rolls A- B Box, Compact (SX45)

(10 customer reviews)


Brand Rolls
Size Compact
Item Dimensions LxWxH 5 x 5 x 5 inches
  • Product Type: Sound And Recording Equipment
  • Package Quantity: 1
  • Package Dimensions: 19.304 cms (L) x 12.192 cms (W) x 6.604 cms (H)
  • Country Of Origin: China
SKU: B00102VWJK Category:


The SX45 is a unique frequency dividing device for small sound reinforcement applications. The unit features a 12 dB/Octave roll off rate, a frequency dividing range of 50Hz to 2.5kHz, and an external power supply for noise reduction. * 12 dB/Octave ro

From the manufacturer

About Us

Rolls is a company specializing in audio electronics manufacturing. Products include signal processors, amplifiers, mixers, signal sources, and interface accessories.

Rolls began in 1989 when David O. Di Francesco introduced the HR100 amplifier, the HR11c Microphone Processor, the HR6x mixers, and the HR210 eq at the New York AES Convention.

Additional information

Weight 1 kg
Dimensions 5 × 5 × 5 cm
Item Weight

‎1 Pounds

Product Dimensions

5 x 5 x 5 inches



Item model number


Date First Available

November 20, 2007





10 reviews for rolls A- B Box, Compact (SX45)

  1. Stuart Cohen MSW

    Excellent CrossoverUsing for a multi speaker, multi amp system. The Rolls SX45 is an excellent product. The SX45 works perfectly and doesn’t color the sound.

  2. Bruce Mellinger

    Nice little boxDoes exactly what I wanted and does it very well.

  3. Bruce

    It does what it’s supposed to do!I bought this to add a subwoofer to my Sony GTX-PG10 Bluetooth speaker which is a larger type speaker with ok but somewhat midrange-ish boomy rather than Thuddy base. The Sony RCA Audio inputs. The Rolls unit totally fit the bill. Some reviewers complains about power supply issues causing unwanted noise, but so far I have not had that problem, and if I did, I would just by another power supply. There are plenty of controls on this unit to really dial in the sound you want. A nice little feature associated with the main input volume is that it has a red LED clip light indicator, but even when the volume cranked with the clip light staying solidly on, I can’t hear any distortion. I st the the main input volume so the clip light occasionally blinks on.The only draw back to this otherwise fabulous little unit is that it doesn’t have a power switch. So you either have to plug and unplug it or plug it into a power strip with a switch or one of those switches that plug directly into a receptacle. No big deal, especially at this price point. It’s a solidly built little unit.

  4. jhud

    Great Active CrossoverI was searching for a passive or active crossover to get the lower bass frequencies off the smaller Maggie speakers and onto a subwoofer. This unit did this very well. The Rolls sx45 is very flexible. I can adjust overall input from the preamp on the sx45 as well as the crossover frequency and the level of the upper and lower output to the amp driving the small Maggie speakers and to the active subwoofer. Some of the reviews I read had some issues with the sx45. Rolls may have upgraded the switching mode power supply (smps) from earlier units. I did not have any issues and the unit has been flawless. Using the sx45 crossover cleaned up the Maggie’s allowing them to reproduce the upper frequencies without any congestion from the low bass. Soundstage, clarity, depth, are significantly better. The Rolls sx45 would improve any system that has main speakers that don’t reproduce bass below 35-40Hz by only sending those low frequencies to a subwoofer. I set the crossover on the sx45 to about 90Hz for the best results in my room.

  5. K. Hunter

    Fills the void for consumer (rca in/out) crossover.I’m using the crossover for my pc sound setup which has Tannoy Gold 7 powered monitors and a diy powered sub using a Peerless XLS 10 woofer and passive radiator and 300w plate amp. Overall it sound very good but the crossover adds just a bit of noise. You can work most out with proper level/gain settings though.Biggest issue I have with the SX45, and the reason for only giving it 4 stars, is when powering up the system the SX45 causes a thump in my Tannoys since these speakers do not have a soft/delayed start. My sub has a soft/delayed start so it does not thump. If the sub amp is already on when I power cycle the SX45 then it would thump also. I get around the thump issue by turning down the “high level” knob to 0 each evening when I shut down the system. When powering up the SX45 the clip light blinks once and that is when it causes the thump.

  6. biggvsdiccvs

    You get what you pay forThis was the only small line-level crossover box I could find. I would buy something better, but it would have to be rack-mount and would take too much room. The box I got (new, through Amazon) had a couple of problems:1) One of the output jacks had a bad solder joint. At first, I blamed the cable, but the problem turned out to be with the box itself. I soldered the connection on the board, which fixed the problem. They would probably replace the box under warranty, but it was simpler for me just to do this.2) The Low Level volume control (i.e. the one controlling the level of the low output) only controls the level of the stereo low output, but not the common (mono), which will be used in most cases for the subwoofer amp. This is by (cheap) design. A quick hack is to connect the center pins of the coupled low volume control pots, turning the regulated low stereo outputs into the regulated mono outputs. There don’t seem to be any side effects.I’m not sure how well matched the low and the high outputs are in terms of roll-off frequency and phase distortions; this is actually pretty important in a crossover. It didn’t seem to sound as well as complementary software filters sending signals to multiple outputs of a sound card, but this was a very subjective test using a particular piece of music with certain speakers etc. Using a box like this is certainly more convenient.I find that I sometimes have to adjust the crossover frequency and low level to get the best sound for a particular piece of music. I’ve never had a crossover with easily adjustable frequency; I thought this had to be done once to fit the room and the speakers; maybe I was wrong, and maybe it’s due to the imperfections of this box.Overall, after fixing the connection problem and hacking the Low Level volume control, I can use it, and think the price basically was reasonable, despite these problems.UPDATE: I compared the phases of the input and the high and low outputs. As I suspected, high and low outputs are in counterphase, which is what caused the strange sound and the constant need for adjustment. More specifically, with respect to the input, the high is in counterphase and the low is in phase. A while ago I started using just the low output of this box (for the subwoofer), and the stereo speakers were connected directly to the signal source, i.e. to the input of the crossover. So it basically works as lowpass filter with an adjustable cutoff frequency. I set it approximately to the 3db roll-off frequency of the stereo speakers and everything works great. This way the box could be used without the mod described above (i.e. the the LP-out mono volume could be controlled by the input gain knob, since HP-out is not used). However, I definitely would not recommend buying any Rolls products, unless it’s for a project. I may need another crossover for a different system, so, if anyone can recommend a similar product without any of these problems, please let me know.

  7. Stanley

    Another great product from Rolls!Not seeing a lot of choices here and this may be the only unbalanced RCA (single center conductor) crossover available in this price range.Plenty of the xlr type, but then amps with xlr connections would be needed.The frequency control knob range is 50hz – 2,500hz high/low so typical applications are:* Home HiFi – Woofer & Tweeter* PA – Woofer/Horn Tweeter (Identical power amps will provide the best results, btw)* 2.1 satellite speakers with existing passive xo’s. The Low and High would be used and not the mono sub out.The mono out is the only bell and whistle that I see, which would typically be connected to a sub plate amp (or similar) that has separate low frequency & level controls.I was a little worried this was another glorified “car crossover” with new case and 12 volt power adapter, not here, this little box is whistle clear and my tweeters never sounded better. The fast set up is great, however be very careful not to connect “low out” to the amplified tweeter. There won’t be any second chances and can toast a tweeter winding in a second or two. That said, designing, testing and the costs involved for passive crossover boards is a nightmare for the non-engineer. As they say – Go Active Man!!Update: As mentioned the polarity is reversed Low-High; my unit is “backwards” so you’ll want to check that by ear or mic testing.[EDIT] After using this xo in several applications I discovered the polarity is not reversed, but has more to do with the speaker selection.Would need a sound engineer to explain this phenomena, but anyone can test a speaker phase with computer/mic and free speaker testing download(s).The image below is out-of-phase, so drastic, any computer mic will show the huge dip in the response.

  8. Timothy Wells

    Rolls problematic active crossover that is over activewell I was happy with this crossover until I woke up in the middle of the night to a thumping sound that was very annoying, walked around the living room trying to figure out the thumping I was hearing and after a few minutes realized it was the subwoofer ,I at first thought that the auto sense turn on with the powered sub was defective I unplugged the sub and hooked another sub I have to the crossover and with the system all shut off still the other sub started to thump every 30 seconds. So I confirmed that the crossover even when turned off was leaking enough from a bad capacitors in the power supply. Really sad ,because I really wanted to like this crossover. Ended up sending it back and took the time to build my own active crossover with a pre-assembled board from ebay China store and two Aiyma tube buffer pre amps as the source to have volume nobs to balance the signals to the subwoofer and the power amp for the monitors , I then read the comments on the crossover from Rolls product review and I saw as much new. Feedback as positive feedback .poor quality control is the problem .

  9. Willy

    My 2.0 desktop speakers are now 2.1 with a subwooferI have a set of Swan M200 MKIII desktop speakers. They sound great, but are only 2.0 speakers and don’t have very musch low end bass. So I added an Energy M6 subwoofer to the setup, however this sub does not have built in high level crossover outputs. So I added this device and the setup works very good. Now I can use my desktop speakers with a subwoofer to properly crossover the highs and lows and get 2.1 sound.The unit is small enough to keep under my lcd monitor without being obtrusive.One complaint is adjustment knobs are not centered and point a little to the left, so I am not sure which is correctly centered the knob or the label. Maybe I can open up the case and center the knobs better, but the offset is minimal. Also, there is no power button or autosensing off, but this was expected when ordering this device.***Update, I did notice the low level knob does not control the mono low outputs. But I simply installed a stereo rca cable on the regular low outputs and feed that into my subwoofer. Also, my sub has phase adjustments, however this wasn’t needed as the phase sounds correct at the subwoofer default settings. I could not adjust the knobs to center better, they are soldered on with no way to twist and adjust them.So if you are looking to add a subwoofer, but your subwoofer does not have high level crossover outputs, then this device will let you add a subwoofer to a 2.0 speaker setup.

  10. jrcrwfrd

    This is a great device.For years I have been trying to build a sound system played out doors with high fidelity equipment that would have an audiophile sound. This device allows you to channel low bass to the sub-woofer while channeling just the mid-range and high frequencies to the stereo array. This concentrates amplifier power to the designated speaker while protecting the amplifier and the speakers from distortion. Our guests were amazed at how loud and how clean the music sounded. Unlike in the past, nothing overheated or were any voice coils melted. 400 watts RMS to the sub-woofer and 100 watts RMS to the stereo array did the job with ease with the Rolls unit in control of the crossover points.

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