Sneak peak at my Fe166ESR project and a 'Pass' question.

[one1speed]

Illusus

Question for you. You say this is the best system you've had in your place so far. Can you tell me what you've had to compare to and what you like better about this system? I'm wondering if you've compared to a BLH or similar. Thanks!

Layne

[Illusus]

I was thinking the same mr.Pass, afterall, I can build the amps to run balanced mono and SE stereo. Thanks for your help.

My speakers of late were FE206E in BLH...I also had the same drivers in ML TL cabs. They were both good but the ML TLs sounded a little too much like medical equipment (sterile, cold). The horns sounded very real and live but the sound would often get conjested, I had a hard time hearing toms and kick drums during semi-busy rock music. Orhestral pieces were a wall of sound, all low tones were only peeking out from behind the midrange. I tried many corrective circuits on both types of cabs, some good some bad. Of course, YMMV. I had guest listners in house quite often, most preferred the BLH over-all, but most liked the low end from from the TLs.

Before the 206 projects I had a slew of two and three way speakers, both DIY and commercial. All were so so.

How do these compare? It's hard to describe, the sound is just so different. When a kick drum hits it feels like you're standing right next to one. Low bass is fantastic, tight and tuneful. The imaging is already better, but I need to attenuate the back wave a bit, it seems to be adding an excess of confusing ambience to the stage. There is also a new level of 'realness', openness maybe? in the whole packge, especially the midrange, it really sounds natural and delicate. Only problem so far is the tiny sweet spot, it's about the size of a small beach ball, I can definitely tell when I poke my head out of it.

I really like the FE1666 drivers, very detailed, natural sounding. I'm amzed everytime I listen and hear nuances I've never heard before, new layers of harmonics, tiny details...I can't wait till they break in, if they're anything like the 206 I'm expecting some relatively big changes.

[one1speed]

Thanks much, that's what I was looking for. Best of luck with it!!

[5th element]

Have you factored bafflestep into any of this?

I see you mention the woofers sensativity is 100dB but after the conversion into 4pi you are really looking at 94dB. You are already about 3dB down at 200hz anyway due to this, coming full circle at about 100hz. I have estimated that your baffle width is about 18".

[Illusus]

you were pretty close on your estimate...they average about 18" near the woofer.
I thought about it a little(baffle step), I thought that the drop from baffle step would help even out the efficiency mismatch, I was wrong, upon first impression I was stunned by the gobs of bass but that's only because of lack of reference, my last speakers were very thin by comparison. I'm far from done though.

Yesterday the efficiency mismatch became very apparent through listening to frequency sweeps. I hooked up my warble tone generator(only tone generator I have-too lazy to burn a disk) and went through the frequencies. when I got to 200HZ there was a jump in volume, at least three db, enough to be obvious anyway. They sounded pretty flat in volume from 32Hz to 160HZ, then the jump in volume and again very flat up to about 16kHz. Inaudible at 20kHz, and I know I can hear that high, when I was foolin' around with FT17H STs I was hearing 20k, it's an annoying test tone, my cat went really nuts at 22kHz and above, I thought I could hear 22k but wasn't sure, I was definitely aware of it though.

So...last night I rigged up a pair of L-pads I had kicking around and toyed with them untill everything sounded flat, much better over-all but the bass sounded a bit bloated...I knew I over stuffed so I removed over half of what I had in there, much better. I mocked up some panels made of thin, stiff fiberglass insulation behind the OBs(I loosely boxed them in, I tore half the thickness off paper backed insulation panels) to damp the rear wave, it was causing a slightly confused sound, the fiberglass cleared it up a lot with no immediately apparent drawbacks - the midrange still sounds effortless and detailed but no more of that overly rich ambience. Imaging improved.

Now I wonder if I should work on a BSC or pad the upper driver, I don't really want to keep the L-pads in there. I'm in no hurry though so lots of time to spend in theory before making the choice.

[5th element]

Well the good news is the open baffle speaker does not suffer from bafflestep losses because the driver radiates in 4pi all the time. However after the width of the baffle you get a loss of 6dB per octave and then 18dB per oc after driver resonance (IIRC), 50hz in your case. Im sure you know all this.

The way I would approach this is to cross the openbaffle to the bass driver at about 100hz, but in this case that is not possible, I would also use active filters just because I have them available to me. Shaping the lowpass on the bass driver should be able to compensate for the rise in response without having to add lots of compensation in other areas.

Once the low pass has sorted out the bafflestep loss on the bass driver there will be about a 1dB mismatch between the two drivers. Dont worry about this, we all get a small amount of room gain even if the speakers are placed free of the walls.

Assuming the JBL is flat for atleast 2 octaves past xover frequency and that impedance is constant in the xover region a textbook LWR4th order at 180hz is not far at all from an acoustic slope of the same design.

If however you are using a 2nd order slope then a text book crossover is much further from the acoustic. Both can be manipulated to provide almost perfect roll off.

[Illusus]

just to play around with BSC I'm going to put in a line level circuit to-morrow, the corner is at about 85Hz...I should have no problems finding the parts in my bin.

[planet10]

Originally posted by Illusus or go active and bi-amp

At that low of a frequency active sure makes a lot of sense... even if just PLLXO.

dave

[Illusus]

That's pretty much the conclusion I'm arriving at. I will still configure the amps for use as both SE and Balanced. I'll participate in the MOX group buy if it goes through, till then I'll go with PLLXO. Now, what to do with those giant parts I bought?

If I use the preamp (BOSOZ) in SE mode, I just groung the unused inputs, right?

BTW...does the MOX support BSC as is or will I have to use the proto section?

Dave - check your eMail.

[one1speed]

if there's anything more going on with this. Real interested to see where you land with this one, as I still like this direction...