Nothing special it’s good, but I’ve never heard a lot of differences between compression drivers, as soon as they have similar specs, angles and then good interaction with the horn.
It was easy to eq and seem flawless, here’s a page on them.
Good to know.
Cream woofers would look cool yes. I certainly would like a lower FS
Beautiful start! What’s the size, around 80x40x60?
Where are you struggling? to align everything for glueing?
It sure was an issue for me, that’s why I glued the box first (sides and back) and then added bracing after to make sure to compensate for little offsets here and there. Then the baffle glued over at the end after careful sanding to get everything flat for it.
Big panels are more tolerant I think.
The 1st one isn’t perfeclty square, one diagonale is 5mm longer, 2nd one is ok.
I studied bracing for a while, found @planet10 posts very useful (about bracing in longer length).
For the smaller boxes I was more into over bracing.
Construction was a bit different as the Eket panels are made of particles with honeycomb cardboard in the center.
Very rigid for their weight but not dampening enough, so I used a second skin inside with mdf, + bracing a la Troels.
1st version used limited bracing:
2nd one had heavier braces + cross section holding the woofer tight (very long to adjust) with baffle screwed on.
On this one I also tried using sand (like on an older sub project), meaning I "emptied" the center of each eket panels, removed the honeycomb, Glued the box with mdf inner skin, and filled them with sands, you can see here the little panel used to close each sides, the square near the brace on the right. Box was of course very heavy and certainly dead on the knock test.
Well at the end I ddin't hear any differences (didn't measure impedances).
A lot of work (and fun) but for nothing.
That’s why with the big boxes I started much lighter.
Plus I also realised how much weight the braces would add, I wanted to be able to hold them alone at the end!.
No need for 2nd inner skin here as the panels I used are full particles, no honeycomb, maybe just a little too thin (17mm) but they’re only for sides so have the shortest dimensions. I also solidified all corners to compensate the simple and weak butt joints.
And used multiple kind of glue depending of the material, cyano, PVA and PU wood glue and sika at the end to make sure everything is tight.
I certainly don't have JBL's build techniques but just wanted to try a better ratio of efficacity.
Found the sweeps about the filling,
Empty:
4 cushions:
6 cushions:
8 cushions:
Qts down about 2 points and 6 herts on the Fc.
And the wiggles I could see are above the bandpass.
So like I said I finally removed everything, it sounded a bit constrained.
I will restart soon, but so far the room resonances are really the issue, not the box’.
Empty:
4 cushions:
6 cushions:
8 cushions:
Qts down about 2 points and 6 herts on the Fc.
And the wiggles I could see are above the bandpass.
So like I said I finally removed everything, it sounded a bit constrained.
I will restart soon, but so far the room resonances are really the issue, not the box’.
Pretty close indeed; the baffle is 72x58 so with sides it’s ~76x62 and yes 40 deep (30 inside, double baffles).
The struggle is glue for sure. The cutouts from the wood shop wasn’t as accurate as with previous projects so I have to sand a lot to make things fit and I’m unsure only glue will work this time. And the angles screws up as you describe.
The two largest sides remains but I think I’ll get some listworks into there before continuing with sanding. I’m a bit tired of it to be honest I might have overstepped this time.
But seeing your project progress gives me motivation.
I never had the chance to play with DATS, but from what I can see, there are some wiggles at impedance and improvement after 4 pillows.
Theoretical resonance formula:
34000/100/2 = ~170 Hz
Yes for sure you can use LT to have less bass ie lower Qtc.
“For Vituix I have everything to try, started to plan something in the garden for the smaller version but need to re-evaluate for these heavy boxes.
Or maybe just placed still on a tall wall and moving the mic is enough.”
Learning curve is steep, but I think it is for sure worth it.
No, it doesn’t work good to eyeball measurements. Only right way is to build turntable so you can measure angles properly. Turntable for your beautiful speakers will be HUGE….
Of course room matters a lot, but I do think some of your issues with bass is also from not having good enough measurements. Splicing farfield and nearfield is I think the best way.
For finish on the front of you epic speakers, how about making a grill? Or if you don’t like that, how about
Linoleum in a nice color?
Or maybe just placed still on a tall wall and moving the mic is enough.”
Learning curve is steep, but I think it is for sure worth it.
No, it doesn’t work good to eyeball measurements. Only right way is to build turntable so you can measure angles properly. Turntable for your beautiful speakers will be HUGE….
Of course room matters a lot, but I do think some of your issues with bass is also from not having good enough measurements. Splicing farfield and nearfield is I think the best way.
For finish on the front of you epic speakers, how about making a grill? Or if you don’t like that, how about
Linoleum in a nice color?
Nice work gents.
I think these systems will give you both years of enjoyment.
Off topic but l was considering using the Roy Allison dual woofer design but it looks weird.
I much prefer this classic retro look of these baffles even if it isn’t acoustically perfect in a room. We tend to listen with our eyes after all…. Lol 😜
I think these systems will give you both years of enjoyment.
Off topic but l was considering using the Roy Allison dual woofer design but it looks weird.
I much prefer this classic retro look of these baffles even if it isn’t acoustically perfect in a room. We tend to listen with our eyes after all…. Lol 😜
And sanding mdf is clearly not a pleasure…
I usually build with mdf for the low cost, but this time using plywood and lumber made such a difference! No more itching or funny breathing at the end of the day.
Is it all butt joints? If you're not sure of the angles maybe you can use PU glue? It helped filling the irregularities, but it needed tight clamping as its expansion is strong.
The horn will be placed on top in free air, or inside?
95/96cm inside so around 177-178hz in theory for the horizontal.
And 34000/66ish/2 so around 250hz for the vertical one.
The midrange box and braces might extend their pathlength a bit and that could explain the wiggles around 150hz and 220hz.
The 220Hz one is clearly visible in nearfield measurement, the 150hz one is less.
You convinced me maybe 2-4 cushions are needed I'll retest!
So about the LT, it is used a lot nowadays but still not the majority of the time I feel.
Is only due to the driver and amp requirement? (high Xmax & power needed)
I mean, if well done we should not expect any difference in the quality of the sound?
Ok, I need another project to think about, was thinking about a DBA for the winter…
But maybe I should focus first on Vituix.
Turntable then, boxes are not so heavy, maybe 80kg as I can still lift them but their size makes it unpractical, and unsafe.
I'll check other threads about turntables.
Good catch, I do like grills, especially jbl foamy style, 70s orange or apple green for example.
4350 split style would not work as the mid is not high enough to create a fake separation, and one big flat surface might be odd.
I don't know yet how to finish them but it is an option, it will depend of the finish and color on the horn.
Then either just paint the baffle, or build a frame with tissue.
I have a bunch of tissue of different colors from when I wanted to build basstraps in besta boxes (you can see a raw one behind the left speaker above).
Also the raw plywood look is not bad once in place, it matches the stuff I have around.
Same here, it looks much better to my eyes with the protruding side panels (is there a word for that?).
I knew it would not be best for diffractions, but I imagine it's partially compensated by the horn return/round over, with its lip right over the panel.
+ the fact that it's cut above its minimal crossover point now at 1400Hz instead of 1200Hz, so I imagine even less soundwaves going this path.
Horn total height is 23cm, 1400hz wavelength 24.5cm.
But there's probably big diffraction there when the sound-wave hits the front baffle.
I guess I'll know better with Vituix, as I could try different setup.
I just contacted Nicolas. I'd like to use the Kartesian Cmp45_vTLHP which I've already bought and should be good from 1600Hz.
I'm about to create powerful LCR speakers for my home cinema together with Hypex FA503 and I'm slowly thinking of routines with the woodworking with a lot of standardisation to get repetitive and precise cuts. I have multiple Festool tools which I want to use to the highest level possible. See one of my builds https://i.ibb.co/9gwSQmG/Bracing-Nero.jpg
I must say Im no export, just happy amateur. But I will say LT is really nice if used properly. Commercially I would bet it is used a lot. BUT: With the little change many DSP in OEM have dynamic bass boost/limiter.
Issue with huge box is more material and I think requires even more bracing compared to smaller.
I would say if done correctly you could have very good bass. Way better than oldscool textbook tuning.
Price to pay is more distortion, you need more watts and SPL may be limited.
Unfortunately your drivers is not in VituixCAD, but data can be input manually.
For example here we have 2*Faital 15PR400 in parallel in 107 Liters. I have no experience with them in practice.
Qtc 0.707. Fb 78 Hz. If we add LT to Qtc 0.707 and fo to 40 hz we get this:
If we lower level to 95 dB, which is pretty loud! You have more than 15 dB headroom at 30 hz and it requires less than 5 watt! But of course requires much more if signal has huge peak of low bass.
Depends on a few things: how the 2x12 cab perform bass and mid, I have some ideas: a free air large horn on top, a smaller horn inside, and possibly a mid, or use this as a sub where I put some monitors on top; an 8” tannoy coax I have from long ago possibly open baffle, or a 12” celestion coax I have built few years ago. Or something else. All depends on how it preforms. “It” being the 2x12. I’ll make a thread about it some day and stop derail this thread. Sorry for that.
Note @Joseph Crowe has a kit 2154 where the 15OB350 works in 90L BR Box 🙂
I am not fan of BR box but well used you can do miracle in the bass, lowering distortion and have a high definition without loosing transient.
Curious to hear back what he says about the Cmp.
At first I had in mind to use the Cmp65 but followed his feedback.
That kind of bracing should close the question for sure!
Thx Rockytheman, the sims I’ve done showed similar potential with the 15OB.
Higher Q and Xmax but lower FS, and finally picked them for the price.
I boosted them a bit more around 30Hz than planned since in real life I listen lower than on the sims.
I also realised I’ve made a mistake with previous voltage measurements, miscalculation, so at the end they push +3db at peaks so double power for max output.
That’s still low but the Xmax is coming closer, in theory.
And since with recent days I kept increasing the spl... I need to get a precise measurement of SPL at MLP.
I had the habit to correlate it with the minidsp volume but that was an old reference that needs to be updated for normal/loud/super loud levels.
I also struggle to adjust the house target to this new system.
With the dipole I was more into a B&K curve, with slightly decreasing spl at the very low end.
Now I’m trying to adjust it to find the right level, strong enough but not too much so the room takes over.
Yep his test in sealed was part of my decision.
Finally I have enough output down low so I won't try BR, now it’s more about refining it.
I bet those SB 15” is great! I forgot to mention I think they Will sim even better than the Faitals.
It is indeed difficult to get it right with bass. I like to cross check level with headphone or reference speaker.
It is indeed difficult to get it right with bass. I like to cross check level with headphone or reference speaker.
Agree that Raw plywood look quite nice.
I searched a Long time to find the right type and color. I ended with this Company that I think makes the best fabric. Quality dont even compare to the cheaper stuff around. Very smart system they provide with Velcro so you Can realign fabric (cost a bit more thet Velcro, but works like nothing Else)
https://www.akustikstoff.com/en/Ord...loth-Sample-Swatches-All-45-Colours::758.html
I think it is ‘french’ blue I have and I believe it is pretty close to original JBL blue.
I have sample of all colors, so Can post some if you like.
I searched a Long time to find the right type and color. I ended with this Company that I think makes the best fabric. Quality dont even compare to the cheaper stuff around. Very smart system they provide with Velcro so you Can realign fabric (cost a bit more thet Velcro, but works like nothing Else)
https://www.akustikstoff.com/en/Ord...loth-Sample-Swatches-All-45-Colours::758.html
I think it is ‘french’ blue I have and I believe it is pretty close to original JBL blue.
I have sample of all colors, so Can post some if you like.
Yes sure great potential, I must say I’m still somewhat influenced by the idea that a driver in itself can bring some magic, but I try to counter-prove myself.
And the lower budget than before helps here 😀
Or I’ll only change/upgrade once I have done everything right like: reconfiguring the room.
Relocating the wall of diffusors, putting the boxes to the front flat or toed-in, moving the sofa closer and then play with basstraps or multi subs/dba.