Help tuning my FE127e fullrange ref MLTL - diyAudio
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Old 2nd April 2008, 11:28 AM   #1
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Default Help tuning my FE127e fullrange ref MLTL

I have recently completeted a pair of Diyaudio fullrange reference MLTL monopoles.

I am not blown away by them, and I am wondering what the fuss is about fullrange loudspeakers. Maybe they need tuning?

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I have lined the cabinets with traditional felt (10mm est) on the rear of the cabinets, and synthetic felt (2x5mm est) on the fronts. I have stuffed the top 3/4 of the cabs with three layers of MDM3.

I have made the vents 50.8 mm long x 51mm diameter.

Ouch. ****, ^^^^, """", !!!!!!!!. I have just noticed from the original drawings that the monopoles should be 38.1 diameter. This is very annoying as I spent hours cutting the holes to 51mm (dipole diameter) with about 20 sessions each using a specially purchased Forstner bit. The idea was to avoid plastic tubes.

Is this likely to be responsible for the muddy sound?

The top end is good.
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Old 2nd April 2008, 04:09 PM   #2
chrisb is offline chrisb  Canada
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ouch, that is a lot of time & materials to invest in a project that leaves you underwhelmed.

As best as I can recall, there were many variations on enclosure dimensions, driver placement & vent tuning this series. Of the few that I built or heard, my personal favorites were the folded monopole which I made into a short, angled floorstander for my mom, and Scott Dunn's bipoles.

Yes, if your port is oversized, the tuning will definitely be off. How are these mounted? If the vent is downfiring, you could possibly line the inside of the port with a cut length of ABS pipe, hot glued in place - out of sight, etc......
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Old 2nd April 2008, 04:32 PM   #3
SCD is offline SCD  Canada
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Default Your hole is too big!

Yes you have a bit of a pickle here.
I was thinking the same thing as Chris. A liner to reduce the tuning diameter of the port will solve the problem.
Another thought once you get that dimeter solved is how is the port loaded I have a sneaking suspicion that the presentation does not load the floor or a wall. If this is the case the bass might be a little thin.

Also these speakers do like a current source more than a voltage source. Nelson Pass has a good paper on this topic that is worth the read. A Tube amp or an F4 ( or other current source) are quite wonderful. There are other amps that perform quite well, these are the ones I know about.

Good luck
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Old 2nd April 2008, 04:43 PM   #4
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These are designed to be wall mounted with the port facing down.

I have already been to the plumbing shop today, but it was closed.

I will insert a piece of pipe of the correct length and internal diameter and fill the gaps with silicone, and report back.

Perhaps we can get on with tuning after that.

SCD. these are to be used with my digital amp based system, see below. there is a pair of subs to follow.

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Old 2nd April 2008, 05:00 PM   #5
chrisb is offline chrisb  Canada
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Once you get the tuning / installation kinks worked out, I'd think it very likely you'll understand what the "FR" fuss is all about.
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Old 2nd April 2008, 09:23 PM   #6
GM is offline GM  United States
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Hmm, it's a bit late, but I calc'd an alternate driver position if anyone's interested, though with such small cabs it's debatable as to how audible the difference might be:

Monopole: 11.09"
Bipole: 12.09"

One thing's for sure though, even wall mounted the monopole will still probably need some BSC at this low tuning (for the driver).

GM
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Old 7th April 2008, 02:53 PM   #7
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http://www.diyaudio.com/forums/attac...amp=1102456925

I am struggling to find some pvc or similar tube with 38mm (1.5")internal diameter. 35mm is the nearest in the UK, so far.

Should I keep looking, or adjust the length accordingly. If so please could someone do the calculation for me (with 35mm tube) or point me to the software, so that I can have a go myself.
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Old 7th April 2008, 10:55 PM   #8
G is offline G  United States
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Quote:
Originally posted by dublin78
http://www.diyaudio.com/forums/attac...amp=1102456925

I am struggling to find some pvc or similar tube with 38mm (1.5")internal diameter. 35mm is the nearest in the UK, so far.

Should I keep looking, or adjust the length accordingly. If so please could someone do the calculation for me (with 35mm tube) or point me to the software, so that I can have a go myself.

Just adjust the length. All you are doing is looking for the correct volume of the tube. If the diameter is narrower then make the length longer. Look for a volume calculator on the web that calculates the volume of a cylinder.
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Old 8th April 2008, 01:39 AM   #9
GM is offline GM  United States
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Hmm, it's not about matching the vent's volume. For a given Fb, a smaller diameter vent requires a shorter one.

Anyway, RonE has periodically posted a vent scaling solution:

L2 = L1*(D2^2/D1^2), where D2 is new the diameter and D1 is the original diameter.

GM
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Old 8th April 2008, 05:35 AM   #10
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I have a pair of the diyRef bipoles (in the mezzanine)... i find them a bit tubby in the bass, but this often seems to happen when you try to max the bass with a small FR.

I REALLY enjoy them as fronts for the HT.

dave
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