2 ohms- are you doing it?

tktran

So the car audio guys have been doing 2 ohm loads for years. Recently the pro audio crowd are doing 1 ohm loads; with the Powersoft iPAL.

So I’m curious, has anyone wired up their 4 ohm drivers for 2 ohms. For even higher sensitivity? What amp did you use- and did you run into any issues?

charlielaub

A "4-Ohm" driver might have a Zmin as low as 3 Ohms. Two of those in parallel is too low for a home audio amp. A pro audio amp can do it, but will probably run out of juice (max power drops off) below 40Hz. The classic example of this is the Behringer NX series (I own a NX3000). 20Hz max power is much less than 40 Hz power because the PS is not beefy enough for those low frequencies.

OTOH, if Zmin is not too low and your amp can support the low impedance of the parallel load, there is no reason not to do it.

From the amplifier side, performance is usually worse when current demand is high. This is true for class-AB but also true to a lesser extent for class-D. Dissipation increases in the output devices and cooling requirements increase.

6thplanet

I do it in my car and will be doing it at home with the OB project. The Ultamax drivers I got from Charlie are dual two ohm, so the coils will be wired series, then paralled with another driver. These will be run by the Bose PM8500 @ 1000W x2

Wolf

I will be doing that with the E150HE44, but carefully to keep DCR golden for 4 ohm stable amps.

Ron_E

I ran a pair of 2 ohm Gold Ribbon Concepts ribbons with a Hafler DH500 for a lot of years. The vintage Proton 930 30 watt receiver I'm using for my computer speakers is rated for 2 ohm loads. I read a review where it measured 66 watts into 2 ohms.

Ron

ugly_woofer

I remember the car audio "cheater" amps that were stable to a fraction of an ohm. I don't run low impedance at home, because there's really no reason for me, I don't listen at high levels, and power is cheap, even if going non-Chinese.

jr@mac

The Dreadnaught will do 2 ohms, but no reason to do so.

tktran

I’ve seen a measurements of a few amplifiers that are stable down to 2ohm. As Charlie commented, yes they do have somewhat higher distortion than in a 4 ohm load.

My woofer bin has a pair of 8 OHM drivers in parallel, with Zmin of 3 ohms, like Charlie mentioned in the first post. so I don’t need 2 ohm amplifier.

But my next woofer bin will probably use dual 4 OHM drivers in parallel. If you have any past knowledge going down this rabbit hole of high current low impedance amplifiers I’d love to hear about it…

Steve_Lee

Do you really think 4" woofers need to be driven by a high current, low impedance amp, Thanh?

tktran

Terrible typo. My goodness, this dictation thingy I use … I didn’t spot it!! (Now Corrected)

Steve_Lee

Just ribbing you, mate!

Ed_Perkins

Most class-D amps configured in PBTL (i.e. mono mode) will handle 2 ohm loads. For example the TPA3255 datasheet lists a theoritical 495 W @ 1% THD+N in PBTL. The TPA3116/8 and MA12070 chips will also handle 2 ohms in PBTL, although at lower power levels.

tktran

Thanks Ed,

I have 2 budget <$100 TPA3255 amps and they both deliver about 100W in 4 ohms. It seems they are limited by the external power supply that they are bundled with.

Have you seen amy affordable commercial implementations of these that actually deliver close to the 495W at 2ohms ?

Ed_Perkins

I know of one from 3e Audio that I would try. Here's a link: 3e-audio.com/amplifier-kits/tpa32xx-with-pffb/?spm=a2g0o.detail.1000023.1.4f5fIQkxIQkxqO. Their 480-1-29A (mono with heatsink) is rated at 480 W @ 1% THD into a 2 ohm load. It has PFFB and very beefy output filter inductors. They're about $110, but out of stock right now. Supposedly will be back in stock in September. Charlie Laub has been looking at these too. Here's a link to a diyaudio discussion of this amplifier line: https://diyaudio.com/community/threads/tpa3255-tpa3251-with-post-filter-feedback-pffb.390701/.

PS: You'll need a beefy PS in the 48-50 V range. The PFFB amps have a gain of 20 dB (x 10) so you also need an input capable of ~3 VRMS to drive the amp up to 450 W.

tajanes

2ohms for home audio ???

If you are looking for quality high output consider: legacy audio 325watts 8 ohms, 650watts 4ohms powerbloc 2, and in 4 channel as well. There are cheaper ‘pro’ amps, and massively more expensive ‘audiophile’ amps but these deliver.

https://legacyaudio.com/products/view/powerbloc4

tktran

Well if some of these class D amps are capable of swinging 20V into a 2-3 ohm load, it’s means I can achieve higher voltage sensitivity by pairing up 4 ohm drivers.

I’ve been looking at all the commercial speakers that’s been measured by Erin Hardison at erinsaudiocorner.com , and most can hardly be called 8 ohms nominal.

Most of them are really 4 ohm designs, even for simple 2 ways. So it turns out commercial guys have been doing this for years!

So higher sensitivity, smaller cabinets, smaller amps? Count me in!