adireaudio
You are viewing stuff tagged with adireaudio.
You are viewing stuff tagged with adireaudio.
Saved from Audio Karma ::
Well, it’s Minnesota, it’s been snowing most of the day already. So, time for a speaker post.
Project One, the HPM-60 ‘restoration.’ Actually, these were in fantastic condition when I got them from a fellow AK’er … thanks again! So, there wasn’t much to do at all. But calling it a restoration sounds cool. Anyways, I ordered the re-foaming kit from PE, but then decided to just go with Midwest Speaker Repair, which I got a fine deal on (and they’re near my campus). After that, we reveneered the sides with walnut. Now, if I remember correctly, these speakers are exactly two feet high on one side. When we bought the veneer, we stupidly assumed that when they said “24 inches” they meant a full 24” … So, there is anywhere from a sixteenth to an eighth of an inch gap between the bottom of the veneer and the bottom of the speaker. With a little plastic wood and sanding, it’s pretty hard to see. Shame it had to go that way, but I am happy with the results. The finish is less shiny than the ‘stock’ HPM’s, but that’s how I wanted it! Finally, gave the front a good cleaning around the drivers to give it some life again and now they’re almost done! (Did I mention how perfect the grills are?) Any advice on how to ‘pull’ the midrange dustcaps would be appreciated. I could always replace them, but considering a dented dustcap doesn’t affect the sound quality, I am content to leave well enough alone.
I’ve been out and about; I am back to write an update.
I’ve spent part of tonight modeling subwoofer enclosures on this great program called WinISD for the Shiva Mark III. The program has an unbelievable help file and a great graphing system. Now I just learned all this tonight, so bear with me: The idea of a ported enclosure is to increase the efficiency of the subwoofer driver; in other words, it makes it easier for the thing to move air when there is a hole in the box. Each driver reacts differently to the same box because they have unique sets of properties. This program allows the user to enter in those properties and then to run box size simulations. In the shot below I have a simulation of a closed box of 66L (4027.6 cubic inches), which is graphed in yellow. See as the frequency drops, the volume that the sub is able to produce in the box drops as well. Going from right to left, the yellow line drops off quite early. However, take a look at the green line. That’s a 100L (17.48” X 16.00” X 30.00”, 6102.4 cubic inch) box that is ported. “Ported” means it has a 4” square air “tube” that guides air out. The length of this tube is precisely calculated by the program as 22.4” (as you can see) and that is what lets the green line on the graph stay up higher. But, “that line drops off as well” you say? Not to fear, I can solder out (there are instructions, don’t worry) two resistors on the 250W plate amp that I am looking at and they will boost the green line by 4dB between 20Hz and 23 Hz, which will bring that green line nearly horizontal (albeit artificially for those last 3 Hz) down to 20 Hz, which is nearly feeling, not hearing, territory. Anyways, the box will be constructed out of MDF (haven’t determined the width) and I am waiting on more information on what to use to acoustically dampen the inside. Either way, I am pretty excited about the project - it has the potential to work. We’ll see, though. We’ll see.