I need help with a speaker design using Hi-Vi A5+

[chasingame]

Hi,

A couple years ago I picked up 4 closeout Hi-Vi A5+:

http://www.parts-express.com//pe/sho...number=299-119

I also have a sack full of Peerless Tweeters model 811851 1" dome:

http://www.parts-express.com//pe/psh...number=279-082

My goal was to create a little speaker to use for my computer and maybe a bed room (lower end) Home Theater plus subwoofer.

Would someone enjoy taking on a task and model an enclosure and a simple XO I can build? I am not an expert but I have a very nice wood working shop with all the tools. I can handle ported but I think sealed would be quicker and easier for my goals, even at the sacrifce of some base - not a problem.

I could make a simple two way and have two pairs or I could do MTM or TMM, you decide

I will even pay you for a completed XO (pair) if you like doing that.

Thanks in advance.

[chasingame]

Any comments? Anyone ?

[sdclc126]

If you have the T/S parameters for the drivers you can design the XO yourself - you just need to get the software and learn how to use it.

Recommended:

http://www.rjbaudio.com/Audiofiles/FRDtools.html

[Dave R]

Hello,

I designed and built a TMM for a friend using (2) of the A5+ and (1) HiVi K1 tweeter.

The crossover is a series. The A5+'s were connected in series, so their combined load was about 12 ohms. That might sound a little unusual, but it seemed to work out nice. The impedance rolled off smoothly to the 5 ohm load of the K1 at the crossover point (somewhere around 4 kHz, if I remember correctly).

Anyway, I still have the prototype box (about 11 liters), the crossover design, as well as the K1 tweeters if you're interested.

Dave R

[mlise]

Hi,
Try Win ISD. It's free and works well. The Win ISD Pro is a little more fussy. I plugged in the TS parameters for the A5+. I figure two drivers in parallel with a tweeter in the center between them. The nominal load will be 4 ohms. The tweeters have more sensitivity than the woofers, so this ought to work out. You can add an L-pad if you want to adjust, but you really shouldn't need it.

The interior box volume ought to be 16.6L (1013 in^3). The volume occupied by the woofers is about the same as a cone of the nominal diameter of the driver and as high as the mounting depth of the driver. 1/3 pi()*r^2*h. It will need a port. Use 3" ABS pipe 7" long or so. You can trim this down by ear if you like, but it'll be close. This will occupy interior volume as well. That comes out to about 1118 in^3 total for the interior volume of a rectangular box. Using 1/2 inch plywood, that's a box measuring about 8*11*17.25 (exterior) with a big wad of fiberglass inside.

Cross it over with a 2 pole filter at 3500 or 4KHz. For a 3500Hz Butterworth crossover put 4uF to the tweeter with 0.5mH in parallel with the tweet. 0.26 mH to the woofs with 8uF in parallel with them. For a 4K crossover put 3.5uF to the tweeter with .45mH in parallel with it and 0.23mH to the woofers with 7uF in parallel with them.

There's a nice calculator at http://www.diyaudioandvideo.com/Calculator/XOver/

This isn't a high power cabinet, so 1/2 or 3/8 plywood will be fine. Get 'shop' grade plywood. this is smooth (sanded) on both sides and pretty cheap. It's a paint grade plywood meaning that you wouldn't want to use a stain finish on this for fine furniture where you could see the wood, but really, it looks fine.

This looks a little big for a computer speaker, but it'll roll off below 50 Hz. These should give the good gentle but firm shake of the testicles.

Cheers.

[chasingame]

Thanks you so much for the information. I am still trying to digest it all. I have two 4x8 sheets of birch laminate 3/4" MDF I had hoped to use. Will this work or will it be overkill ?

Yesterday I installed WinISD Beta (not pro) and started playing with it. Would it be possible for you to email the project file you created ?

I was worried about the woofer being 8ohm and the tweeter 4 ohm. But I see now that when you run two in parallel it halves the ohms right ? Creating a 4 ohm driver pair and a 4ohm tweeter. Cool.

I cant quite visualize the XO circuit. Is this a 6db or 12db ? Can you email this as well ?

Would I mount the tweeter in the center with woofers over and under ? Do I space them as close as possble ?

I am thinking that I may just create a floor standing speaker and hide a "bottom" within that taller cabinet to create the chamber for the correct volume. I am guessing the tweeter needs to be about ear level right? Or is this a dumb idea? Should I make a smaller box and use a stand? I am thinking I would rather use these in my bedroom for my TV now that they are MTM and much larger.

What happens to the power handling when you run two drivers in parallel ?

PM me for my email (assuming this forum has pm feature)

Thanks so much for all the advice... I am feeling better about this now.

[chasingame]

Also, if I already have an adjustable 2" ID unflared port, can I use this and what length would work with your modeled vented enclosure above ?

If not, I can order the 3". Are you refering to a 3" ID or a piece of pvc pipe ?

[activexp]

Hi Anthony,

You might find these sites helpful:

For crossover design:-
http://www.apicsllc.com/apics/Misc/filter2.html

For just about everything else:-
http://www.lautsprechershop.de/english/index_tools.htm
This is an excellent German site with lots of good stuff. Note that all dimensions etc are metric.

Regards,
Steve

[chasingame]

Can someone please contact the user mlise as the forum will not let me "email users" for some reason.

I would like to see if he would kindly explain a bit more about his post and how I can arrive at his same figures so that I can understand it my self.

My email is:

anthony at chasingame dot com

could someone help me out please ? thanks so much !

[mlise]

Hi,
I created a new driver in WinISD with the paramaters from your driver and told it to make a vented cabinet with two drivers loaded 'normal'. Under the Box tab you can see the interior volume you need. Under Vents you can tell it how wide your vent is and it calculates how long it should be. I usually put all this into a spread sheet to find the gross volume of the cabinet including the space taken up by the drivers and port. The 3/4" birch lam MDF is great stuff, but it'll look funny if you don't miter the edges. but jointed edges will work fine, but you'll need to seal the edges and sand before you paint the boxes, or just leave them undecorated. It just depends on your decor and wife/girlfriend influence. Do you have a table saw or Festool circular saw? If you have a circular saw, use a big straight edge clamped down.
Folks that are good a filters have big beards and lots of antennas on their cars. For normal folks, just use one of the crossover calculators. Each reactive element (inductor or cap) adds another pole (6dB) to the rolloff. A single pole, one cap to the tweeter and an inductor to the woofer is really simple and works fine, or you might try the two pole crossover. Often, people don't even put a crossover on the woofer, but a crossover to the woofer reduces distortion from resonant modes in the cone.
It turns out that WinISD and any online crossover calculator will make a fine speaker. Your biggest challenge is getting the cabinet to seal up. However you cut the pieces, go slow and measure a lot. A big sheet rock square is cheap and a great way to get the corners right. To visualize how all the pieces will fit together, try Google Sketchup. It's a free 3D CAD package that's pretty easy to use and all the manuals are Youtube videos.

Cheers,
M