I’ve been into audio gear since I was a kid. My first “real” system was a Kenwood receiver and a pair of floorstanding Technics 3-way speakers with 15 inch woofers. (Ah, the memories of cranking them up and trying to hear them at the street.) Then I had a pair of DCMs, and then tried bookshelf speakers with a subwoofer.

I fell out of the game for awhile in my early twenties and didn’t get truly back into it until a year ago.

I’d had a general understanding of how everything worked, what ports were about, etc., but recent experiences showed me just how much more there was to it all.

Earlier this year I got my hands on the Dayton Audio Ultimax 15″ (UM15-22) and it was a game-changer in how I thought about subwoofers, even as a long time basshead. In particular, it seemed to answer questions I’d had such as:

  • How big of a difference does a well-braced, well-built box make?
  • Do bigger cones hit lower notes more easily?
  • Why do people favor heavier cones with lower sensitivity ratings (that require more power) over lighter cones that need less power to hit target dB levels?
  • Just how much of music falls below 80hz anyway? Is bass that important? (Not a question I was asking, but didn’t know an ideal answer for when people asked me that.)

I’ll talk about each of these one at a time.

The difference a good subwoofer box makes.

I admit that in the past I’d always viewed the box as an afterthought. I figured it was simply to house the speaker, to separate the forward and backward motion from cancelling each other out (the way woofers do in free air).

I was wrong.

At one point reading up in various forums I noticed a bunch of people were making the point that actually probably 60% of what you hear in a subwoofer is the box, and when you’re looking to make an upgrade — especially if you have a cheap box — you’ll get a bigger bang for your buck getting a better box rather than a better subwoofer.

Over the years I’ve used various big box store subwoofers in the house and car, and never gave much thought to the boxes that were (in retrospect) too small and too weakly constructed. These things were taking away more of the experience than I’d realized.

The Ultimax 15 came with a Denovo flatpack, which is a nicely pre-machined set of heavy MDF panels that fit neatly together. With some good wood glue, you can assemble this box in under an hour. Most of the time is in waiting for it to dry with clamps on it. (About a day.)

This box ends up being nice and heavy, and very well braced internally. Certain frequencies that created unpleasant rattles in the room were suddenly gone with a stouter box.

And more importantly, I immediately noticed how much deeper it played than any of the subwoofers I’d been using.

The box volume is also super important. You have to let the subwoofer breathe, or else you’ll stifle its range. I learned this the hard way by bringing car subwoofers into the house and trying to amp them. It worked and sounded better than not having them, but the small boxes common for car subs are relying on what enthusiasts call “trunk gain”.

This refers to the innate boost the small space of your trunk and car cabin give to low frequencies (+6-12dB), which allows a subwoofer to sound awesome in your trunk. But without that trunk gain, that same box will sound anemic in your house with much more open spaces.

Especially at frequencies below 40hz.

A simple piece of advice if you’re ever thinking of building a new box for a car subwoofer to use in your house: start by at least doubling whatever the cubic airspace of the car box was. Yes, you will need to increase it that much.

Often sealed boxes for 12″ woofers are 1 to 1.25 cubic feet, for instance. As a start, you could double that to 2 to 2.5 cubic feet and you’d notice a significantly fuller low end. This is all the more true if you go ported, since in general ported boxes need to be larger than sealed boxes.

(Largely because of air pressure around the port and difficulty hitting lower tuning frequencies.)

The Denovo flatpack that came with the Ultmax 15 is 3 cubic feet for a 15″ sub, but I’ve seen a lot of talk from people saying the Ultimax sounds even better in a 5 cubic foot box.

Advantages of bigger (and heavier) subwoofer cones.

While there are always exceptions to any generalization one could make, e.g. a small subwoofer that can hit surprisingly low, my experience has been that it does seem that larger cones reproduce lower frequencies more effectively.

Look at the specs on any product line (for internal consistency) and you’ll usually notice the smaller cones have a higher f3 rating (the frequency at which the response curve starts trailing off 3dB) than the larger ones. That means that the smaller subwoofers reach a point where they can’t create bass with as much presence at an earlier point on the downward frequency curve.

My anecdotal experience thus far has been consistent with that, and I’ll discuss it.

But even more than that, the cone’s heaviness and material makes a difference.

Years ago when polypropylene cones were having their heyday there was a big fuss about the advantages of lighter cones being easier to drive, and more accurate. (My first car sub way back was a Sony Xplode in red polypropylene.)

The problem with thin plastic is that it isn’t very rigid. When the cone is moving at the intensity low frequencies demand, thinner cones can flex unevenly throughout their motion and create distortion. Or simply not create the same sense of bass impact.

This is why some subs with higher sensitivity ratings (90dB and up) don’t necessarily sound better in real life applications. They more efficiently produce sound in general, but can be less impactful for the things a subwoofer is for.

A heavy speaker like the Ultimax 15 carries a sensitivity rating of 86dB, which at a glance might deter you after you’ve seen other subs at 90-91dB.

After all, since every 3dB increase requires a doubling of amp power, that theoretically means the Ultimax requires twice the power of an 89dB sensitivity speaker to hit the same perceived volume, right?

But the extra cone mass, while potentially a little harder to drive, also resists flexing far more under stress and also creates a greater perceived sense of impact on hard bass hits. This is where the Ultimax excels.

I think the key that separates this truth from older, conventional wisdom about big, heavy cones sounding muddy or sloppy is that you need to have a sufficient magnet. When the magnet is too small or weak to control the heavy cone, it sure does sound muddy and anemic.

Many woofers years back were created with undersized magnets, usually because manufacturers would use the same magnet for their entire woofer line, from 8 inch or 10inch woofers all the way up to 15 and 18 inch woofers. It was a cost-saving decision that seems to have given larger woofers a bad reputation.

But one look at the magnet on the Ultimax will assure you that’s not the case here.

Dayton Audio Ultimax 15 side view with large magnet

I’ve always found that despite having a big 15″ cone the Ultimax sounds clean, even when driven hard.

Also, I have to second a thought I’ve seen made in numerous audio forums about this concept: These days power amps are so cheap that higher power demands are easily met. For instance, the capable Rockville RPA12 goes for $250 and will net you 1400W RMS bridged, or the well-known Crown XLS series start at $350, and start at 1100W RMS bridged.

Subsequent DIY subwoofer boxes I’ve made have made the other woofers sound much better.

Porting 10″ and 12″ subwoofers for the 28hz range made a big difference. The played louder and with more impact, and they hit much deeper.

What surprised me a bit, though, was in A/B tests they still didn’t outperform the Ultimax 15 in a sealed box. (I’m sure there are some that can; I’m just saying that thus far in 3 other subwoofers I’ve played with it hasn’t been the case.)

Sure, the ports really brought out the low end and helped the smaller subwoofers create a presence, but the Ultimax still had more of a wall-rattling, hit-you-in-the-chest impact that the others didn’t.

Maybe you can chalk that up to the Ultimax’s build quality etc., but I tend to think it’s a mixture of the solid box it came with and its sheer amount of air it can move with its mighty cone.

When I’ve watched movies with loud effects and bassy gunfire or explosions, the smaller subs made the movie more fun, for sure. But the Ultimax transformed the experience into a “feel like you’re there” sensation, especially on those really deep frequencies that are just barely within the range our ears can still hear.

But how much of a difference does a subwoofer really make for music, anyway?

In my experience, a lot. You don’t have to be a basshead to appreciate the difference.

Unless you have large floor standing speakers that respond low, very likely you’re not hearing the full frequency range. It’s underrepresented.

If you’re used to the way your speakers sound you may not notice anything missing, and their limitations not something that drew any attention. Once you’ve heard an audition with a clean but capable subwoofer you’ll likely realize you’ve missed the prevalence of half of what the drummer is doing and most of what the bass guitarist is doing in your music.

You could hear those instruments, but they probably didn’t stand out and instead became kind of background for the guitars, vocals, and other instruments.

Even if you have big floor standing speakers, typically the woofers in them only respond well down to about 40hz. You’d be surprised what even another 10-15hz deeper than that does for movies (and even an increasing number of modern pop, electronic, and rap songs).

And like I was mentioning above about the Ultimax’s ability to create chest-thumping impact, certain live music like Pink Floyd and the kick drums in the Eagles live album Hell Freezes Over feel authentic and just… present. It changes the presentation of the music.

My Klipsch RB62 bookshelf speakers claim they respond down to 40hz and are even ported, for instance. They don’t sound as anemic as little satellite speakers usually do, but they certainly lack any kind of bass impact in an open room.

My system benefited greatly from the addition of all of the subwoofers I’ve used, and that was true even when I fiddled with undersized car subwoofer boxes inside. It got a lot better with custom boxes that were larger, thicker, and ported. And got better still with the Ultimax.

I know I’ve been laying the praise on hard with this subwoofer and it’s not perfect. There are certainly others out there that can play louder and deeper — particularly the higher end models of SVS. But for a DIY-type setup at a more accessible budget, it’s a monster.

Why you should use a powerful amp.

My first real subwoofer was a Klipsch with about 350W RMS many years ago. Before the Ultimax, I’d been using other 10’s and 12’s with different amp configurations, usually 100W to 350W again.

When I stepped up the power to 700W and then 1100W RMS I started getting that impact that just wasn’t happening before. I’ll make the point that I’m not saying one needs 1000W to create good bass.

From what I’ve observed, think of it like this:

When you’re running your amp at safe gain levels you’re probably using 50% or less of your amp’s power at any time. Often far less. Those peaks will jump up much higher than average levels, but ideally they don’t go above what your amp says it can produce RMS. (Speakers can realistically play at their advertised peak levels, but to stay clean amps should really only be played at their stated RMS levels.)

The advantage of using, say, a 1000W amp isn’t that you need all 1000 watts. It’s that it gives the quieter sounds more presence, and gives those peaks a hell of a lot more room to breathe. They can jump up 10dB higher than other sounds as they often do, requiring 8-10x the power of other sounds, and with that amp headroom you’ll still be well below RMS limits.

Those peaks might hit 300W or 600W and sound great, even if the majority of the sounds use less power.

With a 350W amp those same peaks might only be hitting at 150-250W unless you’re driving the amp hard, because again, with proper gain levels you’d have to turn the source volume up pretty loud to be using all of the subwoofer amp’s power. So you might think that 300-500W is plenty of power, but the only way to reliably play at those wattages without straining your amp and potentially clipping the speakers is to have higher power reserves.

That’s part of what gives the low end of music so much more presence, because you don’t have to turn your main receiver up as loud for the sub’s amp to get it moving. Treble requires very little power to sound loud (and sound good). With ample bass power music sounds more balanced/even.