Originally Posted by GeoJustGeo
Ok I guess my question is how much compression is too much compression? I thought the minute it showed up you were done and just default to the last sweep prior as a safe max zone for your sub's limit.
Is there a compression sweep guide lol?
That's a good question! I think that different people would define maximum safe limits in different ways. Personally, I would prefer to run my subwoofers as cleanly as possible, with sufficient headroom so that I had no compression at all. As a practical matter, I'm not sure that having a little bit of compression would be harmful to your subwoofers. It might, however, slightly affect your audio quality, depending on how noticeable it was. Remember that when the bass compresses, some frequencies continue to play louder, while other frequencies don't. The compression is rarely entirely symmetrical.
Nathan Funk, of Funk Audio, has stated that compression above about 50 or 60Hz is much more noticeable than compression below 30Hz, or especially below 20Hz. In his experience, some people are able to detect even 1 or 2db of compression at, let's say 60Hz, where even 3db at 20Hz or below might not be as noticeable. I think that individuals would have to experiment to find out where compression became noticeable to them, and the crossovers they used might be a factor in that.
Speaking personally again, and using Chucky's example, I might prefer not to go above the light blue line at 107.3db, and almost certainly not above the dark blue line at 110.1db, due to the compression occurring above 50Hz. Combined with the strong peak at ~42Hz, I think that the fact that the mid-bass frequencies stopped getting much louder might be especially noticeable to me with some content. But, I think that depends a lot on our own listening habits and experiences. Once we get used to a fairly smooth frequency response, we may want to add a house curve to lift the lowest frequencies, or to add some PEQ at specific mid-bass frequencies. But, it can be harder to go back to hearing randomly peaky bass, however it occurs.
If I were trying to advise someone else, my default advice would always be to have enough subwoofer headroom to avoid distortion, compression, or port chuffing. But, the reality is that we all enjoy slightly different aspects of our listening experiences, and how much compression is acceptable to someone is just one of many YMMV questions.