Subwoofer preout/cord

[bryan90s]

hi, something confusing me.

ok my HU have a mono subwoofer cord or u may call it a sub preout. i wan to connect it to my amp but my installer doesnt recommend it.

they say by doing it this way, the sub will sound 'soft'.he insist on to tap from the rear preout to my sub.rather than use the sub preout.

i wonder i can believe them o not as i believe the sub preout is there for a reason

 

[Zenn]

try both la and judge for yourself, then only u will know for sure....

 

[cacin]

Hi,
Firstly, what HU are you using?
I know pioneer had some model that support direct sub drive. I am not sure how you connect that though.
Regarding your question, are you saying it's a cable or a rca jack? From what I know, you can connect the RCA Sub preout jack to the amp. This lets you HU use it's built in LPF to send low frequency to your sub amp. If you want, you can still use the built in LPF on the amp too.
The reason for having sub preout on the HU is like having an electronic x-over. So that only the low frequency signals are sent to your amp. So, they have more headroom before the signals get distorted.
A LPF or HPF on the HU minimizes the number of 'things' that you need to have on your system.
Example, Stock HU --> x-over --> amps --> speakers/subs.
HU with built in LPF/HPF --> amps --> speakers/subs.

of course, for some audiophile, the built in H/LPF is not sufficient, that's why you can see this people use the 30 band x-over and stuff like that.

Hope this helps.

 

[howiechoo]

if entry level(of maybe all) hu with sub preout, the preout freq cant be adjust to wat actually u wan..example,
a hu only can adjust sub at 3 mode : 50hz, 80hz and 120 hz...
if ur sub is best at 65hz, then maybe u will had a more punchy sub (80hz) or a softer sub(50hz)..for me, built in xover is useless...i still prefer using another
e-xover to set it to the optimum i like....

 

[k2000]

yes, its true, mine also using preout instead of the sub preout

 

[kyheng]

Using the pre-outs from HU got its advantages and disadvantages. The good is you no need the pre-amp or e-crossovers(save some money and reducing potential airplane create by these 2). The disadvantages is you cannot control the sub frequency hz by hz. But bear with mind, the amp still can adjust the sub frequency. If you want the sub to be harder you can add a coil to it that act as a low pass filter. Just for info, cheap pre-amp and e-crossovers always will generate airplane sound.

 

[DJThoRmented]

Aik? I use the sub preout and set my XO on the HU... OK only. Actually acted better than previous. I believe in new HUs actually but when according to their specs (can save more money for more juniors he he he )

Now with long holidays, think want to try to test the sub amp with another and see the characteristic of it

Oh ya, I've got a friend who used the sub output of his HU and won 1st place

Depending on your HU from my point of view.

 

[cacin]

Not just the HU. Everything in your system comes to play. If you choose the correct HU, the sorrect amp, the correct speaker, the correct sub and the correct box, everything will seems perfect. :P

 

[calvinhpk]

Using the pre-outs from HU got its advantages and disadvantages. The good is you no need the pre-amp or e-crossovers(save some money and reducing potential airplane create by these 2). The disadvantages is you cannot control the sub frequency hz by hz. But bear with mind, the amp still can adjust the sub frequency. If you want the sub to be harder you can add a coil to it that act as a low pass filter. Just for info, cheap pre-amp and e-crossovers always will generate airplane sound.

i wonder why u use coil as low pass filter will give u harder bass??
it's juz a filter.... that's all...it didn't boost any signal

 

[wyx]

in my opinion, if your HU sub preout Xover set to 80Hz, then all freq above will channel to main L/R preout, left 80Hz and below to sub preout.
As your installer claimed that rear preout give 'stronger' bass, I wud say that the 'stronger' bass is actually frm the more punchy bass at freq range of 80-120Hz, which u will miss if using HU with Xover setting at 80Hz.
To me, flat freq response throughout 20~20kHz is more important than boosting on certain freq range. Anyway, it's all abt personal listening taste :)

 

[cacin]

I had read from Car Audio and Electronics that the actual flow sould be,
Which frequency you want to have (for sub), then design a box that will give you the frequency response that you want. Then select the sub that will perform in that box design. Which is normally the flow people will use :P

 

[Zenn]

usually HU will have the sub RCA out with the highest voltage, compared to the front & rear outs. of coz the higher end ones will have all of them pretty high voltage lah. just that normally the sub ones are higher, thats why it shouldnt be a problem using that to connect to your sub amp.

however.....there are some HUs that if u try to connect the rear out to the sub amp, they can sound stronger, so thats why i encourage u to try both, just in case your HU falls into this funny category.

 

[wyx]

normally, we will choose the driver unit (woofer) that has excellent freq test result or sound character that suits our listening taste (most natural sounding), then based on the recommendation frm manufacturer/designer of the driver unit, we build the enclosure according to their spec. Some driver units are meant for front/rear ported enclosure design, some for bass reflex type enclosure, some for horn loaded type, etc. Besides the design, the material use for the enclosure plays a very important part as well.

 

[wyx]

I thought all preout shld b at 2Vp-p? I thought the rear preout sounds stronger is bcoz the rear/front channels cover full freq range (~80-20kHz without LPF)? And if connected these rear/front preout to sub, the sub will sounds 'stronger'or punchier or louder? The preout typical Vout spec shld b listed in amp user's manual. Anyway, can try both to find the one suits your preference.

 

[Izso]

Erm.. not all HU's are equal. Eclipse has one model 8v preout.

 

[kyheng]

i wonder why u use coil as low pass filter will give u harder bass??
it's juz a filter.... that's all...it didn't boost any signal

Well, you can try to use a 2 channel amp to power the sub without pre-amp or e-crossover. You can feel the bass abit softerand the sub moves very fast, sometimes until the voice coil disallocated. Then you try adding a coil to the sub, you can feel the bass is harder a bit and the sub movement slower.

 

[Zenn]

why never use the LP on the amp...?? like that running full range of coz la rosak...

if the amp doesnt have any filters then u definitely need an electronic crossover, unless your HU has one built in.

only last resort if no filters at all in either HU, XO, amp, then only get a inductor coil to do the LP filtering for u. but u only need one filter, not use all together at same time. so its either HU or XO or amp or coil....

 

[kyheng]

Nolah, I forgot to mention it. The amp and HU already set to LPF, but still got some voice comes out, after add the coil the voice no more already.. If use an e-crossover just for the sub's amp, is a waste as my HU has 3 pre-outs. If a 2 channel or 4 channel amp really can used for driving sub, then we no need to buy monoblock amp already.

 

[cacin]

What's the slope of the LPF of your HU? I heard that for best performance, 18db/octave or higher must be used for subs.

 

[Zenn]

maybe LPF set too high thats why still got voices....