Dual Opposed AV15H Subwoofer Build - Page 6

pbc,

Are yours actually DVC versions?

James

The spec for Re (or resistance that you can easily measure) is 2.7ohms, which is not uncommon for a "4ohm" driver. But your multimeter may or may not be accurate to better than 0.5ohm.

You measured DC resistance; actual impedance will vary widely over frequency. Other than short (zero) or open (infinite), I wouldn't worry much about it.

Edit: By the way, nice build!

Very nice!

For your first build you got excellent results and those suckers are going to pound.

Can't wait to hear your impressions on how they sound.

pbc, just wondering, how close are the rear drivers to the wall? I think that when you hear the AV15H's, you'll end up selling the PB13 sub. To integrate all of those subs is not going to be easy (if possible at all), since they are different, two sealed subs and one ported.

From the QSC page on that amp.

Continuously variable-speed fan, rear-to-front air flow.

http://www.qscaudio.com/products/amps/rmx/rmx5050.htm

James

I was wondering the same thing.

not sure if it has been discussed, but the av15's are low q drivers with a -3db point up around 60hz or so. with an 80hz cross and no eq, they may sound like they lack depth. the dcx2496 has a 12db/octave shelf filter which will more or less match the rolloff of the sealed enclosures in the same way as a linkwitz transform (which is what you would use the bassis for). however, if you have a really small room, you may get lucky and have a high enough pressure vessel gain point to not need the shelf filter, but that would be rare.

i'd also call monoprice and ask if your order got screwed up and what the eta is. maybe it is a canada issue. stuff that i have ordered from them arrived within a couple days.

the minimum dc resistance reading will always be less than the impedance, so your reading seams fine. as was stated, impedance will vary with frequency response, because every subwoofer has some sort of impedance peak in the bass.

edit, you can also test your subwoofer wiring by applying a 9 volt battery to them. 9 volts into 4 ohms is about 20 watts, so is a very safe test level. if you wired everything up properly, when you attached the positive to positive and negative to negative, the cones should move out when the battery is applied.

Is this only in a sealed design? I thought John posted measurements of the AV15s running very well even past 500Hz.

Im curious because I have seen them used as bass bins (I believe Salk does this). THere are also some recent new projects assuming the AV15 runs up to maybe 200Hz.

Maybe thats for the AV15H and not the AV15X?

Penn,

I think LT maybe saying that below say 30HZ (just using 30 as a random number) the AV will not have a lot of power, umph, however you want to describe it. This is just the way I am reading it since he mentions the -3 being around 60, I figured he meant once you start to go down past that you will be losing stuff. I could be wrong and I am sure LT will see these and correct as needed.

James

I wish this myth would go away because it's simply bad advice. The AV drivers in that box will show a very wide F6 BW, not anything resembling a .707 second order roll off and the F3 will not be at 60Hz. So, a 2nd order shelf is a stab in the dark at best and is asking the amplifiers for X16 the power across most of the subs operating range, and no other options.

The Marchand Bassis is still the hands-down best tool for shaping in-room response, extension and F6 BW. Short of that, more than a shelf filter is required and +12dB is not recommended in most cases of a 4X15" system powered by a QSC 5050 in 2500 cubes.

Bosso

It hasn't been my experience with the AV15H that the F3 in your box will be 60Hz anechoic. JJ posted a FR somewhere early on and I lifted it. I then laid it over my close mic measurement of the Raven, a dual driver sealed enclosure just a bit smaller than yours.

If I find it I'll post it here, but the F3 was in the low 40sHz, IIRC. JJ's was even lower, but I don't know the specifics of his measurement.


I'll say it again; for multiple subs, I like the features available on the DCX, for mating sub performance to the room, Bassis, all day long. Best to have both.

If you're set on one or the other and not both, I agree that I would get close mic and LP mic traces and look at what the room is offering, then decide.


Should be lots of fun. I'll be following along.


I disagree with the method. I see no reason to pull the subs to a different distance from the mic and in-room response for calibration. I would set the levels from the LP to where they'll sit (your placement is virtually equidistant) and set the AVR/amp levels for best stab at unity gain.


All the more reason to set levels in place.

Bosso

Man, your son is a tough critic

Just so you know, that post just made my night....I cant stop laughing picturing that happening...that and I know that someday that will be me.... lol

john j. (aka stryke) mentions av15h has f3 of 67hz or so in another guys small sealed build. the confusion here is just the point of measurement. when i mentioned 60hz, i was talking about without a low pass filter. with an 80hz low pass filter, the peak is at 60hz or so and the -3db point moves down to around 36hz. also, the 12db per octave is a pretty good guess for a small sealed enclosure, until pressure vessel gain kicks in (and remember that is just the shape of the contour, not how much you have to apply, you may only need a few db, if any in a small room, which is why i hedged my comment the way that i did.)

http://www.aespeakers.com/phpbb2/vie...php?f=1&t=1749

bosso, what does a bassis do that a dcx cannot?

from an old post on htguide:
"The LT can be replicated as the sum of 3 filters - two band (bell shaped) filters and one 12dB/octave shelving filter. The first band filter changes the Q of the box/driver to 0.7 at it's Fb. The shelving filter changes the response to Q=0.7 at the new desired Fb. The second band filter sets the Q to whatever you want it to be, e.g. Q=0.5, at the new Fb.
In practice, you may not even need the band filters. Just use a shelving filter to boost the lows. If the final response curve looks the way you want it to, it doesn't matter how you get there or what kind of fancy name you give it. It's all just EQing the bass response to be the way you want it."
http://www.htguide.com/forum/archive...p4/t-9744.html

Def you should cross those over high, heck maybe even higher for that matter with your layout - you have the perfect scenario for it - you won't have any issues with localization - the subs will basically attach themselves to the speakers.....

By the way - nice to see your boy approves of your subs.... That was pee in the pants funny.... or at least it should have been...