Hey guys, I’ve floated around here for a while and have learned a lot from you guys. However I haven’t come across the pros and cons to the driver placement for an mtm like in the drawing I attached. Is there any benefit to having the midrange drivers close together and the tweeter in between off to the side?
Side note: The drivers are the Satori MW19P-8 7.5” for the midrange, and the SB Acoustics SB29BNC-C000-4 29mm Beryllium dome tweeter.
Thank you guys!
Side note: The drivers are the Satori MW19P-8 7.5” for the midrange, and the SB Acoustics SB29BNC-C000-4 29mm Beryllium dome tweeter.
Thank you guys!
Attachments
Given how compact the tweeter is i’d call it a no-brainer. The tweeter sits inside the edge of the mids.
8” C-C would suggest a practical XO of <1,700 Hz.
dave
Awesome, I was hoping that this type of layout would help mitigate some of the lobing issues in typical MTM designs but was worried it might introduce other problems, so thank you! Also thank you for taking the time to draw up that layout.
You are addressing what might be the largest concern, partially at least. Do you plan to use this configuration to achieve the original D'Appolito goal of mirrored crossover lobing?
I’ve just gotten deeper into trying to understand loudspeaker design from a DIY aspect, and to be honest I’m unsure of what that is. I’m building a three-way active 4ohm MTMW system with the goal of the achieving the highest output I can with as little distortion as possible, hence using an MTM based configuration. For the woofer I’m thinking about using the Dayton Audio RSS390HE-22 15”, it seems to be the best value I can find for power handling and sensitivity. I plan to drive the woofers with my Gen 1 Emotiva XPA 1’s (currently used to drive my passive towers), and build hypex n core 400 amps for the for the two pairs of mids and the tweeters. I know later D’Appolito designs used a 4th Order LR crossover so my plan is to start with a 24db slope at my crossover points (100hz and 1,700hz).
Also I’m planning on using the 15” woofer front firing as I want to try a wide baffle design to eliminate baffle step in the midrange frequencies (baffle will be 18” wide with radiused edges).
The original D'Appolito plan was to eliminate lobing by using the mirrored MTM configuration. This required running the tweeters and mids with a phase shift between them.
Later it was shown that the twin midranges gave narrow directivity just below the cross, and some decided to begin using LR to make the lobing come back. The mirrored configuration is then no longer doing anything with symmetry, but it does increase the cone area. You may consider using it as a 2.5 way.
Later it was shown that the twin midranges gave narrow directivity just below the cross, and some decided to begin using LR to make the lobing come back. The mirrored configuration is then no longer doing anything with symmetry, but it does increase the cone area. You may consider using it as a 2.5 way.
I like it.
Understood, thank you! And since I’ll be using an active crossover I’ll definitely look into trying a 2.5 way.
I appreciate it! 🙏 I tend to question myself on every little thing in regards to whether or not I’m on the right path in terms of putting together at least a half way decent speaker design, so it gives me a bit more confidence in what I’m doing with this.
That’s crazy, what’re the odds? I actually just came across that this morning from one of your posts on a thread from way back in 2004 and was planning on reading through it after work tonight.
https://www.diyaudio.com/community/threads/dappolito-theory.36497/
I gotta say it’s pretty incredible seeing someone active for so long. How long have you been designing loudspeakers for?
Guess it depends on how 'flexible' we consider what 'design' includes since I've been active in DIY since 1956 at age 10, but WRT on-line, I got on the net Christmas '96 when I got my 1st computer, browsed/found audio/speaker BBs that I got banned for my trying to enlighten/'correct' all the BS marketing hype being passed off as real tech, etc., that littered them, then found the basslist, later replaced by these and other more 'enlightened' forums.
Anyway, there's folks here that predate me from the basslist and earlier, so kind of a 'Johnny come lately' actually.
Anyway, there's folks here that predate me from the basslist and earlier, so kind of a 'Johnny come lately' actually.
Dave for your drawing, the woofer is 187 mm outside diameter or 7 3/8
The tweeter is 104 mm. or 4 1/4
That appears to change the placement.
The tweeter is 104 mm. or 4 1/4
That appears to change the placement.
Dave, Direct radiating tweeters are almost always listed as their membrane or moving component size. You have been doing FRs too long.
Yes, I saw the original diagram that caused the confusion.😆
Yes, I saw the original diagram that caused the confusion.😆
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I suppose you could always front mount the woofers and rear mount the tweeter with a beveled or flared baffle (aka mini horn) and you could squeeze the tweeter in there better.
From my own experience, an MTM is where a wave guided tweeter will come into practical use. The WG places the acoustic center further back, closer in line with the LF drivers and also allows for a lower xover, both which can improve the power response off axis and widen the main lobe. Even with increased CTC spacing from the WG, the two listed benefits can prevail. Increasing HF directivity down low to match the LF directivity around the xover point helps as well. Angling in both LF drivers vertically on the baffle can improve things too.
I have some 1" tweeters that are approximately 29mm in diameter, i looked hard for any other info.
dave