ragnarock2

I have a MRD M300 v12 amp, powering a 12" 4ohm dvc type R sub.
It is all connected as should be (according to the type R manual). It doesnt seem very loud (i.e. the headunit needs to be turned up to near max to hear the sub).
Any ideas what it could be (and also can you confirm that to wire a dual 4ohm speaker to 2ohm input, I need to connect the +'ives together and the -'ives together on the voice coils - then connect 1 =ive an 1-ive to the input).

The amp is 300 watt RMS @ 2ohm, but it really doesnt seem very loud. I have set the input level to 4volts on the amp (headunit outputs at 5v) - my mate has a cheaper system that sounds much louder!

PLEASE HELP!!!!

chiark

+ and + commoned up and connected to + of amp, - and - common and connected to - of amp will give you a 2 ohm brided load.

Is the amp happy to drive a 2 ohm bridged load? You might find that it has protection circuitry to limit the current delivered if it isn't happy. Most amps are 2 ohm stable in stereo mode, but not all are happy to drive 2 ohm bridged (equivalend to a 1 ohm stereo load).

If all is good with the amp... First off, check for silliness like a high pass filter enabled on the head unit... Or a high pass on the amp, or ... You get the picture.

Gains need to be set by ear - ignore the marking. Turn the gain up *carefully* with the head unit set to about 7/8ths of max volume with all equalisation and loudness off.

The sound of a sub in pain is obvious. Less obvious is the onset of clipping with a sub, which is where the amp is driving a DC signal into the sub which can knacker the voicecoil. If the sub smells, turn it down. If it distorts, turn it down.

Bear in mind that output will depend upon box style too... Is the box big enough? Is it properly sealed?

chiark

The amp'll be fine driving 2 ohm mono...

ragnarock2

Chiark, the box came from alpine as well - designed for the sub, it is a sealed enclosure.
seems odd, as i thought it would be quite loud!
Head unit is a panasonic 983 mp3/wma player if that helps anyone find out whats wrong?
The instructions for the amp did say I had to increase the volume of the head unit until its 'over' light came on before adjusting settings, but on full whack, I could not get the over light to light up!

atche

Try these settings on the amp:

Input (1-3) setting:9dB
Set X-over (2-2) at 80 Hz
Subsonic filter (3-2) at 25Hz
Parametric EQ (4-2) at 50hz, (4-4) at 10 dB
Bass Comp (5-1) set at ON.

Any problems, email me.

chiark

10dB is a feckoff load of equalisation! A 3dB increase requires a doubling in power... 10dB requires 2x2x2 + a bit, or 8 times the power!

That is a *guaranteed* way to be feeding the sub a badly clipped signal unless you've got the gain set very, very, very low.

ragnarock2

Atche, could I have your e-mail address, as I would like to know what setting does what?
Also, i have no option 1-3, 1-2 is the input setting, and I can only set that from 0dB to -18dB.
Didnt realise that eq would make the sub louder?

atche

That is the maximum output setting, and it can be used to "work back" from. It is the recommended setting in the American Alpine Authorised dealer sales reference guide for demoing on a shop stand. I tried the setting on a 4OHM! sub after a mate of mine complained about a lack of power using a MRD M300, and found it was WAY TOO LOUD. We turned down the gain, then the Parametric EQ, and he was happy :-) Hopefully Ragnarock will find the same result. The MRD M300 has 300W RMS at 2ohms, so there should be no problems of a lack of power when running his type-R sub. As the MRD M300 has a Digital DSP 24bit A/D, and this signal is then amplified in a true class-D circuitry, he shouldnt have any problems with damaging his sub which is 300W RMS, 1000W peak. I admit the setting is a bit extreme, but it should answer his question of a lack of power.

chiark

ah great, i see where you're coming from. Cheers for that advice, if I read it correctly you're saying start there and work back?

ragnarock2

Will try when I get back from work and let you all know the outcome (sub sounds fantastic even when quiet as a fart!) Why can't we go back to a simple gain setting!!!

atche

Simple gain settings - yes I understand what you mean. However, this method of setting up has its advantages, although ease of setup isnt one of them!

The accu class-D circuitry means that this class D amp has DSP prior to amplification, unlike many other Class-D amps which has adjustments after the signal has been amplified. It means that there is no wastage in Power, and the settings are exact. For example, if you set the x-over at 80Hz, as the DSP is digital, it would be exactly 80Hz and not 77Hz or 84 Hz etc, as could be the case using a potentiometer.

But you are right, someone should tell the boffins at Alpine that there should be an easier menu system!

ragnarock, let me know how you get on, and if you need more help just call me and I will go through the set up with you.

Good Luck

ragnarock2

Many thanks atche, at 10db is it likely to burst my eardrums then? (as i assume it can only be running at a fraction of its potential at 0db)?

ragnarock2

Didnt try last night as it was p1ssing it down! WIll try after work tonight!

ragnarock2

Just had a quick play before starting work. Have set input to 0DB, and parametric EQ to +10dB distorts like hell now!
I think that I need to lower the input to say -12dB as my RCA leads are emitting 12V and at 0dB i think the amp is expecting 0.5v or similar.

If not, could it be the Parametric EQ which is making it all distort? (it is now a fair bit louder by the way)!

Atche, is it OK to call you tonight to go through the settings?

[Edited by ragnarock2 - 8/29/2003 10:16:32 AM]

chiark

The parametric eq can cause it to distort, yes. you're asking it to deliver just over 8 times the power that it normally does into the 50Hz range!

atche

By all means call me - I will be happy to explain the settings. The thing to do is to lower the Parametric EQ. Also If you like tighter bass, set the frequecy higher, and for deeper bass, lower. You can adjust the bandwidth as well so it wont be just at 50hz where you are boosting. As I said, the settings i gave you were MAX, and you need to work back from it. Just one thing - I dont think your headunit will be giving 12V at the RCA..

Speak to you later

Atche

ragnarock2

head unit is 5v at the rca's, amp is designed for maximum of 4v i believe! I will call you later tonight mate, thanks for your help!