electro voice 12TRXC

[hunsoop]

Hello there,

I just purchased a pair of EV 12TRXC 8ohms at ebay, and would like to build the enclosure. I studied about this speaker and find out that “it is integrated 3 way speaker”- http://www.electrovoice.com/downloadfile.php?i=970305 but some other documentation says it is two way full range speaker-http://hf-antenna.com/Flotsam/EV/How_to-build_a-EV-spkr_system.pdf

1. Can anyone tell me which definition is right?

Also there are two inputs in this unit – looks like one for tweeter the other for woofer,, but I am not sure how to hook it up to utilize both inputs.

2. Can anyone upload a diagram?
3. Do I need crossover(s) for woofer or/and tweeter? If yes, what would you recommend for? –

If this unit is two way full range speaker-

4. Do I need midrange horn( 8HD with 1824M driver) that is recommended by EV documentation.

Enclosure -I am planning to build 11- 14 cubic feet

5. How the outcomes will be different when the enclosure is 11 and 14 cubic feet?

I really appreciate if anyone can help! Thanks,

 

[GM]

Greets!

Neither is technically correct, though the 3-way one is close enough since it’s an electrical LF, HF 2-way with a mechanical whizzer to span the gap between the two.

Really? I only recall one set of exposed power terminals.

Don’t have a diagram.

Yes, it should have a [basic] XO built in to protect the tweeter horn and with a wired up HF attenuator.

Yes, for best overall performance you’ll need a mid horn, XO.

Well, the bigger the cab, the lower it ideally needs to be tuned just as the EV chart suggests, so you’re trading an increasing amount of LF efficiency for an increasing LF extension with increasing net cab volume [Vb], lower tuning [Fb].

In short, all else equal, the bass rolls off at a higher frequency as the cab gets bigger, tuned lower. The lower tuned cabs tend to blend in with the room’s gain better, especially if corner loaded, but if they will be well away from any walls, corners, then a smaller cab tuned higher is usually preferred.

GM

 

[hunsoop]

Thank you Gm,

I found its diagram at the internet-already ordered parts for crossover.

http://mypicsonline.net/archive/arc...iscellaneous Electronics/EDS/X8 & X36 EDS.pdf

And, I decided to go ahead with 12 cubic feet.

LF 3db down point-31hz
SPL MF-111dbsb
SPL LF-108db

Has anyone tried this speaker? people say that it is really good for tube amp and i tried it without cab, it really sounds more alive than the one i have- Psb T55.

 

[GM]

You're welcome! FWIW, 14 ft^3 looks worth the extra 2 ft^3 in a sim.

Regardless, what layout do you plan to use, basic rectangular box, MLTL, or ?

GM

 

[hunsoop]

yes, just basic rectangular with a vent (width 24X depth 24 X height 38)

I will use made in russian 6uf cap at ebay and air core inductor Jantzen 0.37mH 18 AWG Air Core Inductor 255-222 for crossover. the diagram for crossover was 16ohms so i had to change to 8 ohms.

Anything I should concern? please let me know. thank you

 

[GM]

You’re welcome!

Don’t know about ‘concern’, but since you’re already at a 38” height, going to a taller MLTL normally yields a bit better overall performance due to its TL ¼ WL action damping the vent for better driver control around/at Fb plus it gets the tweeter up to average seated ear height.

I’ve never owned one, but have helped others with earlier versions, with the best sounding being with a SS amp powering the woofer and a SET for the HF in a ~20 ft^3 net MLTL.

GM

 

[freddi]

- - wonder if Qts >0.7 ? - that designation I think says its the 16ohm version of 12TRXB -- not sure how adding an 8HD would sound overall.

 

[GM]

Factory spec is 0.665 Qts. Not sure what your concern is, I mean adding a mid horn and three way XO is desirable when the HF horn has such a high XO point.

GM

 

[hunsoop]

- - wonder if Qts >0.7 ? - that designation I think says its the 16ohm version of 12TRXB -- not sure how adding an 8HD would sound overall.

yeah- Qts is 0.67 and mine is 12TRXC 8ohms (SP 12C + a T35 horn tweeter), slightly different from 12TRXB. And Ev documentation recommended using it with 1824M, so i would like to try.

 

[hunsoop]

You’re welcome!

Don’t know about ‘concern’, but since you’re already at a 38” height, going to a taller MLTL normally yields a bit better overall performance due to its TL ¼ WL action damping the vent for better driver control around/at Fb plus it gets the tweeter up to average seated ear height.

I’ve never owned one, but have helped others with earlier versions, with the best sounding being with a SS amp powering the woofer and a SET for the HF in a ~20 ft^3 net MLTL.

GM

GM

i thought about MLTL, but it looks like it requires more input on cab and basic rectangle type is pretty simple for me to try by myself. i have very limited capabilities-tool, skills etc..... Do you have any sites that explain step by step on how to build MLTL?

thank you,

 

[phivates]

You can do much better than that old EV midrange horn/driver. Either a high output 6.5" cone or a modern wave guide will result in something listenable, not just loud. I prefer the cone driver since it facilitates a lower crossover. Can of worms?
Then we'd have to move this to another forum, on second thought.

 

[GM]

Been a long time, but I don't remember it sounding bad over the limited BW required for the TRXB, though I agree that modern cone drivers and horns are in some ways far superior to what was available back then.

GM

 

[GM]

GM

i thought about MLTL, but it looks like it requires more input on cab and basic rectangle type is pretty simple for me to try by myself. i have very limited capabilities-tool, skills etc..... Do you have any sites that explain step by step on how to build MLTL?

thank you,

You’re welcome!

If you’re interested enough, MJK’s site has all you’ll ever need to know and much more: Quarter Wavelength Loudspeaker Design

Consequently, there’s many folks here set up to quickly design them, so all we need to know WRT your cabs is what, if any height restriction there is and average seated ear height.

WRT construction, a basic MLTL is nothing more than a tall reflex, so your rectangular cab would be taller and for the same ‘footprint’ [CSA] have a larger net Vb, so depending on the chosen alignment it could take up less floor space.

For example, a 38” driver/floor ear height is common, which using your ~12.667 ft^3 gross internal volume [Vb], which with a 60” i.d. height = ~364.81”^2 i.d. CSA Vs your cab’s 576”^2 i.d..

Since ‘bigger is better’ [BIB] typically rules, especially with high Qts drivers, maintaining the 576”^2 CSA x 60” = 20 ft^3 Vb.

If you have the floor space, then I recommend making them rectangular in a golden or acoustic ratio due to the large CSA as it will reduce the amount of efficiency robbing internal damping required.

Anyway, the 1st sim is the 20 ft^3 example based on a 38” seated ear height, 0.75” [19 mm] material thickness, all dims i.d. and approximate:

H = 60”
W X D [CSA] = 576”^2 [suggest a golden ratio 30.5” x 18.875”]
Vent = 9” dia. [or 3” x 21.25” slot] x 0.75” baffle thickness
driver up 37.25”
Vent up 6.75”

The 2nd sim is the ~12.667 ft^3 reduced footprint version, which of course has much less low bass, though may be sufficient in room:

H = 60”
W X D [CSA] = 364.81”^2 [suggest a golden ratio 24.31” x 15”]
Vent = 6” dia. [or 1.375” x 20.56” slot] x 0.75” baffle thickness
driver up 37.25”
Vent up 6.75”

Damp to ‘taste’. FWIW, I prefer 1” acoustic fiberglass insulation on the top, one side and back down to 40” and add more down further and even its floor if need be to quell if there’s any in-room bass ‘boom’.

There’s a number of suggested bracing schemes in these designs: Frugal-phile DIY Audio Community Site

So, either work for you or do you need a different driver height and/or a shorter cab or can you tolerate an even taller one if the ear height needs to be higher?

GM

 

[hunsoop]

GM

Thank you for your help. I will need to study more about enclosures on the web sites you provided me. Once i make a decision on enclosure dimensions, i will let you know. But height 60"- I wonder that i can handle that high!

thank you so much for all your input!!!

 

[hunsoop]

GM- one more q

Do i need to follow golden ratio to get the best result? or it is just a reference.....? i know that this may be very a silly question.....

 

[phivates]

It is not a silly question. Every solution has more than one rule.

 

[GM]

But height 60"- I wonder that i can handle that high!

thank you so much for all your input!!!

You're welcome! FWIW, mine are ~62" x 30" x 24" and many who have cruised through here left with 72"-84" high pipe horns, so not sure what you mean about not being able to handle it if there's physically no restriction.

GM

 

[GM]

GM- one more q

Do i need to follow golden ratio to get the best result? or it is just a reference.....? i know that this may be very a silly question.....

No, it just theoretically reduces the minimum amount of internal damping required same as when designing a room to have acceptable acoustics.

GM

 

[hunsoop]

GM!

finally made a decision -

vb=15
fb=27hz
number of vents- TWO
vent diameter - 4inch
vent length -3.25inch

The reason I will have TWO vents enclosure is because I can get 4 inch diameter PVC pipe anywhere (home depot or lowes). Otherwise I will need to have an special order.

Here are my qs-
1. Do i have any problems if i go with two vented enclosure?
2. If there is nothing to concern with two vented enclosure- Is there any specific rules/locations for the ports?

Also, I bought a pair of 1824M and university sound cobreflex iii for midrange. Any experience about university sound cobreflex iii?

Thank you,

 

[GM]

Greets!

1] Yes, due to the tall cab’s ¼ WL pipe action damping the vent, it will take [3] 4” dia. x 0.75” [baffle thickness] vents for ~15 ft^3/27 Hz, so no need for tubes.

2] For high aspect ratio cabs it’s a good plan to locate the vent down ~80-86% of its inside [i.d.] length

OK, final design:

H = 60”
W X D [CSA] = 432”^2 [suggest a golden ratio 26.43” x 16.375”]
Vent = [3] 4” dia. [or 1.875” x 20.125” slot] x 0.75” baffle thickness
driver up 37.25”
Vent up 6.75”

Damp to ‘taste’. FWIW, I prefer 1” acoustic fiberglass insulation on the top, one side and back down to 40” and add more down further and even its floor if need be to quell if there’s any in-room bass ‘boom’.

There’s a number of suggested bracing schemes in these designs: Frugal-phile DIY Audio Community Site

Messed with the original Cobreflex some back in the ‘60s and at this point in time all I remember is that the Altec 511 was clearly superior for a 500 Hz XO point HIFI apps, so you may need to up it to 800 Hz.

You’re welcome! Hope you come back and post pictures along with a mini revue.

GM