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Cousin Billy 28th September 2013 06:36 PM

passive radiators for midrange
I am building a 3-way. The midrange will be the Accuton C158-8-085.

I notice that the frequency response is a little down below 500Hz.

Would a passive radiator help?.

tinitus 28th September 2013 07:03 PM

usually the opposite
pad down whats too much

but you say its used as mid driver
Vas is pretty big for a 5" midrange, with 35liter

how did you calculate it ?
crossover ?

Cousin Billy 28th September 2013 08:15 PM

Hey Tinitus, I haven't calculated anything yet. I just had a thought?.

I will look further into what a passive radiator can do.

AllenB 29th September 2013 06:33 AM

I'd probably consider using the upper crossover to cut above 500Hz.

tinitus 29th September 2013 06:42 AM


Originally Posted by Cousin Billy (
I will look further into what a passive radiator can do.

its calculated like vented BR port

you are not using vented BR midrange, are you ?
(impedance peak, phase issue, xo problem, etc etc)

but without knowledge and experience nothing will ever work properly
even with, its difficult enough

I suggest to start with cheap drivers
and simple 'straight forward' design (if there are any)

AllenB 29th September 2013 09:17 AM

I just noticed what speakers you are using .link.. Very nice by the way..

Can I assume the mids aren't attenuated? yet they are a little quiet for the woofer. I'd use a second amp for the woofers to allow you to make up the difference in level and roll off the highs as needed with the mid.

tinitus 29th September 2013 09:37 AM

1 Attachment(s)
ahh, sorry, I have misunderstood
sounded like a theoretical project
(thanks Allen)

but that impressive looking speaker you have there is not a 3way
or at least not in common sense

it is '3way', sure ... but basicly more like a 2way with sub woofer

why say you are building a speaker ?
looks like you already have
or are you going to rebuild it ?
(its confusing not getting all info)

Cousin Billy 29th September 2013 01:53 PM

Tinitus and AllenB, thank you for your response'.

I will be building a second pair for the cottage.

The woofer is DSP controlled, with a 1500 watt plate amp. The midrange uses a notch to lower the bottom octave's. I found this to sound better than to put a cap in the signal path.

If I build a pair for the cottage, I can always face the woofer forward, and cross higher.

Any thoughts on the sound quality of a passive radiator system for the mids vs. my sealed version?.


AllenB 29th September 2013 02:10 PM

I can't see it sounding better than a closed box, or necessarily easier to work with, to design or to implement. Just my opinion. Anyway, since this low end is being discarded by the crossover it won't be the dominant effect, the filter will.

By the way, how do you notch the low end without source impedance or a capacitor in the signal path, do you use a current amplifier?

Cousin Billy 29th September 2013 02:26 PM

AllenB, yes I use a current amplifier. It is the Atma-Sphere MA-1. It has an output impedance of 2.3 Ohms.

When I was designing the speakers, I worked on the mid to tweeter filter first. Once this was finished, we listened for a few weeks. It was amazing, though I have always preferred a 2-way over a 3-way. When I started adding caps to cross to the woofer, every variation, be it in value or manufacturer, caused a loss of midrange clarity. It was at that point I thought, try a notch. I had a 12mH inductor on hand, did some calculation, and voila, it worked.

The natural roll-off of the midrange (9 liter volume), the notch, and the fact that the slope of the woofer was tweaked with the DSP (digital sound processor), made the cross from woofer to mids quite easy.

I just had a thought. Most of my store bought speakers have been ported. Maybe I only perceive there is a lightness below 500Hz. When I measure, it's about 1dB down. Would I be able to hear this slight drop?, or do I just remember the ported sound?.

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