GPA 3184, any experience?

[fallot]

I am currently using GPA classic series (515C and 288H) in my A5 system, and would like to add subwoofer to my system. After searching around, I am thinking of using GPA 3184. I would like to know the compatibility of this particular woofer to the 515C. Any user experience is much appreciated. Thanks,

[Old Guy]

The 3184 is a great vented box subwoofer.

No problem with compatibility, they operate obviously in different ranges.

Getting into territory where GM would be better, but essentially it's a decent efficiency match. The worst problem is people often use too high a crossover. IMHO 120 Hz is pretty much an absolute upper limit for sub xover, your mileage may vary and all that.

[GM]

Ideally you want the sub system to be enough more efficient than the mains to offset any baffle diffraction loss (BDL) if the mains aren't either in-wall or corner loaded or at least flat up against a wall and not so deep as to create any audible broadband dip due to BDL.

Many folks use high excursion/power handling plus some form of EQ to make up any efficiency/BDL difference though, but this increases the sub system's distortion compared to the mains, so not a good plan overall IMO, especially with an HE one where any LF degradation can audibly affect the system's tonal balance for the worse.

Ideally you'd measure to find how much BDL there is and design a sub system that most closely offsets it, but assuming a 'worst case' +6 dB usually works well and at worst requires some attenuation which lowers its potential distortion even further.

Agreed about the upper limit since ideally you want the subs 'done' (at least -12 dB) by ~120-150 Hz where the signal switches from summed mono to stereo depending on the source, with 80 Hz being the preferred HT choice.

GM

[fallot]

Hello,
I would like to post a follow up to my thread. What if I use antoher pair of 515c and put them in 211 cabinet, instead of using subwoofers? I am thinking, since I have to purchase two new cabinets for the subwoofers and setting them up may cause more problems, wouldn't it be better to just use anther pair of 515c and put them into 211 cabinets? Of course, space factor is not a problem for me. Can you give me an idea of how this set up will turn out sonically? How would the 211 differs from the A5 with additional subwoofers. Thanks,

fallot

[RonSSS]

I have 3184's in the factory Altec cabinets and love them Crossed at 70Hz. I believe the system was called the 8184.....
Awesome woofers.

I have no idea what GM was talking about....absolutely no idea. An explanation in english for us amatuers would be great.

I use my subs with M19's but I bet they would be great with A-7's, no matter how loaded. (515 or 416)

Ron

[GM]

Sorry, I simplified it as much as I know how without writing a far more lengthy tutorial than I'm up for. If you're really interested in learning the physics behind it, then I'll dig around for some on-line info when I get a chance or you can buy Don and Carolyn Davis's most excellent SOUND SYSTEM ENGINEERING tome for a truly in-depth tutorial.

FWIW though, depending on your room's acoustics, your mains/sub system match-up is either ~ideal to an acceptable trade-off between power Vs distortion. IOW, if you don't need any boost EQ (more power) to ~seamlessly blend the subs to the mains, then you're in great shape.

Matching to A7s with their higher efficiency though could require either a second 8184 sub/channel or up to 4x more power required with the attendant increased distortion for a single 8184/channel to keep up.

GM