2-way crossover missing with no cap on woofer?

hello all,
I recently purchased a 2-way crossover off Amaz**.
it was supposed to be a 12db/octave Butterworth. but it is missing a capacitor on the woofer side??? so what kind of crossover is this?
It also has a series resistor of 2 ohms in line with the cap on the tweeter side. An attenuator by chance??

hooking it up, I find that the highs do get passed to the tweeter, but the woofer receive ALL frequencies... no blocked highs. and it is supposed to be crossing at about 4.3khz.

Any ideas what this circuit is? and can I assume it was designed wrong? or am I missing something?
see attachment.

Thanks.
 

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Galu

Member
2018-04-17 6:50 pm
Your crossover is OK, but not 12dB/octave in both branches.

The single inductor in series with the bass speaker rolls of the high frequencies reaching the speaker very gently at 6dB/octave. The bass speaker can't be harmed by the prescence of some high frequency signal.

The inductor and capacitor combination gives a sharper rejection (12dB/octave) of low frequencies reaching the tweeter as it can be harmed by low frequencies.

The resistor is there to attenuate the tweeter.
 
If you want to hang around the water cooler with Joachim Gerhard, Dennis Murphy, Lynn Olson and Michael Chua and Curt Campbell and Wolfie, you should yak about tank notches and Zobels... they will decide you are not to be messed with! :D

377922d1382302599-restoring-monitor-audio-r300-bookshelf-speakers-monitoraudio_r300-md_final-png


You end up around here:

599664d1487267698-restoring-monitor-audio-r300-bookshelf-speakers-monitor-audio-r300-md-fr-png


A tank notch is a little resistor and capacitor across the bass coil which takes out some bass cone breakup around 5kHz. Works with 6" and 8" bass. The tweeter Zobel smooths the top end.

All good fun. :cool:
 

Galu

Member
2018-04-17 6:50 pm
Talking about simple crossovers Steve, you may remember that I experimented with the tweeter crossover in my old MS100s.

As you know, the bass/mid driver runs with no series inductor, mechanically rolling off above 5kHz, initially at 6dB/octave.

To my ears, the speaker simply sounds best with just a 2.2uF capacitor on the tweeter to deliver the top octaves. You can't get much more simple than that! :)

I've just built a step filter as designed by Martin Colloms for the MS100 in order to tame its forward sounding nature. Basically, the filter steps down the frequencies above around 400Hz by about 6dB. It's a passive circuit which I've placed between my blisteringly sharp CD player and the amp with some good ear soothing effect, and there is now a greater impression of bass from this small, near wall design, speaker.
 
I believe it Mr. Galu. Audax tweeters. 2uF. Almost flat 6" woofer.

I think you have been hanging round with the illustrious Mr. Michael Chua:

Audax TW010E1 10mm Polymer Tweeter Review – AmpsLab

You poseur... :D

BTW, he sent me the circuit for the Finch. I was surprised and impressed with the 6" bass filter. You might get something out of it.
 
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Galu

Member
2018-04-17 6:50 pm
Ha! Ha! :D

My Audax tweets stopped tweeting properly several years back - dried up ferrofluid perhaps?

You may recall that I replaced them with Monacor DT-75/8s, chosen solely because they fitted into the limited space once occupied by the originals.

Luckily, they blend in soundwise as well!

P.S. Will check out the 'Finch'.
 

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@Gala and @system7. thanks for the info. The problem I am seeing with this is I am still hearing high freq at the woofers. I hooked up a frequency generator just as a sanity check and swept the entire 50hz to 18khz. I could still hear highs over 4K at the woofers.
My application is to add this to a guitar speaker enclosure that has 2 10" woofers. The problem I am having is it is very bassy, and not hearing much highs, so I thought if I added a tweeter driver, I would hear more blended sounds.
 

Galu

Member
2018-04-17 6:50 pm
A guitar cab does not contain woofers - the drivers should reproduce frequencies over 4kHz.

Tweeters are used in bass cabs to increase the attack of bass notes - they are not typically required in guitar cabs.

For guitar use I would not include the series inductor, but there's nothing to stop you from experimenting with adding a tweeter via the high pass section of your crossover.
 
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Guitar or PA speakers are quite a different issue from mere domestic HiFi...

Using coaxial products for DIY monitors and home hi-fi applications

This, if IIRC, is an Eminence 10" 10CX with an APT50 CD tweeter:

496921d1438647678-build-own-speakers-eminence_beta_10cx_apt50_apt3-jpg


Here boxed in a WLM Diva speaker:

496920d1438647678-build-own-speakers-wlm-diva-monitor-jpg


The crossover is probably best left to Eminence, who live and breathe this sort of thing:
PXB2:2K5CX - Crossovers | Eminence Speaker

The schematic looks like this, with a lightbulb current limiter on the CD tweeter, being a bit of a PA thing:

690405d1530864957-cupcake-speakers-eminence-pxb2-2k5cx-png


For all that. If you look up the Eminence 10CX you will discover a quite awkward 2.7kHz resonance, as Galu mentions.

All we can say is for the money, Eminence deliver a great result. Hope it helps.
 
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@Galu. Thanks for the info. I actually know quite a bit about guitar cabs. This cab is one I designed and built. The speakers are full range Jensen. Their curve looked to be just right on paper before I bought them. Has pretty good response up until about 5Khz, and then drops off. But the bass response is pretty high SPL ~106hz, so I figured a tweeter would balance some of high end.

I think by me adding a back to it, made it too bassy. I drilled 3 4" holes across the back, hoping it would allow it to breathe more, and increase the high frequency response. But I guess not enough. So thinking of experimenting with adding a super tweeter with bullet.

I built a 2x 12" cab a few years ago and used Eminence, and it sounds great! Kind of wished I had used them for my small cab. I wanted a nice bright Fender sound....
 

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I started out more in the big venue PA world, rather than the politely carpeted small HIFi World.

It's actually a whole different ballgame.

If you build a simple speaker for a disco or live concert, with microphones, at some point the DJ or vocalist wanders in front of the loudspeakers.

The result is a huge feedback HOWL that shatters everybody's ears (OUCH!) and instantly fries the tweeters.

For the rest of the night you are trying to earn a crust with no top end. It's embarrassing. :eek:

I am no expert on speakers suitable for a superb guitarist like Keith Richards or Mark Knopfler.

But what is for sure is if you want a great sound is you do what everybody else does and use 4X 10" or 12" cabinets.

The top end is a matter of choice, But notice Eminence use a lightbulb limiter to protect the tweeter.

Another aspect of PA is you use balanced line on connections. Our puny unbalanced line that we use in HiFi just doesn't hack it over 100 yards of cable. It HUMS!