Page 1 of 4 1234 LastLast
Results 1 to 10 of 39

Thread: RPG Modex Plates-"Free" Bass Traps

  1. #1
    Member Sponsor Addicted to Best! dallasjustice's Avatar
    Join Date
    Apr 2011
    Location
    Dallas, Texas
    Posts
    2,090

    RPG Modex Plates-"Free" Bass Traps

    Okay. I don't mean they are free of cost. As a matter of fact, they are very expensive. They are probably the most expensive bass trap on the market. However, I think they are the best value going in room acoustic treatment. This last weekend, my dealer Scotty Warren and friend Bill Gainer installed 3 additional modex plates into my room. Before these 3, I already had 6 modex plates in my room. In the post below are some pictures of the side walls and and rear walls before the new modex plates were install. I am showing these photos to demonstrate how many "conventional" panels a modex plate can replace. Later on, I will explain AND demonstrate the advantages Modex Plates offer over fiberglass panels (even great ones like RPG BAD panels). You might also ask me; Why would you want to add 3 more Modex Plates to your room? Isn't 6 enough already? Before I do that, I think it's important to discuss how fiberglass panels work and how that's different from a VPR like the Modex Plate works.

    PRESSURE VS. VELOCITY

    The standard in room treatments has been fiberglass panels. They can be very effective at reducing low frequency ringing from about 100hz to 300hz. Their performance can even be extended below 100hz depending on their thickness and some other mounting tricks. Fiberglass works on velocity. Fiberglass can reduce the bass wave's velocity and thereby mitigate room ringing. Of course, velocity is at its greatest away from the walls in a room. So fiberglass doesn't work so well mounted directly onto a flat wall. However, fiberglass can be mounted on "off sets" which create a 4" air gap from the wall. This can greatly increase their performance along with using very thick panels.

    There's a "cost" with fiberglass though. Fiberglass will absorb a lot of midrange and high frequencies. Moreover, the closer a panel is located to the speaker, the more the panel will color the speaker at the seated position. This is especially true if one elects to use absorption on sidewall lateral 1st reflection points. I know there's much controversy here and Floyd Toole has done some research suggesting that no panels should be used in this location. However, there's no universal here. In my case, I like to use absorption at these reflection points. I believe I can get a smoother midbass and the measurements bear that out. However, it takes a lot of fiberglass panels to do the trick. And even the best fiberglass panels will absorb a little too much midrange and high frequency. RPG BAD panels are designed to mitigate this effect with a perforated wood plate which is mathematically proven to diffuse the mid and HF much more evenly. However, even BAD panels aren't great and too many of them can reduce the decay times in a room to a VERY low level. So, that's the cost for fiberglass. You have to use sooooooo many of them to get great bass that you suck out too much HF and make the room sound a little unnatural.

    RPG Modex Plates work by reducing bass wave pressure. I don't know how to build one and I can't give you a technical paper on how they are designed. I know that RPG sells them on license from a German manufacturer. I don't believe there are any other companies selling VPRs. Modex Plates must be mounted directly onto a wall wherein high pressure bass energy accumulates. So, knowing where to install the modex plate requires some basic room acoustics knowledge. In my case, my room is 14'6" wide, 24' long and 9'3" high. Of course, the lowest frequency ringing is length axial with the most dominate mode being 47hz and another half wave at 23hz. There would be many others as well if the room were untreated.

    At this pointed, my room is very well controlled in the low frequencies. A few years ago I started getting room acoustics help from Nyal Mellor. This relationship started me on the path to room acoustics learning. I've learned a lot since then. I regularly use a mic and REW. Let's just say that the room treatment, my seated position, speaker positions, digital crossovers, DSP and subwoofers are not haphazardly setup in my room based on hand claps or listening to the soundtrack for The Movie U571 or Saint Saens Symphony No. 3.

    Yes, I said it. Modex Plates are "free." They don't absorb midrange and high frequency. The absorb low frequencies better than any other product on the market. That's actually a fact and RPG has real data testing to prove it. So, I'm not blowing smoke here. These things work very well. I am going to post some pictures below starting with what my room looked like before I install these last 3 modex plates. Then I will show some photos of the install and finally some photos of what they look like now.

    I have been taking REW measurements and I am confident in saying two things.
    1. The3 Modex Plates (1 type two Modex Plate and 2 type one Modex Plates) installed easily perform as well or better than all of the 8 very thick fiberglass panels and two QRD diffusers (6 of which were BAD panels). Most of these panels were at least 5" thick, some thicker.
    2. The decay time in my room is greatly improved since I've removed these numerous fiberglass panels from my room and replaced them with 3 "free" Modex Plates.
    Name:  IMG_0351.JPG
Views: 2009
Size:  100.4 KB
    Last edited by dallasjustice; 06-22-2015 at 04:40 PM.
    MUSIC IS GOOD

  2. #2
    Member Sponsor Addicted to Best! dallasjustice's Avatar
    Join Date
    Apr 2011
    Location
    Dallas, Texas
    Posts
    2,090
    Some before pictures

    Name:  IMG_0354.JPG
Views: 1923
Size:  66.3 KBName:  IMG_0360.JPG
Views: 1632
Size:  91.5 KBName:  IMG_0361.JPG
Views: 1893
Size:  70.2 KBName:  IMG_0362.JPG
Views: 1689
Size:  57.1 KB
    MUSIC IS GOOD

  3. #3
    Member Sponsor Addicted to Best! dallasjustice's Avatar
    Join Date
    Apr 2011
    Location
    Dallas, Texas
    Posts
    2,090
    Here are some installation photos staring Scotty Warren the Modex Plate installation guru.
    Name:  IMG_0364.jpg
Views: 1858
Size:  35.9 KBName:  IMG_0366.jpg
Views: 1606
Size:  38.4 KB
    Last edited by dallasjustice; 06-23-2015 at 07:40 PM.
    MUSIC IS GOOD

  4. #4
    Member Sponsor Addicted to Best! dallasjustice's Avatar
    Join Date
    Apr 2011
    Location
    Dallas, Texas
    Posts
    2,090
    Here is a photo after the install of a sidewall.

    Name:  FullSizeRender.jpg
Views: 1721
Size:  216.0 KB
    Here is backwall:
    Name:  image.jpg
Views: 1819
Size:  613.2 KB
    MUSIC IS GOOD

  5. #5
    Member Sponsor Addicted to Best! dallasjustice's Avatar
    Join Date
    Apr 2011
    Location
    Dallas, Texas
    Posts
    2,090
    I will post REW plots tomorrow. The overall SPL will be virtually identical. However, I expect to see longer decay times in midrange and high frequencies.

    Subjectively, the longer mid and HF decay was the first and biggest impression. The sound is so much more open. The soundstage is wider, deeper and inner nuance is heightened. The bass sounds just as great as before. So, it's a win-win!!
    Last edited by dallasjustice; 06-22-2015 at 05:46 PM.
    MUSIC IS GOOD

  6. #6
    Member Sponsor Addicted to Best! dallasjustice's Avatar
    Join Date
    Apr 2011
    Location
    Dallas, Texas
    Posts
    2,090
    Here is right channel before and after the three new modex plates at 1/12th per octave resolution. The before is a stereo sub measurement, so the very low bass is smooth with two mono subs versus two stereo subs. I prefer listening with the mono subs. It sounds much better. Green is before and yellow is after. These are actual measurements from the seated position after Audiolense digital crossover and target curve application.
    Name:  yellow after green before.jpg
Views: 1683
Size:  63.4 KB

    You can see that the SPL and especially the bass matches my target curve very well. I prefer a downward sloping target curve. This is perceptually flat and the most subjectively desirable target. Overall, the sound quality is mega; never-heard-before; whatever else you want to call it.

    The following is RT60. RT60 tells us how long it takes for a signal to fall by 60db. Its not the perfect measurement for small room decay. But it IS very useful in comparing different setups. There is a sweet spot for decay; no doubt about it. If you want to read more about where the sweet spot should be and how decay should be shaped, I highly recommend Nyal Mellor's article he recently published on the topic.
    http://www.acousticfrontiers.com/und...79b6-408472965

    Again, green is before and yellow is after.
    Name:  yellow after green before rt60.jpg
Views: 1619
Size:  49.5 KB

    These graphs tell us two things.

    1. The bass is just as good, if not better, after the 3 modex plates were installed and the 8 fiberglass panels removed.
    2. The decay time is greatly improved in two ways. First, the decay is smoother without all of the fiberglass panels and the three modex plates installed. Second, the decay time in the midrange and higher frequencies are significantly increased. Previously, the room was on the edge of acceptable decay time. Some folks may have thought the room sounded a little to anechoic, if you will. I personally felt the room sounded great but I also knew it could be improved.

    Now, with the longer and smoother decay times, its the soundstage that gets the mega upgrade. The soundstage is much wider and deeper. Also, the smaller high frequency details like the nylon tipped drum stick tapping the high hats, are so much more clear. Also, I was surprised to discover that vocalist intelligibility is greatly enhanced with slightly longer and smoother decay times.

    Was it worth all the money and trouble? Absolutely! I could have spent that money on a new DAC/ADC or a fancier speaker cable. Would I have been able to get the same level upgrade in my system had a spent that money on something else? No way, no how.

    Michael.
    Last edited by dallasjustice; 06-23-2015 at 06:51 PM.
    MUSIC IS GOOD

  7. #7
    Industry Expert [Industry Expert] Nyal Mellor's Avatar
    Join Date
    Jul 2010
    Location
    SF Bay Area, CA, USA
    Posts
    591
    Great posts!

    Worth mentioning there are three different types of Modex Plate.

    Type 1 works from 65-300Hz. Uses a 1mm steel plate. Steel plate is the outermost layer facing the room. 4" of absorption behind that.
    Type 2 works from 40-100Hz. It uses a thicker 2.5mm steel plate than the Type 1. Steel plate is the outermost layer facing the room. 4" of absorption behind that.
    Broadband works from 65-5000Hz. It uses the same steel plate as Type 1 but sandwiched between two layers of 2" absorption.

    The technology was developed by Fraunhofer, it is also known as a VPR. Fraunhofer license to Renz who manufacture the product, RPG import from Renz. RPG will wrap the Modex in any fabric, or you can get it without a fabric wrap, in which case the finish is white perforated metal.

    They are very good products, and work as advertised. The only downside is their expense. However you need to factor into that their size and compare that to the 2'x4' standard acoustic panel size. The Modex are 3'3" x 4'11". Pretty much double the surface area of a 2x4 panel.

    To deal with the sub-100Hz range I advise a combination of proper shell design ("floppy walls"), multiple subs and EQ. See a blog article I wrote called Five Steps to Amazing Bass.
    Acoustic Frontiers - specialists in the design and creation of listening rooms and home theaters. Experts in room design, sound isolation, acoustic treatment and AV electrical systems.

    High-end audio equipment from: ATC, Aurender, DEQX, Devialet, Exasound, JL Audio, Torus Power, Wireworld.

  8. #8
    Site Founder And Administrator Steve Williams's Avatar
    Join Date
    Mar 2010
    Location
    Coto De Caza, California on the 13th fairway of the south golf course
    Posts
    26,492
    How much is each one of those
    Steve Williams
    aka oneobgyn
    There's ALWAYS another Steve Williams BUT there's only "oneobgyn"
    USA Dealer of Center Stage Feet and owner of PitchPerfect Sound (www.pitchperfectsound.com)
    Dealer Lamm Electronics
    My System

  9. #9
    Member Sponsor Addicted to Best! dallasjustice's Avatar
    Join Date
    Apr 2011
    Location
    Dallas, Texas
    Posts
    2,090
    Quote Originally Posted by Steve Williams View Post
    How much is each one of those
    They are priced by RPG based on the order. The prices don't include shipping, which isn't cheap. The type 2 is usually listed around $1,500 and the type 1 is usually listed around $1,200. So, they can really add up fast. IMO, they are well worth it since there's zero competition in terms of performance or aesthetics. They are only 4" deep so they look very nice.

    In my room, I have 3 type 2s and 6 type 1s. I bought them at three different times because I could really afford to buy all at once, I thought. When Nyal first advised me to buy them a couple of years ago, I think he told me I could easily use 9 in my room. I almost fell out of my chair. Looking back, it would have been wise to just bite the bullet.
    MUSIC IS GOOD

  10. #10
    Member Sponsor Addicted to Best! dallasjustice's Avatar
    Join Date
    Apr 2011
    Location
    Dallas, Texas
    Posts
    2,090
    I also want to mention something about installation. Scotty has probably installed 20 plates now. He uses a special type of lag bolt which works super on drywall. There's no need to drill into studs. Hopefully Scotty can chime in here. My room has pretty flat and symmetrical walls. But Ive seen a few problem installs in cases where the wall isn't totally flat. You'd be surprised how often walls aren't totally flat.
    MUSIC IS GOOD

Page 1 of 4 1234 LastLast

Similar Threads

  1. Replies: 105
    Last Post: 09-21-2016, 06:34 AM
  2. Replies: 20
    Last Post: 05-28-2016, 04:58 AM
  3. RPG Modex Plates (35Hz) placement question
    By stevekale in forum Room Acoustics Forum
    Replies: 89
    Last Post: 10-05-2013, 03:09 PM
  4. This is what "real" bass looks and sounds like
    By amirm in forum General Audio Forum
    Replies: 20
    Last Post: 11-27-2012, 11:20 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •