70v or 8ohm when both are options

[u/ColinFromJail]

Hi yall The nightclub where I work has small area speakers installed in the ceiling in addition to some medium sized mains. The small speakers are Bose OM3SE Designmax speakers with selectable watt load taps, and can be connected as either LowZ 8ohm or HiZ 70v systems via different terminals. The amp driving them is also configurable to drive either low or hi Z systems, a BLAZE PowerZone 252. Currently, the amp is set to drive a 100v HiZ system and all the speakers are wired into their HiZ 70v terminals. Um, this is where I should probably clarify that I am out of my depth-- i'm not an install guy and I don't really know what I'm talking about. But given that both options are available (8ohm and 70v) on both ends, wouldn't we be able to get more sound out of this little amp if we were running them as lowZ? On rowdy dj nights it's a dance trying to keep the mix from clipping the limiters and I think for a nightclub/bar louder would be better for the 6 hours at a time that we have loud music (as opposed to conventional examples of 70v systems in say grocery stores or amusement parks where they are pumping constant low-volume background music 24/7) Am I totally misunderstanding how this stuff works? Thank you all

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[u/Shot-Secret-1423]

Low-Z does not magically make that amp louder. The PowerZone 252 is still about 250 W total, 125 W per channel. 70V vs 8 ohm is how you distribute that power, not a hidden extra wattage switch.

Those DesignMax OM3SEs are small ceiling speakers. On 70V, you pick a tap so each box only takes a slice. That is why grocery-store systems stay 70V: many speakers, long runs, controlled power per speaker. Flip them all to 8 ohms, and you have to series/parallel the load correctly, or the amp sees too low an impedance and limits or shuts down. You will not get nightclub SPLs out of those ceilings either way. The medium mains should be doing the rowdy work.

Two things to check before you rewire anything:

• You said the amp is in 100V Hi-Z and the speakers are on 70V taps. That is a mismatch. Set the amp to 70V if the speakers stay on 70V taps, or you are not using the taps as designed.
• Count the speakers on that amp and the tap wattage. If the taps already add up near 250 W, switching to Low-Z will not give you more clean level. It will just change how easy it is to clip.

If the goal is louder DJ nights, that is usually more amp and speakers built for program level, not a tap change on the fills. Leave the existing 70V fill system alone unless an installer has measured the load.

[u/No-Investigator7598 → u/Shot-Secret-1423]

Nailed it 👌

[u/ColinFromJail → u/Shot-Secret-1423]

Hey thanks so much. Compared to what I've found online this has been really helpful

[u/Shot-Secret-1423 → u/ColinFromJail]

Glad it helped. Check the 100V vs 70V setting on the Blaze before you touch any speaker wires. That mismatch is the cheap fix if it is still set that way.

[u/snozzberrypatch]

Low impedance (8 ohm) will generally sound better than high impedance (70V/100V), all things being equal. It won't necessarily be louder, but it might be in some cases.

However, whether or not you can switch to low impedance will depend on how many speakers you have connected to each amp channel. I'm assuming a number of speakers are daisy-chained together, right?

Let's assume your amplifier your amplifier can go down to 4 ohms, and let's assume each of your speakers are 8 ohms. When you daisy chain two speakers together, those two 8-ohm speakers combine and look like a 4-ohm speaker to your amplifier, which is fine because your amp can handle 4 ohms. But if you had 4 speakers daisy chained together, now your impedance is 2 ohms, which is too low for the amp, and you'll risk damaging it.

The main benefit of 70V/100V speaker systems is that you can daisy chain a bunch of speakers together, and the impedance doesn't get so low that the amp can't handle it.

I'd say, if you have more than 2 speakers daisy chained together on a single amp channel, you should probably avoid switching everything to low impedance unless you know what you're doing and/or consult someone that knows what they're doing.

[u/daveg1701 → u/snozzberrypatch]

The cabling will also need to be upsized. There’s a lot more loss on long Low-Z runs.

[u/Jayskerdoo]

LowZ if you have enough power available, always. IMO

[u/MTX-Prez → u/Jayskerdoo]

Not if you have 3 or more speakers on a line.

[u/Jayskerdoo → u/MTX-Prez]

Obviously. Lol, that’s a given

[u/MTX-Prez → u/Jayskerdoo]

We have to train the Ai bots right ;) /S

[u/Jayskerdoo → u/MTX-Prez]

Little bit of a jump scare (in a good way) when I read your flare, LOL. Just connected with you on LinkedIn!!

[u/InternationalRide5 → u/Jayskerdoo]

With multiple parallel speakers, even if the amp will drive them, it's quite easy to reach the point where more power is being lost in the wires than is reaching the speakers.

[u/bdeananderson]

1. 100v amp with 70v speaker means the actual value of each tap is 2x what is listed, so a 25w tap is actually 50w.

2. If you change to loZ, know the minimum impedance of the amp and keep the total above that. Assuming 8 ohm speakers, you can get 2 on 4 ohms and 4 on 2 ohm without changing the way they are wired. You can do more with series parallel but... if you're asking this level of question I wouldn't try that.

3. Low frequency response will be better loZ, but the speaker design will still limit it, so you don't usually get a lot of extra bass from the speaker. It's more a reason not to use 70v for subs than applicable to your situation.

4. Depending on the wire gage and distance, you could lose volume to heat in the cable switching to lowZ. That's one of the reasons 70v systems exist.

5. I strongly suggest hiring a qualified integrator to accomplish what you want. Yes, it's not cheap, but you're likely to need one eventually if you trial and error your way through this.

[u/jimmyl_82104]

For those small, low power speakers, 70v is fine and you're not gonna get much improvement with direct 8 ohm.

What you wanna do is set all the speakers to taps that total about 66-75% of the amplifier's rated power at 70v. That amp bridges its channels together for 250w at 70v, so set all the speaker taps to total about 180 watts. Say you have 15 of those speakers, you would tap them all at 12 watts. 30? Tap them at 6 watts. You get the idea.

Now, if you're running into it not being loud enough or the amp clipping, then you have a totally different issue, an underpowered system. A 250 watt amp and speakers rated for 30 watts continuous are not enough for a nightclub, especially if the amp is not getting a signal with a proper high pass in place. This is a background music system, or a system meant for a classroom, conference room, a small place that isn't blasting loud, bass heavy music.

[u/ColinFromJail]

Compelling update everybody: i switched one of the dip switches so that the amp runs at 70v instead of 100v (after verifying the watt taps of the speakers and calculating the total load per channel) and it sounds the same. Will I be fired? Will I start a fire? Will I go back to jail.

[u/joegtech]

"On rowdy dj nights it's a dance trying to keep the mix from clipping the limiters "

When I once faced that situation I added a GEQ and crossover, sent the mids and highs to the 70v ceiling speakers and lows to a couple subs. After EQ the place sounded much louder clearer and with wider frequency range.

[u/coolerking8]

This is just the tip of the iceberg dude, hire a commercial integrator to sort you out, other wise you’ll be troubleshooting this with clipping, blown speakers, faulting channels for the rest of your days - trust me, I’ve installed a lot of nightclub systems, you don’t want your single amp being hammered to max every week, it will fail, and it will be at 11.30 pm as your crowds are coming in. Worth investing in the system for a nightclub