TMWW... First DIY project

[WernerM]

I don't see any problems. You've certainly put in your time with PCD. You deserve a break - starting cutting some wood!

Thanks Don, you know it dawned on me this morning that I should go to Lowes and have them cut the panels, and then take them with me to AL and get my Dad's help. He would really get a kick out of that, and it would make them even more special to me. I also think ultimately I am going to cut the baffle a little larger, so that I can glue 1/4" plywood to the sides, and sand and stain for a nice simple finish. Still thinking a Red Mahogany, or deep Cherry finish, with a black baffle would look real nice, and match my decor'.

[WernerM]

Well crap just rememberd I can't make the baffles bigger without remodeling.

[WernerM]

So i am now building the baffle the same size, but the box will be 9.5"W x 39.75"H x 16.5"D. Still yeiding the same size enclosure, but giving me the space to put the plywood, and baffle will still be even with sides.

[WernerM]

Woohoo!!! Just did the math, and parts for crossovers for BOTH sims is $107.10 before shipping, not too shabby! So total invested will be ~$300 total for listening tests, raw mdf cabs. I say ~$300, because I will have $250 invested when I buy crossover parts, and the only items I am lacking are screws, and damening material. Have the terminals, gasketing material, yada, yada, yada. I may beat the $400 budget end goal!

[rpb]

I assume that you did the extraction thing on the file, which I know nothing about. If you would, post the file you used in your sim so I can try it in my sim.

[rpb]

What's the final mid location?

[WernerM]

Hmmm... I have used the 6.5" and the 12" GRS poly woofers. I have no reason to doubt their 8" brother would behave very similarly.

The Vifa chosen as a mid will be somewhat low sensitivity otherwise an excellent, wide band choice.

The Goldwood tweeter you chose is one of very few GW tweeters that looks to be "ok".

What I would do in your situation is to throw a big coil on the woofers (5mH or so) along with a shunt network of a 25uF cap and 6 ohm resistor.

The mid I would put a single series cap and coil, say 12-18uF and 1.0mH or so coil.

The tweeter I would add at least a 6db L-pad and a small coil, 2-3uF.

The GRS woofers are really not terrible drivers - just not overly superb at making the really deep bass. They have a really nice, old school thump to them though.

The above is just an off-the-cuff speculation.

I was just going back through the thread, and for off the cuff, Johny was pretty F'n close!!! WOW!!!

I mean my sims ended up bieng a 6mH coil on the woofer with a shunt network of 80uF cap and 6 ohm resistor.

For the mid HP I have a 47uF cap and 2mH coil LP is a 1.5mH coil with a 10uF cap, also a parallel RC of 10uF and 12.5 ohm before the crossover.

Tweeter ended up being a 1.5uF cap with a .33mH coil a shunt resistor on coil of 2 ohm, and another 3.3uF cap. A series resistor of 10 ohm before crossover, and an L-pad of SR 2 ohm PR 8 ohm.

[donradick]

Thanks Don, you know it dawned on me this morning that I should go to Lowes and have them cut the panels, and then take them with me to AL and get my Dad's help. He would really get a kick out of that, and it would make them even more special to me. I also think ultimately I am going to cut the baffle a little larger, so that I can glue 1/4" plywood to the sides, and sand and stain for a nice simple finish. Still thinking a Red Mahogany, or deep Cherry finish, with a black baffle would look real nice, and match my decor'.

That sounds good - it's a classic look to have a black baffle and dark wood box. I've used a variety of Home Depot and Lowes plywood over the last few years - Home Depot has some pine plywood called Accuply that is my current favorite - lots of layers, nice A-A surface on both sides. I've often used Birch or Oak face plywood - which is a lower quality, less layers, but you can basically sand and stain it as is. If you decide you want to face them with 1/4 inch ply, remember you will need to cut it very precisely and cleanly and then glue it on straight and solid to the existing box. Seems like less work and better results to use 3/4 inch hardwood faced ply and be done with it. If your dad can miter the corners it will look very good. (But I am not a woodworker! I just do the best I can, and try not to make the same mistake more than twice )

[WernerM]

What's the final mid location?

32" high in the 40" baffle on center horizontally.

Here is the file

vifa.frd

If you have RM downloaded, all you have to do is go to the right in the screen a little to the Hilbert Bode transfer section, and extract min phase from frd, then choose the file you sent me, and save it when it is done. Then you import that file into PCD.

[Wolf]

One thing looking at the response vs. power response. Your on-axis looks quite nice, but the off-axis will likely have a peak in the 2kHz region, and a trough to either side of it.
This can lead to a little bit of a fatiguing sound if it is modeled correctly. Then again- depending on placement, you may not even notice it.

Give it a shot!
Wolf

PS- Here's a shot of a 3-way model I did for a reference point:

[rpb]

Different speaker drivers right?

[rpb]

I was just going back through the thread, and for off the cuff, Johny was pretty F'n close!!! WOW!!!

I mean my sims ended up bieng a 6mH coil on the woofer with a shunt network of 80uF cap and 6 ohm resistor.

For the mid HP I have a 47uF cap and 2mH coil LP is a 1.5mH coil with a 10uF cap, also a parallel RC of 10uF and 12.5 ohm before the crossover.

Tweeter ended up being a 1.5uF cap with a .33mH coil a shunt resistor on coil of 2 ohm, and another 3.3uF cap. A series resistor of 10 ohm before crossover, and an L-pad of SR 2 ohm PR 8 ohm.

If those are the x-over part values you want to try, I might be able to sell you some surplus parts for a good price. I believe I have a few extra coils in the 1.3 mH to 2 mH range.

[WernerM]

Yep those are what I am going to try. The difference between using the data you measured, and the SPLCopy of zaphs graph is just a couple of resistor changes, so I think it is time to build and listen, and tweak from there if necessary.

[rpb]

Just wanted to post one more. This one might be a little more expensive than yours.

[WernerM]

Just wanted to post one more. This one might be a little more expensive than yours.

Can you repost that with both power response, and driver phase shown? Also, the only issue that I worry about with that crossover point is lobing. It looks like the crossover point is around 4250Hz, and the problem with that is that both the tweeter and mid I am using have ~2" CTE, netting 4" CTC. 13500/4=3375Hz which the crossover point in my last sim is ~3200Hz. I appreciate the effort, and it looks great, I just wonder if lobing will be an issue there. BTW did you measure the mid on a 40"H x 10"W baffle mounted at 32"H with no offset? I think you said you did, but can't remember.

[rpb]

Can you repost that with both power response, and driver phase shown? Also, the only issue that I worry about with that crossover point is lobing. It looks like the crossover point is around 4250Hz, and the problem with that is that both the tweeter and mid I am using have ~2" CTE, netting 4" CTC. 13500/4=3375Hz which the crossover point in my last sim is ~3200Hz. I appreciate the effort, and it looks great, I just wonder if lobing will be an issue there. BTW did you measure the mid on a 40"H x 10"W baffle mounted at 32"H with no offset? I think you said you did, but can't remember.

The vifa measurement was on a 12" baffle and offset. I can cut the board down and remeasure. I don't post the phase because it clutters up the picture so much. Same with power response. The power response is simply going to dip a little at each x-over point. If I was concerned about those dips, I'd alter the filter orders, and then there would be a very small reverse null at each x-over point. I will however post it later this evening. I don't think lobing is an issue crossing high. That can also be demonstrated in PCD by adjusting the listening height. I'll do that as well.

[rpb]

Here's the power response.





Here's the phase.





This is the begining of a null about 14 degrees above the listening axis. I gets very deep at about 35 degrees.

[Wolf]

That is a very nicely aligned phase plot.
Well done!
Wolf

[WernerM]

Okay, so looking at your graph rpb, and Wolfs, I see two phase alignments at the crossover points. So this is what I am supposed to see? The woofer/mid phase should overlap at the crossover point, and the mid/tweet should overlap at their crossover point? So if this is correct, then mine doesn't look so good to me anymore. Yes I have great nulls, but that doesn't mean that it is the best crossover for my design? What about the lobing issue, do you think it will be a problem at that high crossover point? The reason I can't get the drivers any closer CTC, is because of the design of the tweeter surround, it is 4" wide. I suppose that I could try to trim it to get the mid/tweet CTC closer, but I am not sure that I am capable of that. Well, I am capable, just not confident I can do it well. Sorry, I just want to get these right, I know that really, I should measure the drivers in the cabinet before designing the crossover, but I don't have the equipment for that.

[rpb]

Okay, so looking at your graph rpb, and Wolfs, I see two phase alignments at the crossover points. So this is what I am supposed to see? The woofer/mid phase should overlap at the crossover point, and the mid/tweet should overlap at their crossover point? So if this is correct, then mine doesn't look so good to me anymore. Yes I have great nulls, but that doesn't mean that it is the best crossover for my design? What about the lobing issue, do you think it will be a problem at that high crossover point? The reason I can't get the drivers any closer CTC, is because of the design of the tweeter surround, it is 4" wide. I suppose that I could try to trim it to get the mid/tweet CTC closer, but I am not sure that I am capable of that. Well, I am capable, just not confident I can do it well. Sorry, I just want to get these right, I know that really, I should measure the drivers in the cabinet before designing the crossover, but I don't have the equipment for that.

You want the phase to be close at the x-over points. I got a little carried away trying to make this one "perfect". Not that it is perfect, but it's overkill to tweak that much in PCD. If you have a 10 dB null when you reverse the polarity, it's close enough in my opinion. I've never used PCD to actually make a x-over. I do trial and error, and check for a reverse null. It's nice when its -15 dB or more, but -10 dB is good enough I think. I don't think the lobing would be a problem if you are sitting. If you stand, the dip may be audible if you are listening for it. There's nothing wrong with crossing a little lower though. I was trying to work around a little bump in the mids response. Crossing higher made it easier to tame the bump. I will cut the baffle down, and remeasure. Then you can see if anything changes, and fine tune a little.