under powered sub

Back ground: My friend and I are building a system for his 2000 Maxima. He has already bought Polk MMC6500 for the front, MMC650 for the rear, a Soundstream TRA960.4 amp, a pioneer head unit, and the soundstream SK4/8CAP 2 amp wiring kit.

Now he doesn't have enough money for the Sub and the amp for it at this time. So I was going to let him borrow my Crossfire BMF W12D sub (I've read 300 and 350 rms so I'm not sure)  and an amp that was giving to me, boss rev-265 85w x 2 @ 4 ohms.

I've spent about 2 hours today researching this subject and I have read so many things that I don't know what to believe. So far i'm leaning towards it's ok to run this setup as long as you don't turn the gain all the way up.

I also have an old Alpine 3528 amp 80w x 2 @ 4 ohms. Could I put these two amps together?

Thanks

widerides wrote:

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I also have an old Alpine 3528 amp 80w x 2 @ 4 ohms. Could I put these two amps together?

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I think DYohn might have over looked this, but the answer to this one is no, one amp or the other.

One amp or the other and if you try and bridge either amp, the sub must be ran in a series circuit or you will crispy critter either of those small amps.

forbidden wrote:

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One amp or the other and if you try and bridge either amp, the sub must be ran in a series circuit or you will crispy critter either of those small amps.

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The boss amp is 2 ohm stable. Would it still crisp it? If so should I run the 10-20 year old Alpine, it looks a lot better built and cleaner. Maybe it's underrated?

I think all signs point to the Alpine.

As far as your question "could I put these two amps together?"..I would say with authority, please don't.

As far as underpowering the sub have no fear...that is a myth. Like others stated watch the gains..Without getting technical and starting a posting war..lol, I can say an ignorant attempt to squeeze out more power then the amp is capable of for the sake of more volume can damage stuff.

I have seen cases where doing this actually damages the amp..not the sub..that's not debatable because I have done it myself trying to destroy a sub...I inadvertanly killed the amp after hours of trying to kill the sub.

Perhaps haemphyst is right..however I have never had the thought to try that...running one coil of a DVC sub bridged to a boss amp...and the other coil bridged to an Alpine amp????   I don't know..this is like audio hieracy...it just doesn't sit well with me.

You don't think the different charactoristics and specs of those 2 amps could wreak any havoc on that poor speaker trying to work together??  Maybe it's just me..lol

Not that it matters it's more of I'm wanting to learn.

So I bridge the alpine to send 160 watts to one VC and bridge the boss amp 170 watts to the other vc, would that be a 4 ohm setup?

Also is there more distortion in a 2 ohm setup than a 4 ohm setup? more in a 4 ohm than a 8 ohm?

Would this funny month long setup sound quality sound better with the two amps or just one?

Thanks for yalls replies

Ok heres how it works out...

Each voice coil is 4 ohms. you are using amplifiers that are 2 ohm stable in stereo..which means the lowest impedance you should bridge to either amp is 4ohms. Connecting a 4ohm load to a stereo amplifer bridged to both channels..is running the amplifier at 2 ohms..so technically..this setup if using both amps this way will be two-2ohm setups.

As far as if there will be more distortion with a 2ohm vs a 4ohm vs an 8ohm has to do with the particular amplifiers specs. Heres some examples I pulled off manufacturors websites. The first is an alpine amp I am actually installing in a 2007 saleen extreme mustang this week with 2 JL 10W7's ..along with a boatload of other goodies..I will post pics when it is completed.

Alpine PDX-1.1000
RMS Power (at 14.4V THD+N,20Hz-200Hz)
Per channel into 2 ohms : 1000W x 1 (<=1%THD+N)
Per channel into 4 ohms : 1000W x 1 (<=1%THD+N)

Notice the THD as WELL as the power output does not change despite the ohms load.

Ok another amp....

Alpine PDX-2.150
RMS Power (at 14.4V THD+N,20Hz-20kHz)
Per channel into 2 ohms : 150W x 2 (¡Ü1%THD+N)
Per channel into 4 ohms : 150W x 2 (¡Ü1%THD+N)
Brigded 4 ohms: 300W x 1 (¡Ü1% THD+N)

Notice with this alpine amp that the THD never changes nor does the power..it is 150 X 2 in stereo..or 300w X 1 when bridged @ 4ohms (this is how your amps will be running). Note this amp is 2ohm stable....but it only shows specs bridged into 4ohms...that's because as I stated before the 2ohm rating on a 2 channel amp is per channel..the amp is technically running at 2ohms when a 4ohm load is bridged to it.  Ok next amp...

Boss BL1000
Max power: 500W x 2, 2 ohms
RMS power: 210W x 2, 4 ohms
Bridged power: 1000W x 1
THD: 0.01%

OK..notice the difference in the way the specs are done. With Alpine it is not that they are underrated..that would be really poor marketing and self defeating. The key is that alpine amps are rated honestly and at usable power levels.

This Boss 1000w amp is maybe 400w RMS at best going down hill with the wind at it's back. They claim the THD rating is at RMS levels so I guess we have to believe that. next...

Sony XM-D9001GTR
mono subwoofer amplifier
550 watts RMS x 1 at 4 ohms
900 watts RMS x 1 at 2 ohms
2-ohm stable

Here'a a Sony mono amp.....notice they give no THD specs..oh well. Now..the RMS ratings for this amp are not too bad..but notice when the load is cut in half..the power does not double.

So whats it all about? We see one amp that the power stays the same regardless....one amp that doubles when the ohms load is halved..and one that  is rated 200 watts less then double when the load is halved. This is your answer..lol  Hope it doesn't add even more confusion.

Now..for my opinion on using both those amps to one DVC sub...I don't think it is worth the extra work..but if you have time try it out. The deal is this. Running each of those amp at 2ohms (bridging then each to a 4ohm voice coil) will allow each amp to operate at it's highest power level..assuming the power level goes up when bridged...by how much?  As you see it depends on the particular amplifiers specs.

Which will sound better?? I don't know 100% so no harm in trying other then it sounding like total doggy doo after the install.

Now..if You follow my advice and just install the Alpine,,,,since that amp can not handle a 2ohm load bridged to it (which would technically be running the amp at 1ohm..no good) we need to series the coils for a final load of 8ohms. When we bridge that to the amplifier it will technically be running at 4ohms. So you may have less output vs. the 2 amps..but it won't hurt anything..as a matter of fact at 4ohms that amp will be running cooler. If that amp loses half it's power at 4ohm you will be running 80watts to it..not bad...if not 160w. But either way it is honest RMS power and I would assume a cleaner signal. Using both amps I would think the Boss would reach distortion levels much sooner if trying to match the alpines output.

I don't know what effect that will have since i have never tried this myself....has anyone else? post results. But I can't imagine feeding each coil of a DVC a different sine wave (although how different I can not predict) with any great results. In other words it may sound like ass..but can't hurt too much to try it..maybe I am wrong, you decide.

Thanks for typing all that. So if I'm right your saying that there isn't a best ohm to run at it's just what is needed for the application. 

So your saying to bridge the amp to 2 ohm but wiring the speaker for 8 ohms and that makes it 4 ohms right? 

In final I'm going to take your advice and use just use the alpine, but I'm going to try both amps for a few minutes just to mess around with it.

One last question: My dad found the manual for the alpine and it has a 2 amp and 4 amp mode. So what if I put it in 2 amp mode and wired one channel to one side and the other to the other side. That would made it 4 ohms on both sides right? making it 80w to each side.

I feel like I get it but if I'm still wrong you have the right to hit me with a stick.

Not a stick..but maybe a large polo mallot..lol kidding of course. Anyhow this is one of those strange topics that is really simple..but difficult to grasp at first..we have all been there (some of us still are..lol) so no problem,

First off I never said  "bridge the amp to 2 ohms" but you need to look at this whole thing differently. Ok..the amplifer only deals with what we connect to it as a speaker. If it's 2 speakers or 2 voice coils of one DVC or 3 speakers the amp only sees one load..and the value, in ohms, of that load can change ONLY by the way we choose to wire it. If we only are dealing with one single voice coil..we can NEVER change the ohms spec of that speaker..it is what it is. 

Now lets look at stereo wiring to an amp. If we have 2 single voice coil 4ohm speakers...or ONE dvc speaker with 2- 4ohm voice coils, the amp does not know the difference...it just sees a load going to it. Now the rating of the amp (2 ohm stable) when applyed to a stereo amp means we should not connect any load less then 2 ohms to each channel. But,,,,my examples did not show this well, most amplifiers will put out more, generally twice the power when running at 2 ohms, so we will generally try to run amps that way....just what we do, don't question it...lol

OK next...we use in this example your setup..and why we will make certain chioces. What this whole thing is really coming down to is peoples obssesion with running amplifiers at 2ohms...but there is reason...simply put more power...usually. And since your speaker can handle more RMS power then any ONE of those amps you have can deliver...more obssesion with full power.

So we want power right?  As much as these amps can deliver right? At any cost right?  kidding.

Heres the thing. We obsses at how do get this most power to the sub. But theres  a "problem" with using only one of these amps. They are only 2ohm stable. We are STUCK with a DVC sub that has 2-4ohm voice coils. We only have 2 ways to wire both coils.....in series to net a single 8ohm load...or..in parallel to achieve a single 2 ohm load.

So we have this delema....one 2ohm OR one 8ohm sub. Since we have only one sub..we should bridge it to the amp. NOW,,,and this is the important part...the ohms we bridge to the amp (making the 2 channel stereo amp into a one channel mono amp) will technically be running the amp at ONE HALF of what we connect to it...that rule DOES not EVER CHANGE!!!!!..oopss sorry ..yelling lol.

I hate to say ut the following way but it seems to work so I will share....if you bridge an 8ohm load to a stereo amp..the amp "sees" 4ohms...if we bridge a 4 ohm load to a stereo amp..it "sees" 2 ohms..get it now??  it "sees" half..ok?

ok Quiz.....IF we connect a 2ohm subwoofer to a 2ohm stable stereo amp..what is the result??

Answer: The amp will attempt to operate at one ohm....it can't so it cuts out..gets real hot..and eventually it is toast.

So bottom line..if we have a 2ohm stable stereo amp..we would like to run it bridged to a 4ohm sub..just the way we do it. But we don't have a 4ohm sub...DO WE???? NOOOOO . We have a 2ohm OR an 8ohm because some dummy didn't know to buy I one ohm stable amp..or buy a 4ohm sub..kidding sarcasm..ok.

So the options left.....either choose the better of the 2 amps and bridge an 8ohm load to it.....running the amp at 4 ohm...still not bad..just not as much as we could have in a perfect world..or...attempting to run each voice coil seperatly (4 ohms each) and bridge each one to a different 2ohm stable stereo amp.

The BEST thing to do would be to get a one ohm stable amp and run the sub @ 2ohm....or get another indentical sub...wire it the same...we have 2 -8ohm subs now..we parallel those to end up with a SINGLE 4ohm load...we can bridge that to the Alpine amp..or the Boss if the Alpine is so old it quits working (lol) and all the obssesors of 2ohm amp running can sleep tonight....LOL.

Did that help at all? it didn't help me...nah kidding..I do type fast with amazingly few errors (sometimes..) but I don't mind the time to help others if i can..if no one did that for me I'd probably have been a lawyer or stock broker....damn..why did I like this field?

oh sorry..forgot your last question..I don't remember what that "2amp"  "4amp" means but regardless....if you run the amp stereo with one channel to each voice coil @ 4ohms each...it is the same thing as bridging 8ohms to it..remember??? cut in half when bridging..right? 4 OHM STEREO = 8 OHM BRIDGED. 6 of one..half dozen of another.

Try that and mess with the switch..see if you hear an increase..if you do..leave it set that way.

peace

Alright I finially get it. Thank you. As for the 2 amp, 4 amp thing I should have said 2 channel, 4 channel thing.

This is what the manual says. 

4-Amp is for a four speaker system (four 4 or 2-Ohm speakers) In this mode of operation, the INPUT 1 (DIN connection or RCA jacks) accept left and right front outputs. The INPUT 2 (DIN connector or RCA jacks) accepts left and right rear outputs. Specs: 30W x 4 into 4 ohms / 35W x 4 into 2 ohms

2-Amp is for a two-speaker system (two 4-Ohm speakers). In this mode of operation, the INPUT 1 (DIN connector or RCA jacks) only accpets left and right outputs. Specs: 80W x 2 into 4 ohms

This is me typing again. The amp comes with 2 types of speaker wiring connectors. One set to wiring up 4 speakers, and other set for two speakers. You wire the speakers to these connectors then plug them into the amp.

So in the end the 2 amp mode would make it a Independent wiring configuration for the DVC sub or like running two mono amps to two svc subs, which would make it 4 ohms.

I'm glad my dad was into audio stuff back in the day, this is a pretty cool old amp (only 1 scratch on it). Never seen one like this, but then again I'm just now really paying a lot of attention to this stuff.

Also am I still wrong? Sure hope not. Thanks again for the help

Sounds like you are getting  it...sooo  din plugs?   You know..IF that amp still works..it is probably cleaner then 95% of ANY amp built today...IMO no amps sound as good as old Alpines..even the old head units sounded good..and the ear never lies.

Good luck..post how it sounds when you get it crankin..

If the amplifiers can be safely bridged into a 4-ohm load, then there is no problem using a seperate amp for each voice coil.  Just be certain that each amp is receiving the exact same signal or you can set up cancellations inside the motor system and reduce your net output instead of increasing it.  If you use one amp over the other, in general anything from Alpine is about 100X better than anything from Boss.

It seems your Alpine amp if a 4-channel amp?  I do not recommend trying to use it for a subwoofer.  Set it up to power the main speakers in your car, or sell it.

DYohn] wrote:

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t seems your Alpine amp if a 4-channel amp?  I do not recommend trying to use it for a subwoofer.  Set it up to power the main speakers in your car, or sell it.

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The alpine can be either a 2-channel or a 4-channel amp. It's just crazy cool like that. The wiring diagram for the alpine in the manual has two of these amps together, one running the main speakers and one running two subs.

I'm going to try the alpine to the sub as well as the boss and alpine together to the dvc sub just to see what happens. In the end I think I'm going to wire the soundstream TRA960.4 to the front speakers and the sub, then use the alpine in 2 channel mode for the rear speakers. This is just a temporary setup till my friend can afford a sub and amp for it.

Last question, has nothing to do with what components I have just trying to completely understand this. This is that last thing I can think of that is still kinda in the air for me. So if I bridged a 2 channel 4 ohm stereo amp that will make it 2 ohms, then if I wire it up to a 4 ohm svc speaker that  would make it a 2 ohm load right?

Well we decided on what kind of subs to get now. Going with the Polk db212 720 watts rms https://www.polkaudio.com/caraudio/specs/db212/

Now for the amp, in the discription for the subs it says

The soundstream pca1000d 800w rms at 2 ohms  https://www.audio-warehouse.com/web/mdl/PCA1000D/detail.asp

Seems like a good match to me what do yall think?

Sounds fine.. But....."Single Voice Coil 4 Ohm drivers wired in parallel for a net 2-Ohm load, optimum for today's Class D subwoofer amplifiers".

As long as the amp is 1 ohm stable and you are using 2 - 4 ohm drivers. I don't know what they mean by "todays Class D subwoofer amplfiers"..seems like an assumption that all class D amplifiers are 1 ohm stable....I don't know if that's 100% true...but many are and apparently this one must be if they reccomend those ohms values.

Now it seems you are still a bit confused....so this is what I want you to say to yourself over and over until it sinks in...OK there tough guy??

Whatever ohms value you bridge to a STEREO amplifier.....you MUST cut that value in half ....that is what the amp runs at.

Whatever ohms value you connect to one channel of a STEREO amp...is what that channel will run at..same holds true for the other channel of the stereo amp.

In the case of a 4 channel amp...you MUST think of it has TWO - 2 channel amps and apply the above rules.

Whatever ohms you connect to a MONO amp..that is what it wil run at.

I can't simplify it any more then that.

Cool beans???

I have something else to add..at the risk of confusing you even more...lol..but I have enjoyed our conversations so here goes...

I don't know when you are getting the new equipment..but if you plan on working with what you have now...here's my opinion on it.

I agree that the Alpine amp is better suited for running your mids/highs...not only is it a very good sounding clean amplifier (assuming it is in original operating condition)..but..it was most likely built before dedicated subwoofer amplifiers were commonplace like today.

Now this by no means implys that it can't run subs and sound great..it most definatly can..power is power. As stated make sure the inputs are summed..if uncorrelated it will cut power and add distortion, which is way I am fiercly against using the boss amp in tandom with the Alpine..however..and this has not been discussed yet...does that Alpine amp have a built in low pass crossover???

If it does...no problem..if it does not...it will not sound very good on the subs.

One option if this is the case is to buy a seperate electronic crossover...since this is a temporary setup..any will do. They make very inexpensive electronic low pass x-overs..PAC has one....you hook up power...ground and remote...plug in the RCA's..and instant adjustable low pass cross over.

The other option is to use a passive crossover...the drawbacks>>>>  they rob power and are not adjustable..you would need to determine the frequency you wish to start low passing at and the final ohms load to determine the value of the inductor in mfds..to change the frequency you need more inductors...you can get the electronic one for about 15-20 bucks and have some adjusment to boot.

If the deck you are connecting the amp to has preamp sub-outs...ignore this entire post.

Ok...confused even more now??  lol

CORRECTION....!!!

"you would need to determine the frequency you wish to start low passing at and the final ohms load to determine the value of the inductor in mfds.."

I did NOT mean mfds (microfarads..that's for capacitors)..

Inductors (coils) are rated in Henries.....the value needed for subs will be valued in millihenries (mh)...typed before I thunk..but at least I caught it before someone else did and made me look like more of an ass.