Thinking about picking up a pair of used Deftech A90s
I've been running these in my spare setup for about four years now, and they're one of those speakers that quietly do everything right without making a fuss. If you're looking at Definitive Technology A90 For Sale listings, here's what actually matters before you pull the trigger. The A90 is a 2-way bookshelf with a 1" Synex domain tweeter and dual 6.5" polypropylene bass drivers. Rated at 150 watts RMS, 8 ohms nominal impedance, and a frequency response that runs from 48Hz to 35kHz. They aren't going to rattle your fillings with bass extension, but in a properly set up room they sit comfortably in the midrange and highs without ever feeling strained. The build is decent — MDF cabinet, solid binding posts, no cheap-feeling grill material. I picked up mine off a guy in Portland who was upgrading to towers. Paid about $180 for the pair in case that helps calibrate what fair pricing looks like on the used market right now.
How they actually sound in a real room
These lean slightly warm. Not in a muddy way, just... relaxed above 3kHz. That Synex tweeter is well-damped and it doesn't spike like some budget domes do. Pair them with a bright amp and they smooth out nicely. Pair them with something already dark and they start to lose their sparkle. I run mine through a Parasound Halo A23 and it's a clean match — the amp gives them enough current without coloring the output. One thing nobody mentions: the dual 6.5" bass drivers in this size enclosure mean there's a port tuning around 42Hz. Below that, output rolls off fairly steeply. If you watch a lot of action movies and expect sub-bass impact, you'll need a sub. A modest one — even a 10" in a sealed box will cover the gap without fighting the A90s for the same frequency range.
The thing I ran into
About two years in, I noticed the left speaker's tweeter had a slight ringing on certain high-frequency material. Specifically, I was testing with acoustic guitar recordings at moderate volume and there was this metallic whisper around 8-10kHz that wasn't on every track. I tore the grill off, removed the driver from the baffle, and found a small hairline crack running from the surround into the foam ring. The speaker had been bumped at some point during previous ownership and the damage wasn't visible from the outside. Replacement tweeter from Definitive's parts department ran about $45 shipped. Took about ten minutes to swap it out — four screws, disconnect the wire, reverse. Speaker sounds stock again. If you're buying used and something sounds odd on a specific recording, check the drivers before writing them off.
Get the Full Details
What to check before you buy
Walk into a used speaker purchase with a short list. Test each driver by playing something with a steady low tone near 100Hz and watching the cone movement. Both 6.5" drivers should move evenly. If one is slack or rubbing, the voice coil is damaged. Check the terminals — loose binding posts that don't grip wire tightly will cause channel imbalance over time. Look at the surrounds on both bass drivers for any dry rot or separation from the frame. This is less common on newer models but still happens on units pushed hard for years. Also ask how they were stored. I've seen pairs that sat in unheated garages through a humid summer. The foam on these surrounds degrades with heat cycling. A quick visual inspection under a bright light will tell you if the foam is crumbling or discolored.
Running them as surrounds
One setup where the A90s really earn their keep is as rear surrounds in a 5.1 or 7.1 configuration. The dispersion is wide enough that you get even coverage across a typical living room seating area, and the power handling means you can drive them from the same amp channel as your main speakers without worrying about overheating. I ran them as surrounds for three years before switching to dedicated surrounds and honestly missed them when I swapped. The imaging on ambient tracks and film atmospheres was better than most purpose-built surround speakers at this price point. They're not for everyone. If you have a large open room — anything over 400 square feet — you'll be pushing these too hard and they'll distort before they get loud enough. They also struggle with low-volume listening in a treated space because the drivers need a certain amount of excursion to produce coherent bass. If you mostly listen at conversational levels with a sub, there's not enough energy in the lower mids to make them sound full. For that use case, something like a KEF Q150 or a SVS Prime Bookshelf would be a better fit. Tighter bass, more extension, better suited to small-room quiet listening. The A90s need room and volume to shine.
Getting a deal
If you're hunting for Definitive Technology A90 For Sale options, check local listings more than auction sites. The shipping cost on bookshelf speakers is brutal relative to their value. A pair listed for $150 on a marketplace might cost $80 to ship, while someone selling locally for $120 saves you real money. Also, these were common enough that older listings on forums occasionally pop up when people upgrade. The speaker communities on Audio Circle and Head-Fi have a used section that moves slower than eBay but has better vetting on seller reputation. The A90s aren't going to turn heads at a listening party. They'll just make the system sound more complete than its price tag suggests, which is usually the better outcome anyway.
