Zaph L18/27TBFCG design questions

[Dave Bullet]

Is it ok to use a 2.25mH inductor for L0? (ie. design calls for a 2.2mH inductor - will the extra 0.05mH be significant?)

What are the cabinet dimensions? (unless I'm blind, I couldn't find them on the design page)

What are the tweeter / woofer positions (centre) relative to top of baffle?

and left field....

Zaph,

I'm quite keen on trying a Seas metal cone design - but want a higher efficiency one. Have you considered a 2.5 way or MTM Seas design?

Cheers,
David.

[Zaph]

Hello,

Box dimensions are in the enclosure section linked like this:
"[image] - Parts Express .5 cu ft box, w/baffle layout"

I have a 2.5 way TMM design but I haven't given it out because I've never built, tested or listened to it. If you'd like to try it anyway, I could post it, but no guarentees. Of course, I have no guarentees on any of my projects, LOL.

[wa4swj]

Hi John,

I built a set of your L18's and just sent you a picture a few days ago. I would be willing to try a 2.5 TMM design of yours. I've been looking for something else to build and I like your designs very much. My L18's are wonderful. (Wish I had the equipment to measure them like you have.)

Thanks and best regards and happy holidays!

[wa4swj]

Sorry for the additional post: Parts Express has cabinets on sale right now so if it would fit into one of those that would be great.

Thanks again,

[Paulus1981]

Originally posted by Zaph
Hello,

Box dimensions are in the enclosure section linked like this:
"[image] - Parts Express .5 cu ft box, w/baffle layout"

I have a 2.5 way TMM design but I haven't given it out because I've never built, tested or listened to it. If you'd like to try it anyway, I could post it, but no guarentees. Of course, I have no guarentees on any of my projects, LOL.

Hi John,

would such a 2.5 way also work when the second L18 is replaced with a L26 from Seas?

I've already built enclosures for these, now they are playing as a subwoofer with my monitors which is a waste of the beautifull units.

The built enclosures are 32 cm wide and 75 cm high.

best regards,

Paul

[sreten]

Hi,

Assuming Zaph's TMM design is based on the TM design
measurements it would drop into the PE 1 cu ft cabinets,
the extra 1/2" of baffle width not being a major issue.

/sreten.

[JasonB]

Originally posted by Zaph
Hello,

Box dimensions are in the enclosure section linked like this:
"[image] - Parts Express .5 cu ft box, w/baffle layout"

I have a 2.5 way TMM design but I haven't given it out because I've never built, tested or listened to it. If you'd like to try it anyway, I could post it, but no guarentees. Of course, I have no guarentees on any of my projects, LOL.

John,

I wouldn't mind having a look at that TMM design, If you don't end up posting it is there any chance you could email it to me?

Thanks,

Jason

jaybrandt@hotmail.com

[Zaph]

I almost forgot to post this for you guys.

Here's the image:
L18 / 27TBFCG TMM crossover

Build it with the same baffle width and driver locations, and just stick the 2nd woofer below the 1st. I think with this design, I'd go for a bit more volume if you're building from scratch, like maybe .65 cu ft per woofer and tune the port 3hz lower.

Looking at this crossover, I kinda see why I never published it. It lacks the elegant simplicity of the TM version. It uses the brute force method of making the woofers behave. Not only is it complex, but it's going to be expensive as hell because low dcr inductors are required. You have to meet or beat the dcr values in the woofer circuit. I don't design this way to often - I cheap out when possible in the crossover. But if I recall (from 2003 when I did this) the design needed low dcr all around to work well.

It's a full baffle step design with relatively high output, suitable for medium to larger rooms, and at least a few feet away from corners or walls. Sensitivity is roughly 87 or 88dB. Impedance is a solid 4 ohms nominal with a minimum of 3 ohms in the midbass. This would probably work with a tube amp if it had 4 ohm taps. It hasn't been tested, so build at your own risk. But if you do, be sure to send me a picture.

[Dave Bullet]

Hi Zaph,

I really appreciate the time you've taken to respond to what I thought was a real left field question.

I'll study the crossover in more detail. I'm quite keen on building the TMM version. Just have to move into a new house and do a few things, but will put it on my next project list.

Thanks very much,
David.

[Dave Bullet]

Hi Zaph,

Just noticed there's a 112 uF cap (C6) on the woofer circuit.

Could you get away with a bi-polar cap (paralleled with some polyprop caps to make up the 112 uF?)

I've read never to use bi-polar caps in speaker crossovers, but since it isn't in the signal path, wondered if it made less or no difference?

Thanks,
David.