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Whiterabbit said:
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).
 

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erickoh said:
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).
 

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MarkZ said:
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?
 

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Discussion Starter #44
Switching amplifiers are generally more efficient, and cost effective but tend to maximize their power output into low impedance loads.
 

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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.
 

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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
 

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MarkZ said:
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?
 

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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.
 

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MarkZ said:
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.
 

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MattinTheCrown said:
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
 

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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?
 

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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.
 

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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.
 

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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
 

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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.
 

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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
 

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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.
 
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