FE103E Bipole project

[RtV]

I'm a newbie to speaker making, so I can use guidance, if there's some to be offered.

I'd like to build a bipole FE103 ML TL for use with a Sonic Impact Class T amp. Bipole, because I'd like to minimize circuitry (for baffle step correction) and enhance sensitivity and bass for the 6 watt amp. FE103 because it seems to be universally liked (except by basshounds). I'm willing to accept whatever bass extension I can coax through good cabinet design, while optimizing other parameters.

Scanning the archives I've found several conflicting measurements for the optimum cabinet size and port hole (as an ML TL). So I'd like to get that straightened out. Also, I'd like to know if anyone has tried placing the drivers off-center, and if so, how that might change the cabinet design.

[Scottmoose]

Horizontally off centre -no difference at all to what happens inside the cabinet. It might improve imaging if these were monopolar, but they're not, they're bipolar, and therefore have many of the properties of a dipole design. So probably not worth the effort.

As for modelling the thing: use Martin's MathCad worksheets if you aren't already, with these changes:
http://www.quarter-wave.com/General/Two_Drivers.pdf

problem solved. Oh, by the way, I'd suggest the FE107E rather than the FE103E in a TL.

Best
Scott

[gmilitano]

Originally posted by RtV
I'm a newbie to speaker making, so I can use guidance, if there's some to be offered.

I'd like to build a bipole FE103 ML TL for use with a Sonic Impact Class

Take a look at Tim's site.

http://www.timn8er.com/

He has put togther an FE103E Bi-pole (BP-103)

The BPTL and BV-1 may also be suitable with the FE103E.

[RtV]

Thanks Scott for your reply:

It might improve imaging if these were monopolar, but they're not, they're bipolar, and therefore have many of the properties of a dipole design. So probably not worth the effort.

The only purpose in locating the drivers off-center was to reduce cabinet resonance. I understand that the imaging of bipoles is not their strong point.

I see that Martin K's worksheets provide the option of locating the drivers off-center vertically. So I will look into using that worksheet once I figure them out.

What feature of the 107 leads you to recommend it for a TL? I didn't think I would need the extra shielding, although the extra dB of sensitivity is nice. Do they sound as nice? Many threads have waxed ecstatic about the sound of the 103's.

Thanks also to GG:

I have loooked at the BP-103 and in fact have noted that the measurements of the cabinet differ from Tim's recommendation in another (earlier than the BP-103, I think) thread. I was hoping he'd explain what caused him to change the parameters.

Have dl'd mathcad and the worksheets and the worksheet instructions. Unfortunately may not get to study them until the weekend. I understand some of the Thiele-Small parameters, but not all yet. So my learning curve is still on the steep end.

Randy