RS28a/RS225 MT

[kgveteran]

What is the location of the drivers on the baffle.It looks like the tweeter is off center ?
http://www.audioheuristics.org/proje...ence_rs225.htm

The XO's are between 100.00 and 118.00 each using dayton caps Jzanten coils and 10watt resistors

I'm going to have my cabinet guy make em' out of 1" MDF w/one brace.

[tokyofist]

I forget what driver spacing I used, but I just guestimated it from the picture on Mark's page. Obviously not the best option because of the oblique angle, but the finished speaker sounds pretty darn good. I can get you the figures I used tomorrow evening - I had to relocate my woodshop to my mother's house (ah, apartment living :roll: )

[JonP]

I'm sure Mark will chime in momentarily....

Have had my eye on these for a while.. and have the beginnings of a project related to them on the cold back burner.. (time to crank a knob!)

With a 1200hz crossover freq, the driver spacing dosen't need to be very tight, so that's flexable. You could always put the baffle and driver dimensions in BDS, and play around till you get the flattest positioning. I forget what I came up with, a tweeter offset of about .75-1.0", IIRC...

[Mark K]

What is the location of the drivers on the baffle.It looks like the tweeter is off center ?
http://www.audioheuristics.org/proje...ence_rs225.htm

The XO's are between 100.00 and 118.00 each using dayton caps Jzanten coils and 10watt resistors

I'm going to have my cabinet guy make em' out of 1" MDF w/one brace.

Hi guys,

The cabinet is a standard 3/4 PE cab
The tweeter centerline is 3" down from the top edge and the tweeter is offset 3/4 of an inch from the centerline.
The woofer is on center, with the centerline of the woofer 6" from the bottom edge.

I've been meaning to generate a drawing, but, well.

Let me know if that's not clear.

mark

PS- If you haven't read it, the speakers should be placed with the tweeters towards "the outside," i.e. the speakers should be placed with the tweeters offset outwards. This is against the general rule of thumb but is what the measurements suggest is correct.

[kgveteran]

Hey Mark,
Great design.These will be my rear/side surrounds. I'll use a PEQ to get them right as they will be placed close to each side wall.I don't want to mess with a great XO design should I move them later.

Thanx for the measurements. KG

[kgveteran]

Sorry for this Mark, ops: which driver is which D1 and D2.I thought that in line caps was 28a and inline coils were 225 ?

[Mark K]

Sorry for this Mark, ops: which driver is which D1 and D2.I thought that in line caps was 28a and inline coils were 225 ?

right
D1 is the woofer
D2 is the tweeter

not a problem. You can actually change the icon, but I didn't get to it.

mark

[kgveteran]

Thanx Mark.

[kgveteran]

Hey Mark,

What would you say the final impedence is ? Also the final sensitivity ? I have been looking at amps and I have an eye on a three channel 200watt.I'm sure that would give me loads of headroom at my usual 85-90db movie watching experience.

KG

[kgveteran]

B&K sells a three channel amp that is rated for 140X3.It bumps up a bit to 180watts into 4 ohms.you guys think this would do for the rear surrounds.My usual listening is at 85bd-90db.I'm sure they would sound fine, I like headroom though.

It is the B&K 3140.

[Mark K]

B&K sells a three channel amp that is rated for 140X3.It bumps up a bit to 180X3@4ohms.Do you guys think this would do for the rear surrounds.My usual listening is at 85bd-90db.I'm sure they would sound fine, I like headroom though.

It is the B&K 3140.

This is more than fine. Say they are 84dB/2.83v. If it can drive 4 ohms at 180, that would be, oversimplifying, ~150w is 105dB.

[kgveteran]

This is more than fine. Say they are 84dB/2.83v. If it can drive 4 ohms at 180, that would be, oversimplifying, ~150w is 105dB.

After the first of the year I'll start looking around.Thanx.

105db would give me the headroom.The surrounds are about 5' from my head on either side of my sofa.

[kgveteran]

After looking around the room and building little cardboard speakers to see the fit...they are too big(10"w X17"h X 15" d).This is about .8cu ft.

This is my thought.....As I did with the three mains.I cut the cabinets depth to make them smaller.What are your thoughts on cutting down the cabinets depth to fit them for wall mounting.My XO is 100hz at the processor.Can you guys run some box volumes to see where i'm at with this.To tune them around 80hz acoustic 12db/oct roll off sealed would fit me fine.Other than short changing the frequencie response, should I be concerned about any other effect of a smaller cabinet, other than wall mounting them on some nice omni mounts.

I'm also going to upgrade to 7.1 from 6.1 . I'll be picking up two Behringer 500a's for the four channel surround duties.

[dlneubec]

Hey KG,

If you are going to cross them at 100Hz, why not just use the RS180 instead of the RS225? They can do that in very small sealed boxes around 7-8 liters.

[Jonasz]

If you cut the volume in half maybe a variovent would be helpful to lessen any possible damages to the respons?

[kgveteran]

Hey KG,

If you are going to cross them at 100Hz, why not just use the RS180 instead of the RS225? They can do that in very small sealed boxes around 7-8 liters.

I thought that the 225's would handle power a little better than the 180's.

I know that this isn't a XO issue when it comes to sealed boxes.The box depth is really 12.5" not 15".

What would the response be if the outside depth was around 8". That would be around .4 cu. ft. Does anything happen to the upper octaves with a smaller cabinet or does this become a "bass only" issue ?

[kgveteran]

Hey KG,

If you are going to cross them at 100Hz, why not just use the RS180 instead of the RS225? They can do that in very small sealed boxes around 7-8 liters.

I already have the RS225's purchased

[Mark K]

Using a box volume of 14 liters gives a Q o 0.78 and a slight bump of ~.1 dB at 140 Hz. Practically speaking I think you could get away with this. I would try to stick to around 0.5 cu ft or so at least.

[kgveteran]

Using a box volume of 14 liters gives a Q o 0.78 and a slight bump of ~.1 dB at 140 Hz. Practically speaking I think you could get away with this. I would try to stick to around 0.5 cu ft or so at least.

Thanx Mark. I have PEQ's for all six channels.As long as thats the predicted rise,I can always tweak the sound.Just out of curiosity, what's the new rolloff with that small of an enclosure ?

I'll draw up some plans for the cabinet man.


Do you feel that my thinking is correct, that the 225's would handle demanding SPL's better than the 180 ? I'm not sure what the XO frequency is for the 28a/180.

Thanx again...KG

[Paul H]

...

Do you feel that my thinking is correct, that the 225's would handle demanding SPL's better than the 180 ? I'm not sure what the XO frequency is for the 28a/180.

Thanx again...KG

Yes, you're definitely going to get higher spl's from the 225. The 225's cone has almost but not quite as much area as two 180's, and slightly higher xmax - you're going to get similar output from one 225 as a 180 mtm.

The crossover for Jon M's MT 28a/180 is around 1700-1800 Hz.

[kgveteran]

cabinets done

The cabinet guy finished my four surround speakers today.I opted to make the brace up higher and kinda cut the cabinet in half.Notice they are only 8" deep.They will fit perfect on the wall with smallish mounts.

I ordered two Behringer A500's yesterday.Found a guy to do them for 179.00 shipped each .They will power these.

[kgveteran]

The dry fit

Who can refuse a dry fit. I could just imagine these with the 15" depth. Pretty damn stout !

Well, I've got the BOM for the XO parts, but not quite the 450.00 for all four.Soon enough though.....

KG

[oxcartdriver]

Kgveteran, are you happy with the sound? Did you have to EQ to get the desired response?

Why the comment on the 15" depth? Was there an alternative cabinet with this depth?

Sorry for all the questions, but I'm torn between the RS28/RS225 and RS28/RS180 MT designs.

[jonathanb3478]

Kgveteran, are you happy with the sound? Did you have to EQ to get the desired response?

Why the comment on the 15" depth? Was there an alternative cabinet with this depth?

Sorry for all the questions, but I'm torn between the RS28/RS225 and RS28/RS180 MT designs.

He does not have the crossover components, yet. He knows what to get (he has the BOM), but not the money (~$450), as he points out.

I have seen a completed pair of the design he was working from, in person. It is intended for use in a Parts Express .75cuft bookshelf enclosure, and that is what the one I saw was in. The enclosures he has built are not as deep as the PE enclosures. He is making surrounds, so he sacraficed some bass extension for a smaller profile by DIYing his own enclosures with less depth (and thus volume, obviously).

I can attest to the fact that a completed pair look pretty big for "bookshelf" speakers, at least when they are put in the intended PE cabinet. I am accustomed to some Infinity SM82 (the old party speaker 2-way with an 8" woofer), as my mom uses a pair of those on the receiver connected to her TV. She has for the last decade-and-a-half. ops:

No 2-way bookshelf really looks big, once you are used to those Infinities.

[kgveteran]

Jonathanb3478,

Couldn't have said it better myself.Yes, I will have to tweak it up a bit once in place.The depth is 8".Internal volume about.5cubes.

I think the smaller cabinet will help with the reinforcement it will get from the back wall.We'll see though.



KG

[kgveteran]

Kgveteran, are you happy with the sound? Did you have to EQ to get the desired response?

Why the comment on the 15" depth? Was there an alternative cabinet with this depth?

Sorry for all the questions, but I'm torn between the RS28/RS225 and RS28/RS180 MT designs.

What duties will they have ?

[oxcartdriver]

I was looking at this as mains in a second zone, and/or surrounds in a home theater. Both applications would be mounted on stands, not mounted on the wall.

[kgveteran]

I was looking at this as mains in a second zone, and/or surrounds in a home theater. Both applications would be mounted on stands, not mounted on the wall.

Then you would have no problem with the original cabinet depth of 15".They would seem to be great as mains with that big ol' 8" woofer.

KG

[JonP]

Not sure about this 15" deep cab thing... I thought these were in the PE .75 cu ft 2way cabs, and those are 12.5" deep. Same box as the Modula MT...

[kgveteran]

Not sure about this 15" deep cab thing... I thought these were in the PE .75 cu ft 2way cabs, and those are 12.5" deep. Same box as the Modula MT...

You are correct.Here are the specs off the web site.

Cabinet Finish: Piano Black Gloss
External Dimensions: 17" H x 10" W x 12.5" D
Internal Dimensions: 15.5" H x 8.5" W x 10.75" D
Internal Volume*: .82 cu. ft.

[kgveteran]

If you cut the volume in half maybe a variovent would be helpful to lessen any possible damages to the respons?

Did we ever address this device and whether it would be needed ?

[Gir]

Not sure about this 15" deep cab thing... I thought these were in the PE .75 cu ft 2way cabs, and those are 12.5" deep. Same box as the Modula MT...

I basically mimicked their design, except mine is 13" deep since I have a 1 1/2" front baffle instead of a 1" thick baffle. I'll be using mine as mains along with a big 'ol sonosub =D

BTW, the internal volume is roughly .8 cubic feet (I forget how big the holes are in the bracing), and with the drivers in it should be around .75 cubic feet, same as the PE one (which is really .82 cubic feet before driver placement).

[kgveteran]

shielded pair/unshielded pair

OK, the 28a (unshielded) is out of stock until mid Feb.Is there a big difference between shielded and unshielded acoustically.I have a pair of unshielded, should I purchase the shielded pair and be done with it?

[Ecir38]

Is there a big difference between shielded and unshielded acoustically.

I would think the crossover would be differant but i could be wrong. I would like to know this too as far as if there would be a acoustical differance between the two.

[Paul H]

I would think the crossover would be differant but i could be wrong. I would like to know this too as far as if there would be a acoustical differance between the two.

They're different - the shielded version has a higher resonant frequency and a dip in response between 1000 and 2000Hz compared to the shielded.

I'm still tinkering with a model of MT with the RS180 and shielded RS28. I've measured and checked, and have replaced one inductor with one twice its size, and adjusted resistors on the tweeter to get closer to a flat response.

It's starting to sound pretty good, but the point is it required changes as compared to the crossover designed for the unshielded version.

[cgr]

Is there a big difference between shielded and unshielded acoustically.

I bought the shielded ones when they were on sale last year without realizing most designs use the unshielded. I found a couple of references to people building the modula mt with the unshielded on it's thread. I bought the unshielded in the dec sale.

When I built my modula mt I tried swapping for shielded for unshielded and couldn't hear any difference; but that isn't to say that someone else wouldn't or that if I played other source material I would hear something.

I ended up using the unshielded versions and plan to build a set of rs125 or rs150 surrounds that are designed with the shielded rs28.

[kgveteran]

One set done !

Here are the finished 28a-225's....the diet version (8" thin) . Talk about blending in..

I just got done watching "Cars". Can't wait to get the back pair done.EX was meant to be heard like this.I've got my Rat Shack Minimus-7's as back duty for now.

[kano32]

Nice job!

How much money do you have invested in foam/room treatment. Looks like alot of work. Can you take a couple photos of the entire wall.

[JoshK]

When you finish up with that other pair you can get started on mine.

[Ecir38]

Nice job!

How much money do you have invested in foam/room treatment. Looks like alot of work. Can you take a couple photos of the entire wall.

nice, i would like to see some more pics too.

[kgveteran]

It's just that 2" blue foam insulation cut up with a foam cutter and painted grey.The panels are OC 703 board wrapped in roma wool.More time than money.

[kgveteran]

When you finish up with that other pair you can get started on mine.

Where do I ship em' to ?

[kingpin]

Hey Mr. KG

I love the way your finish looks on all of your speakers.
What is the product you use to paint them.
Is it just grey paint or something else.
It looks like it has some texture to it.

Mike

[kgveteran]

Hey Mr. KG

I love the way your finish looks on all of your speakers.
What is the product you use to paint them.
Is it just grey paint or something else.
It looks like it has some texture to it.

Mike

The MDF is rounded over and I paint on latex satin with a roller.I do three coats, then sand with 150grit.Then two more coats.

I use those little rollers, only about an inch diameter.They cover pretty good.

Wash them first(the rollers) and let them dry.It eliminates lint from the roller.

[kingpin]

What is the color called.