Shiva-X App Note - Welkom op Bassmasters

Transcription

Exodus Audio Shiva-X Application Guide
1
Introduction
The Shiva-X is a 12” long-throw, low distortion driver from Exodus Audio. It is tailored to
applications that require high output in the lowest octaves. The Shiva-X works great in a
range of enclosures both sealed and ported. The Shiva-X is well suited for Infinite Baffle
applications also. This paper will outline our recommendations for how best to utilize the
Shiva-X.
Sealed Enclosure Designs
Sealed enclosures have a lot of advantages. They are simple to build and make a perfect
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.
Small Sealed Box
The Shiva is our small box champion. Unlike its bigger brother (the Tempest-X) the Shiva
works exceptionally well in unassisted small box applications. Small is relative of course.
We prefer to design around larger boxes simply because deep bass requires drivers with
large swept volumes. Also, large boxes translate to deeper bass with lower power
requirements. Small boxes just do not make for deep bass; don’t let anyone tell you
otherwise. To get deep bass in small boxes takes incredible amounts of power that has to
be dissipated through the voice coil and former of the transducer. It also means that the
suspension of the system becomes highly non-linear due to the “air spring” in the box being
non-linear in comparison to the larger enclosure. Both cause higher distortion and/or power
compression than does running the sub in a larger enclosure at lower power requirements.
Of course not everyone wants subterranean bass. If your interest is mainly in a musical sub
for a 2-channel system, you may actually desire an early cut-off so not to excite so many
room issues. Most 2-channel systems benefit from some re-enforcement of the first &
second octaves but don’t require massive output down low. For those types of systems small
sealed Shiva-X based systems are a very attractive solution.
One other application that is popular for the Shiva is in automotive environments. I’ll state
right now, we didn’t target automotive applications for any of our drivers, but the Shiva ends
up working extremely well in 1.5-2.0 cubic foot sealed enclosures for automotive use. I
don’t recommend the Shiva-X for ported automotive applications simply because of the
difficulty of getting a large enough port in what is a relatively small box.
Starting out small and moving to larger designs:
Exodus Audio Application Notes
Copyright  2007 Exodus Audio. All Rights Reserved.
1
2
1.5 cubic feet (43L) with 100% poly-fill (automotive
application)
The great thing about a car is that you have a small chamber and get tremendous amount of
cabin gain from the small sealed cabin. That being the case, the sub itself can start to rolloff much earlier than you would desire in a home environment. Here is the Shiva-X modeled
in my mini-Van. I know a lot of you guys drive mini-vans. ;-) The smaller the cabin of your
vehicle, the higher up in frequency that it kicks-in. Unless you’re driving a Chevy Suburban
you can count on this as a worst-case situation. With 100% fill (about 20oz. of poly-fill and
goosing the driver with 800W you get a lot of output. I recommend you aim for about
600W into 4 Ohms and if you run it higher, for prolonged periods of time, I neither
warranty the driver nor your hearing. I have a subsonic on this one @ 15Hz but it doesn’t
have much effect on the response. You really don’t need it in this small sealed box.
2
3
2.0 Cubic Feet (56L) with 100% poly-fill (automotive
application)
At 2.0 cubic feet you stuff the box with 30-32oz of poly-fill for 100% stuffing. The large
box requires less power and goes a little deeper. This has 500W @ 4 Ohms on the driver
and the subsonic filter is at 10Hz. The subsonic does almost nothing to the response and its
not needed on this small sealed box application.
3
4
85L Sealed with 100% poly-fill (home audio use)
For home audio use its nice to get a little deeper output. You don’t get the same effect
from cabin gain as you do in car. Here is the Shiva-X in a 3 cubic foot (85L) enclosure
stuffed with 48oz. fill. This simulation is using 500W @ 4 ohms. The Parts Express 500W
plate amp is a good candidate for this application. It has a single band parametric EQ which
can be handy for either extending the response or dealing with a room issue. It provides
plenty of power at a reasonable price for this application. This would be a great sub for
music systems or where having a musical sub is your primary consideration and home theater
is a secondary concern.
4
5
Once again, you get more extension the larger you go and require less power. The 500W
amplifier is capable of driving the Shiva-X past its full linear excursion limit under 24 Hz.
You won’t really get into a problem because this simulation does not take into account
thermal compression, cms non-linear behavior or the drop from BL non-linearities. In other
words, you won’t overdrive the sub with a 500W amp in this box.
You get very reasonable
response down deep due to the relatively shallow roll-off of the sealed box system.
5
6
No surprise here, the larger box goes deeper and requires less power to get there. At this
point we are up to a 4.3 cubic foot box and you get a very musical tight response from the
subwoofer. The larger sealed box designs tend to sound tighter and more musical.
This
sub goes really deep. There are minimal advantages to going with larger sealed designs than
this with the Shiva-X. You get marginally more extension but as you can see from the cone
excursion graph, it requires more driver output than a single 12” driver can really provide to
get meaningful output down low. To get more output lower, you have to either move to a
larger driver or a ported system.
6
7
Ported Shiva-X Designs
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 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 Shiva-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. We
recommend the 4” Precision Sound Flared port for all Shiva-X ported designs. 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).
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 Shiva-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!
All of our ported alignments for the Shiva-X are done with 100% fill. Figure about 16oz. of
poly-fill for every cubic foot of enclosure. We don’t sell poly-fill. Go to Wal-Mart and buy
the stuff the old ladies buy to make pillows. It cost about $3 per 20oz. bag. There are
not really meaningful improvements provided by the “audio grade” materials. They might
perform slightly better but its very marginal and certainly not worth the additional cost for
subwoofer applications. One thing to be conscious of, especially with enclosures highly
stuffed is getting the stuffing near the mouth of the port. Keep the exit of the port clear
from stuffing. If you have to use a little less fill to accomplish that just do it. Don’t stress
if your fill is +/- a couple ounces of fill.
All of the ported designs use a single 4” flared Precision Sound port. I have intentionally
designed them all to use a full-length 17” port. You don’t need to cut it, just glue the thing
together with some PVC cement and install the port in your enclosure. Keep the outlet of
the port at least 3” from any inside wall of the enclosure.
7
8
100L (3.5 cubic feet) tuned to 20Hz with 4” flared port, 17”
long and 56oz of Poly-fill.
Ported alignments give you much better extension into the lowest octave at the expense of
rolling off quickly after that point. If you compare this simulation with the 100L sealed box
you can see that we are getting a significant improvement in output down around 20Hz. This
extra output is provided by the port. This is with the same amount of power, 500W in this
case. You will notice we have an extra graph depicting the “Airspeed in port”. This is an
indication of how fast the air is rushing in/out of the port at this simulated output level. In
this case, the 4” flared port is overloading. Anything above about 14-15 m/S is going to
cause the onset of something called “chuffing”. This is a noise produced by the port as
airspeed becomes turbulent inside the port. It’s a form of distortion in a ported system.
You won’t get the actual output shown in this simulation due to the port compression among
other non-linearities that start to occur at high power. It’s nice to dream though.
So… what do we do about this? Well, there is a dilemma involved with ports. To get lower
air speed you need a larger diameter port. Unfortunately when you use a larger diameter
port you ALSO need a longer port to tune the enclosure to the same frequency. If we
moved up to a 6” flared port it would require a port almost 40 inches long. Try fitting that
8
9
into a 3 cubic foot box. Of course you can build a slot-port. Slot ports are ports that are
built into the structure of the box. A slot port can be made to have a very large crosssectional area and raise the threshold for chuffing. They are not as efficient as flared
round ports at passing air and determining at what point they will chuff is beyond the scope
of this document. For beginning DIYers I recommend sticking with my recommended flared
round ports. If you want more output than the single 4” flared port can provide, I
recommend using one of the Passive Radiator designs shown later.
120L (4.3 cubic feet) tuned to 18Hz with 4” flared port, 17”
long and filled with 64oz of poly-fill
Going with a larger box provides the same benefit as it did in a sealed box; you get deeper
response and require less power to get there. Here we have good response well down into
the teens. I have the subsonic filter set at 14Hz and this provides plenty of protection in
this design.
9
10
140L (4.9 cubic feet) tuned to 17Hz with a 4” flared port,
17” long and 70oz of poly-fill.
This is largest ported box in my recommended Shiva-X designs. If you are willing to build a
bigger box than this to reach deep you are better off looking into the Tempest-X designs.
The cost of the driver is only about $10 extra so it makes sense to upgrade if you’re willing
to live with the larger box.
Passive Radiators
Passive radiators are non-powered drivers that are used almost like ports to provide extra
output. They are non-powered in the sense that the amplifier isn’t connected to them.
From the outside they look like a normal driver and many manufactures make loudspeakers
or subs look more “powerful” by having lots of non-powered drivers.
10
11
Passive radiators have the advantage of not having limitations based upon “chuffing” noise
that we run into with ported systems at high output. Of course you have to design them
such that the Passive Radiator has enough surface area and stroke to deliver the output
desired, but we handle that for you. Passive radiators roll-off a little quicker at low
frequencies but for most of our designs that is a non-issue as the roll-off is outside of the
range of usable output. Passive Radiators have slightly higher group delay and some other
technical considerations but none of these factors are much worse than the ported system’s
behavior.
The other consideration is the Passive Radiators cost more than a port. A port is a passive
device with no moving parts and much cheaper to manufacture than even a non-powered
driver.
To Summarize:
Advantages:
•
•
•
•
•
No chuffing due to excessive air-speed in ports
You can get higher effective output in some designs that are limited by the chuffing
of a port.
They don’t suffer port resonance issues of ported designs with excessively long
ports.
Can keep enclosure size smaller because you don’t take up precious enclosure volume
with a port.
They look really cool.
Disadvantages:
•
•
•
PR’s cost more than do a simple port.
PR’s pay a slight penalty in group delay.
PR’s roll-off below the tuning frequency slightly quicker than does the same ported
alignment.
In my opinion, PRs really make sense when you want to maximize the output of small
enclosures and you have high output subwoofers (like the Shiva-X) that require excessive
port diameters to achieve a proper low-frequency tuning points.
Stay tuned as Exodus Audio will have a PR to go with the Shiva-X & Tempest-X first quarter
of 2008. These designs will be matched to the performance of the Shiva-X & Tempest-X
and provide excellent value in-line with the other Exodus Audio products.
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
11
12
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 smaller sealed box or a ported sub. Sometimes the difference is dramatic. In
order to 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.
Unless you have space constraints, I recommend the Tempest-X for IB applications. There
is absolutely nothing wrong with the Shiva-X used in IB installs but you get more for your
money when you buy the Tempest-X.
12
13
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”. 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.
13

Shiva-X App Note - Welkom op Bassmasters

Transcription

Similar documents

Introduction About the Simulations Sealed Enclosure Designs

your report here

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

Component DA`s Specification Sheet