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-   -   How can I connect my subwoofer?? (http://www.diyaudio.com/forums/subwoofers/68099-how-can-i-connect-my-subwoofer.html)

kayjayw 18th November 2005 12:20 PM

How can I connect my subwoofer??
 
Hi! I wonder if anyone can help me with a small speaker dilemma… I have been given a subwoofer with cab (Adire 12” – don’t know specs as I can’t contact the guy who gave it to me!). I’d like to hook it up to my system (NAD 3020 amp connected to Humble Homemade HiFi Tempo speakers each with Seas H831 tweeter & Vifa PL18WO-09 midwoofer) to increase the bass. The problem is how to connect the subwoofer. My amp only has one set of speaker outputs. Is there a splitter device that can allow the subwoofer to be connected to these – and will there be an impedance conflict or a volume differential? Alternatively, someone suggested connecting the subwoofer via a dedicated amp to the tape out (pricey?). I am obviously no genius when it comes to these matters so any help appreciated!
Regards, Kevin

simon5 18th November 2005 12:37 PM

It's probably a Shiva if you paid a low price for it. It's a dual 8 ohms voicecoil, probably wired in parallel to make a 4 ohms load. I'm quite sure your NAD amplifier wouldn't like a 4 ohms load in parallel of what you already have, but I could be wrong.

You should buy a separate plate subwoofer amplifier. To power a Shiva, I would shop at Rythmik Audio for a 250W (109$) or 350W (149$) amplifier. I used a 250W on the one I built and the owner, besides hitting the protection circuit often (115+ dB measured with a ratshack using a correction sheet), she loves it. I guess if I went with the 350W version, she would burn the poor woofer, she's a heavy user hehe! If yours is in a smaller box, then you could use the 350W version without problems, but it is worth it? You'll gain about 2 dB in output, you decide.

You could also get the audiophile version, you decide if it's worth it also.

Link:
http://www.rythmikaudio.com/nonservo_product.htm

There you can buy it too if you don't want to order directly from them (price is slightly higher):
http://www.acoustic-visions.com/~aco...rs/index.shtml

EDIT: Just saw your were in Greece, I don't know if they ship there or if there's great local alternatives, you might want to look around. Anyway to connect the subwoofer with your NAD, you'll need to build a nice lowpass x-over anyway if you don't go the separate plate amplifier route...

DorinD 18th November 2005 01:20 PM

Why don't use something like this:
http://www.visaton.com/english/bildg..._bweiche1.html
So, for an uniq sub you can make a "mechanicaly" L and R channel sum using both voicecoils and without lowering the impedance seen by your oldy NAD.

richie00boy 18th November 2005 01:38 PM

But that will lower the impedance seen by the amp, not to mention that the passive filter will offer pretty poor performance and no way to match level between the sub and main speakers.

IMO passive subs should not be considered, especially with decent main speakers like what he has.

DorinD 18th November 2005 01:53 PM

Quote:

Originally posted by richie00boy
But that will lower the impedance seen by the amp, not to mention that the passive filter will offer pretty poor performance and no way to match level between the sub and main speakers.
He could use the same sub crossover to cross-high the mains and get them sattelites (by taking signal parallel with the inductors). In this case impedance will never being lowered.
Using a passive sub is a challenge but is worth trying if the mains a not so sensitive. I use such setup with horn mains (sensitivity about 100dB) crossed @80Hz but woofers were 2x4 ohm in an unstuffed strait TL of 2.5 meters.

richie00boy 18th November 2005 06:37 PM

The problem is twofold:

1. Lack of damping at the filter -3dB point, making the bass flabby.

2. The impedance of the main speakers and possibly also the sub will be all over the place through the crossover, so the response will be all over the place.

Try it, but it's certainly not high fidelity.

kayjayw 21st November 2005 07:24 AM

Thanks everyone! I got a bit lost with the technical advice, but what I gleaned was that it seems preferable to buy a separate plate amp. The driver I have must be a Shiva as the cabinet design is a Shiva one. The point is to have an element of HiFi - not just a botched together setup. Simon5 mentioned building a low pass crossover. Where can I get a design drawing of one of those? Where will the subwoofer amp actually connect with my main amp?
Regards

sreten 21st November 2005 08:43 AM

Hi,

get a decent plate amplifier - it will include the low pass crossover.

For a NAD3020 you can connect the Sub to either the speaker outputs,
which will not be additionally loaded, or split the pre-amp out connection
to provide output to the sub and the 3020 power amplifier section.

:) /sreten.

sumacSK 21st November 2005 09:37 AM

Hi sreten,

What do you mean with " split the pre-amp out connection" - just run 2 wires from where should be only one? I'm really interested in thist because I have the same problem.

Thanks Martin

sreten 21st November 2005 11:38 AM

Quote:

Originally posted by sumacSK
Hi sreten,
What do you mean with " split the pre-amp out connection"
- just run 2 wires from where should be only one? I'm really
interested in thist because I have the same problem.
Thanks Martin

Yes, exactly that.
Though I will note that doing this on my Audiolab 8000A turned out
not to be a good idea as the extra loading (presumably the capacitance
of the long stereo sub cable) degraded the treble performance too much.

:) /sreten.


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