It appears that link may have been incorrect. Here it is:
GRS 8FR-8 Full-Range 8" Speaker Pioneer Type B20FU20-51FW 292-430
GRS 8FR-8 Full-Range 8" Speaker Pioneer Type B20FU20-51FW 292-430
Bumpdate: P-E continues to sell these, now down to less that $15 (<$12 each four or more). I've used them as mini-PA drivers and test drivers for various projects. Peavey is using them or something very much like them in some of their Ecoustic combo amps. As for prevailing opinion, while they may not have quite the same characteristics as the Pioneers, P-E customers seem to be quite happy with them, according to their feedback.
(Do you mean klbird on PE's TechTalk forum?)
Same here. Hard to say either is accurate, being so different from PE's and each other. Since companies can be sued for inaccurate claims, they tend to be pretty close but purposely conservative in case there's slight variance among samples. I can't find Pioneer's original specs, and GRS factory specs are on the PE page previously mentioned. FWIW, here's one each of one each of others' tests. Choose your own dosage of grains of salt, as even these results were criticized by others. And despite differences in reported specs, the testers
GRS
GRS 8FR-8 (Supposed replacement for Pioneer B20FU20-51FW) (Page 1) / FullRangeDriver Forum / Fullrangedriver Forum
* This data was exported from the Dayton Audio WT3 Woofer Tester by "BamaBoy" on the Parts Express website.
*
* Manufacturer: GRS
* Model: 8FR-8
* Piston Diameter = 165.1 mm
* f(s)= 63.25 Hz
* R(e)= 7.43 Ohms
* Z(max)= 49.80 Ohms
* Q(ms)= 5.702
* Q(es)= 1.000
* Q(ts)= 0.851
* V(as)= 32.170 liters (1.136 cubic feet)
* L(e)= 1.14 mH
* n(0)= 0.78 %
* SPL= 91.00 1W/1m
* M(ms)= 12.67 grams
* C(ms)= 0.50 mm/N
* BL= 6.12
=====
Pioneer
BOFU -- Pioneer B20FU
Re 6.567
Fs 40.24
Qem 0.496
Qms 2.723
Qts 0..428
Qem 0.496
Le 0.496
Vas 67.82
BL 7.149
Perhaps it'd be best if by "replacement", people (including or especially PE) meant not drop-in replacement, but rather something that could be built around to get comparable performance. Even if I had the Pioneer specs, I'd continue to build mine around the GRS specs.
I'll pick up one or two the next PE order. No great love from me for BOFU as they rot fast in my climate - rather have cloth surround L.Cao, Fostex, Nirvana although much more money. Does GRS use inferior magnet material? (not to say original was great) - not charged well? I've seen lots of Chinese drivers whose slugs weigh a lot but have no power. A Visaton BG20 is good for relatively low money.
here's a late Pioneer BOFU in my pile
here's a late Pioneer BOFU in my pile
An externally hosted image should be here but it was not working when we last tested it.
Hmm, here's what I copied/pasted last year.............
Reviews:
AUDIOBIRD:
I ordered four of these for future projects and when they arrived I quickly put them through the WT3 tests. They are far from the advertised specs. Examples are: FS is 58Hz not 39Hz, Vas 0.815, Not 2.26 and Qts is .936 not .40. All four were within 5% of the above measurements. I placed one of them in a 1.0 cu Ft test box and found the bass adequate but the treble was lacking even with the wizzer cone. Serious music listening with these speakers will require a tweeter. Workmanship was poor as some of the whizzer cones were out of round and had creases in them.
They can handle a lot of power and the overall sound was
fine for background listening. I am going to cut the wizzers off and use them as woofers.
Overall not a bad speaker for the price buit PE needs to tighten up on the published specs and re-measure what they have in stock.
Pioneer's specs changed as its manufacturing location moved from Japan, Taiwan, Thailand, China, each time basically raising Fs, losing motor strength [Qts] and being ~offset by shrinking Vas. This was also partly done because amp damping kept increasing [lowering output impedance] until the driver's Qts + any wiring resistance was completely responsible.
Anyway, here's PE's measured BOFU specs: http://www.parts-express.com/pedocs/specs/290-045-pioneer-specifications-44291.pdf
GM
Reviews:
AUDIOBIRD:
I ordered four of these for future projects and when they arrived I quickly put them through the WT3 tests. They are far from the advertised specs. Examples are: FS is 58Hz not 39Hz, Vas 0.815, Not 2.26 and Qts is .936 not .40. All four were within 5% of the above measurements. I placed one of them in a 1.0 cu Ft test box and found the bass adequate but the treble was lacking even with the wizzer cone. Serious music listening with these speakers will require a tweeter. Workmanship was poor as some of the whizzer cones were out of round and had creases in them.
They can handle a lot of power and the overall sound was
fine for background listening. I am going to cut the wizzers off and use them as woofers.
Overall not a bad speaker for the price buit PE needs to tighten up on the published specs and re-measure what they have in stock.
Pioneer's specs changed as its manufacturing location moved from Japan, Taiwan, Thailand, China, each time basically raising Fs, losing motor strength [Qts] and being ~offset by shrinking Vas. This was also partly done because amp damping kept increasing [lowering output impedance] until the driver's Qts + any wiring resistance was completely responsible.
Anyway, here's PE's measured BOFU specs: http://www.parts-express.com/pedocs/specs/290-045-pioneer-specifications-44291.pdf
GM
They look like the B20 but don't sound like them. I have both and listened to them often - preferring the B20 by a large margin. Having said that, both make sound and can be enjoyed... tho I enjoyed the GRS less. Regarding freddiy's magnet question, I remember placing the GRS onto a refrigerator that had magnets stuck to it and it didn't stick very well. Never tried this with any other driver.
Very true, but I don't recall anyone doing 1 on 1 comparative listening test. Audiobird claimed they sounded different, but didn't do a comparison as far as I can tell, just a listening test with the WT3. And, as he mentioned, Pioneer's specs drifted, so it's a shame they're gone and be comparison tested.
I was testing a pair of them in Karlson Klam 8s very much like Freddi's avatar, strictly 1 watt output of both 1 kHz and recorded material. People stopped to listen and commented on how good they sounded for something so small. I even had to prove to one person that it was 1 watt only. I've tested many things there but this was the only time people spent time listening.
"The same"? Almost certainly not. As good? Possibly, if done up right. For the money? Darn hard to beat. PE is charging 40% less than their original price, but they're also carrying a lot more models of GRS drivers now, so somebody is doing something right. I've got 8 in boxes and a couple recycled ones just waiting for new projects.
can't find my newest BOFU, but one probably a decade+ old which came in an Alan Weiss Karlson-klam patio speaker was laying out - a touch of the surround made the typical crumble - here's its electrical stuff (if can read the skipping ink pen stuff)
Re=6.322, fs = 36.34, Qes = 0.5898, Qms = 2.148, Qts = 04627, Le = 0.7302
its too bad Pioneer couldn't have offered a version with a surround which would last better. Thankfully they didn't cost Lowther money.
for US$27, BG20 are decent. are there surrounds which are suitable to restore BOFU?
these commercial goodies came loaded with BOFU - maybe also the old Radio Shack 8. i had a copy based on this klam's dimensions loaded with BOFU and it worked well outdoors. Loaded with a $13 Sammi, one little klam was pretty loud 150 feet away and almost like a concert at 75 (coil probably getting pretty hot)
hey Doc - any chance of you still doing a wiki for JK ?
here's my last real BOFU vs a stamped frame Nirvana Super 8 on-axis - in-room with each in the same direct radiator MLTL - maybe BOFU's rather soft cone was responsible for its nice quality - is the GRS similar paper-wise?
and with mic and enclosure positions fixed
Re=6.322, fs = 36.34, Qes = 0.5898, Qms = 2.148, Qts = 04627, Le = 0.7302
its too bad Pioneer couldn't have offered a version with a surround which would last better. Thankfully they didn't cost Lowther money.
for US$27, BG20 are decent. are there surrounds which are suitable to restore BOFU?
these commercial goodies came loaded with BOFU - maybe also the old Radio Shack 8. i had a copy based on this klam's dimensions loaded with BOFU and it worked well outdoors. Loaded with a $13 Sammi, one little klam was pretty loud 150 feet away and almost like a concert at 75 (coil probably getting pretty hot)
hey Doc - any chance of you still doing a wiki for JK ?
An externally hosted image should be here but it was not working when we last tested it.
here's my last real BOFU vs a stamped frame Nirvana Super 8 on-axis - in-room with each in the same direct radiator MLTL - maybe BOFU's rather soft cone was responsible for its nice quality - is the GRS similar paper-wise?
An externally hosted image should be here but it was not working when we last tested it.
and with mic and enclosure positions fixed
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Being a rather generic 8" with W.E./Jensen design roots that date back to at least to the '50s, I'd be surprised if there's not a cloth accordion surround suitable for doping still available.
Kneading some/all of the starch out of the whizzer goes a long way towards smoothing out these type drivers. Ditto judicial doping with Dammar and if too 'soft' a dynamics, then use shellac.
GM
This seems to be the most recent GRS8FR8 thread and the only one with reported T/S specs, so I'll post my recent findings here. I just finished testing five of these with REW and the added mass method. I'm about 93% confident in my testing setup. After running all five (four were post-break-in, one fresh out the box) this tends to be the average results:
fs 55.1 Hz
Qms 6.360
Qes 0.689
Qts 0.622
Fts 95.9
Mms 14.68 g
Cms 0.486 mm/N
Rms 0.865 kg/s
Vas 35.48 litres
Bl 7.672 Tm
FS on the broken in ones was closer to 55 with the fresh one at 62Hz
Break-in process was ~40hrs of play various material while the drivers just sat on a shelf.
I'm glad the Qts isn't up in the 0.85 range, but wish it was closer to 0.4
fs 55.1 Hz
Qms 6.360
Qes 0.689
Qts 0.622
Fts 95.9
Mms 14.68 g
Cms 0.486 mm/N
Rms 0.865 kg/s
Vas 35.48 litres
Bl 7.672 Tm
FS on the broken in ones was closer to 55 with the fresh one at 62Hz
Break-in process was ~40hrs of play various material while the drivers just sat on a shelf.
I'm glad the Qts isn't up in the 0.85 range, but wish it was closer to 0.4
The Qts is pretty high. I am wondering about this driver on open baffle lately. Perhaps it's worth another listen without bass frequencies running thru it? Unfortunately I don't have the drivers anymore 
I remember they sounded a bit garbled in 1cf sealed boxes. Is there a frequency response somewhere?
I remember they sounded a bit garbled in 1cf sealed boxes. Is there a frequency response somewhere?
The Qts is pretty high. I am wondering about this driver on open baffle lately. Perhaps it's worth another listen without bass frequencies running thru it? Unfortunately I don't have the drivers anymore
I remember they sounded a bit garbled in 1cf sealed boxes. Is there a frequency response somewhere?
hey 'Zilla
Bob Brines has worked with them.
BOFU -- Pioneer B20FU
FR as posted above in a fake Druid size pipe - green trace = Pioneer BOFU - the foam surrounds rotted so fast - a pleated cloth surround would have been nice -- look how hot on axis Nirvana's stamped frame Super8 was in comparison on the top octave
An externally hosted image should be here but it was not working when we last tested it.
must be a 'replacement driver' for the bofu based on appearance and not specs, then?
Not even looks beyond it being a whizzer cone 8", what with different ribbing and a much larger whizzer.
Shame on PE, it's still showing BOFU specs on site and in it's latest catalog for this $#@%^* GRS......... Probably better overall to buy a cheap ceiling PA coax driver; at least they will have a good speech BW reproduction and coincident tweeter.
GM
Shame on PE, it's still showing BOFU specs on site and in it's latest catalog for this $#@%^* GRS......... Probably better overall to buy a cheap ceiling PA coax driver; at least they will have a good speech BW reproduction and coincident tweeter.
GM
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