Zaph L18 monitors

[DIFORCE]

Recently I've started building these according to zaph's schematics ,following them closely.. However My room is rather small and the speakers will be placed next to a wall by somthing like 30 cm ... I've read somwhere about the reduced baffle step version of his design ( that he does not share ) ,But i think I found it here :

ZAPH L18, BSC issues.

If someone could verify this is the updated one cheers

also another question ,I want to make two retangular front ports below the woofer . Retangular ones ... How to I calculate this ? WinISD does only square and circle ... I can fit the circle below in a ProAc studio'ish kind of way but .. I dunno doesn't seem right.

Any ideas ? Also could use some hints on the bracing

( The image does not show the length of the port ... It is allmost all way in leaving 7 cm from the back wall If i use a single round 50mm port )

[DIFORCE]

wow no input anyone ?

[mondogenerator]

i dont know the original zaph design personally although i may have seen it as he is on here alot,

the port will tune the box to the same frequency if it is of the same length and also the same cross sectional area, as the same mass of air will be contained within the tube.

you can make your port whatever shape you like as long as you adhere to:

1: the area of the port tube MUST remain the same as the round port you are trying to replace, and the length muct also be the same.

2: If making the port a 'slot' shape, the dont exceed um...say 5:1 ratio in the H and W dimensions for the port.

[sangram]

Zaph had to redesign the crossover to the port on the front of the box - I can't remember whether that was here or HTguide forums, but he had actually put a port next to the tweeter (IIRC, not sure) on the front.

That XO looks correct and AFAIK the last update from John on the reduced BSC.

[DIFORCE]

I considered the port to be near the tweeter as there is more room there for a bigger radius port. I'ts very hard to design one port below the woofer with less then 0.20 Vent mach , No room

In the picture you can see the 2' Inch port below and it barley Fits ( dont know if it will with absorb mats inside ) and It gives me the minimum of 0.16 Vent mach port noise so I dont know about that ...

2 ports look ugly no thnx.

Edit: actually I tried to place the port near the tweeter , even less room then below the woofer ... on top of that I seriously need to move the entire baffle "up" to the point the tweeter VC on the inside barley tauches the roof inside Wierd ...

According to zaph and his double 1' inch port ... He gets around 0.24 vent mach .. That is way over the green zone , What about that

[sangram]

At what power/excursion are you getting those numbers? Does the woofer reach its travel limits before the port starts chuffing?

[DIFORCE]

I only realised these numbers of VENT MACH are at max excursion
Since I'm pretty sure I wont be getting anywhere near there Im safe using a 2 Inch port on the front.

They will be Used for desktop monitoring ,At 1m away from the listening point and Facing directly the listener ( Toe'd in ) and around 35cm away from the back wall. I understand certain BSC is needed but I've read somwhere Zaph's redesign offers too much BSC so I think I need less ... somthing about zaph's BSC is 6DB and I someone else designed a 3.5DB and he thinks I'ts better.

Any Ideas ? Only about the BSC version...

[sangram]

Yups, thought so

There are a bunch of crossovers for those drivers out there - I think Tony Gee has a few.

As you drop the inductor value, my understanding is that the notch filter will shift slightly. I'm not so sure about this. But the notch is absolutely required. I've tried to play the driver raw and with some improvised crossovers, and it sounds pretty trashy. With Zaph's XO, it's butter-smooth.

Be warned that even with low-BSC speakers, you'll still need some more distance from the back wall. I monitor with a pair of Dyanudio BM6 passive nearfields, and those need their ports stuffed with socks for mixing duty (though it's fine as is for generally listening to tunes).

[DIFORCE]

Any Advice ? This should be the final schematic ,Everything looks fine to me unless there is a problem placing ports so close to the woofer and/or tweeter ...

Heavy "+" shaped Bracing inside connecting all walls exepct the baffle

[sangram]

That answer is a little out of my league, unfortunately. I assume port location will influence the final response - though to what extent I'm really not sure. I wish Zaph were around to post but seeing as he doesn't stop by much I don't know how the output will change.

I might think that with a port that close you'll need a pretty big roundover on the port hole to prevent diffraction, and there may some secondary effects in the midrange due to leakage through the port itself - the exact nature and extent of which I am uncertain about...

I'm certain that the crossover will need some changes with that baffle layout, specially if you're looking forward to a nice and flat frequency response for monitoring.

I would (personally) run them sealed and add a sub, that would solve all the potential issues. It's a little more pricey than pulling them out into the room, though