Official Rythmik Audio Subwoofer thread - Page 533 - AVS Forum
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Subwoofers, Bass, and Transducers > Official Rythmik Audio Subwoofer thread
rak306's Avatar rak306 11:38 AM 06-14-2014
Quote:
Originally Posted by Rythmik View Post

.... The difference of these mass difference is very subtle and yet look at all the speaeker measurement with noisy background and poor resolution. That is why we keep going back to the same conclusion -- there is no difference.

Brian,

I am not following what you are saying here. Is it that people don't make good measurements, and wrongly conclude there is no difference in speakers with different mass?

As I see it, the math models of speakers (TS parameters) assume away the non-linearities. As a result, all speakers have the same damped harmonic solution - with the only difference being the Qs (electrical and mechanical), resonant frequency, size, and power handling. And one can equalize them all to be the same. So one might conclude that all similar speakers can be made to sound the same (which is non-sense).

Left out of many speaker specifications are distortion measurements.

IMO all speakers specification should include distortion vs frequency curves with inputs at 0 dB (re rated output), -6 dB, -10 dB, for various input frequencies (e.g. 1/2fo, fo, 2fo).

This would be very telling. Transistors, A/D converters, power amplifiers, all include distortion measurements - why don't speakers? Is it because they are not very good (like 3%-10%)?

rcohen's Avatar rcohen 02:29 PM 06-14-2014
Quote:
Originally Posted by rak306 View Post
Quote:
Originally Posted by Rythmik View Post

.... The difference of these mass difference is very subtle and yet look at all the speaeker measurement with noisy background and poor resolution. That is why we keep going back to the same conclusion -- there is no difference.

Brian,

I am not following what you are saying here. Is it that people don't make good measurements, and wrongly conclude there is no difference in speakers with different mass?

As I see it, the math models of speakers (TS parameters) assume away the non-linearities. As a result, all speakers have the same damped harmonic solution - with the only difference being the Qs (electrical and mechanical), resonant frequency, size, and power handling. And one can equalize them all to be the same. So one might conclude that all similar speakers can be made to sound the same (which is non-sense).

Left out of many speaker specifications are distortion measurements.

IMO all speakers specification should include distortion vs frequency curves with inputs at 0 dB (re rated output), -6 dB, -10 dB, for various input frequencies (e.g. 1/2fo, fo, 2fo).

This would be very telling. Transistors, A/D converters, power amplifiers, all include distortion measurements - why don't speakers? Is it because they are not very good (like 3%-10%)?
I would be really interested to see an article or discussion on the differences (pros, cons) between using feedback (amp and/or servo) versus using signal processing to correct for speaker distortion.
DonH50's Avatar DonH50 02:35 PM 06-14-2014
My off-the-cuff comments not to be confused with Brian's thoughts: In general the earlier in the chain you correct the errors the easier they are to fix. DSP correction requires a very accurate speaker/driver model that will likely get blown out by interaction with the room anyway, or an acoustic sense and feedback scheme that is difficult to implement cleanly and make stable. I've used analog and digital signal processing to correct errors from various components in an RF chain, no reason to think it would be much different for audio. In some ways much harder if you try acoustic sensors, the loop delay is a killer.

Many years ago I built a servo sub using a dual voice-coil woofer and compared it to non-servo and the best subs of the time (mid-80's, Velodyne, many passive designs up to and including a pair of Hartley's in an HQD system). The results sold me on servo and I've been there ever since.

IME/IMO - Don
rak306's Avatar rak306 04:45 PM 06-14-2014
Quote:
Originally Posted by DonH50 View Post
My off-the-cuff comments not to be confused with Brian's thoughts: In general the earlier in the chain you correct the errors the easier they are to fix. DSP correction requires a very accurate speaker/driver model that will likely get blown out by interaction with the room anyway, or an acoustic sense and feedback scheme that is difficult to implement cleanly and make stable. I've used analog and digital signal processing to correct errors from various components in an RF chain, no reason to think it would be much different for audio. In some ways much harder if you try acoustic sensors, the loop delay is a killer.
...

IME/IMO - Don
Yes loop delay is a bad thing, but only if you are trying to correct errors at a higher closed loop bandwidth than the loop can support (like you trying to control your room temp. by constantly tweaking the thermostat and not waiting long enough to know what the changes in temp setting did to the room temp - you end up with an oscillation).

I don't think there is very much feedback signal delay in Brian's servo loop. The feedback signal is from the sensor coil (in the speaker coil assembly) driving a cable a few inches going to an OP amp.

To me, the key to a servo solution working is an accurate feedback sensor. If the sensor is not accurate - the servo will not be accurate.

A source of non-linearity in a speaker is a variable BL depending on coil position in the gap. It seems to me that would also affect the feedback sense coil. Non the less, I think the servo drives are the way to go - I have 2 of Brian's dual 8" kits, and I love them.
DonH50's Avatar DonH50 11:03 PM 06-14-2014
The loop delay problem I mentioned was with acoustic sensors, which can add 10's of us to ms (or 10's of ms for a mic at the listener's position) delay. As I said, I used a similar servo loop ages ago and agree that such a design can be readily stabilized.

Brian discussed the BL impact at one point; I'm sure he'd be willing to do so again if the post is not easy to find (I did not look tonight -- tired, and this is a big thread!)

I have designed amplifiers and data converter circuits for VHF through W band. I am very familiar with trying to deal with loop delay, and the problem of explaining why an amplifier is a great oscillator...
rak306's Avatar rak306 03:35 PM 06-15-2014
Quote:
Originally Posted by DonH50 View Post

...
Brian discussed the BL impact at one point; I'm sure he'd be willing to do so again if the post is not easy to find (I did not look tonight -- tired, and this is a big thread!)
...
I would be interested - if you can find it.

I tried to read this entire thread awhile ago - but I gave up. Then I resorted to searching only on posts from user "Rythmik". Even that list was huge.
JT78681's Avatar JT78681 07:43 AM 06-16-2014
So I've been running my FV15HP's in 1 port mode 3db hot <60hz, 14hz/high dampening (using PEQ on amp) for a few days now. I think I have finally found the right combination of settings that I will stick with for a while. I feel like the subs aren't being over worked and retain their composure throughout the entire frequency range. It's simply tight and controlled, but punishing down low. I can only imagine what you guys with dedicated theater rooms are experiencing.
Rythmik's Avatar Rythmik 09:35 AM 06-16-2014
Quote:
Originally Posted by rak306 View Post
Quote:
Originally Posted by DonH50 View Post

...
Brian discussed the BL impact at one point; I'm sure he'd be willing to do so again if the post is not easy to find (I did not look tonight -- tired, and this is a big thread!)
...

I would be interested - if you can find it.

I tried to read this entire thread awhile ago - but I gave up. Then I resorted to searching only on posts from user "Rythmik". Even that list was huge.

Our sensing coil indeed has some special design features which you can understand I don't want elaborate here. The BL profile of sensing coil is different from the BL profile of the driver coil. One MIT student bought a driver from us to finish his undergraduate thesis. He already has a better head start than others as that is a significant improvement over a regular dual voice coil driver (sorry Don, I have to point this out BTW, I also started with a dual voice driver)


-
Rythmik's Avatar Rythmik 09:52 AM 06-16-2014
Quote:
Originally Posted by rak306 View Post
Non the less, I think the servo drives are the way to go - I have 2 of Brian's dual 8" kits, and I love them.

We do plan to make those as regular finished products. We will have two flavors: F8 and M8. They share basically same driver/enclosure/amp. However, in F8, there are 3 extension setting whereas in M8, one of the extension setting is designated as 50hz/24 so that it can be used as a midbass module.


Some customers have asked where we are for the FV15 replacement? To make long story short, we decide to offer the follow new models by Thanksgiving:
1) FVX15 (DS1502 aluminum driver + HX405 amp). This has the same enclosure size as FV15HP. But the new amp without PEQ control can make it more affordable. The price should be around $999, plus $140 shipping. In terms of compromise over FV15HP other than driver and PEQ, the extension setting will have 1port music, 1port HT, and 2port. There will be no independent damping and extension filter control.
2) FVX12(DS1204 aluminum driver + HX405 amp). This model has a smaller enclosure (20"H x 17" W, 22" D without grille, grille and amp control add 2"). The price is to be determined, but my goal is around $900 including shipping. It has dual tune feature similar to FVX15.


Both this models should fill up the big pricing jump we have from LV12R to FV15HP. If the pricing pressure is too much, we may even consider LVX12 (which use less expensive paper cone driver) and by doing that we can drop price by another $100.


For sealed subs, we also have L12 in the work (300WRMS amp driving 14" cube) and other models... Stay tuned.
tvuong's Avatar tvuong 10:01 AM 06-16-2014
So the fv15hp will still be the top of the ported? Fvx15 should have similar FR as the Fv15hp? What about the F25hp?
Rythmik's Avatar Rythmik 10:19 AM 06-16-2014
Quote:
Originally Posted by tvuong View Post
So the fv15hp will still be the top of the ported?
I know where you are going. I am not going to make fridge size subwoofers. Maybe DIY can do that in their garage

Quote:
Originally Posted by tvuong View Post
Fvx15 should have similar FR as the Fv15hp? What about the F25hp?

FVX15 scale with FV15HP pretty well. So customers will have same FR as FV15HP.


F25HP is still in the work with my contractor engineer. That one has the most uncertainty. Hope everything turns out as I have calculated.


-
tvuong's Avatar tvuong 10:41 AM 06-16-2014
Quote:
Originally Posted by Rythmik View Post
Quote:
Originally Posted by tvuong View Post
So the fv15hp will still be the top of the ported?
I know where you are going. I am not going to make frig size subwoofers. Maybe DIY can do that in their garage
No, I am happy to still own a pair of the top dog Rythmik ported sub . The FV15hp is just the right size for its performance. I know I am all set for subs for the longest time unless I want more which I do not see, then a fridge size DIY will be it.
The FVX will be a great value sub.
DonH50's Avatar DonH50 12:33 PM 06-16-2014
[quote=Rythmik;25006050]
Quote:
Originally Posted by rak306 View Post
Our sensing coil indeed has some special design features which you can understand I don't want elaborate here. The BL profile of sensing coil is different from the BL profile of the driver coil. One MIT student bought a driver from us to finish his undergraduate thesis. He already has a better head start than others as that is a significant improvement over a regular dual voice coil driver (sorry Don, I have to point this out BTW, I also started with a dual voice driver)-
No apologies due me, Brian! My work was almost 30 years ago and I am glad to see people like you have taken it so much further! And glad I am one of the ones reaping the results.

For the record, the woofer I used also had different BL curves for each coil, but I used a simple LDI control loop and did not carry the idea nearly as far as Brian has. Of course, I was an undergrad student at the time, and Brian has a PhD plus lots of experience with control systems.

No worries - Don
Blacklightning's Avatar Blacklightning 03:33 PM 06-16-2014
[quote=Rythmik;25006506]
Quote:
Originally Posted by rak306 View Post
For sealed subs, we also have L12 in the work (300WRMS amp driving 14" cube) and other models... Stay tuned.
You have talked about this model before.
I would love to see this but there seems to be a lot of Models.

Sealed subs seem to be less popular and I can't see many people picking the L12 over the LV12 if the price is around the same. Another brand has a sealed and ported option in the same price range and most people recommend the ported version even for Music as both are clean.
dragonleepenn's Avatar dragonleepenn 04:35 PM 06-16-2014

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Rythmik's Avatar Rythmik 07:32 PM 06-16-2014
Quote:
Originally Posted by Blacklightning View Post
Quote:
Originally Posted by Rythmik View Post

You have talked about this model before.
I would love to see this but there seems to be a lot of Models.

Sealed subs seem to be less popular and I can't see many people picking the L12 over the LV12 if the price is around the same. Another brand has a sealed and ported option in the same price range and most people recommend the ported version even for Music as both are clean.

Black, I appreciate your feedback. This is thetype of feedback we really want to hear.

L12 will be our standard overseas "postal shipping" subwoofer. It is the first sub that is truly able to ship via postal office. In addition, our F12 is still a very popular model (but pricy)which means there are sealed sub die-hard customers who are willing to sacrificea bit in output. L12 entry servo sealed sub will serve that market well. Mostthe recommendations on AVS forum are based on HT-centric application.

We will also have other derivative products following L12. Your feedback on L12 allows us to adjust the qty mix.


-
grasshoppers's Avatar grasshoppers 08:41 PM 06-16-2014
[quote=Rythmik;25023250]
Quote:
Originally Posted by Blacklightning View Post

Black, I appreciate your feedback. This is thetype of feedback we really want to hear.

L12 will be our standard overseas "postal shipping" subwoofer. It is the first sub that is truly able to ship via postal office. In addition, our F12 is still a very popular model (but pricy)which means there are sealed sub die-hard customers who are willing to sacrificea bit in output. L12 entry servo sealed sub will serve that market well. Mostthe recommendations on AVS forum are based on HT-centric application.

We will also have other derivative products following L12. Your feedback on L12 allows us to adjust the qty mix.


-
I have been waiting very patiently for the L12 sealed sub.
Let me know when you plan on releasing them and I will
Happily be one of the first to order.
3db's Avatar 3db 07:50 AM 06-17-2014
[quote=grasshoppers;25024922]
Quote:
Originally Posted by Rythmik View Post

I have been waiting very patiently for the L12 sealed sub.
Let me know when you plan on releasing them and I will
Happily be one of the first to order.
I have to ask, the LV12 is the ported version and identical to the LV12-R? I would choose ported over sealed anyday from the Rythmik family. I have my LV12-R sub configured for maximum extension and its extremely tight for music. I do not detect any kind of boom or sloppyness in its output.
enricoclaudio's Avatar enricoclaudio 08:02 AM 06-17-2014
[quote=3db;25032058]
Quote:
Originally Posted by grasshoppers View Post


I have to ask, the LV12 is the ported version and identical to the LV12-R? I would choose ported over sealed anyday from the Rythmik family. I have my LV12-R sub configured for maximum extension and its extremely tight for music. I do not detect any kind of boom or sloppyness in its output.
The LV12 is the same LV12R. Sometimes we forget to put the R at the end. The FV12 (port on the front) was the previous 12" ported subwoofer but we replaced it with the LV12R. The L12 will be the sealed version of the LV12R.
JT78681's Avatar JT78681 08:05 AM 06-17-2014
[quote=3db;25032058]
Quote:
Originally Posted by grasshoppers View Post


I have to ask, the LV12 is the ported version and identical to the LV12-R? I would choose ported over sealed anyday from the Rythmik family. I have my LV12-R sub configured for maximum extension and its extremely tight for music. I do not detect any kind of boom or sloppyness in its output.
And this is why it's recommended so often. I don't think anything can beat it in the $600 dollar price range.
eljaycanuck's Avatar eljaycanuck 10:53 AM 06-17-2014
Quote:
Originally Posted by Rythmik
... we decide to offer the follow new models by Thanksgiving:
1) FVX15 (DS1502 aluminum driver + HX405 amp). This has the same enclosure size as FV15HP.
. . .
FVX15 scale with FV15HP pretty well. So customers will have same FR as FV15HP.
The FVX15 sounds intriguing! Although its FR is expected to be the same as the FV15HP's, output will likely be less. What are the "guesstimates" of how its output will compare?

Thanks!
ahmedreda's Avatar ahmedreda 01:12 PM 06-17-2014
This is purely a guess but I would think around 3db less accross the board.
Quote:
Originally Posted by eljaycanuck View Post
The FVX15 sounds intriguing! Although its FR is expected to be the same as the FV15HP's, output will likely be less. What are the "guesstimates" of how its output will compare?

Thanks!

JT78681's Avatar JT78681 01:27 PM 06-17-2014
Quote:
Originally Posted by Rythmik View Post
We do plan to make those as regular finished products. We will have two flavors: F8 and M8. They share basically same driver/enclosure/amp. However, in F8, there are 3 extension setting whereas in M8, one of the extension setting is designated as 50hz/24 so that it can be used as a midbass module.


Some customers have asked where we are for the FV15 replacement? To make long story short, we decide to offer the follow new models by Thanksgiving:
1) FVX15 (DS1502 aluminum driver + HX405 amp). This has the same enclosure size as FV15HP. But the new amp without PEQ control can make it more affordable. The price should be around $999, plus $140 shipping. In terms of compromise over FV15HP other than driver and PEQ, the extension setting will have 1port music, 1port HT, and 2port. There will be no independent damping and extension filter control.
2) FVX12(DS1204 aluminum driver + HX405 amp). This model has a smaller enclosure (20"H x 17" W, 22" D without grille, grille and amp control add 2"). The price is to be determined, but my goal is around $900 including shipping. It has dual tune feature similar to FVX15.


Both this models should fill up the big pricing jump we have from LV12R to FV15HP. If the pricing pressure is too much, we may even consider LVX12 (which use less expensive paper cone driver) and by doing that we can drop price by another $100.


For sealed subs, we also have L12 in the work (300WRMS amp driving 14" cube) and other models... Stay tuned.
Brian,

Can you tell us what you are expecting the wattage to be on the HX405 amp? Also, will the FVX12 look like a smaller version of the FV15HP?
JT78681's Avatar JT78681 01:42 PM 06-17-2014
Quote:
Originally Posted by ahmedreda View Post
This is purely a guess but I would think around 3db less accross the board.
I like your setup! This makes me want to add a third FV15HP nearfield. Right now I have two up front and I'm more than satisfied, but hey you can't ever have too much bass.
enricoclaudio's Avatar enricoclaudio 03:59 PM 06-17-2014
Quote:
Originally Posted by ahmedreda View Post
This is purely a guess but I would think around 3db less accross the board.
According to Brian the output on this subwoofer will be -3dB less across the board compared with the FV15HP.
tvuong's Avatar tvuong 04:01 PM 06-17-2014
^^ good to know.
enricoclaudio's Avatar enricoclaudio 04:02 PM 06-17-2014
Quote:
Originally Posted by JT78681 View Post
Brian,

Can you tell us what you are expecting the wattage to be on the HX405 amp? Also, will the FVX12 look like a smaller version of the FV15HP?
The HX405 is a 400 watts Hypex amplifier.
Eldave's Avatar Eldave 07:22 PM 06-17-2014
I too am interested in the L12. Will it have the same output as the F12?
enricoclaudio's Avatar enricoclaudio 07:32 PM 06-17-2014
Quote:
Originally Posted by Eldave View Post
I too am interested in the L12. Will it have the same output as the F12?
I'll let Brian chime on this but I'm pretty sure than the L12 will have less output than the F12 mostly because the size of the box (14" cube) and the power of the amp (300 WRMS).
ahmedreda's Avatar ahmedreda 07:42 PM 06-17-2014
Thank you! The third one did not add much in terms of output as much as it helped smooth a wide dip around 35-50hz. The tactile feedback improved quite a bit as well. If you have a smooth response and you get decent tactile response, you should be good as long as your subs can handle your current listening levels.
Quote:
Originally Posted by JT78681 View Post
I like your setup! This makes me want to add a third FV15HP nearfield. Right now I have two up front and I'm more than satisfied, but hey you can't ever have too much bass.

Tags: Rythmik , Rythmik Audio , Rythmik Audio F12 Direct Servo Subwoofer , Rythmik Audio F15 Subwoofer
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