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RSL CG4, CG24, and Speedwoofer 10 First Impressions

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CG4 and CG24 Monitors

First impressions have been wrong before. So I tried to approach this with an open mind.  My tune changed a bit once I unboxed the speakers. They felt incredibly solid, had good weight, and build quality seemed to be excellent.  The cabinet for the monitors is made of 1/2 inch MDF and the Speedwoofer 10’s enclosure is 3/4 inch MDF.  RSL’s patented compression guide board (more on that below) provides additional bracing.  What I’m trying to say is that these felt more like solid wood blocks than a hollow enclosure with drivers.

CG4

RSL CG4 Loudspeaker has a single 4" woofer

from the drivers, to construction and finish, the RSL speakers are top notch.

There’s an excellent motor structure to all the drivers.  The tweeter in both models is a 1” silk dome with a ferrite magnet.  The 4” woofers have a cast aluminum frame with ferrite magnet and polypropylene cone.  Given the drivers, I applaud Howard and Joe for their design choices.  The CG4s are only rated down to 100Hz and the CG24s are only rated down to 65Hz.  So many times, speaker manufacturers will want to make their speakers—especially monitors—try and do everything.  Simply put, you can’t bend the laws of physics. When you do that you end up with an acoustic mess.  Instead, these speakers are designed to perform within their range and then hand off the lower end to the subwoofer. The real key, then, will be to see how well these monitors blend with the Speedwoofer 10 sub. 

CG24

RSL CG24 has two 4" woofers in an MTM design

At this price-point, I was impressed to see magnetic grilles on all the monitors.  The grilles are all metal.  There is no acoustically transparent mesh.  The grilles have felt pads on the corners that prevent them from scratching the speakers’ high gloss piano black finish when the magnets snap them into place.  That's right, there are no peg holes in these babies. Instead, neodymium magnets are located behind the front baffle to make a firm connection to the grilles once you position them towards the speakers.

The finish is excellent. It is simply not something you see at this price point.  The high-gloss polyurethane finish is hand-painted.  It’s beautiful, but it is not a flawless, mirror-like look as with SVS’ products.  But RSL’s high-gloss finish also doesn’t command an additional premium like it does on SVS’ Prime series products.  RSL’s finish looks identical to speakers I’ve seen costing thousands.  That is another nod to RSL’s focus on quality.

The rear of both monitor models has a metal threaded hole should you want to hang the speakers with a speaker mount. The gold-plated five-way binding posts are high quality but are shorter than usual.  If you use full size banana plugs they may stick out a bit.  This won’t impact performance, but if you want to hang the speakers flush to a wall then you will need to use shorter 90 degree banana plugs, spades, or bare speaker wire.

 A distinctive feature of both the speakers and the Speedwoofer sub is the thin, rectangular port that RSL calls their Compression Guide.  The CG24s have two compression guides.  The CG4s and Speedwoofer have only one.  RSL says that the Compression Guide is a patented technology so I asked Howard for more information.  

“The first Compression Guide patent was issued to me in the early 90’s,” he said.  “Since that time there have been several additional patents issued for variations and improvements on the design (our current line utilizes those latest improvements).” Howard told me that the inspiration for the design goes back to the 70s when RSL was a new speaker company.  

Compression Guide

RSL Patented Compression Guide courtesy of RSL.  

“During that time I noticed a problem with virtually every speaker on the market, including ours,” Howard told me.  As Howard went on to describe what he was aiming at, it was that “you are there” sensation that so many audiophiles strive to reproduce.  “The best way to describe it is comparing it to hearing a live band. In the live performance when the drummer hits the kick drum with his mallet, you hear the rap of the skin and then feel the impact in your chest. However, when listening to a speaker, all you'd hear was a ‘boom.’ The detail of the drum's skin was lost. It seemed that the only speakers I heard that got it right were the transmission line speakers out of England that typically used a KEF B139 oval woofer. I was determined to find out the cause of the problem and the reason for this bass inaccuracy.

Howard went on to say that he discovered that the problem was caused by the way speakers were tuned using system resonance. He used the following analogy, “Like an acoustic guitar, no mater what note you strike, you'll hear it along with the resonance of the cavity of the guitar. Although nice in a guitar, this isn't what you want from a speaker. Also, as you know, resonance acts like a spring meaning that the woofer wants to keep going after the signal is no longer applied.”

Howard told me that they tried unsuccessfully for many years to find a way to reduce system resonance.  Finally, Howard says, he discovered a way to do it and the Compression Guide was born. “[The Compression Guide] works by essentially dividing the cabinet up into areas of lower and higher pressure (compression). As the sound wave travels though these different pressure zones, the effect of resonance is reduced.  This reduction results in tighter bass and eliminates the ‘boxiness’ that even high-end box speakers tend to suffer from. We also feel that eliminating the ‘boxiness' increases midrange clarity.”  

Compression Guide Subwoofer

Illustration of the Compression Guide Technology on the Speedwoofer 10

Many speakers as diminutive as the RSLs haven’t impressed me with their impact, midrange, or lack of “boxiness” so I was curious to see in practice how this would all play out.

Speaking of midrange, the RSL CG24s are a midrange-tweeter-midrange (MTM) design but not a D’Apollito design.  In a D’Apollito design, the drivers are aligned in an MTM configuration and use a third (18dB/oct) or fourth order (24dB/oct) crossover.  In contrast, CG24s use a first order (6dB/oct) crossover and the CG4s use a second order (12dB/oct) crossover.  

We aren't necessarily subscribers to the D'Appolito design,” Howard told me. “In some cases some [of] the D'Appolito design would have not worked well with our Compression Guide design. We basically design the crossovers to give us the sound we're looking for first.  In the CG24, we had a sonic goal in mind for the speaker, both for stereo and home theater use. Once we've achieved this we measure it to see where we're at and if changes will be necessary. We know that some designers consider this order to be reversed, but this is the method we prefer.”  

RSL markets the CG24s as a center channel speaker, but the model can easily be used for the main left and right channels.  With the CG24s, you could therefore have a truly ideal multichannel setup where you are using the same speaker for every channel with exactly the same orientation.  

The CG4s are a two-way speaker.  What’s visually odd about the CG4’s is the tweeter’s placement under the woofer. When I asked why, Joe told me that the configuration had to with their Compression Guide design. According to Joe, the positioning of the internal board didn't leave ample space for the woofer if the woofer was placed below.  Although a late 1980’s version of the CG speakers had a traditional driver arrangement because there was a little more room, the current design called for repositioning of the board to accomplish a different angle. “To accommodate for this,” Joe told me, “We placed the woofer above to provide proper spacing.”

Speedwoofer 10 Subwoofer

Given the specs of the CG4 and CG24, you’ll certainly want to add a subwoofer.  As part of the review setup, I received the Speedwoofer 10, which is the sole subwoofer in RSL’s lineup.  It features a 10” cast aluminum frame with a rated frequency response of 24-180Hz +/-3db.  The Speedwoofer 10 is driven by a 375W RMS Class A/B amplifier.  Joe and Howard evidently tried several, more powerful Class D amplifiers but were not satisfied with the results.  “We originally checked out a bunch of Class D amps up to 500 watts,” Joe said, “and none of them had the (forgive the lack of technical term) slam of the A/B amp. So we chose that.”  

Speedwoofer 10

RSL's Speedwoofer 10 with a 10" driver

Unpacking the 64lb subwoofer wasn’t as bad as some other subs I’ve had come through my system.  The front-firing subwoofer is solid but unlike the monitors with their metal, magnetic grille, the Speedwoofer 10 has an acoustically transparent grille attached by old-fashioned pegs.  The Speedwoofer 10 includes your choice of plastic feet or spikes.  

The outboard crossover and volume control (that RSL calls the “receiver”) is one of the more distinctive features of the Speedwoofer.  Joe told me that this was one of the unique design elements that they were really proud of.  Unlike so many other subs, RSL’s solution puts all the controls you need at your fingertips in a separate, outboard box.  You don’t need to hunch over the rear of the subwoofer. 

The outboard receiver connects to the Speedwoofer 10 via the included shielded Ethernet cable.    You can place the receiver on top of the sub or move it to anywhere in your setup.  To do so simply use a longer shielded category 5 or category 6 cable.  Note that most typical Ethernet cables are not shielded. 

You can set the crossover and volume using the included remote control.  When it came time for me to calibrate the Speedwoofer 10 sub, I found this to be a smart, incredibly helpful, and time-saving feature.  In addition to handling crossover and volume, the receiver also serves as an indicator for the sub’s power status.  The crossover and volume dials will glow red when the sub is in standby and blue when it is active.  

For die-hard two-channel listeners or those who lack bass management on their receiver or processor, you can go old school.  From your amplifier or receiver simply run speaker cables to the sub and then from the sub to the speaker.   You can now manually manage the crossover from the Speedwoofer.  The user manual goes into extensive detail on this kind of setup if it is a new concept for you.

Speaking of crossover settings, the CG4 monitor is rated at 100Hz-25,000kHz and the CG24 is rated at 65Hz-25,000kHz. Even though you have the flexibility to set whatever crossover you want, the RSL user manual strongly suggests that you set the crossover between 90Hz-110Hz and not the THX standard of 80Hz.  At the very early stages of the review, Joe wanted to make sure I had noted the recommended crossover settings in the user manual.   I ran Anthem’s ARC room correction to see how ARC interpreted the frequency response of the speakers and sub.  Needless to say, ARC confirmed the recommended range Joe had suggested.  

When I listened to the RSL setup with the Anthem, I accepted all the ARC measurements.  When I paired the RSL speakers with the Classé Sigma SSP and AMP5, I manually set the crossover in the Sigma SSP PEQ (parametric equalizer) settings to 100Hz.

The Speedwoofer comes out of standby as soon as it senses an audio signal and goes into standby after 20 minutes of inactivity.  Unlike some other subs with this auto-on and auto-standby feature, not once did I hear the sub “pop” when turning on or when I powered down my system.

 Like the monitors, the Speedwoofer features RSL’s compression guide along the front bottom of the unit.  

 

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Recent Forum Posts:

JPyman325 posts on January 01, 2016 10:52
An update on this amazing systems sub woofer. Last night while watching fireworks with our neighbors we were making sure that neither of could hear our outdoor speakers. He says the only thing he can hear is the neighbor on our other side son playing his new bass. Well its actually my sub watching movies. My HT is upstairs over the garage and there is probably 50 feet between our house and theres -
JPyman325 posts on December 31, 2015 09:20
I would suggest giving RSL a call and talk to either Joe or his dad Roger who designed the speakers. These are one the best speakers I have heard in a long time even off-axis listening as in my bedroom with bookshelf. One of the most impressive is how good these speakers sound at each volume level. My old Def Tech's (1990's) needed power and volume to really come a live. My Mirage's also had their sweet spot. I have not found a volume that these don't sound good but loud is always better.

The speed woofer is amazing a good tight bass for music and with enough power to feel the movie throughout my house. My HT is upstairs above the garage and my wife feels the vibration in our bedroom - other side of the house downstairs and our house is not small (nor large unless you live in New York).
TLS Guy posts on December 31, 2015 09:05
ski2xblack, post: 1111009, member: 9107
That impedance curve looks a bit like that of a speaker with an aperiodic port that needs a bit more stuffing. Those rsl cabs are interesting. They remind me somewhat of Atlantic Technology's HPAS cabs. Although AT's goal was extension, both have unconventional enclosures that feature some sort of novel hybrid/truncated/reverse taper transmission lines with side chamber, and from the looks of it they must damp the active driver a bit differently than by-the-numbers bass reflex. I would actually have been surprised to see the classic symmetric impedance peaks Gene expected.

I have been looking at this. It is not a reverse taper TL. If it were the start of the pipe would be widest. It is more like a horn that is too short. There is an expansion box, throat, and another expansion, just like a horn would have. Then there is that port.

The impedance curve looks like a that of an incorrectly tuned QB4 box. The 3 db point is around 100 Hz and the roll off is fourth order like a ported box would.

I'm not at all convinced that internal contributes anything but bracing. I would like to see the comparison of the same drivers and crossover in a properly deigned QB4 box. My feeling is it would be superior.

The speaker sounds good because the crossover seems spot on and the drivers are perfectly integrated.

As for the bass loading, it seems a mish mash of a too short TL with expansion and taper of a horn and then an attempt as mass loading with a port. Pending further information and data from the company, I'm not impressed with this loading arrangement.

The Speedwoofer on the other hand at first glance looks more promising. Although F3 is fairly high, it is rolling off second order, like a TL would.

I would like to see more measurements of that, and details.

I have tried various configurations over the years to try and reduce the real estate of TLs, including mass loading them with ABRs. The only ones any good were labyrinths. I suspect if that GL4 where a labyrinth it would be much more promising as far as the low end is concerned.
The price would be higher as there would be a lot more internals. However I think the 3db point would be lower and roll off second order, with more low bass, and low Q to boot.
TLS Guy posts on December 31, 2015 08:56
ski2xblack, post: 1111009, member: 9107
That impedance curve looks a bit like that of a speaker with an aperiodic port that needs a bit more stuffing. Those rsl cabs are interesting. They remind me somewhat of Atlantic Technology's HPAS cabs. Although AT's goal was extension, both have unconventional enclosures that feature some sort of novel hybrid/truncated/reverse taper transmission lines with side chamber, and from the looks of it they must damp the active driver a bit differently than by-the-numbers bass reflex. I would actually have been surprised to see the classic symmetric impedance peaks Gene expected.

I have been looking at this. It is not a reverse taper TL. If it were the start of the pipe would be widest. It is more like a horn that is too short. There is an expansion box, throat, and another expansion, just like a horn would have. Then there is that port.

The impedance curve looks like a that of an incorrectly tuned QB4 box. The 3 db point is around 100 Hz and the roll off is fourth order like a ported box would.

I'm not at all convinced that internal contributes anything but bracing. I would like to see the comparison of the same drivers and crossover in a properly deigned QB4 box. My feeling is it would be superior.

The speaker sounds good because the crossover seems spot on and the drivers are perfectly integrated.

As for the bass loading, it seems a mish mash of a too short TL with expansion and taper of a horn and then an attempt as mass loading with a port. Pending further information and data from the company, I'm not impressed with this loading arrangement.

The Speedwoofer on the other hand at first glance looks more promising. Although F3 is fairly high, it is rolling off second order, like a TL would.

I would like to see more measurements of that, and details.

I have tried various configurations over the years to try and reduce the real estate of TLs, including mass loading them with ABRs. The only ones any good were labyrinths. I suspect if that GL4 where a labyrinth it would be much more promising as far as the low end is concerned.
The price would be higher as there would be a lot more internals. However I think the 3db point would be lower and roll off second order, with more low bass, and low Q to boot.
ski2xblack posts on December 31, 2015 02:17
KEW, post: 1108809, member: 41838
In the measurement section, Gene wrote:

The CG4 measured a nominal 8 ohms just like RSL states, never dropping below 7 ohms (6.4 ohm min per IEC requirement). However you can see the box is a little too small for the driver with the asymmetric peaks between the saddle point. To RSL's credit, didn't hear any ill effects in bass. However, in my opinion, a speaker this small should be sealed since a port can't do a whole lot in this scenario.


Did either of you try sealing the port to see if it affected the sound quality? That would be interesting to establish since the port is designed to reduce resonance rather than be a source of added sound (as I understand it).

That impedance curve looks a bit like that of a speaker with an aperiodic port that needs a bit more stuffing. Those rsl cabs are interesting. They remind me somewhat of Atlantic Technology's HPAS cabs. Although AT's goal was extension, both have unconventional enclosures that feature some sort of novel hybrid/truncated/reverse taper transmission lines with side chamber, and from the looks of it they must damp the active driver a bit differently than by-the-numbers bass reflex. I would actually have been surprised to see the classic symmetric impedance peaks Gene expected.
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