Active monitors with deep low end

[ChrisG]

The source's directivity is irrelevant here: we're talking about the directivity of the microphone under test.

ie, at the end of the test, this graph can be made:

Edit to add: I can see why Rasboo wants a point source: anything other that a point source will mean one passband is arriving at an angle to the microphone. The only fix there is to change the mic position.



NB - All of this requires that the speaker/subwoofer is the primary sound source. Real-world acoustics may present problems, which is why a lot of this sort of testing gets done in an anechoic chamber.


Chris

 

[sigbergaudio]

Yees, without being a microphone expert I am just guessing that you will not register a lot of microphone directivity either at 20hz, since the SPL level in the general area of the entire microphone is likely to be very similar due to the nature of low frequency sound. But I might be wrong. But I again I think simply putting a sub beneath the speaker should work well for this.

And to be even more pragmatic: If we are analyzing single frequencies, can't we just use a subwoofer for the frequencies below 100hz, why does it have to be the same source at all frequencies?

 

[Ken Tajalli]

Why has Neumann KH120 II not mentioned yet?
They go deep, clean deep, perhaps not too loudly, but still!
I have heard them, unbelievable sound.

Neumann KH120 II Monitor Review

This is a review, detailed measurements and listening tests/EQ of Neumann KH120 MKII DSP active monitor (speaker). It is on kind loan from the company and costs US $999 each. I love the form factor for desktop use. It is not too deep or unwieldly as some larger configurations can be: Back...

www.audiosciencereview.com

 

[Rasboo]

If it was my project, I'd put a 3" coaxial and an 8" long-throw subwoofer driver in a cabinet. Measure 20Hz-200Hz with the 8", and then 100Hz-20kHz with the 3" coaxial. Splice the data in the overlapping octave.

Thank for being understanding
This was the first plan actually, and it is likely still the most plausible. But finding some "close to coaxial" solution would save a lot of time in the long run
My work isn't really about microphone directivity, but I work with headphones and active noise cancellation so it is one of these things I need to keep a close eye at. As you have probably understood, it's about correlating measurements to excitations. So the annoying thing about using multiple drivers is that the group delay between the measurements basically would need to be adjusted every time the measurement setup is changed. Since I'm not the only one using our anechoic chamber, this could be a real time robber...

I don't disagree with the rest of you all, but I won't join the general discussions about low-bass sound, it is a messy SUBject (sorry)

 

[Rasboo]

In order to make useful recommendations, my question is this: what's the measurement distance?

Sorry, i missed this. We do all kinds of measurements here so it varies fairly wildly depending on DUT and reference. Did a test to check for distortion in a bom mic the other day, that was at a distance of 30mm. But I would say 1.5m tops at least.

Recommendations for a bit pricier speakers are also welcome! I might start with my Genelec Triamps or borrow something with a bigger woofer to probe the room first and hopefully get a bigger budget if the room proves that it can handle it.

 

[DearSX]

I have the $4k Buchardt A10 monitors, with a great 6.5" woofer and DSP and it has extended output to 28hz, but its very limited in regards to SPL at that frequency. I came to the conclusion that the only way to get great dynamics at loud volumes and very clean sound is to move a lot of air. Even many of the best 8"-10" woofers struggle with lower bass and dynamics over 86dB without 3% plus distortion. I think the solution is to move a lot of air with large or multiple woofers or subwoofers, or just accept physics.

I have a 3-way DIY speaker with sealed 10" woofers, and it can get boomy in my room, but the A10s are not.

 

[Rasboo]

Is there a verdict here on Yamaha's HS8? Can't find much actual data on it..
Same goes for Focal's Alpha 80 Evo.
I expect the Yamaha's to lack bottom out of the box, but some say they sound rather "full"...

 

[ChrisG]

Yees, without being a microphone expert I am just guessing that you will not register a lot of microphone directivity either at 20hz, since the SPL level in the general area of the entire microphone is likely to be very similar due to the nature of low frequency sound. But I might be wrong.

Allow me to rephrase: microphone directivity is the measure of the microphone's sensitivity to sound incident from a particular direction, as a function of the angle of incidence.

Thank for being understanding
This was the first plan actually, and it is likely still the most plausible. But finding some "close to coaxial" solution would save a lot of time in the long run
My work isn't really about microphone directivity, but I work with headphones and active noise cancellation so it is one of these things I need to keep a close eye at. As you have probably understood, it's about correlating measurements to excitations. So the annoying thing about using multiple drivers is that the group delay between the measurements basically would need to be adjusted every time the measurement setup is changed. Since I'm not the only one using our anechoic chamber, this could be a real time robber...

I don't disagree with the rest of you all, but I won't join the general discussions about low-bass sound, it is a messy SUBject (sorry)

You're welcome.

My recommendation: 12" subwoofer driver, and coaxially mount a 3" coaxial driver. 3-way design. You'll need to design a small "pod" enclosure for the 3" driver to sit in, in front of the 12" cone. Use some DSP to time-align the two passbands, and you should be good to go.

FWIW, none of the 8" 2-way monitors I'm aware of will put out 20Hz. 40Hz, probably, but that's a full octave short. I also expect that a fully-coaxial design might be beneficial to you.


Chris

 

[Doenerkunde]

Any affordable 10" out there that i have missed?
Price range is approximately 1000$

KRK Rokit RP10-3 Gen4. Three way monitor with a 10 Inch woofer. Should yield a -6dB rolloff point around 30hz and their street price fits your budget.

 

[Rasboo]

Allow me to rephrase: microphone directivity is the measure of the microphone's sensitivity to sound incident from a particular direction, as a function of the angle of incidence.



You're welcome.

My recommendation: 12" subwoofer driver, and coaxially mount a 3" coaxial driver. 3-way design. You'll need to design a small "pod" enclosure for the 3" driver to sit in, in front of the 12" cone. Use some DSP to time-align the two passbands, and you should be good to go.

FWIW, none of the 8" 2-way monitors I'm aware of will put out 20Hz. 40Hz, probably, but that's a full octave short. I also expect that a fully-coaxial design might be beneficial to you.


Chris

hehe. The coaxial mount is an idea i have sketched on during the day. This is definitively something i will considder.

Now i should say, if only for posterity. I was clumsy when writing "all the way down towards 20Hz". I just mean farther down than 40Hz. We have noise spikes here at around 35Hz that we can't isolate away and need to drown out. But realistically we don't need all to much accuracy lower than that. We just need to be sure that what we are reading is coming from the room and not some inherent noise in the DUT..

Thanks again for the help.

 

[ChrisG]

A decent 8" monitor might hit 35Hz with reasonable authority. However, for a noise-cancelling application, I'd probably want a lower cutoff around 20Hz. VLF noise can still be annoying, although I can imagine that if you try to go too low, you might end up battling wind noise in the real world.
Still, artificially limiting your testing seems unwise to me. 20Hz is a possibility.


FWIW, an off-the-shelf coaxial build could be: a store-bought 12" subwoofer (find one with a sealed cabinet, not ported), add an Audix cab-grabber from the live sound world, and use that to attach the mid-high speaker of your choice.


Chris

 

[Rasboo]

(find one with a sealed cabinet, not ported)

Can you expand on that, how come you recommend sealed in this case?

 

[markstein]

Let me ask, why 20Hz? There is very little going on there.

I would extend my budget and try to get BETTER bass with multiple subs.

 

[ChrisG]

Can you expand on that, how come you recommend sealed in this case?

A ported subwoofer has its output solely from the port for a narrow frequency range. ie, it's not a point source any more.
Also, below the port tuning frequency, there's basically-zero output available. Sealed cabinets can get down to the very-low-frequency range, but don't get as loud as ported boxes. Everything's a compromise. In your situation, I'd go for sealed.


Chris

 

[Kyle_PL]

Why has Neumann KH120 II not mentioned yet?
They go deep, clean deep, perhaps not too loudly, but still!
I have heard them, unbelievable sound.

Neumann KH120 II Monitor Review

This is a review, detailed measurements and listening tests/EQ of Neumann KH120 MKII DSP active monitor (speaker). It is on kind loan from the company and costs US $999 each. I love the form factor for desktop use. It is not too deep or unwieldly as some larger configurations can be: Back...

www.audiosciencereview.com

They go down to ~45Hz @ -3dB - it's not deep. Deep is let's say 30Hz @-3 dB. Even Neumann KH 150 can't do that ... but Neumann KH120II+Neumann KH750DSP do.

 

[Ciobi69]

1000$ they don't exist buddy, sadly there is 2 option or you get a neumann 420 but its not the case because they cost 8000$, or you could get for example a pair of kali in v2 and pair it with a subwoofer, or any other monitor with subs..

 

[Rasboo]

I can give a short update on how this project ended up. I went with a Presonus Eris 8" coaxial monitor. After careful consideration it looked like the best compromise.
It does delivers reasonably well, not the flattest response by any means but it delivers where we need it as it manages to over-power our abient noisefloor down to 20Hz enough to get stable phase measurements.
The main issue is probably the front ported design, which i think basically acts as a phase inverted sound source around it's resonant frequency (is this accurate enough to be a reasonable simplification? Idk). But after shoving some acoustic material in the port and experimenting a bit i can get nice and consistent readings without severe regions of phase cancellations.


Thanks for all the help

 

[ChrisG]

Blocking the port is a reasonable approach. A rolled-up pair of socks usually does the job nicely.

Glad you've found something that works for you.


Chris