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Help with some big ol' used DIY speakers

A good friend of mine, passionate about music but new to this hobby, is putting together a system on a dime, a nickel if he can help it. It's a fun project. He recently picked up a pair of whopper DIY, homemade speakers for free (craigslist). He rolled them into his office and this awesome picture tells the story:

https://imgur.com/z2lAvpy

Two questions. First: is there any way to look at those speakers and gauge the kind of amplification they'll need? The guy who built the speakers implied they were rated at 8 ohms and were quite efficient. He said he was using an old 90 watt receiver, and said that even 40-50 watts would be fine. (We're not talking class A here.) I don't think he knows the other specs, such as sensitivity, etc. Maybe it's because I have mini monitors that are underpowered at 200 Bryston watts, but I can't imagine driving those big boys for a house or lawn party with an old 50 watt receiver. I'm hoping my friend can try out a few different amps but that may not be possible. The question is: is there any way to look at those and guesstimate what he needs to drive them? Or, without knowing their sensitivity, is it really just trial and error? Keep in mind the ethos here: free or close to it. So while you can never have too much power, it's also much easier to find inexpensive used receivers or integrated amps at 50-100 watts. (Of course, the watts rating of a receiver or amp doesn't really tell us all that much, but it's likely the best guide as my friend looks around at used equipment.)

The second question is about the wiring. The speakers are in two cabinets, with the woofers below and the tweeters/midrange above. The man who made them simply runs speaker wire from the amp (receiver) to the base cabinet and then more wire from the terminals on the base cabinet to the terminals on the top cabinet. That makes sense, I guess, but without crossovers I assume that the full-range signal would be going to all the drivers. This might not be ideal for the quiet moments of a Chopin etude, but as long as the timing sounds okay, are there any issues with this? I've never done this kind of thing before. I can't imagine my friend would want to plunk down money for an outboard crossover, if that would even work, but maybe. Thoughts?

As you can tell, the goal here is to have some fun putting together a system for as little money as possible ... and to have all kinds of fun cranking tunes and throwing parties!
northman
millercarbon's avatar
millercarbon
12,531 posts
 
Anyone can tell just looking at them they will play plenty loud with 10 watts. Crazy loud. This is great, as it means anything he buys any power at all will be fine. If he wants quality I would look for a tube amp someone is throwing away, for the cost of a new set of tubes he'd be set. Or SS will be a lot more cheap to choose from, maybe some even worth listening to. Well we can hope.

There's no problem with the wiring. The owner built them, he would know. I can see these during the quieter moments of AC/DC not Chopin, but no worries, with all those drivers pointing all directions they truly will present massed strings as a mass of strings.

Honestly, I think you will be pleasantly surprised. We did something like this in college with some ancient speaker in a huge box with smashed up domes and were all impressed how good it sounds. This will play big and full and loud for cheap. What could be more fun than that?
northman OP
268 posts
 
Perfect! Just what we wanted to hear! It can feel counterintuitive to me that huge speakers don't necessarily need much power, but I also know it can be true. Thanks, MC.
oldhvymec
5,101 posts
 
Some of the greatest speakers that ever were, are still in some folks imagination. Necessity is truly the mother of invention. I think it's a silhouette of a Klipsch kind of idea (La Scala / Corner hybrid)
The problem is no horns. :-).

Second a NEW 70.00 usd Behringer active XO CX3400 would put all the crossover points in the right places. for a 2 or 3 way. You could add a topper (tweeter) for the 3 way.. You might be surprised. The problem is for every channel you add you have to add an amp. That would be 6 channels for a 3 way and 4 for a 2 way..

But the biggest thing I see is getting a center phantom speaker.. Imaging! They are going to make a LOT of sound, PARTY speakers, garage speakers, shop speakers, basement speakers, BUT YOUR speakers.. Maybe not..

A Parts Express passive XO is 39-79.00 for a pair. Then you could use a single stereo amp..

I think you'll find both cabinets are either 4ohm or 8 and wired together they will ohm out at 4 or 8 ohms.. Are there any passive XOs? Bose didn't use them in the early 901s, I know that..

That 45 degree topper though.. Maybe unplug the outside drivers on the top. Then point the bass section forward no toe in..
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