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

[Bobby Bass]

Gene love the gangster look with the sub. What a monster! I need a bigger house so I can put in all this amazing equipment. Or maybe I should start with the equipment and build the house around it. I know where I’m spending my money if I hit powerball.

 

[Matthew J Poes]

I'm sorry I'm being "silly" as I'm not a subwoofer expert. But doesn't room gain also apply to ported subs, particularly down to their port frequency? The RSL is tuned to 16Hz I gather? (Infrasonic the last time I checked) and from what "silly" things I understand is that the really big advantage with a sealed box for room gain would be below that frequency due to the faster roll off on ported sub (not because room gain doesn't actually affect ported subs as well). I'm just going by the reviews burst measurements quasi-anechoic so maybe I missed how the RBH can put out more bass at 20Hz or even 16Hz than four RSL 12s units. At 10Hz, there's no question about it.

Like I said, I'm not an expert on subs, which is why I asked a question based on the quasi-anechoic measurements based on my needs (not yours as you seem to be assuming by your comments about Infrasonic use only and already having four subs).

Now you might want 10Hz tactile feel from a real sub, but 14-16Hz is about as low as I imagine ever needing to go (pipe organ). Explosions aren't that interesting to me and a Crowson actuator would give safer Infrasonic tactile sensations (for both my hearing and my house structure) than blasting oneself below 16Hz for $650 per chair (plus amp) and a DIY HoverEze would be an more reasonably priced. But maybe my silly non-expert self is still missing something here?

A number of groups did some studies looking at their ported and sealed subwoofers in various rooms and found pretty consistently that ported subwoofers didn’t get much if any room gain advantage below port tuning. Erik Weiderholtz did a presentation on this at ISE. The folks at Ascendo and Mark Seaton have shared similar findings in their own work. It’s been consistently my finding as well.

The reason that the majority of in-room infrasonic generators are sealed was this finding. The sealed subs have a really significant advantage down to DC.

it’s also important to note that room gain isn’t fixed or automatic. Very large rooms will have a lot less. Maybe none.

 

[TLS Guy]

A number of groups did some studies looking at their ported and sealed subwoofers in various rooms and found pretty consistently that ported subwoofers didn’t get much if any room gain advantage below port tuning. Erik Weiderholtz did a presentation on this at ISE. The folks at Ascendo and Mark Seaton have shared similar findings in their own work. It’s been consistently my finding as well.

The reason that the majority of in-room infrasonic generators are sealed was this finding. The sealed subs have a really significant advantage down to DC.

it’s also important to note that room gain isn’t fixed or automatic. Very large rooms will have a lot less. Maybe none.

That is because drivers in a ported box, rapidly decouple from the box below tuning, which will be around F3. The roll off is 24 db per octave. You can not equalize this, as you just get useless cone excursion and damage the driver. A sealed alignment has a much higher Fs and rolls off 12 db. per octave. You can equalize it, if the VC can take the power and the driver has the excursion. You must high pass at xmax otherwise you will be looking for another driver. However you double the power required for every 3 db. of equalization. So very quickly you require enormous amounts of power. So this generates a ton of heat in the VC, which goes up by the square of the current. So, that is why I call it the brute force approach, which it is. Elegant engineering it is not, and its very hall mark is inefficiency.

 

[Mr._Clark]

It is not just hearing that low frequencies damage, but the CNS as a whole and even cardiovascular damage. The effects of low frequency abuse are significantly different from spl. abuse per se. They do not just involve hearing. There has not been a lot of investigation until recently and LF noise from wind farms has prompted a resurgence of interest.

Here is a good review article of the literature. Although it goes back to 1920, this is a relatively new area of study.

I know for certain that I don't like excessive bass, but a well balanced sound. I have stated here often that I think subwoofers are frequently abused to the detriment of realistic accurate reproduction. I do not believe these 'mega' subs are required for accurate balanced reproduction in the home. As you know I do not use a sub as such in my HT room. However I believe the reproduction to be balanced and accurate to concert hall levels, with no frequency band favored over another.

I think this topic will receive increasing attention in the years ahead. As I have said, at this time I advise caution, and reinforce the dictum of Primum non Nocere!

This is a bit off topic, but back in my engineering days one of the issues we had to deal with was stress on satellite structures due to acoustic energy during launch. When I first became aware of this, it surprised me how much energy from the sound waves was input to the structures. At the time there was no really good way (at least not that I was are of) to predict the response of the structure.

>>>The rationale for acoustic noise testing is straightforward, as acoustic energy is the primary source of vibration input to a space launch vehicle. . . . Acoustic energy is transmitted to the mission payload in two ways. First, fluctuating pressures within the payload fairing impinge directly on exposed spacecraft surfaces, inducing vibration in high gain antennae, solar panels and other components having a large ratio of area-to-mass. Secondarily, the fluctuating external pressure field causes an oscillatory response of the rocket structure, which is ultimately transmitted through the spacecraft attachment ring in the form of random vibration. . . . At the integrated spacecraft level, then, acoustic noise is a primary source of vibration excitation.<<<

Llis

llis.nasa.gov

The sound can be incredibly loud, and I doubt anyone will be generating 200+ decibels in a home audio system.

>>>Nasa's measurements at the time [of the Saturn V launches] captured the launch noise at 204 decibels.

Just how loud is a rocket launch?

The massive thrust needed to launch a rocket into space creates a lot of noise. With the launch of SpaceX's enormous Starship rocket, how loud did it get?

www.bbc.com

 

[isolar8001]

You think the 21-SF/R was something...just wait until this one.

 

[highfigh]

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.

Look at the homes owned by major celebrities and athletes- they often have a theater and because they have many, many millions of dollars to spend and because the younger ones like to show off and compete with their friends, too much is just right. While he wasn't a celebrity, one of my old customers built a 17,000 square foot house and the theater was, IIRC, 24' by 30-something by about 14' and he definitely liked his bass, but not to excess. That room would be a good candidate for this type of subwoofer and he's not even in the star athlete income level.

 

[highfigh]

This is a bit off topic, but back in my engineering days one of the issues we had to deal with was stress on satellite structures due to acoustic energy during launch. When I first became aware of this, it surprised me how much energy from the sound waves was input to the structures. At the time there was no really good way (at least not that I was are of) to predict the response of the structure.

>>>The rationale for acoustic noise testing is straightforward, as acoustic energy is the primary source of vibration input to a space launch vehicle. . . . Acoustic energy is transmitted to the mission payload in two ways. First, fluctuating pressures within the payload fairing impinge directly on exposed spacecraft surfaces, inducing vibration in high gain antennae, solar panels and other components having a large ratio of area-to-mass. Secondarily, the fluctuating external pressure field causes an oscillatory response of the rocket structure, which is ultimately transmitted through the spacecraft attachment ring in the form of random vibration. . . . At the integrated spacecraft level, then, acoustic noise is a primary source of vibration excitation.<<<

Llis

llis.nasa.gov

The sound can be incredibly loud, and I doubt anyone will be generating 200+ decibels in a home audio system.

>>>Nasa's measurements at the time [of the Saturn V launches] captured the launch noise at 204 decibels.

Just how loud is a rocket launch?

The massive thrust needed to launch a rocket into space creates a lot of noise. With the launch of SpaceX's enormous Starship rocket, how loud did it get?

www.bbc.com

Any idea of the distance from measurement instrument(s) to the launch pad?

 

[Mr._Clark]

Any idea of the distance from measurement instrument(s) to the launch pad?

The numbers in the NASA lesson (Figure 2) are based on measurements inside the fairings of the rockets:

>>>To quantify the acoustic environment during launch, launch vehicles are often instrumented with internal microphones, which measure noise levels within the rocket fairing. This data is telemetered to the ground for processing and ultimately plotted in the form of a sound pressure level versus frequency spectrum. Since the acoustic forcing function is stochastic, depending on many atmospheric and other variables, data from a number of such flights are generally gathered, and an envelope, such as that of Figure 1, is developed to encompass the historical record of microphone data.

This process can be extended and applied to data from a number of launch vehicles. If a launch platform has not yet been manifested for a particular payload, acoustic profiles from a number of candidate rockets can be enveloped, producing an aggressive specification which will ensure design adequacy for the spacecraft. Figure 2 reflects such a process, providing an envelope which encompasses the acoustic environments from three launch vehicles.<<<

I'm not sure about the numbers in the BBC article.

 

[highfigh]

The numbers in the NASA lesson (Figure 2) are based on measurements inside the fairings of the rockets:

>>>To quantify the acoustic environment during launch, launch vehicles are often instrumented with internal microphones, which measure noise levels within the rocket fairing. This data is telemetered to the ground for processing and ultimately plotted in the form of a sound pressure level versus frequency spectrum. Since the acoustic forcing function is stochastic, depending on many atmospheric and other variables, data from a number of such flights are generally gathered, and an envelope, such as that of Figure 1, is developed to encompass the historical record of microphone data.

This process can be extended and applied to data from a number of launch vehicles. If a launch platform has not yet been manifested for a particular payload, acoustic profiles from a number of candidate rockets can be enveloped, producing an aggressive specification which will ensure design adequacy for the spacecraft. Figure 2 reflects such a process, providing an envelope which encompasses the acoustic environments from three launch vehicles.<<<

I'm not sure about the numbers in the BBC article.

I doubt they used microphones, more likely strain gauges- am I correct?

 

[Mr._Clark]

I doubt they used microphones, more likely strain gauges- am I correct?

The NASA information says "internal microphones, which measure noise levels within the rocket fairing." I believe this is correct because the basic idea is to use measured noise levels from prior launches to predict future noise levels (predicting future noise levels is really just a SWAG with a layer of fudge factor applied, hence the "enveloped" language) and then predict the resulting vibrations in a different payload (satellite). Different payloads will vibrate differently and experience different stresses in response to the exact same acoustic load, so it is necessary to separately evaluate each new payload based on the predicted noise level.

If one were launching numerous identical satellites on identical launch vehicles I imagine it would be feasible to measure one of more of stress/strain/acceleration directly during a launch and use this instead of predicting these quantities based on the acoustic load. Even this would not be 100% accurate due to differences in atmospheric conditions and other variables at launch, which would change the acoustic load. One could measure stress/strain/acceleration during numerous launches in an effort to determine the effects of launch variables to more accurately predict the loads, but I'm not sure if anyone has tried this.

 

[AcuDefTechGuy]

You think the 21-SF/R was something...just wait until this one.

View attachment 62586

The RBH 21-SF/R, AKA "The Phantom F4 Subwoofer".

SURGEON GENERAL'S WARNING: Listening at MAX VOLUME LEVEL/4,000W may be detrimental to your health!

 

[VonMagnum]

A number of groups did some studies looking at their ported and sealed subwoofers in various rooms and found pretty consistently that ported subwoofers didn’t get much if any room gain advantage below port tuning. Erik Weiderholtz did a presentation on this at ISE. The folks at Ascendo and Mark Seaton have shared similar findings in their own work. It’s been consistently my finding as well.

The reason that the majority of in-room infrasonic generators are sealed was this finding. The sealed subs have a really significant advantage down to DC.

it’s also important to note that room gain isn’t fixed or automatic. Very large rooms will have a lot less. Maybe none.

If you reread what I said it clearly says "down to" the port tuning frequency not "below it". If the sub is tuned to 16Hz then a sealed sub only has an advantage for room gain below 16Hz. I still fail to see by the numbers posted where this RBH sub is more powerful than four comvined RSL 12S subs down to 16Hz. Room gain benefits both equally down to 16Hz. I only see an advantage to RBH starting below 16Hz.

As I indicated, if going below 16Hz isn't important to someone, what advantage does RBH provide at 3x the price and no ability to smooth room modes with only one sub?

I'm talked to like I'm an idiot when I'm just asking a question, but I haven't seen a single response yet address it properly, just making it appear I said something else entirely.

 

[Danzilla31]

If you reread what I said it clearly says "down to" the port tuning frequency not "below it". If the sub is tuned to 16Hz then a sealed sub only has an advantage for room gain below 16Hz. I still fail to see by the numbers posted where this RBH sub is more powerful than four comvined RSL 12S subs down to 16Hz. Room gain benefits both equally down to 16Hz. I only see an advantage to RBH starting below 16Hz.

As I indicated, if going below 16Hz isn't important to someone, what advantage does RBH provide at 3x the price and no ability to smooth room modes with only one sub?

I'm talked to like I'm an idiot when I'm just asking a question, but I haven't seen a single response yet address it properly, just making it appear I said something else entirely.

 

[Danzilla31]

If you reread what I said it clearly says "down to" the port tuning frequency not "below it". If the sub is tuned to 16Hz then a sealed sub only has an advantage for room gain below 16Hz. I still fail to see by the numbers posted where this RBH sub is more powerful than four comvined RSL 12S subs down to 16Hz. Room gain benefits both equally down to 16Hz. I only see an advantage to RBH starting below 16Hz.

As I indicated, if going below 16Hz isn't important to someone, what advantage does RBH provide at 3x the price and no ability to smooth room modes with only one sub?

I'm talked to like I'm an idiot when I'm just asking a question, but I haven't seen a single response yet address it properly, just making it appear I said something else entirely.

So I posted those 2 sets of data to try and figure it out how much gain do you expect we will get from the 4 RSL subs?

I think from the way I understand the increase in output is dependent on the room and frequency and isn't always as linear as people think. Of course that same thing applies to the RBH sub in room

 

[Danzilla31]

Also I don

If you reread what I said it clearly says "down to" the port tuning frequency not "below it". If the sub is tuned to 16Hz then a sealed sub only has an advantage for room gain below 16Hz. I still fail to see by the numbers posted where this RBH sub is more powerful than four comvined RSL 12S subs down to 16Hz. Room gain benefits both equally down to 16Hz. I only see an advantage to RBH starting below 16Hz.

As I indicated, if going below 16Hz isn't important to someone, what advantage does RBH provide at 3x the price and no ability to smooth room modes with only one sub?

I'm talked to like I'm an idiot when I'm just asking a question, but I haven't seen a single response yet address it properly, just making it appear I said something else entirely.

I'm not following why you think people are talking to you like an idiot. Gene said that's silly he didn't say you were silly. And I didn't see Shady or Mathew come at you that way at all.
I'm wondering what is the math on upscaling 4 subs when all are combined in a room.

I think it was Ricci was talked about it in Data-Bass that that extra output will vary from room to room though. You can't always assume that your going to get exactly the output the math says you will

 

[William Lemmerhirt]

Also I don

I'm not following why you think people are talking to you like an idiot. Gene said that's silly he didn't say you were silly. And I didn't see Shady or Mathew come at you that way at all.
I'm wondering what is the math on upscaling 4 subs when all are combined in a room.

I think it was Ricci was talked about it in Data-Bass that that extra output will vary from room to room though. You can't always assume that your going to get exactly the output the math says you will

If I’m not mistaken Dan, you can usually expect about 3-6db per each subwoofer after the first one. Of course these aren’t necessarily linear translations and are frequency dependent, but should give an idea. In my room for example, just using the AVR test tone, I get about 4db(iirc) each from my second and third subs.

 

[TLS Guy]

If you reread what I said it clearly says "down to" the port tuning frequency not "below it". If the sub is tuned to 16Hz then a sealed sub only has an advantage for room gain below 16Hz. I still fail to see by the numbers posted where this RBH sub is more powerful than four comvined RSL 12S subs down to 16Hz. Room gain benefits both equally down to 16Hz. I only see an advantage to RBH starting below 16Hz.

As I indicated, if going below 16Hz isn't important to someone, what advantage does RBH provide at 3x the price and no ability to smooth room modes with only one sub?

I'm talked to like I'm an idiot when I'm just asking a question, but I haven't seen a single response yet address it properly, just making it appear I said something else entirely.

The RBH sub wins, but not by as much as you would think. The figures also illustrate the massive efficiency penalty you pay for a sealed design.

So of you had four RSL speedwoofers, you would get a gain of 6db over a single

Now we need to look not only at the output in the 16 Hz range and below, but well above it. This reveals the efficiency penalty of a sealed design and it is massive.

4 X RSL------------------------------------------ RBH
31.5 HZ 114.4db ------------------------120.1db

20Hz 110.6db -------------------------112.3db

16Hz 106.1db --------------------------105.5db

12.5Hz 93.7db --------------------------- 97.7db

However the four RSL subs would require 2000 watts for max output.

So going from 31.5 Hz to 16 Hz there are roughly five 3db steps in which the RBH sub has to double its power output. The RSL subs will be constant power and roll off 24db between 20 and 10 Hz, but amp output will not have to increase. So the RSLs are actually the more efficient solution by far, with only a penalty in the infrasonic range.
In my view that does not justify such a massive and costly engineering response the quality of the engineering not withstanding. The whole approach to me is intellectually unsatisfying.

 

[Danzilla31]

The RBH sub wins, but not by as much as you would think. The figures also illustrate the massive efficiency penalty you pay for a sealed design.

So of you had four RSL speedwoofers, you would get a gain of 6db over a single

Now we need to look not only at the output in the 16 Hz range and below, but well above it. This reveals the efficiency penalty of a sealed design and it is massive.

4 X RSL------------------------------------------ RBH
31.5 HZ 114.4db ------------------------120.1db

20Hz 110.6db -------------------------112.3db

16Hz 106.1db --------------------------105.5db

12.5Hz 93.7db --------------------------- 97.7db

However the four RSL subs would require 2000 watts for max output.

So going from 31.5 Hz to 16 Hz there are roughly five 3db steps in which the RBH sub has to double its power output. The RSL subs will be constant power and roll off 24db between 20 and 10 Hz, but amp output will not have to increase. So the RSLs are actually the more efficient solution by far, with only a penalty in the infrasonic range.
In my view that does not justify such a massive and costly engineering response the quality of the engineering not withstanding. The whole approach to me is intellectually unsatisfying.

So why can't a ported sub be done that could get you there to infrasonic.? One with a low port tune. The box needs to be bigger. But with that in mind the power requirements are less and as long as the ports can go that low you get the best output vs efficiency especially with power usage.

In fact @TLS Guy your talented and very knowledgeable about modeling and building speakers and subs.

Not asking for a detailed model but can you give us an rough ideas ballpark figure on just how big a box and driver would need to be to get you there into infrasonics without using a ton of power

 

[shadyJ]

The RBH sub wins, but not by as much as you would think. The figures also illustrate the massive efficiency penalty you pay for a sealed design.

So of you had four RSL speedwoofers, you would get a gain of 6db over a single

Now we need to look not only at the output in the 16 Hz range and below, but well above it. This reveals the efficiency penalty of a sealed design and it is massive.

4 X RSL------------------------------------------ RBH
31.5 HZ 114.4db ------------------------120.1db

20Hz 110.6db -------------------------112.3db

16Hz 106.1db --------------------------105.5db

12.5Hz 93.7db --------------------------- 97.7db

However the four RSL subs would require 2000 watts for max output.

So going from 31.5 Hz to 16 Hz there are roughly five 3db steps in which the RBH sub has to double its power output. The RSL subs will be constant power and roll off 24db between 20 and 10 Hz, but amp output will not have to increase. So the RSLs are actually the more efficient solution by far, with only a penalty in the infrasonic range.
In my view that does not justify such a massive and costly engineering response the quality of the engineering not withstanding. The whole approach to me is intellectually unsatisfying.

I would expect a 12dB increase going from one to four subs, at least if they were all placed in a single spot. A 6dB increase is a doubling in amplitude. So double that, and you should get a 12dB increase.

 

[lovinthehd]

I would expect a 12dB increase going from one to four subs, at least if they were all placed in a single spot. A 6dB increase is a doubling in amplitude. So double that, and you should get a 12dB increase.

Why would you place all subs in a single spot, tho? Or you mean just within a 1/4 wavelength or ?