Nova 8B Tweeter Question...

[jeep jones]

Disclaimer up front. Still learning and not a speaker guru...yet.

Got a Goodwill set of Nova 8B's for 26 bucks. Cabinets are in excellent condition and all of the drivers are at nominal in one cabinet. However, the other cabinet has two drivers that don't even register on the ohm meter. One is the tweeter and the other is the woofer. I've got a like for like replacement woofer coming my way, but can only find like for like replacements for the midrange, not the tweeter. The midrange are 4 ohm, while the tweeter is 8 ohm. Would I need to add anything extra in the way of resistors to use a midrange in the tweeter location? They look identical from the face of the speaker, just smaller magnet on the tweeter. Want to keep the overall ohm rating for the speaker around 8 as per original spec. How much would this impact performance? Losing some crispness with this approach?

Any information would be appreciated!

 

[Mac Lessig]

I have the tweeters. They were pulled from a working set of the Nova 8B's........ The Cabs were seriously destroyed but the drivers are all ok

 

[jeep jones]

I have the tweeters. They were pulled from a working set of the Nova 8B's........ The Cabs were seriously destroyed but the drivers are all ok

Thanks Mac. Sent you a PM.

 

[jeep jones]

Anyone else have input on an additional resistor? Still curious as to that configuration.

 

[Stuart Pedaso]

The midrange are 4 ohm, while the tweeter is 8 ohm. Would I need to add anything extra in the way of resistors to use a midrange in the tweeter location?

Anyone else have input on an additional resistor? Still curious as to that configuration.

If it's only a matter of series resistors then just pop a mid in there and try it. Resistors are already in place. Regard the schematic below:



The identical mid and tweeter level networks are just a pair of resistors switched in or out to put 2, 1 or none in series with the drivers. A 4Ω mid connected to the tweeter filter will have 4Ω in series in the "normal" position or 10Ω in series in the "low" position. You can expect this to vary output level attenuation while shifting crossover point somewhat. Though the high pass frequency will already shift a lot by using the existing cap with a 4Ω driver. Don't expect added series resistance to influence the top frequencies this mid driver can reproduce.

And you can already hear its top end. Look at the midrange filter in the schematic. The cap and coil aren't configured as a band-pass filter, but rather as a 2nd order high pass filter. The mids run free at the top end and reproduce all that they're able (forget about the "1-7kHz" printed on the terminal plate -- videolady found mids and tweets sharing quite a lot a bandwidth and designed a celebrated crossover mod, in part, to address this issue).

So if you want to know if the midrange driver can replace a tweeter, just disconnect the tweeter in your working speaker, play some music and have a listen. If the mids can reach the highs they will, because there's nothing inside the box to stop them.

 

[Stuart Pedaso]

Nice speakers. I picked up a pair of Optimus 5b off the road side in a rainstorm during clean up week. they were beat to rat turds and had one missing mid. sourced a new one off the net and sanded them down and ended up staining them to match my girlfriend's maroon colored furniture...gave them to her with a Sansui AU101/TU505 and dang they sound good! Congrats and enjoy!!

They look fabulous too!
That was a very inspiring thread.

 

[jeep jones]

Awesome info Stuart, Thanks!