TMW - Inwall surrounds.

[JamesB77]

I want to build a set of TMW In-wall surrounds to match the Dayton RS TMWW Mains that I have already built. I have these speakers recessed in the front wall, so as far as i know they are essentially acting as in-wall speakers. I had the cross-overs designed with that in mind. For the surrounds I would like the tweeters to be SEAS Excel T25CF-002, the mid to be SEAS Excel W15CY-001 and, the woofer to be the same Dayton RS225-8 - the 8 ohm version.

Here is what I have designed so far.

Images not available

Because I am limited in depth I have had so substantially limit the depth of the box. The original design for the towers had the TW box with a depth of 5.75". I have had to reduce that dimension to 5". In order to keep the same internal volume i added length to the bottom. Is this ok or should it be added to the width?

So - any input guys? Am I on the right track with this or completely out to lunch? Any help id definitely appreciated.

[cjd]

I'm really unclear on exactly how you're working these out, both crossover-wise (existing speaks as well as the new one here) as well as what original design you're referring to - though adding to the bottom may be fine (not a freebie, it changes floor-bounce frequency,) while adding to the width (for an in-room speaker at any rate) is usually the one thing you never want to do (usually no adding height above the tweeter if the tweeter is at the top of the speaker is similarly a bad idea.)

A pair of RS180-4's in series will give you similar results to the single 225 but give things a bit more breathing room behind as they're 1cm shorter. For surrounds, the slight loss in low-end extension is unlikely to be a significant issue.

That aside, you're amazingly close to the In-Khan-Neato design, driver choice aside. And those worked out really well, in my opinion.

[JamesB77]

Ha, as you can see I’m really new at this.

My overall goal is to build a set of in-wall speakers that match the towers.

Maybe if i give a bit of background it may help what I'm trying to achieve. I am building a dedicated HT with a false wall and the speakers behind the screen. I've also incorporated an IB sub behind the screen. To get enough room for the IB behind the screen I've had to bring the front wall close to the false wall and recess the towers into it. Here's a quick layout of the room.



and what it looks like at the moment.



When I had originally built the towers I wasn't going to recess them but as the design of the room progressed that's where they ended up. I had Solen.ca design the crossovers for me with the recessed position in mind. Looking back I probably made a mistake in switching out the Tweeter and Midrange drivers from the original design.

So, looking at this a different way. If one were to design an in-wall speaker to match the Dayton RS TMWW Mains designed by dawaro with a maximum inside depth (back of baffle to front of back panel) of 5" how would you go about it?

[---k---]

I'm glad you cleared up the fact that Solen had designed the crossover for you. At first I thought you just swapped drivers and didn't change the crossover. Though, I'm not familar with Solen's crossovers , so I can't say what the level of optimization the crossover has.

Anything is possible. First question, are you planning on designing the crossover yourself or are you asking for someone else to design it for you.

If you're doing it yourself, you're diving in the really deep end of the pool for your first crossover (3-way with metal cone drivers). The recommendation would be to start with a simple 2-way with easy drivers. But, if you're going to press forward with designing the crossover, you should know the crossover designers that hang out here are a bit of perfectionist. I say that with love. But, you won't get a lot of help if you're not really taking the time to learn how to do it correctly and are just wanting to wing it.

If you're looking for someone to design the crossover for you, well there are several that will do it for you if you got a project that interest them. PM is often the best way to negotiate it.

I try not to pimp my own designs too much, but, as CJD mentioned, the In-Khan-Neato's use the RS28, RS150, and RS180 and are probably a good match to the original TMWW (but who knows with what you got now). The in-wall loading and placement will make a huge impact on sound. In this case, I personally would rather have a speaker designed from the get go for in-wall use rather than something adapted or close enough.

[JamesB77]

Thanks for the replies guys.

I'm not sure what level of optomization they have either . When I asked them to build the xo's i asked for a linkwtiz-riley cross over, I think it may have been a 4th order. I'll have to check. Whether they built that for me I don't know.

I would love to learn and build my own cross overs and I'm sure I will need a lot of help along the way. I think what I will do is get the box designed and attempt to design a cross-over. If i'm having too much trouble I will see if I can get someone to do it for me.

I took a look at the In-Khan-Neato's and they look really good. However, they are too deep for me since the depth of my application is so limited. I would have to change either the with or length of the box.

Correct me if I'm wrong, putting the speakers in-wall basically gives you a really large front baffle. So the length and witdth of the baffle aren't as critical as they would be with free standing speakers. There would need to be changes to the cross-over vs. a free standing speaker but the box design is fairly flexible.

[cjd]

Yup. YOu can tweak the in-khan dimensions as much as you want. the baffle dimensions are infinite as-designed, the box is just convenient.

[---k---]

Somewhere in the In-Khan thread there is a discussion about the minimum depth. I think CJD said the box could be down to like 6". You're going to have the same issue with anything with a 6" woofer.

[JamesB77]

Somewhere in the In-Khan thread there is a discussion about the minimum depth. I think CJD said the box could be down to like 6". You're going to have the same issue with anything with a 6" woofer.

Thanks, I went and had a look at your build thread. I noticed that the minimum box depth was 6.5". The maximum amount of depth I have to work with allows a box of about 7.25".
What is everyone's thought on a 1.5" baffle for surrounds? Is it needed? I suppose it would depend on the size of the box.

[JamesB77]

Ok, I've given the box design another try using 2 RS180's as recommended by cjd.
Pluging everything in to Unibox it gives me a Vb of 39.7L or 1.4 ft3 for the RS180's and a Vb of 4.2L or .15 ft3 for the W15CY-001.

This is what I've come up with:

Images not available

Over all box dimensions of 40"x17"x7.25" and 3.2" behind the RS180's.

[lhwidget]

Nice project. I do believe your false wall makes the biggest cabinet I have ever seen (glued and screwed wall construction?)

The only thing you may want to re-think is the inset baffle design. While the major difference between free standing and in-wall designs is no need for baffle step compensation, the small step around your baffle will have a distinct diffraction signature.

An absolutely flush design will practically eliminate this.

[JamesB77]

Thanks for the suggestion. I will take the insert out, which should make it easier to build as well

[---k---]

What is everyone's thought on a 1.5" baffle for surrounds? Is it needed? I suppose it would depend on the size of the box.

It really depends on the box size. For a box this size, I think 3/4" is sufficient. That is what I did. A well placed brace will be just as effective or more than double thickness.

Ok, I've given the box design another try using 2 RS180's as recommended by cjd.
Pluging everything in to Unibox it gives me a Vb of 39.7L or 1.4 ft3 for the RS180's and a Vb of 4.2L or .15 ft3 for the W15CY-001.

You seem to be discussing a couple of different options. I'm not clear what design or crossover you're working with here. I can only help you with an existing design. For mods to existing design, maybe someone else can help.

[JamesB77]

You seem to be discussing a couple of different options. I'm not clear what design or crossover you're working with here. I can only help you with an existing design. For mods to existing design, maybe someone else can help.

Thank you for the help you've given me so far, it's been very - well - helpful . I have decided to design my own box with drivers that match the center and tower. I'll attempt to design the x-overs. If I find that too daunting I'll have someone design them for me.