Amp wiring & General questions

ganesh · 15 Jan 2013 at 13:24

The amp - HERTZ HE4

If you see my other thread - http://forums.overclockers.co.uk/showthread.php?t=18476540 You'll see that i've bought all new audio equipment.

My issue - The amp has a wide and bewildering array of connections/settings and comes with a terrible manual, which doesn't really help in the slightest.

I'll be wiring in using three channels, two front speakers and a sub as below.

But, for three channels concerning the RCA leads it says this "Apply same L&R signal using RCA Y adaptor" -

Do i just need one set of RCA leads? As the picture shows there are two inputs, labelled A/B. So where do my RCA cables go?

This is the confusing end of the amp -

I've no idea what the A-Level/A X-over or B-Level/B X-over knobs do, any clarification is very much welcomed.

Thanks all.

Howard · 15 Jan 2013 at 13:46

If you use only one set of RCA leads you won't have any control from your head unit over the level of the subwoofer independently of the speakers. Run another feed for the subwoofer's channel.

The level and crossover settings are just for setting the gain and high/low pass crossover point for each pair. Set the A Xover mode to 'full', B input to 'B in', and the B Xover mode to 'Lo pass'. Set the level about mid way on both and set the B Xover Level to 400 and set this, and the speaker and subwoofer output levels using the head unit if possible.

The crossover defines the high or low cut-off frequency for the speakers, i.e. for the subwoofer you don't want to pass it high frequencies, and vice versa for the other speakers seeing as you have a sub.

touch · 15 Jan 2013 at 13:55

You put a left + right feed into the A channel but you feed a mono input onto both connectors (with a y splitter) on the B channel.

Swifty55 · 15 Jan 2013 at 15:40

Does your Head Unit have separate RCA outputs?

ganesh · 15 Jan 2013 at 18:42

Howard said:
If you use only one set of RCA leads you won't have any control from your head unit over the level of the subwoofer independently of the speakers. Run another feed for the subwoofer's channel.

The level and crossover settings are just for setting the gain and high/low pass crossover point for each pair. Set the A Xover mode to 'full', B input to 'B in', and the B Xover mode to 'Lo pass'. Set the level about mid way on both and set the B Xover Level to 400 and set this, and the speaker and subwoofer output levels using the head unit if possible.

The crossover defines the high or low cut-off frequency for the speakers, i.e. for the subwoofer you don't want to pass it high frequencies, and vice versa for the other speakers seeing as you have a sub.

Most informative, thanks, the manual reccommends putting the A Xover to High, but I can play around and see what works.

touch said:
You put a left + right feed into the A channel but you feed a mono input onto both connectors (with a y splitter) on the B channel.

Now I just need to find me a mono cable with such outputs.

Swifty55 said:
Does your Head Unit have separate RCA outputs?

Yep, it has outputs for fronts, rears and subs.

Much appreciated chaps.

mejinks · 15 Jan 2013 at 18:53

Ignore touch, thats incorrect. What head unit have you got? You run two sets of RCAs, from head unit front output to A in and sub to B in. Howards advice is mostly correct other than you need to set the crossover point at about 80hz, not 400.

Swifty55 · 15 Jan 2013 at 19:48

ganesh said:
Most informative, thanks, the manual reccommends putting the A Xover to High, but I can play around and see what works.

Now I just need to find me a mono cable with such outputs.

Yep, it has outputs for fronts, rears and subs.

Much appreciated chaps.

Run 2 sets of RCA cables. 1 from Front Out, and the other from Sub Out.

Front to Channel A and Sub to Channel B. Wire up the speakers to the correct channel outs and set up the channels accordingly.

ganesh · 15 Jan 2013 at 20:11

mejinks said:
Ignore touch, thats incorrect. What head unit have you got? You run two sets of RCAs, from head unit front output to A in and sub to B in. Howards advice is mostly correct other than you need to set the crossover point at about 80hz, not 400.

This makes more sense, both the head unit and amp both have a left and right connector for the sub, so there's no mono connection. Will find myself another RCA cable. My head unit is the Alpine X305s.

ganesh · 16 Jan 2013 at 08:22

One last question, i don't suppose anyone knows if there is a standard bullet connector size on headunits?

The blue remote cable i believe is a female bullet type, but what size male connector i need i have no idea.

iaind · 16 Jan 2013 at 08:41

They dont tend to be standard, but just get yourself a little box of bullet and spade connectors of all different sizes - worth having and not expensive

Howard · 16 Jan 2013 at 09:28

mejinks said:
other than you need to set the crossover point at about 80hz, not 400.

Yeah, 80Hz on the head unit if possible, was what I was getting at

I wrote that post in a bit of a piecemeal fashion yesterday so it probably doesn't make as much sense as it should!

In fact if it is possible to set the sub crossover on the head unit, which I'm sure it is if you've got separate sub outputs, no need to set the crossover on the back of the amp, just leave it at full range.

If it's possible to set the high pass filter / crossover for the speakers on the head unit as well then do this and leave both the A and B inputs set to full range.

ganesh · 16 Jan 2013 at 19:55

Howard said:
Yeah, 80Hz on the head unit if possible, was what I was getting at I wrote that post in a bit of a piecemeal fashion yesterday so it probably doesn't make as much sense as it should!

In fact if it is possible to set the sub crossover on the head unit, which I'm sure it is if you've got separate sub outputs, no need to set the crossover on the back of the amp, just leave it at full range.

If it's possible to set the high pass filter / crossover for the speakers on the head unit as well then do this and leave both the A and B inputs set to full range.

I've been scouring my head unit manual and I have the following options:

Bass Centre Frequency - 60/80/100/200hz
Bass Bandwidth - 1/1.25/1.5/2
Treble Control - 10/12.5/15/17.5khz
High Pass Filter - 80/120/160hz

This is in addition to the standard audio settings -
Subwoofer: 00 ~ 15
Bass level: –7 ~ +7
Treble level: –7 ~ +7
Balance: Left15 ~ Right15
Fader: Rear15 ~ Front15
Loudness : ON/OFF
Defeat : ON/OFF
Volume: – ~0 dB

Will adjusting the high pass filter just affect the speakers? Also will settings on the head unit override those on the amp?

Edit:
From further research I think I'll set the bass to 80hz, leave the bass bandwidth to 1, the treble to 12.5 and the high pass filter to 80.

Thanks for your help everyone.

robnut · 16 Jan 2013 at 20:36

Dont run a filter on both the stereo and the amp, it can cause issues. I use all amp filters and a bass control knob to tweak now and then.

ganesh · 19 Jan 2013 at 20:01

Had a horrible day trying to install all of my new sound system, luckily the previous owner had already run new speaker cable through the door harness which saved me some time. Still lots to finish tomorrow, I was ****ing freezing all day today, probably not the best weekend to do it but I couldn't sit around with all this nice gear and not install it!

Oddly the remote cable on my head unit was already connected to something, but I don't have an amp currently.

Though I do have one problem and would appreciate some advice:
I want my amp (Hertz HE4) to sit underneath the passenger seat and currently the seat scrapes the top of the amp without anyone sitting in it.

Can I just raise the passenger seat with some washers?

If I can't do that then the only other place I could think to put it would be to screw it into the firewall behind the passenger seat, which is a lot less stealthy than I would like.

The car is a MK2 Mr2.

Wonderloaf · 19 Jan 2013 at 20:14

Don't raise your seat with washers, they kind of need to be secure to the floor lol.

Can you modify the amp cover?

ganesh · 19 Jan 2013 at 22:01

Wonderloaf said:
Don't raise your seat with washers, they kind of need to be secure to the floor lol.

Can you modify the amp cover?

Amp can't be modified in any way, if I can't raise the seats with nuts/washers then perhaps I could modify the seat in some way, it's a metal cover underneath the seat that it scrapes on, but I'm guessing that it's quite structurally important.

Is raising the seat 5-10mm really going to affect the security of the fit that much? When I had a bucket seat it had 5mm spacer plates fitted.

Participant · 20 Jan 2013 at 09:34

Other option might be to lift up the carpet and see if you can cut an amp-sized hole in the sound deadening. This might drop the amp enough for the seat to no longer foul it.

Personally I'd far rather have my amp in the boot, for access and serviceability, but then I don't know the mr2 layout very well and this might not be so practical. If you're worried about lack of stealth, could you create a false panel covering the amp from thin mdf and cover it with carpet to match the boot floor?

iaind · 20 Jan 2013 at 09:40

Robbie G said:
Other option might be to lift up the carpet and see if you can cut an amp-sized hole in the sound deadening. This might drop the amp enough for the seat to no longer foul it.

Personally I'd far rather have my amp in the boot, for access and serviceability, but then I don't know the mr2 layout very well and this might not be so practical. If you're worried about lack of stealth, could you create a false panel covering the amp from thin mdf and cover it with carpet to match the boot floor?

Problem with that is the engine is in the middle of the cabin and the boot! Wouldn't be impossible, but running speaker cable through the engine bay doesn't seem like a great idea

I wonder if it could go under the bonnet though...

Alternatively, the bulkhead behind the seats could work, but if its got the T bar roof you wouldn't be able to stow the glass back there

Tom_ed1987 · 20 Jan 2013 at 10:18

Many people put the amp in the frunk, taking care to keep the wiring well away from the power steering pump. It's a bit of a clunky solution though. I mounted mine on top of the rear storage box as like you I found there was no room under the seats. I had to trim some of the heatsink material off the amp to allow it to fit, but it was only there for the bling anyway and the amp remains cool (JBL GTO4000) and after a lick of satin black dosen't look too bad. The t-bar glass can still rest ontop of it too.

Be sure to run the RCA cables down the center of the car to avoid inteference. The main car loom runs down the sills.

The remote cable on the HY is probably connected to the electric aerial activation wire in the factory loom.

You can feed cable from the cabin to the boot via the box section that comprises the rear wings if you wish, completely avoiding the engine bay. Remove the boot carpet and the interior lower quarter panel trim pieces for access.

Unless you have a very low profile amp (<~3cm~) there is no way it will fit under the seats with someone sitting in it.

ganesh · 26 Jan 2013 at 21:28

Tom_ed1987 said:
Many people put the amp in the frunk, taking care to keep the wiring well away from the power steering pump. It's a bit of a clunky solution though. I mounted mine on top of the rear storage box as like you I found there was no room under the seats. I had to trim some of the heatsink material off the amp to allow it to fit, but it was only there for the bling anyway and the amp remains cool (JBL GTO4000) and after a lick of satin black dosen't look too bad. The t-bar glass can still rest ontop of it too.

Be sure to run the RCA cables down the center of the car to avoid inteference. The main car loom runs down the sills.

The remote cable on the HY is probably connected to the electric aerial activation wire in the factory loom.

You can feed cable from the cabin to the boot via the box section that comprises the rear wings if you wish, completely avoiding the engine bay. Remove the boot carpet and the interior lower quarter panel trim pieces for access.

Unless you have a very low profile amp (<~3cm~) there is no way it will fit under the seats with someone sitting in it.

I finally finished the car this morning, and it sounds awesome. Loving the sub behind my seat, with the music up loud on a bassy track i can really feel it in my back.

I had an engineer shop make me up some 20mm diameter, 20mm long spacers so the passenger seat clears the amp.

You're spot on with the electric aerial activation, can I just split the remote cable from the HU?