Hey Brandon, my Son is heading off to 2nd semester and needs some speakers for his PC we built over the winter break. Mostly for movies and music with a little gaming. Was thinking of your Noobster MTM design with the new PE monitor amp
http://www.parts-express.com/pe/pshowdetl.cfm?Partnumber=300-774
Would be really convienient for PC use so he could free up some space without an amp/receiver. The efficiency seems like a good match as well. He'll be listening nearfield so it's a toss up between front or rear port in 1 cuft. The Amps just went on sale and considering the cost reduction of no passive components, seems like a no brainer. I'm concerned if i'll need to add a passive notch or if the 3k xo 24db/oct will get it done on it's own.
http://www.parts-express.com/pe/pshowdetl.cfm?Partnumber=300-774
Would be really convienient for PC use so he could free up some space without an amp/receiver. The efficiency seems like a good match as well. He'll be listening nearfield so it's a toss up between front or rear port in 1 cuft. The Amps just went on sale and considering the cost reduction of no passive components, seems like a no brainer. I'm concerned if i'll need to add a passive notch or if the 3k xo 24db/oct will get it done on it's own.
I'm not Brandon, but I think I can comment on this. If you use the active crossovers of the plate amp, the speakers will have nothing to do with Brandon's design except only the choice of drivers.
And you can't expect good driver summation from the use of active crossovers with predetermined slopes, due to the drivers' natural rolloffs.
I have modeled quite a few crossovers for the W5-704D in MTM for people here and over at the PE Tech Talk board. I can quickly model a crossover with the PE plate amp if you ask me. You'll definitely need additional (not many, though) passive components to achieve good crossover performance.
If you want high efficiency, a single TB W6-789S in MT is a good option, too. What tweeter do you want to use? The Vifa DX25?
-jAy
And you can't expect good driver summation from the use of active crossovers with predetermined slopes, due to the drivers' natural rolloffs.
I have modeled quite a few crossovers for the W5-704D in MTM for people here and over at the PE Tech Talk board. I can quickly model a crossover with the PE plate amp if you ask me. You'll definitely need additional (not many, though) passive components to achieve good crossover performance.
If you want high efficiency, a single TB W6-789S in MT is a good option, too. What tweeter do you want to use? The Vifa DX25?
-jAy
Thanx Jay and yes the DX25. I know he's going to drive them to their limits so hopefully the high efficiency will give him enough output without doing it too often. If the component count isn't too high, i'd certainly appreciate the effort. What first attracted me to Brandons design and the plate amps is the abilty of the 704 to play up to 3k nicely. I could just scratch the plate amps and give him my Onkyo M-282 but something tells me with a few components this is going to sound really really good.
I've got the 704s, but not the Vifas. They'll be nearfield about 40" apart and 30" from the listener. Basically on either side of a 32" monitor at a workstation. In an MTM design, the tweeters would be at ear level. A sub probobly wouldn't work in a dorm room so if i can avoid one and having to pay for an off campus apartment down the road......LOL.
Being crossed at 3 kHz with a higher order filter, the DX25 is an overkill. The Dayton ND20FB-4 or ND20FA-6 will be perfect in this application. Plus, they have no higher (even slightly lower) tall order distortion than the DX25 above 3 kHz. Also, if the speakers are near-field, they will be very sensitive to the slight change of the listener's ear level due to MTM lobing errors with the 3 kHz xover point. Close driver spacing with the Dayton neo will help here. If you still want the DX25, I can model up the xover with it, though.
I was also wondering if mounting this tweeter in a shallow waveguide as a continuation of the existing housing would help with the two peaks in the F5 at 2.1 and 2.7khz. I'm under the impression that the tweeter will operate a bit more efficiently but would need a cap to shape the freq response back to flat. Would the results be worth the effort with such an inexpensive build. I have a lathe and lathe operating experience if that helps. I've done a few cutting tests with MDF circles in the past and had good results. I'm suggesting something small, maybe 2.5" in diameter as not to increase the D to D spacing.
Here is my modeling result of an active MTM with Tang Band W5-704D midwoofers and Dayton ND20FB-4 tweeter using the Dayton MCA2258 Bi-Amplifier. This is the result of my full modeling including baffle step/diffraction and bass response. The crossovers are the Dayton plate amp's active filters plus a few passive components. I used about 2.5 dB baffle step compensation, which should be optimal for near-field listening with desktop placement. I recommend not using the Dayton amp's bass boost function. This will be useful in case the speakers are placed far-field on stands in the future.
Note in the schematic that the tweeter is connected in reversed polarity because this is an acoustic LR6 design. You will need to adjust the tweeter level control on the plate amp to find good balance. Assuming the gains of HF and LF amplifiers are equal, I predict about 1-2 dB attenuation of the tweeter will do.
The modeled bass tuning frequency is 44 Hz, which is achieved by using a 2" ID, 2.75" long tube in a 27 liter box.
The drivers' impedance with passiver components added should be benign loads for the amplifiers. You won't use more than 15 watts, at which the system is as loud as 100 dB at 1 m, and beyond that the midwoofers will run out of xmax.
The baffle used for modeling is 9" wide. You can use a 8" wide baffle for your build if you want a slimmer look. A 1" difference won't have any significant effect on the response. The drivers are placed with 4" center-to-center spacing. The tweeter is centered with no horizontal offset. Don't use any toe-in when placing speakers.
Let me know if you have any questions.
-jAy
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An externally hosted image should be here but it was not working when we last tested it.
Note in the schematic that the tweeter is connected in reversed polarity because this is an acoustic LR6 design. You will need to adjust the tweeter level control on the plate amp to find good balance. Assuming the gains of HF and LF amplifiers are equal, I predict about 1-2 dB attenuation of the tweeter will do.
The modeled bass tuning frequency is 44 Hz, which is achieved by using a 2" ID, 2.75" long tube in a 27 liter box.
The drivers' impedance with passiver components added should be benign loads for the amplifiers. You won't use more than 15 watts, at which the system is as loud as 100 dB at 1 m, and beyond that the midwoofers will run out of xmax.
The baffle used for modeling is 9" wide. You can use a 8" wide baffle for your build if you want a slimmer look. A 1" difference won't have any significant effect on the response. The drivers are placed with 4" center-to-center spacing. The tweeter is centered with no horizontal offset. Don't use any toe-in when placing speakers.
Let me know if you have any questions.
-jAy
Thanx for all the hard work Jay. The response looks excellent and i'm sure the low harmonic distortion of the Dayton tweeter will be an added benefit as well as a cost saver. Going to DIY the cabinets curved 1 cuft with a rear loaded port. The planned location on the workstation allows for about 1ft of clearance behind. I'll probobly do the 8" baffle with 1/2" roundovers. Will follow up with progress soon.
Anthony
Anthony
Oh, I didn't consider that the speakers have 1 ft clearance off the back wall. If you already ordered parts, never mind---it's just a little difference. If not, use the following. This one has a bit more BSC:
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Hello,
Interested to hear your results, about the results, anyway. I have the same drivers and see the amps on sale ~ 40% off atm. My wife's computer speakers need replacing (plastic Creative Labs speakers with cheap 3" full range drivers I think).
This concept might be a little large for the desk we have the PC on now, might end up w/a RS-100 design, w/small active sub, or, might re-arrange things to make speakers like this fit...
The W5-704 seems to be one of Tang Band's better, more consistent drivers. I've had a half dozen of them for a few months now, but not listened to a complete finished speaker with them yet. Maybe someday my garage will have heat...
Interested to hear your results, about the results, anyway. I have the same drivers and see the amps on sale ~ 40% off atm. My wife's computer speakers need replacing (plastic Creative Labs speakers with cheap 3" full range drivers I think).
This concept might be a little large for the desk we have the PC on now, might end up w/a RS-100 design, w/small active sub, or, might re-arrange things to make speakers like this fit...
The W5-704 seems to be one of Tang Band's better, more consistent drivers. I've had a half dozen of them for a few months now, but not listened to a complete finished speaker with them yet. Maybe someday my garage will have heat...
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