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The HiVi M8a is the last 8″ woofer that I have from this manufacturer. I bought four units way back in 2013, so it has been more than ten years. Over that period, I tried her in different designs, even drawing inspiration from the the JBL 4425 studio monitor by mating her with the JBL2342 coupled to a JBL 2425 compression driver. Though the result was satisfactory, I was never really excited about the music. Since I am testing out 8″ woofers for their bass performance, this is the best time to look into the M8a again. It will be interesting to hear how her bass sounds like. Out of convenience, I loaded her into a 20 liters Sealed Box. I decided on this loading after her dismal performance in a bass reflex in my other designs.
According to the simulation above, her Q is at 0.777. Personally, I prefer Q in the 0.5 region but this will have to do for now. F3 is at 53.5Hz which is perfectly fine for music. Being in a sealed box, the bass will sound more natural because the roll-off is not as steep as a bass reflex. the Inductor I retained the 10mH inductor as before since it worked with my other 8Ω woofers. There’s no necessity to change the inductor unless something crops up during audition. The last thing I want is to add more components to the crossover. From my previous tests, even a zobel network has an adverse effect on the music. HiVi M8a Bass I couldn’t believe my ears. From the first track, the M8a sounds exactly like the F8. Maybe a little bit more “meat”, that’s all. However, after three days, there is a noticeable change in the bass. It tightened up considerably. Now, the M8a sounds between the F8 and the C8. I don’t regard this as a weakness in the M8a. As a matter of fact, the M8a can be made to blow listeners away. Imagine having two M8a in a sealed box and using EQ to boost the 50Hz region. That would sound smashing. I’m having visions of the Watt-Puppy thinking about this. It’s a shame these M8a are no longer available. They are actually pretty good woofers. The closest is the M8N. This version is available and shares the same Aluminum/Magnesium cone as the M8a. The difference is she uses a stamped steel frame whereas the M8a is cast. Their T/S are almost the same, so there’s a good chance the M8N will sound similar. Summary This exercise proves once and for all that trying to design a 2-way with 8″ woofers is futile. The crossover can be done but the resulting music leaves a lot to be desired. The bass is just neither here nor there. It doesn’t stand out the way I want. This only applies to Hi-Fi drivers. I have no issues using pro drivers in 2-ways. I’ve used 10″ and 12″ woofers with compression drivers and horns with outstanding performance. Unless otherwise stated, all measurements were made in Full Space (4pi). Mic at 36 ins, tweeter axis. Impulse Window=5ms. No smoothing applied. |
February 11, 2024HIFI DRIVERS, Projects
