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Sehlin Helium DIY Speaker Review

amirm

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This is a (quick) review and detailed measurements of the Sehlin Helium DIY ultra-compact speaker kit. It was sent to me by the designer and member @Mudjock. Here is the cost factors as he provided me:

Drivers + crossover parts: $108.84
Cabinet kit and binding posts: $31.44

This is a very small speaker which literally fits int he palm of your hand:

Sehlin Helium DIY Speaker Audio Reivew.jpg


Needless to say, it was a joy to put on the measurement stand and bring up to my work area to listen. :)

Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.

I used over 800 measurement point which was enough to compute the sound field of the speaker within 1% to 2% error.

Temperature was 81 degrees. Measurement location is at sea level so you compute the pressure.

Measurements are compliant with latest speaker research into what can predict the speaker preference and is standardized in CEA/CTA-2034 ANSI specifications. Likewise listening tests are performed per research that shows mono listening is much more revealing of differences between speakers than stereo or multichannel.

Spinorama Audio Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker is and how it can be used in a room. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:

Sehlin Helium DIY Speaker Spinorama Audio Measurements.png


I went back and forth with the designer as his measurements were smoother than mine. Ultimately he decided that these are probably accurate. If so it is quite uneven as you see.

Sehlin Helium DIY Speaker Spinorama Early Reflections Audio Measurements.png


Sehlin Helium DIY Speaker Spinorama PIR Audio Measurements.png


I could not drive the speaker beyond 80 dB SPL (naturally):

Sehlin Helium DIY Speaker Distortion Audio Measurements.png


Sehlin Helium DIY Speaker Impedance Audio Measurements.png

Sehlin Helium DIY Speaker Beamwidth Audio Measurements.png



Sehlin Helium DIY Speaker Horizontal Directivity Audio Measurements.png


Sehlin Helium DIY Speaker Vertical Directivity Audio Measurements.png


Sehlin Helium DIY Speaker Impedance Audio Measurements.png


Quick Speaker Listening Test
My near-field workstation area is in pieces so I initially tested the Helium far field. Well, let me just say the sound is not right. Tonality is wrong (muffled and boomy), and there is grittiness to sound which I did like. I then sat in front of it while still on my normal stand and the situation improved. But the grittiness was still there.

Conclusions
I don't know how to judge this speaker any other way than I do normally which is to hold it up to the best sound one could get. It is likely quite unfair to do that relative to the tiny size of this speaker. I just don't have another frame of reference. As is then, I am afraid this is a failing attempt. I hope the designer uses this information to refine the product and produce a follow up with better performance. Having something small but very high quality would be dandy.

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As always, questions, comments, recommendations, etc. are welcome.

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Woody Stool

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How good could something that small really be? If the job for the day is to move air something that small is going to have a hard time.

Side question: is there anything this small-ish that is considered a good sounding speaker? NHT Super Zero maybe?
 

Tom C

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I had a pair of Bowers & Wilkins MM-1 that didn’t sound too bad, and easily fit in the palm of my hand. I would think it possible to design something that tests reasonably well.
 

ROOSKIE

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Revel M8?? Taller but still very small and weigh is light.
 

Billy Budapest

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How good could something that small really be? If the job for the day is to move air something that small is going to have a hard time.

Side question: is there anything this small-ish that is considered a good sounding speaker? NHT Super Zero maybe?
Yes, the Super Zero is great sounding speaker, although sans bass. Also, it has an elevated frequency response right around 1k but is otherwise pretty flat. With EQ at 1k and a little at the top of the audible range, it would be very flat.
 

RayDunzl

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Blumlein 88

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Is that a 4 inch woofer? Or smaller? You didn't give those details. Also a view of the rear would be nice. I suppose we also don't have any similarly small speakers to compare it to do we.

Any ideas on how that jagged response from 800 hz to 2 khz happens?

@Mudjock I don't imagine you thought the results would be this way. Kudos for putting it together and sending it in for testing. I've made a few speakers in my time, and who knows how crazy some of those would have measured.
 

q3cpma

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How good could something that small really be? If the job for the day is to move air something that small is going to have a hard time.

Side question: is there anything this small-ish that is considered a good sounding speaker? NHT Super Zero maybe?
Genelec 8010A.
8010kit-image1.jpg

8010A_horizontal_response.png

Obviously, you can't expect much SPL:
Harmonic distortion at 80 dB SPL @ 1 m on axis: 70…400 Hz < 3%, > 400 Hz < 0.5%
 

thewas

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edechamps

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I have added the Sehlin Helium (built by Mudjock) to Loudspeaker Explorer where it can be compared to other speakers.

Consistency within the listening window is okay except at extreme off-axis near 6 kHz:

Loudspeaker Explorer chart(36).png


Since I beat @MZKM here I'm taking the opportunity to announce an Olive preference rating of 3.2.
 

Vladimir Filevski

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Sehlin Helium is a fair attempt to create cheap, very small loudspeaker with easy to find, off the shelf ingredients. How to compare? Opponent should be small also, with comparable price. Not easy to find! Jeff Bagby Quarks? Audioengine A2+ also comes to my mind. Although it is active, it is easy to pair one low cost class D stereo amplifier with Sehlin Helium, for about the same total price. It should be an interesting comparison.
Genelec 8010AP and IK iLoud Micro Monitor are small also, but more expensive. NHT Super Zero, Revel M8 and Vanatoo Transparent Zero are bigger and more expensive than Sehlin Helium plus amp.
 
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MZKM

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How did you place the microphone for 0°? Was it tweeter axis offset to the center of the tweeter, or center of the cabinet?
______
Here are Dayton’s published measurements for the tweeter:
1E494D7D-5626-446B-960A-44917476D091.jpeg

Totally not what we have here. We have narrowing directivity centered at 5kHz and a widening of directivity centered at 9kHz. Dayton shows wide directivity at 5kHz and a slight narrowing at 7kHz.
I wonder if this is just how unit-to-unit variance is for a <$10 tweeter, or if there is something else at play.
 
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napilopez

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Sehlin Helium is a fair attempt to create cheap, very small loudspeaker with easy to find, off the shelf ingredients. How to compare? Opponent should be small also, with comparable price. Not easy to find! Jeff Bagby Quarks? Audioengine A2+ also comes to my mind. Although it is active, it is easy to pair one low cost class D stereo amplifier with Sehlin Helium, for about the same total price. It should be an interesting comparison.
Genelec 8010AP and IK iLoud Micro Monitor are small also, but more expensive. NHT Super Zero, Revel M8 and Vanatoo Transparent Zero are bigger and more expensive than Sehlin Helium plus amp.

Yes, the iLoud Micro monitors almost get it perfect except for the port noise causing high-Q cancellations:

1598177667648.png


Horizontal
1598177711871.png


Vertical:
1598177726065.png


They are perfect to use as little digital piano practice monitors - placed them right on top of my keyboard and they are much better than any built-in digital piano speakers I've heard. I've not noticed 'missing notes' due to the narrow resonacnes.
 

thewas

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