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RMS Question - Will I blow my Tubes?

 
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Old 19 Mar 2011, 07:01 pm
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Default RMS Question - Will I blow my Tubes?

I have two Bazooka BT8024DVC bass tubes. These are dual voice coil 4ohm amp bass tubes.

http://www.crutchfield.com/S-jARwyAc...BT8024DVC.html

These are 400 RMS, or 200 per voice coil.

My amp is an Alpine MRP-M500, 500 RMS. This is a mono amp.

If I wire up BOTH tubes, they won't blow, correct? (Because combined it can handle up to 800 RMS and since the amp is only putting out 500 RMS max, I'm assuming I should be fine)

But I'd thought I'd ask first!

This is how I plan to wire them up:

http://a248.e.akamai.net/pix.crutchf...4-ohm_mono.jpg

Any info is appreciated! Thanks!

Cilos
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Old 19 Mar 2011, 11:54 pm
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Default Re: RMS Question - Will I blow my Tubes?

Very much so you can blow them! You are greatly underpowering your setup.

As long as your gain is set properly on your amp, you're not blasting your stereo like a teenager, and you don't turn up bass boost features and the sort you'll be fine.

The way you'll have your system hooked up, your subs will share 300 watts between the both of them. Your amp will only put out 500 watts if wired down to 2ohms, but that'll come with some slight distortion (those Alpine's are entry-level).

One thing that alot of people are confused about and need to understand is that you run a great risk of blowing your speakers by underpowering them as opposed to overpowering. When you turn up your speakers, you're asking that they play at a certain level. With this, they demand a specific amount of power from your amp (which is why we call your speaker a load). Well, if your speaker doesn't receive this demand it'll attempt to achieve the SPL you're looking for and eventually it'll destroy itself in doing so by distorting horribly and blowing out/tearing up the voicecoil.

Reason you can't exactly blow a speaker up by overpowering it is because a quality speaker can achieve very high SPL. If you meet it's demands, said-speaker will play amazingly loud+clear at levels that'll make your ears bleed! Your ears will give out before your amp/speaker/volume knob does. This is especially true of high-end home audio, whether it's 2-channel or home theater.

Trust this coming from an audiophile, listening to and building quality systems to include modifying my own components/crossovers and so forth for over a decade.

If you want/need any advice, drop me a line or post your question here so I can address it publicly.

-Freddy
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Old 19 Mar 2011, 11:58 pm
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Default Re: RMS Question - Will I blow my Tubes?

Random thought: I like the title 'Fanatic Cruiser' found underneath my handle however I wish it was something like 'The Forum's Audiophile'
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Old 20 Mar 2011, 10:04 am
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Default Re: RMS Question - Will I blow my Tubes?

Thanks Freddy for your advice on this one! One thing I didn't realize, until reading your post, was that with dvc's they can be wired differently and the ohm load can change, even based on only 1 or 2 dvc tubes.

Is there some equation or something to figure out what the watts per ohm are? Is it static, meaning, if a 2 ohm load is 500 watts, a 4 ohm load is 300 watts? How does one figure that out?

Thanks again, really glad I'm asking these questions here!

Matt

Last edited by Cilos; 20 Mar 2011 at 10:20 am.
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Old 20 Mar 2011, 12:58 pm
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Default Re: RMS Question - Will I blow my Tubes?

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Originally Posted by Cilos View Post
Thanks Freddy for your advice on this one! One thing I didn't realize, until reading your post, was that with dvc's they can be wired differently and the ohm load can change, even based on only 1 or 2 dvc tubes.

Is there some equation or something to figure out what the watts per ohm are? Is it static, meaning, if a 2 ohm load is 500 watts, a 4 ohm load is 300 watts? How does one figure that out?

Thanks again, really glad I'm asking these questions here!

Matt
You're limited to the different loads you can create with 1. the number and the type of subwoofers you're running and 2. the type of amp and the loads it can handle.

There's no equation here as to how many watts per ohm, it just takes a bit of looking at your amp.

It's rated at 300 watts @4ohms, and 500 watts @2ohms.

You'll find that if you look around, another amp rated at 300 watts @4ohms could be rated at 400-600 watts @2ohms.

Other than a few rebadged amps, all amplifiers are created differently using different internals. Just because amp A is rated higher than amp B, doesn't mean amp B can't play a sub better, and with authority.

Try this out;
When you've got your amp hooked up and ready to connect your subs, connect only one subwoofer to create a 2ohm load. This single sub will potentially see the full 500 watts your amp can put out.

Now, with everything off go ahead and connect both subwoofers to your amp to create a 4ohm load. Both subs now sharing 300 watts, tell me how it sounds.

You'll better SPL with both subs running (depending how that amp runs and how sensitive your subs are), but you might notice a 'lack of control' at higher volumes compared to running a single sub. You should be able to pick out better detail with greater dynamics throughout your entire volume range on a single sub.

Not sure what you're after exactly, but if you're happy with your setup then by all means keep it! If you're looking to step up to a different/better setup just let me know.

And btw, I wouldn't worry too much about blowing your speakers out due to lack of power. Ported subwoofers can get away with being underpowered a bit, whereas a sealed subwoofer at minimum should see it's maximum power handling capabilities...if not more.

Don't know what kind of music you're listening to, but just make sure your subsonic filter is on.
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Old 20 Mar 2011, 01:08 pm
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Default Re: RMS Question - Will I blow my Tubes?

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Originally Posted by Kawizx9r View Post
When you've got your amp hooked up and ready to connect your subs, connect only one subwoofer to create a 2ohm load. This single sub will potentially see the full 500 watts your amp can put out.
I see so ohms to watts is based on the amp's output, I see.

A week ago two of the tubes arrived.

As far as the above, I did, 3 days ago. Cranked it up for a good 20 minutes, started to smell something, and the tube went out. Took it out, looked at it, the cone appears fine, but the woofer won't move at all, as if it's, locked into place. Naturally, that was a 2 ohm load at 500 watts and these voice coils are rated at 200 each, so 400 max... (facepalm)

In the mean time I ordered a replacement, that arrives Tuesday at which point I'll hook up both tubes, creating the 300 watt 4 ohm load. So that's the initial reason for my post. I just didn't want to again blow one, or now possibly two out.
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Old 20 Mar 2011, 01:11 pm
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Default Re: RMS Question - Will I blow my Tubes?

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Originally Posted by Cilos View Post
I have two Bazooka BT8024DVC bass tubes. These are dual voice coil 4ohm amp bass tubes.

Bazooka BT8024DVC BT Series 8" Bass TubeŽ with dual 4-ohm voice coils at Crutchfield.com

These are 400 RMS, or 200 per voice coil.

My amp is an Alpine MRP-M500, 500 RMS. This is a mono amp.

If I wire up BOTH tubes, they won't blow, correct? (Because combined it can handle up to 800 RMS and since the amp is only putting out 500 RMS max, I'm assuming I should be fine)

But I'd thought I'd ask first!

This is how I plan to wire them up:

http://a248.e.akamai.net/pix.crutchf...4-ohm_mono.jpg

Any info is appreciated! Thanks!

Cilos
YOOOO,

Your amp is only pushing 300 RMS @ 4 ohms.

300 watts RMS x 4 ohms (500 watts RMS x 1 at 2 ohms)

Alpine MRP-M500 Mono subwoofer amplifier &mdash; 500 watts RMS x 1 at 2 <b style="color:white;background-color:#00aa00">ohms</b> at Crutchfield.com

Many mono amps have 4 speaker terminals; yours only has 2

http://www.sonicelectronix.com/pictu...cture_id=89796


Your subs are 400 RMS each

You have 2 subs 4 ohms DVC

You are severely underpowered your set up. You are providing 300 RMS to a 800 RMS subwoofer set up.

I would suggest you get the same exact amp; and run 1 amp per 1 tube.

Then I would wire each 4 ohm DVC sub down to 2 ohms. Your amp would them push 500 RMS, and your sub can handle 400 RMS. From there I would turn your gain down on your amp; till you get around the 400 RMS area. This will also extend the life of your amp; since you are not pushing it too hard.

Wire each tube like this:


Last edited by SergeantPtCruiser; 20 Mar 2011 at 01:21 pm.
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Old 20 Mar 2011, 01:19 pm
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Default Re: RMS Question - Will I blow my Tubes?

Didn't know you just got your subs.

One thing that's extremely important here;
SPEAKERS NEED AT LEAST 150-200 HOURS FOR BREAK-IN.

New, you don't ever want to blast your speaker. What you described is exactly what I was talking about, a blown voice coil Sure you could've sent the right amount of power to your sub but we don't know what your gain settings are at, the bass levels (if any) on your amp, and what DSP functions you have on in your headunit. All these 'bass enhancers' should be eliminated until you've properly installed, dialed in and broken in your subwoofer.

Depending how often you drive, it could take up to 3-4 months to properly break in your subwoofers.
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Old 20 Mar 2011, 01:24 pm
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Default Re: RMS Question - Will I blow my Tubes?

Haven't messed with the amps dials yet. They were about 50%.

Head units settings were +15 sub +7 bass.

So I guess the story here is, put in the two tubes this week, dial back everything for a couple months and then revisit at that point.

Thanks again for your help here, had I only asked before!
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Old 20 Mar 2011, 01:24 pm
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Default Re: RMS Question - Will I blow my Tubes?

Sgt, I covered all that and more above.

Only reason I haven't made a suggestion is because the OP has yet to tell me his/her end result since I just recently asked.
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Last edited by Kawizx9r; 20 Mar 2011 at 01:32 pm.
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