4x12 subwoofer with passive radiators

[mcdap74]

Like so many others, I often daydream about speaker ideas. Here is one of my ideas. I play the guitar. I have two old 4x12 cabinets that I picked up pretty cheap. But I never use these for the guitar. I like them because they look cool and they are great for sitting my PA mains on. But I have often fantasized about making them useful and turning them into subwoofers. So my thought is to get a single high output subwoofer and three passive radiators in each cabinet. I would like for these to be usable as HT and PA subs. And like many out there, I would like to do this as cheaply as possible. So I am thinking of Dayton's least costly PR along with a pretty decent subwoofer. Does this idea seem stupid? I just think that this would pretty killer and would put my useless cabs to good use. BTW, a standard 4x12 is about 30"x30"x18". The internal dims are probably around 29"x29"x15". Let me if this seems like a good idea. Perhaps I will pull the trigger and give this a go! Any driver recommendations are appreciated too!

[Wolf]

Re: 4x12 subwoofer with passive radiators

If you use 3 PR's and an active, using the Dayton Cheap PR's, you won't be able to load them with enough mass to tune low enough. If you use the NS PR's, you might be able to get away with 2 drivers and 2 PR's if you pick well. That's more output than using a single active.

Later,
Wolf

[mcdap74]

Re: 4x12 subwoofer with passive radiators

You sure do know how to burst a person's bubble. :P

I don't much about pr's except what I have read online. I have read that adding mass makes the bass sound slow and sloppy. I have also read that using multiple pr's produces good results.

I keep thinking of using the Eminence Lab12. I could use a single pr and then plug the other two holes with plywood (with pics of speakers glued on to maintain the 4x12 look). The positive of only using one pr is that it should save some money.

Do you know of any good resources for learning more about pr's?

Have you ever used an actual loudspeaker as a pr? I had a 2x12 guitar cab loaded with a 12" and an 8" on a baffle that I made. I disconnected the
8" and it in place. I could hear a noticable amount of bass being
added due to the 8" speaker. When I took it out and tried a "detuned" scenario, the bass reponse was less than with the 8" installed.

So many questions. So few answers. Perhaps I have to go down the
experimental path.

[MGrant1957]

Re: 4x12 subwoofer with passive radiators

Do you have a budget? What are the Power Specs on the amp? Is this for a PA that requires high sensitivity? Home Theater? We need more input.

Off the top of my head I'd say a good low cost recommendation would use a pair of Dayton DVC310-PR 12" Passives with a pair of Dayton DCS305-4s, as that size box could support them.

Ice

[Chris Roemer]

Re: 4x12 subwoofer with passive radiators

You sure do know how to burst a person's bubble. :P

I don't much about pr's except what I have read online. I have read that adding mass makes the bass sound slow and sloppy. I have also read that using multiple pr's produces good results.

You MUST add the PROPER mass to achieve the correct TUNING, period. .
A PR (or two) need to have more "displacement" potential than your driven driver (2x is the ROT). The LAB12 has a hugemongous Xmax. You need to find a single PR with the same dia. and double the Xmax, OR use a pair of PRs of the same (12") dia. and the same Xmax (the LAB12 is around 12mm, isn't it?), or a 15" PR with the same throw as the LAB12.

I keep thinking of using the Eminence Lab12. I could use a single pr and then plug the other two holes with plywood (with pics of speakers glued on to maintain the 4x12 look). The positive of only using one pr is that it should save some money.

Won't ever happen.

Do you know of any good resources for learning more about pr's?

Have you ever used an actual loudspeaker as a pr? I had a 2x12 guitar cab loaded with a 12" and an 8" on a baffle that I made. I disconnected the
8" and it in place. I could hear a noticable amount of bass being
added due to the 8" speaker. When I took it out and tried a "detuned" scenario, the bass reponse was less than with the 8" installed.

So many questions. So few answers. Perhaps I have to go down the
experimental path.

Chris

[MSaturn]

Re: 4x12 subwoofer with passive radiators

Ah, the bass speed myth continues its march ..

Like he said, the right tuning is the right tuning, it's the end result that matters. PRs are just fancy, less leaky ports.

From the sound of it, you'll have to do some experimenting - a single 12" woofer and two PRs is doable, but you'll have to match them up. Get yourself Jeff B.'s software and start crunching numbers.

I like the idea, though.

[mcdap74]

Re: 4x12 subwoofer with passive radiators

Thanks to everyone for engaging me on this and offering up ideas.

I'm typing this on my iPhone. So some of my sentences below make sound like a barefoot hillbilly. I may be from Oklahoma. But I ain't no hillbilly! If Steve Jobs in his infinite wisdom pit some navigation arrow buttons on this thing then I wouldn't have this problem.

I don't really have a budget. But I am tight with my money. So I don't want to experiment too awfully much. I rather do it "right" the first time.

I want this to be dual purpose. My "theater room" is also my band reharsal space. So I want to use this sub for both HT and PA. But I don't need it to be gawd awful loud!

Cocerning port tuning, I believe that it is clear that there is not just a single port tuning method, though most methods are based on the TS way of looking at things. Electrovoice used to make some PA boxes that were tuned 1/3rd octave below what TS called for, the idea being to extend the LF response of these PA speakers just a little bit lower. Of course this method probably involved some trade-offs, as do most things in life. Perhaps tuning a PR 1/3rd octave below what TS calls for will help smooth out the dip in the frequency response due to the driver and PR being out of phase with one another.

Concerning the "speed" of bass, I probably should have used the
term transient response. The fact is that heavier stuff
responds to input stimuli at slower rate. It also longer for
heavier stuff to come to rest. I am always a bit concerned with transient response. I hate sloppy bass!

Thanks again to everyone. Now I just gotta convince myself to spend a little money, that is after I play around with that software that was suggested.

[diy speaker guy]

Re: 4x12 subwoofer with passive radiators

Cocerning port tuning, I believe that it is clear that there is not just a single port tuning method, though most methods are based on the TS way of looking at things. Electrovoice used to make some PA boxes that were tuned 1/3rd octave below what TS called for, the idea being to extend the LF response of these PA speakers just a little bit lower. Of course this method probably involved some trade-offs, as do most things in life. Perhaps tuning a PR 1/3rd octave below what TS calls for will help smooth out the dip in the frequency response due to the driver and PR being out of phase with one another.

T/S are a list of driver parameters, and as such, they don't "call for" anything. You can tune to any frequency you want and there are at least a dozen factors you should be taking into account when choosing the tuning frequency.

There are 3 basic ways to tune a box.
1. Trial and error by ear. Somewhat popular in Japan but not on this continent since t/s parameters were defined.
2. Using old pre-t/s formulas. Not a whole lot more helpful than trial and error.
3. Using t/s parameters. Even with this method there is no perfectly unanimous "right" tuning, it all depends on pre-defined usage goals and response. There are many common targeted alignments (such as max flat and many others) but in between these is a whole continuum of other possible valid choices.

[mightym]

Re: 4x12 subwoofer with passive radiators

I think it's a neat idea, but that's the kind of Hairpin I am. Interesting repurposing proposal ( say that fast 5 times ).

No one has offered any useful PR info, it's something I've been looking into myself. There just isn't a whole lot of info that I've been able to find. What I have stumbled across is a pretty good section on the AE site:www.aespeakers.com/PRFAQ.php

An interesting but never updated DIY effort that I think could be further investigated here :https://www.danmarx.org/audioinnovat...tpassives.html

I do know that Steve Decker(t) of Decware uses a sort of DIY PR on one of his designs with a fullranger ( Modified Fostex FE 206 E ). But I haven't further investigated that avenue.

I believe that a carefully selected driver could be utilized to do what you wish. I too have wondered why one couldn't purchase a supply of the inexpensive buyout drivers that PE offers, remove the magnet, and voice coil and use them for PR too...

BTW Where in Ok are you?

John

Seems to me that the magnet and coils of the buyout drivers might be more useful if left in place, and a potentiometer placed across the terminals, then adjust the tuning with it, till your happy and replace it with a suitable cermet resistor. Just spitballin' here....

[mcdap74]

Re: 4x12 subwoofer with passive radiators

Thanks DIY Speaker Guy for stating things much more elegantly.

If I use three PR's, I have questioned whether there would be any value to tuning each PR a little differently from each other. Perhaps tuning each of them a little differently would help to minimize the frequency cancellation dip.

I'm in Tulsa. West Tulsa to be a little more specific. I see you are from Checotah. I used to live in Muskogee. I went to the races in Wainright every night. I miss going to that track. It is such an awesome facility!

[Wolf]

Re: 4x12 subwoofer with passive radiators

If I use three PR's, I have questioned whether there would be any value to tuning each PR a little differently from each other. Perhaps tuning each of them a little differently would help to minimize the frequency cancellation dip.

In a vented or PR system the number and multiple tunings will always converge to one tuning overall, it makes no difference except your heavier-loaded PR's may react worse or better in comparison to the lighter ones.
Later,
Wolf

[mcdap74]

Re: 4x12 subwoofer with passive radiators

I was playing around with WinISD a little bit tonight. The Lab12 with three of the Dayton SD315-PR's looks pretty good with no added mass. Adding about 72 grams of mass gets me centered on Fs. But how accurate is this software model? This is getting me very tempted to give this a try. Now I just gotta convince the wife that this is worthwhile. $220 is a small price to pay for a husbands hapiness. Right?

[diy speaker guy]

Re: 4x12 subwoofer with passive radiators

I was playing around with WinISD a little bit tonight. The Lab12 with three of the Dayton SD315-PR's looks pretty good with no added mass. Adding about 72 grams of mass gets me centered on Fs. But how accurate is this software model?

I've never been interested in passive radiators and never modelled one, but assuming you are doing it correctly the model should be fairly accurate. I don't like WinISD that much but in this case, the internal dimensions are pretty short and the port isn't too long (actually non existent) so the model should hold up fairly well. Of course the simulation doesn't take the driver's actual response into account, or the baffle step or room interaction (things like floor boundary, room gain, room modes, etc) but if you know what to expect you don't need to see those things.

Or you can use Jeff Bagby's software suite for a much more accurate simulation, as it can account for all these things (except room modes).