Taming the Cerwin Vega 316R Hardrockers. A Fool's errand.

[Dan Carlson]

Hi all. I am about to dip my toes into speaker building. Over the weekend I scored a pair of rough Cerwin Vega 316R cabinets. Missing the woofers and one of the rear-firing tweeters. Condition of the midranges is yet unknown. I know that these are rare bears but I really don't want the signature Cerwin Vega hard rock party speaker sound, and while the cabinets are intact, they are probably not nice enough to ever be of collector value if restored. So, I am treating them as a set of boxes with a decent amount of volume for a 15 inch woofer​

 

[Dan Carlson]

My end goal is to have a nice set of large speakers with sensitive drivers to go with tube gear in the future, for listening to a wide variety of genres, at moderate volumes. As I am a complete newb at this. I am soliciting an approach to selection of a set of economical drivers (perhaps Alnico?) and a crossover design to suit

 

[Dan Carlson]

I am aware that many will feel that this is folly, that driver design dictates cabinet volume and construction, as well as crossover design and I agree to a point. My benchmark here is ending up with something reasonably above mid-fi; a somewhat intentionally imperfect design. A warts and all throwback to the early days of Hi-Fi, when established design principles and formulae were still being developed, if you will. Certainly, if anyone has ideas about this then I am open to suggestions

 

[Nyjblbob]

Alnico JBL's as well as Altecs Even EV's are good.and would be an upgrade, They are widely available. Find out how big the cabinets are Cu Ft. for the correct port size.
Plenty of Drivers and xovers out there used. Cabinets should also be strengthened as well.
should be a fun project

 

[rothwellaudio]

I am aware that many will feel that this is folly, that driver design dictates cabinet volume and construction...

For vented speakers, that's true. Sealed boxes are more forgiving. You'll need suitable drivers for sealed boxes, but they are available. An EBP (efficiency bandwidth product) of less than 100 makes the drivers suitable for sealed boxes.
http://www.mh-audio.nl/Calculators/BRH.html
http://www.mh-audio.nl/Calculators/CCC.html

 

[Dan Carlson]

For vented speakers, that's true. Sealed boxes are more forgiving. You'll need suitable drivers for sealed boxes, but they are available. An EBP (efficiency bandwidth product) of less than 100 makes the drivers suitable for sealed boxes.
http://www.mh-audio.nl/Calculators/BRH.html
http://www.mh-audio.nl/Calculators/CCC.html

Will post pictures when I get a chance later today or tomorrow, but these critters seem to be ported. On one box the rear firing (Foster?) bullet horn tweeter has been relocated to the front, and there is a plastic port on the upper middle of the back baffle. The sales brochure scan that I found online seems to indicate that only the midrange is sealed. I haven't stuck my arm up there to find out yet but I would expect to find a sealing cup behind the driver

 

[rothwellaudio]

Will post pictures when I get a chance later today or tomorrow, but these critters seem to be ported.

Ports can be blocked off quite easily. I mentioned closed boxes on the assumption that you'll be using different woofers and want something easy to design, or at least easier than ported speakers.
If you go for ported speakers the tuning frequency can be altered by extending or shortening the port length.

 

[John James]

I don't know a thing about designing speakers but you may find some useful info in the Econowave threads.

Good luck!

 

[Dan Carlson]

Yes, making plugs presents no real challenge for me. I am a toolroom CNC machinist by trade and can whip something out quite easily at work. Would ABS plastic be a suitable material to make the plugs? We have some gray ABS material at work, same thickness as the cabinet walls, 3/4 inch

 

[bowtie427ss]

, when established design principles and formulae were still being developed

This goes back further than most folks are aware, think Bell Labs in the late 1920's.

The 316R cabinet actually appears to be a (rear) slot type port, and may require somewhat different considerations than a simple ducted port, if you choose to go the ported route.

A decent PA woofer like JBL 2225/2226(and a dozen others) would probably be right at home with little or no modification to the cabinet itself. Something like the Dayton Pro PA-380 woofers are a great bang for the buck.

About the next most economical option for woofers are the(close to original) cast frame Cerwin Vegas being offered on ebay @ 130 + 25 shipping/ea.. That money will buy JBL's.

Just my .02....

 

[rothwellaudio]

Yes, making plugs presents no real challenge for me. I am a toolroom CNC machinist by trade and can whip something out quite easily at work. Would ABS plastic be a suitable material to make the plugs? We have some gray ABS material at work, same thickness as the cabinet walls, 3/4 inch

Anything would work. Even stuffing up the hole with a bit of old cloth would work.
Ported speakers are much easier to get wrong than sealed speakers. Having said that, if you want ported speakers, go for it. Just be aware that there's more design work involved and more chance of things going wrong.

 

[bowtie427ss]

We should really have a look at the internal structure of the 316R box.

I'm not certain, but i think there were other members of that family of CV's that were a sort of hybrid between sealed and transmission line.

A look at the port:

 

[Dan Carlson]

I was looking at those Dayton Pro PA-380's yesterday morning and wondering if they might be appropriate

 

[NeilBEN]

Have you heard these speakers, and do you like how they sound? I don't think it is possible to get them back to "spec" with any precision. I think you may be able to get them working, and if you are going to do all the work, then you might as well try to get them to sound better than they did.

It seems unlikely that the surviving drivers can work "to spec" - and to find replacement drivers that can work in the cabinets, means that the crossover will need to be completely reworked no matter what.

Start by looking for drivers that will actually fit in the openings, and then within those, which ones are workable in sealed enclosures. What are the volumes of the midrange enclosure, the woofer? What are their relative sensitivities and frequency responses, and impedences? Do you use horn tweeters, or dome?

And what crossover will you use - maybe an active system that lets you quickly try out different crossover points and slopes? (But require triamping ...) I did an active crossover for my 2-way Linaeum LT1000, and it was not simple, but it was possible. The flexibility of this is hard to beat.

Or some new version of an analog 3-way design? You might be able to run the midrange without a filter, and then tailor the woofer and tweeters to blend in?

 

[NeilBEN]

We should really have a look at the internal structure of the 316R box.

I'm not certain, but i think there were other members of that family of CV's that were a sort of hybrid between sealed and transmission line.

A look at the port:

From this picture, it seems like the midrange is sealed, and the bass has a slot port:

 

[Dan Carlson]

We should really have a look at the internal structure of the 316R box.

I'm not certain, but i think there were other members of that family of CV's that were a sort of hybrid between sealed and transmission line

It does appear that these are some hybrid. Here is a shot I took today of the bracing and the midrange enclosure.

 

[Dan Carlson]

And here is another of the cabinet floor (the cab is on its side laying in my trunk). There is a slot in the false floor at the front directly below the woofer, and the lower 2 inches of the cabinet below the false floor are open to the back. These things are disgustingly filthy. Stored poorly with the woofers gone missing. Evidence of mice. Yuck.

 

[Dan Carlson]

And here is the port exit on the lower back. The plastic part I thought was a port on the upper middle of the back is a block off plug for unused tweeter holes

 

[Dan Carlson]

Now this all begs the question, do I block off that port at the slot in the false floor or at the bottom back of the cabinet. Or, should I just fill the port chamber with urethane foam?

 

[Nyjblbob]

My advise is try to find woofers that can ,use the port, and upgrade the mids and highs, and then the x-overs.