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Old 9th February 2013, 08:49 PM   #1
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Default 150hz passive crossover

Hi all,

I am working on a project at the moment the would require a crossover at around 150-160hz, I am using a pair of Lowther DX3's in a small closed box and a pair of GPA 416-8A's in a ported design. individually both speakers sound great and it now an issue of crossing over.

I need to know what are the main issues with crossing over passively in this range?

I am thinking about using all Solen caps, inductors and good quality resistors.

I am running a Tubelab SE 300b and will eventually bi - amp with another of the same.

Note: I have read the introduction to crossover design at the start of this forum. But this is the first XO build I have done.

cheers

Luke
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Old 10th February 2013, 01:17 AM   #2
VaNarn is offline VaNarn  Australia
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For the frequency chosen a passive crossover is not a good option unless you are prepared to use massive air cored coils and capacitors that may well exceed the cost of an active system. A minimal series first order network ,8 Ohm_150 Hz would need a capacitor of 132.3 MFd and an inductor of 8.5mH.If it is intended that the xover is only for temporary use then an ironcore coil and a bi-polar electrolytic may prove adequate,initially.
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Old 10th February 2013, 02:40 AM   #3
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If you decide to go 2nd order the inductor size jumps up to 16mH (for a text book 8 ohms)!! To give an idea just how big this would be with reasonable (still high) DCR have a look at the attachment!

You could try Jantzen Pcore coils, I've not used them, but they are supposed to be better behaved than standard cored coils, and are much smaller for the inductance/DCR than air cored. But I agree active is a better alternative at this low a frequency.

Tony.
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Old 10th February 2013, 02:42 AM   #4
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Default A few thoughts

Look here first: Large Open Baffle

It is as good a start as any.

If you wish to use electrolytic capacitors, read this: Charge Coupled Crossovers Article By Jeff Poth

Try to mount on a baffle at least 24 x 54 for best results, and make sure they are 3' or more from the rear wall.
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Old 10th February 2013, 02:53 AM   #5
tvrgeek is offline tvrgeek  United States
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You could do a band pass box for the woofer and maybe eliminate half the crossover. Only thing I can add to the comments above.
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Old 10th February 2013, 03:02 AM   #6
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Default Bi-Amp

Quote:
Originally Posted by magnetman View Post
Hi all,

I am working on a project at the moment the would require a crossover at around 150-160hz, I am using a pair of Lowther DX3's in a small closed box and a pair of GPA 416-8A's in a ported design. individually both speakers sound great and it now an issue of crossing over.

I need to know what are the main issues with crossing over passively in this range?

I am thinking about using all Solen caps, inductors and good quality resistors.

I am running a Tubelab SE 300b and will eventually bi - amp with another of the same.

Note: I have read the introduction to crossover design at the start of this forum. But this is the first XO build I have done.

cheers

Luke
.... Otherwise Mission Near Impossible.

Regards,

WHG
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Old 10th February 2013, 04:57 AM   #7
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Thank you all,

Interesting problem, so I guess active it is. Jon's first link takes me to the Lowther america site, they suggest a 'first watt B4' design from nelson pass, does anyone know this stuff?
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Old 10th February 2013, 12:13 PM   #8
tvrgeek is offline tvrgeek  United States
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Go to the Pass forum right here on DIY. Papa has a big following.

I was a fan of high quality 30W amps. Quality over quantity. I also tried the low power simple and low power tube route. All that converted me to replace everything with big Parasounds. Well, I use a Creek for background music in the morning, but for all the rest of my systems I went for power. Maybe I just never heard a small amp good enough.
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Old 10th February 2013, 01:00 PM   #9
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thanks tvgeek
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Old 1st March 2014, 03:19 AM   #10
oltos is offline oltos  United States
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Hi Magnetman. So how do the closed box Lowther DX3 & the Altec 416 woofers sound?

Did you go with Nelson Pass's B4 active crossover? FIRST WATT B4

How is the midbass and low bass quality from the Altec 416s?

What size ported or vented cabinets did you use?

Notice on one of the two curves from the GPA 416 datasheet that the 8.8 cu. ft. cabinet has very good performance, though the 6 cu. ft. is also quite good.

I read so many complaints at many forums about Lowther drivers having that peaky “shout” in the lower treble region. Does that happen with your DX3 driver? If not, did you use EQ to tame it?



Or could it be that putting the DX3 in a closed box had muted the shout?

Assuming you did biamp this system, and did so with a 2nd Tubelab 300, is that amp 30 wpc, or less?


And are those Great Plains Audio Altec 416 woofers as efficient as Scott Faller says his original Altec 416s are?New Adventures In High Efficiency My Lowther Journey With a rant or two sprinkled in for good measure. Article By Scott Faller

That is, can you drive them with less than 10 wpc in, say a 12 x 17 x 7h room and get full midbass and low bass
out of them for great late night listening?

Regarding the closed box you use with the DX3, is your cabinet designed to prevent standing waves (i.e. triangular shape), diffraction and low dynamics issues? Could you recommend where I might find actual

closed box construction plans for 5” and 8” Lowther drivers?

Thanks
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