Now look at the real world. Even a very good horn has excursion peaks and dips as you pass through the bass range. The best you can expect is to reduce excursion just above the flare frequency and then again at about twice that frequency, maybe even a third excursion dip above that. But between these dips, excursion rises and it is at those points that you'll want to focus your design efforts. Those excursion peaks will be what sets your limits on the low end.

Retsel

In all the designs I have built and measured, you need to pad down the upper frequencies with a correction circuit. The cabinet can be designed to produce bass equal in efficiency to the driver radiating into 2 pi space. However, by placing the enclosure out in a room the baffle step will exist which requires correction.

Martin

I would also speculate that you are probably getting weak bass and could use a BSC circuit to help tame the rising mid and high frequency response of the DX4 driver, this is probably why you are using a sub woofer to help the low end. With a good BSC circuit design, the sub woofer may not always be needed unless you really want to play bass heavy music.

Martin

However, I do not need to pad down upper frequencies in the Hedlund Horn to get balanced reponse. The Hedlund Horn is balanced from 80 - 100 hz up to 10 khz. Perhaps there is a combination of horn and tranmission line bass which gives the balance that the Hedlund Horn enjoys, or perhaps it is the room reinforcement. This is not just to my ears but to any who have heard my system.

The subwoofer I was using does not provide much boost for the mid bass as I was crossing it over at 38 hz with a third order crossover. The subwoofer is very desirable, though, for most all music.

Retsel

I am skeptical. I am skeptical because I am much more sensitive to transparency then most audiophiles. I work to remove as much from the signal path as possible. For example, years ago when people were raving about the Genesis digital lens, I tried one in my system and immediately removed it because it reduced the transparency of the sound.

In recent years I have been soldering or terminating my speaker wires and interconnects directly to my components to avoid the RCA connectors or speaker binding posts which rob the sound of its transparency. I wired my SACD player to remove all resistors from the signal path. I go directly from the digital chip through a set of mu metal transformers to the output. Thus, I am pretty aware of what I would like and what I would not like. I probably would not tolerate such a device in the signal path.

The upshot from taking these actions is that the sound from my system is amazing.

Retsel