Small Room Acoustics: Traps and Frequency Response - Part Three

[@drampadreg1386]

After making a large number of room mode calculations with a pencil and calculator, (twice the length divided into sound in ft/sec with multiples to 350Hz) your free calculator will be a life saver, and pencil saver. I wish I found this earlier! By about 1000 sheets of paper earlier. Thank you again.

[@JHBrandt]

Thank you, sir! YOU are the reason I put these resources up. ;)

[@soundslikejeremy]

Great series! How is the angle/spacing/amount of the waveguides determined?

[@TheMartinolsson]

Hi John! I have a project I have been wanting to do for a few years now and finally thought (as I finally graduated from the university and am going to now make some money) that I'd get to it. Ok so the project is a rehearsal room which I also use as a recording space for everything from live drums to singing. The room sound is hideous and I want to do something about it. I have a background in building so DIY really is what I had in mind. The room is about 4x7x2,3 m (not the exact measurements) rectangular, and the walls are plastered brick walls. One of the 7m walls is gypsum and the other is covered with some sound absorption panel (perhaps 2cm thick). The door is one one of the 4m walls and on the other there is a large window (about 1,5x1,5m). As you probably can imagine there is quite a lot of flutter echo and modes which make the room close to unusable. Do you have any thoughts that could help me make the room better, not worse? Martin

[@JHBrandt]

Martin, Sorry for the late response. Contact me thru my email on my site and I'll give you my Skype and other details. Let's talk. Cheers!

[@sundamusik]

great channel you've got sir, nice batik blouse love it. bless

[@JHBrandt]

Thank You. :)

[@sundamusik]

im now checking out your interview with warren from produce like a pro. heard you're living in my home country indonesia, hope i can move back one day. salam kenalan ya.

[@saadulislam1]

great video. My room is way to small to install traps deeper than 4". Do you think using 4" very rigid rock wool board with a 1 " air gap work for low frequency trapping? I live in Bangladesh, and we don't have many different material option.

[@matthewhalliday8193]

Hello how are you. What should I do in a living room for just listening to our hifi and tv.

[@JHBrandt]

It depends on how serious an audiophile you are. 😉 For any non-critical application - never let untreated surfaces face each other... And a listening room or cinema room must be symmetrical left to right.

[@its-kapucha]

So what does it really mean small room for control room. Is room with 30 cubic meters small? Are there some tresholds (in cubic meters)? Is it reasonable to invest in membrane solutions in it or not to control low frequencies? My walls are made from bricks.

[@michaelcurtis7376]

Hey, John! Fantastic stuff. I think you mentioned in a comment on a different video that beyond 4in thick that porous absorbers become reflective, but you often use 8in of trapping, like what's found in the first video of this series. Am I missing something? Thanks!

[@JHBrandt]

Yes, the RIGID, high-density stuff becomes increasingly reflective as thickness/depth increases. THEREFORE, use less-dense fiberglass for deeper traps. We have broadband trap designs as deep as 24". Above 16" even the lightweight fiberglass shows reflectivity, so we use an air gapping technique.

[@michaelcurtis7376]

Makes total sense. Thank you for the clarification!

[@jesperzeng8998]

Hi Mr Brandt, you' ve mentioned wave guides in this video. I assume that it is similar to Mr John Sayers's bass hanger am I right? Basically it's insulation wrapped around a homasote board? And also is there any mathematics formula to calculate the absorption coefficient for this? Thank you very much! Jesper

[@JHBrandt]

Jesper, It's not homasote board.. Homasote cannot 'guide' anything but higher frequencies.. kinda like using seaweed for wave-breaks near a beach. We use heavy 3/4" or 18 mm MDF wrapped with 2 - 3 1/2" of fiberglass insulation.

[@jesperzeng]

Thank you for the reply Sir! Since its 18mm MDF, I roughly get the idea. I would assumed that these wave guides instead of hanging loosely like Mr John Sayers' bass hangers, they would be locked rigidly within the acoustical treatment in itself? And how it works is to guide the waves through multiple reflections within the itself and lose the energy via the insulation? And I would assume it is a trade secret which you can't reveal the calculation? Thank you very much Sir! I really love your designs by the way! =)

[@CzarPharo]

how deep is this bass trap representation? what materials is that in there? Rigid fiberglass? Fluffy stuff?

[@JHBrandt]

The depths of the traps are dependent on the original room analysis (based on dimensions and mass properties of the partitions). That very deep trap shown is 16 - 18 inches deep.

[@CzarPharo]

Ok. If I was looking to do a 24" trap. what would I do with extra 6" inches? Another wave guide, air gap, Fiberglass?

[@JHBrandt]

@@CzarPharo why would you do that?

[@CzarPharo]

I was under the impression that if Im in a gypsum board room, that the deeper the broadband traps the better for controlling lower frequencies. Im I wrong?

[@CzarPharo]

I'm in a 19ft by 16ft rectangular room with 8.8ft ceilings that meet bonello. i built 7 6inch traps using the materials you suggest to treat the ceiling. And I've built a 3 8 inch traps using the diagrams on your website with the waveguides that I was intending to use on the front wall behind the monitors. Those were pretty difficult to build for me, I didn't want to build anymore of those and I was thinking of building 2 24 inch traps in for the backwall with the diffuser in between. I wanted to control lower frequencies as much as I could, so I figured the deeper the better. And I'm thinking the deeper traps would be easier to build than those 8 inches were. These were the last 2 traps I was looking to make due to budget, and time. From there forth I was looking to start hanging, moving in equipment and testing the room. I wish I had the diagram for those deeper traps ; ) . What would be your suggestion?

[@boothamilton9850]

John - I think I know why your room sounds dead - possessing absolutely no clarity in the mids and highs. That speaker over your right shoulder has it's midrange and tweeter missing! Replace them and I guarantee the sound in your room will become as bright as I am. Cheers.

[@JHBrandt]

LOL! You have a very good point there! facepalm. By the way, I've moved my new speaker system downstairs where it is now complete and we only need to finish the amp assembly and test. I look forward to showing you guys what we're doing there. :D