 Simple room acoustics problems, like room modes, might be solved without shifting the problem to monetary conflicts if you play music from audio file player software in your computer. Let's see how that works. In my video, Loudspeaker Placement, the long version, I explain that two groups of acoustical problems might arise when placing speakers in a room. Problems be low, roughly 200 Hz and problems roughly above 600 Hz. The first group has to do with the size of the room and the low frequency wavelength, where half the wavelength equals the distance between two room boundaries, we speak of room mode. As soon as a wave with such length is produced by your stereo, it will cause a resonance in the room. When room treatment is done, often so-called bass straps are used. These are a kind of black holes for the lower part of the frequency band. Sound that enters the bass trap will be converted into another form of energy, like heat. But they are not always practical and often not aesthetically pleasing. So what if we don't have our stereo play the room mode frequencies and its first few harmonics? I have tried this using the room parametric equalizer and it worked quite well. Other player software has equalizers aboard and thus can be used too, like J-River Media Center 24 and Audivana 3 Plus. As always with room correction you must place your loudspeakers as good as you can before you even consider room correction. Again, my two step approach for loudspeaker placement video tells you exactly how to do this. The link is in the show notes. Also do realize that corrections you make on your listening position might only be appropriate for a small area around that position and might not work at other listening positions since standing waves have a position bound behavior. The goal here is to only filter out those frequencies that would agitate the room modes so the differences per place in the room might be smaller than when equalization over the low of 500 Hz is used, as room correction software often does. This is how I went about it. I installed a simple third octave graphics analyzer on my smartphone and monitored a number of tracks that contain a fair amount of low end. Over these tracks the 125 Hz bar often peaked higher than the neighboring bars. If I would only have monitored just one track the peaking could be a fingerprint of that recording. By monitoring several clearly different tracks this is avoided. So now I know that somewhere around 125 Hz there is a resonance but I want more precision. Making high precision measurements on low frequencies in a room is rather complex but since room modes are the consequence of the spacing of walls I calculated the frequencies. That can be done since we know what the speed of sound is, which is about 334 meters or 1100 feet per second in dry air, at sea level and at 20 degrees Celsius or 68 Fahrenheit. In other words in the standard climate as used by aviation but usually doesn't occur on many places on the earth. I say this to prevent you from calculating frequencies with three decimals to be exact. Routing at integers doesn't harm. Now the speed of sound. Some use 331.2 m per second at speed, which seems to be scientifically correct. Others use 333.3 m per second since that would give 1 km per 3 seconds. And I have used 334 m per second in the past so I will consequently keep using that. The differences are only of academic importance since in most instances climate conditions will differ anyway. The ground floor of my house is almost completely open with the exception of the hall and the cupboard below the stairs. Halfway there is a room divider that for low frequencies is acoustically transparent. So acoustically the room is 10.6 by 5.4 meters. To find out the frequencies that belong to these measures some complex math is needed for we need to divide the speed of sound by the length in meters, or feed if you prefer. I will use meters, so brace yourself, here it comes. The speed of sound is 334 meters and the length of the ground floor is 10.6 meters. So we divide 334 by 10.6 to find 31.509 434 339 Hz, which we round off to 32 Hz. We do the same for 5.4 meters, 334 divided by 5.4 is 61.8518519 Hz, which we round off to 62 Hz. Room modes start working at half the wavelength, so in my case 16 and 31 Hz. 16 Hz is so low that I don't expect problems there, but the full wavelength is 32 Hz, which is about equal to 31 Hz. And the harmonics are at 62, 64, 93, 96, 124 and 128 Hz. I decided to filter at 32, 63, 95 and 126 Hz and play with the width of the filter. The 126 Hz must have been the problem I have seen on the 3rd octave analyzer and I will try the lower 3 to see what impact they have. I will use these frequencies in the examples below but you should of course use the problem frequencies of your room. To filter out a very small part of the frequency spectrum, we use the parametric equalizer. It has this name since all parameters that define a filter can be varied. Center Frequency, Gain and Cue Factor. The center frequency is the frequency that is attenuated or amplified the most. The gain defines the amount of attenuation of amplification and the Cue Factor defines the width of the filter. It might be clear that we want to maintain as much low frequency energy as possible and only want to lose the problematic frequencies. So we are going to use a very narrow filter and thus a very high Cue Factor. Now let's see how we do this in three software players, Roon or Divina Plus and J-River Media Center 24. After starting up Roon, click the volume control in the lower right corner and click DSP. Select Parametric Equalizer in the left column. If it isn't present, first click Add Filter in the lower left corner and select Parametric EQ. Now you see four peak-dip filters set at 0 dB gain. Click on the pencil on the first filter and choose Bandstop. Set the frequency to 32 Hz, or your frequency of your home of course, and the Cue Factor at 15. Do the same for the next three filters but set them for the three higher frequencies, 63, 95 and 126 in my case. You can experiment with more filters at higher multiples but it brought me no further improvement. Now the filters are set, we want to go to Headroom Management. I set the Show Clipping Indicator to On and set the Headroom Adjustment to minus 3. This is needed to give the DSP function room to calculate without clipping. The clipping indicator is integrated in the signal part light that will turn red when clipping occurs. If that happens, just load the Headroom Adjustment DB setting with one or two more DBs until the clipping goes away. In Audivana go to Preferences and select Audio Units. Select AU Parametric EQ and click Configuration. Now drag the white dot to the right frequency or alternatively click on the frequency and change it to 32 Hz. Also change the gain to minus 20 dB, which is the maximum setting. Change the Q into 15 and click Apply. Take this for three more filters using the three frequencies you have found, in my case 63, 95 and 126 Hz, as frequency or rather use those frequencies that give problems in your room of course. Click the Use Audio Units Effect checkbox and you are set. In Media Center, open the menu Player and select DSP Studio. You can also use Command D on a Mac or Control D in Windows. Click Add and select Parametric Equalizer in the left column. Do not use Room Correction. And select Adjust the Frequency. In the lower part of the window enter 32 at frequency, 15 at Q and minus 40 at Gain. Leave left right as it is. Click Add again and enter 63 Hz frequency, 15 at Q and minus 40 at Gain. And do this again for the other two frequencies. Of course you need to enter the problem frequencies of your room. Now the filters are set, listen to it for a week or so, then switch them off again and listen if the filters improve the sound quality. It is important to get used to the new sound before judging since our ears correct for coloration to a certain degree and removing the room resonances will decrease the level of low frequency energy to a proper level but our ears, rather our auditory system, might initially experience it as lacking bass. So by listening to the new sound for a week that will be reset. After a week listen not to the timbre but to the details you can hear in both situations. So not how much bass is heard but how precise you can follow the bass lines of the instruments. If it doesn't work, switch off all filters but the one closest to the dominant resonance you saw in the third octave analyzer and start playing with that one. Vary the frequency slightly or play with the Q factor. If that improves the sound use the same Q factor for the other filters and use the integer division of the dominant frequency. When in doubt you could switch off three of the four filters, reduce the playback level on your amp and choose an amplification of 10 dB in the dominant frequency filter. Then vary the frequency until you hear a strong increase in level. By boosting you agitate that frequency easily but therefore make sure you play it at a low level. If that doesn't work well, temporarily low the Q factor to say 5. After finding the resonance frequency set the gain back to the initial attenuation and increase the Q factor to regain the fullness without exciting the room resonance. Then when ready set the other filters to the same Q factor and use integer divisions of the frequency used in the dominant frequency filter. This simple and cheap method will usually yield lower results than professional acousticians can achieve. Even if you would have the same education professional acousticians have, you would lack the experience. Well despite all the computer models they can use, like ray tracing software, it appears that experience is eminent and it doesn't come cheap. But if your room and speakers pose little problems, this is a fine and cheap solution. You might lose some quality due to the signal processing. How much is easily tested by disabling the filters and do a minus 0.1 dB low frequency high Q filter will be inaudible to our hearing so if there is a degradation in sound, it's due to the DSP algorithms. Room correction takes time to do well and that's not different in this situation. And you are on your own, I can't help you, for each and every situation is different and I simply can't spare the time to give you personal support. But I am researching automated systems, like direct in the NAD receiver I described already. So if that's more your thing, subscribe to this channel or follow me on social media. If you like this video, please consider supporting the channel through Patreon or Paypal. Any financial support is much appreciated. The links are in the comments below this video on YouTube. Help me to help even more people enjoy music at home by telling your friends on the web about this channel. I am Hans Beekhuyzen, thank you for watching and see you in the next show or on theHBproject.com. And whatever you do, enjoy the music.