Beta 12LTA in a 3cf box - port size

[GM]

I was on a pedal powered cycle GM - these days I only go out on a motorbike when it's really quiet and Never near traffic.
Hardest bit was not being able to surf... next year maybe.

Ah! All the more reason to wear protective gear if your locale is as dangerous as the metro Atlanta area. Serious injuries, muggings, death are an all too common occurrence if you don't ride in a large group even if on a dedicated bike trail, so I stay in my local housing neighborhoods and only cross one major two lane when alone or with just one other.

Please do wait till fully healed as I've learned the hard way the consequences of a re-injury can last a lifetime.

GM

 

[GM]

LOL, funny how we are building speakers and we can't even hear all of the frequencies.

Well, we can still perceive some of them through feel, at least at higher SPLs. When I test myself I can barely hear 12 kHz, but I can sure enjoy much higher without nearly as much distraction that vinyl noise, tape 'hiss' caused in my youth.

GM

 

[freddi]

here's what my Kalsonator 12 does in a messy room with 12LTA - I'll add a short K-tube tweeter but probably will use a 2nd order highpass on the Peavey RX14 as 1uF interacting with its Z peaks allow it to still have substantial output to 1K6

12LTA on sine is pretty clean down to 32Hz -

one natural helper tweeter for this application would be Selenium's discontinued but great ST324 slot tweeter

Karlsonator 12 works nice with 12LTA, Nirvana Super10 and with Beta10cx, went down to 37Hz before cutoff in another room

 

[GM]

Hey Freddyi,

You show all these near-field ground-plane/whatever measurements [thanks!], but what matters is how they sound in room at seated ear height, so considering the K's uniqueness, seems like a ~38" [average seated ear height] ground plane offset at different common listening distances would be more informative overall WRT its mids/HF response.

GM

 

[freddi]

Karlsonator 12 with 12LTA (with or course a good helper tweeter) would sound "fine" at seated height. There's no damping in the rear section, back panel or back chamber top. Its a "warm" balance - different than 12LTA in a Karlson "K12" as the larger Karlsonator has around a half octave more extension than the little K. K12 sounded good with my Yamaha helper tweeters ($$$$) a CTS KN1005 sounded good too and much less expensive.

Karlson's originals are impressive for the punch they can provide. PYM1298 with "95oz" magnet, and topped with a K-tube has a LOT of "GRAB" - 12LTA is laid back and compressed sounding in comparison. I tend to like strong motors and low moving mass. Carl N. said one version of the University C15W had 35Hz fs and only 40 grams MMS. My Peavey 15 with 4" coil has 53 grams mms and that's pretty low.

My opinion of large fullrange with high crossed helper tweeter is that the power response in a section of the overall bandwidth is weaker than a 2-way with 12" and lower crossover compression driver.

12LTA is good for the money - I wish it had more motor - assuming that could be balanced with improvements overall. I paid $39.95 last time for 12LTA - the Karlsonator/12LTA is probably the best I can get out of for low end but it will get beat by a Klipschorn - even a K400 horn that horn-aficionado seem to hate, has more midrange "presence" across a big room than a big paper cone with a whizzer attachment.

Some years back I ran 12LTA open baffle with a helper tweeter and crummy 21" woofer. There was some vertical spatial incongruity with harmonics

I'll try to record the Karlsonator/12LTA combo but don't have any good AA batteries - will have to order a few.

here's where Karlsonator 12 is tuned - these traces probably were made with a half ohm's worth of wire between two rooms. Since I now have the K-nator in the same room as my pc, I will be able to knock off that half or so ohm.

 

[freddi]

I think the Karlsonator with 12LTA sounds pretty good with a decent helper tweeter - tweeter tonight = Selenium slot loaded ST320 1.1uF series/0.2mH shunt - ~5.3 ohm series before the cap as attenuation (still maybe a tiny bit hot)

it doesn't have the visceral grab of my K18 - but for music , adequate -- not bad at all. As I've said before, success with 12LTA will depend upon the helper tweeter and its network.

When I get batteries, I'll record it.

 

[howardg]

Open baffle 12LTA, 400-500hz hump????

Has anyone had a problem with a sharpish hump of 4 or 5 db across 400-500hz in the 12LTA?

I had them in my open baffles, which are multi way. The sub is an 18" Tymphany. They have been replaced with rare-ish Bozak b199a (Much easier to work with). You can see that the 12" Eminence does not have much baffle around it. The LTA was crossed over low to avoid the menacing 400-500hz hump, but still did not sound great. Hell on certain lower register female vocals.

I measured the driver out of the baffle, on the floor, the mic level with the surround (super near field) and saw a similar ungraceful hump.

CAN BE SEEN HERE:

http://www.diyaudio.com/forums/clubs-events/290124-puget-sound-diy-speaker-contest-2016-a-5.html

The open baffles are the ovoid shaped ones. A side view can be seen on the preceding page.

I am not sure what to do with these 12LTAdrivers now. I have not tried the mods yet, largely because I am skeptical that they would help with this 400-500hz problem.

Any recommendations for a simple project that will make these useful?
Woodworking is not an issue, but time is, if they will not really shine.