Onkyo R-MS55 Review: 8-In 8-Out DSP Amplifier and the FDS05B Bluetooth Box
The Onkyo R-MS55 is an 8-in 8-out DSP amplifier with eight high-level inputs, eight low-level outputs, a 31-band equaliser and a built-in eight-channel amplifier that Onkyo rates at 8 x 50 W maximum. Its Indian MRP is ₹21,990, the fourth-lowest of the eight Onkyo DSP amplifiers we list and the lowest among those with eight or more amplified channels. It suits a car that keeps its factory head unit but has more than four speakers to process, and we cover the optional FDS05B Bluetooth box below. The amplifier is on our Onkyo R-MS55 product page.
Quick summary
Eight high-level inputs, eight low-level outputs and eight amplified channels rated at 8 x 50 W maximum. Onkyo publishes no RMS figure.
A 31-band equaliser with six preset music scenes. Bluetooth and USB music playback are listed; a low-level or optical input is not.
Against the R-MS25 it doubles the amplified channels and high-level inputs, for an MRP ₹2,000 higher. The R-MS66 lists 8 x 70 W max at an MRP ₹6,000 above the R-MS55's.
The optional FDS05B Bluetooth box is ₹7,990 MRP. We found no owner reviews or independent tests in October 2026.
Onkyo R-MS55 specifications
Specification | R-MS55 |
|---|---|
Type | DSP amplifier, 8-in / 8-out |
Maximum power | 8 x 50 W (max only; no RMS rating listed) |
Inputs | 8-channel high level, Bluetooth, USB music playback |
Outputs | 8-channel low level, plus 8 amplified outputs |
Equaliser | 31-band, 6 preset music scenes |
Frequency response | 20 Hz – 20 kHz |
High-level input impedance | 240 Ω |
Power supply | DC 9 – 16 V |
Dimensions | 180 x 142 x 43 mm |
Weight | Approx. 0.95 kg |
Setup software | Onkyo R-MS Series, PC and Android (per our listing) |
Optional add-on | Onkyo FDS05B aptX and LDAC Bluetooth box, ₹7,990 MRP |
India MRP | ₹21,990 |
Figures come from Onkyo's R-MS55 product page and our store listings, which agree. That page lists no RMS rating, crossover, time delay, remote or Bluetooth version.
What 8 x 50 W max does and doesn't tell you
A per-channel max figure leaves out how long a channel can hold 50 W, into which impedance, at what supply voltage and with how much distortion. With eight channels it also doesn't say what the amplifier delivers when all of them are driven together from one power supply. Makers differ on how far max sits above continuous power: Alpine's manual pairs 35 W RMS with 70 W max for the PXE-R80-8, while Zapco's manual pairs 35 W RMS with 100 W max on the Class AB channels of the HB 810 II 8AD. With no fixed ratio, we won't turn Onkyo's 50 W into an RMS number. Read it as a ceiling for each channel, not as continuous output across all eight.
Eight inputs, eight outputs and tuning
Eight high-level inputs let you tap up to eight speaker-level signals from a factory head unit, the usual way to add a DSP to a factory touchscreen system without replacing the head unit. No low-level input is listed, so a later head unit with RCA outputs would not have a listed input to use; the R-MS66 lists two. The eight low-level outputs can feed external amplifiers, for example for a subwoofer, while the eight amplified outputs drive speakers directly. The listing doesn't say how the two sets map onto each other, so confirm the routing first.
Tuning uses Onkyo's R-MS Series software for PC and Android, per our listing. Onkyo's download page lists R-MS Series apps but names no individual models, and neither it nor the R-MS55 page lists crossover or delay controls. Keep the head unit's own tone controls flat while tuning, as they alter the signal before it reaches the DSP. VA3 Car Studio does DSP tuning if you would rather have eight channels set up for you.
Onkyo FDS05B Bluetooth box: do you need it?
The R-MS55 lists built-in Bluetooth with no version or codec. Our Onkyo FDS05B listing describes a separate aptX Bluetooth box with a Qualcomm Bluetooth chip, made to add aptX and LDAC music to the R-MS25, R-MS55 and R-MS66. At ₹7,990 MRP it takes an R-MS55 with the box to ₹29,980. The listing doesn't say how the box connects, whether it needs its own power feed or whether it replaces the built-in Bluetooth. aptX and LDAC also need a phone or player that supports them, so check yours first, and ask us how the box connects before you order both.
What owners and reviewers say about the Onkyo R-MS55
When we checked in October 2026, we found no owner reviews, forum threads or independent tests of the R-MS55 or the FDS05B. Onkyo's page is a specification table, which is promotional rather than a review, and our listings show no customer reviews. The closest items are a YouTube video titled ONKYO DSP R-MS 10 , R-MS 25 ,R-MS 55 6 CHANNEL DSP AND 8 CHANNEL DSP, which we couldn't open and so can't summarise, and a June 2026 Team-BHP post that lists an R-MS66, a different Onkyo model, in an active system without giving an opinion of it. Sound quality, software behaviour and long-term reliability therefore remain open questions. If you own an R-MS55, tell us how it has gone.
R-MS55 against the R-MS66, Alpine and Zapco
All four units below list eight amplified channels, using each maker's published figures.
Listed figure | Onkyo R-MS55 | Onkyo R-MS66 | Alpine PXE-R80-8 | Zapco HB 810 II 8AD |
|---|---|---|---|---|
India MRP | ₹21,990 | ₹27,990 | ₹68,999 | ₹54,990 |
Power rating | 8 x 50 W max | 8 x 70 W max | 35 W RMS x 8, 70 W max (10% distortion) | 4 x 35 W + 4 x 100 W RMS at 4 Ω |
High-level inputs | 8 | 8 | 6 | 8 |
Low-level inputs | Not listed | 2 | 2 | 2 |
Crossover and delay | Not listed | Not listed | Listed | Listed |
Our live R-MS66 post covers the model one step up. It adds two low-level inputs, an optical input, two more low-level outputs and a 70 W max rating per channel, for an MRP ₹6,000 higher. Against the R-MS25, the R-MS55 doubles the high-level inputs and amplified channels, lists no low-level input and costs ₹2,000 more. The Alpine and the Zapco publish RMS ratings and crossover and delay controls that Onkyo's R-MS55 page does not.
Who should buy it, and who shouldn't
Buy the R-MS55 if you keep a factory head unit, want eight processed and amplified channels with a 31-band equaliser, and accept a max-only power rating. Look elsewhere if you need a low-level or optical input (the R-MS66, or the four-channel R-MS26), published RMS power with crossover and delay controls (the Alpine and Zapco units above), or only four channels, where the R-MS25 costs ₹2,000 less.
Installation notes for Indian cars
At 180 x 142 x 43 mm and about 0.95 kg, the R-MS55 needs a flat, ventilated spot away from heater ducts and direct sun, because a cabin gets very hot in an Indian summer. Onkyo lists a 9 – 16 V supply but no fuse rating, current draw or cable gauge, so the power wiring has to be sized at fitting, with battery voltage at idle and the AC on in mind. Eight high-level inputs can mean up to eight speaker-wire pairs to identify and tap at the head unit.
VA3 Car Studio in Ghaziabad offers professional installation, and can make speaker pods and door baffles for the speakers the R-MS55 will drive.
Price and where to buy
The Onkyo R-MS55 has an MRP of ₹21,990 and the FDS05B box ₹7,990, which comes to ₹29,980 together. VA3 Car Studio often sells below MRP, so check current prices on the R-MS55 listing and the FDS05B listing. Warranty terms are set by Onkyo; confirm them with us before ordering.
The bottom line
The R-MS55 puts eight high-level inputs and eight amplified channels in a 0.95 kg box. The trade-offs are a max-only power rating, no listed low-level or optical input and no reviews we could find. Add the FDS05B only if you want aptX or LDAC, and ask us how it connects first.
Onkyo R-MS55 FAQ
What does 8-in 8-out mean on the Onkyo R-MS55?
Eight speaker-level inputs take the signal from a factory head unit, eight low-level outputs can feed external amplifiers, and eight amplified outputs drive speakers directly at up to 8 x 50 W max. How the channels map internally isn't stated.
Is the R-MS55 rated at 8 x 50 W RMS?
No. Onkyo publishes 8 x 50 W as MAX Power only. It is a per-channel ceiling, not continuous output, and it doesn't say what all eight channels deliver together.
Does the FDS05B Bluetooth box work with the R-MS55?
Our listing names the R-MS55, R-MS25 and R-MS66 as compatible and says the box adds aptX and LDAC Bluetooth music. It doesn't say how the box connects, so ask us before ordering.
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