Crossover help

[bs1777]

Please help. I have a 8 ohm amp with 2 channels. I recently bought some 4 ohm speakers to go with it. I want to cross it over but i dont want to spend much money. I found a good deal on a crossover that is 4 ohms. Being that me amp is 8 ohms, is it safe to connects the two, and if so what will be the side affects? My amp is a sony and if hooked up to different impedance speaker, after volume 20 it goes into protect.

-Thanks

 

[vdi_nenna]

If your amp can handle no less than 8 Ohms, don't use speakers that are 4 Ohm.
You can damage the amp.

Your choices are to get an amp that can handle 4 Ohms or less or work with 8 ohm drivers and crossovers. The speaker drivers are what's dictating the impedance, not the crossover. The crossover is designed around the impedance of the drivers.

For example, in an 8 ohm, 2-way design that crosses over at 2000Hz, it will have different value crossover components (capacitors, resistors and coils) than a 4 ohm design.

Check out this calculator to get an idea of what's happening:

Passive Crossover Design Equations Formulas Calculator - Two Way First Order Network Butterworth

 

[Cal Weldon]

My amp is a sony and if hooked up to different impedance speaker, after volume 20 it goes into protect.

Your sentence says everything.

Can you buy two more of those speakers and wire them in series?

 

[bs1777]

So if i hook up my 4 ohm crossover will i be good, or will i wreak the amp?

 

[PeteMcK]

re:'will i wreak the amp? ' - highly likely,
What do think the crossover will do?... Crossovers need to be designed for specific speakers, a 'a good deal on a crossover that is 4 ohms' is a waste of time, get your money back and buy speakers that match your amp...

 

[Pano]

Strange that the Sony amp will not do 4 ohms, but going into protect mode tells you it can't.

Can you give more details in your speakers and the crossover you found? And what are your goals, apart from low costs?

 

[bs1777]

re:'will i wreak the amp? ' - highly likely,
What do think the crossover will do?... Crossovers need to be designed for specific speakers, a 'a good deal on a crossover that is 4 ohms' is a waste of time, get your money back and buy speakers that match your amp...

-The crossover is electronic. It is a Audiopipe CRX-303. If you could tell me a little more about this crossover, that would be great. It says to be 4 ohms but will it still work with me amp? A pay very little for the woofers and i really like them and want to keep them. Thanks.

 

[vdi_nenna]

Your crossover is passive, high-level. It goes after the amp and before the speakers.
Is your speaker a three-way low, mid and high frequency drivers?

The crossover is not your problem. The amp is your problem. It can't handle the current of a low impedance driver(s). It over heats and goes into protection.


You need an amp like this one-

AudioSource AMP100 2-Ch Source Switching Power Amplifier | Parts-Express.com

It can handle 8 and 4 Ohms speakers...for the price of little more than 2 crossovers.

 

[bs1777]

I like my current amp but thanks for the reccommend. Is there any sugestions for a good cheap crossover that would work for my amp? And is there a way to make that crossover work?

 

[bs1777]

So would my 4 ohm crossover work with my amp? And i only need a 2 way crossover after some recent testing.

-Thanks

 

[Cal Weldon]

You're not listening to what people are telling you. The problem is not the crossover. It is not 4 ohms, it is designed for 4 ohm speakers, that's what the rating of 4 ohms is. Also it is an off the shelf type so while it may work, it isn't designed for your specific speakers so it's not ideal.

What you need is an 8 ohm load to your amp so if you get two more of these speakers, you can wire them in series to get that 8 ohms. Otherwise you will slowly wear out your amp if you continue the way you are.

I also can't believe that your Sony amp can't handle 4 ohms. What model is it?

 

[giralfino]

It seems that I should repeat what vdi_nenna and Cal Weldon already told you.

Your problem is not the crossover, but the amp, or in other words, you bought non suitable drivers for your amp.
A low impedance driver draws more current from the amp than a high one. If your amp is not able to give the current the drivers need you have only 2 options: change the amp or change the drivers.

The only other way to convert a 4 Ohm (mid-bass) driver to 8 Ohm is to add a 4 Ohm resistor in series, but this is IMHO a very stupid thing to do.

Ralf

P.S. Even if I'm not an expert to me it seems strange that a Sony amp cannot handle 4 Ohm drivers. Are you sure it is not faulty in some way?

 

[bs1777]

Thanks for all the great feedback. I really appreaciate it since im new to this stuff. The amp is a sony MHC-EC78P. It says use 8 ohms.

-Thanks

 

[bs1777]

I also have another question. All my speakers would work at 4 ohm since the tweeter and the woofer are near 4 ohms. So would the crossover work then? I know that if i have 8 ohm drivers on a 4 ohm crossover it would change the frequency and not work, but if all my drivers on the crossover are 4 ohms will it work eventhough the amp is 8 ohm. I know i prpbabally been repetative but im just trying to learn all i can.

-Thanks

 

[PeteMcK]

uh-oh, a 'mini' hi-fi system... too small to drive anything other than what comes with it.
at this point, if you want to stick with your additional woofers, I'd say the best way forward is a subwoofer plate amp, but that'll require some small amount of technical knowledge to wire up....
If you are serious about music & like it loud, however, you need a bigger amp & speakers....

 

[bs1777]

The thing is this amp pushes out 380 watts rms. It slams. I used to have 2 10" on it until it got wreaked in a flood. I am currently builing my own system and had these speakers already. I do have two 8 ohm crossovers but it doesnt work with my woofers. All i need to do is run my 4 ohm tweeter and my 4 ohm woofer from and 8 ohm amp while sucessfully crossing it over. I would reallly like a yes or no answer and any sugestions as i previously stated.

-Thanks

 

[PeteMcK]

re:'380 watts rms' - don't beleive the marketing hype, it's probably got a couple of 15W RMS chip amps inside...
re:'I would reallly like a yes or no answer'... despite the fact there isn't one?

 

[nipper575]

I also have another question. All my speakers would work at 4 ohm since the tweeter and the woofer are near 4 ohms. So would the crossover work then? I know that if i have 8 ohm drivers on a 4 ohm crossover it would change the frequency and not work, but if all my drivers on the crossover are 4 ohms will it work eventhough the amp is 8 ohm. I know i prpbabally been repetative but im just trying to learn all i can.

-Thanks

The simple answer is that you do not want to use 4 ohm speakers with an amp that is only capable of handling an 8 ohm load, you will damage your amplifier.

 

[Cal Weldon]

bs1777, I think it's time to give us more information about your system. It's the only way we can really help you. Post pics too, OK?

 

[bs1777]

The first picture is my current crossover. I used this with my old setup. it is 8 ohms and works with only my tweeter, but not my woofer(which is 4 ohms). i could keep this crossover but i want to use my woofer. The crossovers i want are 4 ohm, 2 way. It would take the main channel on my amp and convert it to woofer and tweeter. The tweeter measures about 6 ohms which is the minimum on my amp, and works with the old crossover(made in 1980). It would also work with the crossovers i want. If all fails i can sell those 4 ohm woofers and get the dual 4 ohm version and use old crossovers. But thats not what i want to do.

The second picture is my amp. Which is around 100 watts per channel RMS. I really like this amp due to the iPod docking and features.

The third picture is just what it says on the back about use 8 ohms. And PLEASE dont tell me about it saying low frequency cause i have tested it and it full range.