choosing an amp for my stereo speakers

Thread Starter

TITANB324

Joined May 6, 2017
5
I got 2(actually 4) stereo speakers, 2 physical ones with the upper part being a mid-high range speaker and the lower one is a subwoofer. each physical speacker has 4 wires coming off of it(positive woofer, negative woofer,positive speaker, negative speaker).
speaker impedance- 8ohms
woofer impedance-6ohms
overall- 2*6 and 2*8 ohm connections.
im looking for an amp on ebay and the labels are on watts and not ohms, moreover i see variable power inputs... should i input the max? min? or something in between?
a third question is about channels... the speakers i have have 4 channels...(2 speaker 2 woofer) and most of the amps on ebay are only 2/3 channels... how bad does the sound qualty decrease from putting the 2 subwoofers in parallel?
a forth question in the subject is returning to the impedance of the speakers... i heard you need slots in the same impedance or lower for a speaker... not higher otherways you will damage the speaker... is it true? if is how do i calculate the impedance of the amps outputs???
i thought of this one http://www.ebay.com/itm/like/183002518980?vectorid=229466&lgeo=1&item=183002518980&rmvSB=true
but can i connect the woofers to the so called "super bass" input?
thanks ahead for any answers and if any of you have a good amp that answers my need on ebay to recommened that would be awesome!
 

wayneh

Joined Sep 9, 2010
17,496
So the speaker has no internal crossover or amplifier for the woofer element? Is it possible to put the woofer in parallel with the other elements? This might lower the total impedance into the range of 4 ohms or so, but that's OK for many amps. I'm just wondering how the speaker manufacturer thought these should be used.

What sort of content are you primarily planning to listen to? You might make a different choice for music than for movies.

I think my approach would be to get a separate, single channel subwoofer amp to drive the two woofers in parallel. This would be good for the LFE channel in movie content. If your main goal is music, I might look for an appropriate crossover network to add to the speakers, so that the woofer and the rest are wired in parallel but the crossover sorts out what frequencies go where.
 

Thread Starter

TITANB324

Joined May 6, 2017
5
So the speaker has no internal crossover or amplifier for the woofer element? Is it possible to put the woofer in parallel with the other elements? This might lower the total impedance into the range of 4 ohms or so, but that's OK for many amps. I'm just wondering how the speaker manufacturer thought these should be used.

What sort of content are you primarily planning to listen to? You might make a different choice for music than for movies.

I think my approach would be to get a separate, single channel subwoofer amp to drive the two woofers in parallel. This would be good for the LFE channel in movie content. If your main goal is music, I might look for an appropriate crossover network to add to the speakers, so that the woofer and the rest are wired in parallel but the crossover sorts out what frequencies go where.
The speaker dont have an internal crossover element for my knowledge... 4 separate wires coming out of each speaker... My main goal is listening to music and about the external crossover thing you talked about... You mean to make yhe speaker and subwoofer a single channel or to make the two subwoofers into a single channel some other way than simply putting them in parallel?
 

MrSoftware

Joined Oct 29, 2013
2,188
Low frequencies are omnidirectional, your brain cannot tell where they are coming from, so it's fine to run SUBwoofers together on the same channel. As frequencies get higher your brain does a better job at detecting direction, so anything that produces higher frequencies that your subwoofer should be on a separate channel. If you use passive crossovers and are happy with stereo, then just get a 2 channel amp rated for that impedance and you should be fine. If there are no passive crossovers then get yourself 3 or 4 channels of amplification. Run the mids/highs on separate channels, and run the subs together or on separate channels, it doesn't really matter. You will want a crossover of some sort. Passive can go in the speaker lines, active will go on the line level inputs to the amplifier. Some amplifiers have a crossover built in. The crossover frequencies and steepness (for lack of a better term) will depend on your taste in music, so get something adjustable.

Edit --> The amp you linked, for roughly $5 including shipping; ignore the specs, they're not accurate. You get what you pay for, and for $5 you won't get much.
 

Thread Starter

TITANB324

Joined May 6, 2017
5
Low frequencies are omnidirectional, your brain cannot tell where they are coming from, so it's fine to run SUBwoofers together on the same channel. As frequencies get higher your brain does a better job at detecting direction, so anything that produces higher frequencies that your subwoofer should be on a separate channel. If you use passive crossovers and are happy with stereo, then just get a 2 channel amp rated for that impedance and you should be fine. If there are no passive crossovers then get yourself 3 or 4 channels of amplification. Run the mids/highs on separate channels, and run the subs together or on separate channels, it doesn't really matter. You will want a crossover of some sort. Passive can go in the speaker lines, active will go on the line level inputs to the amplifier. Some amplifiers have a crossover built in. The crossover frequencies and steepness (for lack of a better term) will depend on your taste in music, so get something adjustable.

Edit --> The amp you linked, for roughly $5 including shipping; ignore the specs, they're not accurate. You get what you pay for, and for $5 you won't get much.
In your opinion this one will give me decent quality?
https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.ca/ulk/itm/352141847310
 

crutschow

Joined Mar 14, 2008
34,281
If you are listening to music you might want to consider adding a tweeter to fill out the high frequencies.
What size is the "mid-high" speaker?
What size is the subwoofer?
 

Audioguru

Joined Dec 20, 2007
11,248
Aiwa made cheap junk. When they almost went bankrupt they were bought by Sony now are owned my Americans.
The "200W" cheap ebay amplifier has a power jack labelled 12V/2A which is 24W. 12W for heating and 12W for an output, 6W per channel.
 

MrSoftware

Joined Oct 29, 2013
2,188
When it come to music, everything is subjective, what you and I consider decent quality might not be the same. If all you want to do is amplify your guitar through the speakers that you posted a picture of, then that amp will probably be fine, give it a shot. Those are not high end speakers so don't spend much time or effort trying to make things perfect.

Side note; the power input on that amp is 12v, 2A, which gives you 24 watts total input. Power output will be something less.
 

Audioguru

Joined Dec 20, 2007
11,248
Side note; the power input on that amp is 12v, 2A, which gives you 24 watts total input. Power output will be something less.
The Chinese description of that tiny amplifier is useless. It has Three outputs, left and right for satellite midrange speakers and a "super bass" output for a woofer. Then its 24W is divided: 12W for heating and maybe 3W for each satellite speaker and maybe 6W for the woofer.
 

MrSoftware

Joined Oct 29, 2013
2,188
Or the sub output could just be the bridged connection for channels 1 and 2. A number of car audio amplifiers back in the day would tolerate simultaneous bridged and stereo connections. The Phoenix Gold MS line comes to mind. I think their marketing departments called it Tri Linear Mode or something like that. My guess is this must be a class D, or a cheap class A/B without a power supply stage. How they can produce any circuit board, put it in a pretty box, cover the ebay fees, the pay pal fees, ship it and still turn a profit for only $15 just boggles my mind.
 

Audioguru

Joined Dec 20, 2007
11,248
That is a good idea that I have never seen and never tried:
Make one channel's output the opposite phase of the other channel and bridge them driving the woofer. Then connect a satellite speaker to one channel and another satellite speaker with its phase reversed to the other channel. Since most bass is mono then the bridged woofer plays bass and the satellite speakers work normally.

Chinese products have a very low cost because they use very cheeeep parts that do not last long. Maybe this "200W" amplifier produces only 1W per channel. How much rice do they put in an electrolytic capacitor or lithium battery?? Are the workers in the factory little kids who are paid a bowl of rice each day?
 

MrSoftware

Joined Oct 29, 2013
2,188
Going entirely from memory (back to the 1990's)... I believe both stereo channels were wired with normal phase. The amplifiers have dual rail power supplies, so bridged used the + from one channel and - from the other.
 

Audioguru

Joined Dec 20, 2007
11,248
Going entirely from memory (back to the 1990's)... I believe both stereo channels were wired with normal phase. The amplifiers have dual rail power supplies, so bridged used the + from one channel and - from the other.
The - of an ordinary amplifier is ground then your idea will not work. A speaker is bridged when it has the + of one amplifier on one wire and the reverse phase + of the other amplifier on the other speaker wire. The phase reversing is done at the amplifier's input so its satellite speaker will need to have its two wires reversed to get the correct phase.
 
Top