Active MTMWW

[Forte_II]

Hi, I was hoping to get some feedback from some people here. I am blind and can’t see all the data in speaker software. So if I missed something important let me know.
The speaker will be two separate enclosures. (I may want to go to larger bass drivers in the future.)
The Mid/Hi enclosure will have adjustable feet to facilitate ear to tweeter alignment.
All drivers will be flush mounted.
The finish will be oiled Oak Veneer.

Tentative X-over points are 280 Hz. and 3.2k Hz.
Sensitivity is approx. 89.5db
Impedance is 4 ohms.
Power handling is 150 watts.

I want excellent hi/mid SQ with fast tight bass. Therefore I have decided on the following drivers with an active X-over.
Vifa XT25TG30-04 1" Ring Radiator tweeter

http://www.madisound.com/catalog/product_info.php?manufacturers_id=143&products_id=1181

PL14WJ09 PREMIUM LINE 5" mid-woofer

http://www.madisound.com/catalog/product_info.php?manufacturers_id=143&products_id=1138

Dayton RS180S-8 7" Reference Series Shielded Woofer

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=295-364

Internal damping will be 2" Wedge foam.

http://www.foambymail.com/Wedge.html

Mid/Tweeter enclosure:
Internal volume is 0.821
Board thickness is 0.75 (Front baffle is 1.5)
Port is on rear baffle
Port is 1.62 round by 1.42 long
Tuning Freq is 50.50
F3 is 50.50
Tweeter is centered at 9.86
Mids are centered 3.86 from top and bottom
Outer dimensions:
H, 19.72
D. 13.64
W. 8.33

Woofer enclosure:
Internal volume is 1.445ft.
Board thickness is 1.25 (Front baffle is 1.5)
Port is on front baffle
Port is 2.5 round and 3.64 long
Tuning freq is 40.50
F3 is 40.50

Outer dimensions:
H. 20.5
D. 14.62
W. 8.33

[Forte_II]

I forgot to memtion I have the following equipment for testing.
PC with True RTA
Naty CM2 reference Measurement Microphone
Naty CM1 Phamtom power supply
Behringer mixer/preamp
Behringer active X-over.
3 Samson SX1200 Class A/B 450w into 4 ohms.

[BobEllis]

quick and dirty feedback - Mid-tweet XO seems high. You can go a lot lower with the given tweeter and you'd be happier with the mid staying further away from its upper end nasties and less comb filtering issues.

No need to port the mid enclosure - seal and stuff.

Why not bump up to the 8" or 10" RS woofer? The 8" is a fairly small cost difference and roughly twice the displacement capability of the 7".

You might consider a measurement system that does MLS unless you have access to a large quiet reflection free space. Speaker Workshop is free, and the learning curve isn't that steep if all you are going to do is measure.

[Jed]

Will you be designing your own active crossovers to deal with BSC, diffraction ripples etc. . .? If not, I fear you might take too much of a textbook approach with this design, which rarely results in good sound or at least an acceptable FR.

Those Vifa's look expensive for what you get, old technology with fair motors at best. Look at some of Jon's (search) and Zaph's tests of woofers to get an idea of the better performers. If you like poly cones, maybe the HiVi 6.8 would be a better option-its a good performer. www.zaphaudio.com

[Forte_II]

I am porting the mids for 2 reasons. First I think this will improve power handling. Second I hope to get faster transients. I really like these drivers in a open baffle but I don't want the placement limitations. As for the 3K X-over point. The Vifa is supposed to be good to 6K. I haven't tested them yet but listening to them full range in a open baffle seems to support the claim. Also the 4th order L-R X-over should quiet things well before 6K right?.
I wanted to go with the 8" Datons but the required volume is 4.13ft. almost 3x the volume of the 7s. Besides a sub will do the work below 60Hz or so. Remember I want fast tight bass.
Yes, I am building my own custom active X-overs. 4th order Limkwitz-Riley. The Behringer is just a test mule. I am looking for a 1/3 octive EQ right now. Once I get everything where I want it I will make the X-over.
I am still researching the active X-over. I need to learn more about these. Any good sites out there?
Thanks.
Please keep the suggestions coming I have alot to learn.

[Forte_II]

I haven't bought the Woofers yet so maybe I will just go with a 2 way right now and see what I want to do about the bottom 3 octives later.
Thanks again.

[BobEllis]

Ported for "fast tight bass"? Sealed or open baffle is the usual way of getting there. Sealed RS225s don't need that much room, especially if you are only going down to 60 Hz or so.

With a 280 Hz xo, porting the mids will do little if anything to their power handling. Does your modeling software allow you to incorporate a filter?

Look at that peak in response at 7KHz for the mid - that's a breakup mode (read: distortion) You want to keep that 40+ dB down. There is also a FR bobble around 1500 that I find troublesome. You can do better than that driver.

Comb filtering is caused by center to center spacing being too wide. Do some research in this regard and you'll see why John Marsh uses C-E filters to push the XO points down towards 1500 Hz.

Linkwitz is the best reference. I've tried to distill his teachings about active XOs to almost plug and play here The boards are no longer available, but the spreadsheet should help.

[Forte_II]

Like I said I have alot to learn.
The only software I can use (I am blind and use a screen reading program) is WinISD. The only useful data I get from it is from the text display option. Witch seems to model everything as flat after a point. Usually by 300-500Hz.
Well as for the Vifa PL14I already have them. I will try them sealed and see what I think. The great thing about having a test rig with active X-overs and EQ is that I can try any X-over point I want as well as EQ a flat response.
Then build X-overs from there if I want. Thanks for the response.
Please keepthem coming as I need to be enlightened!