Directiva r2 project: market requirements gathering

[ctrl]

There is a nice overview of these sort of speakers here

https://www.linkedin.com/pulse/directivity-control-part-1-survey-loudspeaker-systems-steve-mowry

and a follow up page with a design

https://www.linkedin.com/pulse/dire...se-article_more-articles_related-content-card

If rear rejection is not the most important aspect then a supercardioid has a higher DI in the forward direction and is what you tend to get with a rear cancelling driver like the W371.

Thanks for the explanation and definitions. The definition of the term "cardioid" via the polar diagram, DI, the shape of the radiation pattern and the depth of the "null" at 180°, is what I was missing to properly understand the previous posts.

 

[ctrl]

So, now I can also formulate what irritated me so much about the Helsinki example.
So far, one focus of the discussion has been the directivity of the r2 below 1kHz and how the control can be realized.

If one interprets the definition of cardioid behavior a bit more generously, the Helsinki still shows cardioid behavior around 500Hz, but loses control of directivity around 700Hz.

The Princeton measurements unfortunately only go down to 500Hz, but it is easy to see in the frequency response measurements that the speaker clearly expands in its dispersion below 700Hz.

Of course, it could be that the widening in the dispersion of the speaker only occurs for a certain frequency range and when the open-baffle woofer takes over, the directivity changes again.


So the loudspeaker loses control over directivity, at least if you look at the horizontal frequency responses up to 90° or the horizontal sonogram, but still shows cardioid typical behavior.

Therefore, @sarumbear is correct that the Helsinki probably shows a more typical cardioid behavior (in terms of polar radiation pattern), in the frequency range above 500Hz than the 8c, but the 8c has a much better controlled directivity (unfortunately we do not have a direct comparison of the normalized sonograms).

By the way, in the context of loudspeakers, is the right term "dispersion" or "radiation" - not sure which term to use.

 

[Scgorg]

Ow, I ended up starting quite the discussion, pardon that.

The helsinki was used as an example because it was the first thing I could think of with a passive cardioid design and actual polar plots. I did not intend for it to be an example of a perfect cardioid design.

As for the D&D 8C, it does have a pretty "cardioid-ish" behaviour. Erin's review also blessed us with polar balloons such as this:

Here we can see that the dutch and dutch has excellent rear attenuation at 200hz. There are more of these on Erin's review, for anyone interested. Personally I would consider this to be pretty textbook cardioid behaviour (though a polar plot would give easier visual confirmation of that).

To ctrl, I think both dispersion and radiation are alright to use.

 

[TimVG]

I suggested before to let go of the cardioid term to avoid confusing. Pattern control, beamwidth control, dispersion, radiation... It all comes down to the same thing.

Rick has also said no to a wide baffle, this would have been the easiest and cheapest option. So that leaves us with a passive resistance enclosure with controlled leaking, an active version using DSP - or to not bother at all.

 

[sarumbear]

So, now I can also formulate what irritated me so much about the Helsinki example.
So far, one focus of the discussion has been the directivity of the r2 below 1kHz and how the control can be realized.

If one interprets the definition of cardioid behavior a bit more generously, the Helsinki still shows cardioid behavior around 500Hz, but loses control of directivity around 700Hz.

The Princeton measurements unfortunately only go down to 500Hz, but it is easy to see in the frequency response measurements that the speaker clearly expands in its dispersion below 700Hz.

Of course, it could be that the widening in the dispersion of the speaker only occurs for a certain frequency range and when the open-baffle woofer takes over, the directivity changes again.

View attachment 160412 View attachment 160414 View attachment 160440
So the loudspeaker loses control over directivity, at least if you look at the horizontal frequency responses up to 90° or the horizontal sonogram, but still shows cardioid typical behavior.

Therefore, @sarumbear is correct that the Helsinki probably shows a more typical cardioid behavior (in terms of polar radiation pattern), in the frequency range above 500Hz than the 8c, but the 8c has a much better controlled directivity (unfortunately we do not have a direct comparison of the normalized sonograms).

The number one "job" of a cardioid pattern is to reduce rear emissions and stop it completely at 180 degrees to the front panel. Helsinki does that at frequencies where the room boundaries are in effect. I was only commenting on Helsinki's radiation pattern not on any FR anomalies.

However, as this is DIY project my comments were tailored for standard 2-3 way speakers in a simple box that are suitable for a DIY project. Helsinki has a unorthodox shape but it is a passive speaker. On the other hand both D&D 8C and Kii3 are extremely complicated speakers with multiple amplifiers. Kii3 has five power amps driven by an integral DSP in each speaker and has a remote control! Neither designs are within the realms of a DIY project.

By the way, in the context of loudspeakers, is the right term "dispersion" or "radiation" - not sure which term to use.

As an acoustician (see my bio) I can assure you that the correct term is "Radiation Pattern". I may have used other terms in my earlier posts for which I apologise. Posting 2am in the morning while drinking wine is never a good idea to talk technical

 

[TimVG]

Neither designs are within the realms of a DIY project.

Oh I wouldn't know about that .. perhaps the result would be less refined, and not at all claiming it would be easy to properly execute, but we've got some clever minds here.

 

[voodooless]

Oh I wouldn't know about that .. perhaps the result would be less refined, and not at all claiming it would be easy to properly execute, but we've got some clever minds here.

I tend to agree that it might be worth another look. However to lower complexity, one probably would like to keep the number of channels per speaker to 3 or 4. The next question would be if one would need FIR filters, which again raised complexity and also limits the options for DSP's.
The makes the Kii probably too complex. The D&D however might be manageable? I'm contemplating a similar setup, just a bit larger. The current wishlist consists of XT1086 horn/waveguide with BMS 5330ND, B&C 8NDL51-4 as mid, and 2x FaitalPro 10PR320 on the back (closed). Yes, all-pro drivers So higher efficiency, a lot of output with not so much power, and all of these are also very low distortion. But I'm not at all settled on the design or driver choice, so might chip in here to get some more idea's and share my own .

 

[TimVG]

I tend to agree that it might be worth another look. However to lower complexity, one probably would like to keep the number of channels per speaker to 3 or 4. The next question would be if one would need FIR filters, which again raised complexity and also limits the options for DSP's.
The makes the Kii probably too complex. The D&D however might be manageable? I'm contemplating a similar setup, just a bit larger. The current wishlist consists of XT1086 horn/waveguide with BMS 5330ND, B&C 8NDL51-4 as mid, and 2x FaitalPro 10PR320 on the back (closed). Yes, all-pro drivers So higher efficiency, a lot of output with not so much power, and all of these are also very low distortion. But I'm not at all settled on the design or driver choice, so might chip in here to get some more idea's and share my own .

I had similar thoughts when I made my monitors. Since I have a dedicated (although small) room I simply made a large 2-way with pro parts, and since I use 4 dedicated subs I didn't need any low bass anyhow.

 

[voodooless]

Here is some info on passive cardioid tech:

Passive Cardioid Technology | Fulcrum Acoustic

Passive Cardioid TechnologyFulcrum’s latest innovation, their patented Passive Cardioid Technology, was developed to overcome the excessive rear low frequency (LF) radiation that is a major performance challenge of many loudspeakers. The challenge has always been that conventional loudspeakers...

www.fulcrum-acoustic.com

And the patent: https://www.fulcrum-acoustic.com/wp-content/uploads/2019/10/Passive-Cardioid-Speaker-Patent.pdf

 

[TimVG]

Here is some info on passive cardioid tech:

Passive Cardioid Technology | Fulcrum Acoustic

Passive Cardioid TechnologyFulcrum’s latest innovation, their patented Passive Cardioid Technology, was developed to overcome the excessive rear low frequency (LF) radiation that is a major performance challenge of many loudspeakers. The challenge has always been that conventional loudspeakers...

www.fulcrum-acoustic.com

And the patent: https://www.fulcrum-acoustic.com/wp-content/uploads/2019/10/Passive-Cardioid-Speaker-Patent.pdf

And an earlier one from Dutch & Dutch

EP3018915A1 - Directional loudspeaker - Google Patents

A directional loudspeaker is described for use in the mid frequency range of the audio spectrum. The loudspeaker comprises: a housing comprising a front panel, side panels and a back panel, said housing comprising an acoustic resistive material; wherein at least one acoustic transducer is...

patents.google.com

One of the two lead designers of the 8C and other D&D products (that eventually didn't go into production) told me they patented it to prevent direct copies by competitors, but that the general principal was already established and that I should check up on the following as well


T.J. Holmes, “The “Acoustic Resistance Box”—A Fresh Look at an Old Principle”, Journal of the Audio Engineering Society, vol. 34, no. 12, pp 981–989 (December 1986)

J. Backman, “Low–frequency polar pattern control for improved in-room response”, Proceedings of the 115th Convention of the Audio Engineering Society (October 2003)

H.F. Olson, “Gradient Loudspeakers”, Journal of the Audio Engineering Society, vol. 21, no. 2, pp 86–93 (March 1973)

 

[TimVG]

And an earlier one from Dutch & Dutch

EP3018915A1 - Directional loudspeaker - Google Patents

A directional loudspeaker is described for use in the mid frequency range of the audio spectrum. The loudspeaker comprises: a housing comprising a front panel, side panels and a back panel, said housing comprising an acoustic resistive material; wherein at least one acoustic transducer is...

patents.google.com

One of the two lead designers of the 8C and other D&D products (that eventually didn't go into production) told me they patented it to prevent direct copies by competitors, but that the general principal was already established and that I should check up on the following as well


T.J. Holmes, “The “Acoustic Resistance Box”—A Fresh Look at an Old Principle”, Journal of the Audio Engineering Society, vol. 34, no. 12, pp 981–989 (December 1986)

J. Backman, “Low–frequency polar pattern control for improved in-room response”, Proceedings of the 115th Convention of the Audio Engineering Society (October 2003)

H.F. Olson, “Gradient Loudspeakers”, Journal of the Audio Engineering Society, vol. 21, no. 2, pp 86–93 (March 1973)

And one more..

http://www.diva-portal.org/smash/get/diva2:1016965/FULLTEXT02

 

[TimW]

3-4 channels of DSP per side for each speaker makes sense because affordable 8 output devices are fairly common. If you look at the ASR Open Source Streamer thread you will see it has moved in the direction of an easy to use modified version of Moode audio player using CamillaDSP for crossovers and equalization. There was also a member working on an 8 channel DAC that could be used with this platform running on an rpi for an all in one system. Another option would be a USB connected device so long as it has compatible drivers.

If someone wanted to go with a PC based setup there are even more options for 6-8 output devices. Some of the sound card options from the likes of NU Audio and Sound Blaster have been shown to have good performance. There are also recording interfaces like the Behringer Uphoria UMC1820, Tascam US-16x08, PreSonus Studio 1824c, Motu 8pre USB, Focusrite Scarlett 18i20, Motu Ultralite, and many more. These also give multiple input options for the system. Then there is the miniDSP MCHStreamer and USBStreamer which can send and receive 8 channels digitally via optical ADAT. These can be used with something like the Behringer ADA8200, Aphex 141B, or a used mic preamp with ADAT input and output. And then there is the Okto DAC8 Pro.

If you prefer your DSP to be performed on dedicated silicone then miniDSP is the go to. There's the 4x10HD, 10x10HD, DDRC-88A (Dirac Live), C-DSP 6x8, or my personal favorite, the C-DSP 8x12 v2 which can also be upgraded to include Dirac Live.

 

[voodooless]

If you look at the ASR Open Source Streamer thread you will see it has moved in the direction of an easy to use modified version of Moode audio player using CamillaDSP for crossovers and equalization.

As far as I can see, it’s really going nowhere.. but that is a discussion for another day probably

If you prefer your DSP to be performed on dedicated silicone then miniDSP is the go to. There's the 4x10HD, 10x10HD, DDRC-88A (Dirac Live), C-DSP 6x8, or my personal favorite, the C-DSP 8x12 v2 which can also be upgraded to include Dirac Live.

While software solutions are very flexible, they are also less stable (as I’ve seen personally). Also some people might want to use an integrated solution with amps like Hypex offers. Or just cobble together something from AliExpress parts.

I would guess that the DSP section is not part of the Directiva offering? So anyone can choose whatever they like? In that case some ground rules need to be set so enough options are possible. Like #channels, IIR or FIR (how many taps) etc. We’re there any for the R1?

 

[sarumbear]

Here is some info on passive cardioid tech:

Passive Cardioid Technology | Fulcrum Acoustic

Passive Cardioid TechnologyFulcrum’s latest innovation, their patented Passive Cardioid Technology, was developed to overcome the excessive rear low frequency (LF) radiation that is a major performance challenge of many loudspeakers. The challenge has always been that conventional loudspeakers...

www.fulcrum-acoustic.com

And the patent: https://www.fulcrum-acoustic.com/wp-content/uploads/2019/10/Passive-Cardioid-Speaker-Patent.pdf

Interesting design. However, I am not sure how it can work on a wide-range low frequency driver required on 3-way system where the driver have to work up to around 400Hz. Let alone a 2-way where the driver works at much higher frequency. The design relies on the port as as such the cardioid pattern can not extend to much above 100Hz.

 

[voodooless]

Interesting design. However, I am not sure how it can work on a wide-range low frequency driver required on 3-way system where the driver have to work up to around 400Hz.

Why limit the midrange to 400 Hz? You could make a cardioid midrange like the D&D and add cardioid woofers below that Fulcrum style. You can probably get away with a crossover just above 100 Hz with the correct selection of components.

It’s all about choosing the compromise that fits the design goal best.

 

[sarumbear]

Why limit the midrange to 400 Hz? You could make a cardioid midrange like the D&D and add cardioid woofers below that Fulcrum style. You can probably get away with a crossover just above 100 Hz with the correct selection of components.

It’s all about choosing the compromise that fits the design goal best.

The patent and the design you sent works only on the subwoofer frequency range of up to 100Hz. The woofer on a 2-3 way design speaker normally works at least to 400Hz. The said design will not be cardioid above 100Hz. That is what I was trying to explain.

 

[voodooless]

The patent and the design you sent works only on the subwoofer frequency range of up to 100Hz. The woofer on a 2-3 way design speaker normally works at least to 400Hz. The said design will not be cardioid above 100Hz. That is what I was trying to explain.

But it’s based on the assumption that 400 Hz should be the crossover frequency.. so question is: why?

 

[TimVG]

Why limit the midrange to 400 Hz? You could make a cardioid midrange like the D&D and add cardioid woofers below that Fulcrum style. You can probably get away with a crossover just above 100 Hz with the correct selection of components.

It’s all about choosing the compromise that fits the design goal best.

Agree on controlling the midrange radiation this way, but even though the Fulcrum is passive be aware that it will still need active signal shaping to compensate for the lack of efficiency. Also one can argue how useful controlled radiation in the modal range is. It makes sense for PA applications, but in the home..

 

[sarumbear]

But it’s based on the assumption that 400 Hz should be the crossover frequency.. so question is: why?

I did say "at least 400Hz" meaning the crossover frequency will be 400Hz or over. Do you expect to have a drive unit on a 3-way speaker where the midrange driver to work lower than 400Hz?

 

[TimVG]

The patent and the design you sent works only on the subwoofer frequency range of up to 100Hz. The woofer on a 2-3 way design speaker normally works at least to 400Hz. The said design will not be cardioid above 100Hz. That is what I was trying to explain.

Yes, you're correct. Although what voodooless implies is, such as in the D&D patent, one can alter the size, position and resistance of the vents to create different cancellation patterns.