This is a preliminary outdoor 1m ground plane output compression measurement of a single speaker. No smoothing, no room gain whatsoever. Because I like to tease, I left off the higher volume sweeps above 100dB. I wonder how loud this goes?(Hint, it goes a lot higher
An externally hosted image should be here but it was not working when we last tested it.
A ground plane measurement has 6db gain from the, umm, ground. The speaker is radiating into half-space instead of full space.
While the polars are quite impressive at 100 Hz, the room dominates anyway at that frequency. What is happening from 300 Hz to 20 kHz?
Did you calibrate the SPL using an SPL calibrator? How do you know 100 db in REW is actually 100 db?
Are you coming to Burning Amp? I would certainly like to hear these speakers!
Yes, but bass usually radiates in half space in room as well because most speakers are placed close to the front wall.
Not only that, at bass frequencies, it can be a good feet or two from the front wall and still realize the full 6dB gain due to its long wavelength. Then the boost gets smaller as it is placed further away. But this applies to the distance from the ceiling and the floor, giving additional boosts. Therefore a typical speaker placement in a room achieves SPL that is closer to radiating in quarter space due to partial augmentation from the floor and ceiling. That's why a ground plane measurement, while technically 6dB higher than a full space measurement, is actually almost always on the low side in predicting what can kind of SPL that can be achieved in a room.
This is a calibrated microphone. UMIK-1's are meant to work accurately with REW with its calibration file. But if you wonder if I've calibrated the mic, yes. I've used a microphone calibrator that outputs a 1KHz tone at 94dB and it matches perfectly with REW's capture.
And yes, I'm coming to the Burning Amp. But if it is at the same location, the room acoustics are horrendous.
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Also, this is not a polar measurement. This is an output compression measurement. I should write a bit about this since almost nobody does this kind of tortorous testing on their speakers/subwoofers. This type of testing can easily blow up speakers.
It is by far the most challenging bass measurement to do on a speaker/subwoofer. Many people see a good looking FR at a low test volume and are happy, but the real test is how the speaker holds up at high volumes and at its limits. You almost never see this kind of measurement because it usually makes the speaker in test look really bad. At higher volumes, there are many many factors that affect the output linearity. The long sweep places huge strain on the amplifier and power dissipation on the voice coil. The amplifier struggles to maintain constant power output for the 23 second sweep. The driver will start losing motor force from higher driver excursion. The spiders become non linear and starts tightening at high excursions. On a ported system, you will see output compression well below hitting excursion limits due to port turbulence. Ports can easily compress output by 6-10dB at the highest levels. The port must be excessively large in order to avoid this. A passive radiator does not suffer from this kind of non linearity.
Therefore, at high volume levels, you would see a 5dB increase on the amplifier translating only say 3dB increase in measured SPL because the voice coils are burning up and is reducing system sensitivity due to increased DCR. And this gets worse the louder the volume level is.
Here's a normalized output compression measurement of a medium Xmax 15" subwoofer in a 4.5 cu ft box with a 4" port tuned to 18Hz. You can see the severe port compression around the 18Hz tuning and power compression everywhere else. The peak at 50Hz is because that is near the Fc of the subwoofer, which is the most efficient range of the subwoofer. Therefore, it suffers the least amount of power compression in the system Fc range.
It is by far the most challenging bass measurement to do on a speaker/subwoofer. Many people see a good looking FR at a low test volume and are happy, but the real test is how the speaker holds up at high volumes and at its limits. You almost never see this kind of measurement because it usually makes the speaker in test look really bad. At higher volumes, there are many many factors that affect the output linearity. The long sweep places huge strain on the amplifier and power dissipation on the voice coil. The amplifier struggles to maintain constant power output for the 23 second sweep. The driver will start losing motor force from higher driver excursion. The spiders become non linear and starts tightening at high excursions. On a ported system, you will see output compression well below hitting excursion limits due to port turbulence. Ports can easily compress output by 6-10dB at the highest levels. The port must be excessively large in order to avoid this. A passive radiator does not suffer from this kind of non linearity.
Therefore, at high volume levels, you would see a 5dB increase on the amplifier translating only say 3dB increase in measured SPL because the voice coils are burning up and is reducing system sensitivity due to increased DCR. And this gets worse the louder the volume level is.
Here's a normalized output compression measurement of a medium Xmax 15" subwoofer in a 4.5 cu ft box with a 4" port tuned to 18Hz. You can see the severe port compression around the 18Hz tuning and power compression everywhere else. The peak at 50Hz is because that is near the Fc of the subwoofer, which is the most efficient range of the subwoofer. Therefore, it suffers the least amount of power compression in the system Fc range.
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This right here is probably the best argument I've seen for passive radiator yet. I know people say they're better, but never hear a convincing argument. I wonder how Bowers & Wilkins Flowport or Polk Powerport would compare in this kind of test. This port turbulence is exactly what those are supposed to combat.
To work really well, passive driver should have double the membrane area of the active driver. This is because it has no motor to control the cone, and the need to move bigger air volume when working almost an octave lower than the active driver, to achieve same spl.
Too small port area gives problems too like stated. A small box can not be tuned very low in practise, because there is not enough room for a large vent tube, and this leads to too high port air velocity - noise.
mh-audio.nl - Home
Too small port area gives problems too like stated. A small box can not be tuned very low in practise, because there is not enough room for a large vent tube, and this leads to too high port air velocity - noise.
mh-audio.nl - Home
I just heard the speakers at burning up today they’re amazing
I’m just driving away from burning up at the end of the day and these little speakers were in one of the test room everybody was amazed and Auhhed by the amount of sound and the base extension from these tiny packages. Immediately your first impression when hearing the speakers you definitely are not going to buy anything like this at your big box store or off-the-shelf anywhere. Now I just have to figure out how to re-engineer them and scale them down on parts and materials to Price that’s not more than 1/3 the price of my car when I bought it brand new. 👍👍👍 this will be a great fun project to tackle and the effort will be worth it my ears have already told me so .
I’m just driving away from burning up at the end of the day and these little speakers were in one of the test room everybody was amazed and Auhhed by the amount of sound and the base extension from these tiny packages. Immediately your first impression when hearing the speakers you definitely are not going to buy anything like this at your big box store or off-the-shelf anywhere. Now I just have to figure out how to re-engineer them and scale them down on parts and materials to Price that’s not more than 1/3 the price of my car when I bought it brand new. 👍👍👍 this will be a great fun project to tackle and the effort will be worth it my ears have already told me so .
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I remember seeing (not hearing) these speakers whilst Brian was in my neck of the woods - they were very impressive and definitely at the extreme end of challenging for DIY! In my case I’d probably be trying a build with the electronics on the outside to give myself a fighting chance
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Yes I was thinking of throwing the electronics outside myself and I probably would for my personal use. For my three sons of college-age and the oldest one out of college has a small room and does not like a lot of radio gear he likes everything Bluetooth all in one box. My solution for dissipating heat of the four amplifiers that are located in the box for me is easy to just cast The entire speaker enclosure out of pure copper referee 3/4 to 1 inch thick and then use CNC machining for all the holes and drill points and everything else. I get nearly all the copper I want for free as scraps from leftovers in my job including shielded wiring and I had our local college where I’m a student we get access to the CNC machines for free and at our maker development department they do metalcasting . Copper is extremely dense would make a great dampening material for a speaker enclosure and extremely good at heat dissipation even better than aluminum This would take care of the problem with high power amplifiers located within in the entire surface area of the speaker would become a radiant he dissipator we’re having for class AB amplifiers located inside or higher wattage class D. Principal idea is to keep it the size that a student would take to his dorm or a small living quarters .
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I think we're going to see a lot more speakers along these lines, very compact, full of technology to make it simpler for the user. DeVialet is an example of a company pushing in this direction but there are more of them. I think it's going to be a big part of the future of audio as manufacturers bring 'modern technology' to bear on the challenges of good sound in modern surroundings.
We allready see a lot of speakers like this
This thread
DIY High End Studio Monitors
mentions
Barefoot Sound
Kii Three
Dutch & Dutch 8C
and there are probably more examples out there.
This thread
DIY High End Studio Monitors
mentions
Barefoot Sound
Kii Three
Dutch & Dutch 8C
and there are probably more examples out there.
Hi i came across this interesting open source project called freedsp. Maybe it is a step up from your current minidsp.
I don't know if he mentions it in this thread or not, but Bcodemz doesn't use minidsp anymore. He's been using Jriver for everything, with a 7 channel sound card, the Asus Xonar U7 if I remember correctly.
The problem is this little speaker blows away the techniques or any of those other small little speakers. The commercially available speakers in this category are just blown away by the performance of this speaker there is no comparison. I was just at there burning amp festival this Sunday and heard them playing in the large room they were the one speaker that got everybody to stop look sit down and listen. For speaker this size there was no other speaker at the Burning AMP Festival could even compare to this was in its own level with no competition. This is one of those situations where everybody can talk and they could read about specs and take a look at pictures none of that means anything. When you have the speaker sitting right in front of you playing and you instantly realize it’s like nothing you’ve ever heard before coming out of such a small box.
I was inspired by this thread and decided to give my own speaker a go. I will be printing my enclosure from PLA with a 3d printer. Drivers will be Dayton ND140-4 along with 2 PRs, Vifa TC9FD and SB Acoustics SB26ADC. DSP is Sure Electronics ADAU1701. Kind of a "el cheapo" -version on the reference mini speaker Will post a thread later on it when I make some progress or get the parts.
Will post a thread later on it when I make some progress or get the parts.I was inspired by this thread and decided to give my own speaker a go. I will be printing my enclosure from PLA with a 3d printer. Drivers will be Dayton ND140-4 along with 2 PRs, Vifa TC9FD and SB Acoustics SB26ADC. DSP is Sure Electronics ADAU1701. Kind of a "el cheapo" -version on the reference mini speaker
Awesome! I would love to see this. Make sure to post here once you have it going!
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