HI-VI M8A 8" how good are this drive??

but im most interested in the 8" drives from hivi...

Those are the M8a. Browse around that forum and you will find several projects using them - WT and WTW in ported boxes as well as the big dipole where they are used as mids. Good drivers but they need to be crossed pretty low because of a resonance at about 2500 Hz. Jon crosses to the tweeter with a quasi-8th order Cauer elliptic filter at about 1250 Hz.
 
Im Using the M4N along with the Tang 2" with phase plug in a .75 ft^3 ported cabnit and i am shocked at the bass extention of the little 4" driver. Im shockes that it has somthing you can almost ;) call punch down to 45 hz. I am a big fan of hivi now, for the price there better than vifa imho.
 
All the projects using the M8a detailed on HT-Guide and the links in my signature started from an article in the Sept/Oct/Nov issues of AudioXpress. The M8a-MKIV. That design is ported. And several people have built other ported versions.

We've also used the M8a drivers in several dipole designs. They are VERY good drivers for the money

Below is the original posted TM design that was detailed in AudioXpress

M8-IVNoGrilleSS.jpg


Below is copy made into a floorstander

[IMGDEAD]http://www.mts.net/~glendap/images/update/front_sml.jpg[/IMGDEAD]

Below is the M8a-MKIII it has a Focal TC120 tweeter

[IMGDEAD]http://home.comcast.net/~audio-worx/MkIIIFrontNGS.jpg[/IMGDEAD]

Below is a variant, it's ported and is using a Hales tweeter

LivingRoomW_DrvrsSS.jpg


The speakers shown below are ported

[IMGDEAD]http://home.comcast.net/~bcwwkg/photogallery/photo18041/MTM-Finished-007.jpg[/IMGDEAD]

Avro Par't design dipole

[IMGDEAD]http://home.comcast.net/~audio-worx/loadedArvo.jpg[/IMGDEAD]

An 'extreme' version of the Arvo dipole

[IMGDEAD]http://home.comcast.net/~audio-worx/ArvoUltra1.jpg[/IMGDEAD]

Click on the link to see another ported MTM design.

attachment.php4


There are 1/2 dozen or so more designs we've created using the M8a driver. But I think this is enough of a sample to see that we think it's a good driver in many applications
 
Here's a link to the important files that relate to the M8a-MKIV version Vifa XT-25 tweeter (there are other tweeters that will just drop into this design, one is the SS9800).

If you use a sub a sealed box is fine. If you're not using a sub, I recommend going ported to lower the excursion of the driver.

http://pwp.t-3.cc/ttriff/M8aArticle/

If you want all the R&D info related to the design, buy or borrow the back issues of AudioXpress.