DIY Flat Panel Speaker Love

[Unbiasedsound]

These are my higher end DML panels playing. DML - YouTube

[Unbiasedsound]

No, but I have used something similar from Lowes called coroplast. I didnt care for it. If you do decide to try that carbon core I would suggest the 6mm thickness.

[robstivers]

Ok... I've been going down the rabbit hole here and on diyaudio trying to glean all the info I can about how to pull off a successful build. I was going to start with 1/2 inch formular xps panels, but then I stumbled across another material that's reasonable in cost and looks like it might be promising. Does anyone have any experience with this material? https://www.carbon-core.com/product/...eycomb-sheets/

[Unbiasedsound]

What DML material are you referring to, EPS, XPS, Wood, Canvas, Card board, Paper, Plexi glass, honey comb composite, other? Even conventional cone driver materials are not the same, some have heavier/thicker diaphragms and some have very thin/light diaphragms some have more damping properties and some have less while some are aluminum, paper, ceramic , Kevlar, ribbon, poly etc...but they all basically work the same just like DML/BMRs.

A DML is just a exciter attached to a diaphragm while a BMR is like a exciter but has a basket holding the magnet in place while the diaphragm is supported by some type of surround material just like a conventional cone driver. My DML design mimics a BMR driver as it has a spine to hold the exciters magnet in place while the foam surround supports the diaphragm that is attached to the frame.

This technology has been around since the 50's or earlier, its not new. To many people are over analyzing and or thinking that these DML/BMR drivers work differently then conventional cone drivers but in fact they are more similar then not.

[zx82net]

Like I said before a good sounding DML panel is all design dependent as the better ones design the better the sound. If one knows how DML's actually work and function its easy to figure out how to tackle transient response. Its pretty similar to conventional cone full range drivers like Fostex, tang band, mark audio etc. Most of those drivers size are 8inchs and under because its all about physics. Even DML's have to abide by those laws if you want them to sound right. Most people who build DML start off with a 2ft. (pink) panel then go to 4ft. and then max 8ft. They dont even make 4ft. or 8ft conventional cone drivers and for good reason especially if using it as full range. This is why I stress smaller panel size as DML's are very similar to conventional cone drivers.

Also did you listen to my sound clip, and if so what are your thoughts?

Somehow, I'd missed the post with the clip before, browser didn't refresh or something. I've listened to it now, thank you for posting it. TBH, I don't put much faith in cell phone recordings. The treble sounds perhaps a bit smoothed over, but I'd rather attribute that to the recording, rather than blame the speaker.

As a physicist, I find it a bit frustrating when people say "it's all about the physics" without citing any physics. Fact is, the DML work I have seen documented on the internet has been methodical engineering trial and error, which is a perfectly valid mode of design, but it's not really science. There are similarities in operation between a speaker cone operating in heavy breakup and a DML, but the material is different, the radiator size is an order of magnitude different, and the radiator thickness is closer to 2 orders different. So, I don't think you think you can assume the performance is similar just because they both exhibit resonant modes. I'm not knocking DML's, I'm genuinely interested to see some deeper analysis of how they work.

[Unbiasedsound]

Like I said before a good sounding DML panel is all design dependent as the better ones design the better the sound. If one knows how DML's actually work and function its easy to figure out how to tackle transient response. Its pretty similar to conventional cone full range drivers like Fostex, tang band, mark audio etc. Most of those drivers size are 8inchs and under because its all about physics. Even DML's have to abide by those laws if you want them to sound right. Most people who build DML start off with a 2ft. (pink) panel then go to 4ft. and then max 8ft. They dont even make 4ft. or 8ft conventional cone drivers and for good reason especially if using it as full range. This is why I stress smaller panel size as DML's are very similar to conventional cone drivers.

Also did you listen to my sound clip, and if so what are your thoughts?

[zx82net]

No, I have not.

Blurred?

I've not heard good ones or seen transient response measurements, so I have no authority here. People make amazing claims for them, but transient response seems like it must be a challenge: The radiating area is very high, leading to low displacement (a very good thing), the total moving mass is enormous compared to a normal tweeter (a bad thing), and you have to deal with propagation delay across the surface of the panel (a bad thing). I wonder how these things bear out in practice. Since material properties of the favored panel materials are undocumented and variable, I doubt modeling helps much.

[Unbiasedsound]

When listening to my recording I noticed the treble is a bit hot but I tend to like it but if I want to I can easily reduce the treble. With conventional cone drivers usually the only way to change the frequency response is to change the crossover. With DML's you can use other techniques. I've mentioned before that Shelly Katz Podium speakers he uses damping on the spine in which you can tune your DML panels to your taste. I use the frost king foam cut into 1/2-1/4inch pieces placed on the spine. If you do not use a spine you can also place the foam piece directly on the back of the exciter magnet. You can also do it the conventional way by using a 0.05mh inductor and it will smooth out the treble.

[Unbiasedsound]

I made a recording of my small Sat.DML panel with powered (conventional cone) subwoofer playing. Yes I know the sub gain is to high as I had some larger panels hooked up and forgot to dial the sub back when hooking up these smaller DML panels before recording. Its recorded from my cell phone so the recording is not that great.

These small dml panels are my entry level design using a single exciter run full range without any crossover parts.

Sawna - YouTube

[Unbiasedsound]

No, I have not.

Blurred?

[zx82net]

Serious question, has anyone seen any real transient response metrics for DMR flat panels?

They have to be blurred by the speed of the transverse wave propagating across the panel, don't they?

[Eipromb]

If you can get at least 1ft. it will be good enough.

Are you planning on using a powered sub with the panels?

I'll be running something for the low end, though I haven't decided what yet. I have an unused DSP-408 lying around, so I'm thinking I could use that to run separate mid-woofers on each channel, or a single sub or both. The limiting factor is primarily the amount of space I have in the room.

[Unbiasedsound]

Haha this will be tough, it seems typical room sizes in the city where I live are barely larger than 4ft these days.

If you can get at least 1ft. it will be good enough.

Are you planning on using a powered sub with the panels?

[Unbiasedsound]

While I do plan to mount at roughly ear level, I’m curious about this. Is this general advice or something specific to DMLs? I thought one of the benefits of DMLs was their ability to sound well off axis. Ignoring floor/ceiling reflections (let’s pretend I’m sitting in an anechoic chamber), would DMLs perform better/ worse/ the same as a tradition cone that was close to the floor?

This is general advice but the reason I mention this is because I see to many people place there DML speakers way up high. Although DML's sound good off axis they sound better on axis like any other speaker. They would perform better then a traditional cone because of the diffused nature of there reflections meaning the reflections are not as prominent.

[Eipromb]

DML's should be a minimum of a foot away from the rear walls and ideal or optimum distance is around 2ft.-4ft. also depending on the size of the room.

Haha this will be tough, it seems typical room sizes in the city where I live are barely larger than 4ft these days.