The "Real Deal" with 8 ohm drivers

[npdang]

I've seen many people say, "Well I want to use this speaker, but I'm put off by the fact that it's 8 ohms."

Let me explain why it's ok to use an 8 ohm speaker, and why it could actually be better than a 4 or 2 ohm speaker.

First of all, using a higher impedance than what your amp is nominally rated for is always ok. In fact, if your amp is rated for 4 and 2 ohm impedances, typically you will get less power into 8 ohms meaning that your amp will run cooler and more efficiently at higher impedances. It won't hurt your amp, and in fact it's actually much better for your amp's longevity.

Now, you're probably saying how is getting less power out of my amp a good thing? Think of your amp's power reserves as your bank account. Just because you have 100 dollars in your bank account doesn't mean you have to spend it all. Quite the opposite. Wouldn't you rather spend LESS and get MORE? That's exactly what you're doing when you use less power from your amp, and get the same amount of output from a high efficiency speaker.

Remember, most speakers are rated at 2.83V. A 4 ohm speaker rated for 90db spl at 2.83v is really being rated at 2 watts! Whereas an 8 ohm speaker rated for 90db spl at 2.83v is only being rated at 1 watt. You can do the math for yourself, Power = Voltage^2 / resistance. At 2 watts, we can assume that same 8 ohm speaker is actually rated at 93db spl (remember, every doubling of power gives you a theoretical 3db gain in spl). So using that 8 ohm speaker will give you the same amount of output, at half the power required as a 4 ohm speaker. Your amps run cooler and draw less power from your vehicle's charging system, your speakers run cooler, and everyone is happy!

Ok, now let's look at another example of an 8 ohm versus 4 ohm voice coil. Typically, the efficiency of a speaker is given by:

Efficiency = ( B^2 * L^2 ) / ( R * Sd^2 * Mms^2 )

B = magnetic field strength
L = length of wire
R = resistance
Sd = surface area
Mms = mass

So for your 8 ohm voice coil, using the same wire as a 4 ohm voice coil, you would need twice the L or length to get an 8 ohm impedance. That makes sense doesn't it? A longer wire will have more resistance. Now, looking at the formula above, doubling L actually causes your efficiency to rise, even though the impedance also rises. So in this very oversimplified example, raising the impedance actually causes efficiency to go up and lowering the impedance actually causes a loss of efficiency.

What's important to remember is that it's the overall output and efficiency of the speaker that's important, not the impedance. A high impedance, high efficiency driver can get just as loud off a small amount of power as a low impedance, low efficiency driver that sucks a ton of power! Just because you have a 100 watt amp doesn't mean you have to use all 100 watts.... it's all about being efficient.

I also found this excellent post by Dan Wiggins over at carstereos.org:

"I think one thing to consider is that going to a higher impedance voice coil will result in better packing of the voice coil, meaning a higher cross-sectional-area of copper in the flux, for a given mass.

If you take a given driver, and simply swap out voice coils, you end up with more efficiency as you increase the impedance. Take a voice coil, say 2" diameter, 1" winding length, 24AWG 4 layer, and swap it with a 2" diameter, 1" winding length, 27AWG 4 layer, and you double the impedance, but the efficiency also goes up - less mass and better packing density."

It's because the moving mass has dropped, and if desired - because of the thinner wire diameter which packs in tighter - you can put more layers in the voice coil and potentially raise the BL."

[mitchyz250f]

Please help me understand this better. Let us say I have an amp (Orion SX150) that puts out:
-150 watts per channel @ 4-ohm,
-300 watts per channel at 2-ohms
-600 watts bridged @ 4-ohm

Lets say I have sub that has two 8-ohm coils (tempest) or a sub with two 2-ohm coils. What would be the performance difference being with running the amp bridged, non-bridged with the sub in parallel or series? If you could answer this I would be very grateful.

[npdang]

I'm not sure that I understand the question. WIth that amp, and a dual 8 ohm sub you would want to wire the sub in parallel for a 4 ohm nominal load.
For a dual 2 ohm sub, you would want to wire the coils in series for a 4 ohm nominal load. In all instances, you'd want to run your amp bridged into a 4 ohm load.

However, if you were to chose between a sub that was 4 ohm vs. 8 ohm, and the 8 ohm sub was more efficient by ~3db or more... I would choose the 8 ohm sub since you would be pushing your amp alot less harder and achieving same/more output.

[calvinhpk]

ok...for this senario....
i have this amp that can output 4x150w @4ohm

and i have 2 choices of mid same manufacturer, same series, but different impedance,
i) 18W/4531G00 - 4ohm
ii) 18W/8531G00 - 8ohm

which one would give me more control, better sound?
will I lose out on some kick-bass in the 8ohm series?

[10K2HVN]

revelators.. yawn....

you wont hear the difference, just get the 4-ohm because you can.

what are you planning to run with those mids..?

If your planning to run them in the doors, NpDang says the Seas CA18RNX sound better in the doors, freeair.

[calvinhpk]

:D noted. planning to put at the door. In consideration also the 15W version instead of the 18W.
the matter is, i've never listen to the Seas CA18RNX
i've listen to the revelator 4ohm version, and love it.

running with an a/d/s/ P850.2, bridged.

[Tirefryr]

I was down to the Revs or Lotus for In-door app. After doing research, the Lotus/Excel drivers seem to be far better suited. If you have the room for the proper enclosure (and the extra cash), I'd suggest the Revs. Well, then again, that depends on the overall application you are looking for.

[Kramerica]

So does this also mean that an 8 Ohm driver will pull halve as much current than a 4 Ohm driver?

Just trying to figure out the total current draw if I were to add another amplifier.

Thanks

[demon2091tb]

I would think it would, as he said the amp would run cooler and be more efficient with an 8ohm driver over a 4ohm driver at the same sensativity. Say you have a driver with 88db/2.83v at 8ohms, and then you have one that is 88db/2.83v @ 4ohms then its basically 1/2 the power as the formula states, to get the same sensativity of the driver. Because the length of wire for the 8ohm driver is 2x as long as the 4ohm driver, making the 8ohm driver as effecient as the 4ohm driver with 1/2 the power.

Hope i re-itterated that correctly.

The big question i have is, Would cutting down the amount of power that an amp can possibly put out at 4ohms rather than 8ohms have a huge difference on overall spl levels? I probobly already answere my question but besides the obvious benefits of having an amp run cooler and lengthening the life of the amp, how amount actual power differences in question. Like having an amp that does 100rms @ 4ohms, and 50rms or less at 8ohms make a huge impact on the overall sound and possible spl levels?

Hhehe or did i answer that already?

[npdang]

You answered your own question :)

[demon2091tb]

Haha Figures well good deal then, thats the only thing i really wondered about in using an 8ohm driver over a 4ohm driver, as all of the drivers that i will be using in my current build up are 8ohm drivers, except the Tempest and thats a duel 8 :)

The only other thing i worry about is how loud the CA18 and the LPG 26 could be with ~40rms each @ 8ohms, as my amp puts out 82rms @ 4ohms. Somewhat off topic but any ideas Dang? Will they be loud enough to suffice?

[Kramerica]

What I meant to ask was, will an amplifier powering an 8Ohm speaker pull halve the current then if it was powering a 4Ohm speaker?

Say an amp pulls 20 amps to power a 4Ohm speaker.

Will the same amp only need 10 amps to power the 8Ohm speaker?

Thanks, and I will be getting a Dayton Reference tweeter and midrange to replace some CDT's.

[minitruck_freq]

The only other thing i worry about is how loud the CA18 and the LPG 26 could be with ~40rms each @ 8ohms, as my amp puts out 82rms @ 4ohms. Somewhat off topic but any ideas Dang? Will they be loud enough to suffice?


40 watts will be loud with that combo. i have the ca18's and lpg 25nfa's running off an arc 4050. around 50x4 rated power. they get quite loud. even with the gains all the way down.

[npdang]

40 watts will be very loud... however, keep in mind that with music an amp will very rarely be outputting it's max. continuous power.

[minitruck_freq]

i played a 1 khz. tone at my normal listening level...measured ac voltage across + and - terminals... used the formula to convert to wattage blah blah blah. my ca18's are getting just over 17 watts. they are really loud with that little power to them. that myth about needing alot of power is just rediculous. IMO of course.

[pervo]

finally registered thanks npdang!

wanted to bring attention to some issues

an 8 ohm driver compared to a 4 ohm, all things being equal outside of the voice coil windings have these trade offs

the 8 ohm will be slightly thinner and longer
resulting in more turns in the gap.... thus higher bl

making a 4 ohm will have a lower bl and thus needs to compensate

one meathod is to double the layer of voice coils, often facilitating the need for a different voice coil winding... ie flatter wires in order to fit in the same gap. thus bl will most likely not surpas the 8 ohm because even more windings are lost

so dirrect conclusions cannot be drawn form exactly how much inductance differs on the 4 layer vc vs the longer (winding wise) 2 layer

but it is safe to say that inductance will be higher on the 4 layer
also increased mass plays a factor also


this is my understansing at least

[dwyers99]

I HAVE A QUESTION. I AM CURRENTLY RUNNING AN AUDIO ART 100HC THAT CLAIMS STABLE TO 1/2 OHM A CHANNEL

also have 2 oz matrix elite subs dual 4 ohm coils

in this case i had wondered how much difference i would get in the different loads i applied to this amp

i mean 1000 to 1200 watts bridged at 1ohm should give me that bass i need but i am worried it might be overkill both for my front stage and my electrical system not to mention running now at a 2 ohms load bridged is making it considerably hot even at mid listening levels.

i honestly dont think this amp can handle much lower impedence than 1 ohm/channel

however running each channel straight to each sub w/ say a 2ohm load drops the wattage of the amp significantly, nevermind running it to each sub w/ an 8 ohm load

i will try it tonight for kickS (BOTH 2 AND 8 PER CHANNEL)but i would like to hear your feedback on this

I understand what this thread was saying and it makes a great point btw!

[kckon]

So in conclusion does a 2 ohm load have an increase in spl over an 8 ohm speaker?? we know that the amp will run hotter. Also so why make 1 ohm stable amps?

[npdang]

It may or may not. It depends on the speaker. The key is to pay atttention to BOTH the efficiency and the impedance of the speaker.

I was just pointing out that there are tradeoffs in getting a low impedance driver that may lower efficiency if not compensated for. Of course for dual voice coil speakers it maybe different.

[chad]

I think another thing that DIY types overlook is the distance from the driver. Granted sensitivity is rated 1W/1M BUT coming from a home/pro environment we tend to go by experience and dictate a sensitivity number and involuntarily/mentally calculate that to "Listening Position Loudness" Knowing that sound pressure level decreases 6dB for every time you double the distance in an anechoic environment, one can conclude that in a vehicle interior the level perceived with one watt input will be MUCH greater than that it would be in a home or other surrounding. This also proves that the reduction in power going to an 8 ohm driver will be negated by early reflections, cabin gain and lack of appreciable distance from the driver. So not only is it an electrical calculation it’s a matter of the intended application that keeps the SPL of the driver up well within acceptable limits.

Chad

[npdang]

Very true, good post Chad.

[MarkZ]

Nice article, but one *very important* thing I didn't see mentioned was power compression. In the end, the actual resistive component of the 8 ohm and 4 ohm speaker probably wouldn't be terribly far off from each other in most drivers, assuming substantial power levels (a safe assumption, because if we're talking about low volume levels, the point is moot anyway). That theoretical doubling of power you get when you halve the impedance quickly goes away when you factor in amplifier losses and power compression. And that's before you even get into the loudspeaker sensitivity stuff. [For those who don't know, power compression is the phenomenon whereby the resistive component of the driver increases with temperature -- naturally, more power dissipation means higher resistance which, for a voltage amplifier, means a reduction in power dissipation. It's a sort of negative feedback mechanism].

Anyway, you're right to say that the 4 ohm vs 8 ohm issue is all a tradeoff. But you can also look at it from a different perspective: to deliver the same amount of *power* into the 4 ohm speaker requires less voltage. This doesn't matter much until the signal starts to approach the onset of clipping. The problem is that with an 8 ohm driver you'll reach clipping earlier than you will with a 4 ohm driver (again, assuming somewhat similar power dissipation!).

The obvious response to that is: so what? If we've already established that the difference between 4 ohm and 8 ohm output isn't that great because of power compression and amplifier losses, then the difference in clipping shouldn't be all that great either, right? Maybe not. For some musical content, the difference between the peak and average output (usually specified as the "crest factor") can be substantial. So the transients at even moderate volume levels can sometimes reach the rail voltage. That translates into distortion...whether or not it's enough to be perceptible is the question. We can typically tolerate a pretty hefty amount of clipping before it becomes noticable.

Personally, I like to use amplifiers that have enough guts to them to be able to run the 2 or 4 ohm load they claim to be able to run and not have to worry about it. But I also realize that if the speaker I want to use is a higher impedance, like a lot of the 8 ohm stuff that people tout, it's definitely not the end of the world...

[fearlessfly28]

Im looking to get a pair of 6.5" midbass drivers.
Alot of peeps reccomended the Seas W18.
My amp is rated 50w @ 4 ohms.(zapco)

Straight to the point....
Seas W18 will outperform the Seas Performance midbass??

[npdang]

Should be fine with that power, although you will notice a definite improvement in dynamics with more power.

[fearlessfly28]

so u reccomend the Xcels over the Performers?

[npdang]

I don't think you can compare the two. Completely different drivers.

[fearlessfly28]

Hmmm so help a brotha out =)
midbass...dedicated midbass...which one??

[tf1216]

Hey, how long do you have to make your decision?

If I get some free time I will hook up my L18 to my 4.0 and see if I notice a difference in its performance from the 6.0.

I think you might want the 4 ohm driver for your situation.

[avaxis]

i've been reading npdang's article for very long and trying to get it in my head and understand it..and i came up with the figures to explain what npdang is saying.. (i can't quite compute it so i just have to list it down)

speaker A
4 ohm
90dB@2.83v = 2watts and 0.7075A current draw

speaker B
8ohm
90dB@2.83v = 1watts and 0.35375A current draw

amp X
16w @ 4ohm
8w @ 8ohm

every double of power would be +3dB, it can be said that both speaker A & B would play at the same loudness levels if pushed by amp X

speaker A + amp X
2 watt = 90dB
4 watt = 93dB
8 watt = 96dB
16 watt = 99dB

speaker A + amp X
1 watt = 90dB
2 watt = 93dB
4 watt = 96dB
8 watt = 99dB

the difference would be that @ higher impedence, the draw would be at higher voltages but at lower current draw... or in other words..less load..

i hope i am accurate..else do correct me. i was reading npdang's explaination but i couldnt visualize it..until i came up with the figures above.. simply put, its all about matching the impedance and sensitivity of the speaker to the amp. an amp rated for 4ohm would work at 8ohm, and most of the time, with less effort.

[notacop]

Here is a post i made a while back trying to simplify the info in this thread:

A quick summary (hopefully simplified version) of the tech post.

You need to look at the sensitivity ratings of each driver and how they are rated.


If both are rated 1w/1m you need to be 3db higher sensitivity to get the same output with 8 ohm vs 4 ohm

If both are rated 2.83v/1m you need to be the same or higher to get the same (or better) output.


The reasoning is if both speakers are rated with 1watt that is assuming same power to both speakers, since you will be applying half power you will get half output (-3db) so if the speaker is +3db sensitivity or higher you are overcoming that loss of power.

If both are rated with 2.83v that means the 4 ohm speaker was getting 2 watts while the 8ohm speaker was only getting 1 watt, that means that the 4 ohm speaker was given a 3db boost in sensitivity numbers given the same power. So 4ohm-3db = 8ohm given the same power. However since we are only giving half power to the 8 ohm driver our equation is going to be more like 4ohm-3db=8ohm-3db. Obviously the "-3db" part cancels itself out, so as long as sensitivity is the same or better you will get just as loud.


On top of that the way 8ohm drivers are built leads to higher sensitivity ratings so you are more likely to find 8 ohm speakers that can meet the above sensitivity goals.

Hope that helps

[demon2091tb]

Yea so effectively, running an 8ohm load on an amp that is rated at 4ohms, is 1/2 the power of the 4ohm load, but can be just as loud, given the spl/w, if 2 speakers have the same spl lvls' but different imp. the higher imp. or 8ohm load will be run cooler, etc.

Only other reason i would run a 4ohm driver is to just get loads and loads more power out of an amp.

For instance, i'll be running LPG 26's at 8ohms, 82rms @4ohms, diyma 2" at 5ohms, 82rms @ 4ohms, possibly a pair of extremis 6.4's at 4ohm, 160wrms @4ohms.

[Hernan]

I'm running a pair of Auras NS3, 8ohms and (very) low sensitivity. No problem at all powered by 2 x 40W amp with the gains about 75%. They keep the pace with the midbass and Sub powered by a 75 x 4 Eclipse amp. If these drivers work ok, I could guess that any other "popular" 8 ohmer should work too.

[scar19]

I have a 4 channel amp that I'm using to power the tweeters and mid-woofers on my 3Way active system. Currently, 2 channels are connected to the tweets at 4 Ohm and the other 2 channels are for the mid-woofers, also at 4 Ohm...
Let's say I buy a set of 8 Ohm woofers, to exchange for the actual 4 Ohm ones that I have installed. Will the amp work fine? In this case, I would have 2 channels for the tweets at 4 Ohm and the other 2 at 8 Ohm! Is this possible? The amp is rated 4x75W RMS...

[Chaos]

Let's say I buy a set of 8 Ohm woofers, to exchange for the actual 4 Ohm ones that I have installed. Will the amp work fine? In this case, I would have 2 channels for the tweets at 4 Ohm and the other 2 at 8 Ohm! Is this possible?


No problem. Keeping in mind the subject matter of this thread, you should be able to achieve similar output levels (provided that you choose drivers wisely) while putting less demand on your amp.

[03blueSI]

And this is why I think all speakers should be rated at 1w/1m. This way all speakers can easily be compared

[skydeaner]

And this is why I think all speakers should be rated at 1w/1m. This way all speakers can easily be compared


^^true dat

[Pulse-R]

hope you don't hate me for digging this one up...

back on the topic of efficiency...
A colleague of mine insists that efficiency at 1W is meaningless when you apply a lot of power to a speaker, calling it power compression loss.
I understand the concept, but I want to know if it is true, and why....

[MarkZ]

hope you don't hate me for digging this one up...

back on the topic of efficiency...
A colleague of mine insists that efficiency at 1W is meaningless when you apply a lot of power to a speaker, calling it power compression loss.
I understand the concept, but I want to know if it is true, and why....

The resistance of the voice coil increases with increasing temperature. That's true (to some extent) of all conductors. Hell, that's how a light bulb works.

Although I'd hesitate to call power compression a "loss". A loss implies a loss in efficiency, but usually carries the connotation of waste. True, system efficiency decreases with power compression, but it's not being lost in transduction or wasted per se (ie. it's not being converted to heat or something).

[Whiterabbit]

given the fact that many DIY enthusiasts tend to change power output to each driver (like buying a 50 watt amp for the tweeters and a 350 watt amp for midbass drivers), and that the DIY enthusiasts tent to have advanced signal processors that allow for tuning individual gain between each drivers for the purpose of output matching, Ive never really concerned myself much with efficiency.

Dont get me wrong, I always check it and keep it in mind. just in case. But I see it as a qualitative spec rather than quantitative, and until I run or install a passive stage ill never use efficiency as a "deal breaker" when picking drivers.

so I CERTAINLY dont see 8 ohm drivers as a dealbreaker either! if the other performance specs fit my app, its the driver for me!

[erickoh]

Assuming no difference in efficiency, are there any disadvantages in using an 8ohm driver vs a corresponding 4ohmer? If there isnt, then why are 4ohm speakers the "standard" for automotive usage?

[MarkZ]

given the fact that many DIY enthusiasts tend to change power output to each driver (like buying a 50 watt amp for the tweeters and a 350 watt amp for midbass drivers), and that the DIY enthusiasts tent to have advanced signal processors that allow for tuning individual gain between each drivers for the purpose of output matching, Ive never really concerned myself much with efficiency.

Dont get me wrong, I always check it and keep it in mind. just in case. But I see it as a qualitative spec rather than quantitative, and until I run or install a passive stage ill never use efficiency as a "deal breaker" when picking drivers.

so I CERTAINLY dont see 8 ohm drivers as a dealbreaker either! if the other performance specs fit my app, its the driver for me!

Efficiency becomes an important parameter when you start talking about high output applications. The overall output capabilities of the driver are dominated by efficiency. Personally, I think it's a pretty big deal, particularly in midrange and midbass applications where output limitations are often very real (partly due to their unique position of trying to achieve high frequency extension while still trying to move some air).

[MarkZ]

Assuming no difference in efficiency, are there any disadvantages in using an 8ohm driver vs a corresponding 4ohmer? If there isnt, then why are 4ohm speakers the "standard" for automotive usage?

I can't think of any inherent disadvantages. In fact, some amplifiers will like it better, and amplifier design is a bit easier with higher impedance loads in mind.

From what I understand, the original rationale for lower impedance drivers in cars was the reluctance to use power supplies in amplifiers (and head units) that worked on voltages higher than 12v. With only 12v available, the only way to increase power is by lowering the impedance. With aftermarket amps, that problem goes away.

However, another reason to use low impedance drivers comes with the advent of switching amplifiers -- specifically, class D and "class T". The basic operation of this type of amplifier pretty much requires low impedance loads (although they can be designed around higher impedance loads).

[evan]

However, another reason to use low impedance drivers comes with the advent of switching amplifiers -- specifically, class D and "class T". The basic operation of this type of amplifier pretty much requires low impedance loads (although they can be designed around higher impedance loads).Can you elaborate on that?

[npdang]

Switching amplifiers are generally more efficient, and cost effective but tend to maximize their power output into low impedance loads.

[MarkZ]

Their basic design topology makes them more suitable for low impedance loads. The transistors "like" to switch rather than operate within their linear range. Also, in some class D amps, the output filter (which converts the pulsed representation of the signal into a usable audio signal) is supposedly optimized for the targeted impedances of the amp, which tends to be low.

[evan]

Thanks for the clarification.

[erickoh]

Thank you, that concern was at the back of my mind too, since I am using the alpine PDX amp but was considering trying the Seas L18 8ohmer. I guess I'll keep that project on hold for now

[Whiterabbit]

good god why? with 150 rms at your disposal what difference would it make if the driver were 1 ohm or 16 ohms?

[MattinTheCrown]

From what I understand, the original rationale for lower impedance drivers in cars was the reluctance to use power supplies in amplifiers (and head units) that worked on voltages higher than 12v. With only 12v available, the only way to increase power is by lowering the impedance. With aftermarket amps, that problem goes away.
Help me out; I don't understand how that problem goes away. Isn't the problem all about getting high amounts of power out of a 12V source? Regardless of the amp you have, you're still feeding off a 12V source, are you not? What am I missing?

[MarkZ]

You're feeding off a 12v source no matter what, that's correct. But amplifiers convert that 12v into a higher voltage in order to achieve greater amounts of power. This requires a more complex and sizable power supply in the amp, which tends to take up about 1/4 of the total real estate in a typical amplifier (and about half of the heatsink). So it's not exactly trivial to stick a power supply that does that into something small and confined like a head unit, which is why most head units out there were faced with that 12v limit.

[MattinTheCrown]

You're feeding off a 12v source no matter what, that's correct. But amplifiers convert that 12v into a higher voltage in order to achieve greater amounts of power. This requires a more complex and sizable power supply in the amp, which tends to take up about 1/4 of the total real estate in a typical amplifier (and about half of the heatsink). So it's not exactly trivial to stick a power supply that does that into something small and confined like a head unit, which is why most head units out there were faced with that 12v limit.
Oh, I see. I got confused there. My thinking was just that the power supply's ability to convert to the higher voltage was the main factor in difficulty, and therefore, cost. See, even if you're allowing for these monster supplies, you're still saving money and trouble by just building 4ohm speakers (all things being equal, obviously). Or at least that's what I always assumed.

ETA: This, of course, compared to home application where you're working with voltages sufficiently high to make this sort of thing moot.

[chad]

ETA: This, of course, compared to home application where you're working with voltages sufficiently high to make this sort of thing moot.


Yes but you are still faced with the voltage limits of the semiconductors in the amplifiers. Car amps run at nearly the same rail voltages as home amps if not more. Not until you get intop pro amps do you see the mondo rail voltages (like 180V rail to rail) in a Crest Audio big boy 01 series, get out your wallet though.

Chad

[icky4]

I think I have got this figured out, but I want to make sure. I was thinking about buying SEAS Lotus Reference speakers for a 3 way set up. I was going to buy the RW165/1 6.5" for midbass and the RM110 4.5" for midrange. These have slmost the exact same specs at the SEAS Excel W18 and W12. Since I havent been able to find the Lotus midrange, I would be able to use the Excel midrange and midbass instead? Each midbass would be recieving 150W RMS and 75 W RMS to each midrange (4 Ohm rating).

Also, at this power would I be able to use the W22 instead of the W18 given that it will fit in my door?

[GlasSman]

NpDang. If we're talking about a car woofer like an IDQ8 DVC with 4 ohm coils and a sensitivity of 91.5 do the same rules apply since it's not clear wether that speaker was tested at 4 or 8 ohms? My plans for my current setup are limited since I need my lower powered amp, a Reference 500 for my sub. My only options for my midbass is a Rubicon 702 which does 350x2 into 2 ohms, 125x2 into 4 ohms and 75x2 into 8ohms. I've run them at 2 ohms in my previous car but I just don't want THAT much power up front and the extra strain on the amp and electrical system.

[aneonrider]

Although 7 weeks old... I'll chime in that 95% of the DVC subwoofers have their t/s parameters measured when the coils are in series. If they don't, it will be noted.

[Whiterabbit]

and there are also references to methodologies of damping dvc subwoofers by powering only one coil, then "tuning" your Q by either leaving the second coil open, shorting it, or installing a resistor in there.

could be a fun test

[1stOnRaceDay]

Another question. I was looking at the RS180 4 and 8 Ohm power handling capabilities. Both have 60W RMS/90 Max. Does that mean that if I use an amp rated at 100W at 4Ohms, that I could toast the 4 Ohm version, but would be fine with the 8 since the amp will only deliver 50W to an 8 Ohm load. By the way, the 3 Ohm rule holds here 91 vs 88 dB at 2.83/1m.

[ryan s]

kind of OT but i changed my dual 4 ohm sub from parallel to series yesterday and polyfilled the box. it sounds completely different and im loving it, thanks to this thread :D

[a$$hole]

kind of OT but i changed my dual 4 ohm sub from parallel to series yesterday and polyfilled the box. it sounds completely different and im loving it, thanks to this thread :D

Glad to hear it !! :)

NP Dang, will be too !!:)

:cool: :cool: :cool:

[mitchyz250f]

Sorry, to bring this up from the dead and I am sure it has been answered 100 times.

I have an Orion 2150GX; it puts out 150 watts per channel into 4 ohms, 300 watts per channel into 2 ohms. I guess it puts out 75 watts per channel into 8 ohms.

I have dual 4 ohm VC speakers, IDQ8's. The IDQ8's could be setup as 2 ohm or eight ohm speakers. I would be getting 300 watts per channel at 2 ohms and 75 watts per channel at 8 ohms. Sounds like a huge difference to me. How would the speakers sound different in each setup?

These are midbasses (100-250hz) and my primary interest are the dynamics (headroom).

BTW, my car has been in pieces since dec. 19. 2007. I hope to have it together in the next 3 weeks.

[notacop]

Sorry, to bring this up from the dead and I am sure it has been answered 100 times.

I have an Orion 2150GX; it puts out 150 watts per channel into 4 ohms, 300 watts per channel into 2 ohms. I guess it puts out 75 watts per channel into 8 ohms.

I have dual 4 ohm VC speakers, IDQ8's. The IDQ8's could be setup as 2 ohm or eight ohm speakers. I would be getting 300 watts per channel at 2 ohms and 75 watts per channel at 8 ohms. Sounds like a huge difference to me. How would the speakers sound different in each setup?

These are midbasses (100-250hz) and my primary interest are the dynamics (headroom).

BTW, my car has been in pieces since dec. 19. 2007. I hope to have it together in the next 3 weeks.



This thread is meant to apply comparing a 4 ohm driver with an 8 ohm driver. In application where you have multiple wiring options for the same driver (like your DVC sub) wire it to get the most power from the amp, in your case 2 ohms. Since efficiency is not drastically different when you wire it differently, since it is still using the same coils, just in a different configuration.

[mitchyz250f]

I understand what you are saying and it makes sense. But what about this statement;

"kind of OT but i changed my dual 4 ohm sub from parallel to series yesterday and polyfilled the box. it sounds completely different and im loving it, thanks to this thread"

I have read the same thing on 'diyaudio' about subs.

[BEAVER]

I'm gonna have to side with notacop on this one.

I believe the original purpose of this thread was to compare single voice coil drivers and educate the masses on the possible benefit of 8ohm drivers vs. 4ohm drivers... I don't believe it was intended to have people re-wiring their DVC subs to get less power to them. This is just silly, in my estimation. Please correct me if I'm wrong.

[jnelly]

Hey, I don't post much but have a question. I am running a JL 10w1-8 off of a MTX Thunder 502 and to get any noticeable output I have to crank the gains all the way up. The sub's Rms rating is 125 watts. So I figure at an 8 ohm load the amp is pushing out around 180 watts. I guess my question is why the gains have to be maxed out for for any good amount of output.

[bdubs767]

The gain is not a volume nob! you are more than likely sending that sub a very distorted signal at higher volumes. Id be very careful if I were you

that was not his question.....


To the original poster it most likely has to do with weak out voltage of your head unit. But there are many different variables that could be effecting why you are not getting what you consider to be a good volume.

[MarkZ]

The gain is not a volume nob! you are more than likely sending that sub a very distorted signal at higher volumes. Id be very careful if I were you

The gain IS a volume knob. There's no reason to think that his sub is receiving a distorted signal.

[jnelly]

I set the gains by putting the volume to 3/4 of the way up on the HU and then slowly turning the gain up until it hear distortion. The head unit I am using is a Clarion Hx-D10 w/ the processor. It has 4v pre-outs. I just don't get any noticeable output unless the gains are maxed out. Any help is appreciated.

[bdubs767]

I set the gains by putting the volume to 3/4 of the way up on the HU and then slowly turning the gain up until it hear distortion. The head unit I am using is a Clarion Hx-D10 w/ the processor. It has 4v pre-outs. I just don't get any noticeable output unless the gains are maxed out. Any help is appreciated.


Thats prob max 4 volts out. I doubt it puts any thing more then 2 volts out. A line driver would not hurt.

[a$$hole]

Ratio = input-to-output.

Going in reverse order turn gain down on amp or amps, next piece in the line and finally head unit.

Now going in forward turn volume up on head unit to 3/4 of full, turn gain up on amp [you are looking to get the headunit at a clipping point at the same time the amp clips ].

[60ndown]

Yes but you are still faced with the voltage limits of the semiconductors in the amplifiers. Car amps run at nearly the same rail voltages as home amps if not more. Not until you get intop pro amps do you see the mondo rail voltages (like 180V rail to rail) in a Crest Audio big boy 01 series, get out your wallet though.

Chad

i modded my ipod internal amp to that ^.

[AAAAAAA]

I had fun today comparing a 4ohm tweeter (canton) to an 8ohm(tang band) and there was no diffrence that I could hear volume wise at most frequencies.

High efficiency 8ohms rules! ;)

[60ndown]

agreed,
my new midrange
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-020

[AAAAAAA]

Here is mine, not high efficiency but not bad.
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-842

[GlasSman]

agreed,
my new midrange
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-020

Slap a pair of those in the kicks....call it a day.

[br85]

I don't really see why anyone would think moving to 8 ohm drivers would be under most circumstances. Let's be realistic, most of us are constantly buying and selling gear anyway, surely we would just do our best to make amps match our speaker setup?

For example, I have recently purchased a pair of SLS 8". Previously I was running my 4 ohm midbass off 150 Watts per side. I'll be happy with 2 X 75W @ 4 ohms for a little while, but pretty soon I'm going to get another amp, bridge the two amps up and have 300 Watts per side at 8 ohms anyway.

Given how power is not really as expensive as it used to be, I only look at effeciency ratings to question whether the quoted Xmax can be reached with stated RMS power.

For example, if I saw this on an 8" driver (I haven't, but one day i'm sure i will):

Sensitivity: 79db
RMS power: 150W
XMAX: 10mm one way

I would call bs on ever seeing the driver stroke that much without causing a vcv (voice coil volcano).

If I trust the specs, I won't look at sensitivity or effeciency. I'll look at cone size, fs, rms power handling, and Xmax to determine what role it will play in a given setup and what amp to get for it.

[a$$hole]

Given how power is not really as expensive as it used to be, I only look at effeciency ratings to question whether the quoted Xmax can be reached with stated RMS power.



variables

IB = less power handling

small box = less low end more power handling [ SPL ]

efficiency = how loud it gets with available power

[br85]

variables

IB = less power handling

small box = less low end more power handling [ SPL ]

efficiency = how loud it gets with available power

Good point.

[bikinpunk]

If I trust the specs, I won't look at sensitivity or effeciency. I'll look at cone size, fs, rms power handling, and Xmax to determine what role it will play in a given setup and what amp to get for it.

What would be the purpose of the driver?

If it's midbass in a door I'm looking at Sd, Fs and qts. Not worried much about xmax.

[a$$hole]

What would be the purpose of the driver?

If it's midbass in a door I'm looking at Sd, Fs and qts. Not worried much about xmax.


Fs: 45 Hz
Qts: ..38
Power handling: 70 watts RMS
Frequency range: 45-5,000 Hz

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=296-603

[cheesehead]

agreed,
my new midrange
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-020

Did you go with this for midrange? Are you using it for midrange only?

[86mr2]

Waaay off topic for the thread. Could you start a new one?