I set my gain with a DMM

[Beatin' 10+ year member]

and I'm not happy with the results.

EQ flat, loudness off, no boost, LPF maxed out, etc...

Used a 50hz 0db test tone downloaded from that realmofexcursion.com website. On the windows media player it showed the wave clipping noticably. I don't know if that will affect the DMM readings. Does it?

So I set the HU at the volume I prefer, 30/50. The subs were unhooked. I set the DMM to AC voltage, and put the test leads (I think that's what they call them) on the correct +- terminals. I played the test tone while the HU was at 30/50. I gradually increased the gain until the DMM read around 33-34 volts.

My amp is a kenwood 8105d and it's rated 300wrms at 4ohms. 300x4=1200, the square root of 1200 is 34.64.

I road around playing sine wave bass heavy tracks, which I believe were all recorded at 0db. How do I know that? I have no clue other than watching the waves on the windows media player oscilliscope. lol

But it wasn't loud like it used to be. It seem like before, I was heavily driving the amp beyond it's rated output and not recognizing any clipping. But it sure was loud. //content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif

So did I do anything wrong Or did I just realize what was wrong all along? Also does it matter that the subs were unhooked? Voltage will change to a lower number if impedance is lowered so how the hell does the amp know what impedance it is seeing when the DMM is being used? Does the DMM have an impedance load that will affect the readings? 300wrms at 4ohms is 34.64 volts. 300wrms at 2ohms is 24.50. Soit seems like there should be a load on the amp before testing, correct?

I'm so confused...........

Click to read more...

 

[neo_styles 10+ year member]

Your ears probably got used to distortion. That or your subs can safely handle over rated RMS. What sub are you setting up and what type of enclosure?

 

[Beatin' 10+ year member]

Your ears probably got used to distortion. That or your subs can safely handle over rated RMS. What sub are you setting up and what type of enclosure?

2 15" 150wrms radio shack subs (don't laugh) in an atrend prefab sealed box, supposedly around 2.25 cubic feet per chamber but I've heard that they're actually around 1.6-1.7

I got another question for those who know.

When using the formula watts x resistance = volts, do the watts have to be RMS or peak?

300wrms x 4ohms = about 34.6volts

600 peak watts x 4ohms = 49volts

which one is correct for gain setting? I used the RMS method.....

 

[IonRL205 10+ year member]

You're running 300 rms to some cheap subs in a garbage enclosure

You're not going to get good results at all

 

[neo_styles 10+ year member]

2 15" 150wrms radio shack subs (don't laugh) in an atrend prefab sealed box' date=' supposedly around 2.25 cubic feet per chamber but I've heard that they're actually around 1.6-1.7
I got another question for those who know.

When using the formula watts x resistance = volts, do the watts have to be RMS or peak?

300wrms x 4ohms = about 34.6volts

600 peak watts x 4ohms = 49volts

which one is correct for gain setting? I used the RMS method.....[/quote']

You want RMS. You're not getting good results based on the fact that 300W sealed on 2 subs isn't going to give you much impact at all. At least the subs are running safe now, though. Consider looking up the T-S specs on that sub and getting a ported enclosure designed around your subs. Should find the oomph you're missing.

 

[Chriszle 10+ year member]

If your listening to music only, you can use -3 or even -5 db tracks to set your gain.

 

[Beatin' 10+ year member]

You're running 300 rms to some cheap subs in a garbage enclosure
You're not going to get good results at all

Dude that atrend box is huge. I could barely get it in the trunk. I could build a bigger one but it will only fit in the basement.

You want RMS. You're not getting good results based on the fact that 300W sealed on 2 subs isn't going to give you much impact at all. At least the subs are running safe now, though. Consider looking up the T-S specs on that sub and getting a ported enclosure designed around your subs. Should find the oomph you're missing

Digging through the net, I found parameters that another guy got from the box which I lost.

here they are:

25 - 2000 Hz

91 db/1W/1m

Fs 25 Hz

QES .71

QMS 3.22

Qts .58

VAS 523.9 l

excursion 3.8 mm

further more, I'm not a fan of ported boxes.

If your listening to music only, you can use -3 or even -5 db tracks to set your gain.

why?

 

[cdc351jeferson 10+ year member]

Dude that atrend box is huge. I could barely get it in the trunk. I could build a bigger one but it will only fit in the basement.


Digging through the net' date=' I found parameters that another guy got from the box which I lost.

here they are:

25 - 2000 Hz

91 db/1W/1m

Fs 25 Hz

QES .71

QMS 3.22

Qts .58

VAS 523.9 l

excursion 3.8 mm

further more, I'm not a fan of ported boxes.

why?[/quote']

a prefab box is not tailored to your sub. also if you saying you dont like ported you havent heard a properly build and tuned enclosure . a prefab ported ***** of course . dont expect much output with low power on cheaper subs in a sealed box i would port them if your not planning on upgrading soon

 

[IonRL205 10+ year member]

Dude that atrend box is huge. I could barely get it in the trunk. I could build a bigger one but it will only fit in the basement.

A sealed box with 2.5 cubic feet per chamber is not huge at all. Just because you could barely fit it in your trunk doesn't really mean anything' date=' it just means your trunk opening is small.

You're running low power to some subs that are in an enclosure that is ridiculously small.

Is this your box?

15" DUAL SEALED

If so then my two 10s are in a box about the same size.

And why don't you like ported boxes?

You must not have heard a good ported box then, because it would definitely change your mind.

 

[Beatin' 10+ year member]

It doesn't look like my box. My box has different terminals. You lift them and they're spring loaded. Also the sides are reccessed.

Maybe what I need are some proper car audio subwoofers? I mean these radio shack subs have a VAS rating of over 500L, doesn't that mean they need a huge enclosure? Aren't car audio subs usually around 100-200L, so they can be used in smaller boxes?

 

[Beatin' 10+ year member]

Can I use the DMM while the subs are hooked up? Will I damage something? Will the DMM not get a good reading?

I got some songs that play full amplitude sine waves non stop. I figure it would give a good voltage reading.

 

[ForceEdge 10+ year member]

If your listening to music only, you can use -3 or even -5 db tracks to set your gain.

Heard its not to wise to do that

 

[IonRL205 10+ year member]

It doesn't look like my box. My box has different terminals. You lift them and they're spring loaded. Also the sides are reccessed.
Maybe what I need are some proper car audio subwoofers? I mean these radio shack subs have a VAS rating of over 500L' date=' doesn't that mean they need a huge enclosure? Aren't car audio subs usually around 100-200L, so they can be used in smaller boxes?[/quote']

Are you just not reading anything in this topic or what? You're running low power to some cheap subs in a sealed box. If you want those subs to shine, you need a ported box. I don't understand why you don't like ported boxes. My two 10s in their ported box would be louder than your two 15s in your sealed box on the same power. I've had sealed 15s before and then I went with a single ported 15 and it completely destroyed the sealed 15s in sound quality, loudness, and frequency response. My two ported 10s destroy the sealed 15s I had as well.

If you really want to make use of those subs, go with a ported box. You can have the box built to your musical taste and it would do so much better for you. What's the point in coming here asking for advice if you don't want to take it? Your setup the way it is isn't going to be loud, period.

You went the cheap route and got cheap results and that's all you're going to get. You can either take my advice and get a better enclosure or you can just keep what you have and continue to be disappointed. There's not much else that can be said to help you. If you want to see huge improvements, then you should just change everything you have. A good pair of ported 12s on 1k to 1.5k in a good enclosure will be a lot louder than you might think.

Heard its not to wise to do that

I always do that

 

[ForceEdge 10+ year member]

I always do that

I made a thread awhile back and everyone said no just use 0db 50-60hz because -3db can blow my subs or fry my amp. I even said it seemed highly unlikely because I'm not listening to 50-60hz sine waves all day.. I listen to music.. And they still insisted in using a 0db.

 

[calebkhill 10+ year member]

Aside from the manufacturers suggestions how would one know if there subs should be sealed or ported