RTJ Audio 18Sub Subwoofer Review

[shadyJ]

​

RTJ Audio blew us away when they paid a visit to the Audioholics Smarthome with a pair of their 410 modular towers. It had a monster dynamic range but not at the expense of fidelity, and it was a speaker that could tackle any high-end private cinema with ease no matter how large. Sadly, we only had time to play with the 410s for one weekend, but that might have been for the best since it made loud sound so good that we might have ended up with hearing damage if we had them for a longer period. We found many of the design details intriguing, and so we leaped at the chance to review one of the subwoofer modules that RTJ calls the 18Sub. While the subwoofer modules can be had as a part of the complete 410 tower system, they can also be had separately, and there are a lot of interesting aspects of their design that warrant the 18Subs for serious consideration as an individual subwoofer system. Read our full review to learn about the RTJ 18Sub...

READ: RTJ Audio 18Sub Subwoofer Review

 

[ryanosaur]

Very cool, @shadyJ ! Thanks again for another one!!!

 

[Danzilla31]

Wow shady great review. What a gorgeous beast of a subwoofer

 

[TLS Guy]

​

RTJ Audio blew us away when they paid a visit to the Audioholics Smarthome with a pair of their 410 modular towers. It had a monster dynamic range but not at the expense of fidelity, and it was a speaker that could tackle any high-end private cinema with ease no matter how large. Sadly, we only had time to play with the 410s for one weekend, but that might have been for the best since it made loud sound so good that we might have ended up with hearing damage if we had them for a longer period. We found many of the design details intriguing, and so we leaped at the chance to review one of the subwoofer modules that RTJ calls the 18Sub. While the subwoofer modules can be had as a part of the complete 410 tower system, they can also be had separately, and there are a lot of interesting aspects of their design that warrant the 18Subs for serious consideration as an individual subwoofer system. Read our full review to learn about the RTJ 18Sub...

​

RTJ Audio blew us away when they paid a visit to the Audioholics Smarthome with a pair of their 410 modular towers. It had a monster dynamic range but not at the expense of fidelity, and it was a speaker that could tackle any high-end private cinema with ease no matter how large. Sadly, we only had time to play with the 410s for one weekend, but that might have been for the best since it made loud sound so good that we might have ended up with hearing damage if we had them for a longer period. We found many of the design details intriguing, and so we leaped at the chance to review one of the subwoofer modules that RTJ calls the 18Sub. While the subwoofer modules can be had as a part of the complete 410 tower system, they can also be had separately, and there are a lot of interesting aspects of their design that warrant the 18Subs for serious consideration as an individual subwoofer system. Read our full review to learn about the RTJ 18Sub...

That was a really interesting review. I am really impressed that they got Le below 1 mH. Although that is not confirmed by measurement.

I think you notion that this driver is ripe for being used in a three way speaker is right on point.

When I was designing my AV studio system, it went against the grain to give all those resources just to the last two octaves, or less.

The especially true for systems for classical music, where a huge amount of the program is in the range above 80 Hz, and especially up to 600 Hz. The vast majority of speakers lack authority in this range. To make matters worse it is also the range were BSC is operative, adding insult to injury.

Anyhow I went through several designs, and decided that an integrated design was not just a design choice but mandatory for the results I wanted. Since I was going for reasonable efficiency with the TL design, I did not require insane power levels. So that is how I came to use non sub drivers for the sub section and used two 10" SEAS Excel drivers a side. So that is equivalent to two 15" drivers. Since the Fs was 20 Hz and they had very acceptable xmax when TL loaded they fit the bill. Le is an acceptable 1.4 mH.

So this allowed with an active design one of those drivers per side to handle the BSC and sub duties. Both driver handle the sub range. This is easily accomplished in an active design with a mixer circuit and buffer amp.

The result has been everything I could have wanted and a spectacular success. I have believed since then, that an integrated design is the state of the art optimal approach. After all we don't accept off the shelf crossover any place other than subs. Those who think that is OK are deluding themselves. I agree it is somewhat excused by the ear being less sensitive down that low, but an integrated approach has advantages above and beyond just avoiding an off the shelf crossover.

So if this driver stimulates some integrated designs well and good. RTJ should seriously consider making that driver available OEM.

 

[Verdinut]

In my HT system, I am using one Dayton RSS390HF-4 15" sub driver as component of each of my 3 way front speakers, bi-amping with crossover frequency at 200 Hz between each sub and the mid-bass drivers.
With regard to this subwoofer which is well designed, its LE is reported by the manufacturer at 0.92 mH.

 

[Kursun]

Something is wrong with this sentence:
"Here we see a traditional sealed response shape which is unusual since most manufactured sealed subs use a high-pass filter for protection which makes for a steeper roll-off on the low end. "

It is not sealed subs that need high-pass filtering.
But it is generally required for ported subs.
Because drivers in ported enclosures decouple, that is become uncontrollable below system resonance frequency.

Where as, in sealed subs, controlling effect of air mass in enclosure increases with lower frequencies.

 

[shadyJ]

Something is wrong with this sentence:
"Here we see a traditional sealed response shape which is unusual since most manufactured sealed subs use a high-pass filter for protection which makes for a steeper roll-off on the low end. "

It is not sealed subs that need high-pass filtering.
But it is generally required for ported subs.
Because drivers in ported enclosures decouple, that is become uncontrollable below system resonance frequency.

Where as, in sealed subs, controlling effect of air mass in enclosure increases with lower frequencies.

Many manufacturers use high-pass filters to protect over-driving in sealed subs. Sealed subs can still be pushed into over-driving, but it is not as easy as over-driving a woofer below port tuning in a vented sub.

 

[TLS Guy]

Something is wrong with this sentence:
"Here we see a traditional sealed response shape which is unusual since most manufactured sealed subs use a high-pass filter for protection which makes for a steeper roll-off on the low end. "

It is not sealed subs that need high-pass filtering.
But it is generally required for ported subs.
Because drivers in ported enclosures decouple, that is become uncontrollable below system resonance frequency.

Where as, in sealed subs, controlling effect of air mass in enclosure increases with lower frequencies.

Actually it is only mandatory for most sealed subs, as you have to boost 12db per octave below F3, so you have to high pass below the frequency where xmax occurs. Vented subs on the other hand roll off naturally at 24db per octave below F3, but do decouple from the box below F3. However, the power is much lower and more often than not the decoupling does not bottom the driver. If f3 is 20 Hz or less then there is not much point in high passing at that point as little material will be there to drive the woofer. In most vented alignments with a good driver, cone excursion is usually below xmax, and sometimes by a lot, in the tuning region even at max power.

The only advantage of sealed subs is size. After that it is all negative. Well designed ported,, TL and horn subs couple much better to the room, and are preferred. In the latter two, TL and horn, the driver is better controlled, loaded and assisted over a much larger FR. I do not high pass my big bass lines at all. In a sealed sub the driver is the only coupling to the room. A loudspeaker cone is a terrible acoustic coupler to any air space in the LF range., hence the need for gobs of power. I have zero inclination to ever design and build a sealed sub for any of my systems.

 

[luis1090]

Great performance, it should make the right customer happy. I just think at almost 7K it's a really tough sell. I can basically buy 3 SVS SB16-Ultra and still have some money left for a nice steak dinner. The SVS it's highly adjustable and you can set it up from your phone with the SVS app. Finally I don't care if it is designed to be hidden it is dull, just a lazy design, even if $7K is in my budget for a subwoofer it would be a hard pass.

 

[ryanosaur]

Great performance, it should make the right customer happy. I just think at almost 7K it's a really tough sell. I can basically buy 3 SVS SB16-Ultra and still have some money left for a nice steak dinner. The SVS it's highly adjustable and you can set it up from your phone with the SVS app. Finally I don't care if it is designed to be hidden it is dull, just a lazy design, even if $7K is in my budget for a subwoofer it would be a hard pass.

It depends on where your focus is. I'm certainly not buying any $7000 Subs anytime soon, but the world of Extreme Subs is very real and growing... and SVS is not competing in that realm.
Slick cabinets and Phone Apps have a market, just as JTR and RTJ do, or some of the Subs you can buy at GSG or PSA. I've seen folk go through SVS to PSA to JTR to DIY... Some are never satisfied while others find the sweet spot for their own needs.

Hell, I've even see a guy selling his Funk Subs because they didn't scratch his particular itch, and that's about as high up the ladder as one can go! At that point you are shopping JL, RBH, YG... and REL isn't good enough!

That's the nice thing about a free market is you can choose what's right for you!

 

[TLS Guy]

Great performance, it should make the right customer happy. I just think at almost 7K it's a really tough sell. I can basically buy 3 SVS SB16-Ultra and still have some money left for a nice steak dinner. The SVS it's highly adjustable and you can set it up from your phone with the SVS app. Finally I don't care if it is designed to be hidden it is dull, just a lazy design, even if $7K is in my budget for a subwoofer it would be a hard pass.

It is aimed at a totally different market. That sub is not designed to be seen. Basically it is for the professional designer and installer market, to design AV rooms for the custom luxury home market. This market is crying out for designs of really good speakers that can be in wall. I don't mean standard walls, but in false walls. It is nearly impossible to design an elegant space with most of the equipment available today. These clients want equipment heard and NOT seen.

Making pleasant restful spaces that contain state of the art AV systems is a huge challenge. Amateurs generally make a dog's dinner of the aesthetics.

If you are an experienced non pro, like myself, you have a huge architectural/Interior design and acoustical technical challenge. I can assure you it is a mountain to climb.

So yes, the challenge that there is to meet is acceptable, and even beautiful spaces, with gorgeous and life like sound. At the moment this is the preserve of the very wealthy, or the very experienced designer home DIY constructor. Unless this conundrum can be solved really good sounding visually acceptable rooms will continue to be niche, with sound bar and small sub for the masses.

 

[shadyJ]

Great performance, it should make the right customer happy. I just think at almost 7K it's a really tough sell. I can basically buy 3 SVS SB16-Ultra and still have some money left for a nice steak dinner. The SVS it's highly adjustable and you can set it up from your phone with the SVS app. Finally I don't care if it is designed to be hidden it is dull, just a lazy design, even if $7K is in my budget for a subwoofer it would be a hard pass.

Few people will be buying just one of these. They are really intended to be sold as multiples, and then the price lowers. Most people would be buying a quad drive, and then the price is 4,250 each. And if you look at the world of high-performance baffle-wall or in-wall subs, that actually is a pretty good bargain. SVS's in-wall system, a quad 9" woofer with an 800-watt amp, goes for $3k and likely wouldn't be able to touch the performance of just one 18Sub system. It would have equal cone area with maybe half the excursion and a quarter of the power.

As for adjustability, all a sub needs is a gain knob, phase switch, and LPF knob, especially for an in-wall or architectural system. The rest should really be done on board the AV processor. An app control would be useless for a system like this.

 

[TLS Guy]

Few people will be buying just one of these. They are really intended to be sold as multiples, and then the price lowers. Most people would be buying a quad drive, and then the price is 4,250 each. And if you look at the world of high-performance baffle-wall or in-wall subs, that actually is a pretty good bargain. SVS's in-wall system, a quad 9" woofer with an 800-watt amp, goes for $3k and likely wouldn't be able to touch the performance of just one 18Sub system. It would have equal cone area with maybe half the excursion and a quarter of the power.

As for adjustability, all a sub needs is a gain knob, phase switch, and LPF knob, especially for an in-wall or architectural system. The rest should really be done on board the AV processor. An app control would be useless for a system like this.

As I said this is aimed largely at the pro installer market. As I said these units are really for the new construction or extensive remodel market. I have now done both, but new construction I think is actually easier then the extensive remodel.

We have got to the point, I believe were state of the art multichannel audio does require an extensive building remodel or custom new construction. This is obviously going to limit uptake and acceptance. However that is the point we have got to. However the silver lining is that good 2.1 and 3.1 really does give you most of what is required. There should be far more of these systems than inadequate multichannel systems. In fact I think these inadequate multichannel system but a brake on advancement.
What I notice is that mix engineers are very reluctant to put much power on speakers other than the front three. They treat the rest with kid gloves. They seem to me far too scared of blowing up the rest of the speakers. I only have one SACD that really puts the power to the rear speakers. The professional reviewers said it was unplayable. Well, it isn't. I have a BD with significant musical resources in the rear. The mix engineers got cold feet and flipped them to the front.

 

[Kursun]

Actually it is only mandatory for most sealed subs, as you have to boost 12db per octave below F3, so you have to high pass below the frequency where xmax occurs. Vented subs on the other hand roll off naturally at 24db per octave below F3, but do decouple from the box below F3. However, the power is much lower and more often than not the decoupling does not bottom the driver. If f3 is 20 Hz or less then there is not much point in high passing at that point as little material will be there to drive the woofer. In most vented alignments with a good driver, cone excursion is usually below xmax, and sometimes by a lot, in the tuning region even at max power.

The only advantage of sealed subs is size. After that it is all negative. Well designed ported,, TL and horn subs couple much better to the room, and are preferred. In the latter two, TL and horn, the driver is better controlled, loaded and assisted over a much larger FR. I do not high pass my big bass lines at all. In a sealed sub the driver is the only coupling to the room. A loudspeaker cone is a terrible acoustic coupler to any air space in the LF range., hence the need for gobs of power. I have zero inclination to ever design and build a sealed sub for any of my systems.

Driver decoupling of bass reflex (ported) is a fact and is a serious problem.

Bass reflex - Wikipedia

en.wikipedia.org

.
"For frequencies above the natural resonance of the driver, the reflex alignment has no influence. For frequencies below the vent resonance, polarity inversion is not accomplished, and backwave cancellation occurs. Furthermore, the driver behaves as though suspended in free air, as box air springiness is absent. "
Another problem for bass-reflex (ported) enclosures is phase inaccuracy.
"The penalty incurred for this reinforcement is time smearing: in essence the vent resonance augments main driver output by imposing a "resonant tail" on it. "

 

[TLS Guy]

Driver decoupling of bass reflex (ported) is a fact and is a serious problem.

Bass reflex - Wikipedia

en.wikipedia.org

.
"For frequencies above the natural resonance of the driver, the reflex alignment has no influence. For frequencies below the vent resonance, polarity inversion is not accomplished, and backwave cancellation occurs. Furthermore, the driver behaves as though suspended in free air, as box air springiness is absent. "
Another problem for bass-reflex (ported) enclosures is phase inaccuracy.
"The penalty incurred for this reinforcement is time smearing: in essence the vent resonance augments main driver output by imposing a "resonant tail" on it. "

I am not disputing that. My point is that it practice it is not a serious issue. The reasons are as I said two fold. The first is that in a ported sub the driver is not getting a 20db or more boost at those frequencies. The other point is that in a sub with a low F3, there is little content to cause the excess cone movement below F3 of a decent sub. The other issue is that F3 is not a brick wall and the decoupling from the box is gradual. I have never high passed a reflex ported design. So it has not been an issue. As far as I know commercial ported subs are not generally high passed starting below F3. That phase issue comment is also bogus largely. In a proper design the Q of the total design falls in the right place. The design does cause phase inversion from the rear of the cone, so that the port output is in phase with the front of the cone.
It is true there is some time smear, but in a proper design this is well within acceptable limits, and not audible. There are issues with some poorly designed commercial subs. There are too many with extended bass alignments they do have excessively high Qt resulting in a resonant sounding bass response. That is driven by marketers forcing the designers to play the my F3 is lower than your F3 game.

Properly designed ported subs can, and do, provide excellent bass fidelity.

I have attached a model of a 12" sub design. You can see that the driver does not fully decouple from the box until around 15 Hz, and group delay in the functional range is no more than 20 msec. which will not be audible. So that sub does not need a high pass filter.

 

[MrBoat]

As I said this is aimed largely at the pro installer market. As I said these units are really for the new construction or extensive remodel market. I have now done both, but new construction I think is actually easier then the extensive remodel.

We have got to the point, I believe were state of the art multichannel audio does require an extensive building remodel or custom new construction. This is obviously going to limit uptake and acceptance. However that is the point we have got to. However the silver lining is that good 2.1 and 3.1 really does give you most of what is required. There should be far more of these systems than inadequate multichannel systems. In fact I think these inadequate multichannel system but a brake on advancement.
What I notice is that mix engineers are very reluctant to put much power on speakers other than the front three. They treat the rest with kid gloves. They seem to me far too scared of blowing up the rest of the speakers. I only have one SACD that really puts the power to the rear speakers. The professional reviewers said it was unplayable. Well, it isn't. I have a BD with significant musical resources in the rear. The mix engineers got cold feet and flipped them to the front.

I know 2 friends, who spent more on acoustic treatments for a crappy room, including a demountable partition, than they would have building a much better addition to the house. They could have built a really nice, acoustically superior room, compared to what they ended up trying to do with their existing space. It still doesn't sound/look right.

 

[Steve81]

The other point is that in a sub with a low F3, there is little content to cause the excess cone movement below F3 of a decent sub...As far as I know commercial ported subs are not generally high passed starting below F3.

There is definitely some content out there that can cause problems, even for a sub with an F3 of 20Hz or a little below that. The intro to Edge of Tomorrow comes to mind as being particularly brutal.

AFAIK SVS still uses a HPF on their vented subs as one example. Of course, there are other ways to skin a cat and protect the driver.

 

[aoaaron]

I wish this review cross compared with the D215S a little more.

 

[aoaaron]

Great performance, it should make the right customer happy. I just think at almost 7K it's a really tough sell. I can basically buy 3 SVS SB16-Ultra and still have some money left for a nice steak dinner. The SVS it's highly adjustable and you can set it up from your phone with the SVS app. Finally I don't care if it is designed to be hidden it is dull, just a lazy design, even if $7K is in my budget for a subwoofer it would be a hard pass.

Sadly SVS does not compare to JTR sound quality wise so it doesn't really matter for those that want the best.

 

[Verdinut]

There is definitely some content out there that can cause problems, even for a sub with an F3 of 20Hz or a little below that. The intro to Edge of Tomorrow comes to mind as being particularly brutal.
View attachment 64302
AFAIK SVS still uses a HPF on their vented subs as one example. Of course, there are other ways to skin a cat and protect the driver.

SVS is probably the only manufacturer using a HPF on their subs. When an enclosure is tuned at a frequency surrounding 20 Hz or lower , there is not much risk of damaging the driver. The driver is no longer loaded by the air inside the box only below that box tuning frequency.

If a disc contains tracks with extremely loud passages at frequencies below 15 hz, that could create a problem but this would not be a really audible musical signal. A few pipe organs have a 64 foot pipe stop with a fundamental frequency of 8 Hz. You can only feel the vibration if you are not too distant from it.