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
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?
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.
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..
First, you might want to ask more at DIYaudio.com

Second, check and see if the cabinets have built in crossovers.  They might already.  Look inside and see if you find more than just wires.

Lastly, 40-50 watts is in fact a lot of power.  Stick with that, but you probably want to know the impedance of each cabinet.  You can measure it using DATS (Parts Express) or a DIY jig using Room EQ Wizard.
Also, forgot to mention, a great learning tool is XSim crossover simulator.

You can try out different wiring configurations and use XSim to help you see how impedance will vary.  Great if you can measure the individual drivers and parts, but if you can't you can still use it as a learning tool.

Best,

Erik
Can I keep that picture? Couple times a week someone asks for a desktop speaker with good bass, this will come in real handy.

https://imgur.com/z2lAvpy
Excellent--thank you all very much. Good stuff.

I love that picture. MC, I'm assuming you're serious and I appreciate your considerate question. Yes, my friend is pleased at the thought that the picture may inspire some smiles! 
It looks like they have tweets and mids in the top.

They would be a MTTM if they were on their side? or if one side on top was wired out of phase and pointed UP.  The other 4 drivers toward the seated position.  Might be really surprised how that stuff sounds.

It's fun if nothing else.. The stuff I did as a kid, I'm surprised I didn't burn my mothers house down.. I replaced a couple boxes of the old screw-in fuses.. LOL
The top speakers look like modified Bose 901’s. If so, they are facing the wrong direction. I can’t believe someone gave those away. Well, actually, I can.
Are you sure that picture isn't out-takes from  Clockwork Orange?
Desktop set up aspiration - quite subtle!

Someone put a lot of effort into those. Not to mention $$$’s

I agree with Eric, a trip to diyaudio.com will be a great source of info.

Have you pulled any of the drivers out of the cabinets? Hopefully the drivers have manufacturers labels.
Peaking inside should answer most questions.

you should be able to get a rough estimate as far as sensitivity goes if you run a 1k tone into them. You’ll want to measure the AC voltage at the source (power amp output) , set the volume so you get 2.83v. Then get an app for your phone and measure the db output at 1 meter.
Ps - earplugs are a good idea...
Reminds me of the big cabs I built out of plywood back in the day. 12" McKenzie bass drivers and horn tweeters. Rolled out for parties, they shook the house.
The most 'over the top' computer monitors I've seen of late. *G*  But I'd turn down the Win System Sounds to keep from 'dinging' one out of the chair....;) *L*

I'll vote w/opening them up and looking for labels, noting the wiring, etc.  As one who frequents diyAudio, they'd likely suggest the same as a jumping-off point.

Next, as Erik suggests, "a DIY jig using Room EQ Wizard" would be the next step to understand what's watt with them...*S*

"He got them for free..." *?!*  Helluva deal...*L*  Maybe not SOTA but ought to be good loud OTT fun.  Mount some casters on the bass boxes and offer a wallpaper peeling service. ;)  But tape the windows in the room 1st....*smirk*
There may be no XO to the woofers, but there has to be for the mids and tweeters for protection.

you HAVE to know the specs on the drivers to know where to cross them over. You can guess, but may never provide protection or good sound that way. 

These are simple speakers. All drivers are wired Series-parallel, for 8 ohms. Composite efficiency is additive, probably 96 dB/w/m over 89-90 of each individual driver.

Guessing, I’d crossover at 750 and 3000 Hz. 

You’ll have to open up the top and bottom cabinets to check: wiring, crossover components, part numbers on the drivers.
If your friend will be listening while seated at the desk, the problem with this setup is that he will not get the sound from all of the drivers to be well integrated at his position.  It might help to toe-in the drivers so that he is at least closer to being on-axis for all of the drivers.  

Given the small space, close proximity to the speakers, and supposedly high efficiency, he could actually go with amps that have considerably less output than 40-50 watts.  I personally would be looking for used low-powered tube gear, particularly something using 6L6, KT66, EL34, or EL84 output tubes.  Even single-ended triode amps are a possibility (300b, or 45, or 2a3 tube), although decent used ones do not seem to be that inexpensive.  If your friend is at all handy, perhaps a kit amp from the Japanese company Elekit would be nice, although not in the Craigslist kind of price range (but there is nothing wrong with a really good amp used with modest speakers).
I would take the owners word on what amp power you might need. But no way of really knowing unless you measure it. 
"...Anyone can tell just looking at them they will play plenty loud with 10 watts..."

I don't think you can say that. Sure, a large speaker with many drivers could be a way to achieve efficiency but no telling what is behind the grill cloth, what the speaker array is, or what crossover is used.  

Of course not. Blanket statements like that never fly. Anyone refers to anyone who knows a little about speakers, how they work, the different designs, etc. Anyone like that looks at these, and it is instantly readily apparent. First, old paper cone drivers. These were all made back when modern ideas were still way out in the future. They are all pretty efficient. Then sheer cabinet size. Modern speakers are made for women. Women don’t want to see a speaker at all, designers know men are too whipped to buy anything that might turn a woman off, WAF etc etc, so now we have all these teeny tiny little horribly inefficient things. Big box equals big sound, period.

Finally, see that big gaping hole in the top? Anyone knows anything about speakers that big hole says something like folded horn, transmission line, whatever we don’t know exactly but any way you slice it winds up being high efficiency. Same with the big ported uppers.  

So you see it really is the case that anyone can see. Anyone who has a clue. Which would have remained pleasantly unsaid until you had to go and try and one-up me on it. Oh well. Live and learn?
I too wondered about that big hole in the bass cabinet.  I could not tell if that is meant to be the opening of a back-loaded woofer set up (i.e., transmission line/quarter wave back-loaded horn), or the mouth of a compression midrange driver, or a handy shelf to stash weed and smoking paraphernalia.

Also, the top array looks so much like the back of an old Bose 901, with half the drivers removed (a dead giveaway on that would be a driver on the back of that array).  If it is a 901, but with different drivers, it may be quite efficient, if it is 901 drivers, it would not be that efficient.

In any case, even if it is not that efficient, in that room, I would expect 40 watts would be more than enough.  For any given price point, it is easier to make something that sounds good when you don't demand high power.  
"... So you see it really is the case that anyone can see. Anyone who has a clue..."

I'm not trying to one up you. The bass array sure gives the impression of an efficient system but the upper arrays really could be anything. Looks like he left the other drivers out of the array to get some back wave energy out. I'd say yours was a pretty good guess but, I think it is still a guess. 
Ummm...  Have you actually listened to them?  Big does not equate to good.  Or even listenable.  Clearly they were built to play loud.  Ear splitting loud.  If that's the only criteria, go buy some good rock band PA speakers.  Those things are professionally engineered to play at high levels and will weigh less than half these things.
Wait are those the new Wilson PUP'S $ 187,00000,00 price reduction because of COVID 19 infected woofer's !!!!