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Get familiar with the reaction system: Introducing the Reaction System

HiVi F8

Manually exercised (measured/advertised)

Loudspeaker parameters:

Fs  = 42.93 Hz/37 Hz
Re  = 6.30 ohms[dc]/6.5
Le  = 309.27 uH
L2  = 785.20 uH
R2  = 21.80 ohms
Qt  = 0.46 / 0.4
Qes = 0.49/0.44
Qms = 6.80/4.71
Mms = 29.13 grams
Rms = 1.155833 kg/s
Cms = 0.000472 m/N
Vas = 30.30 liters/39
Sd= 213.82 cm^2
Bl  = 10.035572 Tm
ETA = 0.47 %
Lp(2.83V/1m) = 89.85 dB/88

Added Mass Method:
Added mass = 35.00 grams
Diameter= 16.50 cm

Definitely tighter than most of the HiVi stuff I have had in my hands. Close enough that using advertised parameters will get very close, and they might break in a little further and come closer, who knows. I do know they offer a very loose suspension out of the box, not sure how much more break-in will actually occur.

So, typical HiVi dumb oversized frame with the excessive detail and screwholes distracts from an otherwise nice looking driver. No venting out the ass nor is there any under the spider. This design is showing its age in that regards. It does rock a 35mm voice coil, though, with a respectable 17mm winding length. That might dissipate heat fast enough under load. Personally I don't really worry about thermal compression since I actually, you know, like protecting my ears. For SPL junkies, though, this will probably not hold up to extended 95-100 db listening sessions. 

Impedance sweep shows a lot of nasties above ~800, I don't think based strictly on those that I would use this driver in a 2-way. The advertised response curve shows some jaggies above 800 as well. It models well, though, I like it in 30L tuned to 45. I typically model with 0.5 to 1.0 Ohms series resistance. In this case, F3/6/10 of 47.5/39/33 is achievable. Not too terribly shitty since it really lacks the built in ability to handle really low frequencies. Throw a 40Hz highpass on it and crank it up. That almost 90dB sensitivity makes me pretty happy, means we can burn some up playing with higher Re coils. In parallel pairs, these will probably play as loud as sane people would ever want, would just need a pretty sensitive mid/tweeter combo to keep up.

Anywhoo, no immediate plans for these, saw them on sale and grabbed them. Studio guys and musicians seem to pop wood over yellow cones, so I might throw a WT/M together someday and see if any of my local connections bite. Looks to be a pretty good match for the Dayton RS52-F and maybe one of their newfangled small form factor tweeters. 

Or I may see if someone is interested in trading at IowaDIY. I legitimately bought these out of curiosity. 

I have a signature.


  • I have a pair of the F8's that I conjured up a BIG 2-way with a while back. Used the Usher 9950 for the tweeter. I eventually dismantled those and build a 3-way along with the RS52 and the RS28A. There is bass to spare but they also need watts. I've really enjoyed them. I think putting them with the RS52 fabric dome would be a great match-up.

  • The only 2-way with these I knew of before reading of Richard's design here, were Robert Bantly's 'Throwbacks' with the 27TDFC. That would have been InDIYana and Iowa 2009, IIRC.
  • edited September 2018
    Wolf said:
    The only 2-way with these I knew of before reading of Richard's design here, were Robert Bantly's 'Throwbacks' with the 27TDFC. That would have been InDIYana and Iowa 2009, IIRC.
    Robert and I swapped a lot of info and ideas over PETT during the design but my 2-way never made it to a DIY event. I was happy with the sound but the 40+ liter boxes, ehh, not so much. That's part of the reason why the 3-way went "un-boxy".

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