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robhifi

Not another crossover thread!

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Hi Guys

I haven't forgotten you. I'm back home and will post the xover in a couple of hours time .

A few things to check- I want to make sure I post the correct version

Robert

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Finally here is my crossover design for the RF3.

 

I think I will start a new topic sometime and explain more about what I have done to arrive at this circuit. But for now here it is for anyone who wants to try it.

 

The effect of the notch filter on the woofer is easily heard if you disconnect the tweeter and play music through the woofers only with and without the notch filter.

 

The tweeter crossover was altered to account for the removal of the treble output of the woofers by the notch filter. I have not settled on the amount of attenuation of the tweeter.  At the moment I think 6dB is about right.

 

Robert

 

Edit: The schematic had the polarity of the tweeter incorrectly marked. See later post for revised version

 

Edited by robotc
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Thank you robotc for the xo sheet. I will try it and let you know how it works. 

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Thanks for sharing! Quick question, what is the DC resistance for the 1.0 mH inductor on the tweeter side? Thanks!

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what is the DC resistance for the 1.0 mH inductor on the tweeter side?

 

The resistance is not critical. I modeled the crossover with the total resistance of the 1.0mH inductor plus resistor as 8.2R but an ohm difference either way shouldn't make much difference.

 

The series LCR is there to level out the tweeter impedance at resonance. The load is 4ohms across the whole frequency range.

 

Robert

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I'm curious if some of you crossover geniuses think that a particular design could work without getting too crazy... basically take a B&C DE-750 compression driver (same thing that's in a Klipsch KI-396 and KPT-904 I think) and pair it with an Acoustic Elegance TD18+. Basically a 396 on steroids with a super woofer and a lower crossover and more of a tower'ish footprint geared more towards home theater instead of PA use. B&C says 800 hz 12 db per octave on the compression driver.

https://www.parts-express.com/bc-de750-16-2-titanium-horn-driver-16-ohm-4-bolt--294-616

http://www.aespeakers.com/drivers.php?driver_id=24

Edited by MetropolisLakeOutfitters

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Thanks a bunch for posting all of your work.  I was about to sit down with my Omnimic and WT-3 to do basically the same process, but now I get to skip ahead a bit!  Did you see any enclosure resonances in the impedance plot?

 

What tweeter attenuation ended up producing the response curve you measured?

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I haven't visited the forum for a while and just found your post.

 

The only resonance that showed on the impedance plot was around 200Hz. I did a bit of investigation and found that this was the resonance of the whole enclosure vibrating on the rubber feet.

I braced and damped the enclosures but I couldn't see any differences in the before and after impedance plots. However the changes made a big difference subjectively.

 

The tweeter attenuation on the plot I posted was 10dB. This gave the flattest measured response but I felt subjectively this was too much

 

Robert

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I'm glad you made it back!  I finished constructing the crossovers today and have given them a listen.  I just put them into external boxes to manually tweak the attenuation. (Yes, I removed the crossovers from inside the speakers and wired the drivers right to the binding posts)

20160928_232403_zps877xqqvk.jpg

(My "W" and "T" are backwards too, didn't have enough coffee today)

~200Hz could be a resonance from the tall, unbraced sides of the enclosure.  I'll see what I can measure tomorrow, and try the less invasive approach of 1/2" dowel if there ends up being a peak there.

 

 

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Your crossover looks great. I am really interested to hear how you find the sound from the new version.

 

The resonance at 200Hz was definitely due to the rubber feet. At that frequency the whole enclosure was vibrating strongly. I am not sure if it would be audible when listening to music because the peak was so narrow. Removing the rubber feet went a fair way to reducing the resonance. I can post the measurements if you are interested.

Are you making any measurements of your speakers?

 

Robert

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On ‎12‎/‎4‎/‎2015 at 9:59 AM, Deang said:

Often a problem: the loudspeakers are worth less than the new parts you want to use to modify them. I usually encourage people to put the money into better loudspeakers. For example: do you think a pair of RF-3s can hang with a pair of RF-7s?

 

Yes, this is the problem I was having when contemplating what to do with my new to me RF-3 II's. I paid $175 for a mint pair and was having a tough time talking myself into buying new drop in crossovers for $250 plus shipping. Having read through several different threads I decided to follow Deang's advice here and buy some new Dayton caps along with Mills resistors. Altogether parts cost me $40 shipped to my door and I paid a tech friend of mine to do the work for $50 so $90 total isn't bad.

 

I'd like to comment that I've owned a few pairs of these speakers in the past and never really cared for them. After falling in love with my RF-5's though and realizing they are nearly identical (all the same drivers) as the RF-3's I wondered if it was possible to get similar performance out of them. I can say that this simple crossover change / update has brought them very close to the RF-5 quality that I really like so much.

 

First impressions of the RF-3 stock was the bass really sucked, sounded misaligned? Tweeter lacked detail, sparkle and the sound stage seemed narrow and the overall sound was condensed / small sounding. I ended up flipping the speakers upside down which raised the horn up about 6 inches and really helped the sound of the horn although it still lacked detail. Bass output suffered though quite a bit as the ports are now about 6 feet off the ground.

 

After the new crossovers were installed right away the bass seemed to be the biggest improvement even though nothing in the lower end of the crossover was changed? Very weird but certainly seems to be the case. Also the tweeter is very well defined now and accurate, sound is very much like my RC-7. Improvement was huge, these mediocre speakers are now competitive with the top quality Reference speakers in sound quality, highly recommend upgrading the crossovers, well worth the time and money.

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