Right speaker design for Realistic Nova 7b cabinets

[hittheskids]

Hey everyone, new guy here. Excited to be a part of this community and get started on my first build. I have a pair of Nova 7b cabinets that I refinished last year and really like how they turned out. I would like to use them for my build as I plan on just parting out the existing drivers and grills to someone in the vintage community in need of them. The internal dimensions of the cabinets are approximately 11"W x 10"D x 21"H, I also plan on powering the new speakers with an Akai AA-1030 receiver (30 WPC @ 8ohms I think). My budget for this project is going to be about $250.00 for the pair. In looking through some of the designs out there I had a few catch my eye but the lack of depth in my cabinets seemed like it could be and issue with a lot of the designs and I'm in need of some help in determining what will work best for the dimensions of these cabinets. I was leaning towards one of Paul Carmody's designs like the Amiga, classix II, or even the classix 2.5 if it would work. I also liked Zaph audio's BAMTM and thought the sealed version of that design might work. Any recommendations and help would be greatly appreciated! Thanks - Keith.

[wogg]

Those are sweet! I have several on paper designs for my Nova 15 's that are almost the same dimensions. Are you planning on keeping the baffles and grills? I'm intending to cut out the baffle and use the inset to mount the new baffle without a grill. Here are the best combos I've modeled so far. I'll share the crossovers i've come up with if you want, but these are paper only and I'm sure someone can share something they've made and measured in real life.

higher end:
RS180-8 with a RS28A-4
3 way based on Zaph ZDT3.5 by adding an RS52AN-4 to the above

Cheaper:
DA215-8 with a ND28F-6

I've done more combos than that, but those are my 3 favorite options so far. I'd have executed one of those already if I had a place to put them, I've got 2 pairs of those Nova 15 to re-build.

[hittheskids]

I planned on doing just as you mentioned, cutting out the existing baffle and installing the new one where the grill currently sits. I'd definitely be interested in your designs, thanks for the feedback. I had seen some designs with the rs-180 and rs28-a that I liked but most of them had a third driver and that seemed to exceed my budget so a 2 way design that worked for those dimensions is something I'd really consider. This is new enough to me that I still don't understand crossover language/designs beyond being able to identify the individual parts. My soldering is gradually getting better though.

[wogg]

Both of these are modeled on the Realistic Nova 15 baffle, which is a 10 3/4" X 19" baffle, slightly smaller than your but not by enough to really throw it off. The woofer is centered and 10" from the top, the tweeter is 7/8" from center and 3" from the top.

This one I call SuperNova 2, the 2 way design with the RS180-8 and RS28A-4. The box is tuned to 42Hz with a 2" x 8" port, which will require a 90 degree bend to fit accomplished with PVC and an elbow. I don't have the schematics simplified, so you'll have to interpret the WinPCD screens.

[wogg]

And this one I call simply Nova 2, since it's less "super" with cheaper parts, the DA215-8 and ND28F-6. The part centers and box tuning ended up nearly identical, but the low extension isn't as good with the DA215-8.

[Brian Steele]

It would be a shame IMO to rebuild these without the grille....

[Whitneyville1]

Yah, they look like the Fisher's of the same era.

[johnnyrichards]

Yah, they look like the Fisher's of the same era.

No.

[hittheskids]

Those particular grills are actually plastic. These ones are pretty well mint with the original badging intact but the plastic is almost frustrating because the build of the cabinets and the veneer on them is really pretty nice. If they had the super-detailed wooden grills like some of the sansuis and pioneers from the same time frame I would definitely use them. I had a pair of sansui sp200's that are probably the nicest cabinets I've personally come across but the speakers were horrid. If I'd have known I was going to give some builds a shot I would have kept them.

Wogg - I"ll likely move forward with one of your designs as I like the idea of a system specifically designed for those cabinets and didn't necessarily have any preferences coming into this project. I had some additional questions that I'll try and post later. Thanks.

[wogg]

That would be awesome, I'd love to hear how those turn out!

The SuperNova2 BOM ends up a little over your budget at $301.02 while the Nova2 ends up much cheaper at $154.18. I didn't include the little cap across the woofer coil on either of those, I typically have some small poly caps like that on hand, so that would add a couple bucks.

[hittheskids]

I'd love to go with those reference series speakers but this being my first build with hopes of doing more in the future it will go a long way in the green light department to keep this project under budget so I better go with your Nova2 design for this one. I ended up with a lot of questions for you so I'll just post them and you get to them whenever you get around to it. I plan on trying to educate myself a little bit about crossover designs before getting this going so if you or anyone know of any good online resources for that feel free to post them.

What were you planning on for bracing/foam/fill?
Where were you planning on locating the port?
Is the port length including the elbow or before adding the elbow and does the location of the elbow matter?
Do you feel like you could help me with the crossover layout when I get to that (at this point I'm literally lost unless I'm looking at a picture/diagram showing me what goes where and what connects to what)?
Will that receiver be ok for these speakers?
Can you post the BOM you have for those for me?

Thanks again, Wogg. I'm excited to get this going and should be able to get everything ordered pretty quick here. Also, If you think of any other parts/products I should get but aren't necessarily part of the speaker build let me know.

[wogg]

Sweet Mr Hittheskids.... I'll help you out as much as I can. What I'll do is zip up the design files for this when I get a chance and post a link. I have a tutorial online about using the design tools I've used for these here: http://woggmusic.com/advanced-speake...gn-simulation/

The only thing I'm missing in that (I learned later) is the importance of keeping the Polars active to tweak your crossover. I'll edit that eventually. Meanwhile... questions:

Bracing / damping: I'd add a dowel between the left and right side, however since I intend the baffle to be removable the brace to the front and back is tricky. I'm intending to add damping along the back wall and call it a day.

The port location isn't important, wherever it will fit toward the bottom and a side of the baffle is good. The 90 degree bend will need to be done with a PVC fitting, a slow bend, not a tight 90. The total length will include the centerline of the port all the way from the exit, through the bend, and to the internal end.

Myself and lots of folks here can help with layout when that time comes.

Any receiver will work for these, they're an easy 8 ohm load.

The BOM will be in the ZIP file.

Also, I'll add that I vastly prefer the RS design myself too, but totally understand keeping it in budget for future approvals. After all, you'll need some subwoofer action After I post the design files, perhaps we can get some assistance from some crossover design pros here to flatten it out a bit more. The response is smooth, and the phase is good but it's a little bit rounded up in the middle which may make it a bit shouty or forward in the mids.

[hittheskids]

Awesome. What kind of differences could an untrained ear like mine expect to hear between the two designs with the receiver I'll be running? If you feel like the RS design is on another level altogether and the crossovers are nearly the same perhaps I'll wait to order the drivers and see what I can come up with.

[wogg]

Awesome. What kind of differences could an untrained ear like mine expect to hear between the two designs with the receiver I'll be running? If you feel like the RS design is on another level altogether and the crossovers are nearly the same perhaps I'll wait to order the drivers and see what I can come up with.

I'm not exactly sure how audible the reduced distortion of the RS line will be audible, I'd wager you'd have to A/B switch them to tell. Those RS drivers are really well received, but the DA is used in Carmody's Hitmakers in it's 6.5" version and is also well received, so FWIW... What does stick out for me immediately is that the RS180 models better in that box for bass. The RS180 crosses that 80dB mark in the mid 40's while the DA215 crosses that line in the mid 70's.

The RS version will be a whole lot more pleasing in the low end without a sub than the DA, but if you add a subwoofer, that distinction disappears. Are you planning on using these with a sub, if now now than sometime?

[hittheskids]

I did not plan on adding a sub but I'm certainly not against it at some point. However, I'd also have to get my hands on another receiver too as mine are of the vintage 2 channel variety (also have a Realistic STA-2200 that is currently powering a pair of XL7F's). It seems like I had heard of people running a sub through those types of receivers but you didn't end up having the control ability you needed for them or something to that effect.