Amp to run 2 pairs of speakers in store

meansizzler

Ex Member
Joined
May 11, 2005
Messages
7,892
Reaction score
328
Points
1,889
Location
London
Hi, need some advice on an amp that will drive 4 speakers with adequate volume in a store with around 10 people in at any one time, also need some speakers that will work with it... as I read somwhere that the 2nd set of speakers need to be the right resistance otherwise you will get problems..

They are to be used in a store the size of an average mcdonalds... don't need anything fancy just one line in and preferably 3.5mm in

Was thinking

cambridge audio 640A V2 & Q acoustics 1010i
cambridge audio SR10 & Q acoustics 1020i

Will wither combination work fine?, I noticed the SR10 is rated 85W out and 1020i at 75W, will I run into problems? could the speakers get damaged, also the 1020i are biwired but can I connect them as normal?

Many Thanks
 
So long as it's got 2 separate sets of speaker outs it should be fine - the 640a or SR10 would fit the bill.
 
So long as it's got 2 separate sets of speaker outs it should be fine - the 640a or SR10 would fit the bill.

For the 640A says that you need impedance of 6 ohms to run two sets of speakers but for SR10 says you need 8 ohms

Both speakers mentioned rated 6ohms so will they not work with SR10?
 
The normal operating range for a vast majority of amps is in the range of 4 ohms to 16 ohms total impedance PER AMP CHANNEL.

Speakers in parallel, the normal connection, divide, meaning the result is the impedance of a single speaker divided by the number of speakers.

Consequently, the only way to get two pair of speakers on an amp is if both speakers are 8 ohms, which results in a total of 4 ohms (8/2 = 4).

But, let's look at the application a little more; a small shop with only 10 people in it, roughly the size of a McDonalds? I must ask, do you really need four speakers?

If you have four, you can have roughly a uniform sound level throughout the shop, with two speakers, it will be louder near the speakers and quieter away from the speakers.

So, the point is, it depends on what kind of shop it is. If this is just casual background listening while people shop for general merchandise, the perhaps two speakers mounted up high so you are not getting direct sound, would be adequate. If you need more uniform coverage, the four speaker mounted up high.

If this is a bar or cafe, consider that there are probably some people who want to hear the music and some people who don't, or at least some people who don't want the experience dominated by music. In this case, two speakers in the prime party area would work, and from there the sound from the two speakers would soften a little across the room, so people could still have conversations.

So, the nature of how you want the sound to be in the room matters. Uniform coverage, or hot spots near and quieter spots farther away. The nature of the shop also matters. The experience of someone shopping for music is very different from someone trying to have a quiet cup of tea.

If you are going to have one amp and two pair of speakers, the core rule is that those two speakers must be no less than 8 ohms each (8 ohms or higher)

Now, there are some consumer amps, that are capable of more easily sustaining load below 4 ohms. NAD amps comes to mind, though I don't think it is recommended that you run them for extended periods with low impedance loads. I've never had a NAD, so I don't know the details, but based on the power specs being rated at well below 4 ohms, it implies that these load are workable.

For the record, you can get very good deals on the NAD C315 with 40w/ channel (£160 - SuperFi) and the massively powerful NAD C355 with 80w/ch but only in Silver and only if you walk into the store (£299 - Richer Sounds).

So, while I've given you the basic information about speaker impedance, it would help if you gave us some more information about your application. They type of shop, etc...?

Steve/bluewizard
 
Last edited:
You may be better off looking at PA equipment than domestic hifi equipment in this instance.

Another good value option is an AV receiver in 5-channel stereo mode. :)

We used to run an in-store PA from 2 Denon PMA350s with no problem.
 
For the 640A says that you need impedance of 6 ohms to run two sets of speakers but for SR10 says you need 8 ohms

Both speakers mentioned rated 6ohms so will they not work with SR10?

The 640a will run 4-8 ohms so it should be OK but looking at the 1010's I wouldn't go for them, I'd go for the 1020i which are a bit more sensitive and so shouldn't need you to turn the amp up so much.

One word of advice though, make sure that there's enough air around the amp to enable it to breathe / cool.
 
Consequently, the only way to get two pair of speakers on an amp is if both speakers are 8 ohms, which results in a total of 4 ohms (8/2 = 4).

From amp manual...

When using two pairs of speakers, use speakers with a nominal impedance of between 6-8 ohms each

6ohms for the 1020i so should be fine

Also some idiot mounted 4 speaker brackets and routed cables, can't take down now so will have to make use of them

How do you connect 1020i to 640A as they are biwired but only going to use standard cable which has been pre wired through store.. can't find instructions for them, they suppose to have some kind of bridge?
 
BI-Wired is pointless with speakers like these. And, many would say, pointless under any circumstance.

Steve/bluewizard
 

The latest video from AVForums

Is 4K Blu-ray Worth It?
Subscribe to our YouTube channel
Back
Top Bottom