Jims 3 way speaker build

[jimbones]

hi thanks for checking in on this thread. I decided that I would start a new thread that followed a build from it's design stage through completion rather than a bunch of separate threads.Since I am not as accomplished as many of the readers in the forum I will be asking lots of questions as I go through the process. I'd like to thank those that have responded to my inquiries thus far and got me to this point. So let me share where I am.

I am building a 12 inch three way system. Selected drivers (based on lots of recommendations) are the SB 34NRXL75-08, the Arum Cantus AC130F1, and the Seas 27TAC/GB. I have received these drivers and QC'd them using DATS for rub and buzz. Currently I am designing the enclosure. It will be a 70L (internal volume) vented. I am oversized the cabinet by 0.8 cu ft to account for all internals. The front baffle will be 42" high by 16 inches wide. I am centering the woofer and it will be about 12" off the bottom. The Mid and tweeter will be off center mirrored pair such that the distances to the edges are staggered. Also the tweeter and mid have to be as close as possible (even slightly overlapping) since the XO frequency is 3300 hz. Once the cabinets are built I will take frd measurements. Kindly let me know if I am on the right track or missed anything important. I will post a diagram of driver locations on the baffle. Stay tuned and again thanks for your help.

[PWR RYD]

These will be some imposing enclosures at 16" wide by 42" high!

Driver selection sounds nice. What do you have planned for baffle edge treatment to yield some reduction in diffraction?

[jimbones]

nothing special other than rounded over. The cabinets will be a trapezoid shape with the narrower part toward the rear. I could put some sound absorbent material on the front baffle. ideas?

[Wolf]

I would recommend using no offset for the mid-range and tweeters due to having better Imaging at the listening position and better off axis responses. This will also help with BSC on your wide baffle.
There is no reason to xover at 3.3kHz or 2.5kHz, unless the drivers lend well there. Even at 3.3k, you should not need to overlap the drivers. The tweeter is not flat faced and is sculpted. I don't normally recommend 5.25" combos being above 3k in most 2ways, and 4k in 3ways, depending on drivers used. I would recommend an LR4 summation at 1.8k to 2.5k range, as the Continuum were at 1.8k with the same mids and the RS28.

Keep us posted,
Wolf

[jimbones]

The only reason I used 3.3k is because I have tried using the mid and tweet in a prototype set up and the tweeter sound better crossed over higher.(tried 2.2k didnt like it) Right now I have it at 3.3khz 3rd order. Now I wouldn't expect it to stay the same when I do the final build but I would expect it to be fairly close. The crossover will change im sure.

[jimbones]

Trying to figure out how to enable macros on my PCD. I usually compare my values to the auto calculate. Anyone know how to enable the macros? I tried several things but didnt work. I dont remember having this issue before....

[Wolf]

Analysis toolpak add-ins.

[jimbones]

yea I added them but the macros are still disabled. I think it is a security setting. grrrrrr.

Wolf I adjusted the design for drivers to be on center with no overlap but the mid and tweet will be close to each other. thanks for the advice

[a4eaudio]

jimbones - I'm looking forward to the build thread. I know you asked some preliminary questions in other threads before actually settling on a design. Maybe you should post a little summary of how you came to the conclusions on drivers, cabinet size, etc.

[jimbones]

Sure will do

[rpb]

I wouldn't rehash all that preceded this thread. It would likely just create more confusion.

[jimbones]

Note to all: Previous individual threads addressed driver selection, optimal enclosure size and venting/tuning (70L), and midrange enclosure sizing. I am currently finalizing my cabinet drawings and anticipate having cabinets in July. Just wanted to give everyone an abridged version of where I am currently at. Thanks

[jimbones]

question regarding vented alignment: Im thinking this is a SBB4 or SC4? Is that right? If not what alignment is this. (If I tune to 32hz it gets flatter still, so I am thinking it is a SC4)

[a4eaudio]

Hopefully someone else can answer your question, because I don't know. I would comment though that I don't think many people pay attention to those "named" alignments now that we have software and can tweak to get the transfer function the way we want it. Those alignments were useful before software because you could drop the T/S parameters into formulas and get a "known" alignment. (At least I think that is the correct history.)

[a4eaudio]

Deleted duplicate post

[jimbones]

This is the basic overall shape/size of my speaker. It's a trap but I dont have the time/patience for doing curved panels lol. Any major issues? otherwise FSA!!!

[a4eaudio]

Nice! I just built a tiny 0.15 cf trapezoid speaker back in April. I mocked it up in Sketchup to determine the ratio of width, height and depth I liked and was able to calculate the exact angle between the front baffle and side panels and then set my table saw using a digital angle finder. Of course you can always go old school and use trigonometry or an online angle calculator.

[jimbones]

a4eaudio, note that the front is wide and the back is narrow so it is a trap standing up.

[a4eaudio]

Yes, I realized that. I'm a fan of that shape. In your zoomed in portion for Detail 2 you have a gap between the back wall and side panel because the right side of your back panel is a 90 degree angle. In my case I was able to determine that the angle was 84.3 degrees and cut that side of the back wall on my table saw to fit flush to the side panel. Note, clamping was a challenge without all 90 degree walls but I have a 23 gauge pin nailer that helps a lot.

[fatmarley]

question regarding vented alignment: Im thinking this is a SBB4 or SC4? Is that right? If not what alignment is this. (If I tune to 32hz it gets flatter still, so I am thinking it is a SC4)

I wouldn't worry about the alignment, more important is a flat response (or as flat as possible) in your room. In my room an f3 of 45hz works well . With room gain I end up with good bass down to 25hz. A lot of people on hifi forums (not DIY) have problems with bass, so prefer standpoint speakers because they usually roll-off earlier in the low end, and are less likely to cause problems. Some then add subwoofers to fill in the low end.

[rpb]

This is the basic overall shape/size of my speaker. It's a trap but I dont have the time/patience for doing curved panels lol. Any major issues? otherwise FSA!!!

The speaker is too tall! The tweeter should be at least near ear level.

[jimbones]

I can locate the tweeter 36-39 inches off the floor. Note that in my listening chair my ears are 39 inches from the floor.

[rpb]

Your sketch shows the big box height as 43.5"

[jimbones]

The speaker is too tall! The tweeter should be at least near ear level.

rpb correct, so there will be about 4 inches of space above tweeter.

[rpb]

rpb correct, so there will be about 4 inches of space above tweeter.

What, if anything, is in the top section?

[jimbones]

rpb this may help. I can alway make it shorter and adjust the dimensions to maintain internal volume

[rpb]

The other section drawn above the box is the top view guess. I thought it was all the front baffle.