diy studio monitors

[brsanko]

I've come up with a plan for a pair of studio monitors. Using the HI VI f8, and the HI VI RT2C planar tweeter because of their incrediblely flat frequency response. Now the cabinets I want to build would be 16"wx10"dx24"h outside dementions. Giving me an internal volume of 1.64 cu ft, and with a slot port of 8.5"dx12.825"wx1.5"h would give me bass down to 32Hz so I wouldn't even need a sub. These should fit nicely on my studio table and just by coincidence fit the golden ratio almost perfectly. I would need some help designing the crossovers but I think I want to do first order around 2000hz and a 4 db attenuation ciurcut for the tweeter. please let me know what you think.

thanks
Brett R. Sanko

P.S. my internal volume includes the port I don't know whether it should or not.

[Iain McNeill]

A 1st order crossover will theoretically give perfect reconstruction and superb transient response however, it places the greatest demands on the drivers. The drivers need to be 0deg phase and flat response for about 2 octaves either side of crossover. Usually they are not and this causes magnitude and phase errors around the crossover point.

See if you can find Richard Small's AES paper on constant voltage crossovers for an excellent discussion.

wrt the port, you need to subtract the volume of the port plus 5% or so for fringe effects to get the true internal volume. Don't forget to subtract the volume of the drivers as well.

[tinitus]

I have been looking at the RT2II which is useabledown to 2khz, but may be a bit optimistic

The RT2C is only recommendable down to 3khz

That is from specs chart and I suppose this is with 2.order filter ... 1.order 6db wont do at these frequencies

[brsanko]

Thanks for the input guys. The response of the woofer gets a little weird above 2k so I don't know if I'd be better off raising the x-over point or going with 2nd order.
As far as the volume issue with the port I can just make the cabs 3" taller thats no big deal. please keep the comments coming.
Thanks

[brsanko]

actually the spec sheet says recomended x-over point >1700Hz so 2000Hz should work but like you saidonly 2nd order. I definitely don't have the 2 octives of flat resonse below that so I guess a 1st order wouldn't work too good at this frequency. The woofer response gets ugly above 2500Hz so I don't want to go to high. here are the response charts. Let me know what you think the best solution would be. Maybe I need to pick a different tweeter alltogether.

[tinitus]

http://www.swanspeaker.com/product/htm/view.asp?id=11

Only RT2C I see on Hivi site, and it still say min. 3khz ????

Looking at PE site it says 1700hz ....

[brsanko]

look at the pic in the post directly above yours it's from parts express it's the manufacturer's spec sheet.

[tinitus]

Obviously old spec sheets saved at PE I suppose specs on Hivi site is up to date

Response curve seem a bit different too ... maybe its an older model ... weight is a bit different too, so I suppose it has been changed a bit

But without proper xo nothing will work

[brsanko]

Well I wasn't aware of the 2 octive rule before. I think it would be tough to find a tweeter that I could x-over at 2000Hz with a first order design, and I know I don't want to go 3 way, so I guess I better start looking at drivers again. I'll just forget about using the bose boxes and maybe look at 6" woofers.

[tinitus]

A Peerless SLS 10" in 50liter closed and a Fostex FE87e might work with 6db filter ... but will it work? ... I would think it depends on the small fullrange about which I havent got a clew
but there are also TBs and Jordan ... and FR125, but low on SPL ... some like all those small fullrange drivers ... others think they dont live up to their reputation
You might be better off chosing a well proven design