series crossover with 2.5 way bass

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Hello all, I would appreciate your thoughts.
I have just constructed a speaker using two Peerless HDS 5.5inch
mid/bass drivers and the XT25 tweeter. The HDS5.5 are a sheilded variety available thru a distibutor here in Australia.
One HDS sits on the front of the baffle with the XT25 underneath.
The other HDS5.5 sits on the side of the enclosure. The side-firing
bass is intended to be crossed over at 150hz with the front woofer to augment bass. The enclosure is aligned so as to have a low tuning point which hopefully will avoid any mid-bass lumps.

I have an open mind with regards to the crossover.
I have fiddled with a few parallel passive
setups but I would like to know how you would set up a series
crossover using the HDS drivers in a 2.5 setup as mentioned above?

Also, if anyone has successfully used the ARSXO, could the 2.5 way design be used successfully in this topology?

Any ideas appreciated.

Regards
MADINOZ:confused:
 
You don't actually want to cross over the side-firing bass at 150Hz in this setup. You want to cross it over at (115Hz/W) where W is the width of the front baffle, in meters. This is to achieve baffle step compensation.

To do this, a capacitor should be in paralell with the bass, and an inductor should be in paralell with the tweeter, and the - of the tweeter should be connected to the + of the HDS. The side firing driver should be in series with an inductor, and paralelled across the input terminals of the speaker.

If you search the net, you will find a few designs using this setup.
 
It is not possible to build a 2.5 way with a full series crossover
as the two bass units must be in parallel for the 0.5 way to
work correctly.

The 0.5 way driver and inductor can be placed in parallel with
the input, or theorectically in parallel with the series bass unit.

However in the latter case the series inductor would be
handling both bass drivers currents, not a good idea.

:) sreten.

Example :
 

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The crossover to the 0.5 way at the baffle step point sounds good
(I mean I actually set it up and it sounds good!).
Many thanks
PS Does anyone know what this woofer in parallel might do to the inductance and DCR of the front mounted woofer (if anything)
Thanks
MADINOZ
 
Well, I have finished the design with much thanks to those who offered advise.

Firstly, I tryed a number of parallel crossovers and i was not impressed with the results, so, I moved on to series crossovers......

I have ended up utilising a 0.39 and 0.33 inductor in parallel (low DCR) for the tweeer and a 10uf and 4.7uf (bypassed) for the woofer. This is a theoretical 3700hz zeta series filter though the woofer is rolled off lower that this point to compensate a little for baffle step.
The side firing woofer is run in parallel to the woofer/tweeter (which allows bi-wiring of this speaker to separate the high-low frequencies). The side firing woofer has a 0.56mh inductor in series to roll it off at a nominal 660hz.

The result is a very pleasing, good bass extension with a nice punchiness and a lovely fluid midrange and a bright clear treble.

This crossover did not use any resistor to the tweeter or any zobel networks for the tweeter or woofers. I listened to the speakers with a wide range of values and combinations and I didn't like what the zobels or resistor to the XT25 tweeter did.

The result may be a little treble forward to other peoples' tastes but I think they sound wonderful and my Wife even commented on how much she liked the sound (HALLELUYAH!!!!!!)
The low box tuning (14litres, tuned to 43hz) turned out to be on-target in my listening room and I don't feel any need to employ a sub-woofer to suppliment the bass.

If anyone is thinking about using the Peerless HDS 5.5 woofer, then take it from me, they are a great little unit.
Likewise the XT25 tweeter, with the caveat of limited off-axis response is an excellent value for money unit.
If you don't want to spend big-dough, have a good think about these units!

MADINOZ
PS will post picys if any one wants..........
 
Crossover diagram as requested.
I will post some digital photos tomorrow all being well.
I have christened this design the Shroedinger.

MADINOZ
PS these component values come with the caveat that they sound good to me, in my room and that they suit my current amplifier/CD player. You may well wish to adjust values, add a resistor to the tweeter leg, add zobels or call me an idiot.......
 

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Hi All

I too have just been playing with XT25 and series crossover.
In my case the woof/mid is scanspeak15w8530 unit
At first Itried the ARSXO essentially as shown on the LCAudio site, but found problems with soem rather nasty distortion on larger transients (nasty cracking type sounds)
Also had zobels on both woofer and tweeter.

Have since tried simpler ARSXO as per attached
image.
this gives at this point a better result.
from memory both the ss15w8530 and the ss18w8531 appear to have the same motor and impedence curves appear very similar other than at the low end of the frequency range.
Also the 18w8531 is a bit more efficient and the XT25 needs some more padding down with this crossover, but initail results are very promising to my ears at least.
haven't tried zobels yet.
cheers
 

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Yes the 0.56mh inductor sets the crossover at about 1500hz.
It isn't a classic 2.5 way design.

if anyone has the drivers around please have a fiddle and see what you think of the sound. i'm keen to hear feedback.

For those looking at prospective drivers to purchase, give some serious thought to these units.

Could the HDS 5.5 topple the Vifa P13 off it's best value/sound-5.5inch woofer pedestal?
Just waiting for a flood of responses to that question................

Thanks for all your feedback and corrections.
MADINOZ:
 
0.5 Woofer

Just to illustrate the benefits of the 0.5 woofer at the back of the enclosure for BSC I did some calculations before I did my modification (don't give me any stick about my graphing ability).

The black line is the room effects, aqua without 0.5 woofer BSC + room effects and red is with 0.5 woofer BSC + room effects.

Above 100Hz there is hardly any help from the room for BSC. Without BSC (aqua) shows the BS droop on the bottom and and ends up with 8dB variation but the one with BSC (red) is within 3dB. The plots are rough (don't give me any stick about this either) and are only calculated values but it shows the trend which was enough for me to do it....... and it's confirmed by listening.

It was planet10's graph on the p13 TLb that got me thinking as it showed a great variation between the single woofer and the bipolar.... thanks Dave.
 

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Series xo + 0.5 woofer 1st order

One thing I noticed with the 0.5 woofer is that it sounded so much better with the speaker bi-wired (2-way series + 1st order 0.5).

The 1st order butterworth on the 0.5 woofer did not co-exist very well with the 2-way series crossover coming from the same terminal on the speaker sharing the same cable back to the amp.... tended to suck out the mids. A separate terminal for the 0.5 woofer with it's own cable running back to the amp (speaker B) made a great difference IMO.

Reasons for this???????? Constant voltage????????
 
At long last a picture of the speaker.
Excuse the scrappy nature of the photo but my camera is not-
mucha-good.
Metallic silver finish.
Got some nice cable and bi-wired these speakers last week.
Upper treble balance is now much nicer, bass a little less pronounced but more accurate. Massed strings (classical) now sound a lot richer and detailed.
 

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