Crazy idea for Polk rta 12... worth pursuing?

[mountainhick]

Noob to the forum here. I have built speaker systems in the past, but I have forgotten pretty much everything I used to know about design. I do however have the hands on skills for building. I am a woodworker and cranking out a set of boxes for any given project is a very easy task for me, and soldering/assembly skills for crossovers is no problema.

I searched for this but found nothing so here goes...

I have a pair of Polk RTA 12 which I love but they are too big for my current space. I am wondering whether it is worth reconfiguring the driver array to an MTM or TMM config in smaller enclosures and losing the passive radiators. It would fit the space much better to have these smaller boxes and a sub. (I already have the sub)

Thoughts?

If this is not a ridiculous idea, does anyone have the TS info for the drivers in these polks, and/or other info for the cabinet volume and crossover considerations?

[Jim Shearer]

My brother has a pair of RTA-12c which I think sound VERY good. I don't think that butchering the cabs will result in anything even close to what they are now. And I hate to see a really nice pair of speakers trashed.

BTW--the mid-woofs have their magnets glued on; the glue tends to fail with age, especially if the drivers take a hard jolt. You might consider pulling those drivers out and reinforcing the bond with some extra glue (epoxy?) to make sure the magnets stay in place. Particularly important if you start moving them around.

Cheers, Jim

[mountainhick]

I hear ya, but they really do not work for the space so if I don't mod them, I'll just have to sell them and either buy or build a new set. Believe it or not, the building project is easier and less hassle for me. I live in a remote location and selling things is more of a chore than the woodworking.

Also, I would not butcher the cabinets. I would remove the drivers, put them in new cabinets and store the original cabinets.

[mountainhick]

One more try for info before I get out the chainsaw!

(Just kidding)



I guess a more specific question is, if I put these drivers in a smaller box will I be messing with crossover's effect?

One thing about these speakers is the tweeter is set back from the face of the cabinet. I assume that if I were to remount them in a different cabinet that I would need to keep this setback, and that it would be best to keep a TMM alignment instead of an MTM. Thoughts?

[bzfcocon]

Originally Posted by mountainhick

One thing about these speakers is the tweeter is set back from the face of the cabinet. I assume that if I were to remount them in a different cabinet that I would need to keep this setback, and that it would be best to keep a TMM alignment instead of an MTM. Thoughts?

If you want them to sound as close as possible to the original - and assuming you would keep the existing crossover - you should at the very least preserve the distances between speakers and their configuration (TMM) and, of course, the tweeter setback. Also, the baffle size should be similar or you will need to readjust baffle step compensation. Otherwise, you would basically need to redesign the speaker/crossover.

Frankly, I do not think you will get the same sound as from the original cabinets.

[mountainhick]

Thanks. I definitely don't expect the same bass response. As stated above, they are too big for the room, and I will also be running a sub, so having them roll off is just fine. What I don't know is whether just repackaging the parts in a smaller box will result in good (similar or same) mid-upper frequency response.

[Richard Ellis]

I,m sure you can reconfigure a "new" cabinet for your Polks...
The akward dimensions really would take up lots of space.
So...make some detailed measurements of the existing cab dimensions to get a handle on internal dimensions. If you can, after the drivers are removed, try to measure inside the cab as one might not know the cab thicknesses.
After getting all your measurements we now know the internal volume!
I guess the gist of the discussion is...you MUST maintain the exact same internal volume....in whatever dimension you choose.
Now...I would guess the speakers are taking up too much floorspace...they are akward.. very dated looking..so.. I would opt for a skinny (12") wide(Front), by Nineteen inches deep, by say Fifty inches high. Play with those figures to hit your target volume. Thus you will have a loudspeaker that takes up very little floorspace....One and a half SQ Ft! Appx!
Run the passive radiator on the side wall, the two 8"? in an MTM configuration with the tweeter between the two remember frequency derived spacing...
You will be bring your key drivers up toward ear level....A nice four inch radius on the front edges will get you some outstanding imaging.
I say go for it!

__________________________________________________ _______Rick......

[mountainhick]

Originally Posted by Richard Ellis

I,m sure you can reconfigure a "new" cabinet for your Polks...
The akward dimensions really would take up lots of space.
So...make some detailed measurements of the existing cab dimensions to get a handle on internal dimensions. If you can, after the drivers are removed, try to measure inside the cab as one might not know the cab thicknesses.
After getting all your measurements we now know the internal volume!
I guess the gist of the discussion is...you MUST maintain the exact same internal volume....in whatever dimension you choose.
Now...I would guess the speakers are taking up too much floorspace...they are akward.. very dated looking..so.. I would opt for a skinny (12") wide(Front), by Nineteen inches deep, by say Fifty inches high. Play with those figures to hit your target volume. Thus you will have a loudspeaker that takes up very little floorspace....One and a half SQ Ft! Appx!
Run the passive radiator on the side wall, the two 8"? in an MTM configuration with the tweeter between the two remember frequency derived spacing...
You will be bring your key drivers up toward ear level....A nice four inch radius on the front edges will get you some outstanding imaging.
I say go for it!

__________________________________________________ _______Rick......

Thanks, however, it is not a floorspace issue, it is the overall volume. I am not seeking the same internal volume. I intend to go much smaller and get rid of the passive radiator.

Wouldn't an MTM config require a different crossover?

[planet10]

I've not heard the fancier RTA12, but since the day we unboxed the 1st polk's with the doubled breasted mid-bass i wondered how reconfiguring these would work. I always found the bass a bit fat & woolly, and i don't think loosing the PR to gain some finese over ultimate extension would be a hardship. Given my latest experiments i'd do an MT, with the 2nd midbass on the side or the top.

Knowing the T/S of the midbasses would go a long way to knowing what kind of box would best suit.

From the looks of the XO, i suspect it is all up at the XO point with little or none BSC in the XO. I'd mount the XO externally anyway.

dave

[mountainhick]

Originally Posted by planet10

i don't think loosing the PR to gain some finese over ultimate extension would be a hardship.

Now that's what I'm talking about!!!

Originally Posted by planet10

Given my latest experiments i'd do an MT, with the 2nd midbass on the side or the top.

Knowing the T/S of the midbasses would go a long way to knowing what kind of box would best suit.

From the looks of the XO, i suspect it is all up at the XO point with little or none BSC in the XO. I'd mount the XO externally anyway. dave

Not quite sure I understand "2nd midbass on the side or top". From the little I think I remember about TMM vs MTM, they require differently tweaked crossovers. I was thinking that TMM would be closest to the current layout. I'd prefer to align them all vertically.

I was hoping someone would have the T/S info, but I guess I'll have to measure them. It'll be a couple weeks. I have to travel for work soon.