Can I replace the horrible Sony front left and front right and additionally center channel speakers from a "5.1 system in a box" with the following?
Three Infinity 63.5i (car audio) drivers, specs: 6.5" mid w/tweeter and supertweeter built-in, 4ohm, 75Wrms, 225Wpeak, sensitivity of 90dB, and each include a proper (4 ohm impedance) crossover.
This Sony amp's specifications document states that it drives as following:
* In stereo mode, 84Wrms+84Wrms into 3 ohms (the front left and front right speakers) plus the silly 1.5 ohm 285W sub.
* In surround mode, the wattages go up BUT so does the THD from 1% in stereo mode to 10% however everything remains at 3 ohm. 143Wrms to each 3 ohm speaker (oooooooh). The sub stays the same.
So, the configuration would become three 4 ohm speakers (front left/right and center) plus two 3 ohm rear speakers plus the silly 1.5 ohm subwoofer as seen by the amplifier.
I'd build small sealed and fully stuffed enclosures for the Infinity's. Probably 7"x7"x7" cubes with full stuffing to fully kill the rear wave. The major complaint is that the vocals sound so muddy as to be unintelligible. And, I AGREE! I'd like to show them some good drivers, even with the amp being the weak link in the chain due to its very poor THD.
A kind of fun woodworking project to help them out.
And, here is the main question (sorry for the post's length):
I know what driving lower ohm speakers/drivers will do to an amp (heat it up a ton). But, does driving higher ohm speakers/drivers than an amp is rated for just cut the wattage down per the math and do no harm to the amp and speaker/driver?
The difference is only 3 ohm speakers versus 4 ohm speakers. I do not know how this amp is wired and I have to believe it is a full Class D amp due to its extremely small size.
Thanks!
Three Infinity 63.5i (car audio) drivers, specs: 6.5" mid w/tweeter and supertweeter built-in, 4ohm, 75Wrms, 225Wpeak, sensitivity of 90dB, and each include a proper (4 ohm impedance) crossover.
This Sony amp's specifications document states that it drives as following:
* In stereo mode, 84Wrms+84Wrms into 3 ohms (the front left and front right speakers) plus the silly 1.5 ohm 285W sub.
* In surround mode, the wattages go up BUT so does the THD from 1% in stereo mode to 10% however everything remains at 3 ohm. 143Wrms to each 3 ohm speaker (oooooooh). The sub stays the same.
So, the configuration would become three 4 ohm speakers (front left/right and center) plus two 3 ohm rear speakers plus the silly 1.5 ohm subwoofer as seen by the amplifier.
I'd build small sealed and fully stuffed enclosures for the Infinity's. Probably 7"x7"x7" cubes with full stuffing to fully kill the rear wave. The major complaint is that the vocals sound so muddy as to be unintelligible. And, I AGREE! I'd like to show them some good drivers, even with the amp being the weak link in the chain due to its very poor THD.
A kind of fun woodworking project to help them out.
And, here is the main question (sorry for the post's length):
I know what driving lower ohm speakers/drivers will do to an amp (heat it up a ton). But, does driving higher ohm speakers/drivers than an amp is rated for just cut the wattage down per the math and do no harm to the amp and speaker/driver?
The difference is only 3 ohm speakers versus 4 ohm speakers. I do not know how this amp is wired and I have to believe it is a full Class D amp due to its extremely small size.
Thanks!
my 'precision audio' brain tells me that the higher the load , the better is
the THD figure . The more complex the load , the more the amplifier will fatigue to keep up with it .
So a 4 Ω design at home requires a beefy amplifier with at least 2 paralleled
output devices for major current handling , but this alone won't help to minimize THD , it's the whole circuit of the amp , specially the supply -transformer, rectifier , levelling capacitors .
So , halving of the load ( from the classic 8 Ω ) produces double distortion .
Class D amplifiers in cheap Av equipment are NO GOOD for music .
Also , cubic boxes are NO GOOD for cabinets .
Then , Car speakers ( probably ...plastic ones ) are NO GOOD for domestic enjoinment of the music
🙂
the THD figure . The more complex the load , the more the amplifier will fatigue to keep up with it .
So a 4 Ω design at home requires a beefy amplifier with at least 2 paralleled
output devices for major current handling , but this alone won't help to minimize THD , it's the whole circuit of the amp , specially the supply -transformer, rectifier , levelling capacitors .
So , halving of the load ( from the classic 8 Ω ) produces double distortion .
Class D amplifiers in cheap Av equipment are NO GOOD for music .
Also , cubic boxes are NO GOOD for cabinets .
Then , Car speakers ( probably ...plastic ones ) are NO GOOD for domestic enjoinment of the music
🙂
Yes, if the amp were delivering 3 volts RMS into 3 ohm then that is 3 watts RMS. A current of 1 amp flows. If the impedance goes to 4 ohm then power dissipated in the load is only 2.25 watts and the current goes down to 0.75 amps.
So the answer is that the amp has an easier time of things as the load impedance increases.
Class D amps aren't my thing but as was pointed out to me in an MP3 player thread, the load can sometimes form part of the output filter. But 3 to 4 ohms and there is no issue whatsover. Also the impedance of any speaker will vary wildly with frequency. It may be 3 ohms at some point, it may go lower than 3 and will certainly be above 3 for much of the frequency range.
So imo no problemo 😀
Hi,
There is no problem with your plan at all, though I often find
for car two ways the tweeter level is higher than it should be.
Sealed and stuffed is the way to go with car speakers.
They won't be hifi balanced, but if your lucky the system
may have some built in active EQ working in your favour.
rgds, sreten.
The 1.5 ohm sub is not that silly, it allows it to receive
double the power of the 3 ohm satellites from the same
voltage rails as the satellites, a fairly typical practise.
There is no problem with your plan at all, though I often find
for car two ways the tweeter level is higher than it should be.
Sealed and stuffed is the way to go with car speakers.
They won't be hifi balanced, but if your lucky the system
may have some built in active EQ working in your favour.
rgds, sreten.
The 1.5 ohm sub is not that silly, it allows it to receive
double the power of the 3 ohm satellites from the same
voltage rails as the satellites, a fairly typical practise.
Haha. This is no 'precision audio brained' project by any stretch of the imagination (I save those fun ones for myself!). I'm just replacing three extremely thin plastic enclosured Sony 3 ohm speakers (2-5/8" mids with 1" tweeters and expected to go as low to meet the subwoofer!) with some very good Infinity 4 ohm ones and in properly sturdy enclosures. The Kappa Series 63.5i's are not crummy plastic car speakers but cerametallic's with titanium dome tweeters and then the EMIT supertweeters.
The Infinity's worked great but I didn't really like the sound of the cerametallic cone so I moved to Polk SR6500's with their aerated polypropylene cones (very natural sounding) and separately mountable ring radiator tweeters. The cost of the SR6500 "kit" was worth every single dollar. They no longer make it due to cost and not enough people wanting to spend that much during these economic times. BUT, I got some extra drivers shipped to me from their tech guys before everything was gone so if I blow one, I can replace it.
I agree about higher impedances (for better damping/cone control as is my understanding) and Class D amps aren't great but are getting much better. I almost bought some Class D amps (for home use) by Hypex.nl 7 or 8 years back. But still, for example and even in a CAR, my SR6500's are powered by a great JL Audio Class A/B amp that can put out 150Wrms into each 4 ohm channel. And each Polk midrange/tweeter/xover channel (set) is rated for 125Wrms. Perfectly amp-overdone in my opinion with those 25 extra watts of headroom; no clipping at any time. And, they never, ever see anything below 160Hz while in their sealed enlcosures. Those 6.5" cones CANNOT do much of anything below 160Hz so the low frequency amp power is not wasted and the cone is not "excursioning" wildly to try and reproduce <160Hz frequencies that it cannot do anyway!
The cubic box should be A-OK as this is a completely sealed and completely stuffed box (stuffed all the way to the driver's basket) and with an 80%cotton/20%poly blend that I think is awesome for midrange sealed enclosures in order to eliminate the rear wave entirely. It is many times more thick that 100% poly and absorbs acoustical energy fantastically. The internal box should pretty much appear like an infinite baffle to the rear of the cone. I am familiar with standing waves and why angled enclosures or using the Golden Ratio dimensions is better (going from memory here: is it 0.618:1.0:1.618).
I had to change my username and I chose PrecisionAudio (because AccurateAudio was already taken) and I HATE MP3's! They are taking audio quality back to Type I iron-oxide cassette tapes with their total lack of accurate/quality high end frequencies! ALL of my CD's and reel-to-reel tapes were 100% accurately sampled with the best ADC's and stored in WAV lossless format. So, to the kiddies who can stand MP3's.....I actually feel bad for them!
Thanks for the information/post. I appreciate it.
THANKS! I was hoping for the statement of "So the answer is that the amp has an easier time of things as the load impedance increases." that you said!
Much appreciated. 😀
Oh that's good news
'cos sometimes I fell a loser , an incompetent
A wasted life !
Thank you !!!
Yep, it sure is great news! Thanks for the support.
But, do not feel like a loser, an incompetent, or one having a wasted life. I've turned my life in a different direction many times with ever increasing success.
I wish you the best. And, cheers with regard to the beverage consumption you showed in your post. Looks like Guinness to me. Very tasty.
It must be water ...I've already drank almost 1 liter since I woke up
Florence is always one of the hottest towns in Italy
-and I was a little depressed from my 3 way flash experiment of yesterday-
which caused me a mental trauma 😛
Then it turned up to a 2 way , with a paper cone tweeter and a 6 "
waveguide - simplicity pays 😉
Florence is always one of the hottest towns in Italy
-and I was a little depressed from my 3 way flash experiment of yesterday-
which caused me a mental trauma 😛
Then it turned up to a 2 way , with a paper cone tweeter and a 6 "
waveguide - simplicity pays 😉
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