Center with possible LR builds question

[cjd]

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.

If I ever get around to it I'll have an in-wall variant based on what I'm using in my HT. Which I really should get around to doing. Almost got there this last weekend but was suffering from stress headaches most of it and really didn't feel like dealing with white noise for measuring.

A true in-wall, I should look over the data again. Problem is I really don't know how much baffle step it has (if any) as it is to be able to convert to an in-wall option. It's designed rather specifically for use under a big glass box, and that's how it was measured (though it was a big sheet of foam-core I used I think). I measured without the "extended baffle" but not in-wall.

[ThomasW]

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.)

The NeoDcc is currently Jon's most sophisticated design. But even in a tower sized box it will be a little bass shy compared to true "full-range" systems given the limited displacement of the midwoofers. In a tower sized box it would have bass at least comparable to your existing mains.

Something to consider......

Once you've run your IB for a while, the system will sound VERY strange in those situations where you're not able to run it. The mains will sound thin and lacking. If instead of building the NeoDçc mains as towers you built them as small boxes sitting on bass bins, your fallback situation when the IB couldn't be used wouldn't be such a massive change.

And now for something completely different...

I would be remiss if I didn't mention "The Statements" series for your consideration. I'm sure Curt would modify the center XO for your needs. And overall the crossover build for any of the Statements series is easier than the NeoD.

There's something magical about ribbon tweeters. They have an 'air' or 'presence' not found in other tweeters. The reason they aren't used more frequently is due to cost, the fact the ribbon element is fragile, and the somewhat limited vertical dispersion.

[---k---]

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.

I honestly have no clue what your vertical limits are. I haven't been able to keep up and am confused.

But as for the Khancenter, Yep, 10.876" is the total height. That is squeezing it down as much as can be. The frames overlap the top and bottom as it is. with just a little 3/8 roundover on the edge that touches each driver. The driver diameters can quickly be found at PE.

[Jed]

I'm sure Curt would modify the center XO for your needs. And overall the crossover build for any of the Statements series is easier than the NeoD.

.

I'd have to disagree with you on this one Thomas, unless they are built to go on a stand or as floorstanders. The Statements won't work in a IB situation because of the transmissin line open back design built into all the measurements. Where would the open back radiate? Therefore it would be a complete redesign of the crossover in my opinion.

Just my 2cents.

Jed

[kjgarrison]

I honestly have no clue what your vertical limits are. I haven't been able to keep up and am confused.

But as for the Khancenter, Yep, 10.876" is the total height. That is squeezing it down as much as can be. The frames overlap the top and bottom as it is. with just a little 3/8 roundover on the edge that touches each driver. The driver diameters can quickly be found at PE.

Thank you for your help.

Here is the scoop. My current internal vertical dimension is 9.5" (This is just a drawing, not an actual physical box.) This could go up to around 10.25", maybe a little more, if necessary.

Looking at the spacing between the RS-28 and the RS-150, and adding the radii of the internal hole for each I come up with a minimum requirement of 9.38" on the back of the baffle. Assuming an additional 0.50" (0.25 at the top and at the bottom) would be enough, I can easily make the Khancenter work ... at least from the dimensions standpoint.

I already have 13.25" on the outside, and with the additional 0.5", I'll have 13.75" vertically. The LCD is right above, and the top part of the IB "hole" is right below. My understanding is that this height is the most important dimension other than driver distances for this center. So, I don't think any of the existing crossovers will work for me.

At least the NeoDcc has a no-BSC crossover, although Jon didn't seem to be totally satisfied with it. Not sure about that, though.

Bottom line: any of the 3 current nominees will 'fit' (NeoD, Khan, dawaro WMTMW). Waiting to see if the Statements will be added to the list ... or not.

[Jed]

I'll do a noBSC version of my MaxxL16CC and it will fit no problem. Plus it is optimized for sealed enclosures so the box design isn't compromised if relocating a port. I've also measured the effects of using my speaker with different environments. One was on a stand, and the other was with an IB below the box. You can see the effects of those measurements here:



And the In Room measurement FR with speaker above a TV environment with open space around the top of the enclosure:



Here's the In Room measurement FR with the cabinet mounted on a stand with open space all around the cabinet:



I'm also working on a new HT system (MTMWWWW, TMWW, WMTW, etc) using Hivi D6.8, TB W4-1337 and the new Vifa XT25 double magnet tweeter with a release date of around late August or early September. PM me if interested.

Sure, right when you were about to make a decision 5 more pop up.

[cjd]

Internal dimensions on the Khancenter are 8 7/8 (3/4" box wall width x 2) so you've got plenty of room.

I'll see if I can extrapolate how much BSC it has and arrive at a "noBSC" version, if it's still of interest.

[ThomasW]

The Statements won't work in a IB situation because of the transmissin line open back design built into all the measurements. Where would the open back radiate? Therefore it would be a complete redesign of the crossover in my opinion.

All speakers require a redesign of the crossover to run in-wall, the Statements would be no exception.

IMO, in this particular situation the any sonic compromise from enclosing the mid shouldn't be much of a problem, since he has ~20" of depth to attenuate the pressure of the rearwave.

[ThomasW]

I'll see if I can extrapolate how much BSC it has and arrive at a "noBSC" version, if it's still of interest.

Given how often this request is turning up, it would be nice to see this option available for all our Missions Accomplished designs...

[Jed]

IMO, in this particular situation the any sonic compromise from enclosing the mid shouldn't be much of a problem, since he has ~20" of depth to attenuate the pressure of the rearwave.

Right, and I'm sure Curt will chime in, but the rear wave/dipole effect was used to "voice" the speaker. Remember all the times Curt told people building the Statements not to mess with the chamber one way or the other because it drastically changes the sonic character?

[---k---]

Internal dimensions on the Khancenter are 8 7/8 (3/4" box wall width x 2) so you've got plenty of room.

I'll see if I can extrapolate how much BSC it has and arrive at a "noBSC" version, if it's still of interest.

Ahhhh! Just repost the current crossover as a noBSC one and see how many people notice.

(I'm guessing it is very close already.)

[kjgarrison]

All speakers require a redesign of the crossover to run in-wall, the Statements would be no exception.

IMO, in this particular situation the any sonic compromise from enclosing the mid shouldn't be much of a problem, since he has ~20" of depth to attenuate the pressure of the rearwave.

at least that much depth, plus a lot of width to yield up to 140 liters of volume

fwiw

I heard some ribbon speakers recently and liked them a lot. If the statements can work in my situation, I am interested. I notice that the internal height is exactly 9.5". I wouldn't have to redo anything on the IB.

I can see why a sub is going to be important unless one of these designs can reach down into the 40's at least.

[ThomasW]

The only possible 'deal breaker' with regard to using the Statements center with a sealed mid is balancing the output of the drivers. The little Tangband has the lowest sensitivity of all the drivers in the system, and Curt uses it's rearwave to augment the output. Personally I don't see this as an insurmountable situation, but I'm not the designer...

Were you to run the large tower Statements as the mains, you'd have a lot more bass output for those situations were the IB couldn't be used.

[kjgarrison]

The only possible 'deal breaker' with regard to using the Statements center with a sealed mid is balancing the output of the drivers. The little Tangband has the lowest sensitivity of all the drivers in the system, and Curt uses it's rearwave to augment the output. Personally I don't see this as an insurmountable situation, but I'm not the designer...

Were you to run the large tower Statements as the mains, you'd have a lot more bass output for those situations were the IB couldn't be used.

Hmmm....

I just had a thought. I should look at the towers that go with all these options. The towers I have have extrememly high WAF. She likes their sound and she especially likes it that they are smallish. A 5' tower is going to be hard to sell to her.

Should I post something on the statements thread asking Curt about these questions?

[ThomasW]

Should I post something on the statements thread asking Curt about these questions?

Might just send him a PM requesting he look at what's being discussed in this thread.

[kjgarrison]

Might just send him a PM requesting he look at what's being discussed in this thread.

Done.

[Curt C]

I thought it best to respond to your message here...

Hi Curt,

I have a thread going and there are a couple of questions we are hoping you might answer.

They are:

1. Can your Statements Center be made to work as a closed box? (I am doing a built-in center in conjunction with an IB build, and whatever I do for the center has to be closed, or maybe front ported.

2. If the Statements Center can be made to work, can you design a no-BSC crossover for it?

An excerpt from my write up on the Statement Center Channel:
"Center channel speakers represent a challenge to the designer as there are so many environmental options: Above, below, or behind the screen, placement adjacent to the large screen and other surfaces, or tucked inside a HT cabinet: All permutations will affect the resultant sound is some form or another, due to differences in the apparent baffle size, diffraction effects, etc. As a nod to all possible permutations, I voiced it with the design axis perpendicular to the plane of the baffle and sitting on, but not flush with, a 24” x 18” base".

Consequently, the Statement Center channel may provide acceptable performance with no modification in your application. However if a further reduction in BSC is required, the changes to the networks shown below will result in removing approximately 2 dB of BSC from the original design. The woofer inductor value is changed from 7 to 5 mH, and the values of the mid and tweeter resistors are changed or eliminated, making this a simple to implement, and fairly cost effective design option.

As far as vented or sealed is concerned, the proper choice will be dependent on at what frequency you cross them over to the sub.

If you apply an 80 Hz 2nd order BW to a sealed RS180, you will closely emulate an 80 Hz 4th order acoustic LR transfer function. The vented design also results in a near 4th order LR function, but at an fc of 67 Hz.

If, on the other hand, you choose to cross to the sub at say, 45 Hz, then the vented design closely emulates a LR 4th at that fc, while the sealed system would roll off considerably higher, at 65 Hz.

Caveat: The low BSC design is modeled only, and no voicing was done. Regardless, some tweaking of values may be required in any case to match your particular room environment.

C

[ThomasW]

Curt thanks for chiming in....In this situation the idea of the performance being somewhat compromised is a given as it is with any 'built-in' design.

Looking at the crossover designs and the statement quoted below about gain in the primary Statements thread, do you foresee any unsolvable level matching issues running the single mid in the center in a sealed enclosure? (FWIW, yes I realize you're referencing the double TangBand design in the quote, and that there's a (1 ohm/8 ohm L-pad) in the center channel midrange schematic )

Thanks for your input
Thomas

but they do exhibit at least one dipole-like attribute: They have a gain of roughly 4.8 dB on axis over a monopole design.

[kjgarrison]

Hmmm....

I just had a thought. I should look at the towers that go with all these options. The towers I have have extrememly high WAF. She likes their sound and she especially likes it that they are smallish. A 5' tower is going to be hard to sell to her.

Well, I should have looked at the height of the floorstanders sooner. It would have saved many generous people here of a lot time and bother.

I apologize for not doing so.

Even though the centers will all work, and even though it is no certainty that the matching L&R speakers will ever be built, I have to at least keep the option open. The Khanspires and Statements are simply too tall. It appears that the Mini-Statements and the center we have been discussing match up, so this combo is still in the mix, pending answers to some questions of Thomas' that I don't even understand.

I am not sure if any of the remaining candidates have a cabinet that can be purchased, but if so that would be highly desirable.

The towers for dawaro WMTMW appear to be a good height. I'm not sure what box might be used for L&R floorstanders for the NeoD.

I think the Maxx speakers offered by Jed are not too tall also, but I the graph Jed showed makes me think these speakers would always need to have the IB sub. It isn't clear to me how low these designs need to go on their own.

[Curt C]

Curt thanks for chiming in....In this situation the idea of the performance being somewhat compromised is a given as it is with any 'built-in' design.

Thomas

Good point Thomas, and one I'd entirely overlooked. ops: Thank you for bringing this to my attention.
The open back mid does provide some reinforcement of the power response which would be lost in a sealed mid design. If the application debated here would have some outlet for the open back, say behind the entertainment center, or behind the screen, it may still function as intended. Raising the value of R2051 effects frequencies above the open back passband, so at least in theory, it would have little positive effect. I believe this would certainly qualify as a case where a model doesn't provide all the answers, and actual experimentation would be the best solution. Unfortunately, I no longer have this speaker in my posession to evaluate. Simply sealing the back IMO, would degrade the midrange quality. At the very least the back should be open and and loaded by some larger volume to absorb or direct the energy.

C

[ThomasW]

Thanks again Curt.... :T

Given the WAF issues with large mains means the NeoDcc is the best choice for the center and best match for the existing mains.

Tower height mains based in the NeoDcc design would provide a little more bass output compared to the existing speakers, but the cabinets would be 9"

[kjgarrison]

Good point Thomas, and one I'd entirely overlooked. ops: Thank you for bringing this to my attention.
The open back mid does provide some reinforcement of the power response which would be lost in a sealed mid design. If the application debated here would have some outlet for the open back, say behind the entertainment center, or behind the screen, it may still function as intended. Raising the value of R2051 effects frequencies above the open back passband, so at least in theory, it would have little positive effect. I believe this would certainly qualify as a case where a model doesn't provide all the answers, and actual experimentation would be the best solution. Unfortunately, I no longer have this speaker in my posession to evaluate. Simply sealing the back IMO, would degrade the midrange quality. At the very least the back should be open and and loaded by some larger volume to absorb or direct the energy.

C

The back could indeed be opened up to the very large opening behind the screen (but still in the EC.) It is ~515 liters, minus some wood for the mounting of the TV. At least an additional 400 liters in addition to the ~140 liters available in the space already allocated to the center is available.

The TV doesn't completely block the opening. There is ~2" above and on the sides, and about 0.5" below, all destined to be covered with speaker fabric. It does, however, attenuate the sound of it's own rear firing speakers.

[ThomasW]

If there's 5" of space behind the TV a 90 degree PVC angle coupling can be used to vent the midrange enclosure. But I'm not convinced this level of 'heroics' would be necessary.

The towers for dawaro WMTMW appear to be a good height. I'm not sure what box might be used for L&R floorstanders for the NeoD.

NeoD options are a custom tower box, or the PE box sitting on a custom bass module(aka speaker stand). In either instance I'd put in a side firing 8"-10" driver to augment the bass output when the IB wasn't being used. The reason for this is the HiVi 6.8 drivers in the NeoD just can't reproduce much low bass

[kjgarrison]

If there's 5" of space behind the TV a 90 degree PVC angle coupling can be used to vent the midrange enclosure. But I'm not convinced this level of 'heroics' would be necessary.

NeoD options are a custom tower box, or the PE box sitting on a custom bass module(aka speaker stand). In either instance I'd put in a side firing 8"-10" driver to augment the bass output when the IB wasn't being used. The reason for this is the HiVi 6.8 drivers in the NeoD just can't reproduce much low bass

It sounds like you're convinced that the NeoD is my best option.

and

Therefore, so am I. ;x(

Thank you Thomas, and everybody for that matter. It is very much a relief to have a final decision.

I need to see what these 'custom bass module/speaker stands' look like. These are dangerous WAF waters, you know. Is this what I have seen you refer to as a "bass box"?

BTW, the amount of time when the IB can't be used, combined with the fact that music/TV is much less likely to be played when company is here, makes me want to forgo trying to make something that sounds OK without the IB. Even right now, the speakers I have are making my keyboard, mouse and the chair I am sitting in vibrate with the bass, and I am upstairs! And they only have 5.25" (or is it 5.5"?) woofers. I'm a little scared of the Fi IBs due to be delivered today 8O ! (jk)

I saw your post on the NeoDcc thread about the MD38T cabinet. I must say that both my wife and I like the look of curved cabinets, though (like the PSBs.) I have seen sort of "get 'em while they last" posts about the discontinued boxy cabinets for the NeoD's. Should I nab a couple, just in case the DIY infection spreads even more within me (or the NeoDcc conflicts too much with the PSBs), or would the curved boxes be acceptable?

[ThomasW]

I need to clarify....

My "But I'm not convinced this level of 'heroics' would be necessary." statement referred only to making some kind of labyrinth to vent the mid. It didn't mean you shouldn't consider the Statements.

If the wife is ok with a 44" tall cab, the Mini-Statements will get you nice ribbon performance in a smaller package

Re NeoDcc PE cabinets. One of the things that makes building this speaker so complicated is the crossover is like putting 10lbs of gear in a 5lb box. It's literally a Chinese puzzle to get the boards into the box.

To augment the NeoDcc bass output I'd build a single tower or top module and bass bin where the woofer was mounted similar to the one in this pic...

I'm a little scared of the Fi IBs due to be delivered today

She may 86 you from the house after she sees those...

[---k---]

Thomas, he will have plenty of space in the IB to mount the crossovers externally.

Based on your listening, I agree that the NeoDcc is probably the finest speaker he can build, but has he seen the price tag? :W

[kjgarrison]

Thomas, he will have plenty of space in the IB to mount the crossovers externally.

Based on your listening, I agree that the NeoDcc is probably the finest speaker he can build, but has he seen the price tag? :W

In the big space behind the TV is room for an AVR or two.

Price tag? I think I saw something of a BOM in the 450 ish range, not counting cabinet. Is that about right?

[ThomasW]

BOM in Sept of 07 $500ea excluding cabinets. Obviously nothing has decreased in price since that time.

[kjgarrison]

BOM in Sept of 07 $500ea excluding cabinets. Obviously nothing has decreased in price since that time.

Less than half of what a PSB Synchrony Two center costs retail, and about half of what one costs 'on sale'.

Are there certain components that are harder to find in stock? Something I should pick up when I can? Certain drivers or crossover items?

I don't know what Jon meant by "preliminary" with the no-BSC XO design. Does this mean build it like this then make adjustments, or does it mean there will be more to follow before anybody should build it?

Oh, and I still need to know what volume to make the center's box. And whether to try for any particular relationship of width to depth.

[ThomasW]

Right now the tweeters are out of stock at Madsound (August 4th is ETA for new shipment). When they arrive they should be tested to see if there are performance changes from the previous production run. Jed K is on top of this situation since he has a bunch of designs using this driver. My guess is Jed will test and post any measurement changes.

'Preliminary' probably means it's Jon's the first pass playing around with the design. Like many people with OCD, Jon never really completes any speaker. This means his designs are in a continuous state of revision/upgrade. If/when revisions occur is a function of multiple random synapses firing with the corresponding light bulb above head scenario or being hit by a falling object with the corresponding 'ahh-Ha! moment.

All this means waiting for a finalized design from Jon takes on characteristics of 'waiting for godot'.... But not to worry because the NeoDcc is the most researched and developed design Jon's ever made. So any revisions would likely translate to a performance increase in the .001% range.

Jed modeled a 57L ported box with a Fb of ~35Hz box in post #7

[kjgarrison]

Jed modeled a 57L ported box with a Fb of ~35Hz box in post #7

Heh. I never really understood what Jed did. I thought he was going to "model" the whole speaker and was confused that he only modelled the woofers. Now I understand that the low end is based on the woofers, the box, and the port.

Even with that I couldn't duplicate the model he did, because I don't think I have the right parameters for the HiVi D6.8. There are differences between what is shown in the PE listing and on the HiVi website.

I spent some time looking up much of the BOM (non-BSC), and prices have gone up a LOT. I haven't finished it yet, because I have to dust off some physics and figure out how to make some of the components called for. Things like a 33.7mOhm resistor, and a 3.19uF capacitor.

Plus there are some confusing things I noticed. The famous R14 that is wrong on the BOM at 6Ohm and is always quoted as 12Ohms is actually shown as 12.5 on one of the two previous schematics (and on the no-BSC). Also R8 and R9 are shown in some of the diagrams (Midrange XO), but not in others and not in the BOM.

[ThomasW]

The components used in a crossover are manufactured to various tolerances. Most components vary from 5%-10% tolerance.

The computer model only creates absolute values, this means sometimes it spits out values that don't need to be or can't be made.

So using a 12 ohm resistor when the model calls for 12.5 ohms or a 33 mfd when the model says 33.7 is fine.

There is no BOM for your in-wall design. The component values for your build must be taken off the schematic diagram...

[kjgarrison]

I just took the original BOM and compared the original schematic to the no-BSC schematic. I then red inked in the changes as well as the new prices. Several components are unchanged. It just gave me a template to work from as well as an easy to see comparison of costs.

Like I said, though, some items, like R8 and R9 aren't shown in the original BOM, and they are shown in this schematic:

http://audioworx.virtualave.net/ModulaNeoD-HFRC3-Graph.jpg

but not in this one:

http://audioworx.virtualave.net/AD-ModulaNeoD-RC2.jpg

both of which were referred to here:

http://www.htguide.com/forum/showpost.php4?p=405464&postcount=218

It is clear to me that this little segment of the midrange XO circuit is supposed to be there in the no-BSC XO for my center. It is not clear to me which schematic I would use to build (assuming they would require the original XO) the L&R floorstanders .... if & when ...

[ThomasW]

This is going to be a long educational process.....

The sims create resistor values that are the resistance of other components in the circuit. And there are some values created by the sims that are so small they're irrelevant. When you see a value in the schematic that's not in the BOM look at the value. If it's something outlandish, it's ignored. Examples of this are R2-R8-R9 that exist in the original schematic, but aren't seen in the BOM or the block schematic.

FWIW R8 & 9 aren't discussed in post #218, R14 is..

The block schematic is what you use if you're building floor standing speakers.

http://audioworx.virtualave.net/AD-ModulaNeoD-RC2.jpg

The block schematic is also a good reference for wiring the center channel crossover, with the obvious exception of where the component values are changed or things omitted.

[kjgarrison]

Dang! I missed that R2 was an anomaly also!

Thanks, as always, for your reply.

I hope the educational process isn't too painfully long. So far, I have resisted asking why things are done the way they are and instead stuck with the how. I figure that if I want to know the why, I can, and should, go study the subject. Everybody here is so extremely knowledgeable and into this DIY World, that I feel out of place. Kind of like asking the Beatles to help me sing their songs. Maybe I'll decide to learn and understand, and maybe even be able to contribute eventually. I suspect that a non-engineer just has too much basic understanding of electronics to overcome, though.

I'm sure that you must understand that with no frame of reference and no experience, there is no way I am going to decide on my own that something called for in the design is either irrelevant or outlandish. (Especially since there appears both low and high outlandish limits: R2=10mOhm, R9=164Ohm.)

Fortunately there are only 3 such situations so far, and we have covered them. There is possibly a 4th with R1 now at 33.7 mOhm. But with this value being higher than the other ignored low values, I'm not sure. If it is to be ignored, it's too bad, cause I just got finished designing a cluster of resistors, all in parallel, to yield 33.7266 mOhm! (9 x 0.33; 1 x 0.51; 1 x 2.4)

[kjgarrison]

Regarding L-Pad.

I did a little reading on the subject and I see that there are adjustable L-Pads sold by PE, but the one used in the NeoDs (and most builds here?) are fixed.

Jon said the LPad might need some tweaking. This might be a dumb question, but does anybody ever put one of the adjustable LPads in?

And for a dumberer question: Which part of the schematic is the LPad?

[ThomasW]

Sorry I missed your post.

The fixed L-pad consists of R-12 & R13. You can put in an adjustable L-pad for test purposes.

Here's your BOM, the image is fuzzy due to the amount of compression used to get the image down to the 100k file size limit for attachments



If you're using a PC and want to make great screen shots, download a little freeware program called MWSnap 3 It allows a user defined window capture of anything seen on the screen. It also has a jpg compression feature. Also I suggest you sign up for a free image hosting service so you can upload graphics, pics or whatever and put links or the images themselves in your posts.

[kjgarrison]

I actually have a (non-freeware) program called SnagIt. It does a nice job, only I just can't get it to scroll a spreadsheet. Apparently yours can.

With regards to the BOM, there are probably some ill advised combinations of electronics. It's not like I know what I'm doing. So, if anybody sees something that needs to be changed, let me know and I will edit the spreadsheet and in the meantime figure out how to post it on my own.

Is there a program that people here use? I notice all the BOMs seem to have the same look.

[ThomasW]

I have a large monitor so scrolling wasn't necessary.