Hello again,
so I am back after about a year of not having any reply to my latest post. Regardless I will lay down a few thoughts on how I am planning to move on and hopefully get some opinions on that.
So while trying to find out what would be best for improving the frequency response of the room I ended up leaning towards the helmholtz slat resonator. My aim is to decrease the response graph roughy between 150 - 570 hz so that it is closer to flat. Now, while trying to estimate the construction dimensions and shape I found out that it would be quite hard to cover all that frequency range with a single unit , so I thought of splitting it into two parts. The first part will be roughly 320-570 hz and for this I have already made a sketch which I upload here.
[Please keep in mind that the dimensions of the "box" don't include the timbre dimensions, because I don't know them yet (haven't chosen the timbre that 'll be used), so consider these dimensions as the inner cavity dimensions.]
But I have a few things that I haven't cleared up yet in my mind. In this calculator the picture shows (and takes in account) the distance from the wall.
http://www.mh-audio.nl/Acoustics/SlotAbsorber.html1. One thing that confuses me though is whether the construction (resonator) includes the space between the "timber frame" and the "wall", or is this space just empty space, and not part of the airtight cavity of the resonator? In an older Stuart's post in legendary John Sayer's forum he had mentioned that the resonator could be angled to the wall, so that leads me to conclude that the space behind the timbre is not supposed to be part of the construction, but then again I am concerned as to why is the construction supposed to be airtight , if the space outside it ( behind it ) is influencing its performance.
2. How much insulation should I use? Some use 2/3 of the cavity, others like in the picture of the link above use much less. I know the more is used the more broadened the range of affection will be, but I have calculated the dimensions of the box so that it will strictly affect only the swelling between 320- 570 hz. If the effect is broadened , it will go beyond these boundaries and this, of course is not desirable.
And my the way, is the insulation supposed to be appended on the back of the front "face" as in the upper link sketch, or could it be anywhere in the airtight cavity?
3. Correct me if I am wrong, but from what I have understood , the device primarily relies on friction at the opening areas to attenuate the desired frequencies' amplitude, so practically I could build the construction without any insulation at all, right? Or maybe with just a little on back the "face" (front) side, as shown on the upper link (calculator).
4. How am I supposed to fit the insulation behind the "face" (front) and keep it in place, inside the cavity? The timbre slats will be placed lastly, at the end of the construction, so where and how is the insulation supposed to be "stuck" on them, since it should be placed prior to the slats. Please forgive me because English is not my main speaking language, but I hope I am making my thoughts clear here
5. Should I begin with a slot or a slat at the edges of the front face, or does it not matter that much?
6. I am thinking of making the front face able to be easily taken apart and put back together , so that I could edit the construction with relative ease if necessary (trial and error process). This way I could e.g. add or remove insulation if desired. Probably with rubbers (to keep it airtight). Do you think this is a good idea?
7. Do you think that the dimensions of the construction are sufficient for the size of the room and the problem I am trying to fix?
There are also a few more things I am considering about for the room acoustics enhancement:
8.One is to use plastic stripes over the existing insulation (e.g. at the corners) as reflecting points of higher frequencies , to keep them "alive" in the room. I remember Stuart mentioning that a few times, but the problem is I don't know what thickness and density they should be , and how these relate to the targeted frequencies. Any idea on that?
9. I am very much intrigued by the thought of building a 1 dimension QRD diffuser on the back wall. Now I know that there is a certain distance needed between the wall and the sweet spot (Stuart mentioned 6 meters in an old post in John Sayer's forum, but hopefully he was targeting really low frequencies). AFAIK there should be at least 2 full cycles of the lowest targeted frequency between the device and the sweet spot for the lobbing to smooth out, so maybe if I built QRD tuned from e.g. 550hz and above I should be ok, right?
Generally is it a good idea to go with diffusion on the back wall of such a small place or should I stick to absorption and HH resonators?
And by the way, is there any performance difference between 1d and 2d diffusers?
10. As I have mentioned before the room includes a ceiling cloud with 30cm of insulation. I remember once Stuart adviced me to make it hard back and angle it so that it would redirect the sound towards the back wall. I am considering doing so for the half of the cloud (at the points where first reflections hit from the speakers) and keeping the rest as it is with insulation. Stuart, if you ever happen to read this I would much like your opinion as to how dense and thick the timbre used should be. Could I maybe use plastic instead? And what about the rear wall? Should I use absorption, diffusion , or maybe a HH resonator?
So that's it for now,
Thanks in advance for any help!
God bless everyone!