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Get familiar with the reaction system: Introducing the Reaction System
Blue Octave BDW8 - generic in-wall
Picked up a pair of these off of Fleabay for shits and giggles - I think a pair is under $60 shipped.
8" woven fiber cone woofer with a blue color to it. Rubber surround, black rigid dustcap. Cone is somewhat translucent, looks cool when you hold it up to the light.
Advertised as a subwoofer, but it really isn't. I was expecting it to be very high Q, but that is not the case:
In point of fact, it has parameters closely resembling some classic acoustic suspension drivers of the past albeit with a lower compliance than some of them.
I had this thing pumping during the break-in, and the cone would not bottom out even with what appeared to be 20mm of total throw. So, Xmech is very generous but I estimate overhang Xmax is probably in the 4-5mm range. It seemed fairly clean, however, even with the very high excursions I was putting it through.
This is a really nice looking driver - maybe I will print some cosmetic rings for it or see if Meniscus still has any of those rings left and grab a few. It has a raised spider, and a bumped and vented back plate but that appears to be about as far as excursion goodies go. Plugging the back plate vent increases mechanical noise considerably. Not sure how many of you have ever experimented with that, can be good to hear why these things are important.
Impedance sweep:
The blue is free-air, the red is Delta mass. Inductance curve indicates I will probably not be using this in a 2-way, even though the impedance is free of any wrinkles until 3500 Hz. That indicates to me a smooth response with a break-up well above an expected crossover point. On a lot of these cheap drivers, there are wrinkles between 1 and 2K where a cliff in the response can be found - I see no evidence of that here. However, inductance is fairly high on this woofer, so I imagine distortion above, say, 500Hz or so would lead to less than acceptable performance. Of course, it might surprise me - that happens.
I think a small tower or coffin type of speaker around 1 cubic foot, vented and tuned to 40Hz with a lot of stuffing in it would yield a fairly nice alignment:
That yields F3/6/10 of 46/35/29 - not too shitty.
What about in-wall? Assuming 14.5" X 92" x 3.5" sealed (even though it is probably somewhat leaky between studs), with just a bit of stuffing (modeled in WBCD with Qa of 80), we get this:
Ignoring the massive boundary reinforcement one could expect from mounting it in-wall and probably close to the floor, we have F3/6/10 of 51/40/31. I imagine plenty of reinforcement would kick in and I would not be surprised if typical in-room was approaching 30Hz flat. I am generally impressed with the Ts parameters for this driver given the anticipated installation.
I threw the bezels and grilles away, I hate in-wall speakers lol.
Anywhoo, here it is in one cubic foot heavily stuffed:
F3/6/10 of 58/45/35. Not too shabby, actually. Keep in mind all modeling was done with series resistance of 1 ohm. If a guy was to use these with a subwoofer amp, the F3 generally rises but the F10 generally lowers.
These are allegedly built/imported/marketed by Goldwood Sound, but the website is pretty sketchy so it was definitely a shot in the dark.
Up next, I hope to dismantle a set of the 8" Kevlar 3-way Monoprice in-wall speakers - except those fuckers sent me a box containing 150 or so USB-C to MiniDisplayPort adapters instead. While they figure that out, I wait. Retail on that box of cables is over $2000, so worst case I will sell it as a bulk pack to another Ebayer for ~1/3 of retail and someone else can package and sell over a hundred frickin cables.
8" woven fiber cone woofer with a blue color to it. Rubber surround, black rigid dustcap. Cone is somewhat translucent, looks cool when you hold it up to the light.
Advertised as a subwoofer, but it really isn't. I was expecting it to be very high Q, but that is not the case:
Loudspeaker parameters:
Fs = 46.10 Hz
Re = 7.08 ohms[dc]
Le = 604.97 uH
L2 = 1626.49 uH
R2 = 49.49 ohms
Qt = 0.57
Qes = 0.64
Qms = 5.05
Mms = 30.84 grams
Rms = 1.768615 kg/s
Cms = 0.000386 m/N
Vas = 27.97 liters
Sd= 226.98 cm^2
Bl = 9.968871 Tm
ETA = 0.41 %
Lp(2.83V/1m) = 88.80 dB
Added Mass Method:
Added mass = 40.00 grams
Diameter= 17.00 cm
In point of fact, it has parameters closely resembling some classic acoustic suspension drivers of the past albeit with a lower compliance than some of them.
I had this thing pumping during the break-in, and the cone would not bottom out even with what appeared to be 20mm of total throw. So, Xmech is very generous but I estimate overhang Xmax is probably in the 4-5mm range. It seemed fairly clean, however, even with the very high excursions I was putting it through.
This is a really nice looking driver - maybe I will print some cosmetic rings for it or see if Meniscus still has any of those rings left and grab a few. It has a raised spider, and a bumped and vented back plate but that appears to be about as far as excursion goodies go. Plugging the back plate vent increases mechanical noise considerably. Not sure how many of you have ever experimented with that, can be good to hear why these things are important.
Impedance sweep:
The blue is free-air, the red is Delta mass. Inductance curve indicates I will probably not be using this in a 2-way, even though the impedance is free of any wrinkles until 3500 Hz. That indicates to me a smooth response with a break-up well above an expected crossover point. On a lot of these cheap drivers, there are wrinkles between 1 and 2K where a cliff in the response can be found - I see no evidence of that here. However, inductance is fairly high on this woofer, so I imagine distortion above, say, 500Hz or so would lead to less than acceptable performance. Of course, it might surprise me - that happens.
I think a small tower or coffin type of speaker around 1 cubic foot, vented and tuned to 40Hz with a lot of stuffing in it would yield a fairly nice alignment:
That yields F3/6/10 of 46/35/29 - not too shitty.
What about in-wall? Assuming 14.5" X 92" x 3.5" sealed (even though it is probably somewhat leaky between studs), with just a bit of stuffing (modeled in WBCD with Qa of 80), we get this:
Ignoring the massive boundary reinforcement one could expect from mounting it in-wall and probably close to the floor, we have F3/6/10 of 51/40/31. I imagine plenty of reinforcement would kick in and I would not be surprised if typical in-room was approaching 30Hz flat. I am generally impressed with the Ts parameters for this driver given the anticipated installation.
I threw the bezels and grilles away, I hate in-wall speakers lol.
Anywhoo, here it is in one cubic foot heavily stuffed:
F3/6/10 of 58/45/35. Not too shabby, actually. Keep in mind all modeling was done with series resistance of 1 ohm. If a guy was to use these with a subwoofer amp, the F3 generally rises but the F10 generally lowers.
These are allegedly built/imported/marketed by Goldwood Sound, but the website is pretty sketchy so it was definitely a shot in the dark.
Up next, I hope to dismantle a set of the 8" Kevlar 3-way Monoprice in-wall speakers - except those fuckers sent me a box containing 150 or so USB-C to MiniDisplayPort adapters instead. While they figure that out, I wait. Retail on that box of cables is over $2000, so worst case I will sell it as a bulk pack to another Ebayer for ~1/3 of retail and someone else can package and sell over a hundred frickin cables.
I have a signature.
