[netaron]

Good evening all,

I have been playing around with a pair of speakers I built about two or so years ago. They consist of Seas drivers arranged in an MTM format and wired in parallel with an impedance of about 4 nominal Ohms. I use an AKSA 55N+ and also a tube amp. I never cared for speakers with a 4 Ohm impedance, so I wired the two identical drivers in series and tweaked the L-pad on the tweeter to match the lower efficiency of the series wiring.

So my question is, are there some draw backs to wiring two identical mid/woofers in series?

The one thing I am beginning to notice is some lack of dynamics and solid punch ?!?,  but very good presentation and definitely an effortless sound at the cost of some resolution?!?!?

Maybe I need to get used to this sound, there is really nothing I can place my finger on, just a slight lack of something..........

I have also been considering a pair of these PAudio drivers........   

http://www.commonsenseaudio.com/ 


Haron

[Tliner]

HI Haron,
The drivers in a MTM design are usually wired in parallel to keep phasing etc in alignment. In your calculations to tweak the xover have you taken into account the value of the tweeter?. The crossover will more than likely take into account all drivers and not just the woofers. alone. When, say the net woofer values are altered by changing from parallel to series independently of the tweeter you will usually find that the xover will not operate as the designer intended and not perform as designed producing all sorts of "unusual" responses ore than likely throwing the drivers out of phase hence the lack of dynamics, punch and bass. Go back to the original parallel wiring unless you want to re do the xover from scratch.                         

You should measure the nominal impedance of the drivers or at least look up the manufacturers specs to make sure what you are trying to adjust.  I don't think that the 55N+ will have any trouble in pushing a 4ohm load.

Good luck,


Laurie

[AKSA]

Hi Haron,

I think Laurie is right, though I'm no speaker man, but it's fine for an AKSA 55 to drive a 4R load, down  to 3.5R is no problem at all!

Thanks Laurie, much appreciated,

Hugh

[rabbitz]

With the drivers in series the crossover will be out of whack by a factor of 4. ie, the inductor needs to be 4x the size and the cap needs to be ¼ of the size roughly.... based on a 2nd order xo.

If you want a change in sound, you could always try it as a 2.5 way instead of an MTM.

BTW, the AKSA 55 has no problems driving low impedance loads and I had a set of speakers that were less than Hugh's 3R5 (more like 3R2 in the lower frequencies) and handled it with ease. 4R is a walk in the park for it.

[netaron]

Thank you Gents for your prompt replies!!!

I have run the speakers with the 55 with really no issues, as a matter of fact, the best sound I have ever experienced from a system was the 55 being directly driven from the CDP with a built in digital volume control.

However, as much as I like the 55, I also enjoy a tube amp once in a while (sorry Hugh, hope you can forgive).....

So, a 4Ohm load bloats the lows somewhat with my tube amp, hence the tweaking.

Dear Rabbitz,

The XO is a 4th order LR, so would your recommended values be doubled?


Thank you all.

[gerado]

Hi Haron

what PA model were you looking at
single drivers or the coax

I have played around with the 15inch coax in a number of configurations , OB , ported or sealed box with mixed results.
Theo

[netaron]

Hi Theo,

I was looking into the Coax models, I would appreciate any feedback. If it's not appropriate to talk on the net, please send me a PM.

Thank you,

Haron

[AKSA]

Haron,

I quite understand the tube thang........  I ground my incisors on tubes, I'll have you know!!     I really like what they do to the music;  their distortion is meliflous, where SS distortion can be very nasty.

You'd love the Soraya, you really would......

Hugh

[rabbitz]

Dear Rabbitz,

The XO is a 4th order LR, so would your recommended values be doubled?

Thank you all.

For mid woofers in series using an electrical LR4, the existing inductor values would be multiplied by 4 and the existing cap values divided by 4.

The tweeter would then have to be padded down to suit. The crossover point would drop a tad and would also slightly alter the phase relationship between the tweeter and mid woofers.

The frequency response would be similar to the parallel mid woofers but at a reduced SPL. How it would sound is anyone's guess.

[ginger]

Wiring the 2 mid/bass speakers in parallel has another benefit. They tend to electrically damp each other.
Cheers,
Ian

[Jens]

My bass system consists of 2 x 4 pcs. 8" Peerless HDS woofers, driven directly (no x-over) by an ICEpower amp.

I've tried wiring the woofers both in parallel and series. For my specific system, there was no difference in sound.

The bass system covers the range 20-250 Hz and uses non-vented boxes. The HDS drivers have shorting rings in the magnet system.

As so often before, things that in theory are supposed to make a difference, may not do so in practice. I do suspect, though, that the shorting rings in the HDS magnet system may play a not unimportant part in this case 

P.S. Be careful when experimenting with parallel wiring. Some amps don't take too kindly to the low impedances (in my case down to 2 ohms!). Fortunately, my ICEpower amp seems to be quite sturdy, although I've later been told by B&O that they will not guarantee the stability of their amps at such low impedances.

I know use a combination of parallel and serial wiring, which gives me an 8 ohm impedance 

[netaron]

So obviously there is a mixed bag that comes with my poor attempt to make my amps happy with a good load. I think I will just redesign the cross over and just go for a 2-way, well actually a 3-way if a sub counts. This way I will have an impedance of around 8 Ohms and this should keep our transistor and tube friends happy. 



Haron