Thanks for sharing!
FWIW, based on a typical 206 cm^2 Sd and your Fs, Cms, Rms, BL; Hornresp required a 6.8 ohm Re to get a rounded off 0.69 Qes, 0.62 Qts, though Qms = 6.83 and Vas = 29.41 L.
So, what is the average Re and what Sd did you use?
GM
Last edited:
So for DC resistance I have a very unreliable handheld meter that rounds up to 8ohms where I do actually believe the spec sheet at 7.0 ohms. Thus that is the value I used to enter into the input parameters for REW.
Here are the output of the added mass method (27.5g added each time):
GRS 1
fs 54.7 Hz
Qms 6.730
Qes 0.748
Qts 0.673
Fts 81.3
Mms 19.24 g
Cms 0.440 mm/N
Rms 0.983 kg/s
Vas 32.13 litres
Bl 8.323 Tm
Eta 0.69 %
Lp (1W/1m) 90.53 dB
Dd 17.00 cm
Sd 227.0 cm^2
GRS 2
fs 54.9 Hz
Qms 6.391
Qes 0.663
Qts 0.600
Fts 91.4
Mms 15.09 g
Cms 0.557 mm/N
Rms 0.814 kg/s
Vas 40.71 litres
Bl 7.652 Tm
Eta 0.98 %
Lp (1W/1m) 92.07 dB
Dd 17.00 cm
Sd 227.0 cm^2
GRS 3
fs 59.6 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
Eta 1.05 %
Lp (1W/1m) 92.38 dB
Dd 17.00 cm
Sd 227.0 cm^2
GRS 4
fs 55.1 Hz
Qms 6.885
Qes 0.636
Qts 0.583
Fts 94.6
Mms 15.74 g
Cms 0.530 mm/N
Rms 0.791 kg/s
Vas 38.75 litres
Bl 8.010 Tm
Eta 0.98 %
Lp (1W/1m) 92.07 dB
Dd 17.00 cm
Sd 227.0 cm^2
GRS 5
fs 61.2 Hz
Qms 6.794
Qes 0.747
Qts 0.673
Fts 91.0
Mms 16.48 g
Cms 0.410 mm/N
Rms 0.934 kg/s
Vas 29.94 litres
Bl 8.003 Tm
Eta 0.89 %
Lp (1W/1m) 91.64 dB
Dd 17.00 cm
Sd 227.0 cm^2
Hope that clarifies.
I really didn't average, just picked generally middle values from the respective samples. This is the raw output data from REW.
I'm planning on trying a few builds with these - probably both a MLTL and a cubic ported.
I really ought to ask santa for a reliable multimeter.
is the stamped frame now named the classic? didn't see a stamped frame on their web site.
Agreed!
FWIW, AFAIK virtually all nominally 8" drivers have a 206-209 cm^2 Sd, so combined with using a fixed Re for individual measurements will of course effect Vas, Qts accuracy, though with the latter dominating, it's better to have this the most accurate of the two specs plus any added series resistance [Qts'] to design with to ensure there's sufficient cab net volume [Vb] to allow some fine tuning without compromising bass response and/or resorting to using distortion increasing bass EQ.
All that said and short of remeasuring them and doing a few quick sims based on various average 'worst case' sets of your measured specs [calculates the largest cab tuned lowest]; using PE's BOFU measured specs yields the best overall T/S max flat [I use the term loosely] vented alignment, which for the WAF afflicted is by far the smallest cab tuned highest, so has the widest dynamic range to boot, making for a good baseline to work from or just build one of the many designs already posted here and elsewhere and fine tune the vent, stuffing as required to 'taste'.
GM
Technically correct and especially WRT the measured specs available so far, though as I just posted, these latest ones are at least in the 'ballpark' as a drop in replacement WRT the BOFU's standard default alignment whereas the others aren't acceptable IMNSHO, and others have already noted it falls short of the BOFU's wide BW performance, so seems a poor substitute at best.
GM
Yeah, I've seen this mentioned as well as the SQRT of the surround's inner and outer diameter, but have yet to see any pressure measurements done.
My info is from a now long gone Altec tech bulletin that was their update to the Bell Labs/W.E. anechoic measurements after they got their chamber built and since most frames, diaphragms, surrounds are still made to these many decades old designs [and in some cases, even the same tooling]; I see no reason why their Sd would change unless large whizzers adds to it or the lack of a dust cap reduces it acoustically, especially since so many manufacturers use these old standards.
Anyway, my SWAG is that this is for measuring when high excursions is the norm and T/S is measured at much higher power, which doesn't apply to most HIFI/HT apps except in the bass.
Regardless, since Qts dominates, getting it right takes precedence since Vas can be off quite a bit and still have no audible impact on the cab's performance. Still, it's nice to get the most accurate measurements now that it's cheap, quick, easy to get them.
GM
My info is from a now long gone Altec tech bulletin that was their update to the Bell Labs/W.E. anechoic measurements after they got their chamber built and since most frames, diaphragms, surrounds are still made to these many decades old designs [and in some cases, even the same tooling]; I see no reason why their Sd would change unless large whizzers adds to it or the lack of a dust cap reduces it acoustically, especially since so many manufacturers use these old standards.
Anyway, my SWAG is that this is for measuring when high excursions is the norm and T/S is measured at much higher power, which doesn't apply to most HIFI/HT apps except in the bass.
Regardless, since Qts dominates, getting it right takes precedence since Vas can be off quite a bit and still have no audible impact on the cab's performance. Still, it's nice to get the most accurate measurements now that it's cheap, quick, easy to get them.
GM
I know this is an old thread, where is the latest corrected dimensions for BOFU BIB?
I've added my most recent drawings (2007) of these to the list here: Frugal-phile | Box Library / Other
dave
dave
1772
You will be seriously missing out on the beauty of this driver:
Tang Band W8-1772, if you force it to do everything. No driver can do everything without serious compromises.
Use it as a wide-band mid range, augment the extreme top and bottom, and then sit back and smile.
You will be seriously missing out on the beauty of this driver:
Tang Band W8-1772, if you force it to do everything. No driver can do everything without serious compromises.
Use it as a wide-band mid range, augment the extreme top and bottom, and then sit back and smile.
Last edited by a moderator:
Use it as a wide-band mid range, augment the extreme top and bottom, and then sit back and smile.
As good as it is, IMO there are better wide-band mids for less money.
dave
Well, there really could be. With all the knowledge and experience you have,
I would certainly trust your opinion. The 1772, horn loaded, (like I use it)
has certain qualities that I find pleasing. Other listeners have commented on
a very small lack of detail somewhere in the mid range. I measured these and found a small semi-broad dip around the 1.0-1.6K Hz area. My ears are VERY sensitive to aggression/or/peaks in this area, so as always, this is a matter of personal taste.
For me, the 1808 (and by association the 1772) is a good example of a 'full range' driver that doesn't require a helper woofer or tweeter to sound very good. They require special cabinets but can produce a full range sound. I consider the older Fostex 168z (with whizzer) to have similar capabilities (and by association the Fostex 208z). There are others but I've not heard them.
As for making them do more than they should, I'm not sure I agree with that. As long as you keep the volume at reasonable levels these drivers can fill a room with wonderful full range sound. If you want very high volumes I'd suggest removing bass duties for all of these drivers.
As for making them do more than they should, I'm not sure I agree with that. As long as you keep the volume at reasonable levels these drivers can fill a room with wonderful full range sound. If you want very high volumes I'd suggest removing bass duties for all of these drivers.
Finally made BOFU BIB's
I embarrassed to write this after more than 3 years but I finally built a set of the original BOFU BIB's (with Mark Audio tweeter) and just want to compliment all those involved in the development of them.
These are great! Listening to them through an old Denon integrated amp and I am very happy.
The only negative is their low WAF. Luckily for me my wife likes their sound too so is prepared to put up with their size!
Thanks again!!
I embarrassed to write this after more than 3 years but I finally built a set of the original BOFU BIB's (with Mark Audio tweeter) and just want to compliment all those involved in the development of them.
These are great! Listening to them through an old Denon integrated amp and I am very happy.
The only negative is their low WAF. Luckily for me my wife likes their sound too so is prepared to put up with their size!
Thanks again!!
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.