RBH Sound 21" Monster 4kwatt Sub First to Meet our Maximus Bassaholic Rating!

[gene]

Yes, a ported sub with that driver, would likely be huge. Have RBH tested that sub to full power out of doors? I ask, as I think there is a serious risk that sub could produce a sonic boom. That could do a lot of damage. This phenomenon has occurred with people experimenting with devices like that. If they have not, they had better test it in open space. If it is possible someone will do it, and the law suits will come in.

I do find it hard to justify such a device in the home. I suppose it might be required for the odd effect, in a movie. However it has no practical application for any music I am aware of. I certainly never felt the need for increased bass output in my system and have at times in movies been concerned about structural damage. So I think this unit probably does get into the pointless realm. I could see that it might have an application in large cinemas, but not in any home I am aware of.

Not sure to what extent RBH swept this sub at power at infrasonic frequencies. I know they did run 4kwatts of power to torture the driver and it stood up to it. That's insane! They do have a ported version being installed in an extremely upscale theater system in Orlando we hope to cover in the near future. So far my family complains when I crank up deep bass tracks with the 21" sub engaged despite my sound isolation in my theater room. I rarely heard complaints from them before I installed the 21". It's like my walls don't exist anymore. LOL

 

[TLS Guy]

Not sure to what extent RBH swept this sub at power at infrasonic frequencies. I know they did run 4kwatts of power to torture the driver and it stood up to it. That's insane! They do have a ported version being installed in an extremely upscale theater system in Orlando we hope to cover in the near future. So far my family complains when I crank up deep bass tracks with the 21" sub engaged despite my sound isolation in my theater room. I rarely heard complaints from them before I installed the 21". It's like my walls don't exist anymore. LOL

Gene, I learned about this problem from Bob Carver. He told me he had done this in his lab. He calculated that the pressure changes in a small sealed box could mimic the physical pressure changes of a sonic boom. He told me he did it, and proved his calculation correct. I would bet most speaker designers are oblivious to this possibility. I would not have thought of it personally and I doubt most speaker designers would. I advise RBH investigate that sub for this potential.

 

[Mr._Clark]

I ran across a few papers about vibroacoustic disease. Based on my very brief scan, it's not clear to me what exposure levels would be required to put someone at risk. Perhaps @TLS Guy would be willing to weigh in?

Vibroacoustic disease - PubMed

Vibroacoustic disease (VAD) is a whole-body, systemic pathology, characterized by the abnormal proliferation of extra-cellular matrices, and caused by excessive exposure to low frequency noise (LFN). VAD has been observed in LFN-exposed professionals, such as, aircraft technicians, commercial...

pubmed.ncbi.nlm.nih.gov

 

[Danzilla31]

Not sure to what extent RBH swept this sub at power at infrasonic frequencies. I know they did run 4kwatts of power to torture the driver and it stood up to it. That's insane! They do have a ported version being installed in an extremely upscale theater system in Orlando we hope to cover in the near future. So far my family complains when I crank up deep bass tracks with the 21" sub engaged despite my sound isolation in my theater room. I rarely heard complaints from them before I installed the 21". It's like my walls don't exist anymore. LOL

Gene how easy was it for you to integrate this sub since it's a sealed design with your ported subs in that room? Is that something you can tell us about or do you plan to put that in the article? People always hear that your not recommended to do this but I know some people that do in they're rooms. I'm curious how you were able to make it work

 

[Danzilla31]

Gene, I learned about this problem from Bob Carver. He told me he had done this in his lab. He calculated that the pressure changes in a small sealed box could mimic the physical pressure changes of a sonic boom. He told me he did it, and proved his calculation correct. I would bet most speaker designers are oblivious to this possibility. I would not have thought of it personally and I doubt most speaker designers would. I advise RBH investigate that sub for this potential.

I know that it's a valid health concern your asking about but I cant help but look at the funny part of it. A sub that can produce a sonic boom!
Hell of an advertisement right there

 

[Danzilla31]

Not sure to what extent RBH swept this sub at power at infrasonic frequencies. I know they did run 4kwatts of power to torture the driver and it stood up to it. That's insane! They do have a ported version being installed in an extremely upscale theater system in Orlando we hope to cover in the near future. So far my family complains when I crank up deep bass tracks with the 21" sub engaged despite my sound isolation in my theater room. I rarely heard complaints from them before I installed the 21". It's like my walls don't exist anymore. LOL

I bet the ported version is MASSIVE

 

[TLS Guy]

I know that it's a valid health concern your asking about but I cant help but look at the funny part of it. A sub that can produce a sonic boom!
Hell of an advertisement right there

That is not quite what happened. It reproduced the physics of the sonic boom in the sub and destroyed it. Bob used a small unit to test his theory. If this sub met that criteria it would be a very dangerous life threatening event and not a joke. Not a good advertisement at all!

 

[TLS Guy]

I ran across a few papers about vibroacoustic disease. Based on my very brief scan, it's not clear to me what exposure levels would be required to put someone at risk. Perhaps @TLS Guy would be willing to weigh in?

Vibroacoustic disease - PubMed

Vibroacoustic disease (VAD) is a whole-body, systemic pathology, characterized by the abnormal proliferation of extra-cellular matrices, and caused by excessive exposure to low frequency noise (LFN). VAD has been observed in LFN-exposed professionals, such as, aircraft technicians, commercial...

pubmed.ncbi.nlm.nih.gov

Yes, we concentrate on spl, but the damage from excess low frequency vibrations are an evolving research topic as you found out. I think there is quite enough data already to be very concerned about it. I would say that RBH sub should NOT go into production. I would advise any professional installer not to install that sub for liability and health issues.

I have been concerned about this in my own system. As you know I don't use sub drivers, but I do have those large lines that really make an acoustic coupling to the room. They also measure much lower than predicted. I suspect the room plays a part on this, but not all of it.

Now the only musical instrument that produces frequencies below 20 Hz is the pipe organ. The lowest note has an F of 16 Hz. I know there is the odd organ that has stops labelled at 64 ft. but these are rare, and contrived from the physics of beat frequencies.

As you know I am an organ enthusiast, and these instruments do rattle my rib cage, and shake the floor. I don't watch a lot of movies, but I get concerned when the grandchildren rattle the furniture downstairs watching some action movies, and I intervene.

I have however had increasing concerns about LF damage to the human body, and funnily enough I did reduce the sub signal to the four drivers on the long TLs a few weeks ago.

My impression is that most systems I hear have subs too loud. I suspect a lot of members here are over woofered, and probably dangerously so.

Balance in all things is an axiom to live by, and that includes low frequencies.

 

[ryanosaur]

That is not quite what happened. It reproduced the physics of the sonic boom in the sub and destroyed it. Bob used a small unit to test his theory. If this sub met that criteria it would be a very dangerous life threatening event and not a joke. Not a good advertisement at all!

The trend with many of these Drivers is they're using not just very strong motors but also very stiff suspension to control the motor force.
One example is the Harbottle Audio/Funk Audio Drivers where their design has effectively eliminated compression at the highest output levels. The DataBass measurements done many years back on the earlier models are effectively "textbook" of what long term output should look like.
Cody at Harbottle even recommends people model his drivers to within 3mm of Xmech in order to maximixe potential performance. He does this with a guarantee of actual Xmax being a true known factor rather than being derived from 70% Bl as is often the case for modern design.
Cody's engineering philosophy is very different than others, but what what he and Nathan (Funk) have achieved is pretty special by all accounts.
Considering RBH's engineering acumen, I honestly don't think this will be a problem at all. I'm hoping we get to see a full suite of measurements a la what Ricci and Shady would usually provide. Seeing those Long Term sweeps along with distortion data will be the proof of what that puppy can do.

 

[kini]

And for the price of those I'm sure someone would rather go with another brand

I'm sure you would. and someone else that hasn't heard any of these subs would want to go with another brand they also never heard before too

All you have to do is look at the overall design and engineering of Funk and Harbottle subs and it's clear they are superior in both. But you keep pushing one of your site's sponsors. We all have to eat.

 

[TLS Guy]

The trend with many of these Drivers is they're using not just very strong motors but also very stiff suspension to control the motor force.
One example is the Harbottle Audio/Funk Audio Drivers where their design has effectively eliminated compression at the highest output levels. The DataBass measurements done many years back on the earlier models are effectively "textbook" of what long term output should look like.
Cody at Harbottle even recommends people model his drivers to within 3mm of Xmech in order to maximixe potential performance. He does this with a guarantee of actual Xmax being a true known factor rather than being derived from 70% Bl as is often the case for modern design.
Cody's engineering philosophy is very different than others, but what what he and Nathan (Funk) have achieved is pretty special by all accounts.
Considering RBH's engineering acumen, I honestly don't think this will be a problem at all. I'm hoping we get to see a full suite of measurements a la what Ricci and Shady would usually provide. Seeing those Long Term sweeps along with distortion data will be the proof of what that puppy can do.

My point is that all this is totally unnecessary and very likely unsafe. None of that is a requirement for enjoying music and video in the home. It certainly will add another layer to WAF. I would encourage those designers to study matters of much greater importance.

 

[Danzilla31]

My point is that all this is totally unnecessary and very likely unsafe. None of that is a requirement for enjoying music and video in the home. It certainly will add another layer to WAF. I would encourage those designers to study matters of much greater importance.

Yeah but I think equipment like this is going to owners that can do it just because they could. You can afford 4 of these your probably putting them in theater rooms big enough to handle them Id imagine

 

[ryanosaur]

My point is that all this is totally unnecessary

Yes.

and very likely unsafe.

With great power comes great responsibility.

None of that is a requirement for enjoying music and video in the home.

To this I agree with the exception of the ability for these designs to hopefully perform clean.

I think this is where a lot of designs begin to fail is that they don't look beyond the small signal and theoretical numbers in design and thus we find drivers incapable of performing cleanly when pushed.
Mind, not everything is about how loud [read: LOUD!] any given Driver or system cnl perform, but for those of us interested in the most faithful reproduction of sound, the shortcomings hit pretty easily when exceeding 1or 2 watts.

The responsible folk that are building out rooms with multiple Subs are doing so with the intention of greater efficiency. I know you don't agree with "more is more" (except for more-subs-equals-more-problems ), but discussion yields the theme of only needing to run their monster subs in quantity at less than half power to yield the results they desire.

Frankly, I can't say I have any desire to run some of the insane house curves many use. I've seen some arguing for +20, even! But I do like the idea of not needing to dump 188v into a Sub to get it to produce a 16Hz Low C at 70dB while running out of excursion and motor stability.

The balance point is somewhere in the middle of all this, of course. But there is a growing market segment that isn't afraid to build large and demand bigger still. These products aren't going away. Rather, I hope we see them get built better and eventually a bit less expensive. (This RBH Sub is more expensive than my first car back in '92!)

 

[Danzilla31]

All you have to do is look at the overall design and engineering of Funk and Harbottle subs and it's clear they are superior in both. But you keep pushing one of your site's sponsors. We all have to eat.

Yeah but doesn't Funk and Harbottle have levels to they're subs in performance? From what I've seen on they're web site subs that will rival this RBH are even more in price.

That's one thing I've always enjoyed about RBH they are expensive but usually products at this level of performance are. But RBH are not the most expensive out they're. And they do measure and perform well.

Also it's good to have options out there. More competition the better. And let's not forget $10,000 is MSRP. A good dealer or a regular customer may be getting a better deal then this

 

[ryanosaur]

Yeah but I think equipment like this is going to owners that can do it just because they could. You can afford 4 of these your probably putting them in theater rooms big enough to handle them Id imagine

C'mon, Zilla... You know some guy is putting 3 of these under his bed in a 12x17' bedroom!

 

[Danzilla31]

Yes.

With great power comes great responsibility.

To this I agree with the exception of the ability for these designs to hopefully perform clean.

I think this is where a lot of designs begin to fail is that they don't look beyond the small signal and theoretical numbers in design and thus we find drivers incapable of performing cleanly when pushed.
Mind, not everything is about how loud [read: LOUD!] any given Driver or system cnl perform, but for those of us interested in the most faithful reproduction of sound, the shortcomings hit pretty easily when exceeding 1or 2 watts.

The responsible folk that are building out rooms with multiple Subs are doing so with the intention of greater efficiency. I know you don't agree with "more is more" (except for more-subs-equals-more-problems ), but discussion yields the theme of only needing to run their monster subs in quantity at less than half power to yield the results they desire.

Frankly, I can't say I have any desire to run some of the insane house curves many use. I've seen some arguing for +20, even! But I do like the idea of not needing to dump 188v into a Sub to get it to produce a 16Hz Low C at 70dB while running out of excursion and motor stability.

The balance point is somewhere in the middle of all this, of course. But there is a growing market segment that isn't afraid to build large and demand bigger still. These products aren't going away. Rather, I hope we see them get built better and eventually a bit less expensive. (This RBH Sub is more expensive than my first car back in '92!)

100% Ryan. I have 4 monster subs well monster for my room size in the dual Rythmik FV18 and dual RBH SV1212 Reference. Im not buying these subs to crank them. In fact when I level match them in room I'm doing it at 66 to 68 db in room not 75. I buy them for the fact I never have to overdrive them. I can get the levels I want at lower volumes which means they last longer and so do the amps

 

[TLS Guy]

Yes.

With great power comes great responsibility.

To this I agree with the exception of the ability for these designs to hopefully perform clean.

I think this is where a lot of designs begin to fail is that they don't look beyond the small signal and theoretical numbers in design and thus we find drivers incapable of performing cleanly when pushed.
Mind, not everything is about how loud [read: LOUD!] any given Driver or system cnl perform, but for those of us interested in the most faithful reproduction of sound, the shortcomings hit pretty easily when exceeding 1or 2 watts.

The responsible folk that are building out rooms with multiple Subs are doing so with the intention of greater efficiency. I know you don't agree with "more is more" (except for more-subs-equals-more-problems ), but discussion yields the theme of only needing to run their monster subs in quantity at less than half power to yield the results they desire.

Frankly, I can't say I have any desire to run some of the insane house curves many use. I've seen some arguing for +20, even! But I do like the idea of not needing to dump 188v into a Sub to get it to produce a 16Hz Low C at 70dB while running out of excursion and motor stability.

The balance point is somewhere in the middle of all this, of course. But there is a growing market segment that isn't afraid to build large and demand bigger still. These products aren't going away. Rather, I hope we see them get built better and eventually a bit less expensive. (This RBH Sub is more expensive than my first car back in '92!)

Well hope springs eternal. But that is design is an ultimate brute force design with that amount of power. You are fighting the laws of nature all along that path. As I have said before a loudspeaker cone is about the worst device you could think of for coupling low frequencies to air. The lower you go the concept becomes progressively worse and untenable. So getting it clean with that closed box design is huge up hill lift and not intellectually appealing at all.

I certainly have never felt I need more bass extension or output, I have more than enough with modest power. Why? Because I am using nature's laws to my advantage and not fighting them. Honestly I am yet to hear a sealed sub that produces what I assess as clean natural bass. This rig really does produce a natural very clean bass with no fuss or struggle. So I would never remotely consider installing one or more of those in my system. Many visitors now have remarked how it is the bass quality that really sets this system apart.

I use four of these to fill my larger than average room, with deep clean bass.

As I have said before if more subs are going to be required to solve room FR issues, then they are going to have to be in wall. If not the space will be unlivable. TLs fit the bill here as they are ideal for in wall application and produce really natural bass if correctly designed.

 

[gene]

Gene how easy was it for you to integrate this sub since it's a sealed design with your ported subs in that room? Is that something you can tell us about or do you plan to put that in the article? People always hear that your not recommended to do this but I know some people that do in they're rooms. I'm curious how you were able to make it work

it wasn't easy. I had to employ two All Pass Filters to not get it to cancel with the other ported subs in my system. I may investigate sealing ALL of the ported subs in my system to eliminate the APFs. I have so much headroom in bass that it may be worth the output sacrifice. It will certainly reinforce the infrasonics which my family won't appreciate

 

[TLS Guy]

it wasn't easy. I had to employ two All Pass Filters to not get it to cancel with the other ported subs in my system. I may investigate sealing ALL of the ported subs in my system to eliminate the APFs. I have so much headroom in bass that it may be worth the output sacrifice. It will certainly reinforce the infrasonics which my family won't appreciate

That's an awful lot of trouble to go to just for 20 Hz or so of the audio spectrum. I can certainly think of frequency bands much more deserving of that degree of attention and expense. I honestly have to say, I have not had to fuss over getting good clean, realistic and deep bass. I guess we had different mentors.

 

[AcuDefTechGuy]

I doubt the RBH 21-SF/R will produce anywhere near the magnitude of sonic boom caused by the F-4 jet.