500W+ amps for driving your subwoofer

[Cloth Ears]

I've got a project lined up for a sealed subwoofer (2x15's in Isobarik enclosure). I'm looking for an amp to drive this. The drivers are 5.6ohms each, so that's one of:
1) 2 channels @ 5.6ohms each from the same source;
2) 1 channel @ 2.8ohms which looks a bit iffy;
3) 1 channel @ 11.2ohms which is much easier to drive.

I'm looking at things like the Behringer EP2500, ARX SS1200VC, Yamaha P3200, Alto Mistral 1500 or Australian Monitor 1200. These will drive 385-610W (2 channels) into 5.6 ohms, or 770-1220 (bridged) into 11.2ohms, depending on the amp.

Has anyone had experience in using these (or using a dual voice-coil single driver) in this situation. Which is best, driving the coils (or drivers) separately, or bridged in series?

If so, what amp/driver combination are you using? Oh, the drivers are Lambda SB15 (bought from Nick when he was running Lambda).

[MJL21193]

Why isobarik? Need the box small? I dont know the t/s specs for these subs, but i do know isobarik plats havoc with impedance curve. Can be a very hard load for an amp.

[chasw98]

An EP2500 will drive 2 channels at 2 ohms all day log with no problem. I am currentlly using 4 of them to run my IB and it consists of 4 each 2 ohm dual voice coil drivers. All 4 of them are in a 10 space rack case right on top of each other and there is no heat problem whatsoever. I have even taken all the fans out and replaced them with the quiet slow moving model.

Chuck

[richie00boy]

I would wire for the high impedance load and drive bridged.

Have to second the comment on isobarik. IMO better spending the money one one more appropriate driver in the first place, unless you have a big budget, already have the 'best' driver and just want a smaller box.

[MJL21193]

Isobarik is a good allignment for small subs in small boxes, but you have two beautiful 15" WOOFERS - show them off!

[Cloth Ears]

Originally posted by richie00boy
I would wire for the high impedance load and drive bridged.

Have to second the comment on isobarik. IMO better spending the money one one more appropriate driver in the first place, unless you have a big budget, already have the 'best' driver and just want a smaller box.

Thanks for the opinions. Appreciated.

Regarding the Isobarik:
1) I already own the drivers.
2) The impedance peak is exactly twice (if wired in series) or half that of an individual driver in the same 'Q' box. So however I run it I get the same impedance hassle.
3) SAF - the box will be 20" x 25.5" x 32.5" (that's external dimensions) and be -3dB @ 26Hz, -6.5dB @ 20Hz, -18dB @ 10Hz. That is under Xmax at rated power for the drivers (300W) and before I apply any EQ.

TS (for MJL):
Fs 18.10 Hz
Re 5.60 Ohm
Qms 5.57
Qes 0.55
Sd 855.0 cm2
Vas 363.0 l
Qts 0.501
Mms 437.38 g
Cms 0.177 mm/N
Rms 8.930 kg/s
Bl 31.83 Tm

[MJL21193]

Well it sounds like you have a grip on the design. I would be interested to hear the results.
What are you using to model this design? I use Unibox but it does not support isobarik directly. The specs for the drivers look good except for Vas - quite large.
You mention EQ. What are you going to use?
Sorry for all the questions, just never seriously used isobarik - always considered it to be more suited to automotive.

[Cloth Ears]

Hi MJL,

I also use Unibox, having had great success with my bass modules. If you specify "2 drive units in series, compound", or "2 drive units in parallel, compound", then you get a fair estimate of an Isobarik set-up. One that matches the sizings produced by the other freebies I've got lying around (LspCAD demo, LspCAD Lite, WinISD).

I feed the sizings into my own Excel sheets to work out the layout and sheet-cutting info.

Yes, the Vas is quite large, but then they were originally designed as no-compromise drivers... and I was single when I bought them. My partner has accepted the bass modules (12" in 60l - 22.1" x 17.8" x 14.4" - in Tasmanian Oak veneer) - and I'll need to keep it small to get an OK from her for a subwoofer in the house.

EQ. At the moment I'm using a Behringer FBQ3100 into a Behringer A500 for the bass modules, but only when I'm playing movies. Otherwise I don't really bother, as at reasonable volumes it sounds fairly flat to me. Possibly for the subwoofer I might look at picking up a PEQ2200 (also Behringer) parametric EQ to play with the bottom octave. Maybe.

[richie00boy]

I don't get what you mean about the impedance peak and hassle.

Simply it's best to try and drive higher impedances, so I recommend the series wiring and driven bridge approach.

[SimontY]

Originally posted by richie00boy
I don't get what you mean about the impedance peak and hassle.

Simply it's best to try and drive higher impedances, so I recommend the series wiring and driven bridge approach.

Hi,

That's news to me. I thought the general concensus was to choose parallel wiring for best sound. Certainly parallel wiring sounds far superior in a DVC bass driver compared to connecting only one winding. It has been suggested the inductance is halved and that causes a better transient response. Do you think this applies to parallel connections of multiple drivers?

Clothears,

If you have two drivers you should think about building two boxes. This way you can have stereo subs and cancel some room modes. You will get smoother bass and, depending on your x-over point, better imaging too.

Simon