DIY Flat Panel Speaker Love

[LOUT]

I think I realized some of my mistakes (because I'm socially inept) in my responses above.
While I was talking about different ways to deal with echos and feedback, you took the time to find a video specifically showing a pretty worst-case scenerio for feedback with a BMR speaker performing well.
Instead of acknowledging the work and attention to detail you paid to find that example, I focused on explaining and complaining.
This was likely pretty offensive, and I didn't mean to offend you, so I apologize.

[LOUT]

Looking at the large Tectonic DML measured specs, it looks like it can reach peaks up to ~120db with a +/-5db response from 100hz to 2-3khz according to their heat chart.
The response above 2-3khz for these larger DMLs gets...weird. But the power-response (and I think the listening-window response) might still be fine, so I'm not sure how audible those quirks really are for most listeners.
Still, 2-3Khz is a lot easier to reach with a compression driver at full power compared to trying to crossover at 1-1.5khz to a pistonic midwoofer large enough to reach ~120db (I think 8"-10"diameter).

I also enjoyed this largely positive video review of a 3way using a BMR midwoofer:
https://www.youtube.com/watch?v=7JZjb293HVo

[LOUT]

I think the DML/BMR pattern-based-radiation allows them to achieve an interesting work-around for the usual limits of diameter VS high-frequency-dispersion that conventional pistonic drivers have.

There are caveats where the BMR's mids/highs produced this way exhibit what appears to be something like comb-filtering, but this is generally not enough to show after 1/3octave smoothing which I think means the response should sound smooth to most listeners.

BMRs have been said to suffer less from destructive frequency cancellation from reflective surfaces compared to conventional pistonic drivers. I'm guessing this may be a result of their comb-filter-resembling mid/high response, potentially making it less likely for coinciding frequencies to phase-cancel with their own reflections..?
HOWEVER, frequency response changes from room modes and reflections/cancellations are only one aspect of dealing with reflected sound.
Reflected sound with longer distance differences between the driver and surface still produces an audible delay between source and reflection arriving at the listener. This delayed sound can be very distracting, and it's not something that BMRs are said to handle any differently than conventional pistonic drivers (at least as far as I've read at this point).

I think it's important that these two aspects of room reflections aren't confused with eachother.



The unique advantage I've seen for the BMR is its impressively wide mid/high-frequency dispersion at larger sizes.
I think this BMR advantage should allow a larger-than-typical midwoofer (and the higher SPL ceiling that presumably grants) to more easily reach appropriate frequencies to join a similarly highSPL tweeter or maybe even cover both mid+tweeter duty itself if the high-frequency response is good enough for the application.
Cool stuff!

[LOUT]

Not sure its worth responding since you are going to doubt everything I've said or posted including actual videos in which you make outlandish assumptions like was the speaker in the frame the one being used at the time. REALLY??? It seems you just want to argue instead of trying to understand how DML's BMR's work.

This is why I dont like to give out the answers directly....Instead I will just ask the questions to make people think for themselves and maybe give a few hints along the way. LOL

I'm not doubting YOU and I'm not doubting BMRs, I'm just doubting some of the marketing that comes from TT promotional videos....and complaining about a lack of important information in them.
I've seen other major companies use some sneaky methods to exaggerate what their product can do, even when their product is genuinely great and should be able to stand well on its own merits.

I'd love to know what advantages and disadvantages BMRs can have, and why.
Like I said, I'd particularly love information from any unbiased 3rd Party who has experience with these that they can share.
That means YOU and others like you who can talk candidly (frankly?) about stuff like this.
What have YOU experienced, and what have YOU learned when comparing your BMRs/DMLs beside conventional drivers?

Why do you think Tectonic decided to use panels with corners for some of their designs (like the speaker in the latest link you shared)?

[Unbiasedsound]

Not sure its worth responding since you are going to doubt everything I've said or posted including actual videos in which you make outlandish assumptions like was the speaker in the frame the one being used at the time. REALLY??? It seems you just want to argue instead of trying to understand how DML's BMR's work.

This is why I dont like to give out the answers directly....Instead I will just ask the questions to make people think for themselves and maybe give a few hints along the way. LOL

[LOUT]

The Tectonic folks said that speaker (or at least all the similar ones I could find so far) has 165degree dispersion, so not a controlled-dispersion array.
However they also said it doesn't reflect off walls or any hard surfaces despite their own examples clearly showing it does...so I'm feeling pretty suspicious of their claims, and don't know which (if any) can be believed. Maybe it was just a particular person or persons who got a little drunk on their own hyperbole, but a lot of the same people are in many of the videos...and seeing one of their representatives either make a gross error in wording or seemingly lie through their teeth...that erodes trust pretty fast.

Can anyone tell me why the corners of a DML panel need to be rounded?

It looks like Tectonic might disagree in some situations, at least with their larger DML10/DML500 models.
Why do you think they need to be rounded, and can you think of any pros/cons that might explain why TT decided to use sharp corners in these designs?
Are there some advantages to keeping corners, and are the cons potentially situational where they might sometimes be worth the tradeoff?

[LOUT]

https://www.youtube.com/watch?v=_KI5NJCqnPc.

If that's the only speaker delivering to the audience, the back row is going to get a much weaker level compared to the poor, abused top-of-singer's-head.
It's hard to draw any conclusions when there's no A/B comparison (or comparison of any kind) to draw any conclusions from. The SPL from that speaker isn't mentioned. The rest of the speakers being used (if any) aren't mentioned. I don't think they even said whether or not the speaker in-frame was the one being used at the time. :(

A conventional driver monitor with decent EQ from the desk to avoid problem frequencies and a sensible SPL (both to avoid feedback and to avoid deafening the singer) should also be able to accomplish this.
A conventional array might have better luck by narrowing the vertical dispersion to avoid blasting the singer and the ceiling...focusing more audio onto the audience, further avoiding feedback, and lessening the amount of floor/ceiling-echo.

I don't know if that particular TT speaker being shown is a focused array type (I suspect it is) or a wide-dispersion type. I'll try to take a look at their website in hopes of finding some information on the different models and their patterns.

Some of the TT BMRs (maybe all?) have really lumpy mid/high response that looks like comb-filtering. This levels out under 1/3oct smoothing which they use in many of their graphs, but it might help against feedback if the mic/speaker are positioned where there's a null in the worst problem frequency/ies for the mic. This would kind of be a specialized advantage of the BMR that would take a pretty niche design to attempt using conventional drivers...though it's also pretty finicky either way and would require a very careful mic-handler. A neat trick, if possible, but not practical.
I'm not sure what other things the BMR driver itself could do that would give it any advantage against mic feedback in that position. I'm going to try and look into this a little more.

[Unbiasedsound]

https://www.youtube.com/watch?v=_KI5NJCqnPc

[LOUT]

I first heard about it from reading Dr.Jose Bertagni's articles and patents.
Answer: It has to do with reflections. DML's have a "DIFFUSED" sound. Diffused sound equals less reflections and or WEAKER reflections. Less reflections equals more coherency. In a highly reverberant space there will still be an echo but due to less reflections cancelling each other out the sound will be more intelligible.

Also its been stated that because these diffused type of reflections dont cancel each other out as much as a conventional cone driver, instead what they do is reinforce and use the reflections to there advantage. Bertagni states in one of his articles or patents that his speaker uses the rear wall reflections to increase performance of his loudspeakers due to its diffused nature.

A diffused type of sound with weaker reflections will also have way less microphone feed back which is why you can place a DML panel right in back of the mic. as shown in Tectonic video.

A well-diffused sound can easily result more/stronger/worse reflections against lateral surfaces.
Echos cancelling or reinforcing the original source will depend on the location of the surface and source and listener (and the frequency/ies themselves, I think) so depending on this can be finicky for any source...and may still result in slight "ringing" or sloppy sound.

I think the more important aspects for coherency in a gym or auditorium or tunnel will be:
-the echo's volume relative to the source (which is largely controlled by the listeners' distance from source..narrowing dispersion can help avoid the worst reflection locations where possible)
-the echo's pre-delay time (which depends on the distance and angle of source/surface/listener, which can be controlled by careful placement of sources and narrowing/limiting source diffusion)
-the echo's trail length and frequency-response (pretty sure this can only be controlled by room treatment...though careful pattern control can use the audience as "room treatment", lol).

The extremely diffused sound can be great help for a situation where there will be several quieter sources spread around near listeners to maximize direct-source volume over reflection volume, but any decent 2way/3way or appropriately small single FullRange conventional driver can be designed to do this as well.


I don't believe a BMR with wider diffusion compared to a conventional cone array at the same listening-distance SPL and same frequency-response will result in less microphone feedback.
But you can minimize feedback with either speaker type by being aware of the microphone and speaker diffusion/pickup pattern and by using the mixing board's equalizer to tame problematic frequencies...so the video might've simply been making good use of conventional means.

A wide-diffusion onstage PA without additional audience-only/primary reinforcement PA will mostly result in the stage/players getting blasted by more SPL than the middle and back rows of the audience. A bad situation, even with BMRs.
A wide-diffusion stage-monitor PLUS additional audience-facing PA will have the monitors facing the stage toward the mic dead-zone, and audience PA would be forward or high, also in the mic deadzone...so neither is causing microphone feedback because of their location/facing/controlled-diffusion-pattern. Easily accomplished with either technology.
A controlled-diffusion array can probably be tuned to do a decent job at both stage and audience coverage from onstage while avoiding feedback...but this can be accomplished with either technology.

I'm likely missing some important benefits somewhere, however.
I'm sure the BMRs can do some really cool things, and I'd love to hear some pros/cons from anyone experienced with large, indoor live-sound (preferably an objective 3rdParty instead of a salesman/installer/customer, if possible).

[Unbiasedsound]

Actually the answer is really simple, so simple in fact you might not believe it. lol I think I did mention it someone here or on another site. I first heard about it from reading Dr.Jose Bertagni's articles and patents. I forget which one and they are so long so dont ask me to find it. LOL Even Tectonic mentions it but uses high tech terminology so its harder to understand. lol

Answer: It has to do with reflections. DML's have a "DIFFUSED" sound. Diffused sound equals less reflections and or WEAKER reflections. Less reflections equals more coherency. In a highly reverberant space there will still be an echo but due to less reflections cancelling each other out the sound will be more intelligible. The only way to significantly cancel out reflections to the point of very little echo is to use room acoustic treatments.

Also its been stated that because these diffused type of reflections dont cancel each other out as much as a conventional cone driver, instead what they do is reinforce and use the reflections to there advantage. Bertagni states in one of his articles or patents that his speaker uses the rear wall reflections to increase performance of his loudspeakers due to its diffused nature.

So one of my advice for DML speakers is " DO NOT USE ACOUSTIC TREATMENT ON THE REAR WALLS" behind the panels like how Tech Ingredients says in his video and or in the comment section.

This is actually the so called "MAGIC" sound of DML's as it sounds like a live show.

A diffused type of sound with weaker reflections will also have way less microphone feed back which is why you can place a DML panel right in back of the mic. as shown in Tectonic video.

[Unbiasedsound]

Oh ok I just wanted to be sure as I thought maybe I missed something in the video that you found. lol

[LOUT]

Digging through some BMR specs, it looks like they have impressive off-axis performance at pretty high frequencies for their diameter. Kind of like an RS75 for half the price...though that might also be a brandVSprice thing.
Their high-frequency coverage and LF-output isn't quite enough that I'd want to completely omit a tweeter and woofer, and it looks like some manufacturers agree, so I'm not sure there's much remaining advantage...at least not for hifi.
Obviously there's a nice advantage for affordable lofi singleFRdriver PA though.

Looking at some of the other BMR (advertisement?) videos, it seems many of the other videos are somewhat ironically focusing less on the single-fullrange and wide HF coverage aspects and instead showing examples where large/tall rooms with multiple wall speakers were replaced with line-array type systems to avoid some of the surface bounces.
It's not something exclusive to BMRs nor the TT brand, so it's a little odd that the technology and brand is the focus rather than the better setup.

Maybe there's a cool advantage, directly tied to the BMR technology, that they're forgetting to mention or show in the videos?

[LOUT]

What causes conventional cone speakers to sound unintelligible in that underground railway station? Answering this question will give one a hint as to why DML/BMRS are more intelligible.

In that video/example, it appears the conventional drivers were spaced farther apart and the recording was taken from a more distant location while the BMR replacements were spaced much more frequently, allowing each to play at a lower level while keeping a more balanced/constant output volume for listeners. This also results in the microphone being noticeably closer to the nearest source.
You can still hear a lot of echo, so the BMR doesn't seem to help that, but getting the mic/listener closer to the source allows more of what's heard to be direct-VS-reflected.

In this example, I'm unsure if the BMR had an advantage in size/shape/price to allow this, or if it wasn't so much an advantage of the chosen BMRs as much as simply a better plan for the retrofit.

It would be interesting to hear a comparison against conventional fullrange drivers (properly EQed for low distortion) with similar output and spacing.

So are you just assuming what you think they did or is it actually what they did? Like the recording being taken from a ore distant location and or the conventional drivers being spaced further apart etc.?

I only meant it "appeared" that way, because they failed to describe the older situation at all and didn't give a microphone position for either situation. I probably could've been clearer about that, but it sounds like you're already aware of the video's lack of information.
There's also a large volume difference between the examples, likely indicating the microphone was significantly farther from the source in the quieter example.
Did they share more details somewhere else?

Alternatively, do you have any other examples or maybe a more direct comparison under your own experience you can comment on?
Or is there an experiment folks can try "at home" to experience the differences you'd like to show?

If I have to drag a small amp and a small DML and small FR-cone-driver into an echo-y bathroom, I'm totally willing lol.

[Unbiasedsound]

So are you just assuming what you think they did or is it actually what they did? Like the recording being taken from a ore distant location and or the conventional drivers being spaced further apart etc.?

[LOUT]

In that video/example, it appears the conventional drivers were spaced farther apart and the recording was taken from a more distant location while the BMR replacements were spaced much more frequently, allowing each to play at a lower level while keeping a more balanced/constant output volume for listeners. This also results in the microphone being noticeably closer to the nearest source.
You can still hear a lot of echo, so the BMR doesn't seem to help that, but getting the mic/listener closer to the source allows more of what's heard to be direct-VS-reflected.

In this example, I'm unsure if the BMR had an advantage in size/shape/price to allow this, or if it wasn't so much an advantage of the chosen BMRs as much as simply a better plan for the retrofit.

It would be interesting to hear a comparison against conventional fullrange drivers (properly EQed for low distortion) with similar output and spacing.