My RS180 MTM Design

[ROTECH]

Re: My RS180 MTM Design

Pvc

[fbov]

Re: My RS180 MTM Design

Actually, it was a test that Paul Carmody did that showed the two identical except in the are of Fs where the difference in their Q's showed up.

Jeff, you may not recall, but I had about a 1dB difference in sensitivity from RS28's purchased over a period of several years, and so several production runs. It showed up when I first did my Continuum build, as I used a new and old driver. You suggested padding one of them down, but that also changed the slope, so I used a contemporaneous pair, with silk domes to boot. Difference was gone.

So, the issue isn't getting mismatched pairs from PE, but rather mixing new/old, or using new with an older XO design. Jeff's is one of the later RS MTM designs, so I doubt you'd see an issue in this build.

Have fun,
Frank

[speedle]

Re: My RS180 MTM Design

Just to add to the fun, remember that the Natalie P uses the unshielded version of this tweeter, and seems to keep up just fine.

[coniacvsop]

Re: My RS180 MTM Design

OK, one more rookie question: Someone in some thread or another posted that this (http://www.parts-express.com/speaker...lared--260-480) is an appropriate port for this cab, but my modelling in WinISD show that as not even being close to right to getting a 1ft^3 box tuned to 40 Hz. A single 3" port somewhere between 9.5" and 9.75" looks to work ("9.66" according to WinISD), but now I'm second guessing my school-of-hard-knocks speaker skills. If anyone can give me a confirmation, I'd appreciate it. That port gives (by my work) about a 53.5 Hz tuning.

Added: Or someone could just tell me what the appropriate dimensions are (bonus points for why)! :-)

If it helps, enter the following text into Notepad, save it as a .WSD file and load that into WinISD.

>>
[Driver]
Brand=Dayton
Model=RS180-8
Manufacturer=Dayton
ProvidedBy=kraigo
DateAdded=20150807
DateModified=20150807
Qts=0.31154861916003
Znom=8
Fs=35.54549813519
Pe=0
SPL=86.268920766928
Re=6.4
Le=0
fLe=0
KLe=0
BL=7.82
Xmax=0.006
Cms=0.00112
Qms=1.22
Qes=0.41839257817385
Rms=3.27685838851422
Mms=0.0179
Sd=0.01247
Vas=0.02470560978984
Dia=0
Vd=0.00007482
no=0.0025789727626
Dd=0.12600514720775
EBP=84.9572865043019
numVC=1
Hc=0
Hg=0
SPLmax=0
SPLmaxLF=78.0447656770847
USPL=87.2428497375749
alfaVC=0
Rt=0
Ct=0
gamma=436.871508379888
Rme=9.5550625
Mpow=3.09112641281459
Mcost=0
Gloss=0.03276728653333
VCCon=1
c=343.684120962152
roo=1.20095217714683
Thick=0
Depth=0
MagDepth=0
Magnet=0
Basket=0
Outer=0
Vcd=0
DVol=0
ParState=ECNCENNNEENEECCCEECCNCCENNNCCNNNCCCCNCNNN NNNNNNCC
<<

I used that port with the tower design. It works like a champ for the larger volume, but probably not for the smaller cab. I have a build thread over in the other forum if you want to take a look.

[Mobin]

Re: My RS180 MTM Design

I would like to build these, I have some seas 27tbfcg/byeasf tweeters on hand that I would like to use. My main question is could I use the unshielded version of the rs180 woofer?
Also what kind of bracing should I do?
Would it help to use any acoustic foam in the cabinets?

[Chris Roemer]

Re: My RS180 MTM Design

Here's my suggestion for using the 27tbfcg: 3rd order HP filter (but w/value changes) PLUS an initial series resistor for level adj. :
1.5 ohm series resistor and 8uF series cap, 0.20mH shunt coil (to gnd), lastly a 15uF series cap next to Seas tweeter.

Most here on TT say that the shielded/unshielded RS180-8 woofer FR curves are so close as to be interchangeable.
The shielded woofer CAN play a bit lower (due to slight diffs. in T/S parms), however.

I'd line the vented box interior w/acoustic ("egg-carton") foam.

[Mobin]

Re: My RS180 MTM Design

Thanks for your input Chris, I was able to order the unshielded RS180 wile they are still on sale.
Now I'm trying to decide what kind of box I want to do as I just found out there are a few configurations.

[mastercraft1990]

Re: My RS180 MTM Design

I can't believe this thread has been going strong from back in 2011, pretty cool. I just finished the RS722 in black and they seem a little bright. Is that the reason that Jeff and others have taken the time to rework the crossover or were there different reasons? I'm pushing them with a Outlaw amp with a Yamaha AVR controlling things. Thanks in advance for your feedback.

[fbov]

Re: My RS180 MTM Design

... they seem a little bright. ...

I think the tweeter's sensitivity has changed a bit over the years. I've bought 7 RS28's, and I see about a 1dB shift in sensitivity. The RS722 is PE's design, so you'd think it was done early in product availability, while Jeff's is quite recent. I was building a Bagby design when I noticed the difference between a new and old tweeter... he suggested a padding resistor to even them out.

You wouldn't be the only one...

http://techtalk.parts-express.com/showthread.php?249001-Center-Channel-recommendation-for-RS722s&p=2101860#post2101860

Frank

[mastercraft1990]

Re: My RS180 MTM Design

The number of different crossovers and different price points to do the same thing is kind of mind boggling. I'm brand new to the DIY and had a Bragi kit coming from Madisound with all Seas drivers and then found that they back ordered from Denmark. I had the PE cabinets sitting there and my old Klipsch stuff had all flew out the door via Ebay, so I was soundless. That's where the 722 kits come in. After putting them together they sound good but not great. I need to wade through all the different options for the best second attempt at crossovers, money is not really a factor, want best sound.

[djg]

Re: My RS180 MTM Design

Somewhat dated info, I would do Jeff Bagby version as it is the latest, designed with newer software and some talent.

http://www.rjbaudio.com/RS180MTM/rs180-rs28-mtm.html

[mastercraft1990]

Re: My RS180 MTM Design

Does anyone have a picture of a completed Bagby MTM crossover?

[01-0077]

Re: My RS180 MTM Design

Here's one http://techtalk.parts-express.com/sh...M-Towers/page2 (see post#34) although this has been modified to suit a different tweeter (see post#1 of the thread).

Another in this thread (see post#12) http://techtalk.parts-express.com/sh...80-L-C-R-Build

[bekim]

If you build it, as always, let me know what you think.
Jeff B.

Hi Jeff, I'm planning to build these MTM's and use your cross-over. Dr. K mentions "A larger “extended bass” version of the tower would be approximately 1.7 cu. ft., tuned to 35 Hz via a 3" x 6-1/2" port. Again using 3/4" MDF, this cabinet would measure roughly 9" wide, 40" tall, and 12" deep. Note for these larger cabinets, a 3" diameter port is preferred, and a 4" port is an option if you are going to be running the speakers at high power. "

I'm wondering if you'd advise using your crossover in this larger cabinet?

[Jeff B.]

Hi Jeff, I'm planning to build these MTM's and use your cross-over. Dr. K mentions "A larger “extended bass” version of the tower would be approximately 1.7 cu. ft., tuned to 35 Hz via a 3" x 6-1/2" port. Again using 3/4" MDF, this cabinet would measure roughly 9" wide, 40" tall, and 12" deep. Note for these larger cabinets, a 3" diameter port is preferred, and a 4" port is an option if you are going to be running the speakers at high power. "

I'm wondering if you'd advise using your crossover in this larger cabinet?

it should work fine