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Old 7th May 2009, 08:05 PM   #1191
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Why not just send an email to RPG or to Hunecke or to Fraunhofer instead of speculating?????
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Old 7th May 2009, 08:07 PM   #1192
pjpoes is offline pjpoes  United States
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as I said, I did. I'm waiting a response. However, given the proprietary nature of these devices, I am guessing they won't tell me. They have "shut me down" before when I asked about how it works. The Modex plate seems disturbingly similar, the corner does not. I was most interested in the corner type application for myself, and had been paying most attention to that device and the device generically referred to as Modex. These two devices appear to be different from the Modex plate, but I could be wrong.
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Old 7th May 2009, 08:17 PM   #1193
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"Modex Plate" is foam + steel plate. "Modex Broadband" is foam + steel plate + foam. It all comes from Fraunhofer. Just read the docs on the RPG site.

"The Modex™ Broadband was developed by the Institute for Building Pyhsics at the Fraunhofer
Institute, and consists of a metal plate, embedded between two layers of damping material, surrounded by a
perforated metal frame."
(http://www.rpginc.com/products/modex...-Broadband.pdf)
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Old 7th May 2009, 08:22 PM   #1194
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yes I see all that now, as I said, I was looking at different Modex products. I didn't realize they were different.

It's the Modex and Modex corner that I was looking at, and those are the ones I thought were different. They are listed under residential products.

RPG got back to me and said that the MODEX and MODEX corner are their implementation of a more traditional resonant trap, with the panel suspended at the edges (in a proprietary way so they claim) and dampening inside the chamber, but not attached to the plate. The MODEX Plate is Fraunhofer's design, as you point out. They claim only the MODEX corner and Modex are designed for absorption at these very low frequencies (below 150hz).
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Old 7th May 2009, 08:26 PM   #1195
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you know what, the last part of what they told me doesnt make sense, they indicate on their website and in their graphs that the MODEX plate Type 2 is for below 100hz, and clearly show peaking at 40hz. Maybe he was referring to only the Type 1, I dont know, but clearly the Type 2 is also not their own design, and not like the MODEX or Corner.
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Old 7th May 2009, 08:28 PM   #1196
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They claim that their designs work lower than the Fraunhofer ones?
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Old 7th May 2009, 08:34 PM   #1197
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I think what he was trying to say was that the MODEX and MODEX corner can be custom built for specific applications, and is designed to have greater absorption at even lower frequencies, so yes. However, it's very peaky, as you can see in their graphs.

I also realized that he wasn't talking about the MODEX and MODEX corner as being the only ones for LF absorption, he said home lf absorption, I missed that word, so I'm guessing he meant, the only ones they designed to be sold for home use. It's a size issue I'm guessing, as they are typically smaller but deeper. In the email he indicated that if I needed it, they can make me a corner MODEX with a 12" depth which they have shown to have around a 1.2 absorption coefficient at 35hz. Also, they have a absorption coefficient of 1 at 50hz on the standard corner, which is inline with the German units, but in smaller but deeper package. Again though, it's clearly peakier yet (both seem peaky compared to what you see with a velocity absorber at higher frequencies).
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Old 7th May 2009, 08:44 PM   #1198
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Ok, anyway, I think this issue is settled. I think a device like this could be DIYed easily enough, and additional corner traps like the Modex Corner could probably also be made. Software called AcousticCalculator can be used to model what a standard panel trap will resonate at, then just add the dampening. Unfortunately, there is no software I know of that can model the dampening or the German design, but I'm going to guess that if you model the panels mass correctly, it would be very similar.
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Old 7th May 2009, 08:46 PM   #1199
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Dr. Geddes, I emailed you a while back about building me a bandpass box for my drivers. I'm wondering if that is still a possibility, as it would be a nice summer project, now that I'm probably going to be working less. Let me know, and I will try and get you some data for the driver. All I need is the design and panels cut.
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Old 8th May 2009, 12:13 AM   #1200
gedlee is offline gedlee  United States
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Quote:
Originally posted by markus76
TRADERXFAN, thanks for reading my links. Looks like this is something not many people do
Markus

I read them all. You just don;t want to hear about it.

Putting the panel between two pieces of foam would be broadband and *maybe* new. But I'll stand by my statement that only the lowest mode of the plate has any significant effect.
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