Realistic Optimus 9- has anybody actually heard these??
- Thread starter Adam S
- Start date
Thanks! It's actually part of the midrange bandpass filter (wired parallel to 0.1mH coil) connected to the midrange potentiometer. I've updated the images.
Thanks. Your pics also confirm that the tweeters [oops! -- make that "mids"] are indeed wired in series. I've updated the images in post 33.
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One of videolady's major design concerns seems to have been addressing the large amount of bandwidth shared between the drivers. I've not heard the mod, though by all accounts it's claimed to be impressive.
A single symbol might've been used to represent the total speaker portion of the midrange circuit. It is labeled with the plural "midranges," though perhaps only in reference to the switch. Just guessing ...
Lavane
Lunatic Member
Ah, ok, the mids are in series.
Oops, ... stated it wrong in post #42. Your post prompted the alert. Thanks!
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TomBig58
Super Member
Hey Adam we must be neighbors. I saw those too and thought it was a nice price for what they are but I have way too many speakers/projects already. Good luck with the refurb I hope they work out for you.
For what it's worth I also think 19" wide by 9" deep is not the easiest fit in a setup. More typical though for speakers of that vintage.
For what it's worth I also think 19" wide by 9" deep is not the easiest fit in a setup. More typical though for speakers of that vintage.
HTHMAN
Super Member
The Boston Acoustics A-series were very thin and wide compared to other speakers of the era. The design was supposed to allow them to be placed against a wall.
Well give us the rundown...do you like them?
Adam S
Lunatic Member
Hi Tom- I have too many speakers myself and have been parted with several pairs of nice bookshelfs lately but since I've never saw a pair of these for sale and knowing all the similarities with the 8b I know these may be excellent after a recap.I ordered the replacements yesterday and look forward to hearing them after they're right. The bass is tight and accurate but the mids are high and thin and the tweeter isn't as "sparkly" as I think it will be after the poly film caps are installed and also convert the speaker terminals to binding post and delete the rca connectors. I'm really looking forward to hearing these big boys.They will also benefit from stands at some point. I'll be posting my progress and opinions next week.
BTW, I live on the edge of Lakeview/Lincoln Park on Burling St.
Adam S
Lunatic Member
Yes, have you listened to them when they were young with fresh caps? Or have you refreshed them and if so what do you think?
TomBig58
Super Member
I'm around Belmont and Racine down the street from Saturday Audio. I once had a pair of Nova 7Bs that were very musical and some Optimus T-120 that I really liked. I don't mind hanging on to the smaller bookshelf models now but I have a few pair of larger speakers that just won't make it back into rotation except for nostalgia reasons. We should get together sometime.
TomBig58
Super Member
Based on your signature they had some pretty stiff competition. I'm surprised you still have them around.
Nice looking set, too.
Noticed that your woofers appear to have convex rather than concave surround rolls. Is that just optical illusion? Have they been re-foamed?
Out of curiosity, what value cap did you order for the tweeter?
Haven't seen that cap identified for Optimus-9 yet in this thread. Wondering if it's 6.8uF as used in Optimus-5.
So far, other than 20 Ohm vs 10 Ohm pots, this looks the same as Optimus-5 / Nova-8 crossovers.
Which is odd because 5 / 8 cross at 5kHz between mids and tweeter, whereas 9 crosses at 7kHz. Though the midrange total impedance will be different, and the tweeters may have different impedance curves. Then there's that wire-wound resistor in the midrange filter -- 10 Ohms for 5 / 8; might be different for 9.
That brings up an interesting aspect of Optimus-9's midrange control. Rather than the usual "high" & "low," its labeling references the character of the wall behind it.
Maybe the wide & shallow cabinet design's purpose in this case is to maximize width and proximity of the midrange array for broader area of rear reflection. The factory probably published recommendations for optimum distance from the rear wall. Sure would be nice to find an owner's manual ...
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Adam S
Lunatic Member
Both small caps are 3.3uf on my board..Out of curiosity, what value cap did you order for the tweeter?
View attachment 1870235
Haven't seen that cap identified for Optimus-9 yet in this thread. Wondering if it's 6.8uF as used in Optimus-5.
So far, other than 20 Ohm vs 10 Ohm pots, this looks the same as Optimus-5 / Nova-8 crossovers.
Which is odd because 5 / 8 cross at 5kHz between mids and tweeter, whereas 9 crosses at 7kHz. Though the midrange total impedance will be different, and the tweeters may have different impedance curves. Then there's that wire-wound resistor in the midrange filter -- 10 Ohms for 5 / 8; might be different for 9.
Thanks. That makes sense -- with higher crossover frequency one would expect lower value cap (schematic updated).
Adam S
Lunatic Member
Yea Tom we should- hopefully things start getting better around here sooner than later.