Starting my first project, something like the Bose Buster only bigger

[mackintire]

I 'm working on a project to replace the speakers that came with my Onkyo HT-800. My wife has decreed that they do not match the furniture.

I started out by looking that the Bose Buster project with with a 5.1 setup in mind. Then I got it into my head that I could do better. So here goes.

The mains are in two parts The top is MTM with the dayton DB20's and (2) HiVi B4N's in cabinets that are 15" high, 6.5" wide and 9" deep.

I 'm going to start things out by doing two things at once. Modeling the setup with the origional bose buster X-over in LSP-cad and at the same time planning on doing my own thing using 4th order LR crossovers.

The two mains will sit on cabinets that not only act as stands but have side firing woofers. The woofers are 6.5" and are from Klipsh promedia 2.1 units that had damage elsewhere. I 'll have to test the speakers to get the exact specs but in general they will probably be crossed over around 120hz with extension down below 40hz in their vented cabinet, I'm using the volume of the origional cabinet. The Klipsh woofers are 4 ohm and 50 watts each. Their cabinets will be 3/4" MFD 25.5" high , 6.5" wide, and 9" deep.

So so far I 've selected drivers and tinkered with CAD modeling the cabinets.

The Center Channel speaker is giving me more design problems. I'm trying to figure out a way to extend the response and still fit everything my constrained box size 18" wide, 7.5" deep and 6.5" high.


I was thinking about doing a WWMTWW arrangement via 3.5 crossover.

That being Tweeter (6 Ohms) Mid (8 Ohm) Two woofers in parrallel (4 ohm) with the final two woofers being parrallel in series, X-over around 120hz so that at 60hz the sum load will be back to 8 ohms. I 'll have to do more modeling to see where this goes. But the idea is as the frequincy goes lower more of the load is redistributed to all four of the woofers so at some point all four are being equally driven at a 8 ohm load. At 300Hz the second set are not being driven and the unit acts near identical to the Center channel design used in the Bose Buster project. I tried to model it as a vented enclosure, but that did not work out very well. I 'm thinking of used the a resistive port instead.

Ok small update: I think I've settled on using the origional design with a resistive vent. -3db should be right below 80hz.

Any thoughts Ideas?

This project is kind of a long term. I should have the cabinets assembled within the next 3 months and some driver testing done while things are coming together. Also I need to ask. Is there a design issue with the Bose Busters in regards to the placement of the tweeter? I know I am going to have different baffle related issues, but can I prevent any of it by offsetting the tweeter?

[mackintire]

Another update, I've definately gotten the main box specs where I want them. I need to spend a little more time on the baffle calculations before I decide on where the tweeter is going to be located.

I've attached a pic of the top portion of the mains. The picture does not show it but I was planning on using a 0.5" roundover on the front edges.

Another thought I had is..... after spending the night with WinISO pro, I think I need to get the klipsh driver tested before commiting to the lower section box design.
I could do this blindly and copy the manufactures design, but I'd rather be able to do this correctly.

That said, can any of you test this woofer out and generate the required parameters? If not its going to be a month or two before I can have it arranged to do it locallly.

I'm in PA near Pittsburgh

[HareBrained]

Interesting speakers you got goin'. Getting the Kipsch driver measured is wise. I've seen a number of people use the M4N but not any using the B4N.

0.37cf for the MTM sealed seems to be larger than required for F3=120Hz.

If you're thinking of a 3.5way, note that the 0.5 aspect is to cover the baffle step diffraction which can, depending on the baffle width, impact frequencies as high as 1000Hz. This would mean both the 2nd WW and the 2nd M would have to be implemented as .5 xovers. And in the end, the WW wouldn't be .5 at all since the BSD below 100Hz is essentially flat. Not that it can't be done but it wouldn't be your normal MTM.

If you look at Zaph's ZDT3.5, you'll see his woofers xover at 850Hz. It the BSC (compensation) that driving that xover frequency, not the range of the RS52. And you not knowing the capability of the Klipsch 6.5" woofer makes it difficult to know if it'll work. In the end, I think it won't be up to the task. Maybe you should get the Dayton WT3 to get the T/S parameters.

I think you'll find the 6.5" woofer doesn't play very low (Fs~50Hz). I'm certain it was optimized for it's small enclosure, not frequency extension. I realize they claim a frequency range of 32-20kHz but they don't say what level you get at 32 Hz. It could be -10db or less.

Building a 3-way is difficult enough, but having to create 0.5-way effects on the mids and woofers is going to compound the issues. Maybe you should look at just a straight 3-way.

You could also just use the Klipsch drivers with a plate amp(s). This would simplify your xover design, and the characteristics of the Klipsch drivers becomes less important.

[mackintire]

Thanks for the heads up. I was going back and forth on the .5 part and I think there is enough of an argument to not proceed in that direction.

In my model F3 is showing around 80hz without a high pass filter.

With a 4th order LR filterset to 100Hz F3 moves to 130Hz and the -6db point is 100Hz. The rolloff ends up being 24db per octave.

Xmax looks good as Zaph points out HiVi often lies about the Xmax for these drivers.

This system is for the family room TV, in the area the kids will abuse. My better audio equipment is packed away as our place isn t big enough for it.
I should have mentioned that this is a system on the cheap <$600. If and when the klipsch drivers melt, blow...etc I can talk my way into spending additional money on the upgrade. My wife has my budget fixed for the moment.

I modeled the mains in WinISD pro. So far it looks good. I'll know for sure when I recheck my work in LSP CAD. Hopefully by the end of the weekend I ll have some baffle step data calculated.


A single Klipsch promedia 6.5 subwoofer (I've got two) driver in its factor box can eproduce 106db at 45Hz given 70 watts RMS of input power. 3dsoundsurge.com found (about -8 dB at 40 Hz, - 12 at 35 Hz and –24 dB at the 31 Hz point listed in the system specifications)
I know the woofer is bottoming out and that there is a bit of port noise apparent starting at that volume. (probably need a 30Hz subsonic HP filter)
Two klipsch 6.5 woofers should make 109db if everything works out.


Hyjacking my own thread for a moment.....
Since others here may know, have any of you heard the Axiom M80's in comparason to the Statements? What's the perceptable difference?