Which amplifier to choose for these 3 speakers?

[kralj111]

Hi all, I have 3 speakers that I need to connect to the amplifier.

Speaker model is SAROS SR8T-B-T-EACH:
https://www.crestron.com/Products/Audio ... T-B-T-EACH

Note that this is 70/100V speaker.

Amplifier must have Bluetooth capability.

These 3 speakers are placed in a 80m2 workshop in a letter L shape (if you can visualize) and the main purpose would be to play some music while working.

I would appreciate f you could suggest 2 options: the cheapest amp that will do the job and a high-end option to get the most out of these speakers.

Please let me know which amplifier(s) would you suggest buying and how to wire these speakers into amplifier.

Many thanks!

[Hugh Robjohns]

Hi all, I have 3 speakers that I need to connect to the amplifier.

Speaker model is SAROS SR8T-B-T-EACH:

Note that this is 70/100V speaker.

The link suggests those speakers also have an 8 Ohm (transformer bypass) mode so could be connected to a standard amp if preferred... but three speakers is an awkward number to work with.

So sticking with a 70/100V line amp is probably the easiest option. Just add up the power raps you think you'll need from each speaker and pick an amp that exceeds that number.

I don't know where you are in the world, but you'll find plenty of local options if you Google for "100V line amplifier".

Adastra, Inter-M and Monacor are popular brands, with most models having a BT input.

[kralj111]

Thank you, Hugh, for your help.

I did try to conenct to regular amp with 8-ohm setting on speaker but it didn't work.

Just to be 100% sure. I should wire the speakers in parallel and connect to 100V output on the amp?

These are speaker transformer taps: 7.5W/15W/30W/60W at 100V.

So, if I want all 3 speakers to run at 60W, I need the amplifier that can provide minimum of 180W on a 100V output. Is that correct?

Or say, 3 outputs, each one at least 60W?

[Hugh Robjohns]

I did try to conenct to regular amp with 8-ohm setting on speaker but it didn't work.

Odd. I think there are two 8 ohm positions (at 12 and 6 o'clock) so it might be worth trying both (but only move the switch when the amp is turned off.

just to be 100% sure. I should wire the speakers in parallel and connect to 100V output on the amp?

Yes — the job is made easy as the speakers have In and Thru terminals wired in parallel. So you wire the amp to the In terminals of the first speaker, then run another cable from its Thru terminals over to the In terminals of the next, and same again for the third.

So, if I want all 3 speakers to run at 60W, I need the amplifier that can provide minimum of 180W on a 100V output. Is that correct?

Yes.

Or say, 3 outputs, each one at least 60W?

Yes, for a multi-zone amp.

[kralj111]

Amazing!

I am trying to find the answer to this question, but I can't, maybe you will know:

Why are we not taking impedance into account when connecting 100V speakers in parallel and yet we do it when connecting low impedance speakers in parallel?

[Hugh Robjohns]

Fundamentally because it's a voltage based connection system instead of a current based one.

With a conventional amp/speaker, if the speaker impedance is low the amplifier has to provide more current, and if it's being asked to provide more current that its output devices can handle it will go phut! Which is why normal amps always have a minimum load rating (typically 4 Ohms, for example).

With 100V line systems, there is very little current, but you do have to ensure that the total power load doesn't exceed the amp's rating.

So if the amp is rated at 100W you could run two speakers at 50W settings, or five at 20W settings, or two at 20W, one at 50W and one at 10W (or any other combination adding up to less than 100W).

It works much like the national power grid, running the distribution cables at a high voltage to minimise the current, which means thinner (and cheaper) cables can be used. Power= Volts x Amps, so if volts goes up, current cones down for the same amount of power.

The transformers built in to each speaker present a high impedance to the line, and the actual impedance varies with the power tap setting, but it's always far higher than 8 Ohms!

For example, a 60W tap presents about 166 Ohms, and a 20W tap is about 500 Ohms.

[kralj111]

Hi Hugh,

Many thanks for your patience, now things are much clearer.

In the meantime, I realized the speaker does indeed work with the low-impedance amp, I jsut didn't turn the volume high enough.

What I will do is just connect 2 speakers to the NAD D3020 (my amp) outputs and run the speakers at 8Ohm setting.

Amp datasheet: https://nadelectronics.com/wp-content/u ... heet-5.pdf

There is no power rating for this speaker at 8 Ohms. Do you know how to find it out?

I hope this amp is capable of handling these speakers, its outputs rated power is 30W each.

[Hugh Robjohns]

In the meantime, I realized the speaker does indeed work with the low-impedance amp, I just didn't turn the volume high enough.

Ah. Good news.... and reassuring!

What I will do is just connect 2 speakers to the NAD D3020 (my amp) outputs and run the speakers at 8Ohm setting.

Sounds like a good plan. Place one speaker half way along each wall of the L-room and you should have plenty of coverage. You'll get stereo too!

There is no power rating for this speaker at 8 Ohms. Do you know how to find it out?

From the brochure you linked to earlier: "Power handling at 8 Ohms is an impressive 200 Watts (program), with a frequency range from 60 Hz to 18 kHz (-10 dB)".

That's a 'program' rating... 60W continuous sounds about right!

I hope this amp is capable of handling these speakers, its outputs rated power is 30W each.

Ah... but 65W of 'Dynamic Power' ... Manufacturers' power ratings are notoriously useless, and I can't find a sensitivity figure for the speaker which is what we really need to know to guestimate the acoustic output level.

So, you'll just have to try and see if the little amp can drive them adequately.

[kralj111]

Hugh, you are an absolute legend. Thank you so much for your help.

I connected speakers tonight and they work well! Thank you!

[Hugh Robjohns]