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In Reply to: MMG Frame posted by IEaudiodude on October 15, 2012 at 21:50:30:
Hi IE. It is looking mighty pretty! Here are comments that may be of use to you. I also hope that other people can find an idea or two.Bear in mind that my MMGs are older and not as wide as yours. Mine are 14" wide, yours are 15". Also, I do not use the subwoofer much for music. When I mention "bass", it is the MMGs' alone (mine reach 40hz@-6db). In addition, the line-level biamping has some bearing on what I observe. Lastly, I am sure that the room & layout itself will be a factor; experimentation will allow for better fine tuning. Ok, here we go.
- Your beautifully curved side additions will act as "Wings", as you probably already know. I stayed away from Wings for a long long time because few people reported good results with them in the archives. On one hand, Wings are expected to boost bass and I already had decent bass. On the other, they can also bring disruptions to sound quality. Yet, I finally adopted them to good effect!
- It did take a lot of experimentation, listening and measurement sweeps starting early last year. Importantly, my goal was NOT to boost the lower bass but to boost the 100-250hz range. Unfortunately, you can't get one without the other with Wings (I will return to this point shortly).
- Worse for me (or great if your MMGs lack bottom bass in the room) the lower bass gets more boost than the region where I wanted it. It helped there also, but not by as much as I wished at the time. In addition, I disliked other tonal & imaging effects of the Wings. So, at first, it was very discouraging. I only kept trying because I avoid using any electronic EQ/DSP.
- The initial breakthrough was what I called "Wingies", to remind me of the difference. Wings have a similar hard surface on both sides. OTOH, "Wingies" are wings that include absorption or sound dampening material on the back. Experimentally, layers of [cheap thin] cotton towels worked best in my case.
- This discovery led to a prototype using cheap Home Depot pine wood; a 1x6x4' (.75x5.5x48") length on the bass driver side. This equated to the minimum amount of wood surface area that I found sufficient during initial experiments. If I used another similar Wingie on the side of the tweeter, SQ was damaged (and bass went up too much). I'll return to this observation.
- These "minimum" Wingies still caused too much low end boost. To deal with it, I raised the MMGs by 6 inches. With this, I hit a sweet spot. Raising them killed some low end without losing the gains at 100-250hz. This design resulted in a an additional 6" low Wingie (cover) at the bottom. The resulting "L" shaped framing design was called "LWingies" by my wife.
- At this point, I had a minor but very meaningful gain in the 100-250hz area that I wanted. In addition, the low bass was strong yet not boomy. Any increase in Wingies surface area would make it too strong.
- The story does not end here but an observation is now in order. As I mentioned, adding SIMILAR Wingies on the tweeter side was not good at all. It was not just the boomy bass; SQ in general suffered. Also, neither with Wingies alone on the tweeter side, nor with Wingies in ADDITION to the one on the other side, could I get it to work. This is important because it may affect your design. Why?
- Well, because I found that the "Wingies" are bad for the tweeter side BUT "WINGS" are not necessarily so. Serendipity led me to find that a hybrid combo of Wings/Wingies -- working with other tweaks -- could take my system to a higher level of performance. One day, while meaning to demonstrate the "too much of the Wingies effect" to a friend, I forgot to add the towels to the tweeter-side wood pieces that I had just installed for the demo. So, I wound up with Wings where I wanted Wingies for the demo. Meanwhile, I still had Wingies on the bass driver side. In my earlier experiments, I had failed to check this combination of hybrid Wing/Wingies. (To be clear: Wings on the tweeter side AND the Wingies on the bass driver side.) Suddenly, I was hearing a most promising set of sound attributes and I was not even aware of what had caused it yet! I discovered my "mistake" shortly after. It was sounding very promising but not everything was right just then.
- I mentioned "working with other tweaks" in the paragraph above. That's because I did have to fine-tune the xover so as to "kill" the extra boost in low bass. Easy, and it actually was in plans for another purpose; I already had the right parts. All in all, I got yet another improvement in the 100-300hz frequency range while avoiding an undesired increase in low bass. I actually got even more benefits but that's another topic.
In any event, the initial implication of what I am saying is that "perhaps" you find that damping the back of the wood extension, on the bass driver side is indicated...but only on that side.
If you experiment with various cheap pieces of wood, you may be able to determine what works best in your room. Surface area matters more than shape. In fact, my first experiments where with almost square pieces of wood that I had at hand. I really was not taking Wings all that seriously at first but when I did, surface area became a key game changer. Each of your MMGs has 48 more square inches of frame than mine to begin with. Keep it in mind relative to the wood surface amount that worked here.
In the end, good as it was, the LWingies design was not final, at least for this room config. I now have a little problem. The nice "special order" exotic wood that I made the LWingies from, was scarcely enough for what I needed even then. Now I have to redesign with other woods. No complaints. It is worth it. Hopefully, your design will be optimized by the time you start cutting the good wood.
There's more to this but these are the basics of what happened here, in my room. Many people gave up on Wings in the past. I suspect that quite a few would have benefited from trying some Wingies approach.
Edits: 10/16/12 10/16/12
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Follow Ups
- RE: MMG Frame - JBen 02:00:05 10/16/12 (0)
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