hello :)

[Cia]

hello guys hope you are all well I'm Chris

wish you all a happy new year!

So.. I'm a noob in sound systems trying to learn from forums and groups etc, I've already have a decent sound system which are a mix of commercial brands and also some diy speakers, I have good but not professional woodworking skills and also a decent workshop.(building speakers is addictive hahah)

I will begin with something simple which I feel I need to improve my system some tops that can be stack over each other forming a tower/line array without major comb filtering issues. So i decided to try the omni top 12.

I would like to ask you please just to clear some thoughts.. the omni top 12(not the J array version) is square so cant be stack like the J array...but if I add a spacer at the front 1-2inch to get the same effect as a tapered box, I will encounter any comp filtering issues due to I'm changing the distance between the piezo s?

another one ...I already have some subs and I don't think need more at the moment. but I have a pair of old drivers which I would like to make an enclosure for them...kindly I would like to ask you if they will fit decently in the tuba 30 or the titan 39? the driver are rcf 12lp-400.

parameters:
RCF 12lp-400
sens 94db
fs 34hz
qms 7
qes 0.25
qts 0.26
mms 0.5kg
cms 0.00045m/N
D 0.241m
sd 0.0456mq
vas 0.13mc
re 6ohm
bl 15.5tx m
efficiency 1.9%
xmax 6mm
voice coil D 75mm

thank you guys.

Kind regards

[Seth]

Hi Chris, I'm Seth. Welcome

If you would, please update your profile and let us know what part of the planet you currently call home.

Also, tell us a little about how you plan to use your system. Primarily indoors or out? Live music or recorded? Are you a musician? A DJ?

The RCF L12P-400 spec are suitable for a T39, but the 130L Vas is just over the maximum 125L spec for a T45.

[Cia]

thank you for your reply.

I wish to use omni tops coupled with some subs for live small concerts (school concerts mainly) both indoors and outdoors.
for indoors i usually use reflex subs because(simple) I had some headaches in the past using horns due too that I'm not a pro and it was very time consuming trying different spots to get them sound as desired.

never tried to measure etc.. next step is to invest in a measuring mic and a sound card.

the v coupling method sounds very interesting i wish to try it some day!

sorry but by mistake I wrote tuba 45 but I was referring for the tuba 30(anyway they look simliar)..so the best option would be the t39?

kindly, I would like to ask you please ,regarding sensitivity vs maximum spl, would i get better max spl with a horn? or just sensitivity? cause Im reading in many posts that the power handling of the driver decreases in a horn.

regards

[Cia]

btw nice to meet you !

[Bruce Weldy]

I would like to ask you please just to clear some thoughts.. the omni top 12(not the J array version) is square so cant be stack like the J array...but if I add a spacer at the front 1-2inch to get the same effect as a tapered box,

Really not necessary. If you are just stacking 2 or 3 per side, there is plenty of vertical dispersion to make sure everyone hears. I've been running 2 per side for years and years from small rooms to large outside shows and never once wish that I had tried to get the bottom one angled down.

[Cia]

Thank you Bruce. Piezos or compression driver for the best vertical depression?

[Cia]

I'm testing some piezos that i bought from eBay..but by mistake I choose the 1025 style a different design they are slightly larger than the recommend from the plans.

IMG_20240118_091655.jpg

I was amazed how these crappy plastic things sound!!!

[Bruce Weldy]

Thank you Bruce. Piezos or compression driver for the best vertical depression?

I don't think it makes any difference on the vertical. The melded array has a wider horizontal dispersion than the compression driver, but not by a lot. I have both. I put the melded on the bottom for the wider dispersion and the CD on top.

However, if I was doing it all over again, I'd stick with the CD all the way. I'm willing to give up the little bit of extra horizontal dispersion for the much better sounding CD. Now, the caveat is that this only applies if you do the 1.2k crossover. The lower crossover point just sound way smoother - especially on vocals.

If you are just DJing, then I don't think it matters as much - build whichever you wish. But, for live sound, the CD all the way......again, the 1.2k crossover version, not the 2k.

[Bill Fitzmaurice]

Thank you Bruce. Piezos or compression driver for the best vertical depression?

I believe you mean vertical dispersion? You don't want the best/widest vertical dispersion. That puts sound in the heavens or on the ground, where you don't want it. The point of a line source is it has maximum dispersion on the horizontal, where you want it, not on the vertical, where you don't. The 1025 piezo works, but being larger you can't use as many of them.

[Bruce Weldy]

Thank you Bruce. Piezos or compression driver for the best vertical depression?

I believe you mean vertical dispersion?

Wow, I read right past that...guess my brain just filled in the word I was expecting to see. But, too much vertical dispersion can create some musical depression if you can't get it to sound right.

[Cia]

Yes sorry dispersion . Haha ...

So..In a line source when multiple boxes are stuck over each other high frequency's need to be spread horizontal not vertical due they might interfere with each other. I'm right?

Regarding the piezos 1025 i think that can be trimmed to around 2 inches hight so I might fit 6 in an omnitop12, but not sure if I choose piezos or CD I wil build the CD horn and listen to side by side and then i decide. (But at the moment i m very busy ) i have to postpone a bit for a week or 2.

Thank you I really appreciate

[Bruce Weldy]

Yes sorry dispersion . Haha ...

So..In a line source when multiple boxes are stuck over each other high frequency's need to be spread horizontal not vertical due they might interfere with each other. I'm right?

The horn on the cabinet determines the horizontal dispersion. It's not an interference issue at all, it's as Bill said - there's no need to be sending high frequencies off the floor and the ceiling. The more speakers you stack on the same plane, the narrower the dispersion. That's why stacking the tops instead of splaying them gives you wider horizontal dispersion and no comb-filtering. It also tightens up the vertical dispersion to keep the sound focused toward the audience and not bouncing off the floor and ceiling.

[Tom Smit]

Cia, welcome to the forum!

One does not want the high frequencies bouncing off the ceiling or the floor because those reflections mess with the direct sound, and makes it sound bad.

[Cia]

Thank you guys