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Multi-Way Conventional loudspeakers with crossovers

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Old 12th January 2013, 05:01 AM   #21
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On the Lpad question, the tweeter already has attenuation via the two series resistors (quite a bit actually)... I'm not sure why one comes before and one after the crossover.

If you calculate an lpdad you would want to (at the least) look at incorporating the second resistor into the lpad. you may be able to do away with the first one. I'm not sure what effect (if any) that first resistor will be having on the functioning of the crossover.

Good to hear it is going well I've been suprised at how much bass my MTM's have, and they are 5" sealed alignment that starts to roll off around 200Hz! F3 around 80Hz. It is noticable that it is lacking, but they are a lot better than I would have expected!

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Old 12th January 2013, 09:19 AM   #22
ODougbo is offline ODougbo  United States
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Thanks again Tony.

I might not need the attenuation; I'll tell ya, the tweeters never sounded better. It's nice that the tweeters don't cost a lot, I'm thinking the parts for the xo cost more than the drivers ($50W + $32T).

Q. I guess it doesn't matter the sequence of caps-res.-coil (+ to -) they flipped them on their drawing.
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Old 12th January 2013, 11:38 AM   #23
togril is offline togril  Australia
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Ive been following this thread with interest, if not sporadically, due to location at present.
Odougbo and I have used the same TBs in forward ported cabinets. (I also found the top range a bit duller than expected - even untreated).

@Odougbo: Did you get that mic going? Very interested in the results you got from your build, which I like very much.
It was the last step I wanted (and still want to) invest in, so this a great resource for me.
However the only mic I have is a Blue Spark.

Last edited by togril; 12th January 2013 at 11:41 AM.
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Old 12th January 2013, 11:49 AM   #24
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Quote:
Originally Posted by wintermute View Post
On the Lpad question, the tweeter already has attenuation via the two series resistors (quite a bit actually)... I'm not sure why one comes before and one after the crossover.

If you calculate an lpdad you would want to (at the least) look at incorporating the second resistor into the lpad. you may be able to do away with the first one. I'm not sure what effect (if any) that first resistor will be having on the functioning of the crossover.
The resistor (4.7 ohm) after the crossover is to raised the impedance of the tweeter to about 8 ohms. By doing so, the capacitors in the crossover are of a much lower value.

The first resistor (1.8 ohm) is used to attenuate the tweeter.

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Mike
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Old 12th January 2013, 12:17 PM   #25
ODougbo is offline ODougbo  United States
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Thanks Mike.....I had a guess that the 1.8 could be changed to attenuate the tweeter (have a nice pair of 2.2ohm, maybe I'll try them)

togril, I don't think you'll be hating me if you buy a pair of XT25 tweeters - these are sounding wonderful; great imaging (even with the set-top-tweeters).

Maybe get Madisound to build a XO, I don't think they charge much. I am very tempted to send them a plan. I.e. I have a second pair of W5-1611SAF's
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Old 12th January 2013, 02:46 PM   #26
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Yes, the first resistor is for tweeter volume adjustment. If your tweeter is too hot, you can try changing it to 2.2 ohms.

Do not change the 4.7 ohms after the xo. Doing so will affect the xo.

The VIFA XT25TG-30-04 are nice tweeters. I have these and the XT25SC90-04. Come to think of it, it was only a month or so ago that I re-tested my 6.5" Silver Flutes (W17RC) with the XT25TG30-04. No problem crossing at 2.5kHz (18dB/oct).
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Old 12th January 2013, 04:40 PM   #27
ODougbo is offline ODougbo  United States
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Thanks Mike,

Every once in a while I'm thinking the treble is a bit high, then the next song blows-me-away. I'm having a blast with these!!!
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Old 13th January 2013, 08:59 AM   #28
ODougbo is offline ODougbo  United States
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A pm question about the tweeters - going to jump on soap box for a minute:

The Vifa XT25, that's a great tweeter and a great deal ($32). I don't see them working with a 6db slope, but the xo from the d'Appolitito is working beautifully! The depth is so good it's laughable; sound is moving front to back as much as left to right. Bells, etc are floating around the room like a science museum planetarium; hearing details in "strings" that I've never heard before. (they are 1 meter above floor - ear height, sitting)

These are by far the most easy-to-listen pair of speakers I've ever had - can't wait to turn them on again. [I've had many a speaker, store bought, kit, etc.]

btw, I'm only going for 1/2 credit on this hybrid project; the box was a modification from a fellow DIYer, and dido on the d'Appolito xo. If not for the help, these speakers would be sitting on the bench - or might have gifted them.

Thanks to the forum guys!!
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Old 13th January 2013, 08:10 PM   #29
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Quote:
Originally Posted by Michael Chua View Post
The resistor (4.7 ohm) after the crossover is to raised the impedance of the tweeter to about 8 ohms. By doing so, the capacitors in the crossover are of a much lower value.

The first resistor (1.8 ohm) is used to attenuate the tweeter.

Regards
Mike
I think my brain was on Holiday Mike yes the second resistor if changed will definitely affect the crossover slope!! I'm not sure what I was thinking

I believe it will also be providing attenuation as well. as power must be being dissipated in the resistor. but messing with it would require redoing the rest of the crossover.

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Old 13th January 2013, 10:33 PM   #30
ODougbo is offline ODougbo  United States
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I did go back and add a terminal for the 1st resistor; thanks for the heads up on that!!
(now it's a 30 second job to switch)

So tried several, even a 4ohm, which I could hear the tweeter, but too low. I settled on a 3.3ohm the highs are fine/better balance.

[the tweeter is on 12" wire/lead, which is handy for prototype work]

Going to build one more pair for sure.
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