Drivers for an IB Sub Project.. Tumult? AV15? Tempests? (1 Viewer)

[JeffSchwartz]

Hiya....

This is my first post on this forum, so please be gentle!

I unfortunately showed a good friend my home theater, in which i installed a quad tempest infinite baffle subwoofer, and his jaw just hit the floor when we watched the opening scene from the Lord of the Rings DVD (Sauron's destruction). He wants me to build one for him. (surprise, surprise)

As time has marched on since I built mine, the AV15 from stryke is soon to be released, as will the Tumult from Adire. which would perform better in an IB setting? Or just do the tempests again?

2 Tumults, 4 Tempests, 4 AV15's ???? Something else?

Extension down low is important, as is the sound quality. SPL's are just icing.

For the sake of argument, lets assume we will add any of the QSC RMX amps to drive them (as I drive my tempests with one).

He is not made of money, but any reasonable config will be considered (cap at $1000- $1200). The room is 16 x 26 ft x 7 high.

What do you guys (and ladies, to not offend) think?

Thanks, Jeff

 

[Rick Guynn]

I would probably just go with the Tempests again. In that size room, 2 should not be too stressed. I am running a dual-Tempest IB in a 14x22x8 room with no problems. They extend plenty low, and you might be suprised at the room gain he could get at the lower freqs, which would keep the overall system at a nice rumble down low. What's more is that with only two Tempests, you could drive them with an inexpensive plate amp with no problems.

RG

 

[Jack Gilvey]

Four of the 15" Dayton IB woofers from PE would likely be great also, $109 each if getting more than two.

 

[Scott Simonian]

I second the 2 to 4 Daytons.

 

[Jeff Hoak]

I just finished my IB and used the Daytons listed above. I'm VERY impressed. I recommend them.

My listening area is approx. 14' x 18' with a ceiling that slopes up from 10' to 19'. A pretty good bit of volume in that room but just 2 of the Daytons do a great job. I can only imagine what 4 would do.

 

[JeffSchwartz]

Thanks for all the replies so far!

As an added question, what kind of wattage do you use for your drivers (for those who have them running) and what do you think the proper amount would be for the others listed?

(I am running my 4 tempest setup with a RMX850.. not exactly the wattage king, and it is more than enough)

Thanks!

Jeff

 

[Dustin B]

The Tempest/Dayton will be plenty happy with 100-150W per driver. The Tumult should have 300W or more per driver. The AV15, I'm not sure, somewhere in between the two anyways.

 

[Bill Fagal]

what kind of wattage do you use for your drivers (for those who have them running) and what do you think the proper amount would be for the others listed?

A lot depends on where your crossover is. If you're crossing to 3-way mains at 50Hz, you're going to need a lot less amp on your IB than if you're crossing to bookshelfs at 120Hz. Remember, at 20Hz most IB'd woofers will exceed Xmax at far less than 100W.

Bill

 

[Dennis XYZ]

If you're crossing to 3-way mains at 50Hz, you're going to need a lot less amp on your IB than if you're crossing to bookshelfs at 120Hz.

I don't believe that's true if you want your sub to have flat frequency response. While it's true it requires more power to drive the sub to Xmax at higher frequencies, you won't be doing that. Your max SPL is determined by Xmax at the lowest frequency you want to play and the response will be flat (either naturally or through EQ) from there on up. So, at higher frequencies, you won't be coming anywhere near Xmax and you won't need more power.

FWIW, an amp rated at 60 watts into 8 ohms will drive a single IB Tempest driver to Xmax at 20Hz. A 34W/8ohm amp will do it at 15Hz. 20W/8ohm hits Xmax at 10Hz. IBs are very efficient because you don't need to compress the air inside the box.

 

[ThomasW]

According Dan Wiggin's post on the IB Cult forum an IB mounted Tempest will reach it's Xmax limit with 130 watts input at 20Hz

 

[Bill Fagal]

Dennis,
I think we're saying the same thing...

Thomas,
Thanks for the Tempest info. So perhaps it would take ~300W to fully exercise an IB Tumult at 20Hz? At that level, you'd be getting a good dollop of distortion at any lower frequency, I imagine. BL drops like a stone when you get off of that broad XBL^2 plateau.
Bill

 

[Jack Gilvey]

So perhaps it would take ~300W to fully exercise an IB Tumult at 20Hz? At that level, you'd be getting a good dollop of distortion at any lower frequency, I imagine. BL drops like a stone when you get off of that broad XBL^2 plateau.

Plugging the numbers into Unibox, it looks like a Tumult is Vd limited to about 109dB @ 20Hz and would take 1000 watts to get there in an IB (seems high to me). This would still be at or below Xmax, so I wouldn't think distortion should be high yet (if we're defining Xmag as 71% of rest Bl)

 

[Dennis XYZ]

Thomas, I think that 130 watts Dan mentions for the Tempest is the 4 ohm power rating and agrees fairly well with the 60 watts at 8 ohms (120 at 4 ohms) that I calculated. Here's the whole quote from the IB forum.

Dan Wiggins wrote:

We test with 17V drive level (nominal 36W into 8 Ohms; 70W into 4 Ohms) in free air, at 15 Hz. This pushes the Tempest to full linear Xmax, and allows for a quick 10 second buzz/rub/scrape test as well as verifying for oilcanning, lead slap, loose glue joints, etc.

As far as power requirements, IBs need very little power to get up and move. A Tempest in an IB needs around 130W to reach full Xmax at 20 Hz; 750W per driver will simply overpower the unit, from an excursion capability standpoint.

Note his 15 Hz power agrees almost exactly with mine - 34 vs. 36 watts. Then his number jumps way (unrealistically) up for 20Hz. The 8 ohm rating is the one to use at 20Hz because the actual impedance is about 50 ohms at that frequency so voltage, not current is the limiter. The actual power being absorbed by the driver is only about 10 watts because of the high impedance - high voltage but very low current.

Edit: keeping things simple, it requires about 22 volts RMS to drive a Tempest to Xmax at 20 Hz. How that translates into nominal amplifier power is somewhat arbitrary.

Checking the Tumult, it needs an amazing 63 volts RMS for Xmax at 20 Hz. That translates into the equivalent of a 500 watt into 8 ohm amp rating. Clearly, if you have the room for them, two Tempests will be much more power efficient than a single Tumult. You only need about 1/4 the amp rating for the same SPL.