All done - FE107E + Peerless XLS 10" & PR

[Dave Jones]

All done!

Previously I had finished a set of Ariels that a man abandoned, but this is the first loudspeaker system I have designed (with LOTS of help from the folks here) and built. Except that the cabinets are still raw MDF, it's finished.

I know everyone who builds a set of speakers says this, but -- golly they sound great!

The last tweak was to change out two resistors in the Parts Express plate amp, to change the boost to +3 db at 19 Hz. That was not as easy as the instructions would lead you to believe. The hard part was removing the preamp. It was glued around the edges to a rubber gasket about 1/2" thick. There was not sufficient room to get a knife all the way around to cut it loose. I tore up the rubber a little getting the thing off, but some Shoe Goo (tm) set that right.

I'm also running it with a Richter Scale Series Three. I changed the crossover in it to 72 Hz by swapping out resistors.

The bass now integrates perfectly, and it's solid to below 20 Hz.

The final version of the BSC circuit is 2.75mH/5Ohm.

The box for the mains is made from 3/4" particle board throughout. Inside dimensions are H 15 1/4", W 4", D 5 1/4". There is a 1" diameter hole (vent) near the bottom front of the box. The MDF itself forms a 3/4" long port. The speaker is mounted 6" from the top (ID). There's a terminal cup from Madisound on the back of each. The top part of the cabinet is lined with 1/4" felt. Each box is lightly stuffed with poly fiber, from top to about three inches below the driver. The driver cones were coated with three thin coats of dammar varnish, and painted with a thin coat of ivory black artists' oil paint thinned slightly with dammar varnish.

The box for the sub is made of 1" MDF. Inside dimensions are H 24", W 11", D 6.75". There is a 1" board with large holes in it half way up and parallel to the floor -- a "shelf brace". I guess that after subtracting for the driver, passive radiator, amp, and shelf brace, the internal volume is about 26.5 liters. That yields an alignment with an "extended bass shelf." The top of the box contains the driver and the bottom contains the passive radiator (400 grams). The plate amp is from Parts Express, and has been modified to have 3db boost at 19 Hz. Oh -- I put some of those spikey feet on the bottom. Someone here recently said that wasn't a great idea. I might try removing them.

I am using a Linkwitz-Riley 24db/octave crossover at 72Hz. If you use the crossover that's built into the sub amp, a somewhat lower setting would probably be better.

That's it.

[Josephjcole]

How do they compare to your ariels? How much difference did the dammar make (I'm assuming it was the 107 that you dammarred). Have you tried putting in a phase plug? I've heard this can help quite a bit... Does the 107 really go solid to 72hz? I've been thinking recently about trying a 108ez with a helper woofer comming in at about 150~200hz... so I'm quite curious about your exprience.
Joe

[Dave Jones]

Originally posted by Josephjcole
How do they compare to your ariels?

It is hard to say, because I cannot easily A/B them. But I would say the new system compares favorably in several ways. Of course, with the subwoofer, the bass goes an octave lower than the Ariel. The new system also has a very open sound with a huge sound-stage and precise imaging. On the down-side, of course the mains of the new system will not play nearly as loud. (A high pass filter would help there.) I do believe I hear some "shout" on the transients that I don't hear with the Ariels. People who like the Ariels call their sound "very musical", which I interpret to mean undistorted. I also believe the dammar helped the 107's with the vocal transients. But again, I know it is very easy to fool yourself when doing this stuff. There was no double-blind study here.

How much difference did the dammar make (I'm assuming it was the 107 that you dammarred).

See above.

Have you tried putting in a phase plug?

Nope. But I'm willing to risk another $68. Where can I find info on how people have done that in the past? One thing though... I'm not set up to measure T/S parameters. I have to trust the manufacture. That's one reason I chose Peerless for the sub. Everyone says their stuff measures the way they say it does.

Does the 107 really go solid to 72hz?

Martin's software shows it should be down about 3dB at 72Hz, but I suspect the mains actually go a bit lower than the software predicts. I haven't investigated that.
In theory, if the mains were down 3db and the Linkwitz-Riley crossover on the sub put it down 6db at 72 Hz, I should have a small dip there. But in fact there appears to be small peak (in my listening room at least). I don't know why, and I don't know if it's worth investigating. It sounds real good the way it is.

I've been thinking recently about trying a 108ez with a helper woofer comming in at about 150~200hz... so I'm quite curious about your exprience.
Joe

[Timn8ter]

Where can I find info on how people have done that in the past?

I added phase plugs to my RS 40-1197s which are similar to the FE-107.
http://www.alegriaaudio.com/bipole_voigt_pipe.htm

planet10 sells phase plugs on ebay.
http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW

[Dave Jones]

Originally posted by Timn8ter


I added phase plugs to my RS 40-1197s which are similar to the FE-107.
http://www.alegriaaudio.com/bipole_voigt_pipe.htm

planet10 sells phase plugs on ebay.
http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW

How did they change the T/S parameters? I would assume they increase the moving mass.

[Timn8ter]

I suppose the Mms would actually lower since you're removing the dust cap and the plug attaches to the pole piece. Even so, it's so little I doubt that parameter changes.

[GM]

By removing the dustcap and changing the air loading, Qts goes down slightly, improving transient response, though whether it's enough to be audible is very driver/design dependent. What is audible though is that a properly designed plug improves dispersion (power response) and eliminates the comb filtering that occurs due to keeping eigenmodes from developing across the diaphragm.

GM

[jesper]

Hi,
The FE103 should run into x-max limitation at very low volumes if used as low as 72hz without loading. I've tried the fe87 in a MTM with two Seas L15rly crossed at 500hz (4:th order LR). I found my fe87's to be a bit shouty and not as clean as the L15 crossed to scan-speak 9300 at 2khz.
Dammar might help here, what did you use?
Also, my box was only for testing, no fancy interior shapes, just a small 2L square box with some standard damping for the fe87. Do you think the fe's are sensitive in this regard?

/Jesper

[Timn8ter]

What is audible though is that a properly designed plug improves dispersion (power response) and eliminates the comb filtering that occurs due to keeping eigenmodes from developing across the diaphragm.

It definitely worked on my 40-1197s and should work well on the Fe-107. I used a small and very sharp hobby knife to slowly remove the dustcap. It's a bit nerve-racking to slice up a driver though.

[Dave Jones]

Originally posted by GM
By removing the dustcap and changing the air loading, Qts goes down slightly, improving transient response, though whether it's enough to be audible is very driver/design dependent. What is audible though is that a properly designed plug improves dispersion (power response) and eliminates the comb filtering that occurs due to keeping eigenmodes from developing across the diaphragm.

GM

I hate it when I get eigenmodes developing across my diaphragm (burp). :-)

So, I take it I could just try the phase-plugged speaker in the same boxes, and not be guaranteed to fail, eh?