Subwoofer in phase ...with only one speaker

Subwoofer in phase ...with only one speaker

Hello everyone,

After I installed a single Rel subwoofer into my system I realized
that it would be in phase with one speaker and not with the other.

I explain: My room is just a bit more then 4000 cubic-feet, L shaped.
I set the subwoofer into the left corner behind the left speaker
(Unfortunately this is the only option I have). So, I measured the
frequency response of each front speakers with an real-time analyzer
and I found out that when the phase of the subwoofer is set to 0 the
right speaker's mid-bass frequencies decrease the output considerably.
When I switch the sub's phase to 180 the left speaker's mid bass
portion is sucked in. I checked the wiring, all matches red-to red,
black to black. I thought... maybe I should reverse the polarity of
one of the mains to even up with the sub, but that would screw up the
phase between the two mains. Is there any solution?
Is the distance between sub and mains the cause of this phase
'disparity"?

Any input would be greatly appreciated.
Thank you.

Re: Subwoofer in phase ...with only one speaker

On Nov 12, 6:52 pm, fid <fidelio...@yahoo,com > wrote:

> After I installed a single Rel subwoofer into my system I realized
> that it would be in phase with one speaker and not with the other.

What you are writing is that your satellite speakers are out of phase
with each other? Otherwise, how could the SW be out of phase with one-
or-the-other and *not* both?

A couple of questions:

a) Does the SW have an internal crossover such that it does not feed
full-spectrum to the satellites? This would seem pretty obvious, but I
have to ask.
b) Have you tried (temporarily) placing the SW somewhere else and
measuring the results? Perhaps equi-distant and similar attitude
towards both satellites?

You may be getting "cancellation waves" for lack of a better term -
which makes no sense if there is a good crossover in the SW. *IF*
there is a crossover and *IF* it is adjustable, raise the cut-off
frequency to the satellites and see if that does not solve your
problem.

One last problem that is unusual but certainly possible especially in
rooms with hard parallel surfaces. Are you aware of the concept of a
"standing wave"? Try setting your speakers asymetrically about the
room and remeasuring. You may have to try various configurations
before you determine what gives you the best results.

But, keep in mind your initial statement as-written is questionable,
as properly connected speakers will always be in phase with each
other, all things being equal (no deliberate alterations made).

Peter Wieck
Wyncote, PA

Re: Subwoofer in phase ...with only one speaker

I'd like to mention also that the odd thing is that the Relsubwoofer's
crossoveris set to 22hz. why would it affect the mid bass?

Re: Subwoofer in phase ...with only one speaker

fid <fidelio23f@yahoo,com > writes:

> Hello everyone,
>
> After I installed a single Rel subwoofer into my system I realized
> that it would be in phase with one speaker and not with the other.
>
> I explain: My room is just a bit more then 4000 cubic-feet, L shaped.
> I set the subwoofer into the left corner behind the left speaker
> (Unfortunately this is the only option I have). So, I measured the
> frequency response of each front speakers with an real-time analyzer
> and I found out that when the phase of the subwoofer is set to 0 the
> right speaker's mid-bass frequencies decrease the output considerably.
> When I switch the sub's phase to 180 the left speaker's mid bass
> portion is sucked in. I checked the wiring, all matches red-to red,
> black to black. I thought... maybe I should reverse the polarity of
> one of the mains to even up with the sub, but that would screw up the
> phase between the two mains. Is there any solution?
> Is the distance between sub and mains the cause of this phase
> 'disparity"?
>
> Any input would be greatly appreciated.
> Thank you.

You didn't mention what the cutoff frequency is of the subwoofer's
crossover. Is it 80 Hz? 120 Hz? 200 Hz?

The wavelength of a frequency f is about 1100 / f [ft]. So if the
highest frequency in your subwoofer's output is 100 Hz the wavelength
is about 10 feet. At that frequency, a distance difference of 5 feet
will correspond to 180 degrees out of phase. Of course it's not
black-and-white either - a distance difference of 4 feet will attenuate
the signal somewhat but not completely (theoretically).

So, if you're getting unwanted cancellations in the "mid-frequencies"
I'd say the best thing you could do is lower the crossover frequency of
the sub, down to maybe 60 to 80 Hz.
--
% Randy Yates % "She has an IQ of 1001, she has a jumpsuit
%% Fuquay-Varina, NC % on, and she's also a telephone."
%%% 919-577-9882 %
%%%% <yates@ieee.org> % 'Yours Truly, 2095', *Time*, ELO
http :// www .digitalsignallabs,com

Re: Subwoofer in phase ...with only one speaker

fid <fidelio23f@yahoo,com > writes:

> Peter Wieck wrote:
>> On Nov 12, 6:52 pm, fid <fidelio...@yahoo,com > wrote:
>>
>> > After I installed a single Rel subwoofer into my system I realized
>> > that it would be in phase with one speaker and not with the other.
>>
>> What you are writing is that your satellite speakers are out of phase
>> with each other? Otherwise, how could the SW be out of phase with one-
>> or-the-other and *not* both?
>>
>> A couple of questions:
>>
>> a) Does the SW have an internal crossover such that it does not feed
>> full-spectrum to the satellites? This would seem pretty obvious, but I
>> have to ask.
>> b) Have you tried (temporarily) placing the SW somewhere else and
>> measuring the results? Perhaps equi-distant and similar attitude
>> towards both satellites?
>>
>> You may be getting "cancellation waves" for lack of a better term -
>> which makes no sense if there is a good crossover in the SW. *IF*
>> there is a crossover and *IF* it is adjustable, raise the cut-off
>> frequency to the satellites and see if that does not solve your
>> problem.
>>
>> One last problem that is unusual but certainly possible especially in
>> rooms with hard parallel surfaces. Are you aware of the concept of a
>> "standing wave"? Try setting your speakers asymetrically about the
>> room and remeasuring. You may have to try various configurations
>> before you determine what gives you the best results.
>>
>> But, keep in mind your initial statement as-written is questionable,
>> as properly connected speakers will always be in phase with each
>> other, all things being equal (no deliberate alterations made).
>>
>> Peter Wieck
>> Wyncote, PA
>
> first off thank you for your reply.
>
> I must apologize for not being specific in my question. the two main
> speakers are full range, five drivers floorstanders, rated to 22hz.
> the rel stadium III subwoofer is connected with the typical neutrik
> cable. in paralel (high level?), the crossover setting is 22hz, which
> is what bugs me... the reason I have the sub is to complement only
> the last octave of the sound spectrum.
> I still get this strange mid bass suckuout problem in one of the two
> speakers whenever the sub is activated and dependently from the phase
> setting, 0 or 180, the L or R speakers will be affected.
>
> the mains are in phase with each other. I checked the connections
> several times.
>
> unfortunately the system is located in an L shaped living room. one
> speaker seats in the corner with the sub behind, and the other
> speakeris in the open, meaning that it does not have a side wall and
> associated reflections. just the wall behind.
> I cannot move speakers around, they are heavy and the living room is
> saturated with objects and furniture.
>
> my question is: why the subwoofer appears to be in phase with one
> speaker only -while the two mains are in phase with each other? Is
> phase problrem directly proportional to the distance between sub and
> speakres? I say that because one speaker is definitely closer to the
> sub then the other.
>
> however I could easily live with this "problem",
> I would like to understand why that happens.
>
> thank you.
>
> also I must apologize for my english.

Mike's point about the crossover slope being 12 dB/octave is very
relevent, although I'm not sure we can conclude that is the slope of the
Stadium IIIs' crossover.

I would also add that this problem is exacerbated if you have the level
of the sub pumped up so that "0 dB" of the sub is higher than "0 dB" of
your mains. Regardless of where your level is now, reducing it is sure
to improve the cnacellation problem, but of course it will reduce the
low bass energy as well.

You mention the furniture and speaker weight problems, but just in case
you've got a conceptual error, ideally all the speakers should be
positioned at the same distance from the listening position. The
distance from the sub to the mains is not what's important - rather, the
difference in distance between sub-to-listener and mains-to-listener.
This difference should ideally be 0.

I see only two alternatives: 1) rearrange things so that the speakers
all lie at the same radius from the listener, or 2) add a crossover
system that will roll off your mains and or your sub (or both) more
agressively.
--
% Randy Yates % "The dreamer, the unwoken fool -
%% Fuquay-Varina, NC % in dreams, no pain will kiss the brow..."
%%% 919-577-9882 %
%%%% <yates@ieee.org> % 'Eldorado Overture', *Eldorado*, ELO
http :// www .digitalsignallabs,com

Re: Subwoofer in phase ...with only one speaker

In article <fhnq6g0qje@news3.newsguy,com >, fid <fidelio23f@yahoo,com >
wrote:

> Thank you for your replies and suggestions. Finally I start to
> understand something...
>
<snip>

> Obviously I have standing waves bigger than I can handle. If I
> increase the sub level even at the lowest crossover setting it will
> increase proportionally also those peaks.
>
> I understand that moving the speakers around would change things, but
> my living room is cluttered, that's why I need to learn alternatives,
> if there are any.

The bass energy in a room is much harder to tame than treble, and
increasing it by using sub-woofers makes room dynamics more critical.
IMO the best way to tame resonant frequencies (either reinforcements or
cancellations) is by shifting speakers and furniture. Standing waves
depend on the shape and size of the room as well as the use of large
furniture to break them up or absorb bass.

Sound in general does not respond well to speakers in corners, this
gives great reinforcement to bass frequencies. I prefer to block the
corners with chairs, book cases, etc.

As sound leaves a speaker, it spreads out depending on the frequency.
High treble beams almost straight out in a narrow path, often only 10 or
15 degrees wide. Lower bass goes around corners easily and will leave
the vicinity of the speaker in almost 360 degrees.

So putting your speakers in the corner reinforces the bass up to 4 times
with reinforced frequencies dependent on the distance to the side and
rear walls (as well as to the floor and ceiling). There used to be a
good computer program (BestPlace) that calculated all these
reinforcements.

Taming the bass, and the reflections of all frequencies from flat hard
surfaces, does mean rearranging, but changing room acoustics does make
for dramatic differences.

Have fun.

Greg

Re: Subwoofer in phase ...with only one speaker

On Nov 17, 8:56 pm, Greg Wormald <greg.worm...@gmail,com > wrote:
> In article <fhnq6g0...@news3.newsguy,com >, fid <fidelio...@yahoo,com >
> wrote:
>
> > Thank you for your replies and suggestions. Finally I start to
> > understand something...
>
> <snip>
>
> > Obviously I have standing waves bigger than I can handle. If I
> > increase the sub level even at the lowest crossover setting it will
> > increase proportionally also those peaks.
>
> > I understand that moving the speakers around would change things, but
> > my living room is cluttered, that's why I need to learn alternatives,
> > if there are any.
>
> The bass energy in a room is much harder to tame than treble, and
> increasing it by using sub-woofers makes room dynamics more critical.
> IMO the best way to tame resonant frequencies (either reinforcements or
> cancellations) is by shifting speakers and furniture. Standing waves
> depend on the shape and size of the room as well as the use of large
> furniture to break them up or absorb bass.
>
> Sound in general does not respond well to speakers in corners, this
> gives great reinforcement to bass frequencies. I prefer to block the
> corners with chairs, book cases, etc.
>
> As sound leaves a speaker, it spreads out depending on the frequency.
> High treble beams almost straight out in a narrow path, often only 10 or
> 15 degrees wide. Lower bass goes around corners easily and will leave
> the vicinity of the speaker in almost 360 degrees.
>
> So putting your speakers in the corner reinforces the bass up to 4 times
> with reinforced frequencies dependent on the distance to the side and
> rear walls (as well as to the floor and ceiling). There used to be a
> good computer program (BestPlace) that calculated all these
> reinforcements.
>
> Taming the bass, and the reflections of all frequencies from flat hard
> surfaces, does mean rearranging, but changing room acoustics does make
> for dramatic differences.
>
> Have fun.
>
> Greg

Greg:

All good stuff.

Fid:

There is one quick-and-dirty expedient you can try to help focus on
the direct causes of your problem without ripping your room apart.

Obtain a square piece of 3/4" (20mm) plywood or MDF with its main
dimension about 1.25 x the diameter of the main speaker woofers. Line
both sides of it with either a deep-pile carpet or a dense foam
rubber. Make it on a stand so that you can put it somewhere and it
will stand vertically without additional support.

Place it at several points adjacent to your SW or main-speaker woofers
or between them and see how/if anything changes. It is just a baffle
to break up the sound waves and give you an idea of what is going on.

Best of luck with it. You may have to defer to the Decorator Entity in
your household and beg for a Dispensation to get things moved about.
Been there, done that. A pair of AR9 speakers went by the wayside as
they simply *did not fit* into the room in such a way as to be
tolerable for listening. The pair of 3as fit nicely but are of a very
different nature.

Peter Wieck
Wyncote, PA