Perhaps its time to try a new driver. Just analyising the Alpha 6 I was using again, its Fs is 120Hz, BL is 8Tm and Qts is 0.54. I think that the Qts is rather high for use in a horn.... perhaps this is limiting its HF response.

Using driver mass rolloff equation =2*Fs/Qes gives a mass rolloff on the Alpha 6 of 393Hz.

After searching around a lot, I saw an offering by Eighteen Sound which looks like a good candidate for my horn, model 6ND410. Its a 6" driver with a BL of 11.6Tm, and low Qts of just 0.24, and Fs is 120Hz. Driver mass rolloff equation gives mass rolloff of 888Hz! Very high compared to all other drivers I have looked at such as P.Audio ones and a couple of JBLs.

Hornresp predicts that the Alpha 6 and the 6ND410 both have about the same HF response in my horn. But the Alpha 6 in reality doesn't.... perhaps, the higher BL and lower Qts of the 6ND410 will make it better for the HF response that I (apparantly, grrrr at SW!) am missing with the Alpha? Below is the spec sheet for the 6ND410.

Of course JBL LE5 would be nice... but very rare.

Anyhow if anyone has comments on the 6ND410 etc, I would appreciate it. I would like to know weather or not its worth buying and testing out in my horn or not. I know 18-Sound does not make cheap quality stuff, however I want comments on the suitability of this driver in a horn etc, weather or not I would see an advantage over the Alpha 6...

Thanks for any advice guys!
Adrian

I would still appreciate comments on the 6ND410, that driver is really on my mind at the moment... although I really wanna make sure that I've made best use of the Alpha 6 before spending more on another driver.

Got some ideas off high eff forum about using a phase plug and a little larger throat, a round throat too to reduce more phase cancellations above 1KHz, perhaps I can get more response doing this.

I am going to kick myself for not buying those 2105's. I can only hope that they would not have worked good for me, I'll never know now.

About phase plugs and throat shape - My design approach has been to keep the midrange horn simple and crossover where required without a difficult flare transition and phase plug in the midrange subsystem. The idea is that the added complexity isn't required considering you plan to crossover at some point to a tweeter.

Phase plugs certainly help reduce path length related cancellations at higher frequencies. That's what they're used for. But I'm not sure you'll need one in a midrange horn like this. You definitely could design around one and make an excellent horn. But fabrication might be more difficult, and the extension you'll gain might have been easier to accomplish by different means.

Modern midrange horns designed for use above 100Hz or 200Hz are generally expected to cover the vocal range, and run out of steam in the overtone region, between 1kHz and 2kHz. Many of them use flares very similar to yours, some with phase plugs and some without. So I think you're on the right track here, and you just have to decide what compromises and optimizations are in order for your particular goals.

Also from the Electrovoice picture it looks like it has a one to 3 inch straight throat before it enters the concial horn. What effect would this have? Increase high frequency extension?

See this post http://www.AudioRoundTable.com/PiSpeakers/messages/1623.html and then scroll down to "Hybrid Flare". I think this is what your after.

I think last time why SW gave me a differnet result in the end (when I stated response to 1.6KHz on the conical, then I came back and said it was no longer happening) was because my filler block was kinda pressed against the cone. I knew this was happening because it was a bit oversized and I couldn't be bothered changing it to a more appropiate shape (used two smaller blocks that I had already made and put them togethor to form one big one), so what happened was at the beginning it limited cone movement and HF response increased, but after continuous use, a few hours etc, the cone no longer completed stayed limited. The cone sort of started 'bending', the filler block only limited it near the edge of the cone (towards the surround), so the part of the cone near the middle (towards the dustcap) started bending/bulding, however you want to put it. Kinda like cone flex, it only became apparant after continuous testing/strain on that day. Anyway, thats what happened... I have since removed that oversized filler block as it could also damage the drivers (no damage has been done though).

I started today building yet another conical horn... this time with a 110mm diameter throat. I will use changable sizing rings this time so I can try differnt throat sizes on the horn. Perhaps a little larger throat so that phase cancelations above 1KHz are reduced and also a phase plug too will get me my wanted HF extension, I'm pretty hopeful after my results with phase plugs today. I might post graphs here later of different phase plugs and their results etc, perhaps not for a few days though until I get everything done. Will post back.....