Yep, this is what it looks like for me as well. I was under the impression that it should stick around 0.3 …
Forgive the newbie!
Hi @OCA,
Thank you for sharing your knowledge here - it’s much appreciated.
I’ve included my current frequency response below which I’m happy with save for the 38hz spike.
If I just wanted to reduce this how would I best implement this?
Sorry for my naive question but I would like to hear your view.
Many thanks,
38Hz spike is a standing wave formed between your front and rear walls in your room which must have a length of around 4.5 meters. This is independent of where you place the speaker or where you sit in the room (hence the term “standing”). You can get rid of that in many ways including an IIR EQ filter, FIR filter generated by inverting over a flat target response as explained in this tutorial and by creating a counter standing wave with opposite polarity. In my experience, the last option is the best in terms of artifacts, ringing and clarity. I called it virtual bass array as it’s the digital version of something widely used with subwoofers on opposite walls. It’s the first filter explained in this video below:
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…or if you don’t want to deal with all the calculations, just download the zip file below and direct your Roon convolution engine to that stereo, 44.1kHz zip file (Roon will upsample it as necessary):
https://drive.google.com/file/d/1g4uuNpsm_jHIjiklaOrrfTAP_w3ODU_J/view?usp=sharing
Normally, it should be done separately for left and right channels and optimized for the exact peak frequencies and magnitudes but this should still work quite well simultaneously fixing some dips which you cannot otherwise touch.
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Hi,
Thank you for the very prompt response.
I thought VBA filter would be the one and did reduce 38hz spike but seemed to create more peaks and dips than original frequency response from 60 to 120hz range.
The inverted filter as per instructions looks to flatten from 20 to 24000hz. I suppose I’m asking whether this could used between say 20 and 200hz?
Sorry to trouble you and thanks again.
Iain
The filter I made above for you doesn’t have any effect beyond 95Hz!
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OMG that’s brilliant. I’ll give it a try. Thanks Iain.
Hi Serkan,
Apologies, I can’t get file to open.
If you share details input to create the VBA filter I will try to recreate in REW.
Sorry but I really appreciate your knowledge and assistance.
Thanks again.
Hi Serkan,
Quick update whilst I couldn’t open in REW I’ve been able to upload direct to Roon and is working pretty well I’ve got to say from sketchy information provided!
If you do have a moment, to share your methodology used to, I’d like to understand so I don’t have to bother you again 
.
KRs you are a gentleman.
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It was supposed to work with Roon convolution but you can drag and drop the .wav file in the zip to REW and multiply it with your speaker response to see its effect. You should apply a -117dB SPL offset to it before you use it in vector multiplication though.
I attached the actual .mdat and rePhase files to cretae the filter here:
https://drive.google.com/file/d/1WXJCOCuN9gzpfvvkRh6_OBfRgXY4Dgns/view?usp=sharing
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Thanks Serkan, the filter you produced is way better than those I attempted!
Also did the offset and vector multiplication as you advised and looks pretty good in REW too.
I owe you several 
.
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Like Iain, Serkan hooked me up also and made me the VBA filter yesterday since I found it slightly difficult at first try. Once again, many thanks! This filter is much better than my regular PEQ filters manually made in REW EQ.
Today I properly concentrated on the process and finally was able to make the VBA-filters from my own measurements with the help of the tutorial video. I wanted to learn the process if I need it in the future when I eventually move the speakers or listening spot. At this time, I didn’t go further than Filter 1 (VBA) since that already solves the biggest problem I have, which is the room mode at ~36hz. Here’s a pic of the FR before and after VBA, which obviously doesn’t tell you all but gives some idea. With VBA (compared to my manual EQ), bass is now tighter, hits lower and with more power and there’s just more balls to it. This filter is pure genius, thanks again Serkan!
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Dear Serkan, thank you for your video guide. But for me, as a person who does not understand English well, it is very difficult to do all the operations on the video. I think that the whole community will be immensely grateful to you if you can attach a text step-by-step description to this video. Thank you in advance for this titanic work. And I look forward to your feedback!
The video comes with a pdf guide which you can google translate to any language you want. Also in youtube, you should be able to get english subtitles auto-tranlated to any language. But if you still run into problems, let me know and I will try to get my .doc version google translated.
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Don’t know about your speakers/subs, but there’s still quite a suckout between 40-60Hz, an area where much of the musical foundation is located.
So if you’ve got subwoofers, changing locations would probably be easier than with speakers and could gain you a substantial smoothing in the low bass.
Yeah I wish there was something I could do to that, but not in this apartment. The speakers (ATC SCM50ASL) are where they are since this is a living room + open concept kitchen space. Placement is asymmetrical and has been checked by measurements and ear. Listening spot has been adjusted with RTA and by ear to get best balance to low end. Moving the sweet spot closer to back wall does make the 40-60hz dip smaller but at the same time makes the room mode at ~36hz much worse and also makes the curve worse on higher frequencies. Also it sounds worse subjectively. With Serkan’s filter the end result is great. I think my response is very good when compared to many I see online nowadays with much worse dips and peaks. Also it sounds better than ever with VBA. The measurement I posted shows 1/6 smoothing, with psychoacoustic smoothing (what we actually hear) the dip doesn’t look bad at all.
Serkan, thank you for your answer, I apparently did not carefully examine the attachments under the video, so I did not see the pdf file. Of course I can translate this manual into Russian. Thank you for your help, you are doing a very good job for all audio lovers!
Dear Serkan, I got infected again with the information under the video and did not find a manual in pdf format there. Maybe I’m looking in the wrong place? I would appreciate it if you can show me where your guide is.
This is the pdf:
https://drive.google.com/file/d/17BwTGv933w4id3B3PFHy2zjyijtgZLDX/view
And this is the Harman curve:
https://drive.google.com/file/d/1N9C7lmawVAoxB8PkQjuno7drHSwWuO8W/view
You can also find them under ‘more’ right next to the title of the video.
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