Passive sub help!

[Loxxa]

I recently got a passive sub for my 2-channel system. I am using a pair of Boston Acoustics CR6's, which handle bass well enough on their own (IMO), I just want the extra kick from the 12" passive subwoofer. Also, since I live in an upstairs apartment, I need the freedom of being able to switch the sub off.

I've come up with a solution that I assume will work, my reciever has outlets for a second set of speakers, I was thinking of setting the sub as a mono speaker in the 3rd & 4th speaker outputs. I just need a diagram or something for doing this, since I can't remember how to wire stereo to mono. Also, I don't know if this theory will work as well as I assume.

Please help!

 

[markw]

Just make sure that when you buy the sub it has two sets of speaker level inputs. If you try to hook up two amp channels to one set of inputs you're courting disaster.

 

[j_garcia]

You have the ability to switch any sub off...

With speaker level, you would be best served using a summing network to do the conversion. There isn't a way to sum to mono directly from the speaker level outputs - you would be briging, and usually amps won't let you do that on the B terminals if you have something connected to A, if at all.

To add to what Mark said, you can buy a separate amp for the sub, send it a stereo signal and then feed out a mono signal to the sub.

 

[mtrycrafts]

I recently got a passive sub for my 2-channel system. I am using a pair of Boston Acoustics CR6's, which handle bass well enough on their own (IMO), I just want the extra kick from the 12" passive subwoofer. Also, since I live in an upstairs apartment, I need the freedom of being able to switch the sub off.

I've come up with a solution that I assume will work, my reciever has outlets for a second set of speakers, I was thinking of setting the sub as a mono speaker in the 3rd & 4th speaker outputs. I just need a diagram or something for doing this, since I can't remember how to wire stereo to mono. Also, I don't know if this theory will work as well as I assume.

Please help!

You have a passive sub. Is there anything in that that can limit the frequency band it sends to the voice coil such as a crossover? I seriously doubt this is the case.

Your plan will not work well at all. Firstly, you will be sending the full bandwidth, 20-20kHz to it, unless there is more to your system than what you have written.

Then, from the little info, it is not a good idea at all to strap one speaker across two channels of the outputs.

Then, this sub will be in parallel with the other speakers and then some so your amp load will not be good.

Your passive sub needs its own amp, period. That amp needs a crossed over signal.

 

[Loxxa]

it's all a bit confusing to me really

if anyone was curious of the sub, it's an Optimus Pro SW-14 ground firing 12"

for those curious, my setup consists of H/K 460i stereo receiver, Pioneer EQ, Kenwood 5 disc with dual D/A converters & BA CR6's. This is my bedroom stereo in a SMALL room, nothing amazing, obviously but I am on a budget.

buying an amp for the sub and converting it to a powered is out of the question as I am still waiting to upgrade my CD player and my EQ. The sub was simply an impulse buy and I'm not entirely sure if I need it.

 

[MDS]

I've come up with a solution that I assume will work, my reciever has outlets for a second set of speakers, I was thinking of setting the sub as a mono speaker in the 3rd & 4th speaker outputs.

In order to use the B terminals of the receiver with the sub, the sub would need to have speaker level inputs and there would be two of them so no 'wiring as mono' is necessary. The sub will sum the two inputs to mono. You'd then need to select A+B on the receiver.

However as mtrycrafts pointed out, doing so will increase the load on the receiver (because the sub is now wired in parallel with the front speakers) and that is generally not a good thing.

If the sub also has speaker level outputs, then you would wire the normal A terminals of the receiver to the sub and use the sub's speaker level outputs to connect the front speakers. But again that would only be doable if the sub also has a xover control on the back so you could separate out which frequencies go to the sub and which go the front speakers.

 

[markw]

Kid, do yourself a favor.

First. make sure you've got Adobe Acrobat reader on your computer. If not, it's a free download. Get it.

Now, go to this site, which. amazingly enough, will provide you with the free owner's manual for that very same sub.

http://support.radioshack.com/support_audio/doc63/63336.pdf

You'll see that there are two sets of inputs on that sub, one for the right channel and one for the left channel. So, what's this stuff about connecting two amplifier channels together? Didn't you even bother to look at the back of the sub before posting here, even after it was strongly sugested you do so?

Sorry if I sound a little terse, but this is exactly what I told you to look for in my first response to you. Nothing like responding to a question only to have it ignored.

 

[Loxxa]

In order to use the B terminals of the receiver with the sub, the sub would need to have speaker level inputs and there would be two of them so no 'wiring as mono' is necessary. The sub will sum the two inputs to mono. You'd then need to select A+B on the receiver.

However as mtrycrafts pointed out, doing so will increase the load on the receiver (because the sub is now wired in parallel with the front speakers) and that is generally not a good thing.

If the sub also has speaker level outputs, then you would wire the normal A terminals of the receiver to the sub and use the sub's speaker level outputs to connect the front speakers. But again that would only be doable if the sub also has a xover control on the back so you could separate out which frequencies go to the sub and which go the front speakers.

I completely forgot, yes the sub has dual voice coils, 2 level inputs and 2 outputs so I can connect to BOTH channels to the sub and output from the sub to the speakers.

These are the sub specs:

Frequency Range: 29-200 HZ

Power Capacity: 100 watts RMS

Maximum Power: 200 watts

Impedance: Nominal 8-ohms

Speaker: 12", Dual Voice Coil

Crossover Frenquency: 200 Hz w/built-in crossover (low-pass crossover for internal speaker; high-pass crossover for external primary speaker systems)

My receiver outputs 40W. I have the ability to run 2 sets of speakers, forgetting about wiring to mono, would it really effect the power and sound of my system if i wired the sub up through the second speaker outlets? and would it matter that the sub wasn't outputting a signal to normal speakers?

 

[Loxxa]

First. make sure you've got Adobe Acrobat reader on your computer. If not, it's a free download. Get it.

Now, go to this site, which. amazingly enough, will provide you with the free owner's manual for that very same sub.

http://support.radioshack.com/support_audio/doc63/63336.pdf

You'll see that there are two sets of inputs on that sub, one for the right channel and one for the left channel. So, what's this stuff about connecting two amplifier channels together? Didn't you even bother to look at the back of the sub before posting here, even after it was strongly sugested you do so?

Sorry if I sound a little terse, but this is exactly what I told you to look for in my first response to you. Nothing like responding to a question only to have it ignored.

Sorry, i didn't ignore your post and I actually forgot that it does have 2 sets of inputs. Sorry about the mono business, that would have been an entirely different issue. I'm thankfull for all of the replies, and I will be going over the pdf manual after this post.

 

[MDS]

My receiver outputs 40W. I have the ability to run 2 sets of speakers, forgetting about wiring to mono, would it really effect the power and sound of my system if i wired the sub up through the second speaker outlets? and would it matter that the sub wasn't outputting a signal to normal speakers?

If you do the A+B wiring, the impedance seen by the amp will be halved and will be harder to drive. The specs said the sub is 8 ohms nominal and it is likely that the front speakers are also 8 ohms nominal. A+B will put the sub and front speakers in parallel, making the load 4 ohms. The receiver may or may not be able to drive a 4 ohm load reliably. If it can't then it will shutdown.

If you use the speaker level inputs and outputs of the sub, the sub will get a powered signal from the receiver and the low pass filter will keep the frequencies below whatever xover you set for the sub and the high pass filter will send the rest to the front speakers. If you are going to use a passive sub, that is the best way to connect it.

With the A+B wiring on the receiver, the sub and speakers will see the same powered full frequency range signal so there will be no difference in sound, but the increased load on the receiver may cause it to shutdown. I wouldn't do the A+B wiring if I were you.

 

[Loxxa]

If you do the A+B wiring, the impedance seen by the amp will be halved and will be harder to drive. The specs said the sub is 8 ohms nominal and it is likely that the front speakers are also 8 ohms nominal. A+B will put the sub and front speakers in parallel, making the load 4 ohms. The receiver may or may not be able to drive a 4 ohm load reliably. If it can't then it will shutdown.

If you use the speaker level inputs and outputs of the sub, the sub will get a powered signal from the receiver and the low pass filter will keep the frequencies below whatever xover you set for the sub and the high pass filter will send the rest to the front speakers. If you are going to use a passive sub, that is the best way to connect it.

With the A+B wiring on the receiver, the sub and speakers will see the same powered full frequency range signal so there will be no difference in sound, but the increased load on the receiver may cause it to shutdown. I wouldn't do the A+B wiring if I were you.

Thank you for the info, I will output from the sub to the speakers as recommended then.

 

[j_garcia]

If you use the speaker level inputs and outputs of the sub, the sub will get a powered signal from the receiver and the low pass filter will keep the frequencies below whatever xover you set for the sub and the high pass filter will send the rest to the front speakers. If you are going to use a passive sub, that is the best way to connect it.

With the A+B wiring on the receiver, the sub and speakers will see the same powered full frequency range signal so there will be no difference in sound, but the increased load on the receiver may cause it to shutdown. I wouldn't do the A+B wiring if I were you.

Since this is a passive sub, the receiver is still powering it and it "sees" the same total load, though hopefully not at a combined 4 Ohm load.

The bad news is, I just read the manual and it says the fixed high pass from the speaker level outputs is a whopping 200Hz!! IMO, this is not going to work well.

 

[markw]

The bad news is, I just read the manual and it says the fixed high pass from the speaker level outputs is a whopping 200Hz!! IMO, this is not going to work well.

Hey, waddaya want? Didja see the type speakers it's made to mate with? Basically mini-speakers. I have some of those Pro-7 AV's (basically the linear descendant of the Minimus 7, but lacking something) and for their size they do well.

 

[j_garcia]

Yeah, I checked them out briefly, but since the sub is only spec'ed to be good to 150Hz, won't that create a wonderful little GAP? Even those speakers should be good to well below 200Hz. They do have a 5 1/4 midrange, so I'd expect at least decent extension to 60-70Hz (didn't find specs).

 

[mtrycrafts]

Since this is a passive sub, the receiver is still powering it and it "sees" the same total load, though hopefully not at a combined 4 Ohm load.

The bad news is, I just read the manual and it says the fixed high pass from the speaker level outputs is a whopping 200Hz!! IMO, this is not going to work well.

Since that 200Hz will cover some of his other speakers frequencies, it will be parallel with that and the consequences, with a 40 watt amp.

 

[tubesaregood]

I'm sure the sub has satellite outputs - use them.

 

[Loxxa]

I tested the sub today... my first reactions were that my speakers didn't sound the same... the longer i tested it, the less i noticed it, but there was a noticable change, once or twice certain sounds sounded fuzzy, and i noticed occasional pops and crackles. that could always be the connections... but something is off enough for me to notice. I'm paranoid about ruining my speakers... should I just disconnect the sub?

 

[markw]

"pops and crackles"?

That's not a sub issue. Did you drop any cereal in it? You won't ruin your speakers but if you don't like, take it out.

You ARE running your mains from the sub's outputs as instructed, aren't you?

 

[Loxxa]

yes, i might take the sub off... i can't wait to upgrade parts of my system.

 

[Loxxa]

What a deal I must've got on this sub... It cost me $20, of course I knew it was a steal at that price. But here's the same exact sub sold on ebay for over $100 + postage!

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=013&sspagename=STRK:MEWA:IT&viewitem=&item=230096741385&rd=1&rd=1

Maybe I should consider selling mine!