DIY MTM Speakers in bookshelves - Choice Questions

[ctf]

Hello,

I have been reading posts here for a while and have learned a ton of valuable information.
I built speakers a long time ago, and was very happy with the results, I would like to do that again.

I understand that speakers are usually better placed away from the back and side walls.
Unfortunately, my current setup (and to help with the WAF) does not allow for that, and I have to put the front and center channels into built-in cabinets.
I have attached a picture so that this is all clearer.

The TV is a 65" JVC DILA TV (12" deep) and the speakers around it are Vandersteen 2CE.
There is also, under the TV, a VCC Vandersteen center channel.

The spaces where the Vandersteen front are currently located are 47"H x 18"W and 12" Deep.
I cannot install the speakers into the next bookshelves, as we have books coming to line these up.
(Some books show already on the bottom of each side)

I would like to build speakers that can mostly fill the space on each side of the TV, and sound great.
The Vandersteen are great speakers, but cannot be used in these conditions therefore I will sell them.

I am thinking MTM designs would be good and allow for some great speakers with ample power.
I usually like to listen fairly loud (neighbors are not an issue since this is a house).
This will be used to listen to music (all sorts) and as a home theater speaker set. (5.1)

Last but not least, I will have to redo a center channel.
I can put it on the bottom, or immediately above the TV. (Vertical space is 6")

Can someone please help me understand which designs would work well for these conditions?
The speakers will be against the back of the bookshelves, and will be "enclosed" on each side as well.
I am not sure which speakers will work best in these conditions.

I truly appreciate all the expertise that is available on this forum and look forward to hearing your suggestions.

Thank you.
Arno

PS: posted on another fora, but I figured this is a good place to start as well. Thank you.

[---k---]

Floyd Toole's book, "Sound Reproduction" has a good explanation of what putting speakers into an entertainment center does. Two affects, it messes with the baffle step compensation (bass) and there are diffraction issues. I posted the graphs here:

https://www.htguide.com/forum/showthread.php?t=34016&highlight=toole

Not all speakers are designed to be out in the middle of the room. CJD has designed all my speakers to be closer to the wall. It is just a matter of reducing the baffle step. (there are still other issues, but....)

For what you show in the picture, I would think an in-wall design would be best. And then put a shelf on either side and fill the shelf up with books so it is a flat surface, just like an in-wall.

There are many in-wall designs to choose from, but I'm partial to these:

https://www.htguide.com/forum/showthread.php?t=32111

The Khancenter would also work well underneath in position.

[ctf]

Thank you for the links, it is indeed very interesting.
I am somewhat aware of BSC and Diffraction challenges, but the graphs really put things into prospective.

Your surrounds look very nicely integrated, and I will have to do something similar in my house since the main viewing couch is against the back wall, about 18' from the TV.

This is not a dedicated HT room unfortunately, so I have to live with this constraint.

Since the space on each side of the TV is about 47"H x 18"W and 12" Deep, I am trying to find a design that can take advantage of this space.
I agree that In-wall design may be best, but they are usually limited in power from what I understand, due to the very shallow depth available.
The Vs have a 8" and 10" woofer/coupler, I wish I could stay in those sizes.

The Vs really give a big sound, but I can tell that there are lots of parts where the sound is "missing".

Thank you for your help and keep the designs coming. :-)

Cordially,
Arno

[---k---]

I agree that In-wall design may be best, but they are usually limited in power from what I understand, due to the very shallow depth available.

You're understanding is a broad generalization and in the case of the ones I linked to is just wrong. They may or may not have as much as your current (several variables need to be evaluated), but limited power is not a valid description.

It sounds like you have some preconceived notions of what you want. I doubt you're going to find something already designed to fit what you want. You might want to contact one of the crossover gurus and see if they will help you come up with a custom design.

[ctf]

It sounds like you have some preconceived notions of what you want.

Well, my lack of "extensive" speaker building knowledge probably biases my wishes in an undesirable way.

I would simply like to be able to replace the Vs with "something" that will be at least as good, and hopefully better than the Vs in their current (bad) position.

Maybe "limited power" should have been better described as "not enough spl".
I am after good spl (All relative, I understand), awesome sound quality, for music and home theater use.
All this while being able to place the speakers on each side of the TV, within the existing space constraints.

I hope that my preconceived ideas are not in the way of these goals.
I do appreciate all the help that is available here, this is what will make this project happen.

Thank you.
Arno

[cjd]

Well, my lack of "extensive" speaker building knowledge probably biases my wishes in an undesirable way.

I would simply like to be able to replace the Vs with "something" that will be at least as good, and hopefully better than the Vs in their current (bad) position.

Maybe "limited power" should have been better described as "not enough spl".
I am after good spl (All relative, I understand), awesome sound quality, for music and home theater use.
All this while being able to place the speakers on each side of the TV, within the existing space constraints.

I hope that my preconceived ideas are not in the way of these goals.
I do appreciate all the help that is available here, this is what will make this project happen.

Thank you.
Arno

Got more specifics on what kind of SPL you're after?

Are you using a sub in the mix at all?

With a 12" depth, there's plenty of space to get big uncompromising sound, but you still need an in-wall design because there simply won't be baffle step to deal with. That's quite do-able, but they're rare.

For "loud" I would highly recommend a 3-way. That lets the woofers go to crap without compromising midrange quality if you desire to push things that far

The 6" vertical space is going to be harder to work with, because for best results you NEED vertically aligned mid+tweet - unless you're almost always listening within 15 degrees off that axis (either direction) where an MTM on its side may do, but you still can't use a BIG driver, which means it's going to be by far the most SPL limited part of the system in a place where it can be the most important.

What kind of amp are you using? Can you set lower crossover point separately for each of your front channels? If so, you probably will want to set it much higher for the center - it's all close enough together that sound will still anchor to the center properly even if not coming from the center.

[ctf]

No specifics on spl unfortunately.
I just got a calibrated mic, but did not have a chance to check anything yet, the AVR is away for firmware updgrade.

I have a receiver Harman Kardon AVR-7550HD (7x110W) used in 5.1 and I occasionally get to 0dB on the receiver volume when listening to music with the Vs.

http://www.vandersteen.com/pages/2celit.html

I do have a 15" Servo Velodyne sub that will get replaced as well, not sure by what yet, but probably DIY.
I would like, if possible, to build a (2?) subs that I could lay behind the viewing couch, against the back wall.
Once again, I wish this was a dedicated HT room, but it is not.

The 6" vertical is immediately above the TV.
I could also use the space below, where the center channel is currently installed. This would give more room for more design choices.

Yes, the front channels can be set separately for crossovers, gains, etc...

Thank you.
Arno

[fbov]

Hello,... I have to put the front and center channels into built-in cabinets.....I cannot install the speakers into the next bookshelves, as we have books coming to line these up....I am thinking MTM designs would be good and allow for some great speakers with ample power....I usually like to listen fairly loud ...This will be used to listen to music (all sorts) and as a home theater speaker set. (5.1)...

Here's a link to a build that had similar constraints. Look midway down page 2 for results.:

http://www.hometheatershack.com/forums/diy-speakers/17710-giving-new-meaning-term-bookshelf-speaker-another-natalie-p-thread.html

In-wall designs are louder than free-standing. Looking at k's link to Toole, the 2pi curve has a big bump at 50-200Hz because it was a 4pi design. It's very possible to remove the bump by increasing output above 200Hz, and that's what an in-wall design does.

The open areas beside the speaker need to be filled, per the bottom pair of FR charts. Books work fine, and are best if staggered somewhat randomly as they then act as a diffuser, a good thing on the front wall.

I will have to redo a center channel. I can put it on the bottom, or immediately above the TV. (Vertical space is 6")
...

I have been converted the hard way - don't fit the speaker into the space, find space for the right speaker ESPECIALLY for the center channel. The lower space, minus the center divider, would be perfect, just use a purpose-build center channel design. If making NatP's or Modula MTMs, this is the right CC, in-wall XO design is post 30. Substitute tweeters are available (I used a D3004/602010).:

https://www.htguide.com/forum/showthread.php?t=11475

More to think about, I know....

HAve fun,
Frank

[ctf]

Here's a link to a build that had similar constraints. Look midway down page 2 for results.:

http://www.hometheatershack.com/forums/diy-speakers/17710-giving-new-meaning-term-bookshelf-speaker-another-natalie-p-thread.html

Someone at HTShack suggested this exact thread this morning as well.
This looks very interesting and is definitely something I could do.

There will be many shelves of books on each outside shelving, where the books are already showing at the bottom.

I understand that removing that bottom center divider is probably the best option. I should not have a problem doing so since I already had to remove the center section where the TV is.
This was before 4 empty bookshelves.

Thank you for the info.
Arno

[---k---]

Here's a link to a build that had similar constraints. Look midway down page 2 for results.:

http://www.hometheatershack.com/forums/diy-speakers/17710-giving-new-meaning-term-bookshelf-speaker-another-natalie-p-thread.html

Thanks for posting that. That is exactly what I was trying to suggest, just with a different speaker.

[ctf]

Indeed, both speaker options are interesting.
I realize that I did not talk budget so far.

Since the front/center channels are the most important typically, assuming a budget of about $600 or so per speaker for the electronics/drivers only, which speaker design would you then suggest?

After checking your Khanspires, they look fantastic.
It seems that they are very well reviewed as well.
Can they be made (crossovers) to work in a cabinet type design that would work for my application?

Thank you for all the help.
Arno

[---k---]

Arno,

The Khanspires, no they can't go in-wall. The matching in-khan-neatos were designed specifically to go in-wall from day one. This is why I linked to them in my first response. The Khancenter was specifically designed to be placed in a quasi-in-wall below a big TV, which seems like it would be very close to what you got and why I recommended that.

I'm not going to suggest one design over the other. The dual midrange of the NatP will have some advantages, while the 3-way of the In-Khan will have other advantages (as CJD alluded to above.) Speakers are all about trade-offs. You'll also have to consider in that equation what you're going to use for a center.

There aren't a lot of other in-wall designs that I'm aware of. Zaph has some nice kits at Madisound. I'm sure there are others.

Flip a coin if you have trouble deciding.

[ctf]

The matching in-khan-neatos were designed specifically to go in-wall from day one

This is probably why I am confused too.
It seemed to me that both the Khan-Neatos and Khan-spires were completely different. You seem to indicate that this is not the case...

I am confused indeed, and there are not many choices to choose from like you mentioned, which actually makes my life a bit easier.

I am simply trying to remove the Vs, and replace them by a DIY proven design since I do not have the expertise to design my own from scratch.
The last thing I want to experience however, is to spend money, time and efforts on doing DIY speakers that will not sound as good as the Vs, in their current placement.

This is why I am trying to understand my options, and what expectations i can have from speakers which seem much smaller than the Vs I have.
I hope this makes sense, somewhat.

Regardless, I truly appreciate your time helping me steer me in the right direction. It seems that I need to find the few proven designs that will work for my cabinet requirements, and build from there.
It is simply hard to look at the designs that are out there, and be able to pick the one that will likely make me the happiest.

This is why your and others help is invaluable to me.
Arno

[fbov]

The fact is that the best driver combinations spawn families of speaker designs. The Kahn series is one. The Modula series is another.

The interesting part is both families use Dayton RS drivers, so there are a lot of tangential designs - unrelated other than driver choice. The NatP's RS180/RS28 driver combination alone has 6 XO designs for free-standing speakers by different designers. There are better drivers, at a price. Ultimate quality level is up to you and your budget.

In many cases, the room will be a bigger factor in sound quality than the specific speaker design. Audio preference is famously subjective - new speakers always sound fantastic - so you won't be disappointed regardless. As long as you stick with quality drivers and popular designs, and choose speaker capability based on your needs, you'll be very happy.

Chief among your needs are in-wall/no BSC designs that include a CC. I've got a pair of freestanding NatP's, but you've found the in-wall versions, and an in-wall Modula MTM CC so I can tell you they are a good combination, as long as an MTM will play loud enough for you. If not, then look at a 3-way like the Kahns. I've never heard them, but I have taken my towers to a DIY event, and they really are very good. There are some great sounding designs out there!

Prices. Just bought parts for a second pair of NatP's for just under $400/pr., timiing it to catch drivers when on sale and using P-core inductors. In-wall's will cost ~$30-40 more. The Modula CC in-wall is roughly $350 by itself; $150 XO and $126 tweeter.

BTW, this all assumes you can build boxes and solder circuits. There are options that don't, if need be.

Have fun,
Frank

[ctf]

Frank,

Like you identified, I believe that the quality will likely be there, no questions.
Playing loud enough is my real concern I suppose at this time.

I really like the Khans, and think that I could tackle such a project, but it seems that they are not made to be in-wall at all, the neatos could be used, but are maybe a bit too small.

Any particular good 3-way project that would work well in-wall/on-wall that you would recommend?

Like I mentioned, my budget is about $600 per speaker without cabinets.
This should afford some flexibility in the choice of drivers.

I can build boxes and solder, no problems there.
Finding the time is likely a bigger issue. :-)

Thank you.
Arno

[ctf]

Gentlemen,

Thank you very much for taking the time to educate newbies like me who are full of good intentions, but lack the knowledge to implement properly.

After reviewing the options that you proposed, and surfing more speaker DIY sites than I can remember in the last few days, I have decided to build some in-khan-neatos for the front and a KkanCenter as suggested here.

It seems that this will bring me the "big sound" that I like, with an awesome quality, without breaking the bank too much.

I will be able to remodel the center divider under the TV to locate the center channel, which will be best.
Then, I will likely build in-khan-neatos surrounds as well once the LCR are done.
My Velodyne 15" sub will need to be replaced as well, but can work on this last since I already have a decent sub. (Not sure what to choose there yet)
This should make for a very nice 5.1 system, which I anticipate will make me very happy.

I will be traveling a bit over the next month or so, but will certainly keep a thread going with my progress once I get started.

Thank you again very much for your help, I anticipate I will need a lot more more very soon...
:B

Arno

[---k---]

I think you made a great decision. I hope you enjoy them as much as I do. CJD and I are here to help as much as possible. Good luck.

And, I would recommend building just the center first to get your feet wet and hear how they sound. I'm not sure the whether your VS are warm, neutral, or bright or whether they are forward or laid back. Whatever. But build one and see what you think and tweaked.

[ctf]

And, I would recommend building just the center first to get your feet wet and hear how they sound.

That is actually a great idea!
I may get very impatient to build the fronts once I hear the center.

Thank you.
Arno

[BOBinGA]

Arno,

Like all narrow baffle speakers, the Vandersteens need room to breathe. From all I've read about them over the years, they are wonderful speakers. But in their current place stuffed into the wall shelves, you are doing them an injustice, so I think you made the right choice to build something much more fitting to the space where they will live. It's best to let the Vandersteens go to a loving home where someone else can give them a big space to play in.

-Bob

[ctf]

Yes, this became obvious when I put the Vs a few feet in front of the bookshelves.
My wife did not agree however. :B

I think that I will be very pleased with this solution.
Since I have all matching fronts and surrounds for the Vs, I anticipate that selling this will finance this build. Even better for the WAF of the new project.

Arno

[ctf]

CJD and I are here to help as much as possible.

Which is one of the reasons why I chose this solution. CJD and yourself have a proven record of getting great products delivered and being extremely helpful to others when needed. I appreciate that in this community.

So here is my first set of questions. :B :B

Center Channel:
My current space under the TV (once I remove the divider) is 55"W x 13"H x 11"D

I see the Khancenter is over 11" deep.
Can I make the total outside depth 11" and recover the lost volume by increasing the Width?
Since I just have 13" High, I was thinking keeping the 10"7/8 Design and increase the width to about 33" if my calculations are correct to keep the same internal volume.

Since I will increase the width (if you say it is OK to do so), would it be helpful to add some mid-range drivers, maybe a couple more RS-180 or RS-150 drivers? (In search "bigger sound" for example)

I imagine that the crossover may not work as-is either and would have to be modified?

Added cost is understood, and OK since this is the most important speaker of the 5.1 system.

Thank you.
Arno

[---k---]

I oversized my center channel. It doesn't need to be that big. Towards the end of the thread, this is discussed. You just need to be able to have a reasonable tunnel behind the mid to connect the two woofer spaces. If you want to keep the same volume you can definitely change the width. Usually, you want to keep the tweeter and midrange the same distances to the edges. So, for a center channel (and only a center) increasing the width is certainly do-able.

You can never just add additional drivers. The crossover is custom designed to fit those drivers. A lot of work goes into it. Adding drivers is a completely new crossover and is not a trivial thing to do.

I don't know how big your room is, but I really don't think you'll need more drivers to produce reasonably impressive sound levels.

[ctf]

Thank you for the clarification.
I will re-read the thread properly, I must have missed that part.

I anticipated this would be the case for the crossover and did not think it would work, but it does not hurt to ask.

As for the big sound, I anticipate you are right.
I actually checked today while listening to music, and I can listen upwards of 105db or so, according to the cheap RS sound meter (C-weight).
Did not have the time to pull the calibrated mic.
This is with my older Onkyo receiver BTW, the HK is still in transit.

Thank you.
Arno

[ctf]

Ryan,

So, in reference to this post you made:Bigger Center RS225, it seems that I could build this with the RS225 and not change much otherwise?
(Still limited to 11" depth)

This would be great, and probably would make me feel better about wanting that "big sound".

If I am being stupid, please do not hesitate to let me know...

Arno

[---k---]

The Khancenter was measured on an infinity baffle to simulate being under a big TV and under a wall. The RS225 center design is intended to be pulled out into the room. There is some reduced BSC, but it isn't inwall. It could probably work, especially with roomEQ provided by most modern receivers. I just don't have experience with that one so can't say for sure. It would be a tradeoff between SPL and sound matching quality.

I think you're also worrying too much about "big sound". The bigger RS225 design has the same mid and tweeter where most of the music lives, and with subs in the mix I think you'll be fine. Bigger is better, but there is diminishing returns. For example, I was very satisfied in my room with my brothers Sietecerocero Ochocinco MTM. With the subs in the mix, they delivered plenty of spl. I feel that many people on the internet tend to go overboard. But that is just me.

[ctf]

I feel that many people on the internet tend to go overboard. But that is just me.

Says the man who has 3-way surround speakers...
:B :B :B

Understood, I will stop worrying about this now and get cranking as soon as I can.

Thank you.
Arno

[BOBinGA]

Guys,
Just to make sure all the bases are covered, the drivers to build the center channel that are available now are NOT shielded.

Arno, if you have a projection TV, are the unshielded center channel drivers going to affect the projector? Since the large Vandersteems were unshieded, I will assume that the new L and R speakers will still be far enough from the projector that they won't cause interference. But the Vandersteen VCC Center was shielded and since it was closer to the projectior than the side speakers, it would not affect the projector whereas the new center might.

Ryan, from your build thread, it looks like you had a projection TV at the time you built the center, but you built it with shielded drivers. Have you tried unshielded drivers that close to your projector?

There are various workarounds for shielding. My son used a pair of unsielded drivers next to an old CRT monitor and he simply used the degauss button every week or so as needed and it was all he needed. He found that moving the speaker or monitor caused the most color problems. Once everything was in a stationary position and he deguassed, it would last for several weeks.

I hope I'm being overcautious, but I thought I should bring up the subject "just in case". You could test by putting one of the large Vandersteens in the lower cabinet once you take the divider out and see if it affects the picture.

-Bob

[ctf]

Bob,
Good point, but mt TV is a D-ILA rear projection and I believe immune to these issues.

What would be the best way to shield a speaker otherwise, when the drivers are not shielded?
Big piece of aluminum between the TV and the speaker?

Arno

[BOBinGA]

Since I've never had a projection TV, I don't know how susceptible they are to magnetic interference. But shielding usually requires gluing a magnet to the back of the speaker magnet in opposite polarity. In other words, push together the main magnet and a bucking magnet that are trying to repel each other. You can get bucking magnets at Madisound, but I'm not sure if PE still has them. I'm not sure how effective a piece of sheet steel or aluminum would be.

But to make sure your TV is not susceptible, try putting one of your Vandersteens on their side as close to the bottom of your set as you can in a similar position as the final center channel would be. The Vs are unshielded and should tell you if it affects the TV. It's pretty obvious. The colors get really distorted in a pattern around the magnetic interference. You usually need the magnet to be about a foot from the electron gun in the TV before it becomes a problem. Good luck. I'm hoping that I'm just worrying too much.

-Bob

[---k---]

The shielded were selected because they offered the performance we were looking for. PE has since discontinued the shielded version and replaced them with very similar performing drivers. CJD has tested a couple of them and found them to be close enough to be drop-in replacements. Mine design is sealed, but the if used in a ported configuration, the box size can be slight reduced.

Only a CRT is affected by unsheilded drivers. a DILA is immune.

[cjd]

FWIW - the RS225 and the RS180 are largely equivalent in performance (in these 3-ways) till about 70Hz. That is to say, everything *above* is equivalent. Unless you've got everything else so optimized that you can start picking apart the small differences.

Also, you do not need to have the woofers share airspace that I know of (in the box that is.) For 11" deep, it may give you a little more open midrange to just go full depth and NOT have a tunnel between woofers.

Today I got data and crossover in the works for some cute little satellites. About 7.4x4.75x3.5" (HxWxD) Goin' small! Looks like they may still do a 100Hz cross to a sub in a pinch.

[ctf]

Also, you do not need to have the woofers share airspace that I know of (in the box that is.) For 11" deep, it may give you a little more open midrange to just go full depth and NOT have a tunnel between woofers.

Good news, thank you.
This will simplify the box too.
I will do a sketchup of the box before I build it, and submit it here for review.

Thank you.
Arno