$65 Bass Cube

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Poultrygeist

Re: $65 Bass Cube
« Reply #20 on: 1 Apr 2013, 02:42 pm »
When I built this sub I really did not notice that the woofer has two pair of speaker terminals ( two voice coils ) so I bridged the Dayton as usual and connected it to one set of terminals and this has worked great now for several weeks.

The stereo Dayton APA150 ( Emotiva BPA-1 ) is bridgeable into 8 ohms making 150 watts but it's not recommended as bridgeable into 4 ohms. If you connect the 8 ohm dual voice coils in parallel you reduce the impedance to 4 ohms and that would not be desirable for the APA150 but would be for the plate amp as used in the Triska project link.

Another option would be to run the Dayton amp in stereo and connect both channels to the two pair of terminals on the woofer. In this case power would be much less than in bridgeable mode.

Please feel free to chime in if I'm off base on any of this. 

James Romeyn

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Re: $65 Bass Cube
« Reply #21 on: 1 Apr 2013, 04:31 pm »
When I built this sub I really did not notice that the woofer has two pair of speaker terminals ( two voice coils ) so I bridged the Dayton as usual and connected it to one set of terminals and this has worked great now for several weeks.

The stereo Dayton APA150 ( Emotiva BPA-1 ) is bridgeable into 8 ohms making 150 watts but it's not recommended as bridgeable into 4 ohms. If you connect the 8 ohm dual voice coils in parallel you reduce the impedance to 4 ohms and that would not be desirable for the APA150 but would be for the plate amp as used in the Triska project link.

Another option would be to run the Dayton amp in stereo and connect both channels to the two pair of terminals on the woofer. In this case power would be much less than in bridgeable mode.

Please feel free to chime in if I'm off base on any of this.

Bridging an amp doubles current draw into the same impedance, which explains why minimum impedance doubles (bridged vs. stereo).  Ignore this rule at extreme risk of peril. 

My general understanding, and I hope to learn from other posters on this, is that SS amp distortion specs also degrade with lower impedance.  IOW, there is no free power lunch.  Cutting impedance in half doubles voltage and doubles current draw, but it also increases distortion and can even alter spectra of distortion for the worse (i.e., more 3rd and odd harmonics, which are of course more audible and more irritating). 

My SS amp currently in use sounds audibly worse into 8 Ohm nominal load (5.3 Ohm minimum) then it does into the exact same load except twice the impedance (16 nominal/10.6 minimum...I have a strange 2-speaker load that can be halved or doubled by changing from series to parallel...kind of cool for such tests as discussed here). 

Obviously, the whole point here is how do you want your poison: Voltage or Current? 

It is critical to point out too that minimum AWG specs change with the load and source capability.  I've had applications where the speaker cable converted current into useless heat rather than pass the current to the load, in which case your audio tests are moot because you need more copper for proper results.

Each application is different whether you are better off with more V/less A vs. the opposite. 

In your case, I strongly feel woofer control increases operating both VC instead of only one.  Amp function is a wash (almost, see below) but again, in stereo connected to two VC, you'll have twice the speaker cables which is more copper, always a good thing with subs.  Even the speaker wire issue is a separate subject: with subs you are much less concerned about self-inductance with more copper, because you are less concerned with HF performance.

Re. amp function: the lower the amp quality the more likely are channels not perfectly symmetrical.  The less symmetrical are channels the more sound quality decreases when bridging.  So this is another good reason to employ both VC and leave the amp in stereo vs. one VC/bridged amp. 

So many issues, so little time to sort them out....

What are your HP and LP crossover poles? 

Poultrygeist

Re: $65 Bass Cube
« Reply #22 on: 19 Apr 2013, 03:06 am »
I switched to the second option and connected each channel of the Dayton to each subwoofer VC and all is well.  8)