power needed for 8 ohm car mids?

[Lil Poot 5,000+ posts]

i have a pair of single voice 8 ohm coil css sdx7 mids, driving them right now with my usa 4050, active but its not enough amp for them.

are there any specs i can look for to see if a given amp will be better suited for 8 ohm loads? two of the amp i've been considering is the alpine pdx4.150 and the zuki eleet. i noticed the alpine drives the same amount of power at 2 and 4 ohms, does it do the same at 8 ohms also?

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[Linkz 10+ year member]

I would guess buy an amp that will do double the output you need @4ohm. I donth think there would be much difference. You could alway buy another pair and run it at 4ohm that way.//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[Lothar34 10+ year member]

Try to avoid one that says it puts out the same rated power at 2ohm and 4ohm. It will probably NOT put out the same power at 8ohm because of the power supply design.

 

[FoxPro5 5,000+ posts]

Try to avoid one that says it puts out the same rated power at 2ohm and 4ohm. It will probably NOT put out the same power at 8ohm because of the power supply design.

I would and the amp should love it.

Typically, the impedance difference is made up for improved efficiency as you go from 4 to 8 ohm. What is the rated efficiency of the speaker and by which standard is it measured?

Bottom line is it's not that important when it comes to buying an amp. The fact that the driver is 8 ohms should NOT persuade you from buying the amp that has the specs that are most important to you (size, crossovers, layout, etc).

If you had 4 ohm drivers and I switched them for their 8 ohm brother without you knowing, I really doubt you'd be able to tell.....besides maybe going 2 clicks higher on the HU which you may or may not realize.

 

[Lothar34 10+ year member]

I would and the amp should love it.
Typically, the impedance difference is made up for improved efficiency as you go from 4 to 8 ohm. What is the rated efficiency of the speaker and by which standard is it measured?

Bottom line is it's not that important when it comes to buying an amp. The fact that the driver is 8 ohms should NOT persuade you from buying the amp that has the specs that are most important to you (size, crossovers, layout, etc).

If you had 4 ohm drivers and I switched them for their 8 ohm brother without you knowing, I really doubt you'd be able to tell.....besides maybe going 2 clicks higher on the HU which you may or may not realize.

I should have prefaced my post with "all else being equal."

Efficiency differences aside, if he's trying to match the RMS output of his amp with the RMS input of his speakers (which is how I understood it) then my advice is still correct.

 

[helotaxi 5,000+ posts]

RMS numbers are only numbers. They're really not that important.

 

[thehardknoxlife 10+ year member]

RMS numbers are only numbers. They're really not that important.

X alot. I saw a couple of Xenon amps on the board recently. The multi channels make their rated power @ 8 ohms IIRC, and they were cheap.....

 

[Haunz 10+ year member]

Typically, the impedance difference is made up for improved efficiency as you go from 4 to 8 ohm.

Wat ?

you might want to rethink that one..

OP I'd look for a relativley high power 4ch amp and bridge it...

I also suspect the Alpine amp you are looking at is similar to it's JL counterpart, in that it can switch between powersupply rails to deliver the same output into 2 or 4ohms... that means that you should be able to get full power (300X2) out of the amp if it's bridged at 8ohms.. I'd call tech support to varify..

 

[thehardknoxlife 10+ year member]

Wat ?
you might want to rethink that one..

OP I'd look for a relativley high power 4ch amp and bridge it...

I also suspect the Alpine amp you are looking at is similar to it's JL counterpart, in that it can switch between powersupply rails to deliver the same output into 2 or 4ohms... that means that you should be able to get full power (300X2) out of the amp if it's bridged at 8ohms.. I'd call tech support to varify..

Actually he's right. This is a good read on 8ohm drivers. I suggest you read that and then come back to apologize for saying things you really have no knowledge of, oh and your assumption on the amp is incorrect as well. I'll let you figure that one out on your own. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[tcguy85 10+ year member]

8ohm mids are generally more efficient. meaning they won't need as much power. look at the sensitivity spec.

but i do agree with helotaxi. rms numbers are not important. just get as much clean power as you can afford and can fit in the install.

 

[Haunz 10+ year member]

Actually he's right. This is a good read on 8ohm drivers. I suggest you read that and then come back to apologize for saying things you really have no knowledge of, oh and your assumption on the amp is incorrect as well. I'll let you figure that one out on your own. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

You are an idiot..

First of all 'sensitivity' ratings are basically meaningless.. SPL @ 1khz tells little about a driver's overall performance... and typically higher 'sensitivity' comes at the cost of low end extention...

Secondly impedance has little to do with actual 1w/1m spl.. assuming a 4layer wrap that same driver could have it's windings wired for 2ohms... but I suppose you think that would cut sensitivity by 6db... //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

I suggest you STFU and then come back to lick my left nutt for saying things you really have no knoledge of.... //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

But please, tell me more about the PDX amps since my assumptions are all wrong ? Perhaps the amp uses variable pulse width modulation in the PSU to change rail voltage ??? (if you know what that is)

 

[helotaxi 5,000+ posts]

First of all 'sensitivity' ratings are basically meaningless.. SPL @ 1khz tells little about a driver's overall performance... and typically higher 'sensitivity' comes at the cost of low end extention...

Well since we're talking about mids, not subs here, it's huge;y relevant and a very good indicator of how efficient the driver is...

Secondly impedance has little to do with actual 1w/1m spl.. assuming a 4layer wrap that same driver could have it's windings wired for 2ohms... but I suppose you think that would cut sensitivity by 6db... //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

Depends on the spec. Most brands don't advertise 1w/1m they advertise 2.83v/1m. As such impedance is very important since 2.83v is 1w @ 8ohms, 2 @ 4 ohms and 4 @ 2 ohms. This is exactly how many brands make their mids appear on paper to more efficient than they are. If the actual spec is advertised 1w/1m then impedance doesn't matter, so your rewiring of a 4 layer coil would be correct but when we start talking about the typical spec...

You are an idiot..
I suggest you STFU and then come back to lick my left nutt for saying things you really have no knoledge of....

//content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif
Honestly, you're the one putting your foot in it here. A degree doesn't make you right when you misapply the learning...

The Alpine advertises making its correct power @ 4-8 ohm when bridged.

 

[Haunz 10+ year member]

Usable bandwidth and extention on a mid is certainly important.. and I don't care about 2.83V... everyone with a clue knows that 'sensitivity' ratings are commonly bogus... I look at eta naught...

The only thing worth while in that link posted about sensitivity vs impedance is what Dan Wiggins said about packing round windings together tighter with a smaller conductor...

 

[Haunz 10+ year member]

If the actual spec is advertised 1w/1m then impedance doesn't matter.
The Alpine advertises making its correct power @ 4-8 ohm when bridged.

Two winning sentences... The OP and I both thank you.. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[FoxPro5 5,000+ posts]

As far as PDX and higher impedance is concerned, my 1.600 drives an 8 ohm 88 dB (2.83w/1m) sub almost exactly the same as it drives a 4 ohm 92 dB (2.83/1m)....as in, if I swap one for the other in the same enclosure, the output is the same. In this case, the 4 ohm driver is more sensitive but other factors seem to equalize the output curve.

Point is, buy the amp you want and don't worry about it unless you try and drive a load outside it's recommended range.....the higher you go up, the more the amp will like it.