Aftermarket HU -> Original Amplifier -> Aftermarket Speakers

[Fnz]

Due to what I perceive as a general 'loudness', along with a lot of static, i think my car audio is being amplified twice. It seems as though the aftermarket head unit in my NB is hooked up to (what I assume is) the original amplifier. The pre-out connections on the HU are not being used, the other block connection (ISO?) is delivering the audio. I believe the car has aftermarket speakers (there are 8-inch JBL GTO836e in the doors).

There is static/noise as soon as the volume is raised above 'zero'. This static seems to stay constant (i.e. does not scale with increases in volume). As things are - with the general 'loudness' of the audio - I often find myself listening to music with the volume set as low as possible and the static is very annoying.

I'm looking to improve the sound quality and get rid of the static. I've read on miata.net that the Bose set-up is unique due to a passive amplifier and (originally) low-impedance speakers. I'm not sure whether this implies that the amp and speakers are only really suitable for use together.

I don't listen to the radio so the static is not due to reception. I listen to audio on disc and on my USB drive.

Would it be a waste of time and money to have someone hook up the aftermarket head unit to the original amplifier, which feeds into aftermarket speakers? Would I be better off doing something else, such as just bypassing the amplifier completely, or buying a new amplifier?

[leamyj]

Trial and error would appear to be one option....see if you can get an acceptable sound by playing around with configurations...word of warning , go easy on volume while doing this for fear of blowing the speakers

John

[mx5ash]

If its a aftermarket hu and speakers then you shouldn't run it through the bose amp. Best thing to do is get a speaker and hu out and see can you connect a new speaker wire directly to each other. See what the sound is like then and if its good/better look at bypassing the amp some how. Loads on miata.net for doing it
http://www.miata.net/garage/bose_bypass.html

[johnc55]

Hi
I have an NB as well and went through a few stages to where I am now.
1st was original radio through the bose amp and original bose speakers with a frequency adaptor for the radio.
2nd Aftermarket (Lidl) HU with the line output (not speaker output) fed through the bose amp and bose speakers.
This worked fine for a while then I got the wet buzzy speaker thing and had to look at replacing the speakers.
Present set up is the Lidl HU with speaker output connected through the original loom but with the bose amp bypassed. i.e. find the amp connector and short the connections so that the original wiring can be used.

Lots of info on miata.net garage.

What I do know is that if you use the Bose amp and speakers you have to use the line output (i.e. unamplified) from the HU. If you replace the speakers, you have to bypass the bose amp. PM me if you want to have a chat about it. Based in Dublin and can meet up if that helps.

John

[Fnz]

Thanks very much for the replies. So, because I have aftermarket speakers and aftermarket HU, the original Bose amplifier is useless?

I probably get someone to bypass the amplifier for me - unless it's an easy job?

[johnc55]

Thanks very much for the replies. So, because I have aftermarket speakers and aftermarket HU, the original Bose amplifier is useless?

I probably get someone to bypass the amplifier for me - unless it's an easy job?

My guess is that if you ask a garage or audio place to do this they really will not know what to do.

I can't find the link at the moment but I have a printout of the Bose amp connector and the correct pins to "short" with small jumper wires (paperclips?). This connector is just about accessible in the passenger side footwell and just about visible when unplugged. Then it is just a matter of putting short jumper leads in to connect the correct wires in this plug. This has the effect of leaving the amp in place but it is not connected anymore and the correct wires to the plug-in connector (now disconnected) are connected directly to feed the speaker inputs from the head-unit directly to the speakers rather than through the amp. Not sure of this reads clearly... ? It's one of those things that is easier to do than to describe...

Its about a 30 minute or less job if one knows where the connector is and which wires to connect.

If you want to have a look at mine or if you want a hand to do it, contact me and I can arrange to meet you.

J

[johnc55]

found the link with diagram and instructions.....

http://miata.fosketts.net/index.php?tit ... _Connector

[Fnz]

Thanks for the information John. Now that I know where the Amplifier is, I'm gonna see if I can get my mitts on it.

[johnc55]

Good stuff. The photo in the link shows the location of the amp as being behind the plastic trim over the side of the footwell. It is actually more towards the back (and below) where the head unit is located in the centre. I think I found it useful to remove the glovebox (clips out) first. Also, I remember that I could not actually see the amp unit but found the connector block by touch (after some interesting gymnastics!).
Disconnecting this block allows it to be gently pulled into view which allows for "Jumping" the connector as described. I found it useful to make up the 4 small jumpers by soldering some small cut-offs from a paper clip to both ends of a 2 inch or so length of wire. These were about the right size to be a snug fit in the socket of the connector. I also made a cover from stiff plastic to gaffa tape over the connector block before pushing it back out of site just to protect the jumpers from being knocked out of place.

Should have taken some pics when I was in there.... Next time!

Best of luck with it - let's know how u get on.

john