Initial impressions of Behringer DSP8024

I've added a DSP8024 digital EQ to my system to offset an annoying room resonance, and it seems to work pretty well. I picked it up on eBay with the matching calibrated microphone for $150. El cheapo cabling was another $70.

The system:
Martin Logan Aerius i speakers biwired & vertically biamped with a pair of Adcom GFA5200 50W/ch power amps driven by an Adcom GFP555 preamp. Front end is an HK8550 CD changer (to be replaced with a used Rega Planet 2000 when I can scrape together $500). For this beer-budget bargain-hunting audiophile, this system is a dream.

I've put the DSP8024 between the preamp's Normal outputs and the bass channels of the power amps, so any signal degradation is limited to the woofers. The panels are fed normally from the preamp's Lab (high-bandwidth) outputs. The panels really don't need any EQ. But, the woofers suffer from a significant room resonance at around 80Hz.

It took a couple hours of reading the manual and fiddling with all the buttons and menu items to figure out how to use the DSP8024. The manual's not all that helpful. So far, I've settled for leaving the graphic EQ flat and using two of the three parametric EQs available through the Feedback Destroyer function. I centered one para on 80HZ with a bandwidth of 1/3 octave and dialed it down -6db. Then, after seeing a trough around 40Hz on the analyzer (reading pink noise with the mic), I set a second para at 32Hz with bandwidth of 1/3 octave and dialed it up 3db.

Acoustic bass on Miles Davis' "Kind of Blue" is now a lot cleaner. The 80HZ emphasis on certain notes that was distracting me from the music is now gone. I'll do further tweaking after listening to a wider range of music. In particular, I'll probably boost the 25-40HZ region a bit more, as I know there's more energy there on "Kind of Blue" and the Aeriuses do reach comfortably down to 32Hz, but I'm not quite feeling it.

Purists will probably scoff, but this seems like a good solution to me. My speakers are four feet from the back wall and 18" from the side walls, so there's not a lot more I could do in terms of positioning to mitigate the room resonance. I love what the panels do, but the mid-bass boom was making them sound cheap. Now I can enjoy the flat, detailed midrange in peace.

If I discover anything else useful, I'll post again, in case anyone else is struggling with room resonance and considering EQ as a solution. I searched the forum for info on the Behringer digital EQs but didn't find much. So, here's my chance to offer some useful info to others on the forum.
Wow, best $150 I could have spent. After further tweaking, I've abandoned the PEQ for GEQ. The room resonance around 80Hz (+7.5db) is nicely corrected. And, I discovered that there was a huge suckout (-9.5db) at precisely 40Hz, probably due to the large open doorway in my living room's back wall. With that corrected, the Aeriuses now have proper slam on big kick drums on Manu Dibango's "Wakafrika". Acoustic bass on Miles Davis' "Kind of Blue" seems a little subdued, so further tweaking will follow. I had been thinking of adding a pair of Mission 700AS subs I've had kicking around, but now I can sell 'em. The Aeriuses really do go plenty deep all on their own, at least for this non-HT apartment-dwelling music lover. The 8024's RTA shows output down just -3db at 25Hz and -4.5db at 20Hz without correction.

I'm not sure I'd want to put the 8024 in the signal path to the Aerius' panels, but as a bass EQ in a biwire/biamp system, it's perfect.


Next: better cables and a Rega Planet 2000. But, first, a new Mac.
I actually had an order in for a DSP8024, but I changed it for a DEQ2496 which is a similar newer model. I have had great results with the DEQ2496, and I now have three of them to take care of five channels. Room EQ is the way to go, and Behringer makes it affordable.
I tried putting it in a tape loop to EQ the whole range rather than just the bass. Makes a nice difference. Now I know what another poster meant when he called the Aeriuses "warm". They are warm. I just hadn't noticed, because my previous speakers were Spica TC-60s, which also are warm. With just a bit of very gentle EQ (via Auto-Q) tipping up the upper midrange and treble, vocals opened right up. Makes sense, since the frequency response plot for the Aeriuses as reported by Stereophile sloped gently downward from the midrange to about -2db in the treble. In my room, there's also a small hump around 400Hz and a small dip around 800Hz, which combined to give male vocals a warm sound. About 2db of correction smoothed it right out, and voices are now more natural and present.

Overall, I'm very, very pleased with the effect of this EQ. The Behringer unit is extremely flexible, and the ability to adjust 1/3 octaves by as little as 0.5db enables extremely fine control. I'm a bit leery about possible signal degradation, though I haven't noticed any, so I haven't quite decided yet whether to leave the 8024 in the main signal path or put it back on the woofer channels only. I'm waiting to have an audiophile pal come over so we can switch the tape loop in and out to compare the pure signal with one passed through the EQ set at flat. Will report my findings. I know the 2496 offers higher-rez sampling, but I've got my fingers crossed for the 8024. At least I know the concept works well. If the 8024 disappoints, I might sell it and try a 2496. For now, I'm very pleased. At $150 with mic, it's a steal, especially when you consider that Audiocontrol C-101s go for $300+ on eBay.
Am now using the DSP8024 as a DAC between my HK8550 CD changer and my Adcom GFP-555 preamp, which limits D/A conversion to just one step instead of three. Sounds great. As a DAC, it doesn't seem to be any worse than that built into the HK. Haven't yet had a chance to do an instantaneous A-B comparison with the unit switched in and out of the signal path and EQ turned off. Based on my one-person A-B comparison (listen, get up, switch, sit down, listen), I'm very happy with the DAC's performance. And, the EQ has made such a noticeable improvement in neutrality and imaging that it's painful to switch it out. BTW, there is absolutely no noise or hum in my system, with or without the Behringer.