3110A x-over question

[4345]

I have been attempting an 18" two way system. It uses a JBL a 4518 enclosure loaded with the 2242 and a 2446/2380A combination for the highs. The x-over I am using is a 3110A at 800hz.

I just hooked it up, but find the bass lacking. I think it is more of a level thing, rather than lack of deep bass output from the 2242. I know you should probably not bring the 18" up so high, but I was hoping I would get lots of upside and not too much downside with this simple arrangment.

There is a 3 position switch on the x-over. Even with the horn turned down as much as possible, it does not sound good. Does anyone know the specs of this X-over? I know the 2242 is around 97dz at 1 watt, I would assume the horn is around 112db at 1 watt. How much is this x-over attenuating the horn?

Although I am reluctant to do it, I may need an EQ, Electronic X-Over or a better passive design in order to match the drivers better.

Any comments would be appreciated.

[Zilch]

Use an L-Pad on the horn. The HF boost contour of the 3110A varies with the switch settings.

The curves are in the "Quick and Dirty 4430's" thread:

http://audioheritage.org/vbulletin/showthread.php?t=3838&p=41315

http://audioheritage.org/vbulletin/showthread.php?t=3838&p=42419

[4345]

Thanks for the advice. Where should I buy the L-Pad? Is there one that is better than others. Will it degrade the sound at all?

[Zilch]

3110A is optimized for 16-Ohm HF drivers, but can also be used 8-Ohm with slightly altered performance.

L-Pads are available at Parts Express in both 50 and 100-Watt versions. Use one matching your driver impedance. Generally speaking, L-Pad will not degrade the sound. Once you determine the optimum balance, you can replace it with fixed resistors....

[spkrman57]

It has a rising response which is approx 6 db higher than the midbass/bass notes being reproduced.

Ron

[Mr. Widget]

I have been attempting an 18" two way system.


There is no way to pull that one off without accepting quite a compromised sound.



I just hooked it up, but find the bass lacking.


The 2242 has powerful bass when used properly. It really shouldn't be used above 100Hz. You are right the rising response will make the bass seem weak.
If you filter out this range and use the woofer in a properly tuned box, the bass is quite powerful and very deep.

Widget

[Zilch]

Max recommended xover frequency for 2242H is 1 kHz.

It may be possible to tame the rising response witha LF filter tweak.

I have no clue what it sounds like up there.

http://www.jblpro.com/pages/pub/components/2242.pdf

Lancer'd know both answers, maybe....

[4345]

Widget,

Thanks for your comments. I appreciate it. I am not a technical wiz and have no testing gear. So, I can only go by what I hear.

Does this rising response only happen in the 2242? Or does it happen in the 2245 as well? I actually heard an 18" two way at the AES about 15 years ago. TAD had a box that had 2 x 18" woofers and a 2" horn for the top end. One woofer faced out the other in. It sounded quite good. I think they rate their TL-1801 to go quite high and have a good transient response. I thought the 2242 would be similar. If they can bring a 15" to 1K in the 4430 I thought bringing the 2242 to 800hz would be OK.

I would like to get the levels more closely matched and see how they sound. Perhaps most of the problem is the fact that the horn is just putting out too much level.

[Mr. Widget]

A TAD 1801 or JBL 2245 would be significantly better than the 2242 in a two-way, and then they would be better at 500Hz or lower instead of 800Hz. Are you doing this for domestic or PA use?

Speaker design is always a study in juggling compromises. The TAD 1801 is more comparable to the 2245 but with greater SPL capability. The 2242 would not be acceptable for a two-way system to me.


"If they can bring a 15" to 1K in the 4430 I thought bringing the 2242 to 800hz would be OK."

I don't think running the 2235 up to 1KHz is a good idea... even though it was a compromise that JBL deemed acceptable in the 4430.

"Max recommended xover frequency for 2242H is 1 kHz."

To what end? A 2235, 2245, LE15A, 2242 etc. will reproduce 10KHz too, but only on axis and not as well as a pair of small Bose....

There are two primary issues with using large cone drivers to reproduce higher frequencies.

First: The polar response is directly related to the diameter of the cone. As the cone becomes larger in diameter the response at higher frequencies becomes increasingly more focused on axis.

Second: As the cone gets larger it gains mass. While it is possible to use more powerful magnets to maintain transient response, even with stronger motors the larger cones are more susceptible to breakup. The bottom line is that the "quality" of higher frequencies produced by larger woofers is simple not as good as it is with a smaller driver. (This is why the 4345 uses a 10" driver at 300Hz above the 2245. The 4350 uses a 12" for the same reason, and uses the 12" driver over the 10" driver since maximum SPL at low distortion was the goal.)


Widget

[4345]

Widget,


Thanks for your response. I am sure you are right. I still would like to test the system out a little more. I actually am using just the top end of my AS-2212 speakers. These are 12" 2-way cabinets. I just turned them over and put them on top of the 18" cabs. They use the 2206. So, I can easily make a 3 way system. However, I don't have the x-over to do it and really do not want to have a biamp rig.

I just wanted to try this because of that audition at AES many years ago. There are some who feel there are benefits to a 2 way design over 3 or 4 ways. I do think it holds some promise from my initial listening. I am using this for home audio, not PA.

If the system starts to sound very good, I can always switch to a TAD TL-1801 and a 3115A.

Zilch mentioned using a fixed resistor to lower the level of the horn. Since there is already a level adjustment in the 3110A perhaps I could skip the L-Pad and go right to using a resistor. The 2446 is 16ohm and the 2242 is 8ohm. I think I need to lower the horn 4-6db. Could you tell me what value resistor to use? Is it just one resistor per side? Where would I connect it?

Thanks.

[Zilch]

It's two resistors per side, still an "L-Pad," just fixed rather than variable. Go to #122 in the right column here:

http://www.bcae1.com/

I believe Mr. Widget would agree that two-way is a desireable configuration in many ways. Problem is, nobaody's been able to overcome the inherent compromises. 4425, 30, and 35 were a notably successful attempt....

[4345]

Hope this does not sound too stupid, but...

I am assuming a 3110A is designed to use a 16ohm horn driver and an 8ohm woofer. What happens if you use a 4ohm woofer instead? Does the x-over point change? What if you used an 8ohm horn driver?

Thanks for any help.

[Mr. Widget]

The low pass portion of the 3110 uses a textbook network for ~10 ohms @ 800Hz, if you lower the load impedance you will no longer have the correct load for that filter and it will not be working as specified.

The high pass portion of the 3110 uses an autoformer so you have more latitude, but I am not sure about the 3110A.

Widget

[Zilch]

3110A brochure cautions against using any LF driver impedance other than 8 Ohms. Doing so messes with the crossover frequencies and attenuation.

As Mr. Widget points out, the tapped inductor HF section is more "forgiving." Read through this thread:

http://audioheritage.org/vbulletin/showthread.php?t=5629

The 4660 uses the HF section of 3110A. We present actual response cuves using 8- versus 16-Ohm HF drivers on 2346 horns there....