I have a somewhat old multichannel receiver that I'd like to use for prototyping - it has DVD-A/SACD inputs that bypass the filtering etc which is handy for me, and claims 100W/channel. Its Arcam and very heavy so that might even be believable.
It says '8 Ohm speakers' on the back.
I have quite a few 4Ohm nominal drivers (Re is probably 3.5Ohm) that I'd like to play with, active DSP upstream of the receiver.
What's the worst that can happen?
It says '8 Ohm speakers' on the back.
I have quite a few 4Ohm nominal drivers (Re is probably 3.5Ohm) that I'd like to play with, active DSP upstream of the receiver.
What's the worst that can happen?
A fuse gone... no - I'm sure it will be fine. Check temperature now and then during the first run...
Have fun!!
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Have fun!!
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Does it have a protection circuit? If it’s a multichannel, it probably does. That will help if you run it too warm. It’ll shut off the amp. Otherwise just be very careful with the volume.
The amp will be overloaded - but as long as you keep the amp turned down fairly low, it should be fine. It's alright to hope that the amp contains over current protection, but even if it does, it's not something you'd want to rely (certainly I wouldn't).
How come you've got 4 ohm speakers anyway?, HiFi speakers are pretty universally 8 ohms (although Grundig used to like 4 ohm ones), and 4 ohms are usually in-car speakers, or ones for cheap surround sound systems (which are often pretty similar to in-car).
How come you've got 4 ohm speakers anyway?, HiFi speakers are pretty universally 8 ohms (although Grundig used to like 4 ohm ones), and 4 ohms are usually in-car speakers, or ones for cheap surround sound systems (which are often pretty similar to in-car).
I have low impedance speakers because they are raw drivers - I'm using DSP crossover in a 2x4HD or PC and multichannel DAC.
I don't need (or particularly want) to play loud. I can live without excessive Linkwitz transform.
I don't need (or particularly want) to play loud. I can live without excessive Linkwitz transform.
On a slightly more serious note, the problem with AVR are that they already run on the ragged edge of reliability due to the physical constraints of getting enough power supply, heatsinks and output transistors to be able to produce five or more channels of 100w each.
They are usually designed so that they can do this, but only for very brief periods. Higher impedance speakers and hence lower peak currents really help in this regard.
I can see how it would be handy to use the various channels for bi or triamping but you're starting with possibly the least suited type of multichannel amp for this kind of work.
If you keep the volume low and just need it as a bench amp to test things, I'm sure it will be fine and no great loss if it blows up. You might keep it just for mid and treble duty and have another two channel amp for the bass if you need to push the volume for testing purposes.
They are usually designed so that they can do this, but only for very brief periods. Higher impedance speakers and hence lower peak currents really help in this regard.
I can see how it would be handy to use the various channels for bi or triamping but you're starting with possibly the least suited type of multichannel amp for this kind of work.
If you keep the volume low and just need it as a bench amp to test things, I'm sure it will be fine and no great loss if it blows up. You might keep it just for mid and treble duty and have another two channel amp for the bass if you need to push the volume for testing purposes.
Probably fine. I do a 4 way system and the tweeter channels barely move the needle and the mid is also not very demanding. This coupled with no losses in crossovers means the system can play very loud without much input. One thing I always do though even with the dsp is add a cap on the tweeter just in case. I usually set the cap so that the cutoff would be about 1 octave below where I plan to dsp it at to minimize the effect.
Use them in pairs, in series, for proper 8 ohm loads.
Both speakers and amplifiers will be happy with that.
Define "testing".
If it means only sweeping speakers from 20Hz to 20kHz and measuring frequency response at 1W 1 meter they will most probably survive, no big deal, but playing them louder to check vibration, distortion, Bass response, punch, etc. , will definitely overstress the power amp.
Absolute best case you will trigger protection introducing ugly distortion or plain turning channel OFF, not good for testing.
Worst case was already described in post #2
Both speakers and amplifiers will be happy with that.
You might get way with it with a small cheesy amp (say a cheap 15W unit or so) because often the skimpy power supply drops a lot when overloaded (it typically being on the edge even on "normal" use) but a big heavy supply as you describe will have enough power to destroy an overloaded power amp, any day of the week.
Define "testing".
If it means only sweeping speakers from 20Hz to 20kHz and measuring frequency response at 1W 1 meter they will most probably survive, no big deal, but playing them louder to check vibration, distortion, Bass response, punch, etc. , will definitely overstress the power amp.
Absolute best case you will trigger protection introducing ugly distortion or plain turning channel OFF, not good for testing.
Worst case was already described in post #2
Some of the Arcam's have a 4 ohm / 8 ohm switch on the back. Just check to see if yours has this feature. Must be switched when the power is off.
It wouldn’t say “8 ohm” speakers if it has a 4/8 ohm switch.
During the proto and testing phase, speaker systems can have impedances that fall below Re. If it doesn’t need to be loud, I would use a smaller amplifier that is happy down to 2 ohms and has proper overload protection - for any speaker that’s not fully rung out. I use one 40 per channel. “Cheesy little 15 watt amps“ often don‘t sound good enough to fairly judge loudspeakers. This is one instance where you can easily make something better than you can buy (for the purpose).
During the proto and testing phase, speaker systems can have impedances that fall below Re. If it doesn’t need to be loud, I would use a smaller amplifier that is happy down to 2 ohms and has proper overload protection - for any speaker that’s not fully rung out. I use one 40 per channel. “Cheesy little 15 watt amps“ often don‘t sound good enough to fairly judge loudspeakers. This is one instance where you can easily make something better than you can buy (for the purpose).
I don't quite see the relevance of that?, I presume 'raw drivers' just means drivers not in a box? - for building an 8 ohm system you'd use 8 ohm drivers. Are the speakers intended for in-car use? (which would explain why they are 4 ohm), because in-car speakers aren't very good for use in proper audio systems, and often have highly imaginary specifications.
There are no crossover components, the drivers are attached directly to the amplifier.
They will be in enclosures, but each driver will have its own binding posts, and if I decide to make a passive crossover, it will be external.
I see a lot of 4 ohm variants of drivers, I don't know what you mean? Not all have 8Ohm variants, by any means.
I do have some 8Ohm drivers, to be fair, but they tend to be older designs.
I will run sweeps, and do some DSP crossover development. And also some listening, in my study, which is not large,
I'm surprised at suggestions of doom - I'm expecting the amp rails to sag if the current is more than expected and the available power to be only half or so if its really current limited but that should be OK.
What's interesting is that the panel on the back of it (an AVR280) has a label says 8Ohm for all the speakers.
But here: https://www.arcam.co.uk/product,diva-avr280-receiver.htm it says:
- 80 WPC continuous power output into both 4 and 8 ohms loads, with all 7 channels driven
- Stereo continuous output power 100 WPC into 4 or 8 ohms
The Cyrus amps claim 50W into 8Ohm and 70 into 4. I've never really stretched them, but I've had ported speakers and will now try sealed, which enables fun with a transform.
Then it is “4 ohm capable” and won’t give any problems. You might get a speaker system to go low enough for there to be problems, but not any one single 4 ohm driver. They may just say “8 ohm speakers” if it has two sets of outputs that can be paralleled. There are just as many if not more receivers out there that say “8 ohm speakers” and really really really mean it.
Whats the worst that can happen if you run 4 ohms on one of these cheesy ones? Bang, with enough time and temperature. But some of them have “protection” that will kick in quite audibly, or output transistors run out of gain with 4 ohms and sounds like garbage. That’s even worse when testing loudspeakers. For that reason I use an amp that will take virtually any impedance thrown at it.
Whats the worst that can happen if you run 4 ohms on one of these cheesy ones? Bang, with enough time and temperature. But some of them have “protection” that will kick in quite audibly, or output transistors run out of gain with 4 ohms and sounds like garbage. That’s even worse when testing loudspeakers. For that reason I use an amp that will take virtually any impedance thrown at it.
The vast majority of home HiFi speakers are 8 ohm (back in the very old valve days they were usually 16 ohm), some of the cheap little audio units have moved to 6 ohms (to offer higher power specification from a cheap amp), and most in-car speakers are 4 ohms (or even 2 ohms), in order to get more power from a low voltage supply. Likewise, some surround sound amps/speakers are 4 ohm, but again usually the cheaper ones to try and give a higher output specification.
Are your drivers branded?, and do they have model numbers?.
The specs for the AVR280 according to the link indicate it can drive all 7 channels at 4 ohms. As wg_ski noted, the specs indicate the power supply limits the amount of power available in 4 ohm mode to 80W as opposed to 100W in stereo. I think at this point it is safe to assume the amp can drive your 4 ohms safely with an output of 80W available.