30-50 ohm resister in series with JBL 2446

[ivica]

Thank you for the information Ian. I realise that often someone has spent many hours and extended knowledge researching and coming to the right conclusions regarding specific audio components and crossovers and am extremely grateful for the advice.
Im on a tight budget running the 2446 with a 2" to 1.4" reducer on a 18 sound XT1464 horn crossed at 1600 hz. As the JBL 2446 seems to need correction above 8000Hz that's my crossover to the 2405 with either a capacitor or I might try a high pass and see how it sounds. Looking at the response of the 2446 I'm surprised you suggest running them up to 13000Hz? I do intend to upgrade to the Iwata 300 horn as soon as funds allow and then some Be diaphragms. I'm also looking for a simple way to try and time align the 2405, of course one can do this physically but it puts it so far back from the mouth of the horn that it creates its own problems. I'm looking to try a cheap and simple solution but am not happy about adding to the signal path, Behringer Shark DSP 110.

Hi David Ketley,

I would suggest you to use XR2064 -18sound 2inch horn if you prefer to get the most out of such driver as 2446. converting from 2inch to 1.4inch would not be the best solution. From my experience 2446 would work over 10kHz without any effort, if original not over powered diaphragm is used.

regards ivica

[David Ketley]

Okay

Most of these compression drivers when used in CD horns like the 18 Sound XT1464 either a passive eq or active eq to flatten the response.

You may have mentioned earlier but do you have any form of RTA or measurement kit?

There are some reasonable diy options at Parts Express.

Attempting to optimise CD horn passively is difficult without an crossover software package with an optimiser and take some skill.

For diy home audio all CD horns require an optimised eq contour as they tend to have constant directivity that means in the non eq state the on axis response looks like a banana.

The iwata is more diy friendly but will still require some intervention.

Many years ago I had a JBL 2397 horn and I took it to a friend who was running a college loudspeaker builder course and he measured the horn for me and built the crossover for the 2405.

Depending on where you are that can be a blessing if you can reach out and find some assistance.

If that is not an option you can self help and look at what the 18 Sound people do with this particular horn to make it function correctly.

A starting point is the 18 sound web site enclosure design tab. If you have a look at the 15 inch 2 way it's quite intuitive process. If you are keen as a starting point just use the eq part of the 18 Sound crossover and place a 1.5 uf capacitor in parrellel with a 27 ohm resister. This will be approximate but will be in the ball park as to normalising the CD characteristic of the XT1464 horn.

The effect of this is a response shaping network. It woks by attenuating the response from a selected high frequency in the form of a high pass filter . At the same time the lower end of the response has some sensitivity shave off

Most compression driver work on the same principle so you are not doing anything wrong by trying this.

Still use the large series capacitor before the above eq and crossover with the Marchand crossover at 1500 Hz. I would also suggest a fuse in series to protect the driver in the event of an accident.

The Lpad will not be required.

Measure the response if you can or listen to the horn with Pink noise (or an off station FM radio) and compare to the non EQ version of the crossover. Do not connect the 2405 at this point.

The horn should sound smoother and more extended.

You can then add the 2405 back and compare.

The horn will extend further but will tend to sound soft in the upper hf area. This is normal and I would listen carefully on some know program content .

Adding the 2405 will add spatial resolution with a crisp crystal quality.

I see http://www.eighteensound.com/Portals...15%202ways.pdf

Let me know how you go

I see http://www.eighteensound.com/Portals...15%202ways.pdf

I,m sitting in our caravan on the North Coast of Spain waiting to pick up a ferry home to the UK on Monday from Santander rafter 3 months away.
No I do not have any measuring equipment, I must admit to being reluctant as I know that although its important to get the basics right the endless pursuit of perfection can become an obsession leaving little time for actually listening, hence my trying to get a simple system that sounds good to me. The Marchand does have the facility to add correction cards for the drivers but as I intend to put in Be diaphragms and upgrade to the Iwata 300 later I will try and get the best out of the existing drivers following your suggestions. I did find that mounting my last UF unit a Heil P5 on a alloy plate in line with the top of the horn gave a nice response and it was correctly time aligned to the listening position. Will update on my return.
Thanks

[Ian Mackenzie]

Hi David,

Enjoy Spain and we can pursue this when you get home!

There are a number of great Lansing forum people in the UK and Europe who I am sure would offer to assist and from diy audio.com

Inrecall some off us met at gathering to hear Richards 4345 in SE London back in 2007.

Most UK audio buffs would be more familiar with small book shelve or narrow tower loudspeaker.

I wonder what they would think of the JBL movement?