Sub Project for (4) 12" MKII Titanic drivers

[tomzarbo]

I have 4 of the last generation 12" Titanic MKII subwoofers, that I bought on sale a few years ago, as well as the 272 watt @ 4 ohm sub amp from Parts Express. I have been modeling some designs for a ported sub with (2) 5" ports 19" long, and a cabinet volume of approx. 9 cu. ft. (I have a very understanding wife!) I want to have 3 subs facing front and 1 facing rear with rear facing ports. I will wire the speakers series/parallel to give a 4 ohm load. I am wondering if I should use the 272 watt amp I have, or upgrade to the 1000 watt amp to get the most out of the excursion capabilities of the subs. The 1000 watt amp would drive the speakers into overexcursion, but the 272 watt amp moderately underpowers them. Possibly the 500 watt amp? Also, is it OK to place multiple speakers in a ported box that is open inside that share ports, or should I try to create a separate box and port for each driver? Any advice/info would be appreciated. I currently have a great 12" ported sub now that is extremely musical, this new sub will primarily be used for "rumble power" for movies/home theater.

[slevy951]

> I have 4 of the last generation 12"
> Titanic MKII subwoofers, that I bought on
> sale a few years ago, as well as the 272
> watt @ 4 ohm sub amp from Parts Express. I
> have been modeling some designs for a ported
> sub with (2) 5" ports 19" long,
> and a cabinet volume of approx. 9 cu. ft. (I
> have a very understanding wife!) I want to
> have 3 subs facing front and 1 facing rear
> with rear facing ports. I will wire the
> speakers series/parallel to give a 4 ohm
> load. I am wondering if I should use the 272
> watt amp I have, or upgrade to the 1000 watt
> amp to get the most out of the excursion
> capabilities of the subs. The 1000 watt amp
> would drive the speakers into overexcursion,
> but the 272 watt amp moderately underpowers
> them. Possibly the 500 watt amp? Also, is it
> OK to place multiple speakers in a ported
> box that is open inside that share ports, or
> should I try to create a separate box and
> port for each driver? Any advice/info would
> be appreciated. I currently have a great
> 12" ported sub now that is extremely
> musical, this new sub will primarily be used
> for "rumble power" for movies/home
> theater.

Wow. I have no opinion on your design other than to say I've been thinking about doing the same thing only going the sealed route with about 3 ft^3 per driver(12 total all sharing same space). I was going to use mine as a TV stand'ish type of piece and finish it with granite on the top to make it more wife acceptable. I already have the 500w amp that I'd use to drive all of them. I do think you may need more power, though.
Ok guys, pros/cons to each????

[bogie]

And I like that...

IMHO, throwing the same power at multiple drivers results in "faster" response - yeah, they're going back and forth 20x a second, but they only have to go a fraction of the distance in that time.

Try the 270 watter first, and if you really, really need the EXTRA SIX DECIBELS, go for the 1,000 watter.

> I have 4 of the last generation 12"
> Titanic MKII subwoofers, that I bought on
> sale a few years ago, as well as the 272
> watt @ 4 ohm sub amp from Parts Express. I
> have been modeling some designs for a ported
> sub with (2) 5" ports 19" long,
> and a cabinet volume of approx. 9 cu. ft. (I
> have a very understanding wife!) I want to
> have 3 subs facing front and 1 facing rear
> with rear facing ports. I will wire the
> speakers series/parallel to give a 4 ohm
> load. I am wondering if I should use the 272
> watt amp I have, or upgrade to the 1000 watt
> amp to get the most out of the excursion
> capabilities of the subs. The 1000 watt amp
> would drive the speakers into overexcursion,
> but the 272 watt amp moderately underpowers
> them. Possibly the 500 watt amp? Also, is it
> OK to place multiple speakers in a ported
> box that is open inside that share ports, or
> should I try to create a separate box and
> port for each driver? Any advice/info would
> be appreciated. I currently have a great
> 12" ported sub now that is extremely
> musical, this new sub will primarily be used
> for "rumble power" for movies/home
> theater.

[diru]

> I have 4 of the last generation 12"
> Titanic MKII subwoofers, that I bought on
> sale a few years ago, as well as the 272
> watt @ 4 ohm sub amp from Parts Express. I
> have been modeling some designs for a ported
> sub with (2) 5" ports 19" long,
> and a cabinet volume of approx. 9 cu. ft. (I
> have a very understanding wife!) I want to
> have 3 subs facing front and 1 facing rear
> with rear facing ports. I will wire the
> speakers series/parallel to give a 4 ohm
> load. I am wondering if I should use the 272
> watt amp I have, or upgrade to the 1000 watt
> amp to get the most out of the excursion
> capabilities of the subs. The 1000 watt amp
> would drive the speakers into overexcursion,
> but the 272 watt amp moderately underpowers
> them. Possibly the 500 watt amp? Also, is it
> OK to place multiple speakers in a ported
> box that is open inside that share ports, or
> should I try to create a separate box and
> port for each driver? Any advice/info would
> be appreciated. I currently have a great
> 12" ported sub now that is extremely
> musical, this new sub will primarily be used
> for "rumble power" for movies/home
> theater.

Get the KILO watt. Don't be wimpy at this point.

[mikebw]

You don't suppose to actually put the TV on top of this do you? I mean that's gonna be a lot of vibration, I wouldn't trust anything to stay on top for long.

> I have 4 of the last generation 12"
> Titanic MKII subwoofers, that I bought on
> sale a few years ago, as well as the 272
> watt @ 4 ohm sub amp from Parts Express. I
> have been modeling some designs for a ported
> sub with (2) 5" ports 19" long,
> and a cabinet volume of approx. 9 cu. ft. (I
> have a very understanding wife!) I want to
> have 3 subs facing front and 1 facing rear
> with rear facing ports. I will wire the
> speakers series/parallel to give a 4 ohm
> load. I am wondering if I should use the 272
> watt amp I have, or upgrade to the 1000 watt
> amp to get the most out of the excursion
> capabilities of the subs. The 1000 watt amp
> would drive the speakers into overexcursion,
> but the 272 watt amp moderately underpowers
> them. Possibly the 500 watt amp? Also, is it
> OK to place multiple speakers in a ported
> box that is open inside that share ports, or
> should I try to create a separate box and
> port for each driver? Any advice/info would
> be appreciated. I currently have a great
> 12" ported sub now that is extremely
> musical, this new sub will primarily be used
> for "rumble power" for movies/home
> theater.

[tc]

> Try the 270 watter first, and if you really,
> really need the EXTRA SIX DECIBELS, go for
> the 1,000 watter.
************************************************

An extra six decibels would be perceived as twice as loud...not something bad to have in reserve for a sub.

Also, considering how heavy this monster would be, it might not rattle all that much.

If you could mount two drivers per side, mirror imaging front/back and couple them in between (fasten a dowel or something between the backs of the motors) creating a mechanical coupling, a bucketload of your energy will be countered for.

Add to that this thing will probably weigh in at 250+ lbs...I'm thinking it's going to be pretty cool!

[Paul O]

I like the idea too, but think facing some drivers in opposite directions will likely introduce comb filtering. The output from the rear facing driver/s has to bounce off the wall and around the cabinet before reaching the listener, which will put it out of phase with the direct radiating drivers. It's akin to using reflex and horn loaded subs together, a general no-no unless you can delay(electronically) the output from the direct radiators.

[cooper]

Paul-

I was thinking using a piece of 18"d sonotube about 18" long, capped with plywood or MDF, and mounting a RS10" on each end. The sonotube would sit horizontally, and I would use all-thread to mount the drivers, and couple them to each other. I hadn't considered the comb filtering effect you just mentioned. Would a 18" round, dividing the sonotube in half solve this problem?

> I like the idea too, but think facing some
> drivers in opposite directions will likely
> introduce comb filtering. The output from
> the rear facing driver/s has to bounce off
> the wall and around the cabinet before
> reaching the listener, which will put it out
> of phase with the direct radiating drivers.
> It's akin to using reflex and horn loaded
> subs together, a general no-no unless you
> can delay(electronically) the output from
> the direct radiators.

[tc]

> I like the idea too, but think facing some

> drivers in opposite directions will likely
> introduce comb filtering. The output from
> the rear facing driver/s has to bounce off
> the wall and around the cabinet before
> reaching the listener, which will put it out
> of phase with the direct radiating drivers.
> It's akin to using reflex and horn loaded
> subs together, a general no-no unless you
> can delay(electronically) the output from
> the direct radiators.

*************************************

Possibly but it might also provide a bit of bafflestep loss compensation too, resulting in an improvement.

Whether or not the waves start cancelling each other out, I don't know. Considering the length of the waves and any subwoofer located within a foot or so of a wall, would that not be the case with all subs?

Could the drivers be placed to the sides and not directly firing into a wall?

I've worked a lot trying to model room responses and have not had much luck. I still seem to get nulls regardless. A lot of things I think may not sound good do, and others that ought to be perfect dont. I think that speaks more towards my adeptness than pure science, however I still think that mechanical coupling and built-in BSC would be a huge plus.

I wish I had the drivers and time to play with, would be interesting to test.

[jyourison]

I recently compared monopole subs to bipole (one on each end firing left and right, and also shifting to firing front and back). There was no cancellation as there would be with dipoles, and the bass actually seemed smoother (less peaking and dipping at the usual nodes) as I walked around the room for either orientation. Could just be my room, but I think it's worth others' giving it a try.

> *************************************

> Possibly but it might also provide a bit of
> bafflestep loss compensation too, resulting
> in an improvement.

> Whether or not the waves start cancelling
> each other out, I don't know. Considering
> the length of the waves and any subwoofer
> located within a foot or so of a wall, would
> that not be the case with all subs?

> Could the drivers be placed to the sides and
> not directly firing into a wall?

> I've worked a lot trying to model room
> responses and have not had much luck. I
> still seem to get nulls regardless. A lot of
> things I think may not sound good do, and
> others that ought to be perfect dont. I
> think that speaks more towards my adeptness
> than pure science, however I still think
> that mechanical coupling and built-in BSC
> would be a huge plus.

> I wish I had the drivers and time to play
> with, would be interesting to test.

[jyourison]

[Paul O]

> Paul-

> I was thinking using a piece of 18"d sonotube about 18" long, capped with plywood or MDF, and mounting a RS10" on each end. The sonotube would sit horizontally, and I would use all-thread to
mount the drivers, and couple them to each other. I hadn't considered the comb filtering effect you just mentioned. Would a 18" round, dividing the sonotube in half solve this problem? Sound dampening material will help obsorbe this reflected energy.

This sounds like a little different situation than the OP's config. With the tube perpendicular to the listening position the propagation time for both drivers should be equal, assuming it's centered and the room is symetrical side to side.
There will be constructive and destructive interference with the primary wave, but it may be more benificial than not. As with all systems, the results very much depend on the listening room and the position and orientation of the drivers, and it's not just the primary wave you have to contend with, but reflections as well.

[tomzarbo]

> You don't suppose to actually put the TV on
> top of this do you? I mean that's gonna be a
> lot of vibration, I wouldn't trust anything
> to stay on top for long.

No TV or ANYTHING will EVER sit on this speaker! Sorry, just a little light-hearted obsessive compulsive behavior! We hope to get a big screen TV in the next 2 yrs. so that idea is out for me. I was planning on an angled design where the front baffle is angled rearward mabey 15 degrees, and the top would also be angled 15 degrees (so nothing could be placed on it!) I suppose I may just try the 272 watt amp and see if it has the guts to do the job, I can always upgrade to the 1,000 watt amp later on.