Has anyone built this RS150 & Beston RT002a MTM before?

[nikkoluvr]

Hi All, I just finished assembling one of these and it seems very weak in the bass. Per Lou C. I shortened the port to 3" in length. I have a pair of the Core 2's, and one OS MTM sitting next to it, and they really kick it's backside on bass.

http://www.drmarksays.com/?p=82

Right now I have a .89 cu/ft. enclosure with internal dimensions of 6 1/2" x 12 1/2" x 19" high with a baffle width of 7 1/2". The port is 2" x 6" long. I have no damping material of any kind yet in this test box, and my thinking was that if anything it would be a bit "boomy" this way. Perhaps I'm wrong.

I'm thinking it must be something with the crossover. So if someone has experience with this design, I could use the help,
thanks,
Jim

[Wolf]

Re: Has anyone built this RS150 & Beston RT002a MTM before?

Hi All, I just finished assembling one of these and it seems very weak in the bass. Per Lou C. I shortened the port to 3" in length. I have a pair of the Core 2's, and one OS MTM sitting next to it, and they really kick it's backside on bass.

http://www.drmarksays.com/?p=82

Right now I have a .89 cu/ft. enclosure with internal dimensions of 6 1/2" x 12 1/2" x 19" high with a baffle width of 7 1/2". The port is 2" x 6" long. I have no damping material of any kind yet in this test box, and my thinking was that if anything it would be a bit "boomy" this way. Perhaps I'm wrong.

I'm thinking it must be something with the crossover. So if someone has experience with this design, I could use the help,
thanks,
Jim

My guess is because it was designed with Xover Pro, and didn't take all issues into account like (ie) baffle step and phase alignment.
Likely it is just an inferior design.

Later,
Wolf

[ontariomaximus]

Re: Has anyone built this RS150 & Beston RT002a MTM before?

box tuning of 40hz is WAY too low IMO.

tune the box to 55hz you'll be much happier

[nikkoluvr]

Re: Has anyone built this RS150 & Beston RT002a MTM before?

Thanks for the reply's guys; much appreciated!

Wolf, I was afraid there was a reason nobody had built it yet ("inferior design"). Looks like I need to do a couple of things. 1) learn Passive Crossover Designer so I can fix this thing. 2) build one of Lou C's RS150 MTM's so I know what the RS150's are supposed to sound like in a good MTM. Wolf, do you have a RS150 MTM design?

Ontariomax, Lou had suggested the tuning at 45HZ, are you thinking this is just too low for the RS150's, or is my box too small for that tuning?

thanks again,
nikkoluvr

[duanebro]

Re: Has anyone built this RS150 & Beston RT002a MTM before?

With just a quick glance at the xo i saw that all the inductors are small. (0.2mH) this normally means that there is no baffle step correction built in to the design. This will come through as a lack of base. To fix that you need different xo design. But you already found that out with the previous posts.

[ontariomaximus]

Re: Has anyone built this RS150 & Beston RT002a MTM before?

Thanks for the reply's guys; much appreciated!


Ontariomax, Lou had suggested the tuning at 45HZ, are you thinking this is just too low for the RS150's, or is my box too small for that tuning?

thanks again,
nikkoluvr

I have a pair of Targas - RS150 in 10.5 litres tuned to 56hz. I have no complaints about the bass. Your box size is fine. Shorten your port.

[nikkoluvr]

Re: Has anyone built this RS150 & Beston RT002a MTM before?

thanks again for all the good responses guys. I was thinking about what duanebro said while I was walking to work today, and I wondered what would happen if I added some MDF "wings" to each side of the baffle. Could I get rid of the need for BSC this way, and perhaps hear what they would sound like with a correctly designed crossover? How wide do you think the baffle would need to be?

Ontario, do you have a build on the "Targas"? I'd like to take a look at it.
thanks,
nikkoluvr

[kenny_k]

Re: Has anyone built this RS150 & Beston RT002a MTM before?

http://www.eldamar.net/audio/RS150MTM/

[Wolf]

Re: Has anyone built this RS150 & Beston RT002a MTM before?

Ontario, do you have a build on the "Targas"? I'd like to take a look at it.
thanks,
nikkoluvr

Don Radick designed and built the Targas project. Should be a build log in the Gallery section.
Later,
Wolf

[tyger23]

Re: Has anyone built this RS150 & Beston RT002a MTM before?

My Aria design uses the RS150-4 (single) in a 10.7L box with a tuning of 48hz. The bass is phenomenal out of those speakers. A few things I see when looking over that design:

1. The "BOX ALIGNMENT FOR TWO DAYTON WOOFERS" is the exact same link as the box alignment for one woofer. Also, in the description of the two-woofer alignment, it specifically shows that there's one woofer. I'd be worried that the box you built was intended for one woofer and not two.

2. The design doesn't give any real parameters for driver spacing. It says "as close as possible", but even minor changes in driver spacing or offsets can make big changes to the boundry or baffle diffraction. Also, the design gives no parameters that I see for baffle size. Changing the size of the baffle from what was designed makes it impossible to build a good speaker.

3. The crossover (as mentioned before) does not seem to have any baffle step compensation. So, basically you can add some "wings" to see if the design is performing how you want, but I personally doubt that's going to yield satisfactory results.

4. The RS150 is a great speaker. Phenomenal for it's price. However, it's got a NASTY cone breakup at 6-7KHz. This woofer absolutely needs a tank circuit, or else that breakup will hinder the overall sound. I don't see one in the current crossover.

At this point, I'd suggest the following: Post the design as you built it, not as Dr. Mark describes it. Include the box dimensions, driver spacing, driver distance from each edge, port placement and length, etc. Let us know if there's any stuffing or acoustic foam in the box and roughly how much. Post a picture of the place where these speakers will reside. Include the dimensions of the room and distances from any boundary surface (such as walls, Tv's, etc). Make sure to include the side walls and the back walls. Also, tell us how these speakers will be placed (meaning on stands, on a bookshelf, etc.). Then hopefully some of us in the community will be willing to contribute to designing a proper crossover for you and you can rescue your work so far.

I don't know Dr. Mark, and I don't want to talk disparagingly of him. However, it seems like he posted a design that he merely simulated and never built. It just doesn't seem to be a well thought-out design. Hopefully the TechTalk community can come to the rescue!

[nikkoluvr]

Re: Has anyone built this RS150 & Beston RT002a MTM before?

Hi Tyger23, I'm starting to wonder if the RS150's and the Beston are a lousy match. The Bestons need to be crossed over at 2500HZ +, and maybe the RS150's don't like to "play nice" that high. I'm starting to lean towards using some Peerless HDS drivers instead. I like the look of your Aria's so maybe I'll build a set of those with the RS150's.
thanks,
nikkoluvr

[LouC]

Re: Has anyone built this RS150 & Beston RT002a MTM before?

Hi Tyger23, I'm starting to wonder if the RS150's and the Beston are a lousy match. The Bestons need to be crossed over at 2500HZ +, and maybe the RS150's don't like to "play nice" that high. I'm starting to lean towards using some Peerless HDS drivers instead. I like the look of your Aria's so maybe I'll build a set of those with the RS150's.
thanks,
nikkoluvr

I crossed the old shielded RS-150-8ohm at 2500 in the CKillas, no problem -- as long as you can design the right notch filter.
Agreed they may not be the ultimate match up with the Beston's but certainly doable.

[nikkoluvr]

Re: Has anyone built this RS150 & Beston RT002a MTM before?

solved my problem guys. Finally built Lou's Kavernas after finding a few 832873's.
Oh yea! the problem is now "fixed"
thanks again Lou!
nikkoluvr