# top-quality DIY In-walls



## fusseli (May 1, 2007)

For christmas my mom wants a new set of in-walls to replace their current old ones. I've made her a set of DIY 2-ways before, and as moms go, she'd rather me make her something than buy an off-the-shelf upgrade. Don't have a specific budget, but probably $500ish for the pair would be the expected range.

My plan so far is to use the DIY in-wall kit from PE, in order to get the largest woofers possible. The plan is to simply increase the current hole size from the existing pair, and drop these in. They listen to about 98% of their music from the current in-walls so a top quality replacement would be a huge upgrade. They are driven off of an older Kenwood AVR in the basement HT room, as "B" speakers, and have a local transformer-type volume dial. 

For woofers, I've been looking around a lot for 8-inchers that look okay for IB use. Where they are installed isn't really a massive airspace, but a step in the corner of a slanted ceiling. I'll get a picture of this to show the location these are going, I'm modelling with a very large sealed box rather than as true IB. I've been looking for woofers with as low a resonant frequency as possible, and a Qts of 0.4-0.5, if I should be looking for something else someone please say so. My current choice is the HiVI M8a, with an fs of 30Hz and Qts of 0.43. Anyone know of a better 8" woofer for IB use? I've used the M8N in another project before and loved the sound, coincidentally the M8a looks to have good specs for IB use.

I'm not as sure on a choice for the tweeter. Definately will need the best off-axis response as possible, so should I just be looking at domes? I've found a few that look nice and should play low enough to blend with something like the M8a: Seas 27TBC, Vifa NE19VTA, Morel MDT-22. Another thing I'm worried about really is the off-axis response, since the speaker locations are by the ceiling, maybe 10ft+ high. The room is pretty large, maybe 40'x12'. Any ideas for setting up an angle-mount in the baffles for the tweets? 

I'm also thinking about painting the speaker baffles to match the paint in the room, since I'm concerned about the grills not clearing the woofer surrounds completely. So a tweet with a removable baffle would be nice so I could paint that, too.


Any and all input would be appreciated.


----------



## bambino (Feb 21, 2010)

Your best bet, since you are DIY'ing them is to build backboxes for them that way they will sound better then just putting speakers on a board and slapping them in the wall so to speak.:T


----------



## fusseli (May 1, 2007)

I thought about that, but the location doesn't allow for building any enclosure into the wall so it'd be limited to whatever could hang off the back of the wall mount. When I get a pic up that should help show what I mean.

You are right though, a sealed Qtc .707 box would handle 20W. The IB config would only handle 20W with a 2nd order HPF at fs, and that loses a solid 1dB for most of the bass range compared to the Qtc .707.

The only problem is, as I mentioned before, I'm not sure that I could fab an in-wall enclosure for these. So the best suited 8" driver for IB may be the best bet.


----------



## fusseli (May 1, 2007)

Here's a pic of the locations. Either speaker is in the two top corners of the room, more or less.


----------



## fusseli (May 1, 2007)

any more comments?

I'm now considering something like the Dayton RS28F to go with the M8a woofer, since that tweet can be crossed as low as 1.2khz. That might be necessary with as bad as the cone breakup gets on the M8a... won't know untill I actually start fiddling with a crossover design.


----------



## vann_d (Apr 7, 2009)

I was thinking of doing in-walls and was going to do the Zaph MTM kits from Madisound in the PE in-wall baffle. These were the best in-wall design I could find and they also will fit on the baffle (barely). They seem to be designed very well and are a great deal.

Also, you could do yourself a favor by improving your speaker locations. Reflection off of the ceiling is probably muddying the sound not to mention the angle off axis at which you are listening...


----------



## vann_d (Apr 7, 2009)

Just re-read your original post. Seems like changing locations is out. I would go with a coaxial where you could adjust the tweeter angle. Emotiva is having a killer deal on their in-walls but they are 4 Ohm. Could be ok assuming your mom doesn't crank the volume too often .


----------



## fusseli (May 1, 2007)

Ya, there's nothing that can be done about those current locations. Me cutting bigger holes for the big in-wall kit from PE is a stretch as it is. Funny thing is that they put music on and are only in that room half the time, the rest of the time they're in one of the adjacent rooms. That doesn't change priorities of the build, however.

I'll look around at the emotivas and zaph designs a bit and see how I feel about it.

[minutes later....]

those emotiva's do look nice, the most appealing thing is the claim of -3db @ 38Hz hahaha. 4-ohms definately isn't desirable, they don't ever crank it up real loud but it's more of a risk of them getting left on at a moderate level for hours on end, and the receiver over heating or something (e.g. party, bbq, whatever).

i'm skeptical of the zaphs, and beginning to become skeptical about the criterion for most in-wall designs. i wonder if the "in-wall" crossover just drops that baffle step section? the woofers in the zaphs have an fs at just 65Hz and Qts of 0.44! Unless those have some built-in ssf or something, any low bass would blow those things up above just a couple watts... hmmmmm. based on that, it makes me think the M8a is a better contender than ever. that and i am certainly capable of designing a 2-way crossover.


----------



## vann_d (Apr 7, 2009)

Yeah, no baffle step in an in-wall. That's the difference. The Zaphs are meant to be used with a sub and an active xover. You seem to be mainly concered with low frequency response so those would be out for sure. 

Sounds like you want a little project too. Have fun. Sorry can't help you pick a raw driver...


----------



## fusseli (May 1, 2007)

Well I think I have the design pegged. Modelled using raw .frd info from the drivers, the HiVi M8a and the Dayton RS28a. Both are aluminum and should match voices nicely, I'm thinking.

I worked up an xover based on the actual physical layout, and an off-axis listening location @ 4m away. Kinda taking advantage of the fact that the sitting/listening area and the location of the speakers is pretty well set in stone.

physical layout:









xover:









The crossover model achieves 2nd-order roll-off for the LPF at 1300Hz (actual filter is below 1kHz or so), 4th order roll-off in the HPF at 1300Hz, series L-pad resistance of 2 ohms, and includes a series LCR notch at the woofer's breakup mode (2khz).

Overall model is within +/-2dB and I'm not sure much could be done to improve it? Further off-axis response and power response look pretty great also. Actual on-axis response is pretty raunchy, but I don't see anyone climbing on a ladder to listen to these at that level.

Oh and impedance stays above 6 ohms, ty series l-pad 

Any comments or suggestions would be appreciated.


----------



## bambino (Feb 21, 2010)

Is that a store bought program or something you downloaded, i gotta have it.:bigsmile:


----------



## fusseli (May 1, 2007)

Did some more tweaking and I think I'm happy with it. Kinda taking a gamble at designing for off-axis performance. According to the exact spacing and orientation I've layed out, 4m away and 2m down the response is looking pretty good! I'm going to call this a wrap and order parts in the next few days. The xover is achieving roll-offs of 4th-order Butterworth on the woofer, and 4th-order Linkwitz-Riley for the tweet (both @ 1200Hz). I'd call it an 8 Ohm "nominal" load. Theoretical FR looks to be +/-1.5dB now in this "finallized" design. 

Used the PCD box modeller to extract min phase of the woofer, and used the raw phase data of the tweet. Both reference z-axis are left at 0.0, since both were measured at 1m by the manufacturers. Shifting reference planes for either driver by 10mm does change the FR, but doesn't seem to make a lare impact. I'm crossing my fingers that my assumptions are correct.










Also decided to add a 1st-order passive HPF @ 26Hz to protect over excursion at low frequencies, since these won't be used with a sub. This should make the M8a's handle 15W full-bandwidth, and 30W+ above 40Hz




bambino said:


> Is that a store bought program or something you downloaded, i gotta have it.


The software is Jeff Bagby's free Passive Crossover Designer 7.0, to be used in conjunction with other software he's developed. It allows DIYers to create pretty accurate designs without expensive measurement equipment and other stuff that real pros use. I love it.


----------



## bambino (Feb 21, 2010)

Thanks for the hit on another site to check out. I'm getting ready for my own DIY crossovers and could use all the help i can get.:bigsmile:


----------



## fusseli (May 1, 2007)

bambino said:


> Thanks for the hit on another site to check out. I'm getting ready for my own DIY crossovers and could use all the help i can get.:bigsmile:


The PE techtalk forum is also a great place to go for all DIY-audio related stuff.


----------



## harleyhualer-sc02 (May 25, 2008)

if you're worried about the surround hitting the grill, couldn't you just mount the driver from the rear of the baffle and do a round over on the front?


----------



## fusseli (May 1, 2007)

harleyhualer-sc02 said:


> if you're worried about the surround hitting the grill, couldn't you just mount the driver from the rear of the baffle and do a round over on the front?


ya youre right, that's what I'm currently going for. Bottom or flush mounting both drivers is the only way that the grill will fit properly.


----------



## fusseli (May 1, 2007)

Parts came in and I've started construction.

The real final layout, after simulating every possible configuration. There's hardly enough room on the baffles for both drivers so there really aren't many options:










Starting to figure out crossover placement and driver mounting. PE wasn't lying when they said the largest woofer size possible is 8", just so happens that the [beautiful!] M8a's are 8.5" in diameter, which can be seen below.









To make the woofers fit on the baffle, some modification is required... good thing I just got this handy Craftsman contraption that's dremel meets sawzall!









Woofers fit now. Will probably seal up the rough gap with some caulk upon final assembly.










Tomorrow I'll be cutting holes and painting the baffles. Probably going to come up with some out of the box idea to get all the xover parts to fit/mount.



After changing the orientation, the xover isn't perfect anymore but oh well. Closer to +/-1.5dB theoretical now with a <3dB swing around the crossover point. Here's the schematic:


----------



## fusseli (May 1, 2007)

Pretty good camoflage for a can of spraypaint from Home Depot!


----------



## bambino (Feb 21, 2010)

Looks like they are coming together quite nicely, great job.:T


----------



## fusseli (May 1, 2007)

Call it a wrap  To be honest I screwed up the baffles in more ways than one, and didn't have time to order fresh ones so I just went along with it. 

Only hiccup was needing extra long screws to attach the baffles to the mounting bracket in the wall. The PE kit must assume you're not using thicker than 5/8" drywall, in my case I'm using 1x4 blocking on either side where the hardware sandwiches onto the wall. The six supplied screws were way too short, so I just used some 4" ones instead. I'd guess the finished product here to be ~10lbs, which is pretty heavy especially compared to what they are replacing.

The grills are fairly transparant even after being painted, plenty dark enough to hide the imperfections though! They are heavy and metal, not light flimsy plastic like the former ones. It took some pretty serious convincing to get the grills on once the baffles were torqued down, so it's safe to say they aren't going anywhere...



First, the old:










DVC? O.O

































Now, the new:











Silicone & zip-ties, and a wide angle bracket. Hardly enough room for all of the xover components. I considered putting the entire xover on a seperate board to sit in the wall, but decided not to.



















































They sound pretty nice before any breaking in. Acoustic and jazz is particularly articulate and detailed. Bass is improved over the former cheap in-walls but not as strong as I was hoping, crossing my fingers that it will fill in a little over time. I really want to take some REW measurements but I can't really due to the AVR and room being across the house from eachother. I may try and setup a computer to record and average a spectrum and just play a pink noise disc...

Power handling seems to be excellent. With my zune on the input, these speakers can max out the AVR and produce 104dB+ (radioshack meter)distortion free. Off of the dvd changer via optical, the AVR seems to start clipping before max volume. No bass demanding music I've played so far has made the M8a's bottom-out.


----------



## bambino (Feb 21, 2010)

Very nice job and happy to hear they sound much better then the old ones.:T


----------



## jvinhj240 (Aug 18, 2012)

look really good


----------



## lfergus08 (Jan 25, 2012)

Those ended up turning out really well. I'm sure they will enjoy plenty of jazz up there now!


----------

