DIY Flat Panel Speaker Love

[Unbiasedsound]

First post to this forum, apologies if I get things wrong.

i have a need to place audio monitors in a setting that is extremely space constrained, and think the flat panel approach could be really helpful, ie a monitor that is <3 inches thick. However, it seems there is no easy way of making the flat panel ‘one sided’ so that the volume on one side is loud, the other side quiet. I think I know the answer, that there isn’t an easy way to do this but thought I would throw the question out to this group - is it possible to build some sort of thin enclosure / baffle on the “back” of the panel to stop sound going in that direction?

thanks for any insights.

Yes its possible to build a sealed enclosure on the back just like a conventional cone boxed speaker. I would make a 1inchX2inch frame and just cover the back with a thin (1/4-1/8) piece of wood.

[NW Sailor]

First post to this forum, apologies if I get things wrong.

i have a need to place audio monitors in a setting that is extremely space constrained, and think the flat panel approach could be really helpful, ie a monitor that is <3 inches thick. However, it seems there is no easy way of making the flat panel ‘one sided’ so that the volume on one side is loud, the other side quiet. I think I know the answer, that there isn’t an easy way to do this but thought I would throw the question out to this group - is it possible to build some sort of thin enclosure / baffle on the “back” of the panel to stop sound going in that direction?

thanks for any insights.

[mhester]

I saw the Tech Ingredients vid a year or so ago and have wanted to experiment with this at some point (need to finish my Classix 2.5's first...) This is a very long thread and I'm not sure if you've previously posted your sub design. Can you kindly share that (again?)

[Unbiasedsound]

During this covid time (3 months 7 days a week 2-4 hrs a day lol) I've been experimenting with many different placements of the exciters including the use of 2 exciters per panel. What I have found is that the 2/5-3/5 rule of exciter placement is bogus. Not sure who first thought of those placements as the standard (NXT?) but it seems P.E. guide and T.I. youtube vid like to use those placements.

Most just blindly follow those standard placements instead of experimenting for themselves as most cant think outside the box. lol

[Unbiasedsound]

Another thing that is great about DML's is that you can custom tune your panels to your preference. You can make them sound bright, dark, forward sounding laid back sounding its all based on how one tunes there panel as the combinations are endless. One can even change the soundstage and imaging of a panel. These tuning changes can be done in as little as 30 seconds per speaker with very little cost and no tools required.

With conventional cone drivers the usual way to change the sound is to change the crossover and even then its very limited and time consuming, not to mention all the costly tools and parts needed to do so.

[Unbiasedsound]

It seems some people (on the other forum) dont understand about DML's and bass. Besides having very limited pistonic motion exciters are also not efficient in the bass region. When running full range a exciters mid to high frequencies efficiency will be way higher then the bass which will over power and drown out the bass frequencies. The way to fix it is to use the exciter as sub to only produce the low frequencies 100hz and below. A sub amp is needed as it will push the exciter to produce pistonic motion but wont have the higher frequencies to drown out the lower frequencies.


My DML sat/sub combo is my top preferred design as it has great high frequencies and well as the low frequencies down to 40hz.

[Unbiasedsound]

A controlled and predictable speaker cone is significantly more accurate than a random piece of wood/plastic/composite material vibrating. Isn’t the goal of speakers to accurately reproduce recordings?

Instruments are vibrating material. Whats more accurate then a panel vibrating like a instrument.

[Unbiasedsound]

DML's are great for mid to high frequencies as they are basically full range speakers being able to play from 60hz-20khz. Of course its all design dependent as the better the design the better they will sound. The low frequencies are not as good due to the limited pistonic excursion. Conventional cone drivers move more air to produce bass while DML's vibrate the panel (less air movement) which is why a larger sized panel is needed to produce lower frequencies because it needs to bend the panels hence the term bending wave transducers. EPS needs to be thin (5-10mm) 1/2-1/4 inch to flex enough to produce adequate bass. T.I. video uses 1inch XPS which is to thick. Also EPS is more flexible then XPS.

There are two types of damping. One is panel treatment damping usually done with a 50/50 water/glue mixture or even paint water based or oil based. The other type of damping is done with some type of foam damping material in which this is used to "TUNE" a panel to smooth out its frequency response. It can be applied directly on to the panel and or on to the panel frame. Shelly Katz Podium speakers gave me the idea to use this technique and it works. http://www.stereomojo.com/Podium%20....akerReview.htm

One of the best "ACCURATE", sounding DML's speakers are from a Russian company called Sheet Control.> https://www.youtube.com/watch?v=JheZ84QcZPw

https://www.youtube.com/watch?v=vBXQyR1EwSs

https://www.youtube.com/watch?v=PLweDrL4EDc

https://www.youtube.com/watch?v=MsEg7RjunhQ&t=96s This video compares DML to Dynaudio.

[viewcart]

While I love his YouTube channel, those speakers are going to be a complete mess for HF reproduction, and forget LF all together. For midrange they WILL work, but to get a smooth output the thing needs to be so damped you may as well forget any efficiency advantage from a radiator of that size. He states that these produce sound the same way a piano soundboard does, which IS true, but he goes on to say traditional cone speakers produce sound “artificially” while wooden resonances are “natural.” Sorry, sound is vibrating air and that’s it. It really doesn’t matter what makes it vibrate. A controlled and predictable speaker cone is significantly more accurate than a random piece of wood/plastic/composite material vibrating. Isn’t the goal of speakers to accurately reproduce recordings?

[Unbiasedsound]

What is the best shape for DML panels? Best most accurate shape is a square as it produces the most even sound because its shape is even. Next best shape is a rectangle but there is a limit to how long you can make it. A rectangles length should only be at most 8 inches greater then its width, preferably 5-6inches is ideal. The longer the rectangle the more exaggerated the sound becomes and it also becomes more uneven and weird sounding. This is the reason odd shape conventional cone speakers like 6X9's are not readily used in home speakers as the odd uneven shape makes the sound uneven and off sounding. Its no different for DML panels.

Once the corners are rounded though they are more of a hexagon shape.

[Unbiasedsound]

What is the proper or ideal exciter placement on a panel? When you look at P.E. exciter placement they use the 2/5 3/5 placement to off set the build up of standing waves. You can read up on there reasoning for using those placements in the P.E. buyers guide to exciters.

IMO those are not ideal placements. The ideal placement when using a single exciter per panel is dab smack in the middle/center of the panel. Has anyone ever seen a conventional cone driver with its voice coil off center from the diaphragm? NO right? DML's are similar to conventional cone drivers then most people realize as we are not trying to reinvent the wheel here. When any transducer is off center it will be less coherent. The most coherent sound is when the transducer is placed smack dab in the middle/center of the panel diaphragm.

[Unbiasedsound]

What is the right size panel? What is the right sized exciter? Smaller exciters can be used on smaller panels while larger exciter can be used on larger panels. Also when using more then one exciter per panel you can increase panel size.

Size's of exciters and recommended approximate panel sizes when used with a single exciter per panel.

9mm exciter.=8inch width panel square. if using a rectangle you can add more inches to length but width should be minimum 8 inches.

13mm exciter=10inch width. If using rectangle can add more inches to length but width should be minimum 10inches.

19mmexciter=14inch width. same as above

25mmexciter-16inch. width. same as above

30-32mmexciter-20-24inches width. same as above.

Also all the info given out is pertaining to high grade Expanded Polystyrene 1/2 inch (10mm) thick panels. Different materials will have different results.

[Unbiasedsound]

What is the best shape for DML panels? Best most accurate shape is a square as it produces the most even sound because its shape is even. Next best shape is a rectangle but there is a limit to how long you can make it. A rectangles length should only be at most 8 inches greater then its width, preferably 5-6inches is ideal. The longer the rectangle the more exaggerated the sound becomes and it also becomes more uneven and weird sounding. This is the reason odd shape conventional cone speakers like 6X9's are not readily used in home speakers as the odd uneven shape makes the sound uneven and off sounding. Its no different for DML panels.

[Unbiasedsound]

Ever since Tech ingredients vid on youtube a lot of people are hanging there panels to high. DML's do best closest to the ground. Why because like any conventional cone speaker ideal height placement is usually around ear level. DML's also have a very wide dispersion so if your panels are too tall and or placed to high the high frequencies will go over your head. Below ear level is best.

[Unbiasedsound]

I found out something new. When using a sub I have found that using the 180 degree phase switch blends well with DML panels. As to why it could be that DML panels are slightly out of phase.