C17x4 speaker project - active XO

[skogs]

Hei, i mentioned in another thread a while that i was in the process of designing a speaker using four 6,5 midwoofers and a tweeter.

But now the project is really starting to take shape, and i could need some of you expertice.

I've built a 4th order active XlO @2500, and added a 6th order subsonic filter at 40hz. The filter measures perfectly, and the phase between drivers are excellent. The speaker will be driven using 4 of the channels from a 22kg monster surround reciever. Denon AVC A10S.

This graph shows two of the mids together with a Monacor tweeter mounted on a waveguide. Two main problems occur: spl is down some 12db(!!) at 150hz, and tweeter is boosted way to much at 3,5khz by the waveguide.


So here is my questions:
Tweeter: How much hassle to remove the 3,5khz peak? Would i be better off just dropping the waveguide? Should i use a different tweeter?

Midbass-drivers: How to best attack the problems in the midbass?

And another important issue: Driver placement! WWTWW, WTWWW or TWWWW? I would prefer getting away with a 2-way system, rather than 2,5-way.


XO measured directly, Black line is my soundcards respons.
http://avforum.no/forum/attachments/...lt-direkte.jpg

[PeteMcK]

TWWWW
Re:' I would prefer getting away with a 2-way system, rather than 2,5-way' - why?
2.5 will give you full baffle step & a better balanced system... OK, It'll make a fully active system a bit more complex though, perhaps you do this using a 1st order passive line level xover for the .5 woofers. Personally. I'd xover the tweeters passivly, the main benefit from going active comes from the low-mid crossover...

[skogs]

Using four 6,5" gives alot of output, and would require a lot from the tweeter, that's why i want to cross over with as high order as possible. LR4 would be rather difficult getting correct and with good phase respons.
Making it 2,5-way would require two more dedicated amplifier channels, and i think it would be a shame wasting 130W per 2 tiny 6,5".

But in the end you are probably right. I'm currently building a TWWWW baffel, and i can try both 2-way and 2,5-way. Maybe i could even try passive tweeter xo, in that case i could actually use the amplifiers in my main surround amplifier on them.

Do you think passive HP against active LP, would be a good idea? And i'm thinking about power handling, phase respons and matching with the woofers.

[skogs]

Got a TWWWW up and running now. The midbass is awesome, but the overall sound is really "screamy" (in lack of a better word). Voices are very pronounced and sounds unaturally high pitched. Heavy guitar-riffs sounds very harsh and annoying at slightly loud levels (90db++).

Any idea of what could be causing this? TWWWW-setup? distorting tweeter?

[skogs]

Could really need some help here people. Any ideas why the sound can be so harsh when it measures so beautiful?

[doug20]

Originally Posted by skogs

Could really need some help here people. Any ideas why the sound can be so harsh when it measures so beautiful?

Did you do off axis measurements? Could you post your measurements? Im curious to why the harshness doesn't come up in your measurements.

[skogs]

Here's the response measured from sweetspot. From this plot you would think that it sounded very warm, but it does certainly not.

[doug20]

What about impedance, phase, off axis, distortion and other more important measurements?

[skogs]

The reverse null is not as it should be, only a few db down at the xo. But i get ca 4db "boost" at the XO-point between bass og tweeter, so the phase cant be that bad. Off-axis measurements becomes very inaccurate, as the room is far less than optimal, so i cant tell if its the speakers or the room that causes the differences.

But i havent really measured any of it properly, except the reverse null. If you could elaborate a little how these parameters could affect the sound, that would be very nice of you. I would greatly appreciate it!

Edit: The sound sounds thin and harsh even at levels under 80-90db, could it be distortion at these low levels?

[PeteMcK]

some possibilities - perhaps the drivers are crossed over at the wrong point, do you have links to data sheets? or it may be simply that there is not enough attenuation on the tweeter... Have you dealt with baffle step in your filter?
re: 'Heavy guitar-riffs sounds very harsh and annoying ' - don't they always? maybe it's your test music, try something less complex, Heavy music is one of the hardest to get a good sound on...