Autotuba almost....

[Tom Smit]

My favourite third son told me one day recently that the car stereo had skeleton speakers. Huh? Answer: no meat in the sound. I figured it was time to finally tackle a new project, an AT. Well, I got mine finished except for a coating on the exterior. There are a few faults, ie, placement of panels off by a touch (1/8") and panel six off by 1/2" at the mouth. But never-the-less, it works. Even with running a full-range 8" Volvo speaker. I did a quick hook-up to the bookshelf stereo and it noticeably improved the bass. Then I tried it in my car/wagon both facing the side and the rear....and it doesn't compete with the Kicker that my son put in. The Kicker is getting about 100 watts, the AT about 50. Problem is, the Volvo speaker was bottoming out at the power. So, I'll have to wait to get a 55-2421 and try again.
PS-it's true that the horn filters out the highs.........veeeeeery interesting.(Klink?)


Edit-re-read the instructions and I installed Panel 6 correctly.
-and, the amp is 300 w. / ch? or 1000w? according to my searches. No info on the amp (Kaption HO 50.4).

[Rickisan]

I see nussingg nussingg!!!!

[bgavin]

The mouth (tuba) flare isn't really part of the horn flare, so an error here is minimal.
The throat is the critical part, in any horn.

AT is a lil' butt-kicker... your Favorite Third Son (mine is Favorite Middle Daughter), will no doubt enjoy it.

[Tom Smit]

Well, I got my AT running right today, but, first I must tell you all how my day went. I went to cross the border and half a mile out (1 km) I came to a stop because of a hold up on the US side of the border. It took 45 minutes to reach the toll booth, I asked the traffic directer what happened and he explained that a bunch of tractors (field-type I think) went across the Blue Water Bridge and came back, and that it would take at least an hour for Customs to clear everyone. So I turned around, drove south to take the ferry to cross the St. Clair River to Marine City (45 minutes from arrival at ferry to reaching Customs. When I got to Customs, I got asked where I was going to and I explained that I was going to GC. Why? Heh, I stumbled with my answer (look at bass amps) and had to go to secondary inspection. They asked what was in the wood box in the car, I said it was a speaker cab. Well, they had to listen to it because there was no speaker showing. This was another 20 minute delay. Finally, I get to DJPhatman at 2:30 instead of 1:00, but there was a misunderstanding (he was waiting at GC). So, it was not until 4:00 that I finally hooked up with him! (My trip should only take 1 and 1/4 hour.) But we had a great conversation. And I got to remove the Volvo full-range speaker and put in the 55-2421 in the parking lot.

[Tom Smit]

OK, and now the review with the right driver.....AWESOME!!!! While DJPhatman and I were talking, both of us couldn't get the silly grins of off our faces. I had a great ride home, and demo'd it to my sons. While it does not have quite as much as the, actually it's a Rockford Punch Z 12", it is close. And the Rockford is receiving twice the power, the little '8' is not broken in yet, and the AT has an air leak (an empty drilled hole in panel 1, I think). The boys are IMPRESSED.

[Rickisan]

My favorite first daughter likes hers as well. The car is a Saturn SL and the AT fits snugly leaving exactly half of the trunk free for other pack space.

It is running an Alpine MRP-M350 ($50 Craigslist purchase) spec'ed at 200W @ 4ohms. So about 100W @ 8ohms. We want to run some test tones via CD through the system and check phasing and crossover frequency... although it already sounds very very good as is...

We will post pictures and review when finished.

[bgavin]

Remember, the 55-2421 is a 4-ohm driver. You will have the full 200w available, which will smoke the 55-2421.

I own a number of Rockford drivers. RFR-22xx series, in both 10" and 15". Very well made.
The RFR-2215 is perfect for a THT box.
I have an RFR-2210 running in a T24-I box.

The TAT is living proof of all the wonderful refolding possibilities of the AT.
The RFR-2210 would probably work very well in an AT modified taller to accept the driver height.

[Rickisan]

Oh gosh! Thanks for the heads up. I'd forgotten the driver is 4 Ohms... I do remember something about the acoustic properties of the AT adding Impedence in varying amounts depending on freq. so maybe will help us a little?

If it's not too late... I'll go back and reset the Gain control a little lower. Worst case we will be putting in a new driver.

Sorry for the thread Hi-Jack

[Turntablist]

Oh gosh! Thanks for the heads up. I'd forgotten the driver is 4 Ohms... I do remember something about the acoustic properties of the AT adding Impedence in varying amounts depending on freq. so maybe will help us a little?

If it's not too late... I'll go back and reset the Gain control a little lower. Worst case we will be putting in a new driver.

Sorry for the thread Hi-Jack

The horn is too short to add any impedanceload worth mentioning. And remember, the gaincontrol merely controls how much the inputsignal is increased so a stronger signal will still make the amp go full tilt and since you can't hear the driver beg for mercy, you might blow it..

[jcmbowman]

Oh gosh! Thanks for the heads up. I'd forgotten the driver is 4 Ohms... I do remember something about the acoustic properties of the AT adding Impedence in varying amounts depending on freq. so maybe will help us a little?

If it's not too late... I'll go back and reset the Gain control a little lower. Worst case we will be putting in a new driver.

Sorry for the thread Hi-Jack

The horn is too short to add any impedanceload worth mentioning. And remember, the gaincontrol merely controls how much the inputsignal is increased so a stronger signal will still make the amp go full tilt and since you can't hear the driver beg for mercy, you might blow it..

Ummmm.... per the plans:

The recommended driver is rated at 4 ohms, but the horn loading increases the minimum impedance to 8 ohms throughout the nominal pass band

Also, to whomever above said that there was an air leak in their AT - fix that leak ASAP. It will not only decrease your output significantly, but puts unneeded strain on the driver - making it MUCH easier to produce the evil magic smoke. Yes, it's only a $35 driver, but it still sucks when you fry one and have to live without bass for half a week while you wait for the UPS man to show up.

[Turntablist]

Ummmm.... per the plans:

The recommended driver is rated at 4 ohms, but the horn loading increases the minimum impedance to 8 ohms throughout the nominal pass band

I was under the strong impression that a short horn with fewer bends would have a much lower added impedanceload.. Sorry 'bout that, my bad..

[jcmbowman]

It's a smaller horn, but it's still a 7 foot (that's over 2 metres to you foreign folks) horn path....

[Sydney]

Is there an impedance sweep of an AT available?
( I have seen them for the other MCM 55-2421 driven cabs, and measured my T18 against the published graph. )

[WB]

Is there an impedance sweep of an AT available?

Would this be of any use?

[Sydney]

Well WB, as the saying goes...
"It's better than a sharp stick in the eye"
I figured I'd get the IITP.
I wonder what the Untitled freq marks are?
I find the 28Hz peak, and the saddle @ 44.7Hz interesting.
I'd also like to see the phase curve.
( My speaker building is on a "only if needed" basis, but If I ever get around to an AT I'll run a sweep. )