My RS180 MTM Design

[jackm11]

Re: My RS180 MTM Design

Jeff,
I have the MTM speakers running(using the NPE too). Thanks Jeff.
They do sound clean, smooth and pleasant.

Just curious, how much baffle step comp did you use in the design?

[Jeff B.]

Re: My RS180 MTM Design

Jeff,
I have the MTM speakers running(using the NPE too). Thanks Jeff.
They do sound clean, smooth and pleasant.

Just curious, how much baffle step comp did you use in the design?

I guess about 6dB based on the lowpass transfer function plot which shows a 6dB transition between 1khz and 100Hz. However, I don't tend to think in these terms when I design. My measurements are a composite of 1 meter on the stands and near field spliced, then I target a flat response. I also measure using an RTA with pink noise in the listening position to check the overall balance. I usually never think in terms of how much baffle step compensation I am applying while I am doing this. I am only interested in the final result.

[tktran]

Re: My RS180 MTM Design

Hi Jeff,
Could you clarify on the baffle layout (driver positions)?

Regards,
Thanh

[Jeff B.]

Re: My RS180 MTM Design

Hi Jeff,
Could you clarify on the baffle layout (driver positions)?

Regards,
Thanh

Not exactly, since I don't have this speaker with me. However, I used the precut cabinet and baffle for this kit:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=302-976

It is a basic MTM layout with the tweeter offset about 1/2" on the baffle.

[rtkelly]

Re: My RS180 MTM Design

Jeff,
I realize it has been some time since you heard these speakers, however how would you rate these relative to your Picolos (sp)?

Rollie

[Ed H]

Re: My RS180 MTM Design

Has anyone modeled Jeff's XO with the non-shielded tweeter and 13uF cap as he suggested?

Edit: How does the Seas tweeter stand-up against the Dayton? I've only heard great things of the Dayton.

[Applesauce]

Re: My RS180 MTM Design

Has anyone modeled Jeff's XO with the non-shielded tweeter and 13uF cap as he suggested?

I can't offer anything as far as that goes, but I thought I'd add: Solen still has a whopping two RS28AS-4 in stock. I would guess that's the last of them...

I'm more on the fence now about using the shielded or unshielded RS180. I've seen mixed reports about sensitivity, in particular, with Dayton claiming the complete opposite of Paul Carmody's test; and some variability in box requirements for the shielded vs. unshielded, because of differing Qts.

[mike price]

Re: My RS180 MTM Design

I was curious if anyone had tried this with the RS28-F as of yet? I have all the drivers on hand to build it with the RS28-F , and most of the crossover components , I was just wondering if anyone tried the different tweeter with the slightly larger cap , and what the results were like.

[Jeff B.]

Re: My RS180 MTM Design

I was curious if anyone had tried this with the RS28-F as of yet? I have all the drivers on hand to build it with the RS28-F , and most of the crossover components , I was just wondering if anyone tried the different tweeter with the slightly larger cap , and what the results were like.

Based on what I have seen recently, maybe someone should just begin with the original crossover and adjust from there if needed. give it a try and let us know how it works out.

Jeff

[mike price]

Re: My RS180 MTM Design

Thanks for replying Jeff , I believe I may do just that , and I can always add to that 10uf cap value if there is a noticeable "hole" between the drivers. I am quite impressed with this design , and a huge fan of simplistic crossover designs , that coupled with the fact that I have the drivers and many of the crossover components on hand makes this a no brainer as my next project. I will be fabricating my own cabinets for these , but will definitely stick to the 9" baffle width and original driver layout/spacing. I should be getting started this weekend , and will certainly let you know how it turns out. Is there anything to be gained by increasing the cabinet volume to say 1.25 or 1.5 cubic feet? Or is 1 cubic foot pretty much optimum volume?

[ontariomaximus]

Re: My RS180 MTM Design

Jeff, any chance of a crossover redesign with two RS180-4 in series, vs the 2 RS180-8's in parallel? I happen to have 4 of the RS180-4 version AND I need a pair of studio monitors.

your consideration appreciated...

[Jeff B.]

Re: My RS180 MTM Design

Jeff, any chance of a crossover redesign with two RS180-4 in series, vs the 2 RS180-8's in parallel? I happen to have 4 of the RS180-4 version AND I need a pair of studio monitors.

your consideration appreciated...

Not much chance for me, at least not for a while - just too many irons in the fire right now. You can scale the values for twice the load and go from there......

Then you'll need to add an L-pad to the tweeter to match the new level too.

[ontariomaximus]

Re: My RS180 MTM Design

So the 1.2mh, 20uf, and .025mh components in the woofer section would be 2.4mh, 40uf and .05mh, right?

And can I just add 3 ohms in front of the tweeter crossover to pad the level a bit, without changing the other values?

Perhaps I may even use the Seas TBFC instead as it is SA (still available). Maybe the Usher 9950, any other candidates spring to mind?

[Jeff B.]

Re: My RS180 MTM Design

So the 1.2mh, 20uf, and .025mh components in the woofer section would be 2.4mh, 40uf and .05mh, right?

And can I just add 3 ohms in front of the tweeter crossover to pad the level a bit, without changing the other values?

Perhaps I may even use the Seas TBFC instead as it is SA (still available). Maybe the Usher 9950, any other candidates spring to mind?

No, the cap would scale to 10uf. However, I would need to see if the Q of notch would be right with those values. Let me see if I can take a closer look at my simulation tomorrow.

Jeff

[PunkSweeper]

Re: My RS180 MTM Design

Did I miss something or are these strikingly similar to Dr. K't MTMs?

http://www.parts-express.com/projectshowcase/indexn.cfm?project=DrKMTM