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Impedance question. Layman’s terms please😂

UptonPK

Novice Member
Hi,
I’m a bit new to all this so please take it easy on me! Small words etc😂. I have a PHILIPS MICRO MUSIC SYSTEM BTB2570/12 BLUETOOTH DAB FM RF3075. On the back, by the speaker cable terminals it says “8 ohms”. I want to connect two Roth OLi RA1 speakers to each side ie left & right so I have a total of four speakers. The speakers are 6 ohms each. My understanding is that I can do this safely as long as I connect them in Series and NOT Parallel. Can anyone enlighten me? Thanks.
 

noiseboy72

Distinguished Member
Correct. Paralleling speakers reduces impedance and series increases it. Your amplifier would probably quite happily drive both pairs in parallel, but you do run the risk of damaging it if you turn it up too loud.

Big question is why you want to connect 4 speakers to a stereo amplifier. There's rarely any benefit to doing it.
 

UptonPK

Novice Member
Thanks. It’s just because of the size of the area I want to cover. So are you saying that I should connect in Series but could connect in Parallel providing I keep the volume down?
 

noiseboy72

Distinguished Member
It's a risk to connect in parallel, but depending upon the amplifier, you may find that it won't go loud enough in series.
 

Hixs

Distinguished Member

UptonPK

Novice Member
One last thing, if I did try to connect in series, the worst that can happen is that it will be low volume? Or could more serious damage occur?
 

Hixs

Distinguished Member
What sort of size room are we looking at here? you may well be over estimating what you need.
 

UptonPK

Novice Member
To be fair...I am!!! The room is only 5m x 4m but I just liked the idea of a speaker in each corner! Maybe I’ll put them all up but only connect two of them😂😂😂
 

Hixs

Distinguished Member
A single pair of bookshelves will suffice. Run a Denon DM40 with a pair of rebranded missions (5" drivers) in such a room with zero issues. The Denon is a fair bit better, but yours will cope just fine.
 

Hixs

Distinguished Member
Worth noting that speakers mounted in top corners isn't a great idea unless sound quality is secondary to noise made.
 

BlueWizard

Distinguished Member
Speakers in Parallel Divide, so assuming all the speakers are the same impedance, you take the impedance of one speaker, and divide it by the total number of speakers on a given amp channel.

Rt = R / n = 8 / 2 = 4 ohms

In your case -

Rt = 6 / 2 = 3 ohms

I don't think a cheap mini system is going to like that. Even a better quality high powered system is not going to like that. A PA Amp might be OK with it though. In fact, very quickly, at best, the Amp will shut down.

Series Speakers ADD, and this can be independent of the individual speaker's impedance.

Rt = R1 + R2 + R3 +R.....

Rt = 6 + 6 = 12 ohms

Likely even a mini-amp will tolerate this. The general range for most amps is between 4 ohms and 16 ohms. You typically run into trouble outside this range. Below 4 ohms the Current demand is too high. More Current means more Heat, which means more stress on the amp. Above 16 ohms, the load becomes too light and the Amp can becomes unstable.

But here is the thing, in Series, each speaker, assuming they are the same impedance, gets HALF the Signal. So, twice as many speakers each getting HALF the signal means that Four Speaker are not any louder than Two Speakers. Though there are other advantages which I can discuss if you desire. But you seem to want to keep it simple.

In Parallel, which is NOT an option for you, both speakers get the full signal and you have twice as many speakers, so they will be louder, about +6db Louder from experience. But again, not an option for you.

So, while you might gain general sound dispersion, you don't gain volume. And by dispersion, I mean you can place the speakers in different locations and better fill the room. But no gain in volume from 4 speakers.

If you want more sound to fill the room, just get bigger speakers.

The amp is rated at 70w, but knowing Mini-Amps that is 70w to 4 ohms, which is a way of inflating the apparent Power. Though it is not clear if that is 70w for both channels or one channel, another way to fudge the Power Rating. I'm going to guess 70w is both channels, because Mini-Amps are notoriously low powered. So that means 35w/ch channel. But if that is to 4 ohms, then the real power is about 17.5w/ch. Which sounds more like a Mini-Amp.

Mini-Amps like this tend to be packed with features, but you have to wonder how they manage to get so many feature into such a small package at such a low (more or less) Price. Answer: everything is cheaped to the max. They cut a lot of corner to achieve the features and price point.

In fact, likely these devices can not legally call themselves Hi-Fi. There is a ridged standard for the Power Ratings of Hi-Fi Amps, and none of these Mini-Amp adhere to that Power Rating Standard. Therefore, they can't call themselves Hi-Fi.

They do have their place, and they do serve many people very well, but they are not Hi-Fi systems.

There are more details relative to combining Impedances, but I think at this point that just adds a layer of confusion.

If you want more in depth information on Speaker Impedance, you can find it here -


Steve/bluewizard
 
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password1

Distinguished Member
Many cheap all.in one mini systems also tend to quote a 'maximum peak music output'

something like 3000watts but thats a split second probably at 50% THD (total harmonic distortion)

This system is claimed to produce 4800watts.

IMG_20201017_150654.jpg
IMG_20201017_150618.jpg
 
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