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Realistic Nova 8b Rebuild & Crossover Re-Design

ohenry said:
FWIW, the tweeters in my friend's Nova 8's were labeled 705Ac, Tweeter, 4 ohms.

PS- Measured at 3.9 ohms as well.
Click to expand...

These were also in my Optimus 5's.

I wonder if the 5's/8's used the same crossover as the 5B/8B? I think someone recently posted their cap values for their 8B's and they were the same as my 5's.
 
I'm in the process of replacing the old caps on the mids and highs in my Nova 8s - I had some extra polyprop caps from other projects available. The cap on the tweeter is 3.3 uf and the mids have a 6.8. The woofer has a 33uf cap - I dont have any that big at the moment, so I'll have to get back the that. Has anyone tried running the woofer full range? I have some old Utahs that are somewhat similar to this speaker - they are sealed, with a 12", 6" mid, and cone tweeters. The tweeters went bad on those, so I'm going to substitute some old Foster horns whenever I get back to that project. Anyhow, the woof runs full range on those. Looking at the rest of the Nova 8 crossover, there is .1mh coil, a 1 mh coil, a 10hm resistor, and the two level controls.
 
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WOW - replacing the caps on the mids and tweet has made a HUGE difference! I also applied adhesive gasket strip material (parts express sells it by a big roll) around the woofer opening before replacing the woofers. Bass is much improved!
 
The weak link in this project is the tweeters. Many are blown. A good suitable replacement that is currently available would be most helpful.

videolady201 said:
I have included pictures of the back of the Tweeter & Mid Range so you can confirm that your drivers are the same units. The 8bs were known for blowing tweeters as they only had a first order crossover on them. Check your tweeter to be sure it is not blown or damaged. It should read right at 7 ohms on your voltmeter. The mids were not as bad to blow because two units split the load as they are hooked in series. The two together should also be right around 7 ohms on a voltmeter.
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I don't have the expertise or equipment to choose the perfect replacement, but there are certainly many tweeters available for an 8 ohm application with about 88 dB/w/m sensitivity.

Are any of these worth considering?


http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-870

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=275-070

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=275-075

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=275-076

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=275-078

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=276-604

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=276-610

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=277-010

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=277-080

Thanks!
//Smorgy
 
I have a pair of those Parts Express phenolics - I havent been able to play around with them yet though. I planned on using them as replacements tweeters in some Kenwood LS speakers. The Kenwood version of this tweeter sounds very good, and the parts express model is a very heavy duty tweeter. It looks like it would fit in my Nova 8s, barely - I think the magnet just fits. I didnt actually stick it in there though. The connectors are too large for the stock cable hookups, so those would have to be swapped out.
 
Tweeter Info

absolve2525 said:
I have a pair of those Parts Express phenolics - I havent been able to play around with them yet though. I planned on using them as replacements tweeters in some Kenwood LS speakers. The Kenwood version of this tweeter sounds very good, and the parts express model is a very heavy duty tweeter. It looks like it would fit in my Nova 8s, barely - I think the magnet just fits. I didnt actually stick it in there though. The connectors are too large for the stock cable hookups, so those would have to be swapped out.
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I have a pair as well. They are very nice and with the crossover I get extended sweeps up to 20khz. The crossover has a boost above 15khz because the original driver rolled off the same. They are your best bet if you don't have the originals.
 
videolady201 said:
I have a pair as well. They are very nice and with the crossover I get extended sweeps up to 20khz. The crossover has a boost above 15khz because the original driver rolled off the same. They are your best bet if you don't have the originals.
Click to expand...

Good enough for me, I ordered a pair. I wouldn't have thought them good enough with thier range, but you've convinced me.

If anyone cares, the 4 ohm version is a smokin deal right now too . . .

//Smorgy
 
I put the 4 ohm version of the phenolic ring tweeter in my friend's Nova 8's (he didn't want the new crossover). They did sound really good with the stock set up.

One thing to be mindful of when ordering these. Their magnets do fit into the plastic housing that encloses the Nova 8 tweeter; however, as mentioned earlier, the posts do interfere.

I cut a notch in the baffle to accommodate the posts. Then I cut slots into the plastic housing to allow the posts to protrude through the housing to the outside. I bent the posts up to near 90 degrees to poke through the housing. I sealed the housing post slits with silicone. The wire connections where then made outside of the housing and the whole assembly was slid into the baffle.

So... be prepared to make some minor modifications, but it'll be worth it. :thmbsp:
 
Tweeter Info

ohenry said:
I put the 4 ohm version of the phenolic ring tweeter in my friend's Nova 8's (he didn't want the new crossover). They did sound really good with the stock set up.

One thing to be mindful of when ordering these. Their magnets do fit into the plastic housing that encloses the Nova 8 tweeter; however, as mentioned earlier, the posts do interfere.

I cut a notch in the baffle to accommodate the posts. Then I cut slots into the plastic housing to allow the posts to protrude through the housing to the outside. I bent the posts up to near 90 degrees to poke through the housing. I sealed the housing post slits with silicone. The wire connections where then made outside of the housing and the whole assembly was slid into the baffle.

So... be prepared to make some minor modifications, but it'll be worth it. :thmbsp:
Click to expand...

Are these units not sealed on the back?? My 8 ohm version are. If so, leave the plastic cup out. No need to use it and try to cut slots and wire through them. They are there so the woofer didn't knock the cones out of the original mid & tweeters as they were open back units. The plastic cups sealed off the air pressure from the woofer. If a sealed back driver is used, the cups can be left out!
 
videolady201 said:
Are these units not sealed on the back?? My 8 ohm version are. If so, leave the plastic cup out. No need to use it and try to cut slots and wire through them. They are there so the woofer didn't knock the cones out of the original mid & tweeters as they were open back units. The plastic cups sealed off the air pressure from the woofer. If a sealed back driver is used, the cups can be left out!
Click to expand...

You're right! I was in the mode of going great lengths to preserve my friends speakers with all the parts in case he wanted to go backwards at some point.

Problem is, I totally forgot that's why I used the cups, not for necessity. Some days I completely embarrass myself.

So... nevermind! :stupid:
 
The bafle board must be thinner on the "B" speakers. It is about 1/2" thick on my Optimus 5 speakers. No way possible to bend those tangs down on the phenolic ring tweeters and connect the wires. The opening has to be notched. And...if you don't use the cups, then you still need a gasket since these are sealed box speakers. Which brings me to my question.

The Correct Radio Shack Tweeters arrived today. A BIG Thank You to RMEADE for sending those to me!! When I set them on the counter to measure the resistance, I noticed that I could see through the surround. (see pic)

It appears to be a cloth surround, but no longer sealed. For woofers with this condition (like KLH woofers) I use Permatex Super High Tack. Light, thin coating. This has been suggested elsewhere in speaker threads. It never hardens. No need to slather it on, just a thin coat.

My question is: Should I use the Super High Tack on these tweeters to seal them? (My guess is yes) I thought I should ask before I did it, just in case.

As I looked more closely at ALL of the mids and tweeters, they are ALL like this.

Thanks!
//Smorgy
 

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Tweeter/Mid Surround Coatings?

Smorgy said:
My question is: Should I use the Super High Tack on these tweeters to seal them? (My guess is yes) I thought I should ask before I did it, just in case.
Click to expand...


The mids & tweeters don't displace like a woofer. It will make no difference in performance if you coat them unless you put to much on them. If you do put anything other than the thinnest coating, you could reduce the compliance of the unit which in the mid range drivers may become audible. Also, if you use anything that stays sticky, as it attracts dust, lint, etc., the mass and compliance will both change. If I were to coat them, I would use the thinnest coat possible, (as you have all ready said to do), with something that stays pliable but will dry to a none sticky state. The same glue used to repair surrounds would be great but I don't know if it will stick to the factory coating, if any is left on them. My pair worked fine with the surround glue but they had been in the sun by the previous owner and all the factory coatings had got hot and ran off the drivers and down onto the frame and face of the cabinet.
 
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Well, I gave them a light coat. It was too much of an air leak to just leave it. So, finally, these are complete, or as complete as Optimus 5 (sans B) can be. Correct tweeters (Thanks RMEADE!), upgraded crossover. Now for the fun part - getting a chance to listen to them. :music:

What is the name for your crossover? The VL201 ?

Thanks for all you help! I'll leave some feedback after I listen for a few days.
//Smorgy
 
What is the verdict Smorgy? Are you going to try those parts-express phenolics you bought also? I'm very curious since we have the same speaker for the most part!
 
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Smorgy - did you leave the stock Optimus 5 woofers in there or did you change them out? Thanks.

Smorgy said:
Well, I gave them a light coat. It was too much of an air leak to just leave it. So, finally, these are complete, or as complete as Optimus 5 (sans B) can be. Correct tweeters (Thanks RMEADE!), upgraded crossover. Now for the fun part - getting a chance to listen to them. :music:

What is the name for your crossover? The VL201 ?

Thanks for all you help! I'll leave some feedback after I listen for a few days.
//Smorgy
Click to expand...
 
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