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).
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).
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
Chuck
Thanks for the opinions. Appreciated.richie00boy said:
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
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.
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.
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.
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 said:
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
Simon,
Connecting parallel vs one one winding obviously will sound different, as in the second case you are only driving half the winding so only getting half the possible coil energy.
Parallel will have less inductance, but generally at the low frequencies for subs it's not a problem. IMO the cooler running amp, less stress and ripple on the PSU, less cable losses and balanced drive offered by bridging a higher impedance outweighs the only shortcoming. Give it a go and see what you think.
Cloth Ears,
Are you building a sealed box? If so then two smaller boxes as Simon suggests would be beneficial, providing you have the power to drive them and the drive unit voice coil can take it.
Connecting parallel vs one one winding obviously will sound different, as in the second case you are only driving half the winding so only getting half the possible coil energy.
Parallel will have less inductance, but generally at the low frequencies for subs it's not a problem. IMO the cooler running amp, less stress and ripple on the PSU, less cable losses and balanced drive offered by bridging a higher impedance outweighs the only shortcoming. Give it a go and see what you think.
Cloth Ears,
Are you building a sealed box? If so then two smaller boxes as Simon suggests would be beneficial, providing you have the power to drive them and the drive unit voice coil can take it.
Rich,
Thanks for the info. I should have an opportunity to try this out for myself, to some extent, soon. I'm gonna try building bass modules with two 4ohm drivers, so I have the option of 2ohms or 8ohms. I'd assumed 2ohms and perhaps a paralleled chip amp would be best but I am open to the alternative. This would be for the range ~40-200hz.
Simon
Thanks for the info. I should have an opportunity to try this out for myself, to some extent, soon. I'm gonna try building bass modules with two 4ohm drivers, so I have the option of 2ohms or 8ohms. I'd assumed 2ohms and perhaps a paralleled chip amp would be best but I am open to the alternative. This would be for the range ~40-200hz.
Simon
I am not positive but it has been my understanding that when two drivers are used in isobarik config. the combined impedance curve is not the same as these two wired individually, either series or parallel. Due to them being so close to each other, with a sealed space between. I will test this one day if I ever put together an isobarik.
As far as parallel sounding better than series? Parallel can sound louder, since lower impedance draws more current therefore more power. Bridged (as in both channels of sterio amp tied together) into the higher series impedance will put less stress on the amp. Also bridged will effectively quadruple the listed power of the amp ( 2 x 100 watts/channel = 800 watts bridged into same load). Bridged is NOT for low impedance though
As far as parallel sounding better than series? Parallel can sound louder, since lower impedance draws more current therefore more power. Bridged (as in both channels of sterio amp tied together) into the higher series impedance will put less stress on the amp. Also bridged will effectively quadruple the listed power of the amp ( 2 x 100 watts/channel = 800 watts bridged into same load). Bridged is NOT for low impedance though
I think that maybe Cloth Ears wants to avoid filling the room with speakers to keep WAF level high. I know from my own experiences that if She Who Must Be Obeyed is not happy with your "artwork" it can drain all the fun out.
With that said, it can be very troblesome to place two subs in the same room without exciting room modes or causing cancellation or overlap. Unless its a very large room, I would think twice about using two. Better to have mains that go a little lower and one well made sub IMO.
With that said, it can be very troblesome to place two subs in the same room without exciting room modes or causing cancellation or overlap. Unless its a very large room, I would think twice about using two. Better to have mains that go a little lower and one well made sub IMO.
Simon, using chips I would definitely go bridged and 8 ohm load. I'm just not a fan of paralleling amps of any sort. Not only is the current high but you mess things up even more by inserting a resistor in the amp output (which becomes even mre significant with lower impedance loads) and have the problem that each amp won't be exactly matched. Bridging and higher impedance is a far more elegant solution.
MJL21193 said:
Well admittedly the idea is only theoretical as far as I'm concerned, because I've not really tried it myself. I did briefly hear two subs running together in my system, but they weren't the same type! I did like it though
My mains go to about 45hz and then my sub kicks in, this works fairly well (4th order rolloff to match the ported mains).
richie00boy said:
richie00boy (also on the ESP forum?),
Yes, it's sealed. But this way I have one box (of the dimensions mentioned), running 50Hz down.
I already have 2 boxes handling the bass from 120Hz down. They are -10dB @25Hz anechoic, but if I EQ them flat, then (in-room) they're much to boomy. I tend to run them as-is.
If I were to create the same sort of box for a pair of the drivers (Qts=.7), then I'd have to make 2 boxes of twice the enclosed volume and then find somewhere to put them. This way, I only need to find one place to put a box of 'reasonable size'.
And, it's probably superfluous - T-rex already can do the water-ripple thing when we're watching Jurassic Park with the current boxes. But then,
devilr there's no such thing as too much bass.Oh, I was planning to go either with the drivers in series (and the amp bridged) or with each channel of the amp driving one driver. I figure that either would be good - I just need to make sure that the house power can handle it
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