DIY Flat Panel Speaker Love

[bradley.s]

Because Don Keele said flat CBTs work and researches said MAP arrays work. That's pretty much the only reason other than DMLs have the characteristics you mentioned.

[Unbiasedsound]

Because Don Keele said flat CBTs work and researches said MAP arrays work. That's pretty much the only reason other than DMLs have the characteristics you mentioned.

How are your CBT panels coming along?

[bradley.s]

I've been going back and forth on how to support the array. Finally decided on wood railing over aluminum angle. I'm soaking the wood in mineral oil to deaden it a little.

[Unbiasedsound]

Woooaaa that is a lot of exciters for one panel, 24? My Bastat panels that use a single 19mm exciter can fill my 10ft.X12ft. room with adequate spl levels.

[bradley.s]

Twelve actuators per array. The CBT24K has twenty four per array. The goal is a sound field not loudness. It is a sixty inch array so I could meet the 170mm center to center spacing used in the 2010 wave field synthesis paper with nine actuators. I used twelve actuators because it matches Don Keele's transducer ratio in his arrays. Hopefully, a MAP CBT array can be created using fewer actuators.

[Unbiasedsound]

Sound field? Is that like sound stage?

[RobertOrosco]

I'm shooting from the hip on that issue. I'm hoping my low volume level listening requirements will mitigate the majority of the problem. I'm also going to lean heavily on DSP. All the research I've personally seen investigates homogeneous single layers like a single sheet of aluminum or they use foam sandwiched with paper. The panels I'm going to try are hacked together. I have no idea what the internal dampening is on these things. It's a crap shoot. In addition, my geometry is also way off. I'm using very narrow panels relative to typical DMLs. With regard to normal DMLs, mine are a freaking mess.

What I'm hoping to accomplish is a CBT polar response in the 500hz to 6,000hz frequency range. CBT seems easy to handle below 500hz and hard to do above 6,000hz. If I can get the bulk of the frequencies working I can build a separate DML to handle below 500 and either forget about frequencies above 6,000 or try to figure out an alternative.

I think everybody had a deal with this problem

[bradley.s]

Sound field? Is that like sound stage?

No. Just control over the sound dispersion. Floyd Toole and Earl Geddes use different sound field controls (waveguides in Geddes' case, speaker position in Toole's) to create the illusion of a sound stage. A siren might create an omnidirectional sound field to alert everyone in all directions. The problem most of us deal with in this forum is sound field control in small rooms, our homes. We have to deal with reflections and physically long low frequency waves. Pro audio guys would deal with different problems because they might be in large rooms like auditoriums.

Imaging and sound stage illusion rely on how you control the sound field.

[Unbiasedsound]

No. Just control over the sound dispersion. Floyd Toole and Earl Geddes use different sound field controls (waveguides in Geddes' case, speaker position in Toole's) to create the illusion of a sound stage. A siren might create an omnidirectional sound field to alert everyone in all directions. The problem most of us deal with in this forum is sound field control in small rooms, our homes. We have to deal with reflections and physically long low frequency waves. Pro audio guys would deal with different problems because they might be in large rooms like auditoriums.

Imaging and sound stage illusion rely on how you control the sound field.

So control over the sound dispersion to create a type of sound stage? DML's (no matter how many exciters are used per panel) already have a huge/wide soundstage. DML's from what Ive read already have less room reflections then conventional cone speakers. Are you saying that using multiple exciters per panel will have a wider or better soundstage then using a single exciter? Or are you saying that multiple exciters will have less room reflections then just a single exciter? I cant speak for anyone else but when I want to deal with room reflections I use acoustical treatments like bass traps, diffusers , isolation pads etc etc.

In the Maps article the only thing I agree about it is using some dampening properties....What I disagree with is that more exciters don't mean less room reflections.

[geosand]

Not sure if this has been posted before.
An attempt to create a bass DML, 40hz. They are seemingly successful to some degree and it seems to use techniques that have been discussed here before: https://web.wpi.edu/Pubs/E-project/A...er_Stabile.pdf and its relatively easy to read and understand...

[Kornbread]

Nice find geosand and bonus points for ease of comprehension.

This one sentence tells me what I need to know about multiple exciters vs one exciter per panel as NXT is probably the best known contributor to distributed mode loudspeaker technology. They had big plans for its implementation. "This technology, developed by now dissolved company NXT, involved placing surface exciters in positions along a panel that correspond with that panels resonant frequency" (Zielinski, Obiora, & Sansoucy, 2018).

Ok, these guys read my experiment with the panels. The wood frame holding the panel in with the aid of window seal foam ... where's my name in the reference section?


Reference

Zielinski, D., Obiora, O., & Sansoucy, D. (2018, April 25). Development of a Resonant Panel Speaker[PDF]. Worcester Polytechnic Institute.

[Unbiasedsound]

Not sure if this has been posted before.
An attempt to create a bass DML, 40hz. They are seemingly successful to some degree and it seems to use techniques that have been discussed here before: https://web.wpi.edu/Pubs/E-project/A...er_Stabile.pdf and its relatively easy to read and understand...

I skimmed through that article and if I am not mistaken they don't use a Spline/brace to hold and stabilize the exciter in place which is a very important factor especially in the lower frequencies at higher excursions where the movement becomes more pistonic then modal it will need something to push off of like a spline or brace.

[Unbiasedsound]

Nice find geosand and bonus points for ease of comprehension.

This one sentence tells me what I need to know about multiple exciters vs one exciter per panel as NXT is probably the best known contributor to distributed mode loudspeaker technology. They had big plans for its implementation. "This technology, developed by now dissolved company NXT, involved placing surface exciters in positions along a panel that correspond with that panels resonant frequency" (Zielinski, Obiora, & Sansoucy, 2018).

Ok, these guys read my experiment with the panels. The wood frame holding the panel in with the aid of window seal foam ... where's my name in the reference section?


Reference

Zielinski, D., Obiora, O., & Sansoucy, D. (2018, April 25). Development of a Resonant Panel Speaker[PDF]. Worcester Polytechnic Institute.

These sentences tells me what I need to know about that articles main goals. Which is more about Aesthetics and not hi fidelity sound quality.

This report covers the development of a walled mounted, low-profile speaker system. A format that
could be hung from a wall in a way similar to a painting, and the capability to hit low notes. While a small number of speaker manufacturers have created dimensionally impressive
models, they are almost all very expensive or have limited frequency ranges, leaving a gap in the
sector for more affordable speakers that can achieve an ideal range.

You really believe the works he CITED are the only places his knowledge came from?.....I wouldnt doubt for a second that he read this thread or any other thread on any other forum pertaining to DML technology...most wont cite a forum because its not a scientifically based study but credit should be given where its due. If 5 years from now another scientific study on DML's comes out and they mention the Karsonator technique you will all know he got that technique from me. LMAO


Now like I always ask of those articles is where are there DML panels? Who has heard them? Who has built them? What have they been compared to?

[bradley.s]

DML's from what Ive read already have less room reflections then conventional cone speakers.

No. This is how it works.

https://www.youtube.com/watch?v=tWZdPkH9IgA

[Unbiasedsound]

No. This is how it works.

https://www.youtube.com/watch?v=tWZdPkH9IgA

That video technically supports what I said SMDH....DML's have a very diffused sound the echo reflections are less prominent then with conventional cone speakers therefore the reflections are less directional.

This is one of the reasons DML's have very little to no microphone feedback.