Zaph's SR71 help needed

[Bylie]

Hi,

Ok here we go again, another diywanderer asking to adjust a design to fit his needs .

I've got some Seas 27TBFCG's lying around collecting dust and wondered if this design could also be made to work with those. If i look at the measurements of the 27TBFCG vs 27TDFC, they are almost the same. Is this in any way a drop-in replacement? I know from Zaph's blog that a few months back he had not yet decided which one to choose for this new design. in the end it turned out to be the 27TDFC because of the looks.

But is the 27TBFCG in any way usable in this design?

Note : I know this is yet another request asking to adjust an existing and final design but I'd be a very happy camper if I could put those 27TBFCG's to better use...

[DcibeL]

You could use them, but the top end of the response will be shallow without modifying the crossover. Zaph has compensated for the rising response at high frequencies for the TDFC, this response characteristic does not exist on the TBFCG.

Looking at the response graph at Zaph's site, you may want to pad the tweeter an extra dB or so as well in the crossover.

[DcibeL]

Just thought I'd add that Zaphs L18 design uses the 27TBFCG tweeter, so you could go that route.

[Jay_WJ]

You can use the 27TBFC with the shelving components (C4 and R5) removed and the current 4 ohm padding resistor (R0) replaced by a 5 ohm resistor.

[tktran303]

The Zaph All Metal System is a nice budget 2-way to build.

I onced switched the TDFC for the TBFCG. There are minor frequency response deviations in the top octave, but the biggest difference is the drop in sensitivity, which was glaringly obvious, so you would want to correct for that first.

[Bylie]

Originally posted by Jay_WJ
You can use the 27TBFC with the shelving components (C4 and R5) removed and the current 4 ohm padding resistor (R0) replaced by a 5 ohm resistor.

That's a nice surprise, it actually makes the crossover simpler when using 27TBFC instead of the 27TDFC.

Now another thing, I visually like fullsized speakers more than standmounts. Would it have a dramatic effect when making these as floorstanders while keeping all the crucial dimensions the same (interspeaker distance, cabinetwidth, tweeteroffset)?

[Bylie]

Originally posted by tktran303
I onced switched the TDFC for the TBFCG. There are minor frequency response deviations in the top octave, but the biggest difference is the drop in sensitivity, which was glaringly obvious, so you would want to correct for that first.

I thought the 27TBFCG actually had a little bit more sensitivity in the 2K - 10K range which is why "Jay_WJ" suggests using a 5ohm padding resistor instead of a 4ohm.

[Bylie]

Originally posted by DcibeL
Just thought I'd add that Zaphs L18 design uses the 27TBFCG tweeter, so you could go that route.

Indeed I had them in mind, but the new Seas ER18RNX seems to offer more performance for about the same price. I'm also a bit weary about using a design from 3 years ago using a metalcone driver because of speaker revisionchanges. The precisionstrike notch at 7kHz could be rendered useless if the breakup for instance would have shifted (which we actually saw happening in the excel range).

[Jay_WJ]

Originally posted by Bylie

Now another thing, I visually like fullsized speakers more than standmounts. Would it have a dramatic effect when making these as floorstanders while keeping all the crucial dimensions the same (interspeaker distance, cabinetwidth, tweeteroffset)?

Zaph's design uses more than 6 dB baffle step compensation (BSC). If you make it in a floorstander, it will have even more BSC, due to extended baffle height, resulting in too heavy tonal balance. It'll be more so if your listening room is somewhat small. Zaph provides a reduced BSC option but the reduction is too large in my opinion. And it has another problem. Read my comparison section of my ER18RNX 2-way design page (http://www.geocities.com/woove99/Spk...18RNX_2Way.htm). I suggest trying my crossover in your case. I can provide a TBFC/G version if you want me to.

[Bylie]

Originally posted by Jay_WJ
I can provide a TBFC/G version if you want me to.

That TBFCG version would be nice.