Realistic Nova 8b Rebuild & Crossover Re-Design

[RickeyM]

So stuffing it completely is the way to go?

The stuff I got filled the cabs with sixteen ounces. Moderately stuffed, not tightly packed. Very nice bass. Deep, clean & strong. Not boomy, muddy or bloated at all. Try using 16-20oz per speaker and see how it sounds.

 

[videolady201]

Mid Connection

Thanks for the kind works VL. Another quick question - does it matter if the Mid+ connection goes where I have it marked or should it be at the (-) terminal?

Sorry for the late reply. Where you have it marked is fine!

 

[tiga]

Woofer repair question

Both crossovers are complete and installed. Early today while I was buttoning up the second speaker I decided to bring out the pair of 8B woofers I have. Only one is working so my plan was to use the non-B woofers until I picked up another one to complete the pair. I thought I'd take another look at the non-working woofer and see if I could troubleshoot the issue.

Anyway I connected the non-working woofer and as expected - got nothing. I moved one of the wires that goes from the connector to inside the cone and I got sound! The short seems to be at where the wire enters the cone. Is this fixable? If I removed the dustcap could I see this wire and do a repair?
Thanks!

Tiga

 

[Copa1934]

"...inside the cone..."? If the lead is damaged, which can happen, they can be replaced. Just a matter of cutting or desoldering the leads and replacing them.

Have you actually tried touching the leads at different points behind the cone? If you haven't I'd start there. If there is a break, caused by flexing of the lead, you might be able to simply clip out that section and replace with new leads. If you find that's the issue post it, then PM me with your address and I'll send you a length of lead.

Some people will suggest re-soldering the break, but solder flows and will stiffen more of the lead limiting it's flexibility and ultimately leading to another break. Not worth it.

 

[tiga]

I tried touching the speaker wire all the way down the lead and I get nothing until I'm touching it where it enters the cone. It looks like there is a very small metal ring surrounding the wire where it enters the cone (barely visible). If I touch this I get sound.

Would putting some solder on this point (where the lead enters the cone) be a possible fix or do I risk melting the cone? Any other ideas? Thank you!

 

[tiga]

While I work on my "b" woofers I buttoned everything else up with my non-b woofers and I'm giving them a listen. They sound great! In fact the more I play them the better they sound. They are currently hooked up to my Sansui 5500 and I'm switching back and forth between some Norah Jones and the Steeler game.

I first played them with the loudness off and the tone controls flat. They sounded good but even better with the loudness contour on. I just gave the treble a two-click uptick and I like that even better. Seems like the imaging just went up to another level.

Even though these are the non-B woofers the bass is great. It kind of makes me wonder how much improvement, if any, I'll get with the B-woofers.

Now playing some Beta Band - bass is punchy and tight.

I can't wait to connect these to my Pilot tube amp this week!

This has been a fun project and I'm learning a great deal. Thanks to VL for your efforts and thanks to everyone in this thread who helped me along.

 

[Copa1934]

No worries on the cone. As long as you don't keep the iron directly on the cone or touching the cone too long no issues. Worst case is you might burn the cone. If you have the speaker upside down and or angled so that you can get a drip of solder to drop on the bad spot, you can then apply heat to that spot to get the solder to flow. Can't let the solder sit too long, need to apply the iron right after the solder drops so as to help conduct heat to the lead. If the lead has plenty of flex, it's possible someone clipped there system or simply over-drove their system causing the cone to tug on the lead and ultimately breaking it.

 

[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 on the mid/tweet cones are silk.

 

[RickeyM]

I know this is a long thread but....

The surrounds on the mid/tweet cones are silk.

Um geiman, you already tipped me to this. Since you brought it up again, is there anything that we can re-dope the surrounds with? Whatever was there originally has seemed to melt (?) and run onto the paper cones of the mids/tweets. As good as the mids & tweeters sound on these speakers, I wonder if re-doping the surrounds to further isolate the front and rear sound waves of the drivers would improve the sound?
Any thoughts anyone?

 

[geiman]

Um geiman, you already tipped me to this. Since you brought it up again, is there anything that we can re-dope the surrounds with? Whatever was there originally has seemed to melt (?) and run onto the paper cones of the mids/tweets. As good as the mids & tweeters sound on these speakers, I wonder if re-doping the surrounds to further isolate the front and rear sound waves of the drivers would improve the sound?
Any thoughts anyone?

On the two sets of Optimus speakers I have with this tweeter I see no evidence they were ever "doped". I think doping might have a detrimental effect, reducing flexibility affecting the compliance of the surround.

But who knows, try it and see!

 

[RickeyM]

On all three cones on both speakers there is "something" around the edges of the cones. It looks like something "ran" onto them from the edges. I was thinking this was whatever was on the surrounds to seal 'em?

 

[tiga]

I drove these with my Pilot tube amp last night - sounded even better. Very smooth from top to bottom with great detail in the low end. Next step is to get the cabinets cleaned up, which may have to wait until spring, and get some proper stands for them.

I have to admit there's a part me that thinks I enjoy the sound so much because of the work I put into them.

 

[Buzzbomb]

On all three cones on both speakers there is "something" around the edges of the cones. It looks like something "ran" onto them from the edges. I was thinking this was whatever was on the surrounds to seal 'em?

I was curious about this as well. My 5B's show this same "running" subtance on the tweets and mids. You can see it in most pictures of units for sale/auction. I assume it is factory treatment?

 

[RickeyM]

I have to admit there's a part me that thinks I enjoy the sound so much because of the work I put into them.

Nah, that couldn't be the case .



Sorry, I couldn't even type that and keep a straight face. Of COURSE you enjoy 'em more. The work you put into them makes 'em sound better than when you got 'em right :thmbsp:

These speakers, with a tube front end My Maggies would be so jealous.

 

[Marceilo]

Please find in the attachments, the circuit diagram as well as the measurements from the completed system. I will be happy to answer any questions you may have. I think you will love these changes!!! The graphs show the circuit diagram with the parts value listed for each part, the electrical transfer function of the new crossover, followed by the acoustical transfer function, followed by the impedance with phase and then the Gated SPL of the finished speaker with Phase.

Please NOTE: The tweeter and the mid units must be wired out of phase as shown in the circuit diagram. This is due to their offset in time. This 180 degree shift lines up the time domain with the woofer.

Hi, VL,

Have you ever posted your "original" raw driver-only responses* w/notes as to exactly how they were measured? (Mic distance & position relative to the baffle, etc.) Just kind of guessing backwards, mine (especially for the tweeter) don't quite "line up".

*I looked though this thread and don't see those curves, but I could have missed 'em.

Thanks!

 

[videolady201]

Raw Drivers

Hi, VL,

Have you ever posted your "original" raw driver-only responses* w/notes as to exactly how they were measured? (Mic distance & position relative to the baffle, etc.) Just kind of guessing backwards, mine (especially for the tweeter) don't quite "line up".

*I looked though this thread and don't see those curves, but I could have missed 'em.

Thanks!

No I haven't. I will look back through my files. I should still have them. If I find them I will post the raw sweeps and the testings information. :yes:

 

[videolady201]

Nova 8b Raw Sweeps

Attached is the graph of the raw sweeps of the Nova 8bs. Testing was performed as follows:

The mic was one meter from the speaker and on axis with the tweeter. The speaker was in our 35 foot anechoic chamber. The raw sweeps were then tail corrected for crossover design. The curves also were 1/3 octave smoothed. See attached graph.

 

[Marceilo]

Ok, thanks. I'll try recurving & try to match conditions as closely as possible. (I don't have a 35 ft. anechoic chamber[!]) but I do have LMS, a large space, and a recently calibrated ACO 7012 mic.)

 

[Rockyhill]

I just picked up a pair of Nova 8's today. Found this thread! I'm still a little dizzy after reading it (it's long) so I want to confirm that this mod applies to the 8 (non-B) without any 'mod' to the mod.

I did try the 8" riser suggestion and they sound a tad better that way pre-mod.

If anyone has any photo's of before, during and after that would help as I'm a newbie to speaker tweaking. Not so great at translating a schematic to component hookup. I think a page or two back there was a good picture but anything else to help the cause would be appreciated.

I'll open them up soon to confirm VL's driver prerequisites.

Oh, has anyone deterimined the sensitivity of these? I may want to use with a ST-35 I'll be building later this winter.

Rob

 

[Rockyhill]

I was informed there is this substitute for the Nova 8 4 ohm tweet to 8 ohm from Parts Express:

http://www.parts-express.com/pe/show...number=270-252

Has anyone modded their Nova 8's (non-B)?