Open baffle speaker design

[RayDunzl]

Amazing how well acourate is smoothing in the 100 - 1K range for the center listening position

It's a nice tool. Pretty much a click/measure/click/caclulate/click/load filter/done simplified version of full Acourate.

Digital feed to miniDSP OpenDRC-DI ($325) with AcourateDRC ($85) and digits continuing on to the DAC.

 

[Sal1950]

It's a nice tool. Pretty much a click/measure/click/caclulate/click/load filter/done simplified version of full Acourate.

Is that from a single position measurement or a multi averaged?

 

[RayDunzl]

Single position, three sweeps, left/right/left, some choices of calculation setting (aggressive or not, and how much of the miniDSP to use, draw a curve as desired).

I don't know why it doesn't do left/right/both (originally thought it did), with which it might try to correct the bass phase fault.

The rest of the room sounds no worse (to my deaf ears) for using the single measure.

Since the panels (and I would think, any stereo system) are best at the sweet spot already, I don't consider it a problem.

Old sample, with lots of smoothing applied to the measurement, flat "curve" to create.

 

[HammerSandwich]

Theoretically, "room gain" is simple.

Don, thank you for taking the time to describe this.

I'd hoped to use room gain to help people question the notion that boundary reflections invert phase. Obviously, sealed-room gain could not exist if this occurred.

Apologies for being so cryptic last time!

 

[HammerSandwich]

Flat panels over most of their frequency range (above the deep bass -- depends on panel/driver size) generate a figure-eight pattern in front and behind with little radiation to the sides or top and bottom.

That's the usual sales pitch/magazine copy, but I've seen a lot of evidence to contradict it. (Yes, yes - I'm sure everyone's just shocked to hear that the admen & reviewers aren't telling us the whole story... )

I note that you called flat panels here, so apologies for broadening my reply. Best I can see, the air doesn't really care much about what pressurizes it, so the usual acoustical properties still apply. At the very least, transducer size & baffle width have their effects and limit figure-eight behavior in many dipole speakers. Linkwitz's LX521 & John K's Nao Note have complicated baffles for a reason! John's Tech Studies are comprehensive and daunting; Figure 3 here gives an idea of how band-limited the effects are.

A few examples:

1. The entire 3D3A database! It's small but a treasure. Definitely see the Sanders ESL, which was measured both normally and with back-wave absorption. The frontal-hemisphere behavior doesn't seem to change significantly, though the charts begin at 500Hz.
2. Apogee Stage - The pattern widens above the 600Hz crossover, because the ribbon's narrow & baffle wide. 2-pi up to beaming, no?
3. AA Beethoven - Linkwitz did a great job with a rectangular baffle 25 years ago. Who has proper measurements of the LX521 to compare?
4. Jamo 907 - This one's really interesting, with a 5" mid running 250-2500Hz on a 17" baffle. Above baffle step, the frontal polars look just like similar TMs in boxes. Below ~500Hz, the mid transitions to 4-pi, & we see dipolar behavior that looks like the worst baffle step ever. Also, the rear wave causes the on-axis hole at 1kHz, doesn't it? I suspect a larger driver would average that out a bit, and it will depend on position, just like diffraction.

A lot of these speakers don't have much radiation around 90deg, however, this seems to be a dipole effect only at lower frequencies. The same effect occurs higher up but for totally different reasons, regardless of the type of driver. (I feel the typical subjective reviewer mistakes cause & effect here. Again...) Similar effects certainly can be produced by drivers in closed boxes, but we'll have to compare speakers with identical baffle widths & driver sizes, if we wish to isolate the dipolar behavior.

 

[Don Hills]

One example of phase in reflections is to take the case of a pressure wave travelling down a pipe. Consider what happens when the pulse reaches the end. If the end is blocked, the pressure increases and the pulse is reflected back in phase. If the end is open, the pressure decreases (the pulse expands out of the end). The reflected pulse is inverted (out of phase).

 

[DonH56]

That's the usual sales pitch/magazine copy, but I've seen a lot of evidence to contradict it. (Yes, yes - I'm sure everyone's just shocked to hear that the admen & reviewers aren't telling us the whole story... )

I note that you called flat panels here, so apologies for broadening my reply. Best I can see, the air doesn't really care much about what pressurizes it, so the usual acoustical properties still apply. At the very least, transducer size & baffle width have their effects and limit figure-eight behavior in many dipole speakers. Linkwitz's LX521 & John K's Nao Note have complicated baffles for a reason! John's Tech Studies are comprehensive and daunting; Figure 3 here gives an idea of how band-limited the effects are.

A few examples:

1. The entire 3D3A database! It's small but a treasure. Definitely see the Sanders ESL, which was measured both normally and with back-wave absorption. The frontal-hemisphere behavior doesn't seem to change significantly, though the charts begin at 500Hz.
2. Apogee Stage - The pattern widens above the 600Hz crossover, because the ribbon's narrow & baffle wide. 2-pi up to beaming, no?
3. AA Beethoven - Linkwitz did a great job with a rectangular baffle 25 years ago. Who has proper measurements of the LX521 to compare?
4. Jamo 907 - This one's really interesting, with a 5" mid running 250-2500Hz on a 17" baffle. Above baffle step, the frontal polars look just like similar TMs in boxes. Below ~500Hz, the mid transitions to 4-pi, & we see dipolar behavior that looks like the worst baffle step ever. Also, the rear wave causes the on-axis hole at 1kHz, doesn't it? I suspect a larger driver would average that out a bit, and it will depend on position, just like diffraction.

A lot of these speakers don't have much radiation around 90deg, however, this seems to be a dipole effect only at lower frequencies. The same effect occurs higher up but for totally different reasons, regardless of the type of driver. (I feel the typical subjective reviewer mistakes cause & effect here. Again...) Similar effects certainly can be produced by drivers in closed boxes, but we'll have to compare speakers with identical baffle widths & driver sizes, if we wish to isolate the dipolar behavior.

Geez, a few days ago I was technically incompetent, now I am an adman, not sure how much lower I can sink here. I'll ask Thomas.

I glanced at the Sander's plot and it clearly shows little radiation to the sides and more to the front and back, with increasing directivity with frequency. I have measured and read many similar plots over the years. Yes, transducer and baffle size play a big part in the directivity over frequency, and I clearly said that panel size matters. But I do agree I should have clarified the cause of the effect; I conflated dipoles whilst thinking about comb filter effects. Most speakers become more directive as frequency increases.

In any event, this is not my day job, and I am not an expert in speaker design by any means, so I'll leave it to you experts!

 

[graz_lag]

The Jamo 907 were a joke , a nice designing excercise perhaps as many Danish companies like to do once in a while ...

 

[petsza]

Neither do the DSP'ed box speakers. And the box speakers maintain reasonably sensible time and phase response as you move around them - so the room's reverberation is as though stimulated by something much closer to the ideal speaker. It all 'adds up'.

I even posted a direct quote in my comment...
From the same source:

Not a great feature for the music lover who likes realistic volume levels.

And yes, I have listened to them many times - and never been as stunned as I am by DSP'ed box speakers.

Your view on OB speakers are completely wrong!
Never heard of AudioArtistry in the 90s, by Siegfried Linkwitz? You should educate yourself before speaking out so confidential.

 

[lewdish]

Id like to see ASR do an open baffle measurement and break down what everything means, is it just all hype or is there some objective substance to it.

 

[watchnerd]

Id like to see ASR do an open baffle measurement and break down what everything means, is it just all hype or is there some objective substance to it.

They have different radiation patterns than box speakers.

So, yes, there are physics reasons for why they sound different.

Maybe I'm not understanding the question?

 

[lewdish]

They have different radiation patterns than box speakers.

So, yes, there are physics reasons for why they sound different.

Maybe I'm not understanding the question?

No you got it, but as a result i'd like to know how they measure on the Klippel NFS as a result~

 

[TheGhostOfEugeneDebs]

No you got it, but as a result i'd like to know how they measure on the Klippel NFS as a result~

The Magnepan LRS was measured by Amir and fared extremely poorly. https://www.audiosciencereview.com/forum/index.php?threads/magnepan-lrs-speaker-review.16068/

I don't get it. I love the way Maggies sound, so either myself and my friends are weirdos who have preferences that don't match up with Toole's preference ratings, or there's more to measuring dipoles/ open baffle speakers.

 

[AudioX3]

I have open baffle speakers (Spatial Audion M4 Turbo S) and absolutely love them and think of them as quite natural sounding. I one day will do measurements for the fun of it and to see what comes of the response in my listening position. They also have a rather large sweet spot or at least I can say if you are not in the sweet spot, they sound stage does not collapse it just moves to the left or right.

It would be intersesting if Amir or a member were to measure / analyze.

Speakers to me are one of the areas where you purchase to taste and what works for your room.

I think open baffle appeals to those of us who like a sense of space. I think of it as accurate, but I would not be surprised if the test results were to show measurement issues, nor would I be surprised if they indeed showed excellent measurements. I just know I like the way they sound.

 

[WillBrink]

OB seems to be making a big comeback recently. Like bell bottom jeans...

 

[anmpr1]

I don't get it. I love the way Maggies sound, so either myself and my friends are weirdos who have preferences that don't match up with Toole's preference ratings, or there's more to measuring dipoles/ open baffle speakers.

You have to understand the meaning of the word 'preference'. If you enjoy something that others don't, then that is simply your preference. If 8 out of 10 people rate the Big Mac as the best tasting burger, then does that mean Five Guys is doing it wrong?

Personal anecdote: I have a set of forward firing small box loudspeakers designed (it says in their blurb) in conjunction with Canada's NRC which they claim:

As a result of hundreds of scientific tests, over decades of research, analysts and investigators were able to show measurable characteristics of good sound, and what makes a speaker sound more accurate to our ears.

Well, I have nothing against those loudspeakers. They sound nice, not harsh or offensive, pretty easy on the amplifier, and weren't too expensive. But they are now wrapped up in my attic because the sound just never appealed to me.

If you like what you have, if your loudspeakers make your ears happy, then don't worry too much. After all, we need more happiness in the world.