Introduction About the Simulations Sealed Enclosure Designs

Transcription

Exodus Audio Tempest-X Application Guide
1
Introduction
The Tempest-X is a 15” long-throw, low distortion driver from Exodus Audio. It is tailored
to applications that require high output in the lowest octaves. The Tempest-X works great
in a range of enclosures both sealed and ported. The Tempest-X is well suited for Infinite
Baffle applications also. This paper will outline our recommendations for how best to utilize
the Tempest-X.
About the Simulations
All simulations are done with our production T/S parameters using LspCAD Pro. It’s our
experience that these get you close as long as your construction skills are good. If you
build a weak, leaky ported cabinet it is likely to be off. If you brace it well, and build it
skillfully, you will likely get results very close to the models.
All room simulations are done with a 8.5’ (H) x 14’ (W) x 19’ (D) room with the sub position
near a corner, offset by a meter or so. The listening position is centered on the width of
the room 2/3 back and showing a seated (39”) listening position. All room calculations are
done with 1/6th octave smoothing and normalized to 1M. Don’t take room simulations too
seriously, they vary considerably room to room but this give a GENERAL idea of what to
expect.
Sealed Enclosure Designs
Sealed enclosures have a lot of advantages. They are simple to build and make an ideal first
time DIY project. They have very predictable low-frequency attributes, low group delay,
excellent transient response and good extension into the lower octaves.
Sealed enclosures can be sized to achieve different low-frequency attributes. There are
some general descriptions of these attributes that become quite technical. We will keep it
simple and recommend a couple enclosures and give you a good idea of what to expect from
each. Pick the one that fits your application best.
Copyright  2007 Exodus Audio. All Rights Reserved.
1
2
85L (3 cubic feet) with 100% poly-fill
This is just about 3 cubic feet. Parts Express makes a perfect box, the same one as they
use for their subwoofer kit. In fact, we both use the same basket so the Tempest-X would
be a drop-in replacement with zero modifications needed, although you may want to buy some
poly-fill to get the 100% fill (about 40oz should do it). The F3 is about 29Hz and you get
pretty good driver protection. This simulation is using 500W (the 500W is at 8 ohms, you
double it into 4 ohms). The PE amp is supposed to be rated at 1000W so you would be able
to easily get the full output of the driver. With room gain you get very respectable output
down to 25Hz. Most rooms will benefit from pressure vessel gain below 30Hz to the tune
of about 6db per octave. That just about matches your roll-off and you would have the
excursion to do it all the way down into the teens. How musical would this be? At this SPL
level it would be far from musical. Everything in the house will be rattling and most of the
measured distortion in a room would be from things OTHER than the subwoofer. Doors,
shelves, windows and everything not made of concrete will be dancing around.
At more reasonable levels, this would have a full-bodied response. It would be a great rock
& roll sub with plenty of energy in the midbass ranges.
Lets look at something a little larger.
2
3
120L (4.25 cubic feet) Sealed with 100% poly-fill.
This is with the 500W PE amp and I’d fill the enclosure with about 64oz. of poly-fill. F3 is
a very nice 27.5Hz and with room gain you end up with a very nice musical sub that reaches
fairly deep. The larger the enclosure the less demand for power. You could also use the
1000W PE amp and pick-up a little more output. For music you don’t really need it. If your
doing a dual purpose HT/music sub you might want to stretch.
3
4
160L (5.65 cubic feet) Sealed with 100% poly-fill.
This is a nice musical sub with an anechoic F3 of 26.4Hz. It provides good output with a
smooth controlled roll-off not requiring a ton of power to reach full excursion. The more
power you pour into a driver the less linear it gets so if you have the space, larger enclosure
designs will always give you less power compression, deeper output and trend toward more
musical alignments. Hey… MDF is cheap, build them big.
4
5
200L (7 cubic feet) Sealed with 100% poly-fill
I love large sealed subs like this, great extension, musical, good transient response and it
reaches deep with a reasonable amount of power.
The F3 is just under 26Hz but the rolloff below that point is shallower . Can you tell I’m a big fan of large subs? ☺
Nothing really more to say, load it up with about 100oz. of poly-fill, brace it good and you
only need the 500W PE amp to get this baby cooking. I’d remove their subsonic filter or
push it low as possible. You have plenty of protection provided by the acoustic high pass
nature of the box as long if you stick with the 500W amp. Going up to 1000W is not needed.
Ported Enclosures
Everyone loves to get something for nothing. Most of the time it’s an illusion, you don’t get
anything for free. With ported subs, it’s almost true. You can significantly extend the
bandwidth of your sub with a port. You gain a good half octave or more of extension and at
the lower frequencies you can achieve higher SPL at lower distortion. This is the reason so
many commercial subs use ported alignments, its all about output.
Of course it’s not REALLY free. In the world of engineering you have to pay something for
that output. First, you have to buy a port. For most subs that is a trivial expense. For
the Tempest-X its not trivial because you need a LARGE well designed port to handle this
kind of output. A small poorly designed one will chuff and make noise at higher volumes.
5
6
We recommend the 6” Precision Sound Flared port for all Tempest-X ported designs. It’s
not a cheap port, but it’s well designed and you really need this much port area or more for a
driver like the Tempest-X. All of the stock ported designs I’ll show are based upon this
port and used full-length without cutting the center section (should measure 17” long). If
you’re hard-core, you can move up to 8” ports. There are not any easily available commercial
8” ports available. Most manufactures use multiple smaller ports (which isn’t as good as
using a single large one) so you are going to have to DIY something from sonotube or other
material. I’d plan on flaring the input/output of the port if you really want to maximize
output and I’d have a flare radius of an inch.
A word about ported subs, they are easier to damage. Below the port tuning frequency the
driver unloads. Its not protected by the “air cushion” like a sealed design. As a
consequence, it’s a good idea to use a special filter on ported subs. This subsonic filter will
help protect the driver from ultra-low frequencies that it just cannot reproduce. Our
Woofer Widget offers a fully configurable subsonic filter that will fully protect the
Tempest-X from low frequency content when used in a ported enclosure. It will also give you
room measurement and equalization tools. Hint hint…. buy the Woofer Widget!
240L (8.5 cubic feet) Ported and tuned to 19Hz with 100% polyfill
6
7
Lets start small, with a 240L enclosure stuffed with 128oz. of poly-fill and a full length
Precision Sound 6” flared port. You could build a box, about 22” x 22” x 38” or go with a
sonosub. Either will work equally well. Our in-room response goes deep, well into the teens.
This is with the 500W PE amp and a 15Hz subsonic filter. The airspeed in the 6” port is
reasonable (this is max power) so your system is mainly limited by amplifier power. If you
move up to the 1000W amp the system will quickly become limited by the port noise at full
power. The 8” port option will have to be 32” long.
Lets step up a box size.
300L (10.6 cubic feet) Ported and tuned to 17Hz with 100%
poly-fill
This goes a little deeper, and I’ve moved the subsonic filter down to 13Hz. The PE amp has
a third order subsonic filter so this should offer you plenty of protection. The port is the
limiting factor, with port noise becoming an issue before you reach maximum output of the
driver. If you moved up to a flared 8” port (32” long) you could get more maximum output
down near port tuning, and have lower power compression centered on port tuning. If you
want to maximize output your better off moving over to Passive Radiators where you don’t
have the port limitations. This is still with just the 500W PE plate amp.
7
8
340L (12 cubic feet) Ported and tuned to 16Hz with 100%
poly-fill
This baby goes deep.
I lowered the subsonic filter to 12hz, and we get good response inroom down under 15Hz. Once again the port is the limitation and we are still only using the
500W PE amplifier. For this size enclosure, sonosubs really make sense. A 12 cubic foot
MDF box will be big and heavy requiring lots of bracing.
Infinite Baffle
An infinite baffle subwoofer is really just a LARGE sealed box. The sub is typically placed
mounted in the wall, ceiling or floor with one side facing the listening room, and the other
side in an attic, crawlspace, garage etc… The cool thing about Infinite Baffles is that they
can be installed in stealth mode. You can hide them easily and nobody will know you have a
sub in the room until you unleash the dogs. Infinite Baffle Subs really excel at low
frequency extension. They go DEEP and because they are running in “free air” they don’t
need a lot of power. The disadvantage is that they are also completely unprotected from
being overdriven. In a small sealed box the air cushion inside the box will help to prevent
over excursion of the driver. In an Infinite Baffle, you have no such protection. Another
characteristic of Infinite Baffles is that they don’t have as much output up above 20Hz as
does either sealed box or a ported sub. Sometimes the difference is dramatic. In order to
8
9
make up for this, most Infinite Baffle installs use multiple subwoofer drivers. It’s not
uncommon to see 2, 4 or even 8 drivers being used in an install.
Once again, I highly recommend the Woofer Widget. It will allow you to dial-in some sort of
low frequency subsonic filter for protection, give you room measurement and equalization
and overall provide all the signal processing tools needed in any subwoofer install.
For more information on Infinite Baffle Subwoofers I highly recommend going to “The Cult
of the Infinitely Baffled” (Goggle it). A gentleman that goes by ThomasW started the
forum several years ago and he has a lot of resources for those interested in building an
Infinite Baffle subwoofer.
9

Introduction About the Simulations Sealed Enclosure Designs

Transcription

Similar documents

your report here

Shiva-X App Note - Welkom op Bassmasters

Full Metal Jacket

vTuner Internet Radio Rapid Prototyping SDK USB

Bticino 334202 (5 Wire)

COMMERCIAL: Link Media - Everest Lounge, Harrow, UK

Why Aurix?

Halo by Parasound is the pinnacle of our 25 years` experience.

Step # 13 Open up TMPGEnc 4.0 Express and click on “Start a new

Sentry Wireless Headphone Instructions. Please use the

Component DA`s Specification Sheet