Realistic Nova 8b Rebuild & Crossover Re-Design

[tiga]

Yes (sort of). I have a pair of the Optimus 5's (not B) and they are identical to the Nova 8 (not B) except for the grill. The cabinets on the 5's were in bad shape and the tweeters were toast. I patched up the cabinets and painted them black, re-capped the crossover and replaced the tweeter with a Vifa dome. The results were quite good.

I now have a set of Nova 8's (not B) that I will be putting through VL's mods. I've acquired two B model tweeters and all of the crossover components. I plan on using the non-B woofers for now and we'll see how it works out. I expect they'll do just fine.

Has anyone attempted some mods with their Nova 8s? I know the thread is more oriented toward the Nova 8B / Optimus 5B.

 

[speedle]

I'm looking forward to your results with that, tiga, because that's about what I'm starting out with.

 

[tiga]

I'm looking forward to your results with that, tiga, because that's about what I'm starting out with.

I'll keep posting my progress - I just cut the mounting boards for the crossover. I checked your flckr page - you've accumulated some nice stuff! How do you like the Pioneer sx-838? (sorry to get off topic).

 

[Copa1934]

Nova 8b and Optimus 5b have same drivers...

I know this has been touched on, but there was no definitive answer/response I could find in the post. I took images of my 5b drivers and the part numbers are identical to those posted by VL. What I haven't done, yet, is compared the crossovers, I can only suspect these were different, i.e. the 8b may have been a better design and might account for the higher retail price (both speakers were available at the same time briefly). Of course, when RS phased out the 8b maybe there was too much inventory left so both were marketed till the 8b speakers were depleted. Who knows.

Also, there is a notable difference in the labels on the drivers, but the part numbers do match.

So, anyone with 5b speakers wondering about performing this upgrade can now go for it! I know I will.

 

[speedle]

I'll keep posting my progress - I just cut the mounting boards for the crossover. I checked your flckr page - you've accumulated some nice stuff! How do you like the Pioneer sx-838? (sorry to get off topic).

Well, I haven't had all that stuff at one time mind you. I buy what I like and sell what I get tired of, mostly. As for the Pioneer, I'm listening to it now, happily. It's an Echowars/Punker X effort that's darn near perfect.

As for the the Optimus, I'm short one midrange! Still looking for one though.

 

[geiman]

When I took a close look at the mids & tweeters on my Optimus 5b's, I saw something I hadn't seen before. The surrounds are some kind of fine mesh. You can see right through it. I was just wondering does this help or hurt the SQ? Seeing as the mids & tweets have open baskets, I think I'll try inserting some felt or lambs wool in there and see how it affects the sound. Also the mids & tweets use plastic isolation cups behind the drivers. I wonder what kind of resonances are going on there? There are other things I see done differently than in modern TOTL speakers. Things like the woofer being recessed and the high freq drivers not being flush mounted at all.

Just wondering if there is more performance to be had from these speakers beyond a X-O upgrade is all.

The surrounds are silk.

 

[RickeyM]

Silk surrounds. Could this be the secret to great sound (once the crossover gets outta the way)? Well, I've got my x-o parts from Parts Express. Now to make some time for the mod...

 

[RickeyM]

I noticed something while doing the crossover mods on my Optimus 5B's :scratch2: . I looked at the stock crossovers and went back to check the pics VL posted of the Nova 8B's .
The crossover construction and layout is different between the 5b and 8b "cousins". The drivers and cabs are the same, but it looks like they saved a few bucks on the 5b crossovers.

Well, back to work :thmbsp:

 

[RickeyM]

Optimus 5B continued...

Whenever I do a project like this, I tend to add a few touches as I go along. I used hot glue to form a seal at the bottom of the cups for the mids & tweeters. Then I made some gaskets to go under the flanges of these cups to give the enclosures an even better seal.

Since they won't be used, I sealed up the hole in the RCA jacks on the speaker terminal plates as well. I was going to replace the stock terminal plates, but I found a way to keep it simple. The gold-plated binding posts from the Optimus LX-5's screw right in, in place of the factory screws.

The thin (and old) gasket on the woofer is being replaced too. I also mounted the crossover components on pieces of wood to give me plenty of room to work. One piece for the mid & tweeter components, one piece for the woofer's components.

I vacuumed everything thoroughly when I bagged the fiberglass. Here's the "Inspector" checking my work :thmbsp:

 

[tmccullough]

I vacuumed everything thoroughly when I bagged the fiberglass. Here's the "Inspector" checking my work :thmbsp:

Cats love to get into everything and anything, don't they?

 

[tiga]

I assembled one crossover last night. This was my first crossover build but following greenmark59's pictures it made it pretty easy. I'm going to try to install it in one of the speakers tonight. Like an idiot I didn't order enough caps to make the 1.75uf's for the second crossover so I need to order those.

Any issues/tips connecting to the binding posts?

 

[RickeyM]

Use binding posts out of a terminal cup. They have small shafts that you can use to replace the original screws. If necessary, you may need to drill out the original threads a little and use the nut on the backside to lock the terminal in place. By using binding posts attached in the original positions, I was able to use the original solder tabs for the new wiring.

 

[RickeyM]

HEY, does this look right??

I did the new crossover for my Optimus 5B (per the VL diagram) and listened to the results. Well, it sounded different than the original, but there was no WOW. The bass was fuller & deeper, but I attributed that to better sealing of the cab. The mids & highs didn't really sound like a speaker "transformed".
Later, I happened to come across a schematic for a three way speaker and noticed that the mid-range (bandpass) network for the VL Nova 8b mod didn't make sense.

What did make sense was having the 2.7uF cap as the first component, with the 2.0mH inductor as the shunt to ground after that, followed by the smaller 1.74uF cap in series and the 1.0mH inductor as the shunt to ground after that. I pulled the mid/tweeter x-o board from the speaker, re-wired it and put it back in. Now came the wow! The highs were cleaner and more extended and the mids were way more defined.

My question to anybody who's done the mod is, did you follow the VL schematic for the midranges or did you use a "textbook" circuit?

Any comments, opinions, observations, flames, hate mail, threats

No dis to VL, but the bandpass section of that x-over doesn't look or sound right. I've got my other speakers x-over done and as soon as I get the work on the cabinets done, I'm sure I'll have a pair of VERY good sounding speakers :thmbsp:

 

[tiga]

Could you post a picture of your crossover change? (not that I'll understand it any better from the picture).

I did the new crossover for my Optimus 5B (per the VL diagram) and listened to the results. Well, it sounded different than the original, but there was no WOW. The bass was fuller & deeper, but I attributed that to better sealing of the cab. The mids & highs didn't really sound like a speaker "transformed".
Later, I happened to come across a schematic for a three way speaker and noticed that the mid-range (bandpass) network for the VL Nova 8b mod didn't make sense.

What did make sense was having the 2.7uF cap as the first component, with the 2.0mH inductor as the shunt to ground after that, followed by the smaller 1.74uF cap in series and the 1.0mH inductor as the shunt to ground after that. I pulled the mid/tweeter x-o board from the speaker, re-wired it and put it back in. Now came the wow! The highs were cleaner and more extended and the mids were way more defined.

My question to anybody who's done the mod is, did you follow the VL schematic for the midranges or did you use a "textbook" circuit?

Any comments, opinions, observations, flames, hate mail, threats

No dis to VL, but the bandpass section of that x-over doesn't look or sound right. I've got my other speakers x-over done and as soon as I get the work on the cabinets done, I'm sure I'll have a pair of VERY good sounding speakers :thmbsp:

 

[Copa1934]

Geez, glad I haven't taken the plunge yet. I'll have to wait to here more on this. I follow what you're saying, though I don't fully understand the "engineering" aspects of it. Is it possible you have different drivers than what are stock (and presumeably correct per VL)? I've confirmed my 5b's to have the same drivers as VL's system, just haven't checked the original xover to see if it's at all similar to the 8b system. One other person posted info that the xover was the only difference between the models. Having worked for RS that doesn't surprise me in the least.

Sure would be nice if VL were still around, but haven't seen a post in almost 2 months now. One can only hope. Be a shame if this thread and the Mach thread are layed to rest after all this effort.

 

[RickeyM]

Hth

Rather than post a pic of my x-over, which could be confusing due to the layout, I found a 3-way-second order diagram that should be easier to understand.

Paying attention to the midrange circuit and ignoring the parts list and component values (they're for some other speaker):

C2- 2.7uf
L2- 2.0mH
L3- 1.0mH
C3- 1.74uF

 

[RickeyM]

The only difference in the mids & tweeters in mine is that the specs on the backs of the magnets are on labels rather than printed directly on the back of the drivers. The part numbers are the same.

In a x-over network for a mid, the L3 inductor's job is to filter out the highs from the mid driver(s), letting the tweeter take over for that.

Since I'm doing the other speaker tonight, I'll show pics on how I sealed up the cabinets and the stuffing I replaced the fiberglass with :thmbsp:

 

[speedle]

Maybe this is a stupid question, but did you wire your two 4 ohm mids in series then? And otherwise then, that's a stock 2nd order bandpass network for these mids?

 

[RickeyM]

The original 4-ohm mids are wired in series. I don't know what the designer of the crossover shown in the schematic originally shown in post #5 was shootin' for, but that's not a second order bandpass for the mid.

 

[videolady201]

Nova 8b Bandpass Section

I did the new crossover for my Optimus 5B (per the VL diagram) and listened to the results. Well, it sounded different than the original, but there was no WOW. The bass was fuller & deeper, but I attributed that to better sealing of the cab. The mids & highs didn't really sound like a speaker "transformed".
Later, I happened to come across a schematic for a three way speaker and noticed that the mid-range (bandpass) network for the VL Nova 8b mod didn't make sense.

What did make sense was having the 2.7uF cap as the first component, with the 2.0mH inductor as the shunt to ground after that, followed by the smaller 1.74uF cap in series and the 1.0mH inductor as the shunt to ground after that. I pulled the mid/tweeter x-o board from the speaker, re-wired it and put it back in. Now came the wow! The highs were cleaner and more extended and the mids were way more defined.

My question to anybody who's done the mod is, did you follow the VL schematic for the midranges or did you use a "textbook" circuit?

Any comments, opinions, observations, flames, hate mail, threats

No dis to VL, but the bandpass section of that x-over doesn't look or sound right. I've got my other speakers x-over done and as soon as I get the work on the cabinets done, I'm sure I'll have a pair of VERY good sounding speakers :thmbsp:

Hello all, been down due to health issues. Now back to the speaker. The diagram I posted is correct and is what you should use unless your drivers are not the same as I listed on the first page of this thread. You stated the bandpass section didn't make sense. What part do you not understand. These values are not a guess but the result of many hours of testing and modeling the system. Did you also NOTE that the mid and tweeter in the new crossover are to be wired out of phase? :scratch2: