Center with possible LR builds question

[kjgarrison]

UPDATE:
This thread is a whole lot of people showing great willingness to help a noob create a built-in center in a real PIA entertainment center in conjuction with an IB build in the same EC. The IB build thread is over in the cult, and ThomasW is helping me in both places. (Immeasurably!)

I currently have PSB Synchrony Two floorstanders and hope to have a center that mates up with them, otherwise (if it turns out that I actually can follow directions and build a speaker) I might build floorstanders matching the center. Big difference here is that said floorstanders need to look good, whereas the built-in center and IB will be covered up with speaker fabric.

It appears that whatever center design is used, a no-BSC crossover will be required.

Current contenders for the center are:

Modula NeoDcc. This suggestion came from Thomas. Jon Marsh has posted a preliminary no-BSC crossover. There is a lot of skepticism that a noob can build the XO.

DA Khancenter. Suggested by ---k--- (Ryan). cjd (Chris) has offered, I believe, to do a no-BSC XO.

MaxxL16CC. Suggested by Jed, who also offered to design a no-BSC XO.

Statements CC. Suggested by ThomasW. Needs a no-BSC XO and clarification if it can be made to work as a closed unit.

dawaro's Dayton RS WMTW Center. Suggested by ThomasW. Needs no-BSC XO.

Some quirks about my design possibilities:[/list]

1. I have 9-10" of internal vertical height for a center, and all of these will fit
2. I have a LOT of extra volume available if needed (from width and depth). About 140 liters, in fact
3. A glass LCD will be immediately above the center
4. A front facing 20" wide hole for the IB will be right below the center, but the overall effective baffle height will be 13-14", not counting the LCD and rest of the EC that is.

I probably should mention that I am not an audiophile, and because of some hearing issues, never will be. But that doesn't mean I don't want, appreciate, and am willing to pay for, quality. My wife can't smell, but that doesn't stop her from enjoying eating things she really can't taste.

EDITED/UPDATED 7/9/08



Hello guys.

I just went through this thread, and understood at least enough of it to know I am interested in building a Modula NeoD center to go with a pair of PSB Synchrony Two floorstanders.

Am I correct in thinking that the only only "proper" use of this design is with the one specific box dimensions? I would like to have the option of building L&R be floorstanders later on. Am I correct in thinking that the XO is only designed for the one box size?

If this is the case, perhaps I should look elsewhere for a good center design that can be extended to include good voicing with floorstanders.

Note: this thread was split from the main NeoDcc thread....[list]

[Jed]

Keep the driver layout the same on the same width baffle and extend the height for the floorstander version. This speaker is designed to be turned on its side for LR channels.

[kjgarrison]

Keep the driver layout the same on the same width baffle and extend the height for the floorstander version. This speaker is designed to be turned on its side for LR channels.

That's great! So the baffle dimensions only "matter" in one direction (width which is height for the center)?

What about enclosure volumes? Don't they have to match?

[Jed]

I've done a few tests of the response changes by adding a bit to one side of an enclosure. The result was that it is most important to keep the midrange and tweeter in the exact same layout and the baffle width remain the same.

So, for the CC layout, keep everything as designed. For the tower, rotate everything clockwise or counter clockwise such that the tweeter is close to the edge like in the CC. No longer will the tweeter be at the top, rather it would be off to one side with the midrange to the left or right of it. The box can be up to 60L or so. I can model it for you if you want.



Jed

[kjgarrison]

Correct but the OP doesn't like the idea of using ports, so no reason to use them...

Thomas, I'm confused (again, yes I know) by this port statement. The pictures you supplied with post 127 show a port. :huh:

[kjgarrison]

I've done a few tests of the response changes by adding a bit to one side of an enclosure. The result was that it is most important to keep the midrange and tweeter in the exact same layout and the baffle width remain the same.

So, for the CC layout, keep everything as designed. For the tower, rotate everything clockwise or counter clockwise such that the tweeter is close to the edge like in the CC. No longer will the tweeter be at the top, rather it would be off to one side with the midrange to the left or right of it. The box can be up to 60L or so. I can model it for you if you want.


Jed

That is very generous of you to offer. If it is a lot of time/work/trouble, then I am reluctant to accept. If it's quick and easy, then heck yes! And thank you.

[Jed]

That is very generous of you to offer. If it is a lot of time/work/trouble, then I am reluctant to accept. If it's quick and easy, then heck yes! And thank you.

Quick and Easy. See attached.

[kjgarrison]

Built in? or build and place?

Here is a sketch of the IB project I'm working on (with incredible help from Thomas. Thanks Thomas.)

My questions are about the center speaker. This is the yellow area in the drawing which is not to scale, but pretty close, eyeballing it.

1. The height of the yellow area can be up to 11" approx. Width is ~30" and depth ~22". Would it be better to build the NeoD CC and slide it into the opening, or would it be better to build the NeoD as part of, and into, this center space? There is plenty of MDF (2x 3/4" on all sides, and additionally OSB 1x 3/4" involved with the IB) in this center space, so making a baffle for the front of a center would be only a small amount of additional material and work.

2. Since my IB will be venting into the basement, and since the space down there is for guests, there will be a few weeks each year when the IB can't be used. My understanding is that with the IB, I wouldn't need to worry about porting the NeoD CC, but for those few times when I can't use the IB should I build the NeoD CC with a port? If so, can it be front ported?

3. For the same reason, should I try to push the volume of the NeoD? I could get the most volume if it is "built in".

4. Given the enclosure and the flat surfaces above, below, and on both sides, I'm thinking that there needs to be no BSC. Will the crossover design in this thread be appropriate for this arrangement, or will some adjustments be required?

Thanks for any help. And thanks to Jed for the modelling.

[kjgarrison]

Jeez. Forgot the sketch.

[Jed]

If you need a no bsc version you might look for a different design unless Thomas has one somewhere... but I don't think he does. Hopefully I'm wrong about that.

[kjgarrison]

If you need a no bsc version you might look for a different design unless Thomas has one somewhere... but I don't think he does. Hopefully I'm wrong about that.

Oh. Man the NeoD CC is just the right height for my space! :cry:

[Hdale85]

There will someday (maybe) be a non BSC version but Jon has been super busy with work and hasn't even stepped into the forums for a long time.

[Dennis H]

Does your receiver/prepro have built-in EQ? That can compensate for the BSC.

[kjgarrison]

Does your receiver/prepro have built-in EQ? That can compensate for the BSC.

Audyssey MultiEQ in Denon 4308 CI. So I'm back on track?

[Dennis H]

Audyssey MultiEQ in Denon 4308 CI. So I'm back on track?

Yup, Audyssey should be able to handle that. BSC is just a gentle 6dB or so boost from 800 or so down to 200 or so. It's needed when the speaker is out in free air but not so much when it's on a wall or built into a cabinet.

Crossing to a sub, I'd be tempted to build it into the space you have, sealed with no port. You could build the cabinet and shove it in the hole but you'd probably have to stuff the area around and behind the cabinet to prevent cavity resonances.

[kjgarrison]

Yup, Audyssey should be able to handle that. BSC is just a gentle 6dB or so boost from 800 or so down to 200 or so. It's needed when the speaker is out in free air but not so much when it's on a wall or built into a cabinet.

Crossing to a sub, I'd be tempted to build it into the space you have, sealed with no port. You could build the cabinet and shove it in the hole but you'd probably have to stuff the area around and behind the cabinet to prevent cavity resonances.

Very good news. Thank you Dennis.

Now.

I can make the height of the baffle to NeoD CC specifications (9"), and of course I can make the driver placements to spec as well. But the width will be quite a bit more than spec, and the depth can almost anything up to ~20-23".

Will these 'out of spec' dimensions require a different crossover setup?

Is there another design I should be looking at?

btw, my L&R are PSB Synchrony Twos that crossover at 2200, fwiw. Should I be looking to make a center that more closely matches this?

[kjgarrison]

If you need a no bsc version you might look for a different design unless Thomas has one somewhere... but I don't think he does. Hopefully I'm wrong about that.

Jed, thanks. Do you have any suggestions for a different design? Of course the posts above appear to have taken the "no bsc" issue off the table, but what about my question about the crossover?

[Jed]

The best one can do when deviating from the original design is work a simulation that "might" work based on a general understanding of BSC or of course measure in the given environment. I once ran a few tests with my MaxxL16CC with it placed on a stand, large TV cabinet that acted like a a partial IB, and on a TV cabinet but with space around it. I found that the frequency response changed quite a bit. And that was after NOT modifying the cabinet dimesions like you are planning on doing. So, you will more than likely have to accept a response that deviates from the original, or tune it by ear by fiddling with the tone controls of your receiver. Maybe an Inwall type center channel design would be more suitable for your needs? Isn't CJD working on such a speaker?

[---k---]

The Khancenter was designed to fit under my 50" TV (picture in the first post of the design thread). So, getting close to what you're doing, but not an in-wall. CJD's in-wall is 3 identical vertical speakers or behind a screen - probably not what you're thinking.

[kjgarrison]

The best one can do when deviating from the original design is work a simulation that "might" work based on a general understanding of BSC or of course measure in the given environment. I once ran a few tests with my MaxxL16CC with it placed on a stand, large TV cabinet that acted like a a partial IB, and on a TV cabinet but with space around it. I found that the frequency response changed quite a bit. And that was after NOT modifying the cabinet dimesions like you are planning on doing. So, you will more than likely have to accept a response that deviates from the original, or tune it by ear by fiddling with the tone controls of your receiver. Maybe an Inwall type center channel design would be more suitable for your needs? Isn't CJD working on such a speaker?

The more I read and learn from you guys (and thank you very much for all the help), the more I think that I should simplify my life as much as possible by starting off with a setup that has no BSC and that people here are familiar with for help with tweaking down the line.

I'm just trying to design this whole IB/center thing so I can get started on construction. The current design has a 9.5" vertical 'hole' for the center, so I'm tying to find something close to that. I'm thinking that if the design has no BSC then the dimensions of the baffle really don't matter. Maybe the relationships between drivers matters.

I'll take a look at your MaxxL16CC

[kjgarrison]

The Khancenter was designed to fit under my 50" TV (picture in the first post of the design thread). So, getting close to what you're doing, but not an in-wall. CJD's in-wall is 3 identical vertical speakers or behind a screen - probably not what you're thinking.

Correct. I need horizontal and at ~9-10" height. Maybe could go to 11" but it would be crowding my IB specs.

Thanks. I'll look at your Khancenter.

[Gray]

Hello

The speaker your after is Modula MTM Center Channel. It's the only one here that has no BSC that I know of and it's the size your after.

[ThomasW]

kj,

The physical height of the baffle itself is somewhat irreverent in this instance, since the ET and the components it contains form the real baffle.

FWIW, a little bird told me a non-BSC version of the NeoDcc crossover can be created in about 10 days.

[Jed]

Beyond looking just at the idea of no BSC, there still will be the variable of the entertainment unit forming a IB, since the speaker will be set into the unit, thus changing the diffraction signature significantly. I can't say how significant the differences in response from original to the IB version with BSC would be without modeling it or measuring. However, the nonBSC speaker will get you closer but WILL NOT address the diffraction change issue because the original measurements are based on a cabinet with baffle edges. I bring this point to you so you know that a non-BSC design does not solve your problem completely. How particular you are about it is a personal choice. Most situations in HT involve some sort of compromise. I like the recommendation of the Modula MTM in wall speaker- but even that I'm not sure was taken with measurements on an IB.

[Hdale85]

kj,

The physical height of the baffle itself is somewhat irreverent in this instance, since the ET and the components it contains form the real baffle.

FWIW, a little bird told me a non-BSC version of the NeoDcc crossover can be created in about 10 days.

Hmm how is Jon doing? Whens his next vacation? How long till he retires? :B

[ThomasW]

The Modula MTM In-wall wasn't designed for horizontal (center channel) operation.

I'm reasonably sure we can modify the NeoDcc design to optimize it's operation for in-wall use.

[kjgarrison]

Hello

The speaker your after is Modula MTM Center Channel. It's the only one here that has no BSC that I know of and it's the size your after.

Thank you Gray. I went to the Modula MTM Center thread, and I must say it's a little discouraging to see the Jon Marsh calling it "making a silk purse out of a sow's ear".

My alternative to doing this DIY project is buying a $1300 PSB Synchrony Two Center and sticking it in this opening. There will be nothing I can do, even with the help of all the expertise present here, to overcome the problems with the PSB.

I am looking for maximum "adjustability" and quality. It does not have to be a low budget build (not that I want to throw money away for nothing), but there could be some nice components included and still be far below $1300 and be hopefully better sounding.

[kjgarrison]

kj,

The physical height of the baffle itself is somewhat irreverent in this instance, since the ET and the components it contains form the real baffle.

FWIW, a little bird told me a non-BSC version of the NeoDcc crossover can be created in about 10 days.

Excellent. It is amazing how emotions ebb and flow with all of this!

I love little birds. We have a big bird feeder and habitat right on my back deck. Seriously, we keep them alive for these Wisconsin winters.

"can be created in about 10 days"

What do I need to do, if anything, to help with this? Just be patient?

BTW, there is one (maybe not so) little glitch in the BIG BAFFLE concept. The top edge of the IB opening forms the lower edge of the center, and the IB opening is 20" wide and about 20" deep. So, half of the center will be in a wall and half will be sticking out ~20". Just thought of that.

[ThomasW]

I went to the Modula MTM Center thread, and I must say it's a little discouraging to see the Jon Marsh calling it "making a silk purse out of a sow's ear".

Jon statement was generic regarding any & all MTM center channel designs, not just the Modula MTM center....

In a sense, trying to make a good MTM center is a little bit of trying to make a gold purse out of sow's ear- the "right" way to do it would be a WMTW, with the MT vertical between the W's;

And that's but one reason the NeoDcc was created.

BTW, there is one (maybe not so) little glitch in the BIG BAFFLE concept. The top edge of the IB opening forms the lower edge of the center, and the IB opening is 20" wide and about 20" deep. So, half of the center will be in a wall and half will be sticking out ~20". Just thought of that.

Does the top front edge of the IB sub stick out farther than the front of the TV? Maybe you could create a side view of the proposed ET with sub and center and TV?

BTW, the size of the box for the center channel is relatively unimportant since you'll be running it in the 'small' setting in your system

[kjgarrison]

Jon statement was generic regarding any & all MTM center channel designs, not just the Modula MTM center....

I knew that.

.... And that's but one reason the NeoDcc was created.

I suspected that.

Does the top front edge of the IB sub stick out farther than the front of the TV?

The TV is on a wallmount inside the upper box. It is almost flush with the front of the center 'hole' and the IB. The TV might be 1/2" behind, but it can be adjusted another 1/2" either way.

The center section (about 1/3 of the total width of the EC) sticks out about 6" in front of the left and right sections.

Here is a picture with the rough outline of the IB and the place for the center. The center will be as tight of a box as any, maybe moreso. In addition to the 5/8" to 3/4" plywood that is already there, there will be at least 2 layers of 3/4" MDF all around. Unless I have to take some away for the height of a center, there will be 2 x 3/4" MDF and 1 x 3/4" OSB between the center and the IB 'hole'. But as you can see the speakers for the center will all be right over the IB hole. You can see that the part of the EC to the right and left is about 6" farther back. Except for the sides, everything in the picture below the TV will be gone (drawers and low center opening) all the way to the floor.

[IMG][/IMG]

[kjgarrison]

here is a 2-D view of the front of the IB/center project. It's Google sketchup. I guess I should add the other cabinets and the TV, at least crude outlines.

[kjgarrison]

I am trying to see if I can finalize the 'box' part of the design of the center/IB combo and get cut sheets drawn up.

I am beginning to understand that the height and width dimensions of the baffle probably are relatively unimportant, since the 'baffle' includes the TV and other nearby flat surfaces. 'Unimportant' as long as the dimensions are at least wide/high enough to place the drivers correctly per NeoD CC specifications.

My issue is that my height and width are much more than the 9" height of the NeoD CC. My height and width presently are 13.25" and 45". This is from the bottom edge of the TV hole to the top edge of the IB hole for H, and the entire width of the center section of the EC for W.

What about placement of the center speaker's drivers? I am assuming that they need to stay exactly as shown for the NeoD CC, with the same distances, etc.

If this is accurate, then I can move ahead with physical design. I do need to know if I should aim for a certain internal volume of the center box, or if it just doesn't matter.

Also if it is accurate I can look at another design later on if the 'No BSC' crossover for the Neo doesn't work out.

[ThomasW]

'Unimportant' as long as the dimensions are at least wide/high enough to place the drivers correctly per NeoD CC specifications.

Correct...

Center the dome midrange and tweeter cluster on your board. Then maintain the relationship of the drivers to each other, same spacing, etc.

[kjgarrison]

The "hole" for my center built-in currently would be ~140 liters.

I played around with the woofers for the NeoD (HI-VI D6.8 ) in Unibox, and the box size acts like an IB.

So I'm thinking the box is too big. Should I just layer in MDF to get it down to a max of ~40 liters? I'm thinking if I don't fill up the space with something solid the voids will resonate and cause all sorts of problems. But I'm worried that too much mass will soak up too much of my IB output!

Also, there will be times when the IB sub can't be used (basement is also the guest quarters), so I'm thinking porting would be a good idea as long as it can be front ported.

Solution(s)?

[ThomasW]

No amount of mass will adversely effect the output from the IB.

Let's problem solve the center channel once you've finished the IB, and we have a finished NeoDcc crossover schematic from Jon.

[kjgarrison]

No amount of mass will adversely effect the output from the IB.

Let's problem solve the center channel once you've finished the IB, and we have a finished NeoDcc crossover schematic from Jon.

Thanks. I'm fine with the sequence you suggest, however the IB build has some flexibility of dimensions to accomodate the center. If you feel that it is safe to assume that the NeoDcc is going to be it, and I won't have to allow for some other center's dimensions, then I can proceed with the combo as currently designed.

If only I could get Scott at Fi on the phone, I could order the IB 18s. Been trying for over a week.

[ThomasW]

If only I could get Scott at Fi on the phone, I could order the IB 18s. Been trying for over a week.

They don't do any business by phone. Use the email address in the Fi thread on the cult forum

[kjgarrison]

Let's problem solve the center channel once you've finished the IB, and we have a finished NeoDcc crossover schematic from Jon.

Thomas, as I continue to design the IB/center combo, there is a specific order or sequencing in which the work needs to be done. The reason for this is that because I can't use clamps for the most part, I have to sequence the building of many of the walls (for example, the height of the center) in a way that gives me clearance to put in the screws.

So minor problems with the center can surely wait, but more major things need to be known now.

Bottom line: I need to know what volume to make the center, or at least what the maximum volume it should be is. Early in the Neo thread Jon discussed and modelled a 40 liter net volume box. Should I use that volume? Recall that I'm starting out with about 140 liters of volume in the 'center' space above the IB.

I also need to know if it is better to add volume with depth vs width and if there is an 'ideal' ratio of any of the 3 dimensions to shoot for.

Also, I need to know if the volume and/or proportions of this center should try to approximate any particular floorstander box that would be used for the possible L&R builds later on.

PS: talked to Scott and the Fi IB 18's are on their way!

[ThomasW]

I thought this graphic represented fixed dimensions?

Jon's reference to 40L related to using the Parts Express Box

[kjgarrison]

I'm not sure what you mean by 'fixed', but the only fixed dimensions in that graphic are the yellow shell of the EC, the floor, and the joists.

The MDF (gray) and the OSB are the current design for the IB. Even those dimensions could be adjusted an inch or so if the center dimensions require it.

The center speaker's "hole" at ~140 liters is obviously way too big. My plan is to build up the back wall and side walls layer by layer (MDF) of the center hole to create the targeted overall volume and proportions of the center, but I need to do this early in the assembly process so that I can get in there for screw placement. In fact the very first board to be placed will the the top of the center speaker's enclosure, and the entire center will be built before the preassembled IB box gets slid in.

The height of the center hole's opening as shown is 9.5". Add a couple of inches above and below (below: to the top of the IB hole, and above: to the bottom of the TV hole), and the height of the center's baffle is 13.25".

This height could be made more or less by changes in the IB. But I'm thinking that with the (no) BSC crossover version it doesn't matter. I just need to preserve enough room on the inside for drivers, and I have more than enough for that.

In Jon's original announcement of the NeoDCC he mentions David Roberts Three way WTMW if space is not an issue. But I couldn't find a no BSC crossover and it seems that the NeoD is higher quality. Although maybe the crowding of the drivers in the Neo, which requires the felt on the front, wouldn't be an issue. But this is off the point, and unless you recommend something else, I'm happy with the Neo. Even "something else" would still require predetermining the targeted final volume and dimensional proportions of the center.

I'm not asking you to do a bunch of calculations (at least I don't think I am). Just tell me an acceptable range for the net (or gross) internal volume and the relative proportions of width to depth. Even if it is only "make it deeper than it is wide if you can". Or, "just don't make the depth and width equal".

And I can go from there.

[ThomasW]

I'm not sure what you mean by 'fixed', but the only fixed dimensions in that graphic are the yellow shell of the EC, the floor, and the joists.

Didn't know that, I thought all the dimensions were fixed.

The dawaro WMTW center can play louder and lower than the NeoDcc. This is a function of the 8" midwoofers. Since you have that large space available it might be a good idea to consider this speaker given your statement about not being able to run the sub all the time.

I'm sure Curt C would provide a non-BSC version of the crossover if asked. In addition the crossover used in this speaker will be considerably less expensive and MUCH MUCH easier to build compare to the NeoDcc, which is a nightmare to build given the use of the copper foil inductors.

FWIW, I talked with Jon briefly yesterday and he indicated serious concern about an absolute n00b being able to build the NeoDcc crossover.

If you want to hedge your bets design IB factoring in the size of the dawaro WMTMW, if you change your mind the NeoDcc will easily fit.

[cjd]

The Khancenter might also be up to the task as-designed. Just yet another option for ya.

[ThomasW]

Hey Chris, would you do an in-wall XO design for that speaker?

Seems like all the center channel designs really need that as an option.

[kjgarrison]

The Khancenter might also be up to the task as-designed. Just yet another option for ya.

Thanks. I have looked at the Khancenter, and I can't figure out if I can make room for it vertically.

The only baffle diagram I have found is this one:

http://www.htguide.com/forum/attachment.php4?attachmentid=12184

The problem is that I have plenty of vertical space for the outer holes but limitation regarding inner clearances.

My design currently has 9.5" height internally, but I can increase that a little. I thought I could do more, but I realized I'm limited by the IB drivers' diameters. I might be able to get the center inner height up from 9.5" to 10", mabye even to 10.5".

The diagram of the Khancenter baffle adds up to 10.876" vertically, and the holes look like they use up almost all of that. But these are outer holes, I'm thinking; and the through holes will require much less 'inner' height. No radii of any of the holes is shown, so I cant really figure it out.

With regards to the XO, I know the one you worked up previously was a 'partial' (my word for it) BSC because the TV was just above the CC. My situation is similar with the TV immediately above. But as you can see from the diagram, I have the big opening for the IB right below. Not quite the same as the situation you dealt with, but maybe not really the same as a total in-wall setup either.

[kjgarrison]

Didn't know that, I thought all the dimensions were fixed.

The dawaro WMTW center can play louder and lower than the NeoDcc. This is a function of the 8" midwoofers. Since you have that large space available it might be a good idea to consider this speaker given your statement about not being able to run the sub all the time.

I'm sure Curt C would provide a non-BSC version of the crossover if asked. In addition the crossover used in this speaker will be considerably less expensive and MUCH MUCH easier to build compare to the NeoDcc, which is a nightmare to build given the use of the copper foil inductors.

FWIW, I talked with Jon briefly yesterday and he indicated serious concern about an absolute n00b being able to build the NeoDcc crossover.

If you want to hedge your bets design IB factoring in the size of the dawaro WMTMW, if you change your mind the NeoDcc will easily fit.

I have tons of volume, but I don't have as much room as I thought vertically. See the other post about vertical clearance above.

Still this speaker, while it has a 12.5" high baffle, only appers to need 9.515" total height for clearance of the through holes on the inside. That would put the edge of the through holes right at the edges of the top and bottom, so I'm sure a little extra clearance would be needed.

Now, bottom line: Which of these will make the best sounding front stage if I go ahead and build the center and L&R floorstanders?

Which is most likely to work well (enough) with my current PSB floorstanders?

I appreciate the XO nightmare warning, but if there is a difference in quality, that is the determining factor. I can get some help if I need it. Besides I like to learn. And I'm extremely focused and a perfectionist when doing anything. (Good traits, I'm told, in a surgeon.)