PDA

View Full Version : My Plan



JBLROCKS
02-18-2005, 05:20 PM
Here is my plan for my newly acquired JBL components (See: "OLD JBL FIND" posted earlier)

I plan on building two front woofer boxes like these:
http://www.highefficiencyloudspeakers.com/user/SH04-1201-22_A.pdf

These will be the front speakers and will contain the JBL 150-4 woofers and I am going to build a horn setup like the pictures...I am thinking a "tree" idea to make the horns seem suspended in space...

For the center I am going to build a similar box and use one of the Altec 603B's.

For the rear I am going to build a couple of "Corner" enclosures like the "Harlan" from 1957 :
http://lansingheritage.org/images/jbl/catalogs/1957/page5.jpg

These will contain the D130 Extended Range speakers with a single tweeter horn incorporated.

( I know the horns I built look a bit crude, I am going to make better ones out of nicer wood. ;) I built these pretty quickly to get the idea down and see how they would sound, they sound great! :D )

Steve Schell
02-18-2005, 10:42 PM
Hi JBLrocks, congratulations on your successful horn experiments. One reason they sound good is that you have built conical (straight sided) flares. Conicals have some stellar virtues... they maintain excellent dispersion vs. frequency over the angles formed by the horn walls. They also put about the same spectral energy into the reverberant field as their axial radiation, which sounds very natural to our quick processing brains. You might want to try knocking together some larger midrange horns at some point. I use a 300Hz. crossover point, and the best sounding conical mids I have made are 32" long, with a 24" by 28" mouth. A horn like this can provide some real goose bumps, just killer vocal reproduction.

If using passive crossovers I recommend simple first order networks at least as a start. Paying close attention to polarity and to the alignment of the drivers' acoutical centers to be the same to the listening position will allow for really holographic imaging. Don't just try to eyeball this; stretch a string from the center of the listening chair to the matching horns on each side to get things within 1/8"- it's worth the trouble. Placing the horns on a "tree" should work well. Be sure to try placing the h.f. horn between the midrange horn and bass section; I have found that this arrangement works really well.

Those bass cabinets should sound good, although you may want to consider building some straight bass horns for those 150-4s eventually.

Have fun! You may want to check in at the Audio Asylum High Efficiency Speakers forum from time to time and check back through the archives- lots of horn experimenters hang out there.

JBLROCKS
02-19-2005, 04:06 PM
Thanks for your input Steve. :D
Much appreciated!

You know of any places I can get plans for bass horns?
I have checked out highefficiencyloudspeakers.com but they dont have any horn plans...

Thanks again! :D :applaud:

P.S. I'm interpreting the horn size as 32" deep and mouth 24" high by 28" wide... Is this correct?

JBLROCKS
02-21-2005, 11:13 AM
Having a bit of a problem here...Perhaps someone can help me with it...The horns work so well they make the bass level seem difficient. This is OK on my recievr that had "Loudness" or bass boost control. However, my HT reciever does not have either loudness or boost so the sound is not as good.

Any suggestions?

Woofers are D-130 16 ohm
Horns are dome midrange and dome tweeters (Not sure of brand but nice and hefty, "Made in Germany")
Good X-overs attenuator on MR and TW outputs

Thanks
:hmm: :cheers: :wave:

Zilch
02-21-2005, 11:27 AM
Trust in the Zilchster, now, who only recently learned this hisself. You can't reasonably or rationally do this without an RTA. Spend $100 - $200 on eBay and get one.

D130's not gonna give big extended bass, in any case. Also, you've gotta be bi/tri-amped with active crossovers to get control of the system during development.

Otherwise, you're just depending upon luck and you'll spend the rest of your life trying to get it right....

Note: Boost is rarely the answer, except in final tuning. You want to cut to bring stuff into balance, not boost. Invest in L-Pads until you get it figured out.

JBLROCKS
02-21-2005, 11:34 AM
ummmmmm what is a RTA? :o:

sorry i'm pretty new at this

Zilch
02-21-2005, 11:50 AM
RTA is "Real Time Analyzer." It's a device with a microphone that "listens" to the system with pink noise playing and displays the spectrum of the output, each 1/3 octave. With it running, you dial you crossover frequencies and attenuation to balance the system.

It's how the sound reinforcement guys "tune" the system to the venue to get it right. You're just peein' upstream trying to do this stuff without one. Read up my current "Quick and Dirty 4430" thread for more, and that's just working with a two-way system. Also, use forum "Search" to see how others use them here. Little tweaks make BIG differences in how a system sounds, and you need instrumentation to understand and control what's going on.

There's ways to do it with your PC, as well. Other members will have to help you with that. For now, I like the stand-alone DOD unit Mr. Widget has loaned me, but there are others, too....

JBLROCKS
02-21-2005, 01:35 PM
Thanks for the info :D
MUCH APPRECIATED:D
Like I said, I am a bit new to this!

:hmm: :wave: