miniDSP SHD integration

@erik_squires 

Lately I have seen you mentioning plugging ports on the mains to help with bass control. Obviously you must be on the camp of those who don't think the speakers can be hurt by plugging the ports. Can you elaborate on that and how you actually plug them. Socks, straws, part or whole? Sorry for hijacking the thread.

Hey @baylinor - You can’t hurt speakers by plugging ports, but you are changing their behavior. The behavior when plugging any ported speaker is going to be rather similar. You raise the -3 dB point, but also dampen the response. That is, if there’s a peak at the low end, the peak will be reduced. This behavior may be beneficial in some cases. Some speaker makers go so far as to include foam plug for this reason. For instance, bookshelf speakers which you might want to put all the way up to a wall.

From an academic, absolutist perspective, plugging a port is not the same as making an ideal sealed speaker.  Generally, sealed cabinets should be somewhat smaller than their ported counterparts, so if this was an engineering exercise you'd build 2 different cabinets, one for sealed and one for ported use, but from a pragmatic approach, several speaker designers and my own experience shows this approach can be useful if you have too much bass or are integrating speakers with a subwoofer.  It will also reduce cone excursion and distortion, an especially valuable feature if adding a sub without a high-pass filter.

The only way to know if this is right for you is to try it. I’ve had one A’goner report their bass was best with 1 of the 2 speakers plugged. I imagine this achieved a half-way setting between the two options.

You can actually improve reliability because having a sealed cabinet reduces the amount of motion the driver makes below the port frequency. Below resonance, the port is basically just a great big hole. That is, the springiness of the air in the cabinet which helps to control the woofer motion vanishes. The cabinet might as well not even be there. The THX standard for satellite speakers was to use sealed cabinets, because when combined with high pass filters the combined response would match subwoofers ideally. This is not as good a solution as the THX specs, but it shows that when adding a sub this approach can be useful.

I recommend virgin alpaca socks... :) Definitely not anything crunchy. Nice clean socks wadded up tightly which you can still pull out works just fine. You also don’t have to fully pack the port, just seal the ends, so if you have a very deep port, say 6" long, you don’t have to stuff the whole thing. Just a tight sock on the opening to prevent air from moving in and out of the cabinet is fine.

Much appreciated. It's only my streaming that at times needs some taming of the bass which I do on my dual subs. I did try plugging the ports on the mains before with similar results but was worried about messing with the integrity of the mains. Your explanation is reassuring.

@baylinor if you find yourself adjusting bass levels for music too much you may have some resonances you can tame with EQ if not otherwise.

Some music may excite a room mode, which has you reaching for the volume control.

Check the AM Acoustics room mode simulator for help placing your speakers, then measure and consider bass traps and/or EQ if the problems are still pronounced.

My issue is strictly music related. I use my streamer almost entirely for electronic music and like to play it at 75 db, hence the overamplified bass issue. My vinyl and CDs collections have less than 5% electronic music and bass is perfect.