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Another FHXL Build
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Old 22nd September 2017, 08:57 PM   #101
Eric is offline Eric  United States
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Another FHXL Build
Curly Maple and Bubinga will be an excellent combination! I was really struck by the contrast of Bubinga and Birch before I added the veneer. What kind of finish are you planning to use?
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Old 20th November 2017, 01:47 AM   #102
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So, I've been living with my FHXLs for about 2-3 months now. I enjoyed them when they were first completed, though my first reaction was that they were a bit bright on top for my tastes. Compared to the previous speakers in their place (Atlantic Technology System 350 THX), they cast a much bigger sound stage, but were still bright to me.

I finally found some time to carry them down into the basement and conduct some measurements today. As I suspected, there was a pronounced wide-band hump in the 5kHz to 15kHz region. It stood out on some recordings, but not on others. The primary place where it was obvious was with spoken voices - television shows broadcast in 2.0 sound format were typically the worst. After adding a simple notch filter, the difference is astounding! The upper-mids and treble are reigned it a bit from where they were, but is still plenty bright for my tastes. The part that I didn't expect was that bringing the treble in line with the lower midband range allows more of the bass to come through!

I know I said this before, but WOW - I am just FLOORED with the bass that the FHXL design puts out! Especially after adding my filter tweak! I was enjoying them so much, I got myself in trouble with my the rest of the family for excessive volume after spinning a few albums... At first, I actually had to get up and touch my sub to make sure it was really off! I tend to be a bit of a bass head, so this is really quite something!

I'm just beyond giddy with delight! These speakers sound AMAZING - I'm so glad I spent a few hours measuring and tweaking. I ended up paralleling a 1.0uF cap + 0.27mH coil + 28R and putting this in series with the positive speaker terminal. It brings that 5-15kHz hump down by about 8dB.
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Old 20th November 2017, 02:11 PM   #103
Eric is offline Eric  United States
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And some data from the FHXL and Alpair 10.3 driver. It seems nearly pointless to discuss speaker response without adding a few graphs...

In the attached graph, the purple line is the speaker straight from the amp with no correction at all. After a few hours of playing around, I hit on the green response curve after putting a 0.27mH coil, a 1.0uF cap, and a 28R resistor in parallel and attaching this bundle in series with the positive speaker terminal. As usual, it's probably best to ignore everything under 200-300Hz.

Of course, the irony here is that the results of my fiddling around are probably very similar to the response plot from the 10P driver all by itself... Though, this result is cheaper than buying another set of drivers and selling these. Plus, it comes with the added ability to adjust the response just how you like it. Do you like more treble? No problem - reducing 28R to 20R adds back 2dB in this range. Reducing it further restores more treble. For the ultimate in flexibility, add a variable resistor and dial in exactly the amount of treble that makes you happy!
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File Type: jpg fhxl original vs notch filter.jpg (122.6 KB, 70 views)
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Old 20th November 2017, 02:29 PM   #104
Eric is offline Eric  United States
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Not content to leave things alone, I also spent a few minutes measuring the difference that the stuffing below the woofer makes. I turned the speaker around and place my SPL meter on the floor just behind the rear horn vent to measure the low end response.

Below are two graphs, one comparing 100% stuffing (80g) with 50% stuffing and another one comparing 100% stuffing with no stuffing. In both cases, the 100% stuffing level is represented by the gold trace. Reducing the stuffing results in a few dB more bass at the low end, but visibly adds to the peaks at 1500Hz and 5-8kHz. In the end, I left the stuffing at 100% as my FHXLs sit in the corners of an alcove in the room.
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File Type: jpg fhxl full vs 50% stuffing below driver.jpg (125.4 KB, 70 views)
File Type: jpg fhxl full vs no stuffing below driver.jpg (128.1 KB, 69 views)
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