2ohm subs & amps....

[UNHCLL]

Can you run a 2ohm (or a pair of 2ohm) subwoofers off a 2/4 channel amplifier??

Would I need to wire these in Series or parallel?
Specs call for between 50-750W of power?

FWIW the sub's are Boston accoustics 8.5LF Pro

[UNHCLL]

And could I power the above subs with:

BOSTON ACOUSTIC GT-40
# Dualmode 1 ohm or 2 ohm mono operation
# 10Hz - 95khz frequency response
# Forced air cooling
# Mosfet power devices
# Aluminum security cover
# Sliding track mounted feet
# 4 Channel
# 55 Watts x 4
# 240 Watts x 2 mono
# 0.03 THD distortion
# 20 - 350 hz adjustable HP crossover 12/ 24 Db per octave
# 50- 350 hz adjustable low pass 1 2Db per octave crossover
# 100 db signal to noise ratio
# dimentions 14 1/8" x 2 1/4" 8 7/8"

[europeanplates]

What kind of amp, there are high current amps out there that will drive those speakers.

Tyler

[UNHCLL]

Hi Tyler,

I was looking at the Boston Accoustics GT-40 amp, thats what the above specs are for. I'm even open to only running one of the 2 subs... I'm not looking for explosive bass... more just clean bass in a small enclosure.

I'm on the fence about purchasing the above subwoofer pair... and don't want to do it if powering them(one) is going to require a hugely expensive mono amp.

TIA,
Chris

[netcsk]

If you run subwoofers in series, the impedance of them adds (so in series, those subs would be 4 ohms). When in parallel, the impedance is equal to 1/T=1/R1 +1/R2. This means the impedance is 1/2 + 1/2 = 2/2 = 1 ohm.

Now, you either need a 2 channel (or 4 that's bridgeable to two) that can run 2 ohms, or you need an amp that can run 1 ohm safely (or 4 ohm -- but any car audio amp can do this). With the same amp, 1 ohm of impdeance will give more power than 4 ohm. V=IR -- say 13v and the resistances of 4 and 1 ohm yields a current of 3.25A and 13A respecively. Then Wattage = VI which gives 4 ohms @ 42.25W and 1 ohm @ 169W, which obviously shows a 1 ohm circuit gives 4 times the amount of wattage. Of course, 1 ohm will generate huge amounts of heat compared to 4 ohms, and therefore will always be harder on an amp.


Ok, to sum it up. Your cheapest way out, as far as an amp paired with two of the subs your looking out, would be a 1 or bridged 2 channel amp that runs 4 ohms with the subs wired in series. Your loudest way out would be a 1 or bridged 2 channel amp that runs 1 ohm safely with them wired in parallel. While the middle ground is a 2 or bridged 4 channel amp that can safely run 2 ohms on both channels with each sub on its own channel (depending on the quality of the amp, this may not be a good way to go).

And if you just run one of the subs, you'll need a 1 or bridged 2 channel amp that can safely run 2 ohms.

Your box design is just as (or more-so really) important as the amount of power you're pushing.

[StereoInstaller1]

Your box design is just as (or more-so really) important as the amount of power you're pushing.

Oh yeah, X2. The big trick to understand here is this: 2X 1 watt is NOT 2 watts. It is 10. 2X 10 watts is 100, 2X 100 watts is 1000.

I am talking usable power differences here...real world application. Don't chime in and say "2 watts is too twice the power of 1, I can do the math" because that means you are a fucktard and should be kicked in the nuts. Hard.

In general there is NO MEASURABLE DIFFERENCE BETWEEN 200 and 300 watts. Yes, I mean no difference. Don't believe me? Hook a SPL meter up. You might see 1 or 2 db, but you simply won't hear it, and most meters wont accurately measure it. Especailly at low frequencies.

AND, any dipshit who tells you "that woofer sounds bad, it just needs more power" is AUTOMATICALLY full of shit. If it sounds like shit at 1 watt, it will sound like shit at 1000 watts.

So, The trick in power is to see what you amp wants to see for an impedance load. I understand the Baastun amps have a so-called "High Current" setting, where they wanna see 1 ohm per channel. That means a 2 ohm mono load, see?

The load is carried by both channels, so a 4 ohm mono load (on 2 bridged channels, NOT a mono amp) is 2 ohms per channel, and a 2 ohm load (again, on 2 bridged channels) shows the amp 1 ohm per channel.

It is all a compromise between power and distortion/heat.

If you aren't sure what is the ideal load for that amp, call the manufacturers!

Of course, we care far more about distortion on the mids and highs, so getting the cleanest power matters far more. We are still talking subwoofing, capiche?

So back to Netcsk's comment...if it takes me 100X the power to gain 3db, how the hell do I make this thing loud? Or, how do I make this thing efficient?

Both answers are in subwoofer design. Both answers are in woofer design, too. there is always a compromise between clarity and loud, between small and deep, between accurate and loud.

Personally, I say if you can't hear it, it isn't accurate. End of debate, IMHO.

I love the solid "THWAP" of a kick drum made by the boxes I make. I like hearing a clean output at 25Hz, not 35db down like most sealed boxes have. I like the speed and clarity of a well designed ported box, PLUS I like needing less power to make it happen!

The battle between sealed and ported rages on...I ain't going there. Go search the thread that started a HUGE ruckus back when I built Jordans' box way back when.

Luke

BTW...Jordan LOVED the ported box that I spec'd, that I built. Just so you guys are all clear on who did what.

[UNHCLL]

Luke,

Are you willing to design a box for me/my application and send me the specs/dimensions/etc. I'd obviously pay you a suitable amount for your time to plan it out....

Assembling a box is no major problem for me, its more the actual design that I want to know is done correctly... I can handle nails/screws/MDF/glue/etc....


Are the Boston Accoustics I listed above worth buying?


TIA,
Chris

[StereoInstaller1]

As far as measurements go, I would be glad to spec a box. As far as specs go, I would call the manufacturer.

I have no experience with Boston amps at all, so I really can't comment.

I want ARC audio amps myself.

Luke

[UNHCLL]

As far as measurements go, I would be glad to spec a box. As far as specs go, I would call the manufacturer.

I have no experience with Boston amps at all, so I really can't comment.

I want ARC audio amps myself.

Luke

How about the Boston Subs? I know 8's are small, but they seem to have huge magnets and a decent range of motion?
And did you ever get any of my latest PM's?

[UNHCLL]

Well I ended up with the 2 Boston Acoustics 8.5LF subwoofers.

here are some specs...

RMS: 50-750W each
Moving Mass: 63g
peak to peak maximum excursion: 35mm
voice coil dia: 51mm
Gross internal volume: .3 cu/ft ea (sealed... doesnt offer ported volumes?)

So now its time to find an amp to power these... Anyone have suggestions for a good 1ohm stable amp?

[StereoInstaller1]

PM recieved and sent!

Luke

[UNHCLL]

PM recieved and sent!

Luke

Another silly "newbie" question right back at you..