Project NEXUS... A timbre matched family of Hi-Fi/HT speakers

Hi Matt,
Thanks for checking in on the thread. I think I will do the TMWW versions for L/R and the WTMW centre, and some TMs for the surrounds.


Thanks for sharing your work on these speakers with the forum.


Happy New Year.

 

Hey Matt,


Awesome work! I've been searching and searching for a design to try my hand at and get into the DIY side of home audio and just came across this thread. I'm really interested in building a center channel first and really dig the look of this one.


Can you give some impression of how this center stacks up sound-wise against any of the other more 'traditional' DIY center channel designs around (if you've heard them). (ie: Khancenter, Zaph 3dcc, armadillo cc, statements/finalist cc, etc). I use my home theater for 95% movies so dialog clarity and movie sequence presence is of importance.


Honestly - the price is right for the components on your cc design - I just want to make sure I'm going to end up with a product that will perform well and offer clearer dialog than my current commercial center channels (PSB and Infinity).


Finally - do you have a cut list or diagram of how the Nexus CC is to be put together - especially the separate chamber for the mid and tweeter. As I said, Im a bit of a n00b so I need to be spoon fed (if possible).


Thanks again - I really appreciate your work!
Cheers!

 

Wicked - thanks Erich. I appreciate it.


I think I was able to figure the majority of the design out from the first few pages but Im still not sure if the woofers are sealed in individual compartments or if they are open to each other with the just Mid/Tweet in its own sealed compartment.


If you have the drawing that would be really helpful!


Thanks again!

 

I have not heard all that many other DIY center channel designs so I can't really say how it stacks up against those, sorry.

As for the midrange chamber it is a sealed portion just around the midrange and tweeter. It extends from the top to the bottom of the enclosure but the internal depth of that chamber is only 3" so the area behind it is open to both woofers (think of a large U shaped airspace for the woofers). The internal width of the midrange enclosure is 7", external being 8.5" which comes just to the edge of the woofer cutouts. That midrange chamber works as bracing for the enclosure, the only thing you may need to add is a couple stick style braces from the back of the mid chamber to the enclosures rear panel.

A simple cut list for the center channel box,
Baffle/Back x2: 10" x 26"
Top/Bottom x2: 11" x 26"
Sides x2: 8.5" x 11"
Back of mid chamber: 8.5" x 8.5"
Sides of mid chamber x2: 3" x 8.5"

 

Excellent! Thanks - that clear's it all up. I'm going to give this center channel a shot and see how it all works out. On a side note, I'm surprised that this forum is the only place I've found your plans.


It's just my opinion but I think you should get them posted over on PE and some of the other DIY Speaker forums. I think your plans are desirable to a large group of people and it would be great to see some build threads and listening impressions of the variants.


Thanks again for posting these and for your work!

 

Hey guys - a few quick questions.


I've ordered up all of the components and drivers for the center channel and didn't notice until now a small discrepancy between the crossover network drawing and the parts express order BOM.


The crossover network shows a 0.5ohm resistor being used on the woofer network whereas the BOM shows a 0.47ohm. As I ordered off of the BOM, I now have the 0.47ohm in my hands but I'm not really sure if I should use this or order up a .5ohm instead - or if it really matters at all (I'm new to this so I don't know particularly what this resistor is doing and if that small of a resistor change would be noticeable?!)


Also - I noticed that the woofers are dual VC 8+8. I assume that I'm to parallel the wiring on the voice coils to get each speaker to 4ohm and then connect them in series to get the total load back to 8ohm. Is that correct??

Finally - are these speakers stuffed with anything, foam or fill - or is it not required?

Thanks in advance!

 

No issue with the 0.47 ohm resistor, that was in the BOM because they don't make a 0.5 ohm without spending more for the fancy Dayton one. Difference there is negligible.

I found it is easier to wire the voice coils in series then wire the drivers in parallel but it should not make any difference as I have done it both ways.

I had used recycled denim in the midrange/HF chamber, though you can use poly batting material. Should be moderately filled, enough that the friction keeps it in place but not super squashed in there, should also leave a space for the midrange magnet to fit back in. The woofer chamber should also be filled with poly batting or other acoustic damping material.

 

I saw mention early on of a WTMMW center to go with the MTMWW tower. Is there any benefit of the WTMMW over the WTMW? Would the crossover need modified, or could the drivers just be rearranged something like the attachment.

 

Nice photo editing, that is how it's supposed to look.

The crossover for the tower version might not be a direct drop in for the center channel design. The tower design has some shaping of the response done in the crossover that takes into account the proximity of the woofers to the floor and the offset of those to the mids (listener is further from the woofers on the tower design vs the center channel).

If the crossover was to be used my guess is that there might be a wide lump in the response around 300-500hz where I had boosted the response some in the tower design to give a flatter response at the listener. It is also somewhat unknown what the baffle diffraction effects from the different MF/HF positions will look like or how they will change the response though I doubt they would be too severe. Most issues would likely be fixed by room correction or some manual EQ if used.

The benefits to the dual mid design would be lower distortion and thermal compression in the midrange.

 

After looking for months, I have decided your MTMWW is well worth building. The drivers are sitting on the floor and the cabinets are almost complete. The one thing I didnt quite catch was the exact port length. You stated that you use a "4" precision port with the middle length cut to 5.5", total length is around 12". First off that math does not compute unless the port ends are like 3 1/2 inches each. I dont have that part yet. I was going to use PVC but have decided to order the Precision from PE but the question is if in fact the end are 3 1/2 inch each making the total 12 inches. That puts the port end 2 inches from the front of the cabinet. Is that correct? I thought the rule of thumb was no closer than port diameter.

 

Yes the port flares are a decent length themselves. The proximity to the front of the cabinet is intended, it increases the effective port length allowing the tuning to be lower then it would normally be if the internal port exit was out in the open.

 

Thanks for the quick reply, your the master so I'll just trust you. This is actually my very first speaker build. I have played around with subs in the past but never a nice unit such as this. I did spend about the last 6 months reading every forum on the internet taking notes, making spreadsheets etc.. before deciding on these. My other choice was the Statements and I will probably still build those as well. My original setup for 20 years now was an old pair of Carver AL-III's and a Yamaha M-80 amp but the woofers finally rotted and to be honest I really just haven't had a system since other than a crappy Samsung Soundbar and wireless sub but I am finally getting the home of my dreams after living in a box for the past 6-7 years and it has a Home Theater room So I am going all out on the design and these will either go in there or in my living room. Hadn't decided and I still need to build the other parts of the system (center channel and rears you have shown) as well. So again, thank you very much for all the hard work and effort you all spent on developing such a nice setup.

 

It's the newbie here again. So I got the cabinets finished, wired up all of the drivers and went for the speaker test one at a time with my 50 watt test amp. The first one sounded amazing as I slowly brought up the volume to a normal room level, stuck my ears all over the cabs and the speakers a dozen times listening for anything out of the ordinary and then as increased the volume, the tweeter popped and crackled. I quickly shut it all down, checked everything and slowly brought it back up again.

[SIZE=small] Sounds great until you get past what I would call talking level listening. Loud enough to fill the room but you can still talk over. And there it was again. So I sat aside cab1 and went to cab2 and did the same thing thinking maybe I just got a bad tweeter or something. Nope, cab2 does the exact same thing and upon observing the tweeter cone if you push on up the volume a little more. The cone starts collapsing inward on bass beats when it crackles. I double sealed that MTM chamber because first thought was woofer leakage but both cabs same level? I have never seen anything like that happen so I am asking the masters. Where on earth would you go from here? [/SIZE]

I followed your design on the crossover to the T. As a matter of fact I separated the crossovers as well so the bass is on a board all by it self and the tweeter and mid is on another board and I just mounted them side by side.


I'm only getting a little under 4 ohm on the crossover as a whole does that sound right? I tried to read the other posts above that on what it should be but you were really talking about the other sets and not the MTMWW I think.


I have attached a photo of the crossover which will tell you absolutely squat about the wiring but just wanted you to see that I did spend some time on it trying to make it look nice and I double checked it like 50 times. The copper traces on the board serve no purpose thats why I flipped it upside down, I just more or less just used it as a peg board and wired all the leads together on the back with wire. I did have to use a different combination of resistors to get the .6 ohm on the tweeter. I used a 1.5 and 1.0 in parallel but other than that, I made no other changes but that is also odd that thats where my problem is too.

 

BTW, for any of those that may wander past here in the future. I figured out the problem in the crossovers. Check, double check, triple check and when you think you have it all correct. Check it 5 more times. I wired both of them wrong. It was because some of the areas of the crossovers are wired in reverse polarity on purpose per the design!. PAY CLOSE ATTENTION to that if you should build these. Anyways this was just another speaker build but they are now my primary speakers in my movie room and I may ask to be buried with them.

These are the best sounding speakers I have ever made or heard (within reason of $$$$) Hats of to the designer and builder of these. You really should put them together in a kit or something and offer them for sale. They beat the crap out of anything they sell in stores around me and I live in Dallas Fort Worth so there are many choices.

I am driving these with a Yamaha M65 old school amp and a Yamaha C60 pre-amp. They take as much power as you can stand with ZERO distortion. And the Bass for those that wonder. The bass has more punch than my 15" sub woofers. After running these, I took the subs out. Didn't need them anymore,

Now that I have these in the movie room I am going to try the matching center channel. Will be back soon.

 

Sorry I missed your first post with the crossovers troubles, I forgot to jump over the this forum for a couple weeks but I am glad you got it sorted.

You did a great job on those cabinets, the veneer looks excellent. I am really glad you are enjoying them, they are truly a great value and the set of drivers in this tower format just seem to work so well together.

I do wish it was easier to make a larger flat pack for this tower design as it is one of my top three favorites. I feel bad that mine just sit buried behind other speaker test boxes, I really have to pull them out at some point and exercise them.

 

Hi Matt,
I really love the design of these speakers and would love to make them. I just have a few questions. First of all In you crossover the design mentions Dayton Audio SD215-88A, which of these 3 are the woofers based on
http://www.parts-express.com/dayton-audio-ds215-8-8-designer-series-woofer-speaker--295-430
http://www.parts-express.com/dayton-audio-sd215-88-8-shielded-dvc-subwoofer--295-480
http://www.parts-express.com/dayton-audio-sd215a-88-8-dvc-subwoofer--295-484

2nd. I currently own Klipsch RF-26F speakers which have bronze woofer color so i was wondering if i could just swap out dayton mid and woofer for http://www.parts-express.com/hivi-m6n-6-aluminum-magnesium-midbass--297-441 and http://www.parts-express.com/hivi-m8n-8-aluminum-magnesium-woofer--297-446 and keep the tweeter the same. I know the cabinet size would have to increase by about 2 inches to fit in new midbass speakers but what type of modifications would have to be done to crossover? I am completely new to this and this would be my first build ever. Also is it possible to make it bi-amp design?

 

The woofer used is the last of those three part number 295-484. Unfortunately you can't switch the drivers without a complete redesign of the crossover, as it was designed for the specified drivers and compensates for their specific frequency response and impedance curves. Without having measured the response, relative sensitivity and impedance of those drivers I can't comment on what changes would need to be made to the crossover.

 

Matt,
These seem like they should be very good and inexpensive home theater speakers. It seems kind of weird that I never see them mentioned on other sites. I bought a kit of the mtm's from the AVS classified and they had a nice cnc'd baffle I was told it was from diysoundgroup. Does anyone kit or make the baffle for the center channel?

Steve

 

If those MTMWW towers were on DIYSG I'd buy them in a heartbeat. Not a lot of practical woodworking experience, so the cabinets are what are preventing me from diving in on these.

 

Hi Matt,
I like your design of the WTMW center, I'm thinking of building one along with a pair of matching TMWW sealed tower configuration. I know this thread is quite a few years old now but it's the only 8 ohm TMWW design I can find!
Just a couple of questions about the crossover if you don't mind. What are the crossover points? I tried to reverse engineer using Re specs but not coming up with the right figures. Is that a Zobel on the woofers? No zobel on the mid? First order high pass and 2nd order low pass on mid, is that right?
Thanks,
Wayne

 

Crossover points on that one are 450hz and 2200hz.

Not a Zobel on the woofers, the resistor just damps the 2nd order filter softening the knee slightly.

Correct on the midrange.

I may be revising these designs in the near future, so there may be crossover updates. I recently pulled out one of the MTMWW towers and compared it with the Titan-615LX and the voicing I had on the Nexus was not how I remembered. Plus I have a feeling I can knock a part or two off the TM and MTM designs.

 

Thanks for that. Would you be using the same drivers in the updated design? I'd like to see someone do a build with the newer Dayton RS225P-A drivers, maybe dual 4 ohm's in series. Although as they have high sensitivity, I guess it would be hard to find a midrange to match them.

 

Yeah same drivers, likely just a couple tweaks to the crossovers.

 

2018 update: TM and MTM designs likely getting revamped over the next few days.