1. I was wondering what the differences would be between these speakers (ER18 MTM or Aperion Intimus 5T). Please answer in language intended for an eight year old, I am only an enthusiast!
I heard an Aperion tower about 2 years ago and it wasn't bad. I'm sorry but I don't remember more details or even the model.
Cost – Intimus 5Ts are about $1000 a pair, ER18 MTMs are $600 (dome tweet version) or $681 (ribbon tweet version) for the parts alone. Lumber and labor are extra, and are your choice.
In my own opinion, the ER18 MTM's sound is somewhere between the the $2000 Salk SongTower and the $4500 Salk HT2-TL. I like to think of it as a poor man's HT2-TL.
Size – Intimus 5Ts cabinets are smaller 38"H × 6.3"W × 8"D, ER18 MTM cabs are larger 44½"H × 9"W × 13½"D and much heavier.
Bass Depth – Intimus 5Ts go down to 55 Hz, ER18 MTM go down to 35 Hz.
I'm going to guess that the more expensive SEAS ER18 midwoofers will handle more power and in general sound better, but that is a guess based on the good reputation SEAS has earned. I don't know who makes the Intimus woofers or the tweeter. The Dayton RS28 dome or the Fountek ribbon tweeter (both are options in the ER18 MTM) are both very good known performers.
Dennis Murphy has a well-known reputation among DIY builders for designing speakers with a very clear and clean sound across the midrange which includes the crossover region. The ER18 MTM is a good example of that. He is also the designer of the Philharmonic Audio speakers, and most of the Salk speakers.
I know little about the Aperion designer, but I suspect he also knows what he is doing. Aperion is a small company where the designer might be the owner, or if not the owner, he is in a position where he could control the product design enough to prevent the marketing department from mucking up the design.
2. Are there more DIY project for MTM style speakers because of the complexity of a TMMWW style cabinet or because the sub should take away the necessity of the woofers in that scenario?
Yes a TMMWW speaker is much more complex to build and more expensive to pay for. An MTM such as the ER18 with two quality SEAS 7" woofers can dig deep enough, down to about 35 Hz, to do fine for music without a sub. The deeper sound effects in movies is better done with a sub or two.
3. Why in builds is there an advantage to rounding exterior corners (on bracing) and not interior corners (inside of the cabinet where the side meets the back/front/etc)
I'm not sure I understand what you mean by "rounding exterior corners on bracing". Braces are on the inside of the cabinet.
The only edges that benefit from being rounded over are on the outside of the cabinet, on the front panel (called the baffle). The vertical side edges of the front baffle, if sharp, can become secondary sound sources in the mid and upper treble range – a physical process called diffraction. These can interfere with the sound from the tweeter itself and create unwanted peaks in the sound. If these outside front edges are rounded over, it minimizes this problem. For the same reason of avoiding diffraction peaks, the tweeter can be mounted slightly off center.
Rounding over other exterior edges has a nice appearance, but has no audible purpose. Rounded over edges inside the cabinet will not be seen or heard.
4. Why are frequencies only split once in an MTM speaker. eg. tweeter >2000Hz / midrange < 2000 Hz. Wouldn't the sound get clearer if you split what the two mids were responsible for?
You are describing what is called a 2½ way speaker. Some are good and some aren't, just like with MTM 2-way designs. Broad generalizations can be too broad and too general. The devil is in the details.
I hope some of this helps. If you want a pdf file of the ER18 MTM plans, send me a PM with your email address.
Richard
