 Goed low frequency reproduction in de leven of listening room is niet makkelijk, maar er zijn verschillende manieren om low's te proberen, in de eind een base step moet worden nodig om een true, tight base te ontdekken. Maar deze balkie contraptie neemt ruimte van het Aesthetische Commissie. Tot nu toe is dat. Sinds low frequencies ontvangen veel meer energie dan midden en hoge frequencies en sinds de wavelengingen zijn in de regionen van de ruimte dimensie, er gebeuren verschillende problemen. Daardoor is de luidspeaker plaatsen van paramount importance. Do not think you can calculate the correct position for loudspeakers unless you use a model that includes all properties of your furniture, walls, curtains, and so on. En zelfs professioneel accusations lean on experience more than on modeling. Dat is waarom ik mijn twee-step approach op de luidspeaker plaatsen vond. Zie mijn video 001 Loudspeaker Placement Long Version. In dat video ga je leren hoe je luidspeakers plaatsen in twee stappen. First find the best position for low frequency reproduction and then locate and treat the early reflections for the mids and the highs that have great influence on the stereo image and tonal balance. Only when the best position has been established, further measures can be taken to improve lows. Loudspeaker cabinets have mechanical vibrations, despite what manufacturers say. These vibrations will also potentially set a wooden floor in motion, even if it is a thin layer of wood over a concrete floor like I have. The motions are minute but over a larger part of the floor and do have influence on the sound quality. Spring en damper feet can isolate the speaker from the floor if they are correctly designed for the weight of the speaker. But they allow for movement of the speaker, which will influence tensions and stereo image. They do give better lows though. A more all-round solution are feet that absorb the vibrations while having a firm contact between the speaker and the floor, like the stack audio overs I use in all three of my setups. But there is room for further improvement. In my listening room in the attic, where my setup 2 and 3 are located, there is a small loft over half the depth of the room. That is where I store the empty boxes of my equipment. This function is a large bass trap. Against the left and right wall, on the level the speakers are positioned, are IKEA, Kalex shelving units holding vinyl records, CDs, DVDs and Blu-rays. These form a proper mix between absorption and scattering of the mids and highs. Furthermore monitor speakers onstands with overfeet I use here, while a small rail subwoofer takes care of the rear lows. That could be placed at the best spot for the lows. And given the equipment used, the expectations are lower than for my setup 1. Watch my video about my reference setups made 2023 for more information on my three setups. Setup 1 is situated in the living room, where some limitations are imposed by the aesthetics committee. By carefully applying my two-step approach, the isolator feed, high quality equipment and a bit of lock, I managed to get rather good results. Only the deep lows show some room resonances that muddy the sound to some degree. Here no feed with empty boxes and separate sub, while the PMCs just as well go down to 26 Hz. The answer here would be to build a wideband bass trap. Exactly tuned bass traps are no solution since they would take far too much space. But even a wideband bass trap was too much for the aesthetics committee, understandably so by the way. Then I came across the PSI Ava C214 active bass trap. De PSI Ava C214 is cylinder shaped, measuring 210 mm in diameter en 640 mm high. It weighs 11.1 kilos and stands on rubber feet. The front has a mesh grill. The sides are closed and on the rear there is a recessed panel with mounted against it, a small box that on top holds two buttons that are normally used for gain plus and minus but have double functions in combination with the power switch. That is situated on the bottom of that box where also the IEC mains inlet is situated. The principle of this bass trap is simple. A microphone measures the air pressure variations between 15 and 160 Hz in front of the Ava. When room resonances appear in that spectrum the two 14 cm drivers in the Ava move in a way that these pressure increments are reduced, like if the wall locally moves backwards. Although this sounds like a simple technique, it is quite a feat and the two switch universities have been directly or indirectly involved. Imagine the spectrum from 15 to 160 Hz has to be monitored and while a resonance-like behavior occurs it has to be counteracted against. Luckily resonances take a short while to build up and react on a stimulus, a bass tone, in the music. But still it's a kind of magic to me. PSI emphasis that it doesn't work with anti-sound, sound with the opposed polarity. The original sound is not affected. It rather is a black hole for excessive pressure. PSI states the following on their website. By lowering the acoustic impedance of the air in front of it, the Ava effectively sucks in low frequencies over an area of about 1 to 1.5 meters. As a result, the optimal position for an Ava is in the most rigid corners of the room where the pressure is the highest and the room modes are most present. Sounds great, so I contacted local distributor Helios Pro Audio solutions for a review sample. I was granted two. Time to see what it does in my setup one. The ground floor of my house measures 9.85 x 5.21 meters and the ceiling is 2.58 meters high. It is divided into half by an acoustically rather open calic separation. On one side of this separation is the hall, stairway and kitchen. On the other side the living part. So half wavelengths matching these dimensions are 17.2, 32.7 and 65.9 Hz. The harmonics of the first two come rather close to the third at 65.4 and 68.8 Hz. Nevertheless, even at the couch opposite to the speakers, which is against the wall, lows are quite good. Despite just in front of the walls, there is an increase of bass since the reflected bass adds up to the direct bass. During test sessions I always sit on one third of the room, but for the rest I sit against the wall. Luckily the bass increment is more than acceptable. The equipment uses the core of representant setup one, the Air Acoustics AX520 that drives the PMC FAC12 signature loudspeakers on-stack audio over 70 isolators en connected over AudioQuest Robinhood Zero loudspeaker cable. De fronten van de loudspeakers zijn 96 centimeter's van de wall die je in fronten is en zijn alleen een paar degries toad in. De cord Dave is connecteet tot de amp over Grim Audio SQM XLR cable. Sinds de Grim Audio Mew 1 is sold en ik wacht voor de Grim Audio Mew 2. Ik gebruik de Magna Mano MK3 Farad Network Player, runnig Roopy XL, dat was connecteet tot de cord over de Network Acoustics Mew 1 XLR cable. Both the cord Dave en de Magna Mano receive power over a transparent power isolator 8. De Magna was connecteet tot de Zigsal router over de Network Acoustics Mew 1 Pro system dat cleans up the Ethernet signal. As said, the floor is a thin layer of oak on a damping mat on concrete. There are quite a few large plants around the living end and three small side tables. There's no carpeting. The Ava performs best where the sound pressure is highest. Using an SPL measuring app on my iPhone, the free DB Music app, I looked for the highest reading in the room. The app is particularly handy since it shows both A-weighted and C-weighted sound pressure level, SPL for short. For this measurement you can use either reading. PSI indicates that in most cases corners near the loudspeakers are often where the sound pressure level will be highest. Which was the case in my situation. I have only one real corner next to the right loudspeaker. De one near the left speaker is not really a corner for low frequencies since the cupboard under the stairs is only 83 cm deep. Remember, a 160 Hz soundwave is already 2.1 meters long while a 15 Hz soundwave is 22.7 meters long. Loos won't see that cupboard. The soundwave will simply fold around it. So I placed one Ava in the corner near the right speaker connected to the grid and linked my iPhone to it. As mentioned, you can also control the Ava with small knobs at the rear of the unit, but using the free app is a lot easier. And then I played some music. Right out of the box, switching the Ava on and off, it was almost impossible to hear what it did. So I wanted a low tone to play that would excite my room. I used on the run from the Pink Floyd album Delicate Sound of Thunder, the 2019 remix from Tidal. From 10 seconds to 20 seconds in, it has a deep loud sound. Playing that section, I switched on the Ava, paused the music and listened to the sound dying out. I repeated that with the Ava switched off, then increased the gain of the Ava and did the same test over again. I had to set the gain at 6 which is the maximum to get a very good result. With the Ava switched on, the sound died out directly after the music was paused while there was a short tail with the Ava switched off. The vague low level frequency energy surrounding the music also disappeared when the Ava was switched on. I never noticed this earlier, but now that was killed by the Ava. It was clearly audible when the Ava was switched off. Since Helios sent me two Avas, I unpacked the second one, linked it to my iPhone and placed it on one side of the couch against the wall. Then I repeated the aforementioned protocol, but that didn't give further effects. Not too strange since the result with only one was already good. Still I tried positions at the other side of the couch and next to the left speaker. I even placed the second one on top of the first. They seemed to be designed for that. But dry is dry. And admittedly for reasons I don't fully understand, the RT60 for lows wasn't that bad from the start. The Ava brings relaxation in the sound. The lows have more texture, sound more open. But the midrange also gains a resolution to a certain extent. The overall sound is less fatiguing while the sound without the Ava was already very good. I can assure you the Ava is going to be a permanent addition to my setup one while I thought I would not invest in it anymore. And on that bombshell we come to the end of this video. As usual there will be a new video next Friday at 5 p.m. Central European time. If you don't want to miss that, subscribe to my channel or follow me on Facebook so you will be informed when new videos are out. Help me reach even more people by giving this video a thumb up or link to this video on Facebook, Instagram of LinkedIn. It's much appreciated. Many thanks to those viewers that support this channel financially. It keeps me independent and lets me improve the channel further. If that makes you feel like supporting my work too, the links are in the comments below this video on YouTube. I'm Hans Beekhuyzen. Thank you for watching and see you next week. En whatever you do, enjoy the music.