Official Rythmik Audio Subwoofer thread - Page 1221 - AVS Forum | Home Theater Discussions And Reviews
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post #36601 of 40624 Old 01-01-2019, 09:26 PM
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Originally Posted by enricoclaudio View Post
It says the FV25HP should be +7dB more powerful at 20Hz than FV15HP; however data-bass shows it is only +5.3dB. The difference between our numbers and data-bass numbers is +/-1.7dB.

It says the F18 should be -6.5dB from the FV18; according to data-bass it is -8.1dB. The difference between our numbers and data-bass numbers is +/-1.6dB.

Did you know that a Type 2/Class 2 SPL meter, even the most expensive ones like my $1500 Casella CEL-620 have an accuracy of +/- 1.5dB? If you take in count differences in software, ambient temperature, mic models, wind, external noise, you name it .... a difference of 1.7dB is totally acceptable and even inside the ANSI and IEC 651 Type 2/Class 2 accuracy standards. In fact, that difference is even inside the Class 1/Type 1 accuracy standards. The lower the frequency, the higher the tolerance goes up. For instance, at 20Hz, the tolerances are +/-2.5dB for Class 1 and +/- 3.5dB for Class 2.
Hello Enrico. You're citing tolerances for the mic, which is true - however that same deviation should appear consistently over all of his measurements. And typically, a calibration file is used to correct for all but a very small remnant of this deviation. All things considered, this shouldn't be a huge factor. But, it's possible.

I would like to think that he is controlling for many variables by averaging runs together and using standard protocols so as to not allow wind or weather to influence the results. He follows CEA-2010 subwoofer measurement standards. I don't think he's that much of an amateur

And if he were, that would be a problem, as Rythmik.com cites his results:

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Speaking of ANSI, the correct way to do these tests would be to take multiple samples. That is, you pick a sub, say an FV15HP, FV25HP, whatever, and you test more than one sample from different production times, and with at least two different microphones, and average the results together. That would account for sample variance in both the product and the measuring equipment. I know that isn't practical for someone not being paid by industry as a full-time quality tester, so his methods will have to suffice. But if there is variation in his results, whether it be from sample variation or mic accuracy of up to 2dB, then the conclusion has to be that I can't rely on his measurements. I just have a hard time believing he hasn't controlled for most of this, except for testing multiple samples. So is there a sample variance from sub to sub of up to 2dB? It's possible, but I would have a hard time believing that - knowing how much excursion, efficiency, or amp power needs to change to produce a 2dB difference, that would be a very large swing and I would conclude that there are production problems.

So what I'm saying is, I am unsure where the variances are coming from.

But Rythmik.com provides relative numbers, so we need something to base at least one of the subs on, in order to line up the others. If I can't use data-bass.com, maybe you have an internal measurement? For example, if we knew the 20Hz output of the F12, we could then fill in the rest of the blanks.

Thanks for helping to shed some light on this.

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post #36602 of 40624 Old 01-01-2019, 09:59 PM
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Originally Posted by Soulburner View Post
Hello Enrico. You're citing tolerances for the mic, which is true - however that same deviation should appear consistently over all of his measurements. And typically, a calibration file is used to correct for all but a very small remnant of this deviation. All things considered, this shouldn't be a huge factor. But, it's possible.

I would like to think that he is controlling for many variables by averaging runs together and using standard protocols so as to not allow wind or weather to influence the results. He follows CEA-2010 subwoofer measurement standards. I don't think he's that much of an amateur

And if he were, that would be a problem, as Rythmik.com cites his results:

Attachment 2504218

Speaking of ANSI, the correct way to do these tests would be to take multiple samples. That is, you pick a sub, say an FV15HP, FV25HP, whatever, and you test more than one sample from different production times, and with at least two different microphones, and average the results together. That would account for sample variance in both the product and the measuring equipment. I know that isn't practical for someone not being paid by industry as a full-time quality tester, so his methods will have to suffice. But if there is variation in his results, whether it be from sample variation or mic accuracy of up to 2dB, then the conclusion has to be that I can't rely on his measurements. I just have a hard time believing he hasn't controlled for most of this, except for testing multiple samples. So is there a sample variance from sub to sub of up to 2dB? It's possible, but I would have a hard time believing that - knowing how much excursion, efficiency, or amp power needs to change to produce a 2dB difference, that would be a very large swing and I would conclude that there are production problems.

So what I'm saying is, I am unsure where the variances are coming from.

But Rythmik.com provides relative numbers, so we need something to base at least one of the subs on, in order to line up the others. If I can't use data-bass.com, maybe you have an internal measurement? For example, if we knew the 20Hz output of the F12, we could then fill in the rest of the blanks.

Thanks for helping to shed some light on this.
Honestly dude, what is your goal exactly by picking apart Rythmik and Databass? The very nature of all these elements is.....variable. That means unless someone can control the weather and all of the tolerances of each part that goes into a sub and the testing equipment , then that means there is going to be a variance. Let alone figuring in human error. No one would be able to nail down exact figures.

If those don't satisfy you, then I'm sure you could buy multiples of each sub and multiples of measuring equipment and test on multiple days to get your answer.

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post #36603 of 40624 Old 01-02-2019, 12:06 AM
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Originally Posted by Soulburner View Post
I no longer believe this is accurate:

Attachment 2504104

The main reason I have come to this conclusion is based on the F18 and FV25HP underperforming at data-bass.com compared to what is expected. So when I make a chart out of all Rythmik subs, based on the relative performance numbers from Rythmik.com, these two look like outliers, with only middling performance per dollar. I believe in Rythmik subs and don't think this is true.

It says the FV25HP should be +7dB more powerful at 20Hz than FV15HP; however data-bass shows it is only +5.3dB.

It says the F18 should be -6.5dB from the FV18; according to data-bass it is -8.1dB.

The other possibility is that the data-bass results are legitimate and the relative numbers need to be revised. This is more likely. @enricoclaudio or @Rythmik , in the design and rollout of the new Rythmik.com site design, is there an effort to fix these relative performance numbers? If so, I would look at the whole range and not just the examples here. It's been a very useful tool, but I think it needs a little attention
The short answer is the number is just a guidance, and more importantly, it is not intended to comply with CEA-2010 standard. Also the resolution of our numbers is largely 1db. So let us not over-study it.

Data-bass lists CEA-2010 passing numbers in the spreadsheet. For newer measurements (maybe after 2012), Josh adds another set of numbers called max SPL without THD limit (let us call this non-CEA max SPL). Even though ideally we would like to have CEA-2010 and non-CEA be the same, but we can still see models like F18 with a small difference. For F18, those two numbers are 103.2db and 104.5db, respectively @20hz . So we should have added 1.3db to F18 in your comparison.

FV25 is a different situation. We can certainly adjust the number back by 1db so that it is shown to be 6db higher than FV15HP. On the other hand, at 12.5hz, FV25 is indeed higher by 6.9db over FV15HP based on CEA-2010 passing numbers.

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post #36604 of 40624 Old 01-02-2019, 07:51 AM
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Originally Posted by Soulburner View Post
Fill in the blank:

When one goes from say a 12" sealed Rythmik to a 15" ported Rythmik, and output power from the amp remains the same, distortion should be noticeably lower due to the larger driver and venting efficiency gain. This would have an effect on the sound that could be described as ____________?

Quieter? More tame? More articulate?

Yes, I know there is also a change in impulse and transient response. Are those changes large enough to counter the effect of lower distortion? I would think not, but it would be good to hear some opinions.
I will put "full-bodied" or "authoritative". Both are because ported subs have longer ringing. But one can use it towards their preference if "full-bodied" or authoritative is what he likes.
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post #36605 of 40624 Old 01-02-2019, 02:36 PM
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I have both fv15hp and fv25hp. when I ran just the fv15hp i got 117db...when I added fv25hp I was getting 125db's....the way I was measuring was with a rat shack spl meter and just walking around my room looking for loudest spot. I was playing music...mainly nelly. so the highpoints probably over 40hz....shoot probably 80hz. when I was running rew sweeps I think I only got to 120 dbs for both subs together...think i was doing something wrong with mic settings or something -12 or -18 switch on mic) anyways my point is the fv25hp alot louder than fv15hp...when I 1st got fv25hp I thought it was like 10db louder.

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post #36606 of 40624 Old 01-02-2019, 07:34 PM
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Originally Posted by toddct View Post
Honestly dude, what is your goal exactly by picking apart Rythmik and Databass?
As a customer, I want to know how much bang I'm getting for my dollars. Don't tell me that having accurate product information wouldn't be of benefit . This all matters because if the numbers go one way, one sub would be the better purchase. But if they go another way, another one becomes the better purchase from an output per dollar perspective. I've put together a helpful spreadsheet that arranges all the subs in relation to each other in the same way as Rythmik, but also includes how much output you get per dollar. At this point my confidence in some of the numbers is not great due to the problems reconciling with data-bass. So if Rythmik's site is more accurate, all we need is the 20Hz output of one sub and we can line up the rest of the range. Due to the aforementioned problem, we have to be very careful pulling such a number from data-bass. That is why I set out to determine which statistic was more believable. I need to make sure that the basis for the comparison is accurate.

EDIT: Rythmik clarified below, which corroborates what Schrodinger was saying yesterday.

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post #36607 of 40624 Old 01-02-2019, 07:44 PM
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Originally Posted by Rythmik View Post
I will put "full-bodied" or "authoritative". Both are because ported subs have longer ringing. But one can use it towards their preference if "full-bodied" or authoritative is what he likes.
So the answer is that the change in impulse response has such an effect, that even after the reduction in distortion, it still sounds more full-bodied. Very interesting, thanks! That helps put things in perspective. Really eyeing a pair of FVX15. Trying to be careful to not make the wrong choice (as if there is a wrong choice with Rythmik!), but I suppose the worst-case scenario is I pay return shipping if for some reason I don't like the vented sound. I'm constantly finding myself boosting the low end so maybe this is what I need. Maybe with the tax refund, though I fear it may be smaller due to tax law changes. We'll see.

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post #36608 of 40624 Old 01-02-2019, 07:53 PM
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Originally Posted by Rythmik View Post
Data-bass lists CEA-2010 passing numbers in the spreadsheet. For newer measurements (maybe after 2012), Josh adds another set of numbers called max SPL without THD limit (let us call this non-CEA max SPL). Even though ideally we would like to have CEA-2010 and non-CEA be the same, but we can still see models like F18 with a small difference. For F18, those two numbers are 103.2db and 104.5db, respectively at 20hz. So we should have added 1.3db to F18 in your comparison.
That makes sense. But instead of adding to F18, let's correct the FV15HP.

You seem confident in the FV25HP numbers, so perhaps the FV18 tested a bit stronger than expected, or it benefited from measurement variation. So let's say that the FV25HP is the one we can have confidence in. That puts it at 113.6dB and FV18 at 109.6. That 4dB lines up with the difference in amp power and driver area. Then the FV15HP would be at 106.6, exactly 3dB below FV18. Then, the F18 would be 103.1 - it measured at 103.2, so things are lining up damn near perfectly now. Thank you, Brian!

Quote:
Originally Posted by Rythmik View Post
FV25 is a different situation. We can certainly adjust the number back by 1db so that it is shown to be 6db higher than FV15HP. On the other hand, at 12.5hz, FV25 is indeed higher by 6.9db over FV15HP based on CEA-2010 passing numbers.
You do what you think is appropriate, but I'm not thinking that will be necessary.

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post #36609 of 40624 Old 01-02-2019, 08:34 PM
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Originally Posted by Soulburner View Post
As a customer, I want to know how much bang I'm getting for my dollars. Don't tell me that having accurate product information wouldn't be of benefit . This all matters because if the numbers go one way, one sub would be the better purchase. But if they go another way, another one becomes the better purchase from an output per dollar perspective. I've put together a helpful spreadsheet that arranges all the subs in relation to each other in the same way as Rythmik, but also includes how much output you get per dollar. At this point my confidence in some of the numbers is not great due to the problems reconciling with data-bass. So if Rythmik's site is more accurate, all we need is the 20Hz output of one sub and we can line up the rest of the range. Due to the aforementioned problem, we have to be very careful pulling such a number from data-bass. That is why I set out to determine which statistic was more believable. I need to make sure that the basis for the comparison is accurate.

EDIT: Rythmik clarified below, which corroborates what Schrodinger was saying yesterday.
Ok, I'll play along. I will grant you that many customers like to know bang for their buck. I know I do and many other do but that is literally only one aspect of purchasing a sub. Let's think about the others: size, weight, finish, sealed, ported, SQ, maximum price, minimum price, TR, brand loyalty, new, used, max extension, max spl, subs for music, subs for movies.......and those are just the few things I can name off the top of my head.

I half way see what you are getting at, and if output per dollar is your top priority then the most accurate numbers are your thing. Just because it's your thing, doesn't make it "the" thing. Maybe I'm wrong in saying this but it seems if you are looking for perfect numbers.........and those don't exist, remember variables. Did you consider that Rythmik and Databass may not have the exact same equipment? I honestly don't know, I'm speculating.

As I see it, Rythmik and Databass both have excellent reputations and I would wager their numbers are pretty accurate......but not perfect. They probably will not match exactly as you would like but likely are within tolerance of the variables that go into testing. Therefore, I believe it is unfair for you to assume there is a problem with Databass and I think it's unfair to assume there is a production problem with Rythmik. Those are unfounded accusations. Now, if all of a sudden Rythmik had a production issue or Databass all of a sudden found some glaring issue with their process then I would expect they would correct the problem. People have already posted that there can be variances when testing but you seem to be unwilling to accept that there could be a difference.

I'm sorry if I am coming off harsh, damn it I'm breaking another resolution, but I re-read that you are considering new subs from Rythmik and going from sealed to ported. Not sure what you are looking for, but hey, we all like bigger, badder, louder subs. so go ahead and get them. I wouldn't worry so much about a 1.5 dB difference which you would be hard pressed to notice anyway. I would imagine the 15" will be plenty loud enough while still playing super clean and tight.

Todd
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post #36610 of 40624 Old 01-02-2019, 08:40 PM
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Is the FVX15 available with a silver cone or is that only the the FV15HP?
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post #36611 of 40624 Old 01-02-2019, 08:58 PM
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Quote:
Originally Posted by enricoclaudio View Post
Did you know that a Type 2/Class 2 SPL meter, even the most expensive ones like my $1500 Casella CEL-620 have an accuracy of +/- 1.5dB? If you take in count differences in software, ambient temperature, mic models, wind, external noise, you name it .... a difference of 1.7dB is totally acceptable and even inside the ANSI and IEC 651 Type 2/Class 2 accuracy standards. In fact, that difference is even inside the Class 1/Type 1 accuracy standards. The lower the frequency, the higher the tolerance goes up. For instance, at 20Hz, the tolerances are +/-2.5dB for Class 1 and +/- 3.5dB for Class 2.
+1

Outdoor measurements are an imperfect science and as such there are variations inherent to the results.

Tests on different model subwoofers done back-to-back using the exact same everything - ambient noise, heat, humidity, mic, software, etc. - are an effective way to establish a solid baseline for those specific products. Change any of those elements however and minor discrepancies are inevitable. Even with everything equalized two of the exact same model subwoofer would likely measure slight differences due to +/- component tolerances for the amp and driver(s). You can account for environmental differences measuring in an anechoic chamber but that still leaves manufacturing tolerances to contend with, something which is unavoidable and can't be factored out of the equation.
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post #36612 of 40624 Old 01-02-2019, 09:51 PM
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^^^
I didn't want to bring those factors in when I posted earlier. Indeed, there are a couple of factors that affect the SPL numbers.

Imagine when as a vendor sending in a sub to Josh to test and the numbers are not as expected, we all begin to brainstorm what can affect the SPL measurement results. Each of us can come up with a list of factors. Temperature of the voice coil is one factor even though it is not uniform across frequencies. The other is the wall power voltage. Higher wall power voltage gives higher SPL reading. Stepping is another (the measurement has to increment in a way to find out the "exact" max output). Is it in 0.5db increment, or 1db increment? Is some test just lucky to land on the exact max SPL point vs another? Each run at close to max amplifier output can heat up the voice coil further (unless Josh pause enough time to let the voice coil cool down). As a result, if Josh repeats the same test multiple times in a short period of time, the reading can become just a bit lower, instead of higher. Again, that is just my list. I hope I don't muddy the water any further :-)
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post #36613 of 40624 Old 01-03-2019, 01:38 AM
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Well this has been a useful exercise. As stated above, we've landed on a couple of measurements that seem most reliable - FV25HP and F18. We have an explanation for the FV15HP. We do not have one for the FV18, so we're going to have to chalk that one up to sample and/or measurement variation and call it a fluke as it shouldn't be that close to FV25HP. So based on this we can scale the rest using Rythmik's own relative performance chart, and expand it to include even more information. It's useful to me. Maybe it is to you, too. Or, I'm just an analytical nerd who devotes too much time to this stuff. Thank you everyone for your patience and input.

And Brian, I don't think you need to adjust the FV25HP! I think things line up pretty well now.

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Notes:
• I didn't include FM8, L12 white, F12SE, or any other minor variation of the same sub.
• These charts only speak in terms of 20Hz performance and cost - nothing else. Desired max extension, finish options, and other considerations are a personal decision.
• FVX15 output was adjusted to be -2.5dB from FV15HP based on its product page instead of the main page figure of -3dB.
• Output figures of 2 subs at 20Hz is only valid if placed within a maximum of 14 feet of each other. If placed further apart, you will see +3dB instead of +6dB gain at 20Hz because you will lose acoustic coupling.
• The L series generally has the highest bang for the buck - because it forgoes some of the bass extension, finish options, and amp controls of the F series.
• All models increase in performance per dollar when buying duals - except for F8 and F12-300, because those models do not have a multi-sub discount, or the discount is currently extended to a single sub purchase.
• I can share the formulas if anyone is curious.
• Please let me know of any mistakes.

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post #36614 of 40624 Old 01-03-2019, 09:31 AM
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Nice work on this. I’ve followed the conversation above and see the potential variances.. which is fine, doesn’t bother me and it’s nice to see the general price/performance ration.. So a quick note on that. Your first revision many posts ago was useful as my buddy was looking to upgrade his sub.. I recently purchased the G25HPSE’s and am continually impressed by them.. but his budget wasn’t nearly as large as mine. I remembered your chart and had steered him to the L22... (first Rythmik sub for him also) he made the purchase and now sends me texts once a week to tell me how great the subwoofer is and he’s over the moon with the price/performance and plans to pick up 2 more in near future for another room. So kudo’s for your efforts, they are appreciated.
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post #36615 of 40624 Old 01-03-2019, 09:48 AM
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OSHA requires much tighter calibration but adding that calibration can easily add $100 or more to the cost of the meter, and OSHA only really cares about A weighting. See e.g. this excerpt from their technical manual: https://www.osha.gov/dts/osta/otm/new_noise/#noiseeval

Note temperature can affect the readings as well.

Price/performance can be hard to nail down... Output/dollar is one metric but may not capture the "performance" another listener desires. For instance, while one person may go for maximum output, another may sacrifice SPL/dollar to buy a bigger sub with higher power that provides lower distortion at a given output level, whilst another may buy four smaller subs to better smooth in-room response for the price of two larger subs (that'd be me). Etc.
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post #36616 of 40624 Old 01-03-2019, 11:08 AM
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Does Rythmik do kits for the F18? I don't see it on the website.
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post #36617 of 40624 Old 01-03-2019, 11:46 AM
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Price/performance can be hard to nail down... Output/dollar is one metric but may not capture the "performance" another listener desires. For instance, while one person may go for maximum output, another may sacrifice SPL/dollar to buy a bigger sub with higher power that provides lower distortion at a given output level, whilst another may buy four smaller subs to better smooth in-room response for the price of two larger subs (that'd be me). Etc.
That’s a good point.. one I’ll comment on as well. Despite the G25HP looking like a lack luster value in comparison to output/dollar it is so far from that in terms of satisfaction of performance with a quality, depth and controlled authority to the lowest frequencies that is ever satisfying in my space.. and I havnt had the opportunity to even umik/REW/MiniDSP then yet .. but thats happening next week. Looking forward to having the house to myself and lighting them up all week.
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post #36618 of 40624 Old 01-03-2019, 12:45 PM
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Does Rythmik do kits for the F18? I don't see it on the website.
Yes they do but you'll have to contact them for pricing and such. AFAIK it is not on the website, as you point out.

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post #36619 of 40624 Old 01-03-2019, 12:48 PM
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Quote:
Originally Posted by DonH50 View Post
Price/performance can be hard to nail down... Output/dollar is one metric but may not capture the "performance" another listener desires. For instance, while one person may go for maximum output, another may sacrifice SPL/dollar to buy a bigger sub with higher power that provides lower distortion at a given output level, whilst another may buy four smaller subs to better smooth in-room response for the price of two larger subs (that'd be me). Etc.
This is all quite true. It's also worth noting that there's nothing magical about the 20hz spot on the audio spectrum. It's as good a benchmark as any to address the scenario I suspect is most often encountered, which is, which subwoofer will be most impactful for movies in my open floor plan/mixed use living space?

If you have a sealed room or dedicated theater, and are interested in full bandwidth reproduction, or if your interests are music only and midbass is your thing, then you would want a different benchmark, and would most likely find the value proposition of sealed subs (and the dual driver configurations in particular) to be greater than what is represented using 20hz output as your benchmark.
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post #36620 of 40624 Old 01-03-2019, 01:18 PM
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Originally Posted by Blacklightning View Post
Does Rythmik do kits for the F18? I don't see it on the website.
At this time last year, the F18 kits were $990 each shipped.

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post #36621 of 40624 Old 01-03-2019, 02:11 PM
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Yes they do but you'll have to contact them for pricing and such. AFAIK it is not on the website, as you point out.

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Great. I'm wondering if Shipping will be a lot less since I'm in Canada. Now I need to see if a cabinet maker will be the same price or cheap than getting it directly from Rythmik. Plus I will be able to make the box larger as it seems the F18 is made small the same way the F15 was.

Hope I can get some plans from Rythmik or Salk as I might as well go Big and Heavy.
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post #36622 of 40624 Old 01-03-2019, 02:22 PM
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Quote:
Originally Posted by Blacklightning View Post
Great. I'm wondering if Shipping will be a lot less since I'm in Canada. Now I need to see if a cabinet maker will be the same price or cheap than getting it directly from Rythmik. Plus I will be able to make the box larger as it seems the F18 is made small the same way the F15 was.

Hope I can get some plans from Rythmik or Salk as I might as well go Big and Heavy.
Back when I was considering building a couple F18, I got the plans from Brian Ding and asked him if it would be beneficial to make the box bigger than the production unit, as I remembered there was a bit of efficiency to be gained by building an F15 box a little bigger. He responded that he felt the production F18 box was the ideal size.

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post #36623 of 40624 Old 01-03-2019, 02:38 PM
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post #36624 of 40624 Old 01-03-2019, 03:26 PM
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off-topic but why does avsforum allow hotlinking images to imgflip (seen above in the post by @Blacklightning ), but not the most popular image hosting site imgur? does avsforum have beef with imgur or something?
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post #36625 of 40624 Old 01-03-2019, 03:37 PM
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post #36626 of 40624 Old 01-03-2019, 03:38 PM
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no problem w/imgur or anywhere for me

Power: Marantz sr7008, NAD C 275Bee x 2, Video: Oppo 103, Samsung 75un6300
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post #36627 of 40624 Old 01-03-2019, 03:44 PM
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Quote:
Originally Posted by Blacklightning View Post
Well, he openly did not feel that way about the F15 box, and recommended a 4 cu ft internal volume for it instead of the 3 cu ft in the production enclosure. But hey, if you want to risk over excursion of the driver by installing it in an oversized enclosure . . .

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post #36628 of 40624 Old 01-03-2019, 04:28 PM
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Quote:
Originally Posted by bkeeler10 View Post
Well, he openly did not feel that way about the F15 box, and recommended a 4 cu ft internal volume for it instead of the 3 cu ft in the production enclosure. But hey, if you want to risk over excursion of the driver by installing it in an oversized enclosure . . .

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I'm not trying to start anything and I'm sure the different will be small or null.

BUT.

The Production F15 is 7220 Inch cubed Vs the DIY F15 is 9591.75 Inch Cubed
The Production F18 is 8825.25 Inch Cubed so I figured the DIY F18 would be

and I think Salk's F15 are even bigger at 11,934.

I know my math is off as I'm using the outside dimensions and not removing the brace volume but I know size is a big thing when it comes to shipping so I figured Rythmik would keep the production small but provide a larger plan for DIY.
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post #36629 of 40624 Old 01-03-2019, 04:50 PM
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no problem w/imgur or anywhere for me
oh interesting, last time i tried it didn't work. good to know.
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post #36630 of 40624 Old 01-03-2019, 07:50 PM
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Quote:
Originally Posted by Blacklightning View Post
I'm not trying to start anything and I'm sure the different will be small or null.

BUT.

The Production F15 is 7220 Inch cubed Vs the DIY F15 is 9591.75 Inch Cubed
The Production F18 is 8825.25 Inch Cubed so I figured the DIY F18 would be <elided>
and I think Salk's F15 are even bigger at 11,934.

I know my math is off as I'm using the outside dimensions and not removing the brace volume but I know size is a big thing when it comes to shipping so I figured Rythmik would keep the production small but provide a larger plan for DIY.
Why would Brian dissemble about the volume? There were good reasons for the smaller volume of the F15 at the time, and now the F18 needs to be drop-shipped so volume is less an issue.

You could get a speaker design program, enter all the T-S parameters, see if you can get the servo characteristics, and roll your own of any size you desire.

Or you could trust Dr. Brian Ding's analysis...
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