View Full Version : Realistic Nova 8 Crossover Mod - Roadblock


Rockyhill
12-28-2010, 05:28 PM
I read with great excitement the thread for the Nova 8 crossover mod. http://www.audiokarma.org/forums/showthread.php?t=307141 When I opened up my 8's yesterday {non-B model} I found the tweeter is a 0705Ac, 4 ohms, which appears to be the same as what's in the Optimus 5. Other's made the same discovery, according to the thread. The correct tweeter for this mod is 0725Ac - 8 ohms.

There was a reference by the OP videolady201 for a replacement:

Based on what I have found, Radio Shack shows they still have replacement tweeters for the Nova 8b. :yes: The information to contact them is listed below:

To order parts call Radio Shack Order Line 1-800-843-7422
Catalog #: 11083698 SPEAKER,TWEETER NOVA 8B, 8 OHM L.T
New Part #: SP0266


I called Rat Shack tool free number and they could not locate either part number. I called my local RS store who confirmed that as well.

Can anyone provide the correct replacement part number or equivilent that will work with this mod?

Alternatively, can the crossover be modified to accommodate the 4 ohm driver?

Thanks all.

absolve2525
12-29-2010, 12:35 AM
Parts Express carries an 8 ohm Phenolic tweeter that sounds very good; from what I recall in the crossover thread, you can use this driver instead. I have a pair of NOVA 8 too, with the 4 ohm tweeter. It would be interesting to know if our 4 ohm version tweeter could be integrated into the new crossover, but I dont think think anyone has tried.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=270-252

Copa1934
12-29-2010, 12:38 AM
It will alter the crossover since it's balanced for an 8-ohm load. Popping a resistor in, I believe, would help compensate.

Rockyhill
12-29-2010, 06:56 AM
Parts Express carries an 8 ohm Phenolic tweeter that sounds very good; from what I recall in the crossover thread, you can use this driver instead. I have a pair of NOVA 8 too, with the 4 ohm tweeter. It would be interesting to know if our 4 ohm version tweeter could be integrated into the new crossover, but I dont think think anyone has tried.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=270-252

Thanks! That looks like a good candidate. I'll check with ohenry who mentioned the parts-express replacement to see how his mod went.

Renzor213
12-29-2010, 08:07 AM
If someone replaced the original 8 ohm tweeter's with 4 ohm job's without changing the crossover capapcitor's, that's kinda like a really huge deal. If the original crossover design was 5kz into 8 ohm's, will now be 10khz into 4 ohm's, and probably play much louder. Simplest solution would be adding a 4 ohm non inductive several watt resistor inline between the capacitor and tweeeter. You need to do something soon, as the speaker's probably sound pretty crappy now. Also, my brother used to manage Radio Shack store's and sometime's helped him out at night. Music was alway's going, and alway's the 8B's.

Rockyhill
12-29-2010, 10:44 AM
If someone replaced the original 8 ohm tweeter's with 4 ohm job's without changing the crossover capapcitor's, that's kinda like a really huge deal. If the original crossover design was 5kz into 8 ohm's, will now be 10khz into 4 ohm's, and probably play much louder. Simplest solution would be adding a 4 ohm non inductive several watt resistor inline between the capacitor and tweeeter. You need to do something soon, as the speaker's probably sound pretty crappy now. Also, my brother used to manage Radio Shack store's and sometime's helped him out at night. Music was alway's going, and alway's the 8B's.

These are Nova 8's, not the B model. You may know better than me but I think the 8's had different tweets and hence different crossover (assuming that). I plan to replace the 4 ohm tweet with the parts-express 270-252 and proceed with the mod. The mids are the same as the 8B.

Renzor213
12-29-2010, 11:56 AM
These are Nova 8's, not the B model. You may know better than me but I think the 8's had different tweets and hence different crossover (assuming that). I plan to replace the 4 ohm tweet with the parts-express 270-252 and proceed with the mod. The mids are the same as the 8B.Nope, don't know more about your speaker's than you, but been around speaker building awhile, and you're definitely doing the right thing with the 8 ohm tweeter switch. Part's Express is a good place, and buy from them often myself. Not sure of the Nova 8 and 8B differences, but recall playing with the switcher in my brother's stores, and the 8B's are pretty much where it stayed. Good luck with the tweeter servicing, as think you're gonna like it.

RickeyM
12-29-2010, 12:05 PM
In the Nova 8b/Optimus 5b mod, there is a 10-ohm resistor in series with the tweeter. Would it be a simple matter to increase the resistance to 14-ohms for use with the 4-ohm tweet?

Rockyhill
01-06-2011, 04:49 PM
Just received the replacement tweets and mod components. Will do one speaker this weekend. I'm excited to do a side by side before & after comparison.

Copa1934
01-06-2011, 05:17 PM
Just received the replacement tweets and mod components. Will do one speaker this weekend. I'm excited to do a side by side before & after comparison.
Cool, just remember to run something that is not stereo or play in mono so each speaker receives the same material, otherwise comparison will be very difficult. Can't wait to read the results.

Rockyhill
01-06-2011, 07:15 PM
Cool, just remember to run something that is not stereo or play in mono so each speaker receives the same material, otherwise comparison will be very difficult. Can't wait to read the results.

Will do. I have "Meet The Beatles" and other ancient LP's in mono for testing.

aabottom
02-19-2011, 12:36 PM
Will do. I have "Meet The Beatles" and other ancient LP's in mono for testing.
So, ..., any results? :lurk:

Rockyhill
02-19-2011, 05:07 PM
Both have been complete for a few weeks now. The Nova 8 is a much improved speaker with this mod. Over all, it's fuller sounding. Highs are vastly improved. Mids are very satisfying.

As I posted in the original thread, I wouldn't seek out these speakers with the intention of modding, but since I had them already I'm glad I made the upgrade.

These are in my bedroom, and honestly, much of the listening I do is radio [sports talk and NPR]. Also classical and jazz over the air.

I just received a Sony XDRF1HD Tuner. I can now pull in a distant station and a local low power college station for jazz that sound so much better due to the tuner and the modded 8's.

If you have 8's or 8B's, do the mod. You won't regret it.