Bi-amp 3-way studio monitor - my first build

[linuslinus]

Hello, I am in middle of designing a bi-amped 3-way near-field studio monitor mainly for light music production and DJ. The HF drivers are some old JBL 1 inch tweeter and woofer that i have grown fond of and can't seem to part with. the woofer is a 8" dayton reference (RS225-8). I choose this woofer from the good reviews as well as the decent fs response. the price is also nice (haha).

Attached is the 3rd draft of the speaker schematics designed around the B&W matrix construction. The brace itself will have finished ends (bull head routing tip) where it does not contact with other pertinent panels. thinking this should reduce erratic internal standing waves. I am also thinking about sectioning each 'compartment' with acoustically transparent mesh so i can play with different poly fills varying in density.

the woofer enclosure, i am thinking should be lined in egg-crate open cell foam. the midrange and HF driver is in a sealed and separated egg-crate lined enclosure filled with stuffing.

the port is a basic 3" inch PVC tube with rounded edge (filed down) wrapped in polyurethane foam sheet (20-25 hardness, i just have laying around) to control if any structural resonance.

will this work or all these theoretical thinking is just too much forum reading?

advice please especially concerning the dampening.

[mdocod]

I'd want to do some more research regarding the effects of driver placement like that.

I believe, based on my limited understanding, that the proposed arrangement would cause a very narrow "sweet spot" in the horizontal plane but a relatively wide "sweet spot" in the vertical plane, which could work well if you expect the speakers to be more above or below the listening position but always pretty well "pointed" at the listener in the horizontal plane.

Also... To make a "studio" grade speaker is going to require that you have accurate driver information to model the x-over with. Without SPL and impedance charts for each driver in the system, achieving anything remotely close to flat is very unlikely.

Eric

[linuslinus]

Originally Posted by mdocod

I believe, based on my limited understanding, that the proposed arrangement would cause a very narrow "sweet spot" in the horizontal plane but a relatively wide "sweet spot" in the vertical plane, which could work well if you expect the speakers to be more above or below the listening position but always pretty well "pointed" at the listener in the horizontal plane.

Also... To make a "studio" grade speaker is going to require that you have accurate driver information to model the x-over with. Without SPL and impedance charts for each driver in the system, achieving anything remotely close to flat is very unlikely.

Eric

the speakers would probably sit horizontally with in arms distance from me.

the speaker will have a passive 2-way internal cross-over for the HF and MF drivers. this speaker will be driven by a active cross-over with 100watt amp for the MF/HF and a 200watt amp for the woofer. a 32 band equalizer will also be set up and i will probably do a room/speaker sound analysis from HOLM Impulse freeware. the MF/HF 89db and the LF is 86.2db. I am crossing my fingers that the vented enclosure can boost the woofer's efficiency to +3db.

http://www.daytonaudio.com/media/res...ions-46153.pdf
above is the PDF detail of the woofer. unfortuately, i don't have much info other then what's below ( eventually i will replace them, just not now )

JBL GTO5.2c
5.25 inch woofers
1 inch titanium tweeter
crossovers
10-175 watts RMS per channel
Frequency Response 55-22KHz
Sensitivity 89dB
Impedance 4 ohms

[linuslinus]

Originally Posted by linuslinus

http://www.daytonaudio.com/media/res...ions-46153.pdf

this is the PDF link.. i blindly copied the wrong link by mistake

http://www.parts-express.com/pdf/295-356s.pdf

[mdocod]

Originally Posted by linuslinus

the speakers would probably sit horizontally with in arms distance from me.

Sideways would be better

the speaker will have a passive 2-way internal cross-over for the HF and MF drivers.

The position and slope of this X-over might be tricky to get good blending while still protecting the tweeter and keeping you out of the mid-range breakup nodes and tweeter distortion peaks. at such close listening positions, a rule of thumb is to use shallower x-over slopes. This may or may not be a problem depending on whether the drivers have major "flaws" that need to be covered up with proper x-over design or not.

... the MF/HF 89db and the LF is 86.2db. I am crossing my fingers that the vented enclosure can boost the woofer's efficiency to +3db.

Vented enclosure only significantly effects sensitivity down around the tuning region of the box. Plan on EQing or padding down your mid and high frequency stuff 3-6dB to get flat and then, depending on speaker placement, deal with baffle step losses.

With gain controls separate per high and low sections, combined with the EQ, there's no reason the system can't be adjusted to play reasonably flat IMO.

[linuslinus]

good good,

so what about internal dampening? polyfill, mineral wool, fiberglass, egg-crate lined, etc? is this necessary with the extreme bracing in place? my displacement calculations are off <>5%. so i need to add some fill to compensate.

[mdocod]

For a vented box, lining all surfaces with a single layer of any dampening that you like is fine IMO. Don't worry about 5% variances in box displacement, especially if you are going to post-EQ this thing flat, it just won't matter.

My personal feeling is that the open-foam egg crate stuff is probably going to be the easiest to cut to size and install, I might lean that direction for ease of installation personally.

Eric

[sreten]

Originally Posted by linuslinus

the MF/HF 89db and the LF is 86.2db. I am crossing my fingers that
the vented enclosure can boost the woofer's efficiency to +3db.

Hi,

No it won't but with an active c/o it does not matter.
Nearfield there is little point having amplifiers that push
the drivers to their power handling limits. 50W for bass
and 25W for mid/treble is more than you'll ever need.
(Unless your determined to be deaf in your dotage).

rgds, sreten.

[linuslinus]

Originally Posted by sreten

Hi,

No it won't but with an active c/o it does not matter.
Nearfield there is little point having amplifiers that push
the drivers to their power handling limits. 50W for bass
and 25W for mid/treble is more than you'll ever need.
(Unless your determined to be deaf in your dotage).

rgds, sreten.

what did you say? i can't seem to hear you.

joking aside.

i already have the equipment except for the completed enclosure. i just won't play it at deafening levels.