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Shopping for Subwoofers? Stop! Know what is One Frequency Wonder.

Audiolab 6000A Amplifier

Ravindra Desai

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Feb 13, 2018
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Kolhapur, Maharashtra. India.
Hello,

Most people on this forum buy components from the market and put it together to make a system.
Below is a guideline to follow when you are in the market looking for a subwoofer. It applies for all the categories: Stereo, Surround, PA, Branded, Unbranded etc.

For good bass reproduction, it is very important that the cabinet volume is correctly calculated.
The enclosure type can be sealed, ported, Transmission Line, Open Baffle, Bandpass etc.

If, for any enclosure type, the enclosure volume is less than the calculated volume, then the speaker response will peak at a certain frequency making the subwoofer loud in a very narrow band of frequencies.

In the spur of the moment, we tend to like a compact enclosure, loud bass and fall prey to it.
When we get home and listen to a variety of music, we find that the bass is missing, booming and what not.
More often that not, the tonal quality of bass is monotonous and causes fatigue, quickly.

One area where you find such one frequency wonders is cars.
Smooth bass...but it tends to sound the same.

If its there in the recording, you should hear it. But if its not in the recording and still you get enhanced bass, chances are that your subwoofer is a one frequency wonder.
In case you suspect something is not right, resort to listening on headphones for comparing.

Keep this in mind. Listen to different types of music and take your time before selecting one.
Remember, compact and cheap is often a no no.
Do this irrespective of how reputed the brand is.

I hope that this will help you make a good purchase.

Regards,

Ravindra.
 
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VSTEREO

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This is a great article. Subwoofer purchase is such a hectic and integrating with Stereo is another nightmare. Have been trying with my sub for 8 months to integrate with stereo but still there are lot of scope for improvement.
 

Ravindra Desai

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Messages
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Kolhapur, Maharashtra. India.
This is a great article. Subwoofer purchase is such a hectic and integrating with Stereo is another nightmare. Have been trying with my sub for 8 months to integrate with stereo but still there are lot of scope for improvement.

I believe that if the subwoofer is active, then, it should be the active unit which should also have L-Satellite and R-Satellite out.
That way, it is the subwoofer manufacturer who gets to tune and set the crossover and the satellites receive just the right band of frequencies.
All you have to do then is set the gain (volume) of the satellite w.r.t. the subwoofer and you are done. There after you only have to adjust the master volume.
The big difference that I made in this approach is that I did not allow the end user set the crossover frequency, which really is the job of the subwoofer designer.

Then, integration would be relatively easy. I hope that you agree.

Regards,

Ravindra.
 

subsatya

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Could you please tell us if Y cable is better than single cable for subwoofer? Right now I have connected a single cable from avr to R terminal of the sub. My sub has two inputs. Paradigm Cinema 8 Sub.
Will it make a difference?
Thanks!
 

Kannan

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I believe that if the subwoofer is active, then, it should be the active unit which should also have L-Satellite and R-Satellite out.
That way, it is the subwoofer manufacturer who gets to tune and set the crossover and the satellites receive just the right band of frequencies.
All you have to do then is set the gain (volume) of the satellite w.r.t. the subwoofer and you are done. There after you only have to adjust the master volume.
The big difference that I made in this approach is that I did not allow the end user set the crossover frequency, which really is the job of the subwoofer designer.

Then, integration would be relatively easy. I hope that you agree.

Regards,

Ravindra.
Sir,
Active subwoofers should have phono input and output with adjustable crossover level and an attenuator.
This is the best approach to ntegration with the main speakers.
It allows flexibility of choosing the crossover point and attenuation based on the capability of the main speakers and room response.
Having a pre configured xo in the sub will not work optimally.
 

Kannan

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Could you please tell us if Y cable is better than single cable for subwoofer? Right now I have connected a single cable from avr to R terminal of the sub. My sub has two inputs. Paradigm Cinema 8 Sub.
Will it make a difference?
Thanks!
If using a single output from source, some sub manufacturers will mention which of the two inputs to use.
If not it means the two RCA input in the sub is shorted internally.
The safest bet is to use a splitter (Y cable) and plug individually to both inputs
 

Ravindra Desai

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Feb 13, 2018
Messages
327
Points
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Location
Kolhapur, Maharashtra. India.
Could you please tell us if Y cable is better than single cable for subwoofer? Right now I have connected a single cable from avr to R terminal of the sub. My sub has two inputs. Paradigm Cinema 8 Sub.
Will it make a difference?
Thanks!

Subwoofer signals are recorded in phase and with same amplitude in both left and right channels. In other words, subwoofer signal is mono. So theortically, you can connect either L or R signal to the subwoofer and not miss any bass content. If you connect both L and R, then the two will be added inside the subwoofer and you will have 2X (6db) gain.
So volume wise, there will be a change. However content wise there should be no change, if you use a Y cable v/s a single cable
I hope this clarifies things.

Sir,
Active subwoofers should have phono input and output with adjustable crossover level and an attenuator.
This is the best approach to ntegration with the main speakers.
It allows flexibility of choosing the crossover point and attenuation based on the capability of the main speakers and room response.
Having a pre configured xo in the sub will not work optimally.

I look at it differently:
1. The subwoofer can still have a crossover but it will be optimal if the same crossover also outputs signals for main speakers
2. If you are adding a subwoofer, then why not use it optimally and offload the main speakers?
3. What are the chances of integration going wrong if a layman uses an active subwoofer tuned by the company and which has L and R out?

Remember, should the sub have L and R out, it will be crossed such that Main speakers + subwoofer electrically produce a flat response at any crossover frequency. This, to me is a single largest plus point.
Personally, I would rather have my sub and my main speakers NOT producing the same frequency band together. This is ensured in the approach that I have outlined.

Regards,

Ravindra.
 

Kannan

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Location
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Subwoofer signals are recorded in phase and with same amplitude in both left and right channels. In other words, subwoofer signal is mono. So theortically, you can connect either L or R signal to the subwoofer and not miss any bass content. If you connect both L and R, then the two will be added inside the subwoofer and you will have 2X (6db) gain.
So volume wise, there will be a change. However content wise there should be no change, if you use a Y cable v/s a single cable
I hope this clarifies things.



I look at it differently:
1. The subwoofer can still have a crossover but it will be optimal if the same crossover also outputs signals for main speakers
2. If you are adding a subwoofer, then why not use it optimally and offload the main speakers?
3. What are the chances of integration going wrong if a layman uses an active subwoofer tuned by the company and which has L and R out?

Remember, should the sub have L and R out, it will be crossed such that Main speakers + subwoofer electrically produce a flat response at any crossover frequency. This, to me is a single largest plus point.
Personally, I would rather have my sub and my main speakers NOT producing the same frequency band together. This is ensured in the approach that I have outlined.

Regards,

Ravindra.

Essentially we are saying the same thing.

I use the Wharfedale SW150 which takes in both low level (phono) as well as high level (speaker) inputs.
It has crossover adjustment varying from 40 hz to 150 hz, phase inversion switch and input gain control.

I have my preamp out connected to the sub phono input and the sub phono output connected to the main amplifier which powers the speakers.

The sub input gets the full preamp signal, filters out the lows depending on the crossover point set in the subwoofer and sends the balance to the main amplifier.

The variable crossover point and the gain control on the subwoofer gives total flexibility to integrate it to the main speakers in terms of both the optimum crossover point and system db level.

When the subwoofer is kept off, the crossover on the sub is disabled and full signal goes to the main amp
 

Kannan

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Messages
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Location
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Subwoofer signals are recorded in phase and with same amplitude in both left and right channels. In other words, subwoofer signal is mono. So theortically, you can connect either L or R signal to the subwoofer and not miss any bass content. If you connect both L and R, then the two will be added inside the subwoofer and you will have 2X (6db) gain.
So volume wise, there will be a change. However content wise there should be no change, if you use a Y cable v/s a single cable
I hope this clarifies things.

Sir some earlier head units in car from Aline, Clarion, Mcintosh, Fujitsu etc came with stereo outputs for sub section with an option in the DSP section to sum it as a mono signal.
In such head units, one need to run a 2 channel male RCA from the sub outputs of the head unit to amp irrespective of if the amp has one or two channels for input. However most car audio mono blocks have dedicated 2-channel inputs.

I really don't know the purpose behind it other than running a sub each for left and right channels. I have seen some competition cars in youtube videos using this feature, but for sub frequencies I don't know how it helps.

I had once seen an adventurous high end car setup where there were two subwoofers, one in the boot and the other fabricated under the dashboard in the center. Both were top of the line subs from JL Audio and the amps were from Soundstream.
 
Last edited:

Ravindra Desai

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Messages
327
Points
93
Location
Kolhapur, Maharashtra. India.
Sir some earlier head units in car from Aline, Clarion, Mcintosh, Fujitsu etc came with stereo outputs for sub section with an option in the DSP section to sum it as a mono signal.
In such head units, one need to run a 2 channel male RCA from the sub outputs of the head unit to amp irrespective of if the amp has one or two channels for input. However most car audio mono blocks have dedicated 2-channel inputs.

I really don't know the purpose behind it other than running a sub each for left and right channels. I have seen some competition cars in youtube videos using this feature, but for sub frequencies I don't know how it helps.

I had once seen an adventurous high end car setup where there were two subwoofers, one in the boot and the other fabricated under the dashboard in the center. Both were top of the line subs from JL Audio and the amps were from Soundstream.

If you have looked at my other thread on externally powered, active crossover, 2-way speaker system, you will realize that with my DSP, I can try all kinds of combinations by only changing the program.
I have done that: stereo subs vs dual mono subs vs single mono sub.
My conclusion is that mono sub is the best both in terms of quality (sound stage/ stereo image) and cost. In fact I was unhappy with stereo subs as I felt that some things were consistently missing. Besides, it needs one extra channel of amplifier and does not improvement to stereo image.
I will, however, go with dual mono, but powered from the same amp channel.
Two more advantages of dual mono subs is that they serve as 'free stands' for your left and right speakers (giving then the tower speaker look) and also help distribute the bass over the width of the listening area.

Regards,

Ravindra.
 

blackscorpio

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I look at it differently:
1. The subwoofer can still have a crossover but it will be optimal if the same crossover also outputs signals for main speakers
Remember, should the sub have L and R out, it will be crossed such that Main speakers + subwoofer electrically produce a flat response at any crossover frequency. This, to me is a single largest plus point.
Personally, I would rather have my sub and my main speakers NOT producing the same frequency band together. This is ensured in the approach that I have outlined.

Regards,

Ravindra.

In case the pre has a sub out and variable cross over selector, no phase control & all, which would be better option:
1. use xo in pre
2. use xo in sub
?

In my case, I have an parasound 2100 pre which has sub out & active sub with line & speaker level inputs and line outputs for speakers. Currently, I am employing sub @ pre.
 

Ravindra Desai

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Messages
327
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Location
Kolhapur, Maharashtra. India.
In case the pre has a sub out and variable cross over selector, no phase control & all, which would be better option:
1. use xo in pre
2. use xo in sub
?

In my case, I have an parasound 2100 pre which has sub out & active sub with line & speaker level inputs and line outputs for speakers. Currently, I am employing sub @ pre.

I would use the crossover from the sub for the following reasons:
(I am assuming that the people who have originally designed the subwoofer and the electronics have done due diligence)

1. They will have included a subsonic filter as needed by the subwoofer
2. They will have included the crossover filters with the right slopes for the subsonic filter, sub- roll off filter and satellite take-off filter
3. They will have included any form of EQ/ wave shaping required based on the MLSSA data for the subwoofer

Your pre will have no clue of these things about the subwoofer.
As a bonus, you can afford to make your pre redundant.

I hope that this helps.

Regards,

Ravindra.
 

blackscorpio

Active Member
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Messages
562
Points
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Location
Hyderabad
I would use the crossover from the sub for the following reasons:
(I am assuming that the people who have originally designed the subwoofer and the electronics have done due diligence)

1. They will have included a subsonic filter as needed by the subwoofer
2. They will have included the crossover filters with the right slopes for the subsonic filter, sub- roll off filter and satellite take-off filter
3. They will have included any form of EQ/ wave shaping required based on the MLSSA data for the subwoofer

Your pre will have no clue of these things about the subwoofer.
As a bonus, you can afford to make your pre redundant.

I hope that this helps.

Regards,

Ravindra.

Thank you. Will need to re arrange my connections I guess.
 

tuff

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Just a query. What if you have 4 ohm speakers and an 8 ohm subwoofer? would it be a risky venture?
 

Ravindra Desai

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Messages
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Location
Kolhapur, Maharashtra. India.
Just a query. What if you have 4 ohm speakers and an 8 ohm subwoofer? would it be a risky venture?

Nope, there is no risk at all!
You will need a crossover that will direct bass to the subwoofer and rest of the 'bass-less' content to the speakers.
The 4/8 ohm discrepancy is taken care of by setting the sat gain w.r.t. the sub or vice versa.

Regards,

Ravindra.
 
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