got a O-scope now how do i use it?

[Briggiboy33 2]

I have borrowed a tektronix TAS 475 four channel oscilloscope. It dosnt have the probes with it, i need to get them. And i want to use this to set my amplifier. So how do i make sure im testing my amp at 1 ohms? And what probes should i get? Any suggestions or tips for this would be extremly helpful. Im going to be testing a ppi bk1300.1d

[///M5 2,833]

Personally I wouldn't. No need. It'll force you to set it conservatively and I'm sure your music isn't recorded that way.

If you want to test the amp to see what voltage it clips at fine...but even then realize resolution wise looking at a waveform is not such a good way to do even this.

[95Honda 486]

^^agreed.

I wouldn't waste any time with this other than looking at output waveform. I have yet to see anyone on this or any forum set a gain objectively with an O-Scope...

Also, depending on that Scope (not sure wich one that is) it may not read RMS voltage, may just read Pk or Pk-Pk, so take that into consideration...

[Impious 1,476]

In case the other 2 posts weren't enough, I would also not recommend using the o-scope to set the gain. It doesn't resolve enough information to really be of any use.

[Briggiboy33 2]

Wow... lmao i thought iv read so many times like this is how to set it to its absolute maximum... how is this untrue? Because clipping really isnt that bad depending on the severity.. like i just spent 300 on a sub and 200 on an amp and if i burn either there is no way id be able to replace them. Lol but i could have sworn this was how to get the absolute most performance out of your amp... damn.. so just a dmm?...

[95Honda 486]

You can set up your gains however you like with a DMM or an O'scope. Problem is, if you change anything, and I mean anything in the signal chain, it is all a mute point.

If you set for visible cliping with an O'scope then you have to be 100% sure that is the same signal you play after you calibrate. I.E. if you set it with a sine wave, it is only good for a sine wave at that exact level. Music is much more dynamic than a sine and it is tough to see visible clipping with music.

If you set with a DMM you need to know the exact impedance. You can't do this with a single DMM. And even if you know the exact impedance, you have a tolerance given by the manufacturer for output power that cannot be used with confidence for setting up a clipping threshold.

Also, a small amount of clipping doesn't hurt a thing. In fact full clipping doesn't hurt anything as long as you stay under the manufacturers thermal ratings (assuming the ratings are not inflated). You need to fully realize how this works though...

So in a nut shell, don't turn the volume knob up too far, this will keep you from blowing things up. If you can't follow this, trade your amp in for one that is no more than 1/2 the RMS rating of the subwoofer and never worry about a thing...

[Briggiboy33 2]

So if i use the oscope to set my gains with a test tone at like idk what my bass boost is on my amp.. but ill look it up and use that frequency.. and have my head unit at +3 for subwoofer. And my bass knob maxed.. but i always leave my subwoofer level at 0. Would i ever get any clipping? And i dont use bass boost on the hu or on the amp. Would i just be over safe?... i bought the ssd15 with the cooling feature.. thats it. It is in a 2.5 cuft box tuned to 33ish hz.. am i just being to worried? Right now when i play the sub with 1300rms it gets quite warm after one song that hits hard.. this is why i wanted to try and set my gain "right".. so i dont burn it up... the port is 18.125 x 2.25 so its about 16^2in to cuft.

Edited June 11, 2012 by Briggiboy33

[95Honda 486]

Depends on what level the tone is recorded at. If you have play a song that has a higher level than the tone (possible 99% of the time) you will have more power output.

Additionally (even with cooling) you have enough power on tap to thermally damage the subwoofer, without any clipping. With a heavily clipped signal, that amplifier will put out well more than enough power to cook the driver. Don't mistake the driver being cooked from the clipping, it is just the fact that the amplifer can produce more continuos power with a clipped signal, the clipped signal in itself is no different to the driver than an unclipped one.

So in reality you have more power than the your driver is thermally rated for. Your right hand is going to determain how long it (the driver) lasts...

[Briggiboy33 2]

But the ssd is rated for 1000rms. Cooling is supposed to give it 300-500 more... did i just waste the 30 bucks for the cooling?...

[reelfish92 54]

Good info up there guys. Those subs can handle a lot more with "clean power". If you're sending a clipped signal you are going to damage your equipment. You didn't waste money by adding the cooling option, just know your systems limit(s). Low voltage, bad signals and bass boost will hurt your equipment in the long run. *Turn bass boost and "sub level" to 0, there is no reason to turn those up. I used a DMM on two different system's, in both cases I was pushing a lot more than RMS on the subwoofers. I ran over 3.5k to a btl and never had coil smell or had the amp go into protect.

Edited June 11, 2012 by reelfish92

[95Honda 486]

No. Clean power has nothing to do with it. A clipped signal has never hurt anything. If you are listening to FM radio, you are listening to clipped signals.

Too much average power is what destroys a driver. This concept (lack of understanding it) is what gets people in trouble.

It is a missconception to think you are delivering a full amplifier's power into a subwoofer on a continuos basis. Without constantly knowing all variables (impedance, drive voltage, signal, back-EMF, etc) in real time, you have no idea what amount of continuos power you are actually driving the subwoofer with. Most people believe they are "giving thier subwoofers more than RMS" when in reality they are not. RMS thermal ratings are provided by the manufacturer for a reason. To let you know the thermal limitations of the voice coil in it's given motor assembly.

[dbsupra 69]

You guys make it out to be like rocket science.

Yes there is no way to set it and forget it for maximum output 24/7. But no reason to make it overly complex.

You can use a dmm or o scope to set it. Use a series of different test tones in the bandwidth you have the sub set for. I usually use -3db. Set the head unit how you want it. And whatever you do don't use bass boost. Tune the gain until you see clipping then back it off a touch with a scope. Or you can use the math method and use a dmm.

Sure music is dynamic and this won't allow you to squeeze every last watt out of the amp but it is a good way to safely set it.

Most importantly however is you need to train your ear to what clipping and mechanical limits sound like to keep yourself out of trouble.

* This is my humble opinion and take it for what it is worth. I'm sure there are going to be people that disagree with me but this is how we have done it for 19 yrs.

[Impious 1,476]

You guys make it out to be like rocket science.

Yes there is no way to set it and forget it for maximum output 24/7. But no reason to make it overly complex..

I would disagree. The people who think you need a DMM or O-scope to "properly" set a gain make it overly complicated, especially since both methods are completely misused and misunderstood. It's something you can do satisfactorily with nothing but your ear. No need to pull out equipment and test tones only to end up with a gain that's still not necessarily properly set.

As 95Honda said, a little bit of clipping isn't bad and running it into that range will allow you more dynamic room and average output compared to setting it with a conservative method and test tone. You are leaving power on the table with those methods and not really gaining anything in return.

[///M5 2,833]

Since 95 & Imp have already stated pretty much dead nuts reality I'll respond to one thing that hasn't yet been addressed enough obviously.

You can use a dmm or o scope to set it. Use a series of different test tones in the bandwidth you have the sub set for. I usually use -3db. Set the head unit how you want it.

What benefit is that. You just set some VERY arbitrary variables to a constant. Any spot on your head unit and -3dB. This means that for songs you'll be using your ear to adjust. Why not just do that in the first place? No matter what the choice of levels it's arbitrary as it will never match your source. In fact doing this gives people false confidence and they then turn things up and melt drivers. Outside of competition there really should never be a reason to destroy a driver other than confusion and lack of listening on the person controlling the volume knob.

Of course the worst possible thing you could use for setting your gain is the SMD douchebagortion detector.

[dbsupra 69]

I use my ear to tune. Problem is a lot of people don't know what they are listening for.

I use -3db because most sources don't peak that high and it gives some overhead. I can't ride around with everyone and control the volume knob for them. This is how I was taught when I started in car audio.

I think of it much like I tune cars. My supra makes the most hp at 12.3:1 a/f. But that is on the ragged edge of detonation. Bit of bad gas or a weird blip in my timing map and it gets ugly. So I tune for 11.5-11.8 Sure it leaves some hp on the table but I have a margin of safety.

Perhaps I've been going about this the wrong way. But it has worked in my experience. That being said I'm always open to learning new things. That's what.brought me here in the first place.

[///M5 2,833]

I use my ear to tune. Problem is a lot of people don't know what they are listening for.

I use -3db because most sources don't peak that high and it gives some overhead.

So you don't listen and adjust when playing music?

Again, it all comes down to goals but picking a value IMO is absurd. Why not use -10dB and never turn it up all the way and listen for stress. Why not use 0dB and never have anything to worry about. Why tune beyond the distortion level your ear can hear? Why not tune to textbook no distortion so you never have any?

I could go on, but perhaps that helps. An O'scope is a useful tool, just not so much for car audio. Obviously if you have a $50k Nicollet it'll have the resolution and processing you need to do something but a simple waveform view just isn't helpful. Even worse is the Deeee Deeee One. Obviously meant to steal money from the uninformed. Personally I find the most useful tool in car audio to be the DMM, but I've never set a gain with one.

[///M5 2,833]

And just to be clear. Read my sig. I am not trying to rip on the OP, but instead ripping on the asshats that made him feel like this was the way to go. I thought I should clarify since it was obvious to me, but that rarely means obvious to the other thread readers.

[Sencheezy 689]

I just made this post a few nights ago, it may be some help to you.

On mobile, so I will give a quick personal opinion. Yes, it is safe to set your settings via that fashion. Personally, I wouldn't, and ill tell you why. Its because A, music is dynamic, and B, every system will play differently in any given environment. Understanding that is key when using these given techniques and guidelines. Because thats what they are, simply guidelines, to steer your tunning in the right direction. The way I set my settings, maybe not the best way in the world, or most accurate, but will too suffice. And the tools are my sences lol seriously. If I see/hear or smell any kind of warnings from the driver(s), just back down on the setting.

Take my opinion for what its worth lol

To set ssf, set to port tunning, play a song that you know plays low, and put on repeat. Now, turn HU volume to max listening volume, and slowly turn down the volume until you see or smell anything abnormal. Yes its possible to play wide open.

To set gains, do the same thing, select a song your most familiar with, that has bass, start off with gain low, set to maximum listening volume, then begin turning up gain until you see anything abnormal.

Now remember, these two settings are intertwine, at least for me lol, so this can be a long process and hours of testing. Also, each song will require minor tweaking, as a direct relation to the audios recording, and the quality of the source you have. But the main idea is to be in the general ballpark for each song.

I hope this helps, let us no if you still need help : p

[Briggiboy33 2]

Thankyou everyone for your input. My last set up i tuned by ear and that was easy to hear distortion. But this new sub is alot louder and its a lot harder to hear the distortion.. if its distorting.... and also my electrical isnt up to par so i cant sit and listen to it like focusing hard... lol but i guess ill just adjust as i go. Like one click down or up depending how the songs i listend to sounded.

[///M5 2,833]

You can start by training your ears. Best to do that with a solitary driver(s). Ie, shut your mids & tweets off when listening to the sub. Teach yourself what stress sounds like and go from there.