HI-Low Converter for Subwoofer / LLT use or General use. - AVS Forum
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post #1 of 11 Old 08-28-2012, 01:21 PM - Thread Starter
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I know there are plenty of hi-low converters out there manufactured for the car-audio industry but I was wondering if anyone could point me in the right direction to a decent one that has been tested by anyone. My concern is that I am using this for a receiver that doesn't have any preamp outputs only speaker level and I want to use an external amplifier for a new LLT DIY Subwoofer project I am working on.

Should I be concerned with frequency response of those devices in the 10-100Hz range?
I couldn't even find any where they published the frequency response online but I was pretty lazy with my searching.

Can anyone recommend one or should I just build something? I rather have something out of the box where I can adjust the level to the output.
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post #2 of 11 Old 08-28-2012, 09:01 PM - Thread Starter
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find plenty of models like these, but what is the frequency response?

http://www.sonicelectronix.com/item_44155_Boss-B65N.html
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post #3 of 11 Old 08-28-2012, 09:26 PM
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I've never seen a schematic for one of those but I imagine it's little more than a voltage divider made with high power resistors. If that's the case then frequency response will be flat at audible frequencies .
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post #4 of 11 Old 08-29-2012, 11:19 AM
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Do a search on "crossover" and you'll find descriptions and models from $10 passive to $10,000 active and everything inbetween. You'll also need an attenuator to convert speaker level to line level for the amp. You can build that into the circuit if you DIY.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #5 of 11 Old 09-09-2012, 07:26 PM - Thread Starter
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I'm going to order on of the cheap high low converters and because I'm curious, open it up and see what the circuit is.

If its not a simple voltage divider circuit then ill just build one.

I'll be placing a low pass filter before the amp so not too concerned about that part yet.

I just need to take my sub out speaker level output and feed it to a more powerful amp for a DIY subwoofer upgrade I'm in the process of planning / building.

unfortunately my receiver doesn't have a low level sub out.

Let you know how it works out once I get it.
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post #6 of 11 Old 09-09-2012, 08:09 PM - Thread Starter
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check out the circuit board of this one. has transformers on it, is that something I should worry about if I'm looking for flat response down to 14Hz?

http://www.amazon.com/Pyramid-NS60-Level-Impedance-Adaptor/dp/B000EFKK5G/ref=cm_cmu_pg__header
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post #7 of 11 Old 09-10-2012, 11:29 AM
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My apologies, I completely misunderstood what you wre asking. I was thinking frequency, not voltage levels. I believe I have seen speaker level to line level adapters at Parts Express and Monoprice but have not looked recently. All you need is a resistive voltage divider plus blocking caps to keep any d.c. out of the sub amp (use on + and - sides to isolate ground in case the receiver has a bridged output stage). You can also get in-line attenuators, but they do not always provide d.c. blocking and I would want that in this case. YMMV.

I did not see frequency specs on Amazon and did not try to track down the manufacturer's specs. Most transformer-based designs do not go below 20 Hz if that so I would double-check before using in a subwoofer application. If you can DIY, resistors and caps should do the trick.

100 W into 8 ohms is 80 Vpp (28.28 Vrms). Your amp probably expects around 1 Vrms so you'd want about 15 dB of attenuation.

HTH - Don

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #8 of 11 Old 09-11-2012, 12:49 PM - Thread Starter
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No problem Dom, thanks for the help. I figure they are generally so cheap that if whatever I order doesn't fit my needs I could replace it. I'm still in the late planning stages of building my sub so I'll update this thread once I order something and test it out.
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post #9 of 11 Old 09-11-2012, 04:39 PM
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Quick comment on DIY -- make sure the caps you use are rated high enough in voltage for speaker levels, and/or put them after the attenuator and make sure it is never plugged in backwords.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #10 of 11 Old 11-23-2012, 07:10 PM - Thread Starter
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Didn't want to leave this open ended so this is my update.

I noticed problems with clipping on my hi-low converter I purchased so I ended up just building a voltage divider with a resister.

I used a 68K ohm resister attached to the cut off end of an RCA cable and now I have zero problems with my setup.

little gain adjustment and I'm good to go.

When I was testing with 16Hz sine waves or deep bass heavy scenes, I noticed the issue and started tracking it down to the high-low converter.

if you want any details on the math or the setup feel free to ask.
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post #11 of 11 Old 11-24-2012, 09:57 PM - Thread Starter
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Pics of the production version of the stereo high low converter I built.

nice to have a flat response down to 1Hz.

it has a 68K Ohm resister on each channel attached to RCA plugs on one end and just cheap speaker wire on the other.




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