many threads.


Rythmik now offers complete subwoofers as well as the traditional kits.


Maybe Brian will subscribe.
 
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#28,381 · (Edited)
The trend with other vendors and even DIY seem to be to moving away from round ports to slotted ports. Most vendors (including HSU's triangular ports) are leaving the ports uncovered by the grill. SVS uses round ports but with a metal grill. Most user pics I see have the SVS grill removed in home.

I don't know anything about port design and the implications of different port shapes. Does the port shape make any significant performance difference or is it negligible? (When I visited chucky7 his JTR Captivator 1400 w/uncovered slotted ports still made some port noise at high volumes with 10-15Hz.)

My den subs (Energy S12.3) have downward facing ports and my media room subs are sealed. However, I have a Singstrix karaoke speaker with an exposed round port and my 3½-year-old cannot resist the temptation to put things in it. I have to keep the grills on all speakers and subs throughout the house. For those with little kids like me, running without grills covering round ports exposed can be risky.
I don't know why other manufacturers using slot configuration. I do struggle a bit before I have acess to tooling.

Port is transportation means. It carries air from one end to another. Do you ever wonder why all the pipes are round? Not sure if you read about chaos theory? The first few examples of those are all on real world examples of modelling with insufficient degrees of dimensions. For instance, if you hear people ask you to roll a marble ball to a destination what is the chance that you can hit a target. A student looks at this problem as one dimension problem and concludes 100% of time because he consider this problem as one dimension problem. The second student looks at it with a more complicated model -- 2 dimension. So the marble ball can fire at a range of angle. Then he come up with an estimation. The third student looks at this and figure this is really a 3-dimensional problem because the surface that we roll the marble ball is not completely flat. What I am trying to say here is "can air flow sideway in a slot port? At least it does not always go straight. Does the round port has better control to prevent air to go sideway? Consider it from 3 dimensional view point.


I am not trying to justify round port is always better. But the trade-off is beyond anyone's intuition. I like it because it produces more consistent flow. The slot port that you see for big subs all need to make 90 degrees sharp turn. What if there are wood glues stuck in one of the corner? That will certaintly make me nervous, while others may think no big deal.
 
#28,382 · (Edited)
This is a discussion that took place about 2 weeks ago. Is single port mode worth it over dual?




Here is what Josh Ricci at DB.com wrote in his review: www.data-bass.com/data?page=system&id=51&mset=63
Thanks for the recap. I am now the proud owner of another LVX12. I was able to talk my wife into another one and since they fit perfect into the wall enclosures and balanced out the wall, it was an easier sell for me.

I have to say that the customer service with Brian and Enrico at Rythmik is second to none - amazing, and makes me appreciate my purchase that much more knowing I bought these from company that actually puts the customer first. The shipping was super fast as well as responses to my questions and everything else - thank you again. Also, much easier to try to get these beasts into the house when they are delivered to your door step.

I have never had two subs, not to mention high end subs like Rythmik and I am still amazed at the sound and its hard to break away from the setup, movies and music. I even purchased a UMIK-1 mic, and downloaded REW of which I knew nothing about until about a week ago. All configured and ran my first sweeps - although still trying to interpret what it all means. Holy cow, when will it end!!

Right now, I have one sub with both ports open, and one with one port open and HT mode. Interesting to me reading about the various configurations.
 

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#28,384 ·
I don't know why other manufacturers using slot configuration. I do struggle a bit before I have acess to tooling.

Port is transportation means. It carries air from one end to another. Do you ever wonder why all the pipes are round? Not sure if you read about chaos theory? The first few examples of those are all on real world examples of modelling with insufficient degrees of dimensions. For instance, if you hear people ask you to roll a marble ball to a destination what is the chance that you can hit a target. A student looks at this problem as one dimension problem and concludes 100% of time because he consider this problem as one dimension problem. The second student looks at it with a more complicated model -- 2 dimension. So the marble ball can fire at a range of angle. Then he come up with an estimation. The first student looks at this and figure this is really a 3-dimensional problem because the surface that we roll the marble ball is not completely flat. What I am trying to say here is "can air flow sideway in a slot port? At least it does not always go straight. Does the round port has better control to prevent air to go sideway? Consider it from 3 dimensional view point.


I am not trying to justify round port is always better. But the trade-off is beyond anyone's intuition. I like it because it produces more consistent flow. The slot port that you see for big subs all need to make 90 degrees sharp turn. What if there are wood glues stuck in one of the corner? That will certaintly make me nervous, while others may think no big deal.
Good points!

I doubt glue is a concern with the cabinet quality of current ID sub manufacturers [now that Reaction Audio is gone… (too bad he smudged the RA initials!)].

I have no idea what effects 90° elbow turns have on air flow. (Thinking back to my Thermodynamics course just gives me headaches). I do know Jeff P wanted to avoid multiple port turns when designing his latest JTR Captivator 2400 (very unique/odd form factor). I know performance compromises had to have been made but I absolutely love the PSA ported 18 form factor, with the dimensions of a sealed sub!

I believe the FV18HP and FV25HP will be exciting alternatives to the JTR subs. Any ETA on the amps yet? Are they still in manufacturing or are they "in the mail"? Are the controls/tuning options the same as any of the existing amps (aside from power)? Or any new differences?
 
#28,385 ·
Good points!

I doubt glue is a concern with the cabinet quality of current ID sub manufacturers [now that Reaction Audio is gone… (too bad he smudged the RA initials!)].

I have no idea what effects 90° elbow turns have on air flow. (Thinking back to my Thermodynamics course just gives me headaches). I do know Jeff P wanted to avoid multiple port turns when designing his latest JTR Captivator 2400 (very unique/odd form factor). I know performance compromises had to have been made but I absolutely love the PSA ported 18 form factor, with the dimensions of a sealed sub!

I believe the FV18HP and FV25HP will be exciting alternatives to the JTR subs. Any ETA on the amps yet? Are they still in manufacturing or are they "in the mail"? Are the controls/tuning options the same as any of the existing amps (aside from power)? Or any new differences?
Amplifiers are on the way. They should be here in about 2 weeks or so. The controls are basically the same as the HX800XLR3 but on HX1000XLR3 and HX2000XLR3 amps the FREQ selection is 12Hz/14Hz/18Hz instead of 14Hz/20Hz/28Hz.
 
#28,386 ·
Port is transportation means. It carries air from one end to another. Do you ever wonder why all the pipes are round? Not sure if you read about chaos theory?
Chaotic indeed. Don't forget people, air is compressible. Getting air to flow though complicated plumbing is, um... difficult. You'd be surprised how little resistance it takes to bring air flow to a near halt. It'll compress rather than flow given half a chance.

If you want fun, read up on Bernoulli's principle. Compressible fluid flow (fluids technically includes both liquids and gasses; air at normal atmospheric conditions is a fluid, which is what makes compressible fluid flow so interesting to people who design everything from airplanes to residential HVAC duct work) is a branch of fluid dynamics that comprises a huge chunk of a mechanical and aerospace engineering degree.

What I learned from my fluid dynamics classes comes down to this: Keep it (very) simple. And it doesn't get much more simple than a round port. Just sayin'.
 
#28,387 ·
Chaotic indeed. Don't forget people, air is compressible. Getting air to flow though complicated plumbing is, um... difficult. You'd be surprised how little resistance it takes to bring air flow to a near halt. It'll compress rather than flow given half a chance.
have you heard the fv15hp compress air at max output at low frequency? it's fine if there's music or something to cover it up, but to hear it alone doesn't sound nice. a perfect example is to queue up tron legacy and turn everything up to "that sweet spot" (reference volume, etc), and skip to the scene where sam is transported from the arcade to the grid after initiating the laser aperture. at lower volume it sounds amazing but sounds kind of bad to hear all of that port noise when it happens because all of the ambient music/sound is turned way down at that moment.
 
#28,388 ·
Thanks all this information, including the plots. This does help me put your comments into some context. It sounds like your room a nice size, but not too terribly large, but the stairway to the other rooms makes the entire space quite a bit larger. I'm planning to build a 12.5 by 18.5 by 7.2 ft sealed room in my basement. That is the largest I can get avoiding change in ceiling heights and structural support poles. The good news, about the smaller size, is that it makes it easier to pressurize the space, even with sealed Rythmik subs. It sounds like I have similar goals as you of being able to have low distortion and little to no compression even up close to reference volume. Because of this I was thinking of a pair of F25s, since I will be primarily watching movies, which is quite a bit more demanding. I would like to stay with a sealed Rythmik vs. a ported one since Brian and Dave have both said that you can hear the faster transient response of the sealed Rythmiks and it will more closely match the transient response of my Ascend speakers with the Raal ribbon tweeters. I'm hoping to not have to engage the rumble filter to allow the sub to extend as far as it possibly can. I'm in the camp of just wanting to be able to faithfully reproduce whatever is in the signal, but I don't want to spends tens of thousands of dollars chasing after subs that can play single digits in my room with authority either. Hopefully I don't run into compression with some films to have to limit the low end.

Yes, I'm in the same camp and I prefer the sealed too. Hard to say but I will take a guess that you should be able to add 10 db to my numbers if you do a pair of F25's. Single digits will still be tough since the excursion is going to kick the limiter without the filter. I'd hold out and see if you can do a pair of F18 or F28's if you have the room since they are designed slightly lower in extension and can move more air than the 15's. I'm probalby going to go upgrade for the F18HP myself. I hope it is as or more musical as the 15
 
#28,390 ·
I know. :)

I was looking closely at his REW plots and thinking about the size of my room and expecting quite similar results. But, he was running into compression if he upped the volume much more than that. Reference volume (for movies) can demand as much as 115 dB peaks. According to Rythmik's webpage, the F25 has about 4 dB more output than the L22, which basically gets you up to those 115 dB peaks without high distortion or compression. So I guess I need to ask myself if I really want to be able to cleanly hit reference volume, in which case I would need to likely go with the F25s. Or, if I don't mind setting just being okay with say -5 dB from reference volume being as loud as I will listen.

I guess with this it also illustrates the price that you have to pay to go with a sealed sub vs. a vented sub, especially if you want to be able to crank things up every now and then for home theater use. And even being in a small room. A pair of FVX15s could get me basically where I want to be in terms of output limit, saving some money while doing so. But, Brian and Dave both seem to say that they can tell the difference in the transient response from the ported to sealed Rythmik. So the purist in me tells me to go with the sealed Rythmik, even though it is more expensive to get the output I want for home theater use.
I would always shoot for clean reference capability or you will be upgrading again. The FVX15 will not extend to 7hz, so you will actually have less output down that low. I personally would not worry about anything below 12hz but that is jmo. The F25's sound like what you are looking for.
 
#28,392 ·
:eek: The deep just got deeper
Also, the port tuning frequency is 12Hz with 3 ports on FV25 and 2 ports on FV18. The FV18 in three ports is 16Hz. Next week I will post some pictures of FV18 and FV25 naked (no drivers, no amps) so you guys can see internal parts. The ports in FV25 make him looks like "Darth Vader" :)

About finishes: the F18HP will come in the three finishes (black oak, black matte and piano gloss). The FV18 in black oak veneer and flat matte paint and the FV25 in flat matte paint only.
 
#28,393 ·
have you heard the fv15hp compress air at max output at low frequency? it's fine if there's music or something to cover it up, but to hear it alone doesn't sound nice. a perfect example is to queue up tron legacy and turn everything up to "that sweet spot" (reference volume, etc), and skip to the scene where sam is transported from the arcade to the grid after initiating the laser aperture. at lower volume it sounds amazing but sounds kind of bad to hear all of that port noise when it happens because all of the ambient music/sound is turned way down at that moment.

Yes. That is a tough one. The solution to "reduce" port noise is to increase the area of port opening. However, L/A (L is port length, A is port area) needs to be kept the same in order to keep tuning frequency the same. So if I increase the area, I need to bend the port with an elbow. Since now we have the elbow, I will see what I can do.
 
#28,394 · (Edited)
Chaotic indeed. Don't forget people, air is compressible. Getting air to flow though complicated plumbing is, um... difficult. You'd be surprised how little resistance it takes to bring air flow to a near halt. It'll compress rather than flow given half a chance.

If you want fun, read up on Bernoulli's principle. Compressible fluid flow (fluids technically includes both liquids and gasses; air at normal atmospheric conditions is a fluid, which is what makes compressible fluid flow so interesting to people who design everything from airplanes to residential HVAC duct work) is a branch of fluid dynamics that comprises a huge chunk of a mechanical and aerospace engineering degree.

What I learned from my fluid dynamics classes comes down to this: Keep it (very) simple. And it doesn't get much more simple than a round port. Just sayin'.

I feel I can do the book-geek talk with you (hope you don't mind the word geek). Round shape has the provable lowest perimeter to area ratio of any shape and hence the least friction for air flow.
 
#28,395 ·
Amplifiers are on the way. They should be here in about 2 weeks or so. The controls are basically the same as the HX800XLR3 but on HX1000XLR3 and HX2000XLR3 amps the FREQ selection is 12Hz/14Hz/18Hz instead of 14Hz/20Hz/28Hz.

For sealed F18, I still recommend to use 14hz setting because as we have seen so many in-room plots that 14hz extension on L22/F15HP and etc aleray gives flat in room frequency response. The rumble filter however is set to lower, 13hz, which is lower than 18hz with F15/FV15HP. If customers still want to use 12hz setting on F18, we recommend to turn on rumble filter to protect the driver from over excursion. All these different extension setting is to provide trade-off between excursion and extension. Higher the extension setting, the less the excurison requirement.
 
#28,396 ·
Also, the port tuning frequency is 12Hz with 3 ports on FV25 and 2 ports on FV18. The FV18 in three ports is 16Hz. Next week I will post some pictures of FV18 and FV25 naked (no drivers, no amps) so you guys can see internal parts. The ports in FV25 make him looks like "Darth Vader" :)

About finishes: the F18HP will come in the three finishes (black oak, black matte and piano gloss). The FV18 in black oak veneer and flat matte paint and the FV25 in flat matte paint only.
Bummer that the FV25 will not have the black oak veneer option.
 
#28,398 ·
This can be challenging. I do appreciate the suggestion.


As for ways to reduce port noise, it is all related to how much air we push out of those ports. That is contradictory to the fact that we want to make it more dynamic and easier to move air in and out of the ports.


Completely understand. Photoshopping is one thing but actually making a working, beneficial, and cost effective version is a whole different animal. The grill would need to be removable but still connectable and work as a seamless extension ports to the main box ports. On the plus side, it would add an inch or so of extension to the port length. Though that could be a negative as well.
 
#28,399 ·
I feel I can do the book-geek talk with you (hope you don't mind the word geek). Round shape has the provable lowest perimeter to area ratio of any shape and hence the least friction for air flow.
Yep. And I *am* a geek, no question. ;)

Interestingly, it's the air movement at the perimeter (tube wall) that's often the problem. The air in contact with the wall of the tube tends to want to go into laminar flow, which is high drag, which means that air doesn't move very fast, or very much. The air flow you can get from most tubes is usually considerably less than one would think based on the cross sectional area of the tube. That's because the air near the tube walls isn't moving much (laminar flow), so most of the volume of air flow comes from the center of the tube (turbulent flow).

Yet another reason to prefer round tubes over slots.
 
#28,400 ·
I created a link my sig to my current REW measures for sub, speakers+sub, etc. I set it up for the flattest response aside from running sub hot. I did engage YPAO auto PEQ and I set sub to Low Extension/Damping with MiniDSP sub PEQ engaged (cut only).

I'm curious how much room for improvement there is in terms of these measures. I have linked the .mdat file in that post too.
 
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