Suitable midrange cone, for bandpass mid in Unity horn.

[winslow]

The thing with JBL is they will sell you any parts over the counter to say, but the speakers have to be bought from an authorized JBL Pro Parts dealer.

Just in case someone is looking to buy those little speakers.

[paulspencer]

Everyone who expressed interest in the group buy should have now received a PM

[paulspencer]

I'm now working on S3, which I'm thinking of making 80 x 60. I don't actually need 90 degrees dispersion. A few things happen as you change the coverage pattern. One is that narrowing it makes it harder to mount drivers. Another is that you tend to lose a bit of bottom end extension. Also you tend to make the mouth smaller, resulting in a loss of pattern control at a higher frequency. In S2, horizontally I had a constant beamwidth down to 280 Hz where there was a big mouth and 90 degrees. Vertically, where I had 40 degrees, pattern control is lost much sooner. The result is pattern flip. The narrow coverage only occurs up higher, and in the midrange the pattern starts to get more broad again.

[bwaslo]

Looking around for some cheap midranges to play with, I ran into these:
2" Paper Cone Midrange Tweeter 4 Ohm 289-127

They are open back, but the resonance is high and the compliance is stiff. Even with a big back chamber they seem to work pretty well with HornResponse (the volume behind does not affect it much). Not the most efficient in the world, but with 2" diameter, it can be pushed nice and high in frequency. Assuming the given parameters are close, of course. The price is very cheap for experimenting, looking at 4 or 6 in a synergy horn with a high upper crossover to a small compression driver.

I don't know how many they have, will have to stop up and ask.

[paulspencer]

My sims are suggesting good top end extension is possible with the Celestion 4". Here's an example modelled in both Hornresp and Akabak:



Green is Hornresp

Which one is more accurate? Well here's both against a measured example where I put the Celestion 4" on S1, just a single sample driver and then I modelled it:



Here Hornresp is red

I have found that one can get more out of band output than expected from Hornresp - Akabak is better at predicting that. However, down to the first peak, I've had better results with Hornresp, also with the bottom end extension. Perhaps that changes when one learns to drive Akabak properly, as I've just exported the script from Hornresp. Yes - cheating!

[winslow]

Paul are you doing the ports at 1/4 or 1/2 wavelength distance from the compression driver?

[paulspencer]

That is 1/4 @ 1.5k ie 57mm

[bwaslo]

Here is a HornResponse sim using 4 of these 2" midranges on a 90x60 conical 450Hz unity type waveguide. I've also seen these drivers at Marlin P Jones, not bad for a buck and a half each.

Originally Posted by bwaslo

Looking around for some cheap midranges to play with, I ran into these:
2" Paper Cone Midrange Tweeter 4 Ohm 289-127

They are open back, but the resonance is high and the compliance is stiff. Even with a big back chamber they seem to work pretty well with HornResponse (the volume behind does not affect it much). Not the most efficient in the world, but with 2" diameter, it can be pushed nice and high in frequency. Assuming the given parameters are close, of course. The price is very cheap for experimenting, looking at 4 or 6 in a synergy horn with a high upper crossover to a small compression driver.

I don't know how many they have, will have to stop up and ask.

[ErnieM]

I bought a box of those for some line arrays...this looks more interesting. Nice little driver. Also have a pair of de250's. I think I have a change of plans now.

[bwaslo]

Went up to Parts Express today and picked up 9 of these little guys. I measured the T/S parameters, a little off from what they were quoted, but no less usable. Here are shots of the T/S, new HornResp values, and simulated response curve for a 4x4 arrangement:



They have on the order of 300 of these in stock.

These won't be easy to seal the backs on because the terminals are so close to the outer edge, but a lot of volume on the back doesn't have much if any effect (just stuff the back volume with damping). Could just put the whole synergy horn in a box for the back waves from these drivers.

I'm also getting some of the Celestion 4" mids that Paul Spenser recommends. These 2" ones though might be a good match for use with a CD that cuts in at about 2kHz, I'm hoping.