Do you think you need a subwoofer?

Dear Dan ed: +++++ " you have to control the bass response if you want the mid and high frequencies to sound good and proper. I assume that this is very much true of systems that use strong SW's. " +++++

THis statement is absolutely true.

The control of the bass response is important but to have that bass is really important too, with out it we can't have proper stereo music/sound reproduction and can't enjoy the complete pleasure of hearing MUSIC.

I know your 10t, and I like it, and you can do a huge improvement in the quality sound of your system with the integration of two subwoofers.

Regards and enjoy the music.
Raul.

Dear friends: This is something important issue that I want to share with all of you:

As you can read in my " system " I use Pneumatic suspension insulators from Audio Technica in my Micro Seiki TT and Van Slike insulators in my two Acoustic Signature TTs, both type of insulators do an excellent job with my TTs.

Last week I receive two additional sets of the same model of Audio Technica insulators. So I installed on the TTs and then the Van Slyke were with out job.

I ask me what could happen if I install below my subwoofers?

What a great surprise: these Van Slyke insulators do wonders in my system. Now I have a cleanest low end, not only more tight but " more bass ", better pitch, better image system, less bass overhang, etc...

This was a revelation for me and in my system. Of course I'm truly happy about.

I'm using the Van Slyke Tri-Orb Heavy ( TOH ), three of them in each sub. Three of them support around 200lbs and four of them over 500lbs: this is important because you can use the Tri-Orbs like the footers/insulators of your whole system raks: think about.

This is the site: http://www.vsengr.com/triorbs.html

Regards and enjoy the music.
Raul.

Dear Downunder: I forgot: +++++ " Don't your amps run the speakers full range down to 22hz?? " +++++

No, my amplifiers/speakers run/work from 50hz up and the self powered subwoofers from 60hz down.

Regards and enjoy the usic.
Raul.

Dear Peepoy2: I think that you own the Trio, right? .
Well, Avantgarde are truly great an very special speaker design. Your model crossover point to the subs module is around 100Hz, I like it.

I think that before you go for the second Velodyne, try to talk with the Avantgarde people because their subs integrated design in the Trio has special characteristics in the crossovers for the subs module can integrate seamless to the horn module.

Now, with the info from Avantgarde you can check if with the Velodyne you can mimic the Avantgarde crossover characteristics and if you can then go for the Velodynes.

Other alternative is that your dealer can borrowed the additional Avantgarde subs modules for you can test in your system.

Regards and enjoy the music.
Raul.

Dear Todd: +++++ " It appears as though you advocate using a crossover to take the low freq. information away from the main speakers (only have the sub handle low freq, as opposed to running both subs and speakers full range). " +++++

Yes, this is the main idea. You can do this using the internal crossover of the subs and running the signal to your main amplifier from each sub after the signal ( that comes from your preamp ) pass through the sub internal crossover.
You can do it, too, using an external crossover to run the signal to the main amplifiers. The Pass and Bryston crossovers are very good ones for this application.

+++++ " If the main speaker is a monitor that is -3db at 40hz, is it really necessary to use a crossover? " +++++

Yes, absolutely. Please read carefully at: http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&27&4#27

Regards and enjoy the music.
Raul.

Dear friends: Something that works very well with my Velodyne subs: I mass loaded ( top panel ) with around 25kg.

This can work with your subs. Try it and decide.

Regards and enjoy the music.
Raul.

Dear Audiofeil: I'm using " dead weigh " ( smaller than the cover ): the ones that use for " muscle growth excersice " ( the right words are not on my vocabulary ).

You can " see it " ( a little ) in the " picture " of my " system ".

This is temporary. I'm looking for a ( same size ) steel plate with a weigh around 45kgs. Stay tunned.

Regards and enjoy the music.
Raul.

Audiofeil: Yes.

Regards and enjoy the music.
Raul.

Dear friends: As you know the location for the proper streo integration of the subwoofers is really critical. We have to play around with this subject, many times in incredible " location/way ". Don't be afraid about: try everything till you are satisfied.

My subs are in front of the main speakers and side firing eachother. Till today this is the best " location"way " in my room.

Time consuming but with a big sonic reward. ¡ Try hard on this !.

If you can try to read this: http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&31&4#31

Regards and enjoy the music.
Raul.

Dear Scott: Btw, I choose ( too ) 1st order filter for the high-pass on my system. This high-pass filter is inside of my 20.6s. It work for me.

+++++ " So, how to find the proper balance????? " +++++

I think there are no rules here other than: test, test and more tests. Now, why don't contact with the designer/builder of your subs/speakers?

The " spot on " integration of the subwoofers is not an easy task, I take more than six months to do it and today ( time to time ) I still do little adjustements.
I know that this hard work sometimes is very frustating but I can asure you that is worthwhile. Good luck!!

Regards and enjoy the music.
Raul.

Dear friends: This is for the people that already have or want to have or likes REL subwoofers.

The REL subwoofers are a very good ones subs, no question about.

As any one can " read " in the REL owner manual, that the REL design is primarily for " bass reinforcement on full range speakers ". That's why the REL people recomended that their subs must be installed near the corners and why the REL subs ( normally ) works summing-up the left/right channels signal for works in mono way for less distortion. Other characteristic is that the REL subs does not have high-pass filters for a true stereo performance.

The bass reinforcement REL design is oriented to the HT application and not for a " true proper stereo integration of subwoofers for a music/accurate sound reproduction at home ".

Of course, if you like, you can use it in your stereo system but is totally inadequate an inaccurate for the MUSIC reproduction. Maybe you could use, in the right way, the REL subs with the help of an external electronic crossover.

Regards and enjoy the music.
Raul.

Dear Goatwuss: About fast/low subwoofers please read the links on this link: http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&4&4#4

Regards and enjoy the music.
Raul.

Dear Darkmoebius: I'm not very familiarized with the Bailey subwoofers but I understand that has integrated low/high pass filters: why you are using the Paradigm XO?

Regards and enjoy the music.
Raul.

Dear Scott: Good luck with your Edgar integration.

Regards and enjoy the music.
Raul.

Dear Sirspeedy: Remember the REL subs thread that suddenly " disappear?

Well, in your last post you write something like: " I think there will be no improvement in my system taking out the 80Hz and below from my Ascents. "

With all my respects and in this critical issue, what you " think " or what I " think " it does not matters and don't help you. The only way is to TRY IT, you don't have almost nothing to loose: the second hand subs market is a very " healthy " one.

Please read very carefully at: http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&27&4#27

If some day you decide to try you will be shocked with the improvement about.

Regards and enjoy the music.
Raul.

Dear friends: This is an article, that an Auiogoner send to me yesterday, from Audio Perfectionist Journal about the subwoofers subject and doing a Vandersteen review about: this is not the issue, only the statements about the whys of the subs:

ntroduction
Suppose I told you that you could add two
components to your system that would reduce
intermodulation distortion in the midrange by a
factor of two or more, dramatically improve the
resolution of midrange and high frequency detail,
double or triple the dynamic range capability of
your system without changing your existing
amplifier or speakers and improve imaging more
than you can imagine. You would probably be
interested, right? But wait, there’s more.
These same components would allow the
amplifier to maintain tighter control over the
speakers in the mid-bass and lower midrange.
They could extend bass response to infrasonic frequencies
while lowering bass distortion and
improving the system’s ability to accurately convey
the rhythm and pace of music. And these
same components could virtually eliminate the
uneven response at lower frequencies caused by
room standing waves.
Does all that sound too good to be true?
Are you concerned about the possible cost of all
this improvement? If all this is so easily achievable,
are you wondering why you’ve never heard
about it before?
Let me assure you that all these sonic
improvements can be yours and I’ve been conservative
in my estimates of the level of audible
improvement you’ll get. You can have all this for
$2,500 and you can upgrade in two steps of
$1,250 each. If you are starting from scratch, you
may actually reduce the cost of a complete system
by purchasing a less expensive amplifier and a
lower cost speaker model, along with these components,
and end up with better overall performance.
Few people have figured this out and fewer
have spread the news, but it’s all true.
Of course the components I’m talking
about are a pair of powered subwoofers—but not
just any subwoofers. These subwoofers need to
Page 12 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
Page 13 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
have some special characteristics which we’ll get
to in a minute.
Subwoofers?
I’m sure you are shaking your head in disbelief
right now, and thinking that I’ve lost it. You
may have auditioned some popular subwoofer
models and been less than impressed with their
performance and I won’t disagree. Most subwoofers
available today are simply unacceptable
for use in a system designed for critical music listening.
Yes, we have all heard those thunderous
thudpuckers, commonly called subwoofers, that
add to the excitement of movie sound and simply
ruin the sound of music. How can I claim that
these things can actually be beneficial in a highend
audio system?
Here are two reasons that your experience
may conflict with my statements: most subwoofers
weren’t designed for good musical performance,
and most dealers set subwoofers up
poorly, on purpose.
When properly integrated with the system,
subwoofers blend seamlessly with the main
speakers and don’t make their presence known.
But that’s a very hard sell to the average consumer
and selling is the name of the audio game.
Subwoofers are supposed to add bass, right?
After their initial forays into the market,
few manufacturers continue to try to make subwoofers
that accurately represent music. Why try
to educate consumers when it’s easier to just give
them what they think they want? Boom!
Subwoofer makers soon learned what
dealers had already figured out: if they can’t hear
it woof they won’t buy it. Manufacturers started
to build subwoofers with high-Q alignments and
vents in order to provide more “slam.” Dealers
started to set up their demonstrations for maximum
thump, and maximized sales figures.
Awareness of the basic concepts of specialized
bass reproducers faded or was suppressed.
Home theater exacerbated this situation.
People today expect a subwoofer to rattle their
fillings and the exaggerated bass that most subwoofers
deliver is incompatible with accurate
music reproduction.
But there is more to bass than boom—bass
is the foundation of all music. And there is more
to subwoofers than bass. They reproduce bass frequencies
to be sure, but bass extension is possibly
the least of the sonic benefits offered by good
powered subwoofers.
Why Good Subwoofers Improve Sound
In order to provide the benefits mentioned
at the beginning of this article, subwoofers must
utilize a dedicated bass amplifier, and the main
amplifier and speakers must be high-pass filtered
using a passive, first-order device.
A high-pass filter does just what you
would expect: it allows frequencies above the cutoff
point to pass, and blocks frequencies below
that cut-off point. The attenuation of a first-order
filter is 6dB per octave. That means that the signal
will be reduced in amplitude by 6dB, one octave
below the crossover or cut-off point. If the
crossover point is 80Hz (-3dB), the signal level at
40Hz will be -6dB relative to the signal level at
80Hz, and -9dB relative to the signal level in the
midrange. The signal amplitude will continue to
fall at a rate of 6dB per octave as the frequency
decreases.
A passive, single-pole filter at the input to
the amplifier is the only sonically transparent way
to high-pass the main speakers.
The subwoofer amplifier will require a
low-pass filter to prevent frequencies above the
selected crossover point from being sent to the
subwoofer. A low-pass filter passes low frequencies
and blocks higher frequencies.
A subwoofer with an internal amplifier,
commonly called a powered subwoofer, will
require electronic compensation to allow both
infrasonic response and acceptable dimensions for
home use.
Given these stipulations, a pair of powered
subwoofers can provide the following benefits:
Page 14 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
1. Better performance from your speakers.
Full range loudspeakers utilize the same
driver to reproduce both the bass range of frequencies
and at least part of the midrange. For
optimum reproduction of midrange frequencies
little cone movement is required, and a relatively
small driver is necessary to provide quick
response and good dispersion.
Low frequencies require lots of air movement,
demanding greater cone area and more cone
movement. In engineering terms, the back-andforth
movement of the cone is called excursion.
Cone excursion quadruples with each halving of
frequency.
Good midrange reproduction requires the
use of moderately-sized drivers and good bass
reproduction requires lots of cone area, so most
full range speakers compromise the quality of
both bass and midrange by utilizing woofers that
are too small to provide good bass yet too large to
deliver the best midrange quality.
The cone of the 8-inch or 10-inch woofer
typically found in a full range loudspeaker will be
required to make peak-to-peak excursions of perhaps
an inch to deliver audible levels of output at
40Hz and it will have to do this while producing
300Hz (or higher) midrange signals at the same
time. A 6.5-inch woofer will make a better
midrange driver but it will have to work even
harder to deliver low frequencies and IM distortion
in the midrange will rise.
Intermodulation distortion occurs when
one frequency modulates (alters by its frequency)
another. Peak-to-peak cone excursions of an inch
or more, which may be required to reproduce a
40Hz signal, will have a substantial effect on a
signal at 300Hz. The 300Hz signal will increase
slightly in frequency when the cone is moving
towards the listener to reproduce the 40Hz portion
of the signal, and decrease in frequency when the
cone is moving away from the listener. This is
only one mechanism of IM distortion, which is
sometimes called Doppler distortion. There are
other forms of IM distortion.
All dynamic drivers exhibit some nonlinearity
in outward versus inward cone movement.
High cone excursion exacerbates nonlinear driver
response and causes harmonic distortion.
Harmonic distortion occurs when a harmonic
(multiple) or side-band of the desired signal is
produced due to nonlinear behavior of the electrical,
magnetic or mechanical mechanism of the
driver. If you want to reproduce 40Hz and you get
some output at 160Hz as well, that’s harmonic
distortion.
The results of high excursion of the
woofer cone are intermodulation distortion of the
midrange signal and increased harmonic distortion
of the bass signal. And there’s more.
The small woofers required to maintain
reasonable midrange performance in a full range
speaker don’t do a very good job of reproducing
the lowest bass frequencies but they do put a lot
of energy into the speaker cabinet structure and
this is very detrimental to sound quality.
As the woofer cone makes these large
mechanical movements to pressurize and rarefy
air, an equal and opposite force is applied to the
woofer basket, or frame, which is attached to the
speaker structure. This force excites resonances in
the cabinet structure and tries to move the whole
speaker back and forth. Cabinet resonances color
the sound in the midrange. Cabinet movement
distorts high frequencies.
A backward and forward motion of just a
few thousandths of an inch may represent a major
percentage of the total excursion of the tweeter
diaphragm as it attempts to reproduce subtle high
frequency details. The result of structural movement
is IM distortion of the midrange and high
frequencies.
If you are skeptical about the sonic consequences
of woofer energy moving the speaker
cabinet, think about speaker spikes. A reduction in
cabinet motion is the main reason that spikes
beneath the speaker improve sound. Remove the
spikes and see (no, hear) what happens.
As you can see, a full range loudspeaker is
a bundle of compromise. It is asked to perform
many conflicting tasks. There is an old Chinese
Page 15 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
proverb that goes something like this: “man who
chase two rabbits have no meat for dinner.” By
the same token, a speaker that tries to provide
both bass and the rest of the spectrum compromises
the quality of both.
A single-pole, passive high-pass filter at
the input to the amplifier can cure or minimize all
these speaker problems and improve performance
dramatically. This sonically transparent filter will
reduce woofer cone excursion which will reduce
distortion in the bass, midrange and treble as
described above. The result will be better definition,
better imaging, tighter control, greater
dynamic range and a better presentation of the
rhythm and pace of music. The only thing missing—
besides distortion—will be low bass and that
will be reproduced by specialized devices
designed just for that purpose—powered subwoofers.
2. Better performance from your amplifier.
The major energy demands in music occur
at low frequencies. The major current demands
from an amplifier are at low frequencies. When an
amplifier distorts because of demands for power
that it cannot meet, the output waveform is flattened
at the top and bottom. This distortion is
called clipping because the positive and negative
signal peaks have been “clipped” off.
Amplifier clipping becomes evident at
high frequencies but clipping is almost always
caused by energy demands at low frequencies that
exceed the capability of the amplifier.
Clipping is the primary cause of speaker
damage because a clipped waveform “fools” the
crossover network in the speaker which then passes
high power to the high frequency drivers.
An amplifier in normal use will be clipping
at least occasionally. The percentage of time
that the amplifier is driven to the point of clipping
or beyond will have a profound effect on sound
quality. As the amplifier approaches clipping the
sound will become slightly hard, then harsh, and
then, as the amplifier clips, a shattering distortion
will be heard. This distortion eventually destroys
tweeters and crossover networks.
A single-pole, passive high-pass filter at
the input of the amplifier can eliminate all these
distorted sounds and make the amplifier sound
smoother and more relaxed. The amplifier may
seem to be three times more powerful. Removing
the huge low frequency current demands from the
amplifier, by reducing the level of the input signal
at low frequencies, allows the amp to coast along
with lots of power in reserve. The system will
play at much higher levels with much lower distortion,
providing a greatly improved listening
experience.
The high current necessary for accurate
bass reproduction will be provided by specialized
amplifiers designed just for this purpose—the
amplifiers in the powered subwoofers.
3. Better bass.
Designing a product to perform a very
specific task requires less compromise.
Subwoofers are designed to reproduce a small
range of frequencies at the lowest audible range.
That’s about as specific as it gets in audio.
When compared to full range speakers,
powered subwoofers can provide the following
advantages: more cone area, greater linear excursion
capability, more amplifier power at low frequencies,
and electronic compensation for falling
output at the lowest frequencies. Subwoofers can
also have smaller, stiffer, less resonant enclosures
and can be placed in the optimum position to
introduce bass energy into the room.
Eliminating the compromised bass output
from the main speakers by high-pass filtering the
input signal to the amplifier will dramatically
improve the quality of reproduction in the midbass
range. Improving the mid-bass provides a
better sense of rhythm and pace and makes it easier
to follow the tune of the bass.
4. Better room interface.
The pressure-zone microphone (PZM) was
developed after it was determined that smooth frequency
response at lower frequencies could not be
Page 16 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
obtained from a stand-mounted microphone due
to interactions with the room boundaries. Placing
a conventional microphone on the floor smoothed
the response curve but caused a gradually rising
bass output. Compensating for this bass rise gave
us the PZM microphone. A similar effect occurs
with speakers.
For good imaging and midrange detail full
range speakers must be placed well out into the
room. Bass response from these speakers will be
uneven due to room interaction. This phenomenon
is frequently attributed to “standing waves.”
Removing bass from these speakers and
redirecting it to a subwoofer placed in the corner
of the room will ameliorate most of these room
anomalies. The subwoofer will load the room
from a pressure zone, smoothing response across
the bass range. Adding a second subwoofer,
placed in a second corner, allows low frequencies
to be introduced from two different positions
within the pressure zones of the room virtually
eliminating bass irregularities. (You must remove
other sources that store and release energy at low
frequencies as described in the room treatment
article.)
5. Reduced system cost.
In a given manufacturer’s amplifier line,
the more expensive models usually offer more
power and little else. In fact, smaller amplifiers
frequently sound better than their big brothers and
they always cost less.
The Levinson 33H mono amps that I use
cost about $15,000 less than the Reference 33
amplifiers from the same company. Both models
are essentially the same design, with the larger
version offering only higher output power.
Most loudspeaker manufacturers offer a
range of models that differ only in their ability to
produce bass. Bigger, more expensive models provide
extended bass response with bigger woofers
and larger cabinets. Except for bass extension, it’s
not unusual to find that the smaller models in a
given line of speakers actually sound better
because they have smaller woofers that offer better
midrange performance and the smaller cabinets
add less box sound. Compare the smaller Dunlavy
models to their larger brothers for example.
The Vandersteen 3A Signature speakers
that I use in conjunction with a pair of 2WQ subwoofers
deliver 90% of the performance of the
Vandersteen Model 5s for 60% of the price (3A
Sigs and two 2WQ subwoofers cost about $6,000
and Model 5s sell for about $10,000). My speaker
system delivers a time- and phase-accurate
response over a usable range of 18Hz to 30kHz.
What other speakers can offer that for $6k?
Some reviewers claim that the 3A
Signatures lack the “detail and definition” of the
Model 5s. You may find this puzzling because
both models share identical midrange and tweeter
drivers and use essentially the same crossover network
in this range. Why the perceived performance
difference? Model 5s have a slightly more
inert cabinet structure and they have built-in, powered
subwoofers.
The use of powered subwoofers can allow
a smaller amplifier and a pair of lower-priced
speakers to equal or outperform their more expensive
counterparts. The result is better sound for
less money. Who doesn’t want that?
Why Most Subwoofers Don’t Work Well for
Music Reproduction
Not so many years ago, few people were
aware of the concept of specialized bass speakers.
Explaining what a subwoofer was and the sonic
benefits it could provide were difficult tasks
before the home theater craze hit the public.
Today, people are rushing to add subwoofers to
their audio systems to provide the visceral excitement
that only thunderous bass can supply.
Thunderous bass output makes an onscreen
explosion or gun shot more physically
involving but it can also alter the tonal balance, as
well as the rhythm and pace, of music. Most subwoofers
seem to march to the beat of a different
drummer instead of the one who is playing with
the orchestra.
Today the average consumer believes that
Page 17 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
These illustrations compare frequency response (black trace), phase response (purple trace), impedance (yellow trace), and
group delay (blue trace) for the same JBL 2235H 15-inch driver mounted in a second-order sealed enclosure (above) and in a
fourth-order vented enclosure (below). You can learn a lot about the performance trade-offs involved in the choice of vented
versus sealed enclosure design from studying these graphs. In my opinion, the trade-offs make vents acceptable for use in full
range speakers and totally unacceptable for subwoofers that are meant to reproduce music. A conventional vented design offers
inferior performance in every area except one: output level capability.
the only purpose of a subwoofer is to add bass
and many music purists derisively refer to them as
“fart boxes.”
There are many reasons why boom-box
subwoofers may do a good job of reproducing
explosions and perform poorly when reproducing
music.
1. Phase shift and group delay cause subwoofers
to start late.
Picture a marching band with the bass
drum following about a block behind the rest of
the players and you’ve got a pretty good image of
the major problem with most subwoofers—the
sound they produce is just out of step with the rest
of the music. There are many reasons for this but
most revolve around phase shift and group delay.
Acoustic phase in this instance has to do
with the time relationships of the launch of air
pressure waves towards the listener. Phase shift
that varies with frequency alters the time relationships
between different frequencies. A resonance
in the pass band causes phase shift. Filters cause
phase shift. A speaker in a box is a filter.
When two elements like a subwoofer and
a main speaker have an overlapping frequency
range, or are reproducing different parts of a single
note, such as the fundamental and the harmonics
of that fundamental, you want both to be in
step. If the subwoofer cone pushes out when the
main speaker’s woofer cone is moving inward,
things get out of sync.
Group delay is a complex concept. It is the
negative of the derivative of the phase curve with
respect to radian frequency. Group delay describes
how well the time relationships between a small
group of frequencies are preserved within a narrow
range of frequencies. Time delay and group
delay are not necessarily equivalent but a delay to
one group of frequencies changes its time relationship
to the rest of the spectrum.
Look at the illustrations on page 17 comparing
phase response of vented and sealed enclosure
designs. Trying to synchronize the phase of
the main speakers and the subwoofer will be diffi-
cult with a sealed enclosure subwoofer design and
virtually impossible with a vented design because
of phase shift as the system passes through resonance
in the pass band. Note the 17ms group
delay at the 32Hz tuning frequency of the vented
design.
Subwoofers with a fundamental resonance
in the pass band and a steep slope low-pass filter
at the input will produce output that is delayed in
time relative to the main speakers, and this delay
will vary with frequency.
Subwoofers that start late sound slow and
plodding. They distort the overall waveform even
if their own distortion products are low.
2. High Q makes subwoofers stop late.
An electrical filter will oscillate or ring, to
some extent, after the signal stops. The steeper the
slope of this filter, the more it will ring. The higher
the “Q” of this filter, the more it will ring.
Mechanical filters work the same way. In
fact, all the mechanical properties of a loudspeaker
can be expressed with electrical equivalents and
modeled by electrical circuits.
A woofer in an enclosure is a high-pass filter.
It passes frequencies above the cut-off or low
frequency limit of the design and the signal rollsoff
below this point at a rate determined by the
design. A sealed box acts as a nominal secondorder
high-pass filter and a vented enclosure will
typically display fourth-order high-pass characteristics.
The vented design will ring (oscillate)
about twice as much as the sealed design after the
signal stops.
The “Q” of the mechanical system affects
oscillation, too. System “Q” defines the shape of the
response curve and the amount of damping to overshoot
or ringing (oscillation after the signal stops) that
the system will provide.
Asealed enclosure with a Q of .5 is considered
a “critically damped” alignment with a step response
that has no overshoot. For a given driver, a Q of .5
requires the largest box. This low-Q alignment has a
downward-sloping response curve but offers the best
possible transient performance and the lowest frequency
extension at -10dB.
Page 18 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
Asystem Q of .577 is a Bessel alignment
which has the most linear phase response and offers
slightly less damping.
When Q =.707 we have a Butterworth alignment
with the flattest amplitude response. This is the
most common alignment for “high-end” subwoofers
because it offers a “full” sound which is still well controlled.
System Q near 1.0 delivers a peaked response
but allows the smallest box size still considered by
some to be high-fidelity. Asubwoofer with a system Q
over 1.0 is a boom box with a peaked response curve
and lots of overhang. Guess where most home theater
subwoofers fall.
Subwoofers that play on after the signal has
stopped (due to oscillation), sound slow and muddy.
The Q and slope of the high-pass filter formed
by the subwoofer acoustical system has a major effect
on the sound of the bass the subwoofer produces, but
there’s more. The subwoofer is a mechanical high-pass
filter but it must be used with an electrical low-pass filter
and those cause problems as well.
3. Steep filter slopes and direct-radiating drivers.
Most subwoofer designs include one or
more drivers that radiate directly into the room.
It’s commonly assumed that subwoofers shouldn’t
be allowed to encroach on the midrange where
they perform poorly so the conventional wisdom
mandates a steep-slope low-pass filter to prevent
output above the bass region. There are some
drawbacks to this approach.
Page 19 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
This illustration shows the effect of system Q on frequency response. Notice that the low-Q alignments start sloping down sooner but
ultimately extend lower in frequency at the usable low frequency limit of -10dB. Remember that the low-Q alignments provide far better
damping to oscillation after the signal ceases.
A low-pass filter with a fourth-order slope
will cause another complete phase rollover,
increasing signal delay. Even with this steep attenuation
curve, side band distortion will still be
audible if the driver radiates directly into the
room.
All drive elements will break-up (display
non-pistonic cone behavior) at some frequency.
Filtering below this frequency prevents the signal
from stimulating this behavior. Many other anomalies
such as cone resonances, surround reflections
and “flapping,” magnetic nonlinearities and basket
ringing will remain audible as side-band distortion
even without frequency-specific stimulation. And
some midrange frequencies will still pass through
the filter at attenuated levels.
Midrange signals (even at low levels) and
side band distortion detract from the quality of
sound from the main speakers and draw attention
to the position of the subwoofer which should be
spaced away from the main speakers.
4. System resonance in the pass band.
Removing resonances from audio components
is generally considered to be a good idea but
subwoofers are designed to create resonance.
A vented subwoofer has two resonances
right in the middle of its pass band. The vent resonance
is tuned to play at frequencies where the
output of an unassisted driver would be falling.
Much of what you hear from a vented design is a
production of the subwoofer rather than a reproduction
of the signal.
Sealed enclosures are better with only a
single resonance in the pass band. One is better
than two, as you can see from the graphs on page
17, but none is better yet as we’ll see later.
When the subwoofer passes through a resonance
a big shift in phase occurs. Look at the
graphs of phase response for sealed and vented
enclosure designs and see the effects of resonance
on phase. (System resonance occurs where the
impedance peaks. Note the single peak in the
graph of the sealed enclosure and the dual peaks
in the graph for the vented enclosure. The dip
between the impedance peaks indicates the tuning
frequency of the vented enclosure.)
Subwoofers with a resonance in the pass
band will tend to emphasize the frequencies
around this resonance. The higher the Q the
greater the emphasis. Ever hear the term “onenote
bass”?
5. Dissimilar amplifiers for high and low frequencies.
A powered subwoofer may have an internal
amplifier that is designed for optimal performance
when driving the specific load of the subwoofer
drivers. This amplifier will almost always
have electrical compensation for the falling
response of the subwoofer driver(s) which will
typically be housed in an enclosure that is smaller
than ideal—because nobody wants a subwoofer
the size of a refrigerator in their living room.
A perfect subwoofer amplifier and the
amplifier that is best suited for driving the main
speakers may be very different electrically and
sonically. For instance, a bipolar solid-state ampli-
fier will offer the best performance for bass but a
MOSFET or tube amplifier may sound better driving
the main speakers.
Transfer function is a measurement that
compares the frequency and phase response of the
output from a device under test to the input signal.
If the transfer function of the main amplifier is
very different from the TF of the subwoofer
amplifier, this sonic dichotomy may have a negative
impact on overall sound quality.
Making a Subwoofer to Play Music
A subwoofer should march in step with the
rest of the band and stop playing when the song
has ended. Most do neither.
Subwoofers should be positioned in the
room corners to properly load the room from pressure
zones, creating the smoothest bass response.
If the subwoofer has a “Q” higher than .5 (most
do) it will exhibit a rising response when placed
in a corner.
So how can a subwoofer be designed that
Page 20 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
doesn’t suffer from the performance deficits
described above?
We can eliminate the problem of subwoofers
that start late by blending the subwoofer
and the main speakers using a first-order
crossover for transient-perfect phase response.
This filter system can be implemented in an
unusual way: the high-pass section can be placed
at the input to the amplifier driving the main
speakers and the subwoofer amplifier can sample
the output from this amplifier, including its sonic
signature and phase characteristics. The subwoofer
amplifier can have its frequency response
tailored to compensate for the falling response of
the input signal and the falling response of the
acoustic system that is operating primarily below
system resonance. (More about that in a minute.)
Blending the amplifiers in this way will
ameliorate the discontinuous sound created by
dissimilar amplifier designs driving different parts
of the spectrum.
We can eliminate the overhang of subwoofers
that stop late by designing for a target Q
of .5 to achieve critical damping, along with the
greatest usable bass extension, and to allow corner
placement without a rising low-end response.
The driver(s) can be slot loaded to
mechanically filter out side band distortion and
midrange frequencies. And the system can be
designed to operate primarily below the fundamental
resonance so that no resonance can cause
sonic emphasis or phase shift in the pass band.
This all makes perfect sense and I’d like to
take credit for thinking it up all by myself. But I
didn’t—Richard Vandersteen did. What I have just
described is the Vandersteen 2WQ powered subwoofer
which has been subtly but continuously
refined since it was first brought to market sixteen
years ago. It is the most sophisticated product of
its kind available today.
The Vandersteen 2WQ Subwoofer
The Vandersteen 2WQ subwoofer is completely
unique in a number of ways. It takes
advantage of the fact that loudspeakers in sealed
enclosures offer very predictable amplitude and
phase response characteristics at frequencies
below the fundamental resonance of the system.
The 2WQ operates primarily below fundamental
system resonance to provide frequency and phase
linearity that cannot be achieved by conventional
designs with resonances in the pass band.
It uses a phase-perfect first-order crossover
with special characteristics. The 2WQ samples the
output from the amplifier that is driving the main
speakers for better system integration.
It uses feed-forward error correction to
prevent output errors before they occur and a
unique protection circuit that does not compress
signal dynamic range. The 2WQ will not produce
audible distortion regardless of the frequency or
level of the input signal.
It utilizes three small drivers instead of
one larger unit for greater power-to-weight ratio
and better diaphragm control. The 8-inch drivers
in the 2WQ are slot-loaded to linearize pressure
on the front and rear of the cones and to mechanically
filter side-band distortion.
The cabinet is constructed using constrained-
layer lamination techniques and crossbracing,
resulting in the most inert, resonance-free
subwoofer enclosure that I’ve ever seen.
It has adjustable Q. You can adjust the output
response curve of the 2WQ to suit room
acoustics and placement.
No other commercial subwoofer offers all
these features and virtually all high-quality competitors
cost more.
The 2WQ Operates Primarily Below System
Resonance
Conventional subwoofers operate above
system resonance. They exhibit uneven response
and lots of phase shift as they pass through the
fundamental system resonance which typically
Page 21 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
occurs at the lower end of the pass band.
Designers try to get the resonance frequency low
because output falls off steeply below this frequency.
A vented design with a B4 alignment falls
at 24dB per octave and a sealed design with a Q
of .7 falls at 12dB per octave below resonance.
Take a look at the illustrations in the previous article
to see what happens to phase.
A driver mounted in a sealed enclosure
with a Qtc (total system Q) of .5 will have an
amplitude response curve that falls in a linear
fashion at about 8dB per octave below system resonance
with limited and linear phase shift. Output
will theoretically extend down to DC without the
sudden drop-off and phase shift that occurs when
conventional systems pass through resonance.
This predictable and linear frequency and phase
response is easily compensated for with electronic
correction in the amplifier to produce ruler-flat
output to subsonic frequencies.
Since output is more linear below system
resonance and flat response can be achieved with
amplifier compensation, why not design a subwoofer
that operates below resonance rather than
above it? That’s just what Vandersteen has done.
The result is a subwoofer with virtually no
resonance in the pass band, minimum group delay,
linear phase response, flat amplitude response to
subsonic frequencies, critical damping and a low
system Q making it suitable for corner placement.
A Better Blend with the Main Speakers
The Vandersteen 2WQ subwoofer is integrated
with the main speakers using a unique system
that is not a crossover in the usual sense.
Transitions between the subwoofer and the main
speakers are made with gentle 6dB per octave
slopes using phase- and transient-perfect firstorder
filters that are completely transparent.
Page 22 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
This illustration shows the amplitude and phase characteristics of a sealed enclosure subwoofer with a Qtc of 0.5,
at frequencies below system resonance which, in this example, is 40Hz.
A passive, first-order filter is inserted at
the input to the main amplifier. This filter causes
the signal to the main amplifier and speakers to
roll-off at 6dB per octave below 80Hz.
A 300 watt subwoofer amplifier, designed
specifically to deliver high current into the low
impedance load of the three drive elements, samples
the signal at the output of the main amplifier
and compensates for the roll-off to produce flat
output from the subwoofer. The output from the
subwoofer amplifier is tailored to produce firstorder
low-pass response above 80Hz and a rising
response below 80Hz to compensate for the
falling response curve of the filtered input signal
as well as the falling output response of the subwoofer
which is operating primarily below system
resonance.
Output that could exceed the power limits
of the amplifier, or the linear excursion limits of
the drivers, is prevented by dynamically raising
the low frequency cut-off point rather than compressing
the signal. A unique circuit analyzes the
input signal and dynamically alters the feed-forward
error correction characteristics to accomplish
this feat. The 2WQ cannot be driven to produce
audible distortion under any conditions, yet
it never compresses the dynamic range of the signal,
maintaining the natural rhythm and pace of
music regardless of level.
A passive, first-order high-pass filter at the
main amplifier input is completely transparent so
the sound from the main speakers is not negatively
impacted in any way and all the positive bene-
fits listed in the Subwoofers From a High-End
Perspective article can be realized.
Sampling the output from the main ampli-
fier passes along the sonic and electrical characteristics
(particularly propagation delay) of that
amplifier to the subwoofer system for a better
blend between the subwoofer and the main speakers,
even if the main amplifier is a tube or MOSFET
design. This results in superior integration
between the subwoofer(s) and the main speakers.
Less Audible Distortion
In addition to the feed-forward error correction
system and the specially-designed internal
amplifier, the 2WQ uses several other distortion
reducing techniques.
Three 8-inch drivers have the combined
cone area of a single 14-inch unit but three motors
can provide far better control over the lighter,
stiffer cones. Smaller cones produce less sideband
distortion than larger, more flexible cones,
and any distortion that remains will be at higher
frequencies which can be mechanically filtered by
the indirect radiation path.
These three drivers are slot-loaded providing
an indirect radiation path into the room. Slotloading
the front of the drive elements equalizes
the pressure on the front and back of each
diaphragm making resistance to fore and aft
movement more linear.
A driver in a sealed enclosure “sees” a
diminishing volume of air and increasing pressure
within the box as the cone moves inward, and an
increasing volume of air and reduced pressure as
the cone moves outward. Covering the front of the
driver(s) with a plate so that radiation from the
front of the drive elements enters the room
through a slot or slots between this plate and the
enclosure is an attempt to compensate for this
phenomenon.
Slot-loading provides a reduction in distortion
by linearizing cone motion and also acts as a
mechanical low-pass filter to absorb residual distortion
products at higher frequencies. This
mechanical low-pass filter is far more effective
than a steep-slope electrical filter for the reasons
described earlier.
The cabinet is elaborately constructed
using constrained-layer laminates and cross bracing
to completely eliminate panel resonances and
spurious noise. The 2WQ enclosure feels like a
solid block of material. Rapping on any panel is
like banging your knuckles against a rock. Panel
flexing is simply out of the question.
Page 23 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
Caveats
The Vandersteen 2WQ subwoofer provides
tightly-controlled bass that is “critically damped”
and limited in output level compared to a typical
home theater subwoofer. Two units will be
required in all but the smallest rooms to provide
the THX-recommended output level of 105dB at
35Hz. I recommend using two subwoofers anyway
and 105dB is much too loud for music listening
so I don’t see these as problem areas.
Tightly-controlled bass that is perfect for
music may not satisfy explosion fans who use
their audio systems for both music and home theater.
Vandersteen makes another subwoofer, the
V2W, for these folks. It looks the same but trades
some control and integration for the ability to play
much louder.
Other subwoofers that offer excellent performance
for those with a strong home theater
bias include many of the M&K models and the
Bag End InfraSub. These subwoofers will still
perform well on music and deliver more visceral
output. Don’t use their high-pass filters. Choose a
passive single-pole filter instead.
Best Value
In my opinion, the Vandersteen 2WQ is
the best subwoofer available for reproducing
music regardless of price, and the price is a mere
$1,250 each! If that’s not a bargain, I’m a bad
shopper. I have four 2WQ subwoofers and they’re
not on “long term loan;” I bought them. I want the
best possible performance and I’m willing to pay
for it, but if the product that offers the best sound
quality also costs less, I won’t complain.
Page 24 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty

Regards and enjoy the music.
Raul.

Dear Tbg: +++++ " I stopped suspending my speakers when I bought the 350 pound per side Duntech Sovereigns. " +++++

I think now you can do it again with your Acapella's !!!!

Regards and enjoy the music.
Raul.

Dear Todd: Congratulations for your choose !!. The high-pass filter is the one that do the crossover for the frecuency range that will handle for the main speakers, example: frecuencies from 80Hz and up; and the low-pass is the filter that send the frecuency range to the sub, example: 80Hz and down.

The parametric EQ allow to perform adjustements with a specific frecuencies, that's it that the filters in a parametric EQ are variable and with a variable Q ( broad band ). In a graphic EQ the frecuencies and the Q are fixed.

Maybe you will have to use both of these EQ. You can know it when you try to do the integration to your system/room.

Regards and enjoy the music.
Raul.

Dear Darkmoebius: What you are hearing is right: "Everything was rather muted in a undefined way. ".

For the low bass reproduction has " means " for our " ears " it has to be working with the midrange sound, other way ( 80Hz and down ) you will heard what you already heard.

Regards and enjoy the music.
Raul.

Dear Darkmoebius: You can try the CD from the original soundtrack film: Sneakers. REL suggest to use it in the four track for test the subs room integration.

Regards and enjoy the music.
Raul.

Dear Darkmoebius: It looks great. I will try this week-end ( if I can ).

Regards and enjoy the music.
Raul.

Dear Todd: I think that the man with the Dynaudio speakers have or a room's problem or a Velodyne High-pass filter problem in his sub.

A high-pass filter is a very simple design subject, there is no " high technology " here or " genius " know-how.

If, like the people of Velodyne say, the high-pass filter of the DD series is the same than in the HGS series: don't worried about, is a good one. Btw, don't worried about that specific phase issue on that thread.

Stay calm.

Regards and enjoy the music.
Raul.

Dear Doug: There are many critical subjects/issues for to have a better quality sound reproduction at home. The integration of two subwoofers in a true stereo way is one of the most critical subjects and where any body can hear the great improvement that we can achieve.
Almost ( before this thread ) no one on this forum talk in " deep " about this sub subject.

We all always are talking and looking for a better quality sound reproduction through our systems: TT, cartridges, tonearms, phono preamp, VTF,VTA, etc... , I think that the sub subject is more important and is time to care about and enjoy all their advantages.

No, I don't think that will be worth to add one sub to your system: you need " room ".

Regards and enjoy the music.
Raul.

Dear Doug: Tks God Emily pass through our country ( twice ) with not many damage like everyone waiting for. Tks for ask.

regards and enjoy the music.
Raul.

Dear Sirspeedy: +++++ " ).They felt that since my speakers had superb output down to 35-40 hz,and since my room was only 22.5x13x8,the "second sub" was not a "Real" necessity! " +++++

As you know your Ascents are not the only speakers that are " superb down to 35-40 Hz ". I can tell you that the moment when you can integrate two subs in a true stereo way in your system: you will be shocked!!. The Sumiko people loose/missed the real subs subject.
Btw, what you think or what I think about is totally irrelevant, what is relevant is a FACT and that fact will tell you anything about: the FACT : " the integration of two subs in your system ", you have to try it, you have to heard it at your place: is the only true way to really knows about.

Regards and enjoy the music.
Raul.

Dear Sirspeedy: +++++ " then any low frequencies are perceived in "mono" anyway!.. " +++++

I don't know at which frecuency you are cutting your REL. But, for example, if the crossover is at 27-30Hz and if the low pass filter is of second to fourth order then your REL is reproducing frecuencies as high like 80-100Hz that does not percieved in " mono way " and that are interfering with the same frecuency range of your main speakers.

Any way, as I already told you what you or I " think " is irrelevant: only the " facts " count.

+++++ " ,you have NOT heard every room,or mine.. " +++++

You are right and I agree with you.

Regards and enjoy the music.
Raul.

Dear Scott and Darkmoebius: You are really trying hard the subs integration on your system. This is the only way to do it. We have to have: patience, very good " ears ", high musical experience, very good reference " sound " ( CD/LP ) and more patience.

+++++ " .When you get it "right",you'll immediately know it,as the system will "open up",while retaining proper "weight"!Best of luck! " +++++

Sirspeedy is right, but that is more easy to " tell " than to do it and that is the whole end of the subs integration.

One tip that works for me was: play a little with music with out bass or very little bass contents ( better with CD than with LP ) and compare with subs and with out subs. With this test you could know if the subs volume and crossover frecuency is on target or near target.

Other tip: for a little time don't do more " subs changes ", stay with what you think is " near to the best integration ": listen to your system for two-three days, then go to listen to a live event ( live music ), wait one-two days before you " play " music again on your system, after this " system break " start again with your system and do the adjustements that you think it needs.
If you can't go to listen to live music, then only do the " system break " for two-three times and " see " what happen.

Regards and enjoy the music.
Raul.

Dear Scott: +++++ " So why does almost everyone put the sub behind the satellites??? Aesthetics? Convenience? Sound? " +++++

I don't know for sure: sometimes for convenience, some times for sound or aesthetics.

When I start the integration of my subs I try at the corners ( behind the main speakers ) but does not work: bass too heavy. I try in line ( outside and inside ) with the mains: terrible. I try others room location till I finish with boths subs in front of the mains facing each other and in " open air " position.

If you take a look on speakers designs some of them have their woofers in a side of the cabinet facing each other: NHT, Coincident, Gallo, etc....

I know that everything about is room dependent but by coincidence like six months ago a friend of mine call me to invite to hear his new purchase: Velodyne DD-18. He owns ML with Levinson electronics.
He explain me all the DD-18 features ( very interesting ) and how easy to find te right position in any room and he explain me that the best position of the DD-18 was in the right corner behind the main speakers and front/firing.

Then we start to hear some music: classic, Jazz, rock, etc.., the sound was good but not good enough for what the system " have to offer ". Something was " wrong " with the bass ( only one subwoofer ).

I suggest him to put the DD-18 side-firing instead front-firing, we do that and Voila!!! the bass problem disappear. He do the measurements through the hardware/software in the DD-18 and he find that side-firing do an improvement in measurements too. Coincidence??

I don't have a sound degree to explain why the side-firing position could improve the bass response, but it works.

Regards and enjoy the music.
Raul.

Dear Scottshannon: Very interesting post.

+++++ " .Keep the xover lower than 80hz if using floor speakers that have bass below 50hz. I prefer 55-60 at the top of the range. " +++++

My floor speakers are flat down to 20Hz. I'm crossing around 80Hz and I'm very satisfied with this.
I already try other crossover frecuencies and the best ( at least in my room/audio system ) was 80Hz. It is the best overall, mean: best bass, mid bass, midrange and high frecuencies sound reproduction perception.

I try the 80Hz crossover frecuency in other room/audio systems and; by coincedence, works very well.

I always recomended to start the subs integration with a crossover frecuency at 80Hz and move from there depending of each room/audio system.

Regards and enjoy the music.
Raul.

Dear Sirspeedy: +++++ " .If anyone wants to add "good" low frequencies,to an already good speaker,then the technology is readily available.The problem,to me,on this thread,is that some of the recommendations may scare away some potential music lovers,with the inference of needing 2 units,or additional crossovers.It is simply NOT true. " +++++

The problem is not on this thread. The problem is your approach about, you are talking of something really different for what this thread is all about.

The thread is extremely clear and is not a thread for to " add good low bass " like you say, this subject is for other different thread.

I urge you to read again an very carefully this link thread:

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&27&4#27

Here are the targets of this thread. Your concept is an old one ( I respect that ) an different from the whole subwoofers subject explain in this thread.

Please don't be or don't do that others people can be confused about.

Of course that the integration of two subwoofers in a true stereo way has its own trade-offs: need space room, two subwoofers, money, ettc., but what we can get for these trade offs in quality sound reproduction you can't imagine and every trade off about is justify. This is up to what any one want to have about music sound reproduction through their own audio system.
I can assure you and to any one: nothing come close to the integration of two subs in a TSW. Period.

Regards and enjoy the music.
Raul.

Dear Sirspeedy: I understand what you mean and I agree with you.

+++++ " .We are still talking about low freq performance " +++++

Here it is our differences: you are talking about low freq performance and I'm talking about the whole frecuency range where the low freq is only a part of it. That's all.

+++++ " So I know exactly what you are talking about. " +++++

Maybe here is the problem: that you " think " what I'm talking about, but your posts tell me others things. Who knows?

Regards and enjoy the music.
Raul.

Dear Speedy: Now we can be in the same " channel ".

Regards and enjoy the music.
Raul.

Dear Scott: I understand the why for only one sub. But the test that you do with the second sub tell you that you can do an improvement in a future when you already want it.

Your test is very educational to all of us. Tks for sharing your experience about.

Regards and enjoy the music.
Raul.

Dear Carlos: It will be very interesting for all of us to know your points of view about the subs integration, now that you already have both subwoofers.

Regards and enjoy the music.
Raul.

Dear Skushino: I read the second link that I think is very interesting about the subwoofers subject. All the live and computer experiments tell us many things, that one with 5,000 subwoofers ! ! !!!.

At the end they found that the near perfection about LF it can have it with four subwoofers but they conclude that we can have a very good LF performance with two subwoofers ( and very practical ), this is what they find it:

+++++ " Two subwoofers is very nearly
as good and has very good low as good and has very good low
frequency support as well. " +++++

I think that we are in the " right road ".

Tks for the links. I will take the time to read the other one.

Regards and enjoy the music.
Raul.

Dear Scott: The audiholics link is a good one too, but is more dedicate to HT systems. In this link there are some interesting facts in the: Setup Tips.

Tks for share with us these info. Is really educational.

Regards and enjoy the music.
Raul.

Dear Stringreen: IMHO the subwoofers help to any audio system in many ways other than improve the low bass response.

Please read here: http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&27&4#27

Regards and enjoy the music.
Raul.

Dear Doug: You are always welcome. Please let me know if you are ready to do it.

Regards and enjoy the music.
Raul.

Dear Truthseeker: I agree.

Regards and enjoy the music.
Raul.

DEAR FRIENDS: There is a subject that maybe is not very clear about the integration in a true stereo fashion of powered subwoofers with " full range " speakers like Dynaudio Evidence/Temptations, Dali Megaline, Wilson Maxx2, etc, etc,...

We can think that with a FRS the integration of two powered subwoofers can't do any help to improve the quality sound reproduction. I can tell you that even with FRS the integration of subs can help a lot, let me to give my opinion about::

- That elusive full octave in the low bass is a headache for any one, especially for the loudspeaker manufacturers: they have to choose very carefully the right trade-offs about.
In the other side, we the FRS customers have to choose the right amplification device for really " take-out " and " live " that marvelous low bass reproduction through those FRS: a very hard task, it does not matters the speaker design and the amplifier design.

- There is no single external / stand alone amplifier that can work or do a better job than a low bass dedicated amplifier like the one that comes with a powered subwoofer:
think that this dedicated bass amplifier was designed/tailored to match every single woofer parameter: impedance, frecuency response range, damping, power, distortion, etc, etc,...

- It is not only this dedicated amplifier what makes this subwoofer approach/technology ideal to handle the low bass octaves.
The driver/woofer is designed/tailored too for that specific frecuency range.
There is no passive FRS, at any price with any amplifier, that could beat a self powered subwoofers in that frecuency range. When you have and hear the subs on your system you never can live again with out those subwoofers.

Here we have to remember other important issue: the best subwoofers are SERVO CONTROLLED, this characteristic give to the subwoofer a heavy advantage over a FRS about the low distortion that a well designed subwoofer had against a higher distortions on any FRS.

- With a subwoofer we not only gain with a lowest harmonic distortion but with a lowest intermodulation distortion too. This means better quality sound reproduction.

- Other advantage is that with the integration of two subwoofers in a true stereo fashion to a full range speakers system: the main ( s ) amplifier will be free of those high power consumtion low bass frecuency range: this means too, better quality music sound reproduction. No exception.

- Other advantage with the subs integration is that facilitate the integration of our mains speakers to the room.

Do you think that your FRS audio system sounds great? Wait till you do the subwoofers integration: you will be on music heaven !!!!!!!! Nothing less. Try it.

Regards and enjoy the music.
Raul.

Dear friends: I'm sorry but I'm not sure if the Dali Megaline is a real full range speaker. I think so and that's why I mentioned but I'm not sure.
Anyway, this one could take advante off subs integration.

Regards and enjoy the music.
Raul.

Dear Sirspeedy: +++++ " Servo systems offer their own set of problems(ex:heavy work load on amp). " +++++

I really don't know what you are talking about.

I have my two Velodyne ( servo controled ) HGS-15 for two years and I never " see"hear " any problem about. Its dedicated amplifiers don't have any problem about.

Who tell you rhis?.

+++++ " .Room loading,with a careful ear,costs absolutely nothing,and may ameliorate the need for any aftermarket sub systems. " +++++

Room loading with a careful ear.. Sorry, what do you mean with this?

+++++ " and may ameliorate the need for any aftermarket sub systems. " +++++

My opinion is that f the room enable and if we don't have a self powered full range speakers: any one needs and after market sub system for an improvement in the quality and complete true music sound reproduction experience at home.

I will take your advice about Rel.

Regards and enjoy the music.
Raul.

Hey Sirspeedy: +++++ " problems(ex:heavy work load on amp). " +++++

I'm still waiting for your answers: where or who tell you that? Which the explanation about ?

Regards and enjoy the music.
Raul.

Dear Sirspeedy: Time to time, I really appreciate if you can share with us information from that book that you think is really interesting on the whole subs subject.

Tks in adavance.

Regards and enjoy the music.
Raul.

Dear Tbg: Yes, that is the best start way to set the subs volume system.

Tks, regards and enjoy the music.
Raul.

Dear Mdhhoover: I can see that you are using your subwoofer for bass reinforcement and this is one of the several benefits of the subwoofer integration in an audio system. There are other benefits that could help more to que quality sound reproduction that only bass reinforcement. Please take your time and read this link:

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&27&4#27

Regards and enjoy the music.
Raul.

Dear Eldartford: Please remember that those posts were posted years ago and in one of them you stated that 80Hz crossover frequency.
Thank you for the up-date.

Regards and enjoy the music.
Raul.

Dear Readster: I never had the opportunity to hear the LFM-1 but I think that that subwoofer could integrate better in a home theather system than in a high-end true stereo system.
As a fact that sub goes down " only " to 25Hz and their electronic quality seems to me a little short of a high-end product.

Regards and enjoy the music.
Raul.

Dear friends: I found a Stereophile article that confirm what I already posted about the " must " : two subs in a true stereo way. here it is:

" A simple advantage is that two subs operating in-phase less than one wavelength apart wil generate 6dB more output than a single sub....................If you have two sources arranged in the room so that the left and right woofers are equally far for their respective side walls and equally far from the common wall behind them, most of the standing wave patterns remain the same......the two woofers simply reinforce each other's standing-wave patterns........So while such symetry is desirable at middle and high frequencies for the sake of stereo soundstaging, it may penalize you at low frequencies. This situation change if the bass in the recording is not monophonic. When an orchestra or pipe organ is recorded with widely spaced mikes, bass waves arrive at sligtly different times at each mike. If the bass is not blended into mono for disc mastering, these timing differences will be preserved in playback. The effect is akin to moving one woofer closer or farther away, destroying their simmetry so that the woofers no longer reinforce each other standing-wave patterns.. ......You can achieve a similar result with mono bass by using two subwoofers but placing them asymmetrically.... The bass waves from the two woofers arrive at each boundary surface at different time, producing partial cancellation of the standing waves. These wave interference effects tend to diminish the severity of the peaks and nulls, yielding a more uniform distribution of bass energy within the room. "

Fortunatelly, in my system, I have my two subwoofers in asimmetrically way and I can confirm exactly this very " old " Stereophile statement.

As always I posted: you have to try it: is a " must " to have. Period.

Regards and enjoy the music.
Raul.

Dear Doug: The asimmetry is with respect to the room boundaries ( side/behind walls ) not if the woofers are side firing.

In my case my subs are placed side firing but the right side sub has no simmetry with the left side: the right one is in an almost open boundary.

Anyway, I prefer the subs in side firing position over the front firing. The Coincident are very good speakers and like in the NHT speakers the Coincident has benefits from their side woofers firing, if one of your room side L/R is asimmetric against the other then you are done !!!.

Regards and enjoy the music.
Raul.