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-   -   Need quick bit of advice on Driver/Amplifier Spec. (http://www.diyaudio.com/forums/subwoofers/200493-need-quick-bit-advice-driver-amplifier-spec.html)

lazywretch 14th November 2011 02:46 PM

Need quick bit of advice on Driver/Amplifier Spec.
 
Hi,
We're currently building 2 super scoopers with 18" 800w (1000w re-tested) Drivers. We are aiming to add another 2 to the system pretty soon after completing these and need to know a) if we run them in parallel from each channel can one amplifier safely run all four scoops? b) what would be the best impedance for the drivers (for efficiency and loudness).
Any help on this would be great!
I think that we should be running 8ohm drivers in parallel out of 2 bridged amps for the total 4 scoops but the guys i'm building it with don't seem to think that's the case, please correct me if i'm wrong as i'm not 100%.
Cheers.

chris661 14th November 2011 04:23 PM

Okay, so each cabinet is 8ohm.

A bridged amplifier sees half the impedance per channel, so putting 2 cabs in parallel, then bridging the amplifier, will give the amplifier a 2ohm load. I suspect it won't stand the current (check ratings for bridged 4ohm use on the amp spec sheets).
Putting one cabinet per channel (unbridged) would give more reliable results - you don't want an amplifier blowing up during use. Maybe it'll just shut down nicely, I don't know.

Chris

weltersys 14th November 2011 04:48 PM

Quote:

Originally Posted by lazywretch (Post 2781272)
Hi,
We're currently building 2 super scoopers with 18" 800w (1000w re-tested) Drivers. We are aiming to add another 2 to the system pretty soon after completing these and need to know a) if we run them in parallel from each channel can one amplifier safely run all four scoops? b) what would be the best impedance for the drivers (for efficiency and loudness).
Any help on this would be great!
I think that we should be running 8ohm drivers in parallel out of 2 bridged amps for the total 4 scoops but the guys i'm building it with don't seem to think that's the case, please correct me if i'm wrong as i'm not 100%.
Cheers.

One amp can safely power four 8 ohm speakers no problem, it would need to be 1600 watts per side at 4 ohms to deliver 800 watts per speaker.

If your amps are rated for 4 ohm bridged operation go for it, but make sure they have adequate ventilation.

Many amps rated for 2 ohm output (four ohm bridged) don't sound particularly good with the low impedance load, specifications only go so far.

lazywretch 14th November 2011 07:28 PM

Thanks for the advise I'll take note of it, we haven't actually bought the amp or drivers yet... this is more just to see what the most efficient solution is. Pretty much my question is; are we better getting 8ohm or 4ohm drivers? regardless of the amp/circuit setup (as we can work these around the drivers) and are there any limitations to either?
Cheers.

weltersys 14th November 2011 08:20 PM

Quote:

Originally Posted by lazywretch (Post 2781583)
Thanks for the advise I'll take note of it, we haven't actually bought the amp or drivers yet... this is more just to see what the most efficient solution is. Pretty much my question is; are we better getting 8ohm or 4ohm drivers? regardless of the amp/circuit setup (as we can work these around the drivers) and are there any limitations to either?
Cheers.

There is no one "better" solution.
Matching amp power to speaker power and impedance entails a number of choices.

An excellent plate amp (with built in sub xover) for driving four 8 ohm or two four ohm speakers is the SpeakerPower SP-4000, 4000 watts at 2 ohms.
It will run all day at two ohms without getting warm, and is very power efficient, and only weighs 7 pounds.

That said, putting all your eggs in one amp basket leaves no backup in case the one amp dies, and also does not allow you to split the system into two rentals.

revboden 14th November 2011 09:49 PM

I prefer one amp per box so I can dial in my delays for an array if called for.

weltersys 14th November 2011 10:40 PM

Quote:

Originally Posted by revboden (Post 2781763)
I prefer one amp per box so I can dial in my delays for an array if called for.

That of course also requires a separate delay for each sub output, what DSP do you use, and what type of array do you like to use when called for?

head_unit 15th November 2011 03:28 AM

Quote:

Originally Posted by lazywretch (Post 2781583)
Thanks for the advise I'll take note of it, we haven't actually bought the amp or drivers yet...

Hey, that's a smart time to ask for advice!

Quote:

Originally Posted by lazywretch (Post 2781583)
this is more just to see what the most efficient solution is. Pretty much my question is; are we better getting 8ohm or 4ohm drivers? regardless of the amp/circuit setup (as we can work these around the drivers) and are there any limitations to either?
Cheers.

You can't simply "pick" 8 ohm or 4 ohm drivers. Even if the "same" driver comes in both impedances, due to physics, there will be significant differences between the two versions (if not in parameters then in excursion).

So if you haven't bought amps, pick which driver works best for you in your cabinets, and then get amps accordingly.

Xoc1 15th November 2011 07:29 PM

Most budget amplifiers are optimised for a 4 ohm load.
4 off 4ohm subs and two stereo amplifiers would work together very well, would probably be reliable, and have good audio quality.
If you can get hold of a large single amp that is really capable of driving a 2 ohm load, you could use 2 off 4 ohm cabs per side, and still drive the amp in stereo - no bridging necessary:)


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