Active vs Passive subwoofers

[Imrahn]

First of all, am absolutely a noob at active vs passive subs apart form knowing what they mean.

Yesterday, i was speaking with a dealer regarding AVRs and speakers for auditioning purpose and he mentioned that nowadays,no HT customer is concerned about tonality,crispness etc of the speakers,all that is needed is an awesome display and the boomiest sub they can get.I am not getting into the rights and wrongs of his observation,but have another problem here.I mentioned him about passive subwoofers(i had one DIY for purchase in mind) and he was like condemning them to death.He was clinging to one point all the time -"Its a waste of ur time and money".He said that an 8inch active would maul any 12+ inch passive anyday,anytime.

Can anyone plz shed some insight on this discussion regarding active vs passive subs?

Thanx and regards

Imrahn

 

[shankarcams]

You are likely to receive opinions both for and against. My personal view is for active subs for the main reason that the amp inside the active sub is precisely matched to the driver and enclosure, thus giving you better load matching and damping. In fact I have a general view that active speakers have the potential to sound better than passive speakers.

This is of course dependent on good design; i.e the manufacturer must build the amp specifically for the driver and enclosure load. Good brands would normally do this.

From a practical perspective, an active sub will reduce one separate channel of amplification for you.

 

[Deepchand]

Here is an interesting read

The ACI Subwoofer Primer...a must read for those considering a sub

 

[venkatcr]

From a practical perspective, an active sub will reduce one separate channel of amplification for you.

I am not too sure about this, but I doubt if you can connect a passive sub to our regular AVRs. You have to connect a mono amplifier in the chain.

Cheers

 

[GeorgeO]

Shankar:

My take is that the sub is the .1 in the 5.1 or 7.1 system- so the AVR will have only the 5 or 7 powered channels it wont have a separate channel for the .1 of the sub. Accordingly I dont see how it reduces on channel.

 

[shankarcams]

Shankar:

My take is that the sub is the .1 in the 5.1 or 7.1 system- so the AVR will have only the 5 or 7 powered channels it wont have a separate channel for the .1 of the sub. Accordingly I dont see how it reduces on channel.

That was my point too - that most multichannel power amps today provide the 5/7 main channels of amplification, and assume that the sub is powered so a separate power amp will not be required. Likewise 5.1/7.1 AVRs normally give speaker level outputs for the 5/7 and line level for the 0.1 channel. My point thus was that a powered sub eliminates the need for one power amplification channel.

If I understand VenkatCR correctly that is what he is saying. Maybe you are also saying the same thing!

 

[abhi_jollyguy]

I will vouch for active sub anyday

 

[GeorgeO]

Yes. I suppose so-the point is that the decoding of the audio in an AVR sends the 5 or 7 discrete signals to the built in amps-Main L-R, Centre etc, and the .1 is only a line level signal, so the question of one less channel doesnt arise at all-you HAVE to have an amp for the .1

 

[spirovious]

Passive obviously need a seperate amp & powered SW can be connected to stereo device to simultaniously.
In passive,if AVR doesnt have amp,then you need a seperate amp which will be outside of SUB taking extra space & connection.

 

[shankarcams]

Yes. I suppose so-the point is that the decoding of the audio in an AVR sends the 5 or 7 discrete signals to the built in amps-Main L-R, Centre etc, and the .1 is only a line level signal, so the question of one less channel doesnt arise at all-you HAVE to have an amp for the .1

Yes, but that amp is built into an active sub, whereas with a passive sub one has to go out and buy an amp. That's all I was trying to say.

 

[shrayv]

Sorry, noob here. So even if one has a 150w amp and a 300w active sub, will the sub's output be limited to 150w?

 

[venkatcr]

Sorry, noob here. So even if one has a 150w amp and a 300w active sub, will the sub's output be limited to 150w?

You have to first understand how the signal is sent to the sub.

In systems such as Bose, for example, all the amplification and crossover is done inside the sub. So what you send to the sub is pre-out signal from an amp, or directly from a source.

If you are using an amp for amplification, you cannot send the amplified output to the sub, unless it is a passive sub. If you are using an active sub, the amp should send out a pre-out signal. When you do this, the amp just passes the low frequency signals (at the pre-out level) to the sub, and does not use it's own amplifier for those frequencies. In an AVR this is called the Point 1 (.1) or LFE channel.

An active sub can only accept pre-out signals and there is no question of external amplification.

Cheers

 

[shrayv]

Sorry, noob here. So even if one has a 150w amp and a 300w active sub, will the sub's output be limited to 150w?

Apologies. What i mean to ask was, if one has a AVR with a rating on 150w per channel, will the sub's output be limited to 150w?

@venkatcr

Thank you for you explanation sir. So is it safe to say that, the sub output is irrespective of the AVR's per channel rating since its an active sub

Thank you for ur explanation once again

 

[venkatcr]

Thank you for you explanation sir. So is it safe to say that, the sub output is irrespective of the AVR's per channel rating since its an active sub

As I said, an active sub only accepts pre-out signals. The only relevant amplification is what is inside the aub. The AVR's amplifier is not used at all, so it's specifications are irrelevant.

Cheers

 

[GeorgeO]

To my mind this discussion is just going in circles.

 

[Imrahn]

So, am i right in concluding that passive subs should be integrated only upon audition with the speakers that they are to be used with?

 

[venkatcr]

So, am i right in concluding that passive subs should be integrated only upon audition with the speakers that they are to be used with?

Imrahn, as George said, we seem to be going around in circles. What exactly is your objective?

Subs are one part of the HT chain, that need not necessarily blend with the rest of the speaker system.

Cheers

 

[Imrahn]

Hi venkat, i had mentioned the reason in the OP itself....i have a DIY Horn sub in mind for purchase, but seems the entire process of getting it properly amplified and integrated to my system is significantly cumbersome and best left to a hardcore or rather 'someone-who-knows-the-stuff'.Its nowhere near as easy as working with an active sub it seems in my case,even if the output might be well worth the effort.

 

[venkatcr]

DIY subs are difficult to make. You are playing with large drivers, specialized crossovers, and the need for excellent sealing of the cabinet to ensure tightness of sound. Not my cup of tea at least.

Cheers