RADIOBOMB SOUND SYSTEM OFFICIAL: Horn Loaded Tops (Part 2)
As my 3 week vacation ends, the quest to finish RADIOBOMB’s Official Sound System has come to an end and the horn loaded tops are finished! In this picture, you can see the tops stacked on top of the sub. As you may remember in part 1 of the build, their were very strict requirements for these tops. I wanted to create an all around top that can do multiple duties and be used in a multitude of settings. So I came up with these parameters that these tops are required to be, which are: 1. 8 ohm that can go to 70 hz (check), 2. Stackable and Pole mountable (check), 3. 100% Horn Loaded (check), 4. 50lbs or less (I am not sure, have not weighed them yet), 5. MTM style (check), 6. Sounds good with cheap speakers (check, with a little eqing), 7. Looks good (havn’t got there yet).
Okay, so lets critique the system and how it sounds. The sound system is an MTM style horn loaded enclosure using 10 inch woofers and a compression driver crossover at 2000hz. You may say that is not very original, but I assure you the devil is in the details above. The hardest part was making sure this design met a multitude of requirements. I know I can build a better sounding, more powerful speaker system, but the premise was to build a compact, multiple use, affordable speaker that sounds really good. So to compare, I used a few different speakers for reference. I have built a pair of DR250’s and OT15 from billfitzmaurice using recommended drivers, I also have a JBL TR-215, JBL EON 15 and a Yorkville NX300p used for comparison. I have built two different set ups to test,
Set -up #1 = Chinese made woofers, cross-overs, and compression driver. I bought all these speakers and parts from http://www.mcmelectronics.com, and the whole tops set up was less then $50 dollars. I used the MCM 55-3211 4 ohm woofers ran in series to get an 8 ohm load, along with an audio pipe 2-way crossover and an MCM 53-1210 compression driver. And they are all soldered in with speakon connections.
Set – up #2= USA made speakers, I used eminence Delta 10B 16ohm woofers with a selenium D 220ti compression driver. All the rest of the parts are the same.
Test #1: Sound quality
S1 = Sound quality was descent. I had to eq the midrange with an increase about 6dbs at 400hz and 1000hz, plus I eq’ed the highs at 5kh @ 3dbs and 16khz @ 6dbs. Once I dialed in the equalizer, I set the high pass at 80hz. With the subwoofer low passed at 80hz and high passed at 30hz. The set-up you see in the picture shows a very entry level system, which consist of a 12 channel behringer mixer, DCX 2496 Speaker Management System, and EP 4000 amplifier.
Once I started playing all my favorite tracks, I can really begin to hear the flaws of the speaker and begin to continually equalize the speaker. Once I dialed in the sound and begin playing them at a high SPL level, I forget that I am using $10 dollar speakers. Although the sound is not as crisp as I would like and the mid range detail not as clean, overall sound quality is very good. If I would rank the sound from 1-10, I would probably give the tops a 7 using this set-up. The main issues I have with this set-up is that the upper mid range detail is lacking and if I try to equalize it higher, the sound begins to get harsh. In conclusion, I believe this design passed all the requirements of my test, except for the most important one, sound quality. So then I decided to change the compression driver to the selenium D220ti and what a difference it made. The upper mid range detail was there, but now the woofers where not loud enough to keep up with the selenium compression driver. So with more equalizing, I was able to make the tops sound good again, but who wants that. A speaker should sound good as soon as you plug it in, and then you should equalize it according to the room and music you are playing. With that in mind, lets review set-up#2.
S2 = Sound quality was much more balanced with very minor equalizing. The SPL had a significant difference, on the amplifier S1 was ran at about 40% of the amplifier power, while the S2 set-up was at about 25% of the amplifier power. That is significant in terms of overall power usage because since the speakers are louder, there will be less amplifier power to power them up. So less likely of any type of amplifier meltdown.
In conclusion, I like this set up with the Delta 10b speakers with the selenium D220ti speakers because the sound quality was much better then the Chinese speakers, especially in the detail of the sound and overall SPL. The difference in price of the speaker parts is significant as well. This set up, speakers only, cost $50 dollars for compression driver and $80 per woofer, so that is a grand total of $210 dollars. If you add the price of building materials and minus the labor (1 day of building), this speaker cost about #280 dollars. Next is to add either duratex or speaker carpet and a speaker grill for protection. And with that, the grand total will be around $350 dollars. Not bad…. but as always there are improvements that can be made. So far, I have met my goals I had for the speaker except the weight issue and I want to add a phase plug for the woofers so that I can get a little bit more sensitivity about 1 or 2 decibels and flatten out the mid range a little bit. As for the weight issue, I want to make a pure fiber glass front horn enclosure. This will knock off about 25% of the wood weight or 12.5lbs, plus if I upgrade the speakers to neo magnet speakers, I can take another 10lbs off. Which might not sound like much, but if I was carrying this speaker by myself, instead of 60lbs, the total cabinet weight would be at 37.5lbs.