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Old 17th July 2007, 02:18 AM   #1
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Default 27TDFC and Scan-speak 18S/8531G

Hello all. I just built new speakers with 27TDFC tweeter , Scan-speak 18S/8531G woofer and PartsExpress 1q ft closed cabinet. Tweeter is installed in waveguide and for it's crossover just one capacitor is used. It's done exactly as in Zaph's TMM design. For woofer I use 2.2mh inductor, temporarily. I'll
make line level filter for it later. These speakers are driven by 4 channel amp, so tweeter level is adjusted with amp gain and room induced bass boost 60-110hz is corrected with parametric equalizer -4db.
I just can't believe how clean these speakers sound. Even when amp is playing at full power(45w per channel) there is no audible distortion I guess they will be even better after I replace 19ga inductor with line level filter.
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Old 17th July 2007, 04:40 AM   #2
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Great looking speaker and I'm sure it does sound great too. Is this your first project? I use the 27TBFC/G + Dayton RS 6" in my speakers and they are incredible. I would consider a Scan Speak as the ultimate upgrade but Usher makes some serious contenders too.

What exactly is your crossover design? I'm not sure I'm following what you did - do you have a schematic? I'm not sure exactly what you mean by "line-level filter" either - do you mean an active crossover?
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Old 17th July 2007, 12:35 PM   #3
rabbitz is offline rabbitz  Australia
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Both of those drivers are exceptional. You've done a great job.... well done.
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Old 17th July 2007, 07:41 PM   #4
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actually it's my second multi driver speaker project, first one was bamtm.
crossover is very simple just a 2.25mfd cap on tweeter
and inductor on woofer. i just thought it doesn't make sense to design complicated crossover: 1.drivers don't have breakups to worry about 2.one speaker has to be put between wall and large tv, so equalizer must be used anyway.
no, i don't want to make active crossover(for now), just cap and resistor before amplifier, like here: http://www.t-linespeakers.org/tech/f...ssiveHLxo.html
well, in the future i'll make active crossover/equalizer, i just don't have enough knowledge to do it now.
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Old 17th July 2007, 08:48 PM   #5
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Did you calculate a crossover point? A 2.25 mfd cap should start to slope an 8 ohm tweeter above 8,000 Hz, and a 2.2 mH inductor should start to slope the woofer around 600 or so. Unless I missed something? Even lower impedences skew the values farther.

You could have a serious dip in your midrange frequency response here. I'm all for simplicity, but the XO components should at least cross at or near the same point. A first order crossover is usually discouraged in a 2-way design, especially for the tweeter.

You've spent a lot of money on these speakers - the crossover doesn't have to be complicated but I think you have less than the minimum here; they may sound good now but I suspect there could be a significant audible improvement with an adjustment in the crossover.
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Old 17th July 2007, 09:32 PM   #6
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I agree with you, I am definitely going to work on better crossover.
for now:
tweeter section is done exactly as described here: http://www.zaphaudio.com/Waveguidetmm.html

and I agree inductor is too big, it will be replaced with line level filter anyway.
I don't want any inductors in front of such nice woofer
there is indeed a dip around 1khz, but I like it, it gives mellow relaxed sound
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Old 18th July 2007, 04:07 AM   #7
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OK - yer off the hook.

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Old 14th July 2009, 05:27 AM   #8
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it's been a long time since I built them. they are still my main speakers.
here is the crossover I'm using. I know, it may look nuts, but it sounds great. these speakers can play whole day long and I never get tired of their sound. I'm using separate amps for woofers and tweeters.
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Old 14th July 2009, 07:21 AM   #9
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I think it's a very nice design and not nuts at all :-)

Since you already have a 4-channel amp you should definitely try and move the crossover in front of the amp. Getting rid of the inductor between woofer and amp will "tighten up" the bass.
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