"MTG-08" 8" Celestion + DNA-150/DW-774s bookshelf/surround design

Updated to show finished design and details:

This design uses the Celestion TF0818 and the DNA-150/DW-774s, goal was to have a compact bookshelf that had high efficiency, good dynamics, decent extension, smooth articulate sound and do so with a budget of around $100 for drivers and crossover parts per speaker.

Finished enclsoures:



On axis FR:




0-50 degrees horizontal off axis response:




0-20 degrees below axis:




0-30 degrees above:




Finished Crossover, input is on left, woofer out top left, tweeter out top right:


Schematic:





Original build start point:

Finally started this build yesterday.
Using the DNA-150 CD in the DW-774S waveguide, with a Celestion TF0818 for the low end.



Enclosure is approximately 0.6 cu ft internal tuned to 70hz, F3 sould be right about 80hz.
Dimensions:
External 19"h x 9"w x 10.25"d,
Internal 18" x 8" x 9",
Slot port 1.5"h x 7.5"w x 7.5"L,
Drivers flush mounted, the DW-774S was a pain in the @$$ to flush mount, I had to do it all with the router by hand.




Mostly finished with enclosure construction but needs a few more things done before I throw in the drivers and start measuring. Just building the one and going to leave it unfinished until I decide if I want to build another mdf box and paint them black or make nicer enclosures for the pair.

 

Re: DW-774S/DNA150 + Celestion TF0818 design/build

Thanks tux, the waveguide recess was done freehand. It was not easy and I did mess up some, you can see where I put some wood putty on it in my last post.
I feel that this waveguide is the most flimsy of all the denovo wavguides as the plastic is only about 1/8" thick, but installed it is pretty solid.
Here it is with drivers installed:


I plan on getting some mesurements done today and will post those when done.

 

Re: DW-774S/DNA150 + Celestion TF0818 design/build

Here is what I have come up with for the crossover, 1900hz, 3rd on woofer, 2nd on cd:


The only thing that concerns me is the lump at 750hz with dips on each side, most likely a diffaction issue.
The early bass rolloff starting at 130-140hz is room/measurement, I did not want to go outside to do my measurements in 100+ degree heat.



Parts needed (Updated to V1.1 x-over):





With the DNA-150 and the DW-774S the total comes to $102.96 for drivers and crossover per speaker, shipping not included.
You should be able to build a pair for under $250.
I have not built the x-over yet and I don't have a 1.0mH inductor, though it looks like a 0.9mH air core that I have can be substituted in without much trouble.
Once I get the crossover together give it a listen and I like how it sounds i'll draw up a schematic for the crossover and post it here.
I should be able to build the x-over and give a listening impression before the weekend.

 

Re: DW-774S/DNA150 + Celestion TF0818 design/build

I got the crossover built today, and I started to play some music through it. At first it sounded alright but as I started to listen longer something seemed off.
So I fired up my laptop and ran a sweep, the FR looked a little lumpy around the x-over. ???
I pull it apart and run some test leads from the drivers out the port so I can have the crossover outside the enclosure while I work on it.
First thing I do disconnect one of the drivers the tweeter and run a sweep to look at the woofer FR by itself, bingo problem is with the woofer crossover.
After playing around in PCD to get the same response it looks like a problem with the 12uF cap. After about a half hour of playing around with the cap it hits me, I have two caps there 2+10 to make 12uF, I have them wired in series : .

I get it all back together an it sounds much better, I listened to it for for a couple hours and made some minor changes to the crossover until I thought it sounded good, VERY GOOD ;D . These can kick some serious butt, I was only feeding it with a 65 watt amp and WOW it can get loud and very very clean while doing it. I was listening to music 95dB at the listening position and it was just the one speaker, should have no problem reaching reference with these.
After I played with the crossover the only thing changed is the 2.0uf bypass cap changed to 4.0uF and it only adds $0.53 to the total cost.

Here is the crossover schematic:



The 2.2 ohm parallel resistor across the tweeter can be changed to raise lower the tweeter volume to taste, right now it is flat, .1ohm = 1dB. Higher value to raise dB and lower to go down in volume.
The 4uF cap can also be changed to alter the HF boost that counteracts the falling response of the constant directivity horn. Lower value for less boost, higher value for more, I would not reccomend going above a 6uF cap there because impeadance starts to dip below 4 ohms at that point.


Measured FR, indoors so still some bass cancellation happening, also expect a little more bass with the 18awg solid core, I am using a higher DCR 20awg air core, f3 should come in at ~80hz:




horizontal 0-50 degrees off axis, some narrowing at 2.5k but not bad:

 

Re: DW-774S/DNA150 + Celestion TF0818 design/build

Thanks guys,

I can get the 2.83v/1m sensitivity but don't know how do any distortion measurements, or if I even can with my setup. If you can give a quick how to, or link to one that would be great and I would be sure to post those as well.

Edit:
Just did a quick 2.83v/1m sensitivity test, set the generator in REW to Speaker Cal and turned up the volume until I read ~2.83v on the multimeter, my spl meter read right around 91.5dB from 1m away.

 

Re: DW-774S/DNA150 + Celestion TF0818 design/build

Well you just made me look into how to gate my measuremets in rew it should help alot, thanks max.
The response above has a crapload of noise from reflections in it and I had to apply alot of smoothing (1/6 octave) to it.

Here is what the response looked like unsmoothed:




And now my new gated response unsmoothed, thats much better at filtering out all the noise then just smoothing it away:




And gated with a touch of smoothing:



And finally a short video, (this was one of the first songs I played though it and was blown away):
http://www.youtube.com/watch?v=jkDki019l4U

 

Re: DW-774S/DNA150 + Celestion TF0818 design/build

The DNA-150 is great, it sounds excellent and really held together well when I cranked the volume.

Go right ahead and make some flatpacks for it. It would be nice to get the waveguide flush mounted as it looks better then surface mounting, however surface mounting does not cause issues with the crossover the foward lobe is just moved down a couple degrees without any change to on axis response.

I am not going to start any more builds until I can sell a few of my older ones, I am running out of room to put speakers ;D I have a shelf with 5 pairs just sitting there. Although if one of these new waveguides interests me enough

 

Re: DW-774S/DNA150 + Celestion TF0818 design/build

I haven't gotten any vertical off axis measurements yet, I tried some inside but they were no good I'll need try again.

PCD predicts a -6dB in crossover region at 18° below axis and 15° above.

 

Re: DW-774S/DNA150 + Celestion TF0818 design/build

Ha, I never thought of doing it like that
Should be able to get some up today.

 

Re: DW-774S/DNA150 + Celestion TF0818 design/build

A 3" would work 4.5" long, but air velocity is a little high, two 2.5" ports 7" long would be better, or a 4" port 8.5" long but then space becomes an issue. It's hard to fit any round port in there while keeping air velocity low enough.

Here are the vertical off axis measurements, the lobe points up a little more then expected, 0-20 below:


0-30 above:

 

Re: DW-774S/DNA150 + Celestion TF0818 design/build

Ok, looking forward to someone else's impression.

 

Re: DW-774S/DNA150 + Celestion TF0818 design/build

I was doing some more listening to this one, and think some slight changes can be made to the crossover, to me the upper mids/highs are a little bright. To fix this the 2.5mH inductor can be changed to 3.0mH adds $0.46 to cost, and the 2.2ohm parallel resistor on the tweeter should then be changed to 1.8ohms. However turning the bass knob up on my receiver also seems to do the trick .

 

Re: DW-774S/DNA150 + Celestion TF0818 design/build

Those part numbers would be 266-558 for the 3.0mH inductor and 016-1.8 for the 1.8ohm resistor. The difference in weight should only be +0.04 lbs. These should only result in a very slight tonal change in the sound. I need to test them before you go ordering the parts, it may need only the resistor change.