Dayton Audio OPAL1 Bookshelf Loudspeaker Review

Dayton Audio OPAL1 Subwoofer-Like Bass from a Bookshelf?

When regarding finished consumer products, Dayton Audio has established a reputation for very low-cost and high-value audio products. Some favorites that we have reviewed were the MK442T floor-standing speakers and SUB-1500 subwoofer. For many years now, their B652 bookshelf speakers have been considered a classic in the category of extremely low-cost yet competently-designed loudspeakers. So when they asked if I would be interested in reviewing their latest creation, the OPAL1 bookshelf speakers, I agreed without asking any questions. I assumed they would be in line with what I had seen from their other speakers and subs, which is that they are highly budget-minded but decent products. Upon receiving and unpacking them, I was shocked to find some heavy-duty 20-pound bookshelf speakers with a gloss finish! These look and feel like luxury products − but from Dayton Audio!? It was at that point that I learned their pricing was $800 per pair. This is so unlike you, Dayton Audio!

It certainly wasn’t as if Dayton Audio didn’t have the means or capability to make higher-end products. Their loudspeaker kits and separate components could be very high-performance and somewhat costly pieces. Rather, they simply never seemed interested in tackling upscale, finished loudspeaker products in the past and were always more interested in producing the highest bang-for-the-buck speakers at the most affordable prices possible. With the OPAL1, it seems that has now changed. So what does the OPAL1 bring to the table that Dayton Audio would take such a radical departure from their traditional business practices? Let’s dig in to find out…

OPAL 1 Packing and Appearance

The OPAL1s arrived at my doorstep in an uncharacteristically heavy package for Dayton Audio speakers. Both speakers came in a single box, so they do not ship individually. They were double-boxed with an additional layer of cardboard to help remove the speakers from the inside box, so the lengthwise panels were protected by three layers of cardboard. Inside the cardboard, the speakers were sandwiched between thick polyethylene blocks to protect them from shocks. The speakers themselves were wrapped in some drawstring cotton sacks to protect against moisture and scuffs. Overall, the packing was quite good and protected these speakers from the usual abuses of parcel shipping services.

Once unpacked, the OPAL1s revealed themselves to be gleaming white boxes with some beefy-looking drivers installed. The pair I received came in a gloss white finish, but they can also be had in gloss black. The edges have a very slight rounding, and that does help to soften the appearance a bit, but the enclosures are still just oblong boxes without any larger shaping. Aside from the tweeter and woofer, the only other visual feature on the OPAL1’s front baffle is a Dayton Audio badge near the lower edge. The woofer has a very beefy surround and a carbon fiber cone, so it looks like it means business. The tweeter dome is protected by a fine mesh cover, so the dome itself isn’t easy to see. For those who don’t want to see the drivers, the supplied grille hides the front baffle with an acoustically transparent black fabric. In my opinion, the grille dulls the OPAL1’s appearance, so I would leave the grille off if possible.  

The rear of the speaker deserves mention for its appearance as well. Two passive radiators that look just like the bass driver cone occupy nearly the whole of the rear panel. It doesn’t leave much room for the binding posts, but Dayton Audio has managed to sneak them in at the lower left corner of the rear panel. The product information label is handled cleverly, and it follows the curve of the lower passive radiator with a reflectively colorful top coating.

Overall, the OPAL1s look like pretty conventional high-end speakers. Dayton Audio has played it safe in not chasing any flamboyant styling cues, and I think that will pay off for them.

OPAL 1 Design Analysis

The OPAL1 bookshelf speaker looks as though they are designed to get as much low-frequency extension and dynamic range as possible out of its compact cabinet. The heart of this speaker is the bass driver, a member of Dayton’s Epique series, the E150HE 44. To squeeze a lot of bass out of a small container, the driver needs a lot of excursion, and this driver is positioned to do just that. It uses a 5 1/2” diameter carbon fiber cone attached to a very beefy surround and a spider that is as large as the cone itself.

  
The bass driver uses a cast aluminum basket that leads down to a very curious motor structure that Dayton Audio calls the “Multiple Magnet Air Gap,” or MMAG. This motor has two magnetic assemblies: a large “main” magnet and a ring of 6 smaller “gap-balancing” magnets. These gap-balancing magnets are supposed to create a more stable magnetic field over a larger gap. Two top plates sandwich the gap-balancing magnets. The bass driver uses an underhung coil, and this type of design typically needs a lot of magnetic flux over a wide area to work well. Indeed, the magnet used in this driver is a big one, about as large as the cone itself, and with a 1” thickness. It weighs over 8 pounds alone − one of the heaviest I have seen in a 5 1/2” driver. Dayton claims this driver has zero loss of magnetic force out to 10mm of excursion, and an incredible 14mm of Xmax (at 70% Bl). That is pretty stunning for a 5 1/2” bass driver, especially one with as wide a bandwidth as the E150HE 44 (which is specified to have a smooth response up to 3kHz).

The OPAL1 is specified to handle 200 watts of power, most of which would go to the bass driver, and that means it will need a substantial amount of coil and cooling. Typically, small bass drivers with high excursion and lots of coil mass also have lots of induction, but the split gap topology and dual voice coil design seem to do a lot to mitigate that. The E150HE EE also uses a full-length copper sleeve on the pole piece to reduce induction effects. Induction can dramatically limit the bandwidth of a driver, as well as increase even-order distortion. With a claimed smooth response up to 3kHz, this driver seems to have addressed that problem nicely.

 

This unique bass driver is paired with Dayton Audio’s best soft dome tweeter, the RST28F-4. This 1 ⅛” silk dome uses a tuned rear chamber for better control of the low end of its response. It also has a copper shorting ring and a phase lens for a smoother response at the top of its bandwidth. A ferrofluid-cooled motor system, along with a big ferrite magnet, should greatly assist against thermal compression. With a 710Hz resonant frequency (Fs) and a usable response from 1.4kHz to 20kHz, it looks to be a good pairing with the Epique bass driver. 

The woofer crosses over to the tweeter at 2.3kHz using a 12dB/octave high-pass filter on the tweeter and an 18dB/octave low-pass filter on the woofer. Inside the cabinet, we see a slew of heavy-duty poly-film capacitors, resistors, and air-core inductors. The crossover circuit is divided into two separate boards, one installed on a side panel and the other installed on the bottom panel. I would guess that mounting those components on a single circuit board would have made that board too large to fit inside the enclosure. Separating out the crossovers also has the benefit of improved signal isolation between the drivers too. The build of this crossover circuit certainly befits the high-end status that this speaker is vying for. Connectivity is a pair of five-way binding posts that jut out of the cabinet. 

The OPAL1 uses two passive radiators to shore up the low end. As was mentioned before, these radiators look identical to the bass driver from the outside of the speaker. Given the Xmax of the Epique bass driver, two of these radiators are needed. (As a rule, passive radiators ought to have double the displacement of the bass driver.) These radiators are specified to have 19mm of Xmech each, so they more than meet the requirement for doubling the bass driver displacement.

The enclosure is made from ¾” MDF panels all around, and there is a windowpane brace bisecting the cabinet in a lengthwise direction. Every surface that doesn’t have crossover components or drivers is covered with a layer of acoustic stuffing. The interior of the enclosure is painted, a nice touch since exposed MDF can swell if exposed to high-humidity conditions. There is also padding around the wiring, which is a good idea to prevent the audible buzzing of the wires vibrating against interior objects. There are no installed feet, but Dayton Audio has supplied the OPAL1s with some adhesive rubber feet that the user can install if they wish.  

Zooming out, the OPAL1 bookshelf speakers look to be well-positioned to produce a lot of bass for their modest enclosure size. However, that doesn’t come without a cost; its specified sensitivity is a very low 78.5dB for 2.83v at 1 meter. That means it isn’t very efficient per wattage of energy. Paraphrasing ‘Hofmann’s Iron Law,’ a loudspeaker can have two of the following attributes but never all three: small size, deep bass, or high sensitivity. The OPAL1s would seem to be a great demonstration of that physics. It does remind me of the classic acoustic suspension designs from the late 50s through the 60s, from the likes of Acoustic Research and KLH (to learn about this era of loudspeaker: Sealed is Not Acoustic Suspension in Loudspeakers). However, those classic speakers had a much more limited dynamic range since they did not have anywhere near the power-handling or linear excursion that the OPAL1 possesses. Low sensitivity can be compensated for by higher power, and this is what the OPAL1 does since it is rated for 200 watts. But even that high power handling only takes it so far, and the chances of its low sensitivity becoming problematic are situational. If you are trying to achieve high SPLs in a large room, obviously these are not the best candidates. On the other hand, if you are looking for a pair of bookshelf speakers for a desktop system or small bedroom, these should suffice nicely.

Let’s now see how this design adds up in practice by doing some real-world listening…

Listening Sessions

In my 24’ by 13’ (approximately) listening room, I set up the speakers with a few feet of stand-off distances between the back wall and sidewall and an equal distance between the speakers and the listening position. I angled the speakers to face the listening position. The listening distance from the speakers was about 9 feet. No room correction equalization was used. Processing was done by a Marantz 7705 and the amplification was done by a Monoprice Monolith 5x200 amplifier. No subwoofers were used.

Music Listening

With the OPAL1s in-house, I allowed my exploration of the music of Ralph Vaughan Williams to continue with “Vaughan Williams: Retrospect,” an album of performances that sample his shorter works. I am not the only one currently digging Vaughan Williams since this album turned out to be a bestseller in the classical category. This music is performed by the London Choral Sinfonia under the direction of Michael Waldron. This 2024 release from the Orchid Classics label has terrific production and is surely in the running for a Grammy production award. I streamed this album in a 192kHz/24-bit resolution from Qobuz.

The first quality I noted was the enveloping soundstage projected by the OPAL1s. The album was recorded in a good-sized church (St. Jude’s Church, Hampstead Garden Suburb, England), and the sound mix placed the listener in a center middle seating position, so the environmental acoustics were certainly an element in the recording, but not enough to wash away any well-defined imaging. Lead instruments had a clear sense of placement while instrumental sections occupied large swaths of the soundstage. The OPAL1s managed to convey the scope and depth of the orchestra despite the speakers’ modest size. The speakers resolved the choral sections nicely, and the London Choral Sinfonia sounded gorgeous. A pipe organ joins in for track 13, “Nothing is Here for Tears,” it sounded impressively full on the OPAL1s. It was a marvel to hear how such small speakers can reproduce the sound of a full orchestra plus a large choir and a pipe organ on top of everything. I enjoyed listening to “Vaughan Williams: Retrospect” on the OPAL1s, and if you need to get a big sound out of a small package, these are well worth consideration.

For an album that places a human voice in the fore, I listened to Maria Kim’s “With Strings: Dreams of You,” a laid-back jazz album centered around Kim’s mellow singing. She is backed by a jazz quartet with a string chamber orchestra, and she performs covers of some traditional staples by Gershwin, Schwartz, and Cole Porter, among others. This album doesn’t break any new musical ground, but it is masterfully performed and recorded. These renditions can’t be faulted for execution, even if they are perhaps lacking in originality. If you want a straightforward vocal jazz record that covers some golden-age classics, this is the one to get. I streamed this 2021 release from Qobuz in a 96kHz/24-bit resolution.  

The first track, “Dream of You,” has a simple opening with Kim singing over a double bass. Kim’s voice imaged terrifically in the center of the soundstage, with the double bass recessed behind her. The double bass was given a full sound, and it’s always a neat trick to hear such a large instrument fully reproduced by such small speakers. On subsequent tracks, the string orchestra accompanying Kim had a wide staging that the OPAL1s projected outside the breadth of their placement, yet Kim’s voice was always dead center. The piano could be heard to be mixed to have a right-of-center placement − not the typical placement for that instrument but probably a result of trying to capture Kim’s voice along with her piano playing all with a single microphone. Kim’s mellow voice was beautifully articulated by the speakers, which gave her a lifelike presentation. All instruments were nicely rendered by the OPAL1s, although Kim’s voice was emphasized most in the mix. Jazz doesn’t get much classier than “With Strings: Dreams of You,” and the OPAL1s made it a truly enjoyable listen. Audiophiles should check this album out, and they will be lucky if their megabuck system sounds as good as these diminutive and affordable speakers.

Taking a 180-degree turn away from the acoustic simplicity of the music I had been listening to heretofore, I threw on Creme Rinse’s “Numbers,” a 2021 compilation of some of this unusual artist’s past work. It’s difficult to classify Cream Rinse’s work, except to say that it comprises idiosyncratic studio creations that occupy a space somewhere between sound collages, vaporwave, and electronic dance music. The bizarre soundstages and innovative sampling make Cream Rinse’s music a pleasure to listen on a capable sound system, at least for those looking for something that explores new sounds and isn’t tethered to formal music conventions.  

Many of these tracks sound almost like diegetic music being played in a variety of oppressive environments that contrast with the mood of the music. The OPAL1s enveloped me in Cream Rinse’s aural atmospheres while placing the musical heart of the tracks in the foreground. Many of the foreground tracks were sampled or remixed pop music, such as “Major Tom (Coming Home)” by Peter Schilling or “Eyes Without a Face” by Billy Idol, but Cream Rinse turns these familiar hits on their heads by breaking them into pieces, rearranging the fragments, and then distorting them. The OPAL1s wide soundstage and precise imaging made these psychedelic interpretations fun to hear. Voices could drift off into a reverberant void and then blaze across the soundstage like a deity issuing commandments from on high. The overall experience was rather cinematic, especially since there were so many layers in this soundscape. The OPAL1s kept these layers of sound distinct, so even though this music could be busy at times, it was never confusing or unclear. Many of the sound effects employed by Cream Rinse dug pretty deep in bass, and the low-frequency extension produced by the OPAL1s was mind-boggling. It sounded like subwoofers were in use. I have had plenty of tower speakers that didn’t dig as low! Of course, at the same point on the volume dial, those towers would have been deafening, but the OPAL1s still put out a strong sound. My guess is that most users who listen to this album will do so on headphones, but those with a good sound system and listening room ought to give it a chance. If their system includes speakers as good as the OPAL1s, I am sure they will have a blast.

For something that could find out what it takes to audibly stress the OPAL1s, I played an album entitled “Hellion” by Alex Perez and Headland. It is electronic bass music that lies somewhere between downtempo and dubstep, and it has an extra helping of bass. At high enough drive levels, it would easily push woofers into severe distortion. It’s a strange conceptual album that is fun because of its twisted atmosphere, inventive use of bass, and stark sound design.   

After a trippy intro track, the bass kicks in in earnest on track 2, and the OPAL1s put out a tremendous bass sound reminiscent of a subwoofer. Kick drums had a nice thump, and basslines had a palpable growl. I could see a fair amount of movement from the bass driver’s cone, but I knew it had more to give. Normally, when you can see the woofer visibly move on a bookshelf speaker, that driver is likely at its limits of linear playback, but with a 14mm Xmax, the OPAL1 woofer has more than an inch of total throw, so it is comfortable with a level of movement very few other midrange drivers would handle. These speakers could get loud as well, but given their sensitivity, they do need sufficient wattage to achieve high volumes. Low sensitivity doesn’t necessarily mean the inability to get loud, so long as the speaker can handle lots of power. Luckily, my 200 watts @ 8 ohm amplifier could meet the upper limits of the OPAL1’s power handling spec, and they could get louder than I could listen to for a prolonged period. They do have their limits, as I found out in brief moments of cranking the volume very high, making the woofer audibly complain. But these limits occur at ridiculously loud levels, at which no one should expect a small bookshelf speaker to have undistorted sound. “Hellion” sounded better on the OPAL1s than anyone would ever expect from a pair of bookshelf speakers of their size. Anyone looking for a pair of stand-mount speakers with real bass has a serious contender here.

Movie Watching

An action movie that has attained some acclaim is “Sisu,” a 2022 Finnish action film set in WWII. This movie concerns an ex-soldier who discovers a gold vein in the Finnish countryside. He mines as much as he can and sets off to deposit it at the nearest bank which is over 500 miles away. Unfortunately, a group of Nazi soldiers discover the nature of his haul and set out to kill him and take the gold. However, he turns out to be much more proficient at waging war than they realize. I hadn’t yet seen “Sisu,” but the trailers made it look almost like a western, and the word of mouth was that it had some pretty brutal action scenes. I figured it would be a good opportunity to see what the OPAL1 speakers could do with an action movie sound mix.  

“Sisu” turned out to be a lot more absurd than I anticipated, but I enjoyed it nonetheless, and it helped that I had such a capable sound system to experience it with. We get a taste of the OPAL1’s low-frequency prowess early on as a fleet of German bombers fly overhead menacingly, and the roar of their collective engines filled my room with an impressive rumble. Later on, our hero gets targeted by a tank, and the cannon blasts thundered with a resounding boom which was potently rendered by the speakers. The Nazis attempt to kill the protagonist with a variety of firearms, and these curiously ineffective weapons cracked and popped energetically on the OPAL1s. The main character mostly did not use firearms and seemed to prefer melee forms of combat, and the various stabbings and bone-breaking sounds were reproduced with a sickening level of audible detail. The over-the-top finale on the crashing plane bellowed in my room; it was an over-the-top but fun sequence that was reproduced with verve by the speakers. Dialogue intelligibility was always very good where the spoken language was English (I couldn’t evaluate the few instances of spoken Finnish as my own Finnish is a bit rusty). The music score by Juri Seppa and Tuomas Wainola was a terrific homage to Ennio Morricone’s scores for Sergio Leone, and it sounded terrific and full-bodied on the OPAL1s. Anyone interested in a berserk and bloody action movie would be doing themselves a favor by checking out “Sisu,” and it helps the experience to view it with such effective loudspeakers as the OPAL1s. 

A movie that looked to have an exciting sound mix was “Ferrari,” the 2023 Micheal Mann film about the difficult period in Enzo Ferrari’s life that led up to his participation in the 1957 Mille Miglia endurance race. Mann’s films have always been stylish and technical masterpieces, so a movie about automotive racing looked like a great fit for him, especially in such an important era for such a prestigious manufacturer. This movie promised a top-notch sound mix, especially given the director and subject matter of automotive racing. I was looking forward to seeing what the OPAL1s could do for the racing scenes in “Ferrari.”

I liked “Ferrari,” and it was nice to see that Hollywood can still produce movies for adults once in a while. The OPAL1s provided a shockingly muscular sound for the movies’ racing scenes. While the movie has an impressive cast with stars such as Adam Driver and Penelope Cruz, for many viewers the cars are the real stars, such as the Ferrari 335 S, Ferrari 250 TdF, and Maserati 450S. The OPAL1s gave their twelve-and eight-cylinder engines a guttural roar. Tires sharply screeched on pavement for hard braking, and the occasional crash was given a violent shearing effect as the cars tore through barriers. The OPAL1s continuously impressed me as small speakers that could recreate a big-screen sound. I had the speakers playing at a healthy output level and never sensed that I was hitting their limits. The orchestral score by Daniel Pemberton was also nicely reproduced, and it added to the tension of the race scenes while heightening the emotion of the more intimate personal drama. Dialogue intelligibility was always good, and I could understand the characters’ speech even as most of the cast spoke with a thick Italian accent. It’s unfortunate that “Ferrari” wasn’t a big hit at the box office, since there are doubtlessly many more great stories from the history of automotive racing that would be a great fit for the silver screen. At least we got this movie, and it was a well-made and enjoyable one that should be seen with a decent sound system for maximum effect.

Dayton Audio OPAL1 Bookshelf Loudspeaker Measurements

The Dayton OPAL1 speakers were measured in free air at a height of 7.5 feet at a 1-meter distance from the microphone, and the measurements were gated at an 11-millisecond delay. In this time window, some resolution is lost below 250 Hz and accuracy is completely lost below 110 Hz. Measurements have been smoothed at a 1/24 octave resolution. 

The above graph shows the direct-axis frequency response and other curves that describe the OPAL1’s amplitude response in a number of ways. For more information about the meaning of these curves, please refer to our article Understanding Loudspeaker Measurements Part 1. At a glance, these measurements would indicate a rather nonlinear loudspeaker. However, ground plane measurements do counteract some of the would-be irregularities depicted here, so the OPAL1s aren’t likely to yield an in-room response as peculiar as would be expected from this graph. The areas of interest are a wide Q elevation centered just above 1kHz and a dip centered around 3kHz. Typically, a sound system with an elevation around 1kHz would sound ‘shouty’ or ‘chesty,’ but I didn’t hear much of that in my own listening, and it was only when I A/B compared the OPAL1s against my extremely neutral 1802G reference speakers that I got a sense of any of that at all. In later listening on reference tracks, I thought I might have heard a slight dearth of upper bass, but it was mild at worst. In-room measurements seemed to pan out that perception. As for the dip around the crossover frequency, the sound didn’t seem to be missing anything in that range, even when comparing the OPAL1s to my neutral reference speakers. The in-room frequency response didn’t exhibit any comparably major dips in that region either, likely because it is more a phenomenon of the on-axis response than off-axis responses. A mere glance at the OPAL1 “spin-o-rama” curves would likely be misleading as to the tonal sense that these speakers impart in real-world listening. If I had judged it only from this graph, I would not have guessed that I would like the OPAL1 as much as I did.

The above graphs depict the speaker’s lateral responses out to 90 degrees in five-degree increments. More information about how to interpret these graphs can be read in this article: Understanding Loudspeaker Review Measurements Part II. In these graphs, we get a better look at how the on-axis response and nearby angles compare to the off-axis responses. One interesting aspect that the above curves reveal about the OPAL1s is that the crossover dip is more of an artifact of the on-axis response than off-axis. The directivity matching between the tweeter and woofer looks very good overall, and it may be that incurring an on-axis notch was the penalty for that. I would say that is a wise decision because my in-room measurements showed there was little evidence of a dent at the crossover frequency. This family of curves has good correspondence to each other in general, so those who want to use equalization to adjust these speakers to taste should be able to do that fairly easily.  

The above polar map graphs show the same information that the preceding graphs do, but they depict it in a way that can offer new insight regarding these speakers’ behavior. Instead of using individual raised lines to illustrate amplitude, these polar maps use color to portray amplitude, and this allows the use of a purely angle/frequency axis perspective. The advantage of these graphs is that they can let us see broader trends in the speaker’s behavior more easily. For more information about the meaning of these graphs, we again refer the reader to Understanding Loudspeaker Review Measurements Part II.

Given the design of the OPAL1, we would expect a wider dispersion loudspeaker, and that is what we see here. Smaller diameter woofers and domes unconstricted by waveguides will put out acoustic energy at a wider angle, and we get a fair amount of output out to 70 degrees before the tweeter begins narrowing its directivity. The upper-treble contraction of energy from the tweeter is also something very characteristic of domes mounted on flat baffles with no waveguides. Those who want to be hit with upper treble should aim the speakers directly at the listening position. Those who want a softer sound can simply toe the speakers inward less. Very high treble notwithstanding, these speakers aren’t that fussy with angling and should have a similar sound over a wide area. 

The above graph shows the OPAL1’s response behavior along its vertical axis where zero degrees is directly in front of the tweeter, negative degree values are below the tweeter, and positive degree values are above the tweeter. As with most loudspeakers, the OPAL1 is best listened to on-axis, so try to get it placed with the ear about level with the tweeter. The user does have a bit of vertical room before crossover nulls start to take a bite out of the lower treble, about +/- 10 degrees. Above or below a 10-degree angle, the response becomes a bit rougher as the tweeter and woofer start fighting over their shared bandwidths since their distance difference begins creating phase conflicts.

The above graphs show the OPAL1’s low-frequency responses that I captured using groundplane measurements (where the speaker and microphone are on the ground in a wide-open area). We have done something a bit different from the usual in increasing the shown bandwidth out to 1.5kHz in order to show the difference between this groundplane measurement and the free-air measurements shown in previous graphs. The reader might ask which is correct since they are showing significant differences, and the answer is both are correct. The acoustic circumstances are creating a difference where upper bass is transitioning to midrange; in the free-air graphs, the midrange becomes elevated, but in our groundplane graphs, we see a pretty steady flat response from 60Hz all the way up to nearly 1.5kHz. Both measurement techniques are anechoic in the sense that there are no acoustic reflections being picked up by the microphone, but the groundplane measurement looks to be getting some boundary reinforcement that is filling in the upper bass gap seen in the free-air measurements.

So then the question becomes, which of these measurements will be more reflective of the speaker’s tonality in real world listening? The answer depends on the user’s acoustic environment, but the vast majority of typical listening situations will have a good deal of boundary reinforcement, especially as the speaker gets placed closer to backwalls or sidewalls. A small speaker like this is really meant for smaller room listening and so is much more likely to be placed near a surface than placed out in the middle of a room. My own in-room measurements resembled the groundplane measurement rather than the free-air measurements as far as the bass to midrange frequency band went. For this reason, I believe that the groundplane measurement is more indicative of the OPAL1’s tonality than the free-air measurement.

The above graph shows the electrical behavior of the OPAL1 speakers. One notable attribute we can see from the height disparity of the second peak in the lower frequencies is that the resonance of the bass driver is significantly lower than that of the enclosure. We can also see from the dip between the two peaks that the passive radiator tuning lies between 30 to 40Hz. Dayton Audio specifies this to be an 8-ohm nominal speaker, and I would say that while technically that is a stretch, in practice it is acceptable. The reason why it is a stretch is that most of the tweeter’s bandwidth is spent under 5 ohms, nearly bottoming out at 4 ohms at 5kHz. However, the tweeter doesn’t command a lot of power, so this shouldn’t be hard for any amp to run, especially since the electrical phase isn’t doing anything dramatic in that range. The bass driver, which can use a lot of power, has a fairly benign impedance load, staying at 8 ohms or above.

The impedance isn’t what makes the OPAL1 a difficult speaker to drive, but the sensitivity might, depending on the user’s SPL demands. I measured the OPAL1’s sensitivity to be 76dB for 1 meter at 2.83Vrms. That is very low, even lower than Dayton Audio’s specification of 78.5db for 2.83v at 1 meter, and by far the lowest I have encountered in a loudspeaker. So how bad is such a low sensitivity? It depends on your use case. If you intend to drive these speakers with a low-wattage amp, they will be very limited in output, but with a 200-watt power-handling spec, they can rock if you feed them adequate power. They will never be extreme SPL beasts, but they definitely have enough headroom for a bedroom or small to medium-sized living room for any reasonable output level. They can get loud, but they do need a real amplifier to achieve that loudness.

Dayton Audio OPAL1 Bookshelf Loudspeaker Conclusion

Before bringing this review to a close, I will briefly go over the strengths and weaknesses of the product under evaluation, and, as always, I will start with the weaknesses. The Dayton Audio OPAL1 isn’t perfect and does have its trade-offs that will make it a poor fit in certain circumstances. All loudspeaker engineering is a matter of trade-offs, and the OPAL1 is a good example of the compromise that must be made to get serious low-frequency extension out of a small enclosure: efficiency. The OPAL1 is very inefficient with power. Its extraordinary power-handling does make up for that quite a bit, but, of course, the cost of that is the need for a beefy amplifier. I would be looking to supply it with 100 watts/ch, or maybe 200 watts/ch if you want more punch. I wouldn’t give it a flimsy amp either, because it will probably be stressing the amp more strenuously than is realized. To give this some perspective, a typical tower speaker is about ten times more efficient, so you would be using a tenth of the power to achieve the same loudness level.  

One could complain about the decidedly nonlinear responses that were measured, but as was explained at length in the measurements analysis, the OPAL1’s in-room acoustical performance is likely to be smoother than what we see in an anechoic response measurement. The OPAL1s deserve more than a superficial analysis of measurements. This isn’t to say measurements aren’t indicative of how the speaker will sound, but rather that these need a deeper dive to get a full understanding of how they behave in real-world situations. Despite the erratic anechoic frequency responses, the OPAL1s sounded good and measured well in my room, even when compared to a nearly perfect reference speaker. That being said, they wouldn’t be my first choice for absolute accuracy. But it would be hasty to dismiss them as badly inaccurate from a glance at a few measurements.

Moving on to the OPAL1’s strengths, they sound terrific, and they have incredible bass for their size. I have had bookshelf speakers that had impressive low-frequency output for their size, but the OPAL1s are on another level with sub 30Hz extension in-room. There are plenty of tower speakers that do not dig as deep. If you are limited in space and want as much low-frequency extension as possible from a not-large bookshelf speaker, there really isn’t anything out there that can compete with these, regardless of price. Outside of their unreal bass extension, they image very well and project a nicely enveloping soundstage. While they do have a slightly elevated midrange, their tonality on the whole was good, and users are not likely to notice anything amiss unless they are carefully listening for a bit more forward midrange.

After their sound quality, I was also deeply impressed by their build quality. There aren’t many other bookshelf speakers in the same price range that have this level of solidity. The drivers are quite good for the price, especially the bass driver which has a sensational design and construction. The crossover circuit is pretty serious and probably pretty pricey to manufacture also. The OPAL1 has a true gloss finish that elevates the speaker to a luxury-class item despite its reasonable pricing. The packing was a cut above average as well. The OPAL1s look nice, and they feel substantial.

Thinking about competing loudspeakers, there isn’t anything quite like the OPAL1s, mainly on account of their unique trade of sensitivity for low-frequency extension. Some other speakers in their segment might be the Ascend Acoustic Sierra-1 V2s. I would expect them to have a more linear response and higher sensitivity, but their bass extension is nearly a whole octave short of the OPAL1s. Another competitor would be the Philharmonic Ceramic Mini Monitor. Like the Sierra-1 V2s, the Philharmonics are more linear and more sensitive than the OPAL1s, but do not dig nearly as deep. The same holds true for many of the other similarly-priced and similarly-sized stand-mount speakers. The OPAL1s are in a class of their own thanks to their extraordinary low-frequency extension.  

The Dayton Audio OPAL1s are the speakers to get if you want subwoofer-type performance without the subwoofer, from a modestly-sized pair of bookshelf speakers. Be prepared to feed them lots of power to get the most out of them. Those who do will be rewarded with an engaging and powerful sound. They are the perfect solution to getting a true full-range sound system in a tight space, such as a small bedroom or desktop system. At this point, I should repeat what I said before: I can’t think of any similarly-sized loudspeaker that can dig as deep at any price. In that light, their $800/pair pricing makes the OPAL1s a real bargain. I enjoyed my time with them, and I think that those who have a need for a loudspeaker like them will be delighted by their sound.

The Score Card

The scoring below is based on each piece of equipment doing the duty it is designed for. The numbers are weighed heavily with respect to the individual cost of each unit, thus giving a rating roughly equal to:

Performance × Price Factor/Value = Rating

Audioholics.com note: The ratings indicated below are based on subjective listening and objective testing of the product in question. The rating scale is based on performance/value ratio. If you notice better performing products in future reviews that have lower numbers in certain areas, be aware that the value factor is most likely the culprit. Other Audioholics reviewers may rate products solely based on performance, and each reviewer has his/her own system for ratings.

Audioholics Rating Scale

• — Excellent
• — Very Good
• — Good
• — Fair
• — Poor

Metric	Rating
Build Quality
Appearance
Treble Extension
Treble Smoothness
Midrange Accuracy
Bass Extension
Bass Accuracy
Imaging
Dynamic Range
Fit and Finish
Performance
Value