Thanks guys,
I'll be getting the 2405 16 ohms and will experiment with cap between 1 to 2 uF to determine the optimal point.
Don't think I can go back after hearing the A7 with the 2403. I think the hi freq harmonics produced by the 2403 is making the instruments sounds more real and 3-D.
I finally mustered enough courage to download a version of crossover design software to work out the correct value of the cap to use for my 2405 16 ohms.
Surprisingly, it was quite easy to use. Just wanna be sure, could someone with similar software check my answer:
3 way first order:
Tweeter 16 ohm
Mid 8 ohm
Bass 8 ohm
LF 500 hz
HF 18000 hz
the value of the capacitor calculated is 0.55 uF.
Thanks.
I gather you are planning to let your midhorn run on up and you just want to cut the tweeter in up high to add to the HF output of the midhorn. Your .55uf won't hurt anything, but I don't think the tweeter is going to be making very much sound. Why not try your software using the 10 ohm rating as has been suggested would be more accurate?
David
10 Ohms, not 16.
If it's a JBL 2405, it doesn't matter what the foilcal says.
We ain't just flappin' our digits here....
ng: 18KHz???, what for?, use a 1uF cap, done it bunch of times.
One more question: can I just tap the signal from the Altec 802 terminal or must I tap the signal from the crossover terminals? I think logically it should be the latter because the signal has not passed through the internal crossover yet.
Actually, I also did the calculation for 8 ohms and 10 ohms so that I can get a range of values to experiment.
The reason I am crossing at about 18 khz is because I am worried that there will be too much overlap between the 2405 and the Altec 802.
Seems like there's some consensus on crossing at a lower at about 15 khz. I'll try it out with some cheap cap before investing in good caps.
Thanks.
Do you know where "Koba" is? You can find lots of cheap caps & nick nacks there. They are located in Peoples Park Center (Same building as Larry Hifi), 3rd floor.
Better to tap from before the xover.
Originally Posted by ngccglp
Thanks all,
Datubie - wanted to call you, but thought you will be busy and all...
I've tried the 1 uF cap. Its sounds good. Think I will stick with this value.
Will try to get a longer length of cable to experiment tapping from the crossover terminals. Problem is need to find real thin cables in order to squeeze it into the hole.
Duty's done & I'm for now.
If you're gonna try through the crossover, make it easy on yourself. Grab the output from the horn drivers' terminals. What's crossed over is crossed over. What's phase shifted (from the horn crossover) is just that. You'll be closer to in-phase by tapping it here, and you're so high in frequency relative to the horn crossover point that you aren't going to affect the horn's crossover any at all.
To determine your true crossover frequency with any given capacitor, just drive it directly from the amp at about 1 volt with a frquency generator source. hook the cap between the hot out of the amp and the hot in of the 2405 and the negative of the amp directly to the negative of the 2405. Hook up a volt meter across the two leads on the cap. While sweeping the frequency up, watch until the meter reads 0.5Volts. Now, just to be certain nothing funny is going on, check the voltage across the tweeter terminals and verify it reads the same voltage as it does across the capacitor. The frequency that these voltages are equal is the crossover point, or 6dB down point.
Personally, I would bring those tweeters in lower, since that horn doesn't make it up anywhere near 15KHz before its' output falls off to nothing. If you're shooting the juice to the system, you better make a higher-order crossover if you come in very low.
I'm using 2405's coming in at 7-8KHz, with JBL 2447H's on 2352 horns for mids. In this case, I am tri-amping through a Rane 24dB/Octave crossover (in-phase throughout the crossover region) with the internal CD Horn EQ modification on the mid x-over output to the 2447/2352's amp. This mid/hi setup sits atop JBL 4638 theatre cabinets (JBL 4508A double-15" 8 Cubic ft. 40Hz ported cabs, with 2-JBL 2035H 8-ohm woofers in them).
Sounds pretty good for a dang-ole' club live sound system...
Thanks for all the advice. Just to give an update on my experiments:
I tried the 2405 coming in at a range of values from 8k to about 18k. First impressions were that I liked the extra emphasis on the highs when crossed low at about 8k to 10k. But on extended listening (a few months) and experimentation, I noticed the low freq articulation was masked by the extra high freq, also the sound becomes a bit forward and hard when pushed loud, adjusting the attenuator did not help. After listening to the 2405 for awhile, I decided to unhook it just to see the difference. I was pleasantly surprised to hear a much more natural sounding A7, all the details are presented in a natural way with deep soundsatge, and the speakers sounded relax, which was the reason I bought them in the first place. This prompted me to cross the 2405 at higher freq, just to add the extra sparkle and extension to the 802, while maintaining the inherent character of the A7. Now I have settled on 0.82 uF which is 18k I think.
I learned an important lesson, that Balance in the full freq spectrum is very important, even adding a bit more highs can tilt the character and presentation of the speakers. It has been fun.
You should try out a band pass filter on the 802, leaving the 2405 as the sole source hf producer.
I did this same thing with my 4430s, I wanted just a touch more sparkle on the high-end so I got a pair of 2404Hs. I ended up with .68uF caps coupled with .15mH chokes.
There are two theories to arguing with women, but...neither has worked.
timely thread as passive networks are a weak point in my background
i am also trying different caps on a 2405 crossed over to a LE5-2 mid. the original 1st order cross over point in my box is 7K5. i am trying to increase the slope with an additional cap at around 6K to eliminate the harsh metallic sound of the slot when driven hard around 3-4K.
my question: does adding a high pass filter to an existing network simply increase the slope an additional 6db per octave? in other words if my network produces a 3db down point at 7K5 @ 6db/octave, would a second cap in series increase the slope to 12db/octave.
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