Question about Oaudio500w / selling on AVS.

nasty, the O-audio web site provides this.
http://www.oaudio.com/docs/subamp_variouseqsettings.pdf

This shows the response curves, in room, for each of the SSF settings. Granted, you can't know the boost (in dB) without comparing to the driver alone, and then accounting for boost due to room gain.

Perhaps that's the direction you're pursuing by adding filters to WinISD. If you can also add in room gain filter to your simulation, the actual filter response will be the one that results in a simulation like those shown.

FWIW, with a Tempest X (15") in 3 cu ft, I found 16Hz gave me the best response after a little PEQ. I was also leary of the bump in the 12Hz setting as that's real boost at a frequency that sucks power. As to headroom, only you know how much you need to exceed your needs. This does that for me....

Have fun,
Frank

The filters actual function is directly related to the Q of the system so although it's difficult to predict accurately, models for these purposes are sufficient so no need to over-think it. As for headroom, shure...why not. Better to have the watts and not need them than need the watts and not have em. But remember there's a price to be payed with the Behringer and other Pro amps. There's no built in filter function, NOISY fans and unmatched level inputs not to mention the current draw( and possibly the lack of a sufficient dedicated curcuit to actually provide the EP with the needed current?) and the more complicated installation. But for power on the cheap, the Behringers are hard to beat.

I have two Oaudio's in service where a pro amp just isn't practical.

The amount of boost can be changed in the O-Audio amps by soldering two different resistors. The link to the chart was provided by O-Audio support.

https://spreadsheets.google.com/a/ht...kE&output=html

This thread may help with changing the hi pass filter.

http://www.avsforum.com/avs-vb/showthread.php?t=1371787

Yah it looks like if you set my spreadsheet up (follow Ghani's link above) for 1uf capacitance you can model the oAudio filter.

>>What would I have to do to drop the 12hz setting to NO boost? Is it possible with a resistor change? The other settings can stay the same for all I care, but this would be interesting.<<

Setting Q to 1 and Fc to 12Hz will get that result, but the other results will always change accordingly. So you may have to fool with it a bit to get what you want.

FYI, a Q of .7 gets you an almost flat filter "boost". A Q of 1 gets you an Fc with zero gain (as I indicated above with the 12Hz setting). Q's above .7 begin to add boost above Fc. The higher the Q above .7 the more gain and the closer the boost center freq. gets to Fc.

If you find a filter profile you like using the spreadsheet and want to represent the filter in WinISD make sure you choose a filter Subtype of: SOS, User specified Fc and Q then enter the Order=2 Cutoff=Fc and Q from the spreadsheet.

Good info guys. I just got my O-Audio 500W plate amp in the mail yesterday. I am impressed with the features. I spent about 10 minutes looking at the construction and it looks really well put together. I have a background in electronics manufacturing and (some) electrical engineering. The use of adhesives was very aggressive, a lot of thought went into this design. A unit like this made in America would probably cost 2x as much... but I digress.

Can anyone comment on the viability of this amp in a sealed box that experience high pressure? Problems with leaks or rattles? I read about several people using Dayton Audio amps (I'm not trying to pick on Dayton) that said they ended up building separate enclosures for the Dayton so the plastic wouldn't rattle. I am going to have an optional isolation chamber so we'll see how it goes and what I end up with.

I'm not really familiar with the oAudio 500w amp, but if the only boost comes from the high pass configuration you can use the spreadsheet to figure out what the stock boost is if you know the stock resistor values. Just use the right hand calculator for that.

Hah, I feel pretty stupid now that I think about it. I have a bunch of gasketing tape, I could remove their stock gaskets and install something a little more robust if I need to. Honestly, I think that's the most questionable aspect of the build quality of this amp, mine was kind of messed up. Also, I think Home Depot and Lowes have a large variety of gaskets. We'll see how well the "guts" handle high internal pressures.

I've had no issues with mine in a sealed box with an sdx15. It's a great little amp.



P.S. Behringers are sold at Long & McQuade right here in the Peg if you want one.


P.S.S. It's about time you started building that thing.Good luck, I'm luvin' mine.

Thanks for posting this. I have gone through the very same thought process although in reverse. I started with a used EP2500 and after realizing the fan noise/swap requirement and lack of any HPF I sold it and ordered an Oaudio 500. A big factor for me was just the size/weight/power consumption difference and ability to do a much cleaner and simpler setup. I selected the Oaudio because it looked more versatile than the usual one (which it is) but later realized that versatility came with some issues/risks.

Here are the factory default values for the Oaudio 500w High Pass Filter (from the source):

Switch Setting – 12Hz; C1, C2 = 1.00uF
R8 = 1.96 kOhms
R12 = 154.00 kOhms
Filter Fc = 9.16Hz
Filter Q = 4.43
Fc dB = 12.93dB
dB Boost = ~14dB

Switch Setting – 16Hz; C1, C2 = 1.00uF
R7 = 2.55 kOhms
R11 = 59.00 kOhms
Filter Fc = 12.98Hz
Filter Q = 2.41
Fc dB = 7.62dB
dB Boost = ~10dB

Switch Setting – 20Hz; C1, C2 = 1.00uF
R6 = 2.67 kOhms
R10 = 31.60 kOhms
Filter Fc = 17.33Hz
Filter Q = 1.72
Fc dB = 4.71dB
dB Boost = ~6dB

Switch Setting – 25Hz; C1, C2 = 1.00uF
R5 = 2.43 kOhms
R9 = 19.60 kOhms
Filter Fc = 23.06Hz
Filter Q = 1.42
Fc dB = 3.05dB
dB Boost = ~4dB

I don't know if I've been modeling them correctly but I am using the 25hz setting and model it in WinISD as: Highpass (User SOS, n=2, fc=23hz, Q=1.420).

In order to keep the boost from pushing me past Xmax, I also use the PEQ to put in ~2dB cut at 22hz. In WinISD: Parametric EQ (fc=22.00hz, Q=0.90, gain=-1.9dB)

I am running a pair of Oaudio 12" TC2+ D4 drivers in 4.3 cu ft each tuned to 21hz. The voice coils are wired in series and then the subs are paralleled so I have a 4 ohm load on the amp or 250w to each sub. Works great and sounds great.

Now my frustration with Oaudio is that they won't or can't seem to tell me what the range of the Q adjustment is on the back of the amp, only that it is linear. They tell me I need to measure the result and adjust accordingly but my impression is first and foremost I need the PEQ to protect the drivers. I would guess the Q adjustment on the amp goes from 0.5 to maybe 4 or 5, but that's just a guess. If anyone knows or has a gut feel please let me know.

I'd appreciate any feedback on how I've been modeling this in WinISD. The system sounds great and seems to behave as expected but there are still some unknowns.

Based on playing around in WinISD, my impression is that the only two settings appropriate for a ported subwoofer are the 25hz and in some cases a 20hz setting, and those would need some PEQ to bring the boost back into a reasonable range. To me, the 12 and 16hz settings look like almost certain death for most ported subs. But I've only played with them a little, and I am not certain I am modeling the settings properly.

Comments?

I ran my spreadsheet against your numbers and got the same results. Boost Gain was the only differences. I'll add any differences and the boost center frequencies in case you're interested:
***************
Switch Setting - 12Hz; C1, C2 = 1.00uF
R8 = 1.96 kOhms
R12 = 154.00 kOhms
Filter Fc = 9.16Hz
Filter Q = 4.43
Fc dB = 12.93dB
dB Boost = ~14dB (I get a gain of 11.63dB with a Center Freq. of 10Hz but my spreadsheet only goes down to 10Hz so the 14dB gain may be at a lower freq.)

Switch Setting - 16Hz; C1, C2 = 1.00uF
R7 = 2.55 kOhms
R11 = 59.00 kOhms
Filter Fc = 12.98Hz
Filter Q = 2.41
Fc dB = 7.62dB
dB Boost = ~10dB (I get a gain of 7.7dB Center Freq.: 14Hz)

Switch Setting - 20Hz; C1, C2 = 1.00uF
R6 = 2.67 kOhms
R10 = 31.60 kOhms
Filter Fc = 17.33Hz
Filter Q = 1.72
Fc dB = 4.71dB
dB Boost = ~6dB (I get 5dB Center Freq. 20Hz)

Switch Setting - 25Hz; C1, C2 = 1.00uF
R5 = 2.43 kOhms
R9 = 19.60 kOhms
Filter Fc = 23.06Hz
Filter Q = 1.42
Fc dB = 3.05dB
dB Boost = ~4dB (I get 3.6dB Center Freq. 26Hz)
**********************

You could opt to change the resistors if you wanted to drop the PEQ, but if everything's good now... why bother?

>>I would guess the Q adjustment on the amp goes from 0.5 to maybe 4 or 5, but that's just a guess. If anyone knows or has a gut feel please let me know.<<


It'd be unusual for them to use a Q below .7 since this would result in negative "gain" across the whole passband. .8 might be a closer guess... An upper limit of 5 seems reasonable, this would produce about a 14dB gain at the center freq. and one of their settings seems to run about like that.

I agree, 0.7 or 0.8 to 5.0 would seem to make sense (not as much as a silk screened legend would though!). Fortunately I'm not running on the bleeding edge so I can wing it a bit on the PEQ part. If the 25hz setting didn't model as well as it does in my case, I'd be changing resistors in a heartbeat. Sometime when I have extra time on my hands I may go through the tables and see if another filter (with resistor changes) would work better than what I have now - but the Q of 1.42 does do a little magic for my subs which is good.

So based on the data, do you think I am modeling the 25hz switch setting correctly in WinISD?: Highpass (User SOS, n=2, fc=23hz, Q=1.420)

Thanks for your feedback!

I'm really no expert, but from where I sit you done everything right.

So the 25 Hz subsonic filter is actually 23 Hz?

Yes, but since the filters have a high Q and you have the parametric EQ available, you really need to model both to see which filter and PEQ combination will best suit your driver/enclosure combination. If you're running a sealed sub it is not quite as risky but IMO you still need to check the excursion in WinISD before you try a new setting.

Yeah, WinISD makes no sense to me. Why they use SQUARE METERS for cone area for example, is pretty retarded. (why use a unit you'll always have less than 1?). I have been using UniBox too but I don't think the results from that are very accurate either- it always says I need bigger ports, for example.

You can click on the unit to toggle through the other available units.