Definitive Technology StudioMonitor 45

Bookshelf speaker

Item #: 735SM45

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17 Reviews

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Precise, potent sound for tight spaces

Definitive Technology's StudioMonitor 45 packs an astonishingly big punch into a surprisingly small package. It should — it's the result of more than 20 years of research and development by Definitive in their quest to create speakers with a perfect balance of style, utility, and performance. Each rock-solid cabinet features an advanced 5-1/4" mid/bass driver that delivers plenty of impact and detail, plus a 1" pure aluminum dome tweeter for crisp, extended highs that shimmer. If you're a music enthusiast short on living space, these compact gems should be high on your list of speakers to consider.


" In spite of its almost laughably low price, the SM45 is a speaker that demands to be taken seriously…they were unexpectedly full-bodied and offered an astonishing amount of bass reach (down into the upper 30Hz region)—reach few other small monitors can match. …it provides giant helpings of musical richness, relaxation, and enjoyment at a ridiculously modest price. For these reasons and many more, Definitive's SM45s are a no-brainer recommendation for music lovers whose sights are set high, but whose budgets are limited."

— From Chris Martens' review in The Absolute Sound, April, 2013

Definitive Technology StudioMonitor 45

Definitive's second-generation patented BDSS driver with Linear Response Waveguide™ technology gives this speaker exceptional sound quality.

High-tech driver design for impressive performance

The StudioMonitor 45s are chock full of technology that's also found in Definitive's top-of-the-line speaker models. Its 5-1/4" mid/bass driver uses their latest Balanced Dual Surround System (BDSS) driver design, which places a surround on both the outer and inner edge of the speaker cone. This helps the cone remain more stable as it moves, resulting in clearer, more accurate sound — even at high volume levels. The '45's mid/bass driver also gets Definitive's second-generation Linear Response Waveguide™. This mushroom-shaped post in the center of the cone smooths off-axis frequency response for broad, even sound dispersion and a more realistic sonic "image." That means every listener in the room gets to hear balanced, open sound with lifelike vocals and instruments.

Crisp, sparkling highs

Definitive also equipped the StudioMonitor 45 with their latest 1" pure aluminum dome tweeter. This advanced driver is first heat-treated to relax the crystal structure of the metal, then coated with a ceramic that helps produce clear, sparkling highs without a trace of edginess. You'll easily hear the subtle high-frequency details in your music, like the sound of wire brushes gently sweeping the snare head, or the bell-like ring of a brass cymbal.

pure aluminum dome

A second-generation pure aluminum dome tweeter yields smooth, extended treble.

It's all in the details

Definitive paid close attention to other important design elements, too — both visible and hidden. At its heart, the StudioMonitor 45 uses a sophisticated crossover network with audiophile-grade components that include over-sized inductor coils and Mylar film capacitors. These give you a smoother, flatter frequency response, more powerful dynamics, and faster transients, for sound with real presence and immediacy. Sturdy, vault-like cabinet construction also plays a big role in this speaker's performance. The '45's well-damped, cross-braced enclosure features a specially contoured front baffle with tapered sides to minimize diffraction and vibrations that can color your sound and reduce accuracy. Plus its rear-firing, double-flared port is specially designed to enhance low-frequency impact, while keeping bass distortion low.

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Did you know?
Your new speakers will probably sound better after several weeks of use than they do right out of the box. That's because the material surrounding the woofers will loosen up, allowing the drivers to move more fully. Definitive Technology estimates a break-in period of 24 to 48 hours of playback before the speakers will deliver optimum sound quality. For more information and helpful tips, check out this article from Definitive's website about conditioning your speakers.

Product Highlights:

  • bass-reflex (ported) design
  • second-generation Balanced Dual Surround System (BDSS) 5-1/4" mid/bass woofer delivers clear, accurate sound at high volumes
  • Linear Response Waveguide technology smooths off-axis frequency response for broad, even sound dispersion and more realistic imaging
  • second-generation 1" pure aluminum dome tweeter for clear, extended highs
  • crossover network features oversize inductors and premium Mylar capacitors for audiophile-grade sound quality
  • non-resonant braced construction ensures clean, uncolored sound
  • wood grain matte black enclosure with high-gloss, anti-diffraction baffle and detachable cloth grille
  • frequency response: 35-30,000 Hz
  • sensitivity: 90 dB
  • impedance: 8 ohms
  • recommended amplifier power: 20-150 watts
  • one pair of heavy-duty 5-way binding posts for convenient and secure wire termination
  • 11-5/8"H x 6-3/4"W x 11-5/8"D
  • warranty: 5 years
  • Our 60-day money-back guarantee

Why choose bookshelf speakers?

Bookshelf speakers may be small in size, but they can deliver surprisingly big sound. Some ultra-compact models even fit on a desktop. Most are right at home in tight spaces like shelves, so they're usually good choices for your home theater's rear channels. For the best performance, try placing bookshelf speakers on solid speaker stands to help the sound really "open up." If you want full bass impact, add a powered subwoofer and enjoy punchy sound that's as deeply satisfying as that of floor-standing speakers.

Hands-on research

What's in the box?

Download owner's manual

  • Black bookshelf loudspeaker
  • Detachable black cloth grille
  • 4 Self-adhesive rubber feet
  • Owner's Manual
  • Online Product Registration card

Features and Specs

Enclosure Bass Reflex
Video Shielded No
Tweeter Type Dome
Tweeter Size (inches) 1
Midrange Size (inches) N/A
Woofer Size (inches) 5.25
Woofer Composition Polymer
Woofer Surround Rubber
Power Range 20-150
Sensitivity 90 dB
Impedance (Ohms) 8
Frequency Response 35-30k Hz
Connector Type 5-way post
Bi-amp Inputs No
Height (inches) 11-5/8
Width (inches) 6-3/4
Depth (inches) 11-5/8
Weight (pounds) 12.95
Mounting Bracket Included No
Recommended Stand Height (inches) 28.5"
Parts Warranty 5 Years
Labor Warranty 5 Years

Product Research

Driver Technology
Enclosure Design
Mounting Options

Driver Technology

StudioMonitor Series: The Definitive Technology StudioMonitor 45 is a compact bookshelf loudspeaker designed for use in audio/video entertainment systems. Because the StudioMonitor 45 is a true full-range speaker with extended low-frequency response, it delivers superb performance both as stand-alone speaker and when combined with a separate subwoofer. Due to its compact size, wide-range, high-power handling, and natural articulate clarity; the StudioMonitor 45 loudspeaker is ideal for use as front, center, or surround speaker in a home theater environment.

2-Way Loudspeaker: Each Definitive Technology StudioMonitor 45 loudspeaker features a 5.25" second generation BDSS midrange driver and a 1" pure aluminum dome tweeter.

  • 2nd Generation BDSS Midrange: The 5.25" midrange driver features Definitive's patented Balanced Double Surround System (BDSS) technology that supports the speaker cone at both the inner and outer edges allowing longer, more linear excursion for greater clarity and finely textured inner detail.
  • Pure Aluminum Dome Tweeter: The 1" tweeter is a pure aluminum dome, which has been heat-treated to relax the crystal structure and then coated with a ceramic to produce smooth, extended highs. A new patent pending Linear Response Waveguide smoothes off-axis frequency response and disperses sound over a wider area for crystal clear intelligibility for every listener in the room.

Phase-Coherent Crossover Networks: The crossover network is the real heart of a loudspeaker as it is responsible for perfectly blending together the sound of the various drivers into a musically seamless whole. The sophisticated crossover network design used in the StudioMonitor 45 loudspeaker features premium audiophile-grade components; such as oversized inductors and Mylar capacitors for audiophile-grade sound quality, with linear phase and frequency response. An integrated Zobel network flattens the impedance of the system so that even budget amplifiers will be able to drive the StudioMonitor 45 loudspeaker (although a premium amplifier will bring out all the performance it has to offer). As a result, the audio signal's phase coherence, transient response, and dynamic integrity is preserved for absolutely lifelike music and home theater reproduction in your home.

Enclosure Design

Non-Resonant/Low-Diffraction Cabinet: The Definitive Technology StudioMonitor 45 bookshelf loudspeaker employs a non-resonant MDF braced enclosure that ensures pure, uncolored performance. The specially contoured high-gloss baffle around the drivers and the tapered enclosure sides enhance sound quality by minimizing diffraction distortion.

Bass Reflex Design: The Definitive Technology StudioMonitor 45 loudspeaker utilizes a doubled-flared, rear-firing port for extended bass response with low distortion.

Note: Due to the rear-firing port, the speaker must be placed at least 2" from the wall.


Heavy-Duty Binding Posts: Each StudioMonitor 45 bookshelf loudspeaker is equipped with a pair of heavy-duty, binding post speaker terminals to attach your receiver's speaker wire. The binding post speaker terminals will accept bare wire (up to 10AWG), pin-connectors, spade-connectors, and banana-plugs (single only).

Color-Coded: The speaker's binding posts are color-coded (red/black) for easy identification between positive and negative.

Mounting Options

Table-Top Mounting: The StudioMonitor 45 loudspeaker can be simply placed on a bookshelf, table-top, or speaker stand (such as the Definitive Technology StudioStand, sold separately ). Four self-adhesive rubber feet are included to protect your furniture's surface.

Wall Mounting: The optional PinPoint heavy duty side-grip wall-mounting bracket (121AM41B, sold separately) can be used to wall mount the speaker.

Note: The speaker does not include any type of wall-mount bracket, threaded inserts, or keyhole slots.

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team. They verify what’s in the box, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.

Definitive Technology StudioMonitor 45 Reviews

Average Customer Review:

17 reviews
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This is a great speaker!

Written By Jim E., Washington on Saturday, December 20, 2014

Crutchfield Customer Review (What's this?)

After listening to these speakers for about a month, I'm amazed at the clarity, imaging, and fullness of the sound. I don't want to gush over a $400 pair of speakers, but the sound is so clean and accurate that I find myself just wanting to keep listening. I appreciate them more and more as I continue to listen. There are musical nuances that I haven't noticed before in other speakers. Truly a pleasure to hear. I have no need of a sub with them. Thanks to Buzz for taking my order, and Crutchfield for making this an effortless and pleasant purchase!

Pros: I don't know of anything else this good at this price.

Cons: None.

Definitive Technology StudioMonitor 45

Written By Anonymous, santa clara, ca on Thursday, November 06, 2014

Crutchfield Customer Review (What's this?)

Excellent clarity

Studio 45 Spreakers - Great & Crutchfield Too

Written By Wayne, Ark on Tuesday, September 02, 2014

Crutchfield Customer Review (What's this?)

Great sound for my small listening area. Speakers are impressive right out of the box but are getting more responsive after 8-10 hours use per day. Can't beat for the price. BTW - Can't beat Crutchfield either - they deliver customer satisfaction.

Pros: Small footprint but delivers great sound.

Cons: None

Definitive Technology StudioMonitor 45 Review

Written By PeteD, Cape May, NJ on Monday, September 01, 2014

Crutchfield Customer Review (What's this?)

Excellent speakers for the money


Written By Lance L., New Orleans, La on Wednesday, June 18, 2014

I recommend this product due to clarity and natural sound paired up with a Yamaha AS 500. The treble is not tinny at all and the bass isn't too boomy. However one might consider pairing up with a Definitive Technology ProSub 1000, considering the price range of the subwoofer, if in a medium to larger room.

Pros: Size for smaller rooms, clarity, engineering design, natural sound.

Cons: Bass can be a little short without a sub.

Sound way better than you would expect for this price!

Written By cellhead, Amery,WI on Monday, May 05, 2014

Crutchfield Customer Review (What's this?)

These speakers are amazing, unbelievable value for the money! I have a 9.1 surround system powered by a Yamaha RX-A720 Aventage receiver. Every speaker I had was Polk up until I bought these. I was concerned that they might not voice match my system but the reviews were so glowing I decided to give them a shot and I am so glad I did. I replaced my front "presence" speakers with these and the improvement in the overall sound of my system is beyond impressive. These speakers do everything well: great accuracy, stage depth imaging, etc. They are equally impressive for listening to music as they are for surround sound, adding so much depth and richness to the sound. Can't recommend them highly enough.

Pros: Acccuracy, dynamic range, sound stage, imaging, do everything well!

Cons: None, and the manufacturer says they sound even better after a few days of burn in, can't wait!!!

Big Sound Small Pakage

Written By Robert, Greensboro, AL on Thursday, April 17, 2014

Crutchfield Customer Review (What's this?)

These sound very good. Better bass than other speakers large or small. Someone said grills don't fit snug. Wrong! They fit very snug. It just takes extra effort to get them on all the way.

Perfect for our needs

Written By TimM, Durham, NC on Friday, April 11, 2014

Crutchfield Customer Review (What's this?)

One of the three of us is a professional musician, another is a very active amateur. We make and hear a great deal of live music, and these speakers sound very accurate to all of us. Even without a sub-woofer, they deliver a full bass sound. They would be 5 stars but for the covering grilles that don't clip on quite snugly.

Definitive technology studio monitor 45

Written By ogl, Terre Haute, In on Monday, December 30, 2013

Crutchfield Customer Review (What's this?)

excellent speakers, Highly recommended

Pros: excellent speaker that delivers. highs and lows are reproduced perfectly. A best buy!

Cons: none

Great sound in a great package

Written By gnakasato, Louisville, KY on Sunday, December 08, 2013

Crutchfield Customer Review (What's this?)

I placed these speakers on the bookshelves on each side of the fireplace in my 22-foot tall living room. And they have absolutely no trouble filling up the room with amazing sound clarity without distortion at maximum volume. I use them to listen to music and watch movies (TV above the matle). And I am very impressed. The amount of bass coming from them is impressive given their relatively small size. Even the Audyssey equalization system in my Onkyo "THX Ultra"-certified receiver detects them as "Full Range" (maybe because they are encased between levels on the bookshelves which helps increase the lower frequencies reproduction). The previous Mythos Gem XL (compact) speakers I had in the same location had a recommended crossover point of 120Hz by the same Audyssey MultiEQ system, so it's not all down to location. Big step up in sound clarity and reproduction. I use them with a subwoofer while setting their crossover point at 60Hz (per DT recommendations) and the fullness of sound is just about perfect. You will be hard pressed to beat that for $400 delivered. And unbeatable for close to $300 (I got open box ones and they arrived in mint condition). Highly recommended.

Pros: Excellent sound quality, amazing value, great looks, full range sound reproduction.

Cons: None, zero, nada.

DT StudioMonitor 45s

Written By PB in VA, Northern Virginia on Monday, September 23, 2013

Crutchfield Customer Review (What's this?)

As I fully expected, DefTech delivers the goods again. I've owned 3 other DT speaker sets over the years, including the awesome Mythos STS towers, BP8s and StudioMonitor 450s and am always pleased with their performance. DT has long mastered the art of big bass from small enclosures, but have significantly improved their tweeters in recent years for more pleasing highs, making for better long-term listening. I needed small but relatively full range speakers for a recently-completed 20x16 exercise room so I purchased these along with Sanus NF30 stands. I paired with my 15 year old Adcom GFP-565 preamp and GFA 500 amp, total overkill at 200 wpc but a great way to break them in. I've since moved to a Yamaha A-S500 integrated which is really more appropriate for these speakers, with the bonus of an i-pod dock and subwoofer out to which I am adding a Polk PSW 111 to supplement the bass a bit. Right out of the box the StudioMonitor 45s visually impress with a slightly arched top and rock solid feel, fit and finish. The grills with the flimsy plastic plate at the bottom are the only design misfire in my opinion. Music comes across with as impressive detail and imaging as you could hope for at this modest price point, and they are remarkably full-range with great punchy bass. You simply can't go wrong with DT in general and the 45s in particular for a budget system - highly recommended! Oh, and Crutchfield ordering is seamless and shipping is super fast!

Pros: Attractive speakers, and remarkably full-range. Can handle the power and fill a room without strain. DT is renowned for bass output but are getting it right in the mids and on the top end as well these days with a more refined metal dome tweeter and improved crossovers. Binding posts are of high quality as well.

Cons: Grills have a flimsy plastic bottom nameplate that detracts from the otherwise nice aesthetic, but this is just a picky detail that has no bearing on performance.

2 Channel Goodness

Written By JamieB, Long Island on Tuesday, July 02, 2013

Crutchfield Customer Review (What's this?)

My 20 year old got me to dust off the old turntable so he could play some new vinyls. I had been playing music through a modest 5.1 speaker system powered by a 10+ year old home theater receiver. I decided to build up a 2-channel music system and I needed better speakers. After a fair amount of research, I decided on the DefTech SM45s based on reviews and my budget. I paired them up with a separate pre-amp and amplifier combination and I could simply not be more impressed with the sound quality. They reproduced LPs, CDs and digital music with more clarity and depth than I would have thought possible for such compact, reasonably-priced speakers.

At realistic music levels, they were crystal clear. The definition of cymbals, vocals and acoustic instruments was studio quality. I blasted them on 70's rock standards and they played cleanly even at uncomfortably loud volume levels. Their deep bass extension was completely unexpected despite the published specs.. There was well defined kick to drums and natural reproduction of acoustic and electric bass instruments. Mids and highs were well balanced. I discovered nuances to my music that I had forgotten or never knew were there. The new vinyls were amazing sounding...even though they were not always my genre.

The ordering process was painless. The shipment arrived in 2 business days. I will NOT be using Crutchfield's return policy.

Pros: Great Sound quality. Quality/dollar ratio off the charts.

Cons: If your amp has the power, and you push beyond what you should, the mid-woofer can bottom out before you hear any other audible distortion.

Great Companion...

Written By VictorA, San German, PR on Tuesday, May 21, 2013

Crutchfield Customer Review (What's this?)

You can use this beauties as the main and surrounds of a sub-sat system. I`m using them as surrounds with the sm-55 as the main. It`s a match made in heaven. Great sound and good bass for its size. Its ported design works great... Highly recomended...

Pros: Style, construction, performance

Cons: None

Very Pleasing Sound Quality

Written By Bob L, Ballwin, MO on Wednesday, January 02, 2013

Crutchfield Customer Review (What's this?)

These speakers deliver very pleasing overall sound, especially given their size. I have them mounted on 30" stands which I highly recommend. My rating is based on owning many speakers over the years including currently a pair of Golden Ear Technology Triton Two speakers (very highly rated). I would buy the Def Tech Studio Monitor 45s again.

Pros: Great sound, build quality and finish. Very reasonable price for what you get.

Cons: None

Good stuff

Written By Anonymous, san jose, ca on Friday, November 09, 2012

Crutchfield Customer Review (What's this?)

They sound terrific!!!! love the clarity, my main cause for purchase was in music listening, and they deliver loud, crisp sound

Audiophile Speakers For Sure

Written By roscoe, Los Angeles on Wednesday, November 07, 2012

Crutchfield Customer Review (What's this?)

Awesome speakers for the size. Deep bass that is every bit as good as my JBL G300,

I am upgrading to SM 65 & therefore my 45's have been returned to Crutchfield. Anyone who gets these speakers at an open box price is very lucky as they have been treated with TLC & are completely broken in.. Thanks Crutchfield for the 60 day mbg.

Cons: I am not to crazy about the gloss front but that is a secondary matter of personal preference.

Great Sound, Great Price - A Steal!

Written By SV, Falls Church, VA on Wednesday, August 22, 2012

After the surrounds got worn out on the woofers and bass radiators of my old speahers, I got tired to listening to CDs on portable players and headphones. My music tasted go to classical and classic rock. My requirements: musical transparency. Add nothing, subtract nothing. Powerful response down to the very bottom (Pipe organs) to the very top from a whisper to a roar as required by the music, all at a price I can afford (low). After listening to several systems at various price ranges, I settled on the Def Tech SM 45s and a prosub 1000. The 45s are amazing! Excellent musical transparency, clarity, tonal balance, and a sound stage that is both wide and deep. The SM 45s could please me on almost all my recordings even without the subs. I played a classical guitar recording without the sub, and I could visualise the guitarist in my room. Yes, the sub adds the bottom end seamlessly, but the SM 45s played by themselves at a good sound level (and they will play loud) have a surprising amount of bass, especially considering their small size and low price. As I said - a bargain at twice the price, a steal at their price!

Pros: Great sound, wide & deep imaging, good looks, flexible placement options, very affordable

Cons: not a con really, just a result of their size: Lacking the only the very deepest of bass, but has more bass than you would believe from a speaker this small. If your receiver has a "Loudness" button, use it. If you don't need the bottom octave, buy them or buy a (very good) sub to go with them!

Get everything you’ll need to enjoy your new Definitive Technology StudioMonitor 45

You'll need speaker wire to connect your speakers to your amp or receiver. No wire is included with this speaker.
Add connectors to your bulk speaker wire for a neater, easier, and more reliable installation.
Cut your speaker wire to the exact length you need.
Get your speakers off the floor and at ear level where they are meant to be.
Mount your speakers safely on the wall.
Original Monster Cable

Original Monster Cable

With gold pin connectors (15-foot pair)

Item #: 119OMC1515


Add to Cart
Monster Cable SuperFlat™ Mini

Monster Cable SuperFlat™ Mini

Decor-friendly speaker cable with gold pin connectors (50-foot spool)

Item #: 119SFLM50


Add to Cart
AudioQuest Type 4

AudioQuest Type 4

Speaker cables with pre-attached banana connectors (10-foot pair)

Item #: 703T410BFS


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Monster crimp-on mini bananas

Monster crimp-on mini bananas

1 pair, 16-gauge

Item #: 119MTMB


Monster crimp-on banana connectors

Monster crimp-on banana connectors

1 pair, 12-gauge

Item #: 119MTRB


Monster Twist-on Mini Banana Connectors

Monster Twist-on Mini Banana Connectors

2 pair, 16-gauge

Item #: 119MTTMH2


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Monster Twist-on Banana Connectors

Monster Twist-on Banana Connectors

2 pair, 12-gauge

Item #: 119MTTRH2


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Monster Cable Twist-on Angled Gold Pins

Monster Cable Twist-on Angled Gold Pins

4 pair, 12-gauge

Item #: 119AGPTRH2


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AudioQuest X2 Speaker Cable

AudioQuest X2 Speaker Cable

14-gauge cable, connectors optional (30 feet, Gray)

Item #: 703X230G


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AudioQuest G2 Speaker Cable

AudioQuest G2 Speaker Cable

16-gauge cable, connectors optional (30 feet, Gray)

Item #: 703G230G


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Definitive Technology StudioMonitor Stand

Definitive Technology StudioMonitor Stand

StudioMonitor all-metal speaker stands

Item #: 735SMSTND


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Pinpoint AM-41

Pinpoint AM-41

Side-clamping speaker wall mounts

Item #: 121AM41B


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IsoAcoustics ISO-L8R155 Monitor Stands

IsoAcoustics ISO-L8R155 Monitor Stands

Supports medium speakers

Item #: 892L8R155


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Looking for more? Check out the next model in this lineup.

Definitive StudioMonitor 55

Get even bigger sound

The Definitive Technology StudioMonitor 55 offers these features:

a 6-1/2" woofer with cast aluminum basket for more powerful, accurate sound

a top-mounted bass radiator for outstanding low-frequency response

dual biding-post speaker connectors for bi-wiring or bi-amping