Thank you paulmasoner.

 

so im still confused based on the amount of people saying either tap in before or after the bose head unit...i have an amp with a LOC already inside so is it safe for me to tap into the preamp wires?

 

On page 2 of this thread some people claim that using the built-in LOC (aka high level inputs) on your amp before the Bose amp can fry the headunit.

I don't have any personal expereince with frying a headunit in that manner, however, I have used a LOC before the Bose amp. Output wasn't very loud. Simply un-soldered it and tapped after the Bose amp. Night and day difference. Some people claim the Bose amp puts a wicked EQ curve on its outputs (which I bet it does), however if you're just installing subwoofers, you really won't notice.

I'd just tap right at your rear speakers.

 

by "just subwoofers" you mean subs with the amp correct? as in not other speakers.
just clarifying. what loc would you prefer or just use an RCA-speaker wire connection

 

Subs and amp, yes.

And you can try just using the high-level inputs. But I'm willing to bet you'd get more output using an adjustable outboard LOC.

 

so did this option ever work? I'm thinking about trying it out so I can tap pre-bose amp. if I'm adding amps I want to strip out the bose amps.

 

did you ever get this to work rotarenvy?

get a sub to run off the prebose wires without an external LOC.

Thanks

 

Just wanted to chime in here since I'll be adding subs soon. I'll be tapping the line into the Bose amp. YES this is better. No argument there. I've read some people saying it's damaging the HU running them into the RCA inputs of an amp. This is likely because the Bose input is a balanced signal like an XLR mic signal. If true, the "negitive" audio signal (of the input of the Bose amp) isn't the same sort of negitive as the chassis ground. It's 180deg out of phase with the positive signal. Grounding this lead (via the shield of the RCA input) is essentially shorting one phase of the HU's balanced signal. IF this is all true, what you guys need is a balanced to unbalanced convertor.

I'm sure they make these devices but I don't know who has them. I'll be making my own.

The cheapest way to make a passive convertor is to add a capacitor to both the positive and negitive leads from the Bose amp inputs. This gives you DC isolation. Depending on the input impedance of your amp, 47~100uf 25~50v non-polar should do it. It's likely you can just use the positive signal and tie the RCA ground at the amp but this could create a ground loop with some amps.

Here's a link to a device that should work with the Bose system.
TX-A2D ‐ Dual Audio Converter ‐ Balanced to Unbalanced

Here's a schematic for an active balanced to unbalanced convertor.

 

WOW what a headache this BOSE set up has been in terms of the best set up!

OK so after reading all this one of my options was adding 2 more amps 1 for sub one for rears, wanted to avoid this so wanting your opinion on this set up.

I was thinking of using this EQ NEW LANZAR VIBE440PSU 1/2 DIN 4 BAND EQUALIZER WITH SD AND USB INPUT - Newegg.com after the bose amp to improve on some of the modified signal especially with regard the rears which I am replacing with some new 3-way Infinity Reference 9613i which i snagged for a fiver off ebay!!

So the idea is to come off the output of the bose amp straight into the EQ which accepts high level inputs, then use the EQ's RCA out for the sub input and patch the front and rear EQ outputs back into the BOSE out loom.

However there is one problem. Someone mentioned somewhere that the front tweaters and 9'' have some sort of capacitance on them to further limit the frequency input.

Given the spec of the above EQ would it be ok to remove the capacitors on both sets of speakers and just use the EQ? If so are the capacitors easy to get to?

 

So what is the end result you're looking for? You can add subwoofers and replace the rear speakers without screwing with the Bose amp. And I don't think I'd amp the rears without amping the fronts (which means replacing them too). Bose power on the rears, or gut the whole system.

 

In the Bose system, the front amplifiers are class-d driving 1/2ohm 9" woofers. The tweeters have crossover caps like any tweeter. 22uf I believe. The door amps don't shape the signal. Shaping is done in the trunk amp. If eliminating the small door amps, it's likely that your aftermarket amps may have an issue with driving the 1/2ohm 9s.

Not sure where your going with this. If you tap the signal coming OUT of the bose, where exactly do you plan on feeding the EQ's output? The EQ will not power speakers obviously. Also, that EQ can not be used before the Bose amp due to the system using balanced lines NOT 2-conductor signal/ground like the EQ. http://en.wikipedia.org/wiki/Balanced_line
Tapping the signal before the amp and using a balanced to unbalanced converter into the sub amp (or an amp with a balanced input) is the only correct way to wire subs into the Bose system. Anyone who argues that point doesn't fully understand how the Bose or balanced signal works.

 

Well the problem is the BOSE shapes the signal to the rears so I would not get the best sound out of the 3 way infinity speakers i have! However I still want to use the BOSE amp to avoid having 3 amps!

Great i'm back to the drawing board. OK thought the EQ could pass through a powered signal, my bad. I guess my question now is how do I get the best 3 way signal into the rear speakers using the BOSE amp and secondly is there any point to grabbing the rear outputs out of the amp through a passive LOC into the sub if as a poster on another thread has indicated some of the lower frequencies into the rear speakers have been shaped??!!

What a nightmare system to work with I must say!

 

All Bose's sound shaping is done in the trunk amp itself. You can tap the balanced signal without spending a fortune on convertors -but- there's a DC voltage present in the balanced signal from the head unit. I'm not sure why. You can not simply splice a pair of RCA cables into it. What you can do is place a non-polarized capacitor in series to remove the DC offset and run straight into your sub amp or another line-level device like the EQ your interested in.

If you need a drawing I can make one for you.

 

That would be a great help. Cos I am a little confused by this all.

If you don't mind would help if you told me the color of the lines to tap into.

My sub amp has a gain control and 180 phase switch on it if that's any help.

And lastly can you explain why you say use a capacitor and not a diode? Also aren't capacitors meant to discharge the build up of current somewhere, if so won't the sub pop occasionally? And finally will splicing into the HU out not reduce the voltage going into the BOSE amp and thus reduce its output?

Thanks

 

Will do.

There's a DC voltage present in the signal coming from the headunit. A capacitor placed in series will remove the DC voltage but allow the AC audio signal to pass. This happens because the capacitor charges up to the DC voltage that's present in the line until the charge is equal to that voltage. Once charged, no more current will flow thus blocking the DC. The AC signal's polarity is constantly changing back and forth and current will pass through the capacitor since it's state of charge can't keep up with the rapidly changing waveform.

That is, IF the value is large enough. Too small of a value and the capacitor may have time to charge and keep up with low frequencies, but not higher ones. That's how a capacitor in series with a tweeter does what it does.

I spliced into my wires before the Bose amp and ran the rear channel set to a sub amp. I didn't notice any reduction in volume of my rear speakers but technically there is an impedance mis-match doing it this way. The ONLY way to correctly tap these signals is an active (powered) balanced to unbalanced convertor shown in post 133.

EDIT - Here's the sticky on the RX8's sound system. https://www.rx8club.com/series-i-int...-first-226065/
Some of the info is wrong and some of the links are broken (write-ups shouldn't uses external links) but it may get you started. I'll get you the pinouts and colors. Hopefully later today.

Here's another pic from another user's post. https://www.rx8club.com/attachments/...ampwiring2-jpg

 

Thanks kickerfox I think I'll take your option. Can you tell me exactly what type of rating capacitor I need, and which wires I solder it too. And am I right in saying I just spice into the HU line rather than break it. ie can i just come connect it to the amp in wiring plug? Also does it matter what way round the capacitor is? Thanks

 

Sorry I don't have the schematics yet. My PC with the schematics popped a monitor and I haven't replaced it yet.

10-22uf non-polarized capacitor. Any voltage from 16v up will work. They're usually used as crossover caps for tweeters and probably 25-50v. That will work fine.

It won't have the high-pass characteristics like it would on a tweeter because your amp's line-in is a much higher impedance.

You will need 2 per channel.

 

Do you know what color is positive and negative on the wires going from the amp to the back speakers on the stock bose system . I think ive got one back words because when adjust my line out converter one side gets loader when I adjust it up and the other side get quieter when I adjust it up. The wires are purple and pink on drivers side and whiteish and black on the other side