This is a review and detailed measurements of the HSU HB-1 MK 2 bookshelf speaker. It is on kind loan from a member and costs US $169
each as of this writing (normal price $199).
I can't say I am a fan of the industrial looking horn but otherwise, the HB-1 looks fine:
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As you see, it uses a horn-loaded tweeter. Not much to see on the back:
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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 performed over 1000 measurement which resulted in error rate of less than 1%. Temperature was 78 degrees F.
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.
Reference axis was the tweeter center. The front baffler is slanted back. I measured it however as if it were not.
HSU HB-1 MK2 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:
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At first glance the on-axis response looks pretty messy but it is mostly so above 4 kHz. Below that, it is more or less flat within context of a budget speaker. We can see the responsible actors for the frequency response in our near-field measurements of each radiating surface:
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The cabinet resonance radiating through the port is kept at a lower frequency so that it doesn't interfere with the crossover region as much as it does on many other speakers. Woofer could use a sharp filter to not let it resonate in the 2 to 4 kHz. And tweeter/horn could be more well behaved above 10 kHz.
Directivity has some kinks here and there but overall, it is good enough that the off-axis response is similar to on-axis:
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Thankfully the tweeter response narrows in the upper registers which reduces the on-axis resonance we saw at > 10 kHz. So combined the predicted response looks better than our original spin graph shows:
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What do you think this sounds like? Too bright? What about that dip around 4 kHz? Listening tests will answer.
Distortion at 86 dBSPL is kept in check but naturally gets much worse at 96:
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I mentioned earlier that the tweeter beam width narrows in higher frequencies which we clearly see that in our beam width graph:
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So best to point the speaker at you like the manual suggests.
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At the extreme of the frequency range though, we see a widening which I wonder if it is caused by diffraction at various corners of the horn.
Here is the vertical directivity:
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There is an "eye" (hole) in response around 2.5 kHz so best to sit at or (slightly) above tweeter axis.
Finally, here is our impedance and phase graphs:
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HSU HB-1 MK2 Listening Tests
Anyone who thinks you don't need to listen to speakers in objective reviews, should listen to the HSU. Despite the large variations in on-axis response, the overall tonality is almost correct. There is hardly anything to complain about. I took out the EQ tool to see if fixing the response errors make the experience better:
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It took fair bit of doing to create a subjective experience that was better than stock tuning. Filling the hole around 3.5 to 4 kHz took some effort to make sure the overall tonal character wasn't too bright. The upper filters have very subtle effects due to our hearing dropping off rapidly as we get older. Still, I thought the sound was a bit more open and highs a bit more controlled with EQ.
Once there, or even without EQ, this is a very listenable speaker. It handles tons of power. It essentially doesn't bottom out on deep bass. Instead, it makes some noises and has tonal shifts which I prefer to sudden onset of the driver running out of excursion. That horn loading must enable the tweeter to better keep up with the woofer as once again, I am experiencing something slightly unique here in dynamic capability with a horn tweeter as opposed to normal waveguide.
Despite using a single speaker, I could fill my entire large space with sound but it took tons of power. I think the company advertises sensitivity of 92 dB which is a fantasy likely measured like Klipsch at the peak of tweeter resonance. I used almost every bit of my 1000 watt amplifier to drive it at highest playback level.
As an interesting aside, I could see creases in the woofer surround as I pushed it with deep bass but the audible results was not nearly as bad as the visual inspection would predict.
Conclusions
At first glance, the objective measurements of the HSU HB-1 MK 2 indicates a number of problems but a more learned look shows near flat response up to 3+ kHz where most of the spectrum of music is. So no wonder that the subjective experience was mostly positive. It seems that weaknesses of the designs are in areas where it audibly matters less and strength such as very high SPL playback ability are presented front and center. I can't say that we have enough research to objectively quantify everything that is going on in this package. Some interesting compromises were made here to produce a package that performs better than it should "on paper."
My preference is for speakers that objectively leave no question about their performance. But I have to make an exception here and go with my overall experience and a more specific analysis of the objective measurements to put the HSU HB-1 MK 2 on my recommended list.
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As always, questions, comments, recommendations, etc. are welcome.
Man, it has been hell around the house. The wife smelled a bit of sewage in our drain field. Long story short, roots had grown into the distribution box and I spent the entire day with my head inside the stupid box cutting them out and cleaning up the thing. It was one of the hottest days of the week of course causing me to sweat like nobody's business. On top of that, I tested a couple of products that were defective so couldn't publish their reviews. Hence the slow pace of reviews.
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