Like anything else, there are many ways to accomplish things, and some things work better than others. Resistors are neither "friend" nor "foe" - They're just part of a circuit. Loudspeakers are partially resistive and partially reactive, so sometimes a circuit is ill-formed without resistance.

Some circuits benefit from values of resistance in series and/or shunt, others don't. It depends on your specific configuration more than anything else.

thanks for any input! MERRY XMAS!!

The towers I'm doing is a 3-way design having a tweeter horn, midrange horn, and direct radiator 15" bass reflex to cover the midbass/bass. My particular one uses JBL 2225H's for the midbass/bass - thats a 15" woofer. Since my system has a subwoofer, I've tuned the cabinets to give about a 70Hz cutoff where it crosses to my 18" 18LW1400 subwoofer in a 300L vented box with small amount of electronic EQ which takes care of the subbass down to about 20Hz in my room.

Certainly, its possible to tune a 15" to have a cutoff of 25Hz or even less. Cabinet size will be your main enemy here though, its pretty typical that 15" woofers with output this low are going to be rather large. It may or may not be a problem for you. JBL 2235H is an excellent choice for bottom octave operation.

Where you set your crossover points will completely be determined by what your drivers are capable of, things to consider are distortion and bandwidth of each subsystem. My particular one has crossover points at 300Hz and 2Khz - but that only works for my configuration. You'll likely use a setup pretty different from mine, so your crossover points will likely need to be changed. Electronic crossovers used in pro sound are fine too, if the filter type and points suit your application.

I'm not using SET amps on mine, I need all the output I can get! I love to listen to music at high levels, and I like the sound of SS amps and other high-powered amps. I admit I've never heard any tube amp before ever, but I also feel that they wouldn't suit my needs. Just beware though that not all drivers are suited to SET amps - drivers which produce a lot of back EMF typically need an amp with good current sourcing/sinking ability, which means having a high damping factor, so tube amps are out of the question (they have high output impedance, inversely related to damping factor which would be low). As a guideline, its drivers with high impedance peaks at resonance which are not suited to SET amps. Wayne likes to draw the boarder at about 50ohms, anything below 50ohms impedance peak is likely to perform well on a SET amp, but anything above isn't, although it isn't a strictly 50ohms, its an approximation. Some tube amps behave differently from other tube amps too, so you may find that on some it'll work fine but it won't on others. If you do run a SET amp on a driver which produces large amounts of back EMF, the cone will be rather uncontrolled and you'll also notice a large lack of bass output in the bottom octave, motor strength is a function of current too and the amplifier needs to be able to source and sink the current or it won't be controlled. It's part of motor damping. Also SS amp's and other such high powered amps perform more like a constant voltage source so the load impedance of the driver doesn't have much effect on performance, but a tube amp act like it has a voltage divider and the cone goes crazy.

External dimensions for my cabinet is 46" high, 18" deep and 20" high, that is rounded to the nearest inch.

Adrian

WHAT DO YOU GUYS MEAN WHEN SAYING, "TUNING AN ENCLOSURE TO SAY 30HZ?" HOW DO YOU EXACTLY DO IT? BY JUST DETERMINING BOX SIZE? OR I STILL HAVE TO COMPUTE FOR A LOT MORE STUFF?

WHAT MID&HI DRIVERS ARE YOU PLANNING TO USE? AND SORRY BUT HOW DO WE CONVERT A CU. FT TO LITERS?

ARE PRO HORN DRIVERS ROLLED OFF AT THE VERY TOP END AT AROUND 12KHZ? WILL I LOSE SOME SPARKLE AND CLARITY IN MY MUSIC? MANY PRO SET UP USE EQ TO COMPENSATE, WILL I STILL HAVE TO USE EQ? DO I ABSOLUTLEY NEED TWEETERS OF ULTRA-HIGH FREQ. SUCH AS THE 2404H TO HAVE SOME SPARK IN MY MUSIC?

HERE NOW IS MY REVISED PLAN FOR DRIVER SET-UP FROM JBL, CAN YOU COMMENT IF THIS IS ALREADY A RIGHT SET-UP?
18" 2242H FROM 25HZ-100HZ VIA SOLIDSTATE AMP
12" 2020H FROM 100HZ-1.2KHZ VIA 22-WATT SET AMP
2" 2246H FROM 1.2KHZ-12KHZ VIA 22-WATT SET AMP
1" 2204H FROM 12KHZ-20KHZ VIA 22-WATT SET AMP

http://www.jlaudio.com/tutorials/magic/ported.html

ARE PRO HORN DRIVERS ROLLED OFF AT THE VERY TOP END AT AROUND 12KHZ?

Knowledge + Compensation circuitry + a good horn = good results to 16khz +

HOW DO WE CONVERT A CU. FT TO LITERS?

28L=1 cubic foot

Thanks for the kind words.

How you tune an enclosure depends on what sort it is. In a sealed box, the only thing you can vary is box volume, but in a vented box you get the port (helmholtz resonator) and the box volume too. Perhaps you would benefit from a site which explains the basics of typical box types like sealed, vented, bandpass etc. www.diysubwoofers.org

In my towers, I'm using 15" JBL 2225H drivers for the bass/midbass sections. The midrange is covered by an Eminence Alpha 6 driver horn loaded in a conical horn flare (which I designed and built), and the HF is JBL 2370 horn flare loaded with P.Audio PA-D45 comp drivers. If you want to see pictures of all my parts, see this post http://www.audioroundtable.com/HighEfficiencySpeakers/messages/100.html on the high eff AudioRoundTable forum. My subwoofer uses an 18" 18LW1400 in a 300L vented cabinet which takes care of 20Hz and up in my room.

Most horn/comp driver combo's do rolloff on the top end. Some horns self equalize (like radial horns do) in the top octave so compensation isn't always needed. However most do need some sort of compensation still. And, YES !!!! IT IS VERY, VERY IMPORTANT !!!! Go listen to some without a compensation network, AWFUL. You don't need a UHF tweeter like the 2404 though - just use a compensation circuit on the compression driver. Theres too many other problems introduced when crossing very high as well, I would prefer not to do it.

I assume you meant 2446 2" compression driver, and not 2246 which doesn't exist. JBL makes some crossovers which include high frequency correction to restore response up to 16KHz, which is all you need. Some compression drivers will allow you to go 18KHz. Another great way though is to use the crossover network used in Pi Speakers, which augments the top octave by removing attenuation there compared to the rest of the circuit, so it also matches sensitivity to that of the woofer at the same time. The first few octaves are flat before the augmentation kicks in, so its just what you need.

You didn't specify a horn flare for the 2446 - use the 2380 horn flare. Dont use the 2382, it rolls off way too early (+ it has too wide dispersion characteristics for home environment). Might I suggest though, since your using a 12" driver for the midrange and its capable of HF extension into many kilohertz that you use a 1" exit compression driver instead, like the JBL 2426. The 2" comp drivers don't reach into the top octave very well, their diaphrams are too big. They go lower in frequency though, so they are normally paired with 18" speakers which can't go very high. Since your 12" can go very high though, then use a 1" exit driver. You will gain more HF extension on the top end. In that case, use something like the JBL 2370A horn flare on the 2426 comp driver.

I suggest you use the 2206 12" instead of the 2020. If you look at the response curve for the 2020 you'll notice that its got a fair bit of variation throughout the midrange, its a continually positive rising slope. The 2206 on the other hand is dead flat through the midrange and well into the treble region too until a bit past 2KHz. It also handles more power, has lower distortion, etc. The 15" 2226 is also really good.

Good sub there, 2242. You'll need to use some EQ on this one though. JBL makes a unit which does the electronic equalization for the bottom octave I think, but the Behringer Ultra-Q Pro PEQ2200 fully adjustable parametric equalizer is also really good for the job, its US$99 (probably a lot cheaper than any JBL EQ). JBL reccomends 8ft^3 vented cabinet tuned at 25Hz for this. Set the EQ to give +6db boost at 25Hz with Q=0.67 (2 octave bandwidth). It gives a nice smooth curve when used with the 2242 in that box alignment, and has a small gentle rolloff on the low end, so once you factor in room gain the response curve is nice and flat to the lowest frequencies.

Adrian

Check out the other stuff there too, such as the cornerhorns, etc.

Knowledge + Compensation circuitry + a good horn = good results to 16khz +

How do you get the "Knowledge" to design the "Compensation Circuitry?"

For example, I have ordered a pair of BMS 4592 2" compression drivers from Bill Martinelli. Say, I want to build a crossover for a speaker using this driver. (I have not studied xo's yet, so please forgive me if I spout newbee nonsense.) How do I know how to design the compensation? Suppose that I am the world's best crossover designer. How do I know what this system needs? Do I look at the specs for the drivers? Do I look at the response graph? Do I measure spl with my meter across the spectrum? Do I listen to the driver before building the crossover? Trial and error: build a crossover and tweak it by swapping components out one or two at a time?