Amp crossover settings

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Leddy

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Hi all.

I have recieved a new amp today that i shall be fitting at the weekend. It's an Alpine MRV-F450 and its one big motherf**ker!!!

I'ts power rating at 12v is 30x4wrms + 150wrms. I shall use this to drive my Focal 130's up front, my Pheonix Gold 175's at the rear and my JL AndyMac stealth sub.

My question is, with this setup, what should the crossover settings be? Please see the attached PDF page 12 (MRV-F450 is top left)

Regards,

Leddy
 
I'd set ch1-4 on hp with the Xover set to 100-120Hz. So you're just preventing the really low stuff getting through. And then the sub ch5 on LP at around 85Hz.

But you may want to leave the amp accessible for a few days so you can play around with it.

I know what you mean about the size. I just received an MRV-F407 and it's like twice the size of the older MRV-F400, but the same spec. Wierd.
 
Thanks Andy,

What about the gains and Subsonic filter? Should these be done to ear at the time?

And yes, its enormous! (its sitting on 12" floor tiles!).
 
The gains you'll have to do by ear, I found cabin speakers on mid setting and sub on nearly max gave the best results. Subsonic flter won't really make much difference as the stealth sub won't go down to 30Hz anyway, but I guess with it on you'll prevent possible damage.
 
there is actually a way to set the gain, hopefully someone like dean t will correct me if i'm wrong, but put a meter on the output connections of the sub and adjust the gain until the reading on the meter is about 40 something (something as in i can't remember the units, amps/volts whatever). If you can't bothered to do this, a safe bet is to just leave it at 9.00pm position, ie a quarter up. anymore and you could do damage possibily. Turn the subsonic filter on, it makes a hell of a difference, but probably not with the small sub though.
 
Alternatively if you can lay your hands on a pair of ears, they will give pretty good results!
 
I wouldn't put the subwoofer setting on max. i don't think that the sub will be able to take it.
Keep the gains as low as possible and let the headunit do some work with a nic strong signal for the amp to work with. check the spec of the speakers and see hwat frequency they can handle and then adjust your crossovers to your personal taste within these boundaries to avoid distortion. If you stay within these guidelines it will all depend on your personal taste of sound. Too many times I get in cars and the sub and rest of the music is seperate. Meaning the sub is too loud. You should be able to feel it but you should not know that there is a sub until you turn it off. try and aim for the sound to be smooth throughout the car when listening from the front cabin as this is where you will be spending the most of your time. To tune your system properly may take some time so goood luck.
 
I wouldn't normally suggest running the sub channel on near max, but the stealth sub needs to be driven hard. The enclosure is way too small to provide the additional volume you'd normally get from a large enclosure.
On the 10 or so I've installed I've had 300wrms running to the little JL sub, it's very conservatively rated, and the confines of the enclosure prevent it from over extending unless you start taking the p*ss with the Bass setting.
My wife's A3 is running an Alpine MRV-T505 bridged (300wrms @ 14.4v) to the JL unit, and the gain is set on about 80%, and that's with an Alpine HU 4v pre-out. Remember, you won't get 4v at the amp due to losses in the RCA's.
Admittedly I haven't had the luxury of a 4ch amp running all the cabin speakers with the low frequencies filtered, so you will be able to run the HU with a +ve Bass setting without overloading the cabin speakers. This will reduce the gain needed on the sub channel.
 
putting the gain on max is a bad idea, worst thing that can happen is that you will send a clipped signal to the sub and kill it, not good!

ideally the gains need to be scoped so the speakers have a nice clean input, meaning no distortion - distortion (or a square wave (as you would see on a scope when it clips) will kill your speaker)) put simply!

its fairly easy to hear a clipped signal on components, but in subs it can be quite difficult

crossover wise i would high pass the components at 80hz and see how they sound, then try them at 120hz and see how they are then - there is no general rule of thumb for this, it all depends on your ears and how the components deal with the bass

in my last install i had to low pass the comps @120hz so they could keep up with the heavy bass-end, the ideal x-over point (IMO) is 120hz

i would low pass the sub @ 80hz as this should be fine, leave the subsonic filter off as this is just forted ported boxes really, so the cones dont unload below tune frequency

the gain control is NOT a volume control, more of a sensitivity control with reference to your HU pre-outs, the biggest mistake people in general seem to make is that they treat it as a volume control and clip the hell out of their speakers then wonder why they go POP!

not sure if there are any ICE dealers in the channel islands but they would be your best bet to get your hands on a scope, if there arent just be careful with the gains /ubbthreads/images/graemlins/smile.gif

HTH
Dean
 
seeing as the amp is bridgeable would it not be better to bridge the channels to rn your comps up front then run the rears off the HU?

whats the recommended input (RMS) of your comps up front?
 
That's great in a perfect world. But as I said, the stealth sub is not theoretically perfect, constraints of space/size mean it is pretty inefficient. In theory it shouldn't even work, but it does, very well. So when you have it all setup perfectly, and you can't hear the sub, then try turning up the gain.
Hey, but what do I know?
 
but the gain shouldnt be used as a volume control, im trying to help someone NOT to damage their equipment!

indeed, subs working in smaller enclosures can[/b] take more input, but this shouldn't be done by using the gain as a volume control - if you need more power get an amp with a higher output
 
He hasn't got an amp with a higher output.
I've designed this sub, produced about 15 of them, and installed about 10 in various A3/S3's. None of them have been damaged and a couple have been running for at least 18 months with the gain on 80%+ with either MRV-F400's or T505's.
I don't know what amps you're used to using but Alpine V12's don't clip that easily, that's why you pay more for a well designed amp made with quality components.

 
EVERY amp will clip at some point

i've has a fair few amps myself, as well as dabbling with a lot of other brands in my time, from the old longmills to RFs, directed and then my current one, tru

as a 'general' rule i would never take an amps gain past half way, heck even thats pushing it somewhat!

quite ironic how everyone ripped it out of pimpmyaudi, then he comes along to give some corking advice in this thread re: the gain issue /ubbthreads/images/graemlins/wink.gif
 
So just ignore my reply then.
I didn't say they don't clip, I said they don't clip easily, i.e. you can run them really hard without distortion or clipping.
Look at the birth certificate and you'll see the actual power output of each amp, this is always at least 50% more than the specified rating i.e. 40wrms will actually push out 60wrms with 0.03 third harmonic distortion.
I doubt this is achieved with the gain set at 25%. It's all dependent on the input voltage anyway, so a 4v pre-out will deliver something a lot smaller at the actual amp, the gain compensates for these losses. So to generalise that 25% is correct in any situation is bullsh*t.
My recommendations were based on using identical kit to Leddy in an identical car.
 
aaaaaaarrrrggghhhhh

the gain is just a sensitivity control which is based on the HU voltage preout

it is not a volume control, therefore you cant say that the gain needs to be high to push out maximum output

i was just trying to be helpful to someone and you say im talking [censored]

using an amp properly is all about getting a clean output to your speakers

i'll just stay quiet in the future /ubbthreads/images/graemlins/lol.gif /ubbthreads/images/graemlins/wink.gif
 
So how many competition winning systems has Andymac installed and how many have others done as the advice given by dean T is spot on and andymac is wrong this time,i have never turned up the input gain of any amp more than half way and if you need to for a box too small for its speaker then it is a flawed design.
ps, 3 competetive installs under my belt and winning trophies to prove it.
Cheers "Bingo" /ubbthreads/images/graemlins/beerchug.gif
 
the gain control of an amp can be made by the designer for any input voltage - although for cars this tends to be with 4v rms in mind - 4v rms leads to maxiumum output power approx without clipping.

however, in designing a general purpose amp, you have the input stage more sensitive than required, with an adjustable gain control to allow for this -

now to reduce the power, you either reduce the driving line voltage, or reduce the input gain setting

for an audi head, you are lucky to get 1v rms on the line out, so the head is effectively acting like the gain is reduced to 25% of max of an aftermarket head. it makes sense to wind up the amp gain to enable max output or less on the head unit to drive the amp to max output power.

if you got this wrong, you might clip the amp at a much lower volume setting on the head and this would make the volume control on the head very sensitive with most of the upper range being no use.

the proof is in the listening - an andymac system at max sensitivity for the sub and 1/2 sensitivity for the rear speaker matches the front volume very well, and the volume control is quite loud but not deafening or distoring at about 1/2 output - this works well, gives good control of volume at the quieter end and gives me enough effective volume control for bleeding ears at the top end.

as for the volume being wrong etc in the andymac - of course it is! the design brief was to find an effective and affordable speaker that would produce decent bass hidden in the side pod - this it does very well. ideally the enclosure should be slightly larger and probably ported to be highly efficient, but there just isnt room.

i would rather have an effective stealth system thats a bit inefficient than a useless boot full of sub and amp for the sake of an extra few Hz or db that is academic rather than practical to listen to.
 
[ QUOTE ]
bingo said:
So how many competition winning systems has Andymac installed and how many have others done as the advice given by dean T is spot on and andymac is wrong this time,i have never turned up the input gain of any amp more than half way and if you need to for a box too small for its speaker then it is a flawed design.
ps, 3 competetive installs under my belt and winning trophies to prove it.
Cheers "Bingo" /ubbthreads/images/graemlins/beerchug.gif

[/ QUOTE ]
If you'd bothered to read the original question Bingo you would realise this isn't a competition system and doesn't pretend to be a one, it's a real world stealth system and thus dictated by restrictions in space & size. Anyone can fill their boot with speakers & amps and have the luxury to apply the quite correct advice given by pimp & Dean. But that wasn't the question. I answered the question based on 2 years experience of making and fitting this solution with fantastic results given the impossible restrictions. If this flies in the face of Car HiFi theory then who cares if it works?
Thanks Dunk, spot on feedback from someone who's actually done it.
 
If you have any decent system, why on earth would you have to put the gain anywhere near 80% to get some volume? I have 2 subs, and i wouldn't even think of puttin the gain more then a quarter up. As Dean said, the gain is NOT a volume control. Putting it up shouldn't increase the bass, it will just distort it and ruin the sub probably. I don't know, becuase like i said i couldn't even bare to put the gain up more then a quarter because i can just hear my subs popping.

A sub, whatever size it is, should run niceley on a quarter gain. If u need to push it up so much just to get some bass, then it is not the right sub to use.

And why is everyone talking about having a useless boot? Just becuase you hava a sub and amp, y do you assume your whole boot is going to be full up? A 10" sub and a small amp to run it would hardly take up the whole boot, not even half of it, especially if you mounted the amp on the back seat or something. For the same money as Andymac sub and the sake of loosing about 1 square foot of boot space at least you'd have some decent bass without putting the gain control in no mans land.
 
jojo said:
"I've got to give it to ya Andymac, just had a small demo of the Andymac Bose upgrade from a chap called Revdup. It's truly amazing how a 6" sub can sound so tight and clear, especially running off the standard headunit, total quality man! It's time I need to save some pennies for this future upgrade, and I NEED the boot space, just in case anyone thinks I should go for a seperate amp and sub"

Yeah looks like I've got it completely wrong, what was I thinking? I'll get my coat.....
 
no ones doubting your box building skills chap /ubbthreads/images/graemlins/smile.gif

just disagreeing with the way you set up amps /ubbthreads/images/graemlins/smile.gif
 
all this is bullsh*t about must only use 1/4 of the available gain- if every head unit and amp worked to the same standard for inputs and outputs, then there wouldnt be any adjustable gain needed - each head would be able to get exactly max power from an amp without distortion - as it is, thats exactly why amps have a gain control - to adjust for a variable feed voltage.

its nothing to do with the way andymac sets up amps - if the head unit puts out 1/4 the voltage of other head units, you have to jack up the gain somewhere along the line - with an oem head and an andymac stealth system the only gain adjustment is the head unit volume control and the rear amp gain. given that the head unit drives the front speakers, you have the adjust the amp gain to balance the rear speaker output power and the sub output to have a reasonable bass output.

if you have a neutral front/rear balance and wind up the volume control, the head unit will plateau which is driving the front speakers and they will distort before the rear speakers and sub which have a much better head room because of the larger power reserve of the additional rear amp.

if the sub was under powered and very inefficient it may distort due to the power requirements before the front speakers, but given the amp that andymac supplied and the power handling of the sub, this doesnt seem to be a practical problem.
 
thanks for that, really well written with correct use of commas and full stops.
 
No Dean, you're disagreeing with the way I set up an amp with the stealth sub.
I run a 10" Apline sub in my A4 with a T505 & an Alpine HU. I set this up in the traditional way. 20% gain, jack up the HU until it starts to distort, cut it back so it isn't distorting, then adjust the gain on the amp for a clean signal.
And yes it ends up at about 40-50% gain.
The rule book goes out the window with the stealth sub as it seems to defy the laws of physics, clean thumping bass from an enclosure the size of a shoe box. I don't even know why it works as well as it does, it just does.
However to get it to do what it does, given the limitations of cost and the need for a reasonably priced 4 channel amp to drive the sub and rear speakers, I found you have to jack up the gain on the sub channel way past what you'd normally set it to. Yes I could use a more powerful amp, but this would make the system a lot more expensive, and to what end? You'd get the same end result. If it was clipping and distorting then I'd have used a more powerful amp, but it's difficult to justify when it sounds so good. Again I don't know why, it should sound awful.
The other parameter is that, on most of these systems, we are using the Audi HU which drives the front speakers so we have no way of cutting the bass to the fronts other than reducing the Bass on the HU. So the sub amp is being starved of bass, and, as Dunk says, the pre-out is pretty feeble to start with.
Leddy's system is a bit different as he has a decent HU and is driving all speakers with a separate amp, so he may well find he won't need to go to such extremes on the sub gain, but it will still have to be higher than with a normal tuned enclosure.

You can follow all the theories and best practices you want, but when it doesn't work, you try other options. If this results in a setup that's a bit mad, but sounds good, who cares? In theory spending £900 on a CD Changer & Bose upgrade should sound good, but we all know it doesn't. In theory chipping an S3 to 300bhp is probably a bad idea but boy does it work well. Believe me I wasn't happy with the level to which I had to go and was waiting for the poor little JL unit to self destruct, but respect to the little sub, it just keeps taking it.

So please listen to one of my highly irregular setups before telling me I've got it wrong.


 
audi upgrades
andy, do you know what frequency the bass control works at for the audi head units? i would have thought the bass control works at a higher frequency than the 85hz you set the sub to - should the sub cut-in start higher up?

duncan
 
I don't know what frequency the HU works at, doubt if that info is easily available. I found that any positive setting on the Bass control started to colour the sound, giving that woolly/muffled effect, which is down to the quality of the HU I guess.
I just found that 85Hz seemed to give the best compromise between thump & volume. If you take it up to 100Hz you start to get coloration of the bass notes and a harder kick drum, which personally I don't like (like someone thumping you in the head), and strangely the JL unit seemed to struggle more at higher volume (but this is probably because the signal was louder.
You probably are getting some loss at certain mid/lo frequencies, but crossovers aren't digital, so you still get bleed through over 85Hz.
It's a big compromise with the Audi setup, as you know, unless you have separate mid bass drivers and control of the sub from the HU, certain tracks will always sound better than others. But with the Bass control on the HU being you're only way of adjusting the sub level on-the-fly I found 80-90Hz gave the best result with a variety of music
It's a shame you don't get amps with a remote crossover adjustment, but I guess they figure all the control should be in the HU.
 
You can get amps now with a remote frequency controler (JL do them i think), and also yes it should be set around 70-80hz for the bass. I don't think you'd really want a sub to be messing round with 100hz frequencies.
 
Pimp, do you know how the remote control works? Is it wired to an external controller or literally remote like a tv remote?
 
Andy, you've got the complete wrong end of the stick

I'm not talking about setting up an amp with your stealth sub, I'm talking about setting up an amp in ANY situation.

I simply pointed out to people to be aware of clip and killing speakers.

I HAVE NOT said anything bad about your sub enclosure, in fact if you take a look around the forum you will see that i have been trying to get a listen to one, in fact I was thinking or purchasing one from you!

Obviously i have upset a number of people on here by (allegedley) slating your sub build.

If thats the way it came across i apologise but i will not stand by while (IMO) bad advice is being given out.

Fair enough, I have now learned you guys dont want, or dont need to listen to what I have to offer. Its all good, I can accept that /ubbthreads/images/graemlins/smile.gif

I'll shut up now /ubbthreads/images/graemlins/smile.gif
 
No worries.
I think the confusion was concerning your answer to the original question which was how to set the amp up with the stealth sub. I answered the question based on my experience actually doing it. You replied stating that my recommendation was a bad idea, and then launched into the whole best practices thing and then it got a bit off topic.
I probably should have PM'd Leddy (who seems to have gone on holiday during this post) with the info, as I should have known the offence I would cause to the purists out there with such in car profanity.
I do understand the theory, and try to follow it within reason, but I find some people can't seem to differentiate between wanting a decent system and wanting one that takes over your life, makes your car usuable and wins Sound Off's.
There is some middle ground.
 
well well been away for a while and it's on fire.
well I've heard Andy's set up with his sub and it's good. I bought one off him and my set up is completely diferent and it sounds good. I disagree with Andy's set up but like I said it sounds good. my whole set up is amped and not relying on the Audi system at all not using the head unit or their wiring. A bit more work to install but the flexibility in tuning it in is a lot better. No matter what system this guy decides to use it will depend on his ears and his patience to take his time and tune it all in. You also need to remember that the sub is only a 6 incher and if you try and send the lower frequencies through it it will struggle at higher volumes and sound sh*t. So the crossover setting that I had on my amp for the 12" kappa sub I had is not the same as I am using for this little JL sub, there's no point. Infact it even sounds quite nice if you let some of the higher than normal sub freqencies sneak through. I've tried it. As regards to the size of the enclosure before I installed mine I took it down to My local installers (who I trust and are very good at what they do)and he said it was nice and that the subs are good and are designed for these type of small enclosures. But at the end of the day if you are running your system using any part of that Audi set up you're gonna have to do something wierd to get a good sound out of it. Also don't forget that most people think that they have got a good sound until they really hear a good sound.
 
[ QUOTE ]
AndyMac said:

I probably should have PM'd Leddy (who seems to have gone on holiday during this post) with the info,

[/ QUOTE ]

Not gone on holiday, just injoying the lively debate this has caused. Much better than a simple straight forward answer as i have now learned a bit of the theory behind it all too!

I think i'm just going to have to do it by ear, the sub channel of my amp is only pushing 150wrms at 12V and 200wrms at 14.4V so i shouldn't be able to do too much damage (hopefully).

Also Andy, I have a Mk1 AMSS and have noticed on later versions have speaker connections on the rear as the straight through cables caused leakage, are you offering an upgrade policy? /ubbthreads/images/graemlins/tongue.gif
 
Leddy, the price has gone up so count yourself lucky you were able to secure the "Classic" Mk 1 model at an introductory special offer price.
It also benefits from added efficiency by not having the losses that terminal posts introduce. /ubbthreads/images/graemlins/lol.gif
 
[ QUOTE ]
AndyMac said:
It also benefits from added efficiency by not having the losses that terminal posts introduce. /ubbthreads/images/graemlins/lol.gif

[/ QUOTE ]

Yeah and the back of the terminals reduce the volume of the box?

I can tell you're an Account Manager for HP, you'll be telling me next that your new Konika engined copiers are productive /ubbthreads/images/graemlins/lol.gif
 
Andy,
Its a bit confusing when they say remote, normally it would mean wireless. But in this case, it just means 'remote', as in you can do it from a place other then the amp. So yes, it is still connected to the amp via a wire. You can also get remote bass controllers, which controls the hz from a knob that is wired to the amp. I mounted mine in the ashtray in my last car, but found i wasn't ever using it so didn't bother with it. I guess its the same with the gain, realistically, how often would you need to change the gain? In the 3 years that i have had a system, i have NEVER changed the gain, other then when it was first installed just to get it right. But i beleive that with most of the new Alpine HU's, you can actually control all of the amp settings directly from the Hu, including the gain (as long as you have the Alpine amp as well).

What i do think is really usefull, is a bass level controller. My cousin got one with his JL amp, 500/2 model. It doesn't control the hz, or the gain, but purely just the volume of the sub. So if you get a song with not much bass, you can just whack the knob up, and it will increase the bass. This is much better then a gain controller i think.
 
Yes the Alpine CDA-9812rr has a whole host of control, including sub-crossover and digital time correction.
A few too many things to fiddle with.

That's the main problem with using the Audi HU with a sub, you have no independent control of the sub level, so have to rely on the just the Bass setting.
 
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