Checked out your plans for the midrange which motivated me to play with a couple pieces of MDF over the last couple of nights. It sure amplifies the midrange. I noticed on the Delta 10 the SPL rating is normally around 100 and you're finding 108 with the horn on. That's about an 8 SPL increase.

I got one horn put on tonight mounted to the horn directly in front of the midrange. (temporary test position). There is a noticable increase in volume. I'll have to get things set up properly and on both sides before I know what happens to sound stage. One thing I love about horns is the detail that comes through. When someone takes a breath you hear it.

I have the PHL 1660 midrange which is only a 6 1/2 inch speaker.
PHL suggests it can be used for horns though. It has low Q numbers as well as the rising SPL numbers which makes it suited to the conical horn. It's rated at 97 spl with a 250 watt maximum rating. The speakers suited to these horns are not flat at all. To give a 97 rating is a bit of a joke. It should be a 95-100 SPL rating or something like that.

With any luck the link to the graph and specs works.

http://www.akkus.com.pl/glosniki/szczegoly.php?firma=phl&model=1660

I figure that the smaller speaker radius gives about 2/3 the area of the 10 inch driver and knocked the throat opening down proportionally. (to 3 inches from 4 1/2 inches) I left the horn width 1 1/2 inches narrower and kept the rest of the dimensions the same as your plan. I'm hoping that leaves the compression about the same, the dispersion very slightly altered, and the SPL improvement about the same. I remember on Bruce Edgars plans they used to mount with about a half inch space between the driver and horn and used some of the MDF as a spacer.

I hope things are going well for you and your family. It should be a good summer.

Grant.

To match sensitivity levels, you can pad the horn with a 4 ohm resistor in series and an 8 ohm resistor in shunt. This brings the sensitivity down but dynamic range is still increased by horn loading. And drive requirements are less, so distortion is reduced too.

For a spacer, you can sure use the spare MDF you're talking about, but that requires you to cut a ring. Another way to do it is to use an extra gasket as a spacer. They don't cost much and most recone shops have them.

Thanks for the response.

A second way of playing with efficiency would be to play with the compression ratio if I'm following this idea right. I suspect that would be done by using a slightly larger hole in the mounting plate.

I notice that your model showed a square hole where Adrian used a round hole in front of the driver. I would expect a 4 1/2 inch square to have a lot more surface than a 4 1/2 inch circle which would affect compression ratios.

Still playing.

Grant.

I didn't mount the horn in a cabinet so I had no "rear cabinet" at all. I didn't have a contained compression area either. I just built the horn, attached it in front of the speaker, and got major amounts more sound. I didn't even do both speakers. If the speaker was in a music hall it would have probably had problems. In my living room it didn't.

Even with the little work I did it still makes a HUGE difference. It confirms what you say above. Horn shape and size make a big difference.

I figure the size has a lot to do with how low a frequency the horn affects since the lower the tone, the longer the sound wave. The shape controls dispersion and I would expect with most people having 90 degree horns on the top end they would like to match the midrange to them. If you don't I expect a seating position right in front of the speakers would match up well. Off center would have waves of high and midrange not matching well.

I'll go back to car basics. If compression isn't affected by the size of the hole in the mounting plate a "slightly" wider gap between the speaker and hole should lower compression, therefore SPL increase.

Have a good week-end.

Grant.

You're right about size. Having a horn in the corners does a lot, since the corner itself is essentially a very large conical horn. But putting that aside, you really need size to get the response down low. That's why I like the π cornerhorn. It uses the corner as the complete horn, and it's simple and effective.