vifa 8 inch d'appolito?

[bruce ferrara]

Hello,
This is my first attempt at diy. I am a musician not a tech type so pardon simple questions.

I have 4 vifa p21 wo-12 woofers that I came by for a small amount. ..I am wondering if a d'appolito type design would work with these and if so how large a box? vented? sealed?
I have tried to learn as fast as I can ..so any ideas?
Thanks

[tinitus]

I have a little difficulty to choose if it should be sealed or BR

Best would be if someone know of a construction with theese drivers

If not you may have some luck with a small fullrange as mid/tweeter, or a widerange with a helper tweeter

What is you budget

[noodle_snacks]

Ideally, for a d'appolito the crossover frequency should be below one wavelength between the center to center frequencies of the woofer. Assuming a 200mm OD on the woofers, and a 100mm tweeter, that frequency is 1130hz or so (340 / 0.3000 = 1 133.33333). If not below this frequency the vertical polar response begins to suffer, going higher is possible, but as you get higher things get worse.

Incidentally there are not many tweeters that will cross over that low. Crossing over higher would still be a compromise solution. So if i had 2 8ins i'd probably just go TMM. Unless the crossover frequency is low enough in this case, you will also suffer from poor off axis response in the crossover region. (If this is an issue or not this will depend).

[tinitus]

I would suggest to cross between 500-1000hz, a couple of 3" would do that, but I would do a TMWW, tweeter sets in above 10khz, simple 6db filters will work ok

[bruce ferrara]

hey,
Thanks for the replies.

My budget is low.. as I said before being a jazz musican..means small funds but good ears.
This is my first attempt at understanding all that is to know.
I thought D'appolito for the simplicity (so I hear) and the imaging.
But maybe 8 inchers are too big? I know the Eros Speakers I have sen plans for have 7 inch vifas.
If I could know how to figure box size in a way that I could understand would be a good start. the specs on the vifas :

80 watts
RMS/115 watts max * Voice coil diameter 1-1/2-inch * Voice
coil inductance: 90 mH * Nominal impedance: 8 ohms * DC
resistance: 5.7 ohms * Frequency response: 28-4000 Hz * Magnet
weight 24.6 oz. * Fs: 28 Hz * SPL: 91 dB 1W/1m * Vas: 3.99 cu
ft. * Qms:1.60 * Qes: .41 * Qts: .33 * Xmax: 4.00mm * net
weight 4 lbs. Dimensions: Overall diameter: 8-15/32-inch
Cutout diameter: 7-3/8-inch Mounting depth 3-3/16-inch Magnet
diameter 4-5/16-inch Magnet height: 1-3/16-inch
Thanks for the help.
Bruce

[sdclc126]

Would this sort of arrangement work? I've been wondering if you could arrange large woofers and a tweeter in a sort of triangular orientation, with the woofers very close or adjacent to eachother vertically, and the tweeter tucked in next to them - not really an MTM, not really a TMM? Would this placement allow a higher M-T crossover point and eliminate the need for a small mid? Would there be any advantages or a TMM? Any problems?

[infinia]

Hi Bruce,
If you are interested in learning about speaker design, a good book to start off would be "Loudspeaker Design Cookbook",
Can be found at http://www.madisound.com/index.html which has a sale on 6th Edition only $11 (7th ed. is normally $35).
In the mean time you can download a free program called WinISD to help you determine box (enclosure) sizes.
Figure around 2 cu ft for a vented enclosure for your single Vifa 8 inch. With this size enclosure you can get down around 35-38 Hz -3dB (half power).
FYI...note 1 cu ft is around 28 liters.

[sreten]

Hi,

box size for sealed is around 1 cuft per driver, vented around
1.5 cuft to 2cuft per driver tuned to around 30Hz, the size is
a consequence of the relatively high efficiency of the drivers.

TBH the driver is best used in a MT or a large high efficiency TMWW.

The cabinet for an MT would be similar to :

http://murphyblaster.com/content.php...ifa_Tower.html

Note you will need a properly designed crossover for it to work well.

(edit : and I don't mean a cookbook crossover)

/sreten.

[tinitus]

A properly designed crossover ...... you will have to listen to the speaker to do that ..... right

A TMWW setup would need one inductor and two condensator

[infinia]

Hi Bruce,
Probably wouldn't recommend a MTM for a beginner to novice esp with 8 inchers, but it's possible given some work.
So best to stick with a 2 way in a reflex enclosure for this time.

http://www.troelsgravesen.dk/HES_II.htm
The above article looks likely a good candidate for your woofer depending on your room and placement. It has wide baffle and wants to be close to a wall or even a corner to keep the high efficiency. Unlike a slim floorstanding crossover design which throws it away. It features a deceptively simple crossover network given by way of a homemade wave guided/ horn loaded tweeter. The circuit topology at the bottom of the page (Vifa C20, 8"driver) should get you close enough to tweak a few values by ear. I would recommend a few value changes initially depending on the tweeter/WG (waveguide) you end up with and differences with your woofer. I looked at your woofer response and I think it would work fine for this application.
Also see Zaph's web site for some work he has done with a waveguide tweeter which could be substituted for this application.
http://www.zaphaudio.com/Waveguidetmm.html

Start with AN cabinet design and add more bracing and slightly more depth to get closer to 2 cu ft (AN = Audio Note) Tuning port should be around 35Hz more or less.