Newbie wants to build Modula MT. Help needed

[gee_boi]

Hello everyone,
I really want to get into the DIY home audio world as I think I'm kind of growing out of the whole car audio thing now. I do have a bit of an electrical engineering background (I studied computer engineering) so I understand the basics, but am still learning a lot about the audio stuff.

For my first (and hopefully not my last) foray into speaker building I thought I would go with a tried and tested design and thought the Modula MT would be a good start.

The problem is, I don't have enough room for them . I have a small room with an entertainment unit, not enough space on either side of it for them so I'd have to put them in it. Now, what I'd like to know is should I try to modify the design (baffle dimensions) or just go with another design altogether?

The space I have is 13"W x 13"H x 15"D (and is 1.5" from the wall in the back). I was thinking maybe I could change the baffle to 12.5"H x 10"W and with a depth of 13.8" I could still achieve the req'd .75 cu ft. I assume I would have to modify the crossover, but would it be worthwhile (i.e. would they still sound good)?

Some more info about the room:
-Speakers will be ~42" apart with TV between, about 30" from floor
-Seating is ~6' from speakers
-Will eventually be used with a small subwoofer (which I plan to build myself also)

I guess what I really want to know is should I scrap the Modula MT idea?
(I have a feeling you're all going to say it's not a good scenario for them)

My only other option is a VERY narrow floorstander (I only have about 8" on either side of the wall unit).

Here's a pic of the wall unit. I plan to put the speakers on either side of the TV. (I will try and upload some pictures of the room when I get a chance).

[ThomasW]

The worst possible place for speaker is immediately beside a TV.

Why?

The high frequencies bounce off the glass and are reflected forward the listener. These out of phase reflected sounds combine with the direct sound coming from the speaker and cancel. This is called comb filtering.

And unfortunately the worst possible acoustic shape for a room is a cube, second worst possible shape is a square.

So before building any speaker you need to figure out how much space you can dedicate to fairly large bass traps and other acoustic room treatments. Note that this will include traps mounted on the ceiling.

[HareBrained]

Sheesh, the guy's asking about speakers and you tell him to nuke his house. 8O

I think we all have to live with compromises in our environments. Most room treatments cost more then replacing the TV stand with something more audio friendly. And most room treatments have low WAF.

To the OP, if you're interested in building a set (and not designing), look for another design. Zaphaudio has a low baffle-step option for the ZMB4 that may suit your needs. Baffle-step diffraction is the an affect caused by the sound going to from the baffle (two dimensions) to free air (three-demensions). When a speaker is placed close to other objects (like TVs), the degree of BSD is decreased. As most speakers are designed for free space placement, they have a "full" baffle-step compensation included. If you build the ZMB4, you will need/want a subwoofer.

There are many other small speaker designs to be had. Finding one to fit your space and wallet should be simple.

[cotdt]

As ThomasW mentioned, there is going to have to be a compromise. However, there are some things that you can modify in the ModulaMT design to suit your needs.

It's essential that you keep ModulaMT's baffle width, but you could reduce the height, and make it sealed instead of ported (sealed works better with smaller enclosures). Essentially this only affects the low end, and keeps the other qualities of the ModulaMT intact.

You might want to reduce the baffle step compensation a little, or you might not. Try it out first.

[ThomasW]

Sheesh, the guy's asking about speakers and you tell him to nuke his house. 8O

The idea was to inform him there are challenges to face more problematic than a slightly wrong sized box. And that he might want to deal with those first then decide which variation of the box to build.

[kevinp.]

If you're keeping the smalled measurement of the baffle the same (the width, usually) there is no need to rework the crossover. Unless you're putting the speakers on a shelf... in which case you might want to try a reduced BSC xover, Or a reciever with pretty good room correction software like Audyssey.

[gee_boi]

Thanks for the suggestions guys.

I had a look at the "ZBM4" from Zaph and I agree that those might be better suited for what I need right now. Also, being my first attempt at speaker building (apart from car audio stuff), it might be a better idea to start with a smaller project.

I had been looking at the Modula's for a long time and kind of had my heart set on them, but I just don't have the room for them right now (~600 sq ft. condo), maybe when I move into a bigger place...

[Mudjock]

I would suggest you also consider an RS150-based MT. These can work in 0.25 to 0.5 cu. ft. 9nternal volume and would be a better match for the Modula MT down the road (use them as surrounds). You can check the Missions Accomplished section for more info - there are several design options.

[gee_boi]

Thanks for the suggestion Mdjock, sounds like a good idea.

I will look into the RS150 as well. I don't remember seeing any well document projects using them the first time I looked, but I'll definitely take another look.

[Undefinition]

Thanks for the suggestion Mdjock, sounds like a good idea.

I will look into the RS150 as well. I don't remember seeing any well document projects using them the first time I looked, but I'll definitely take another look.

Yeah, Scott's got some good designs for that woofer (RS150). I did one small sealed design with it that might be what you're looking for as well.

http://undefinition.googlepages.com/diy-thegirlfromipanema

I also have one narrow floorstander design I just finished, with a few more on the way. But I have to ask: would you be placing said floorstanders in corners?

http://undefinition.googlepages.com/diy-vic-20

[Mudjock]

RS150 MT Thread

This is the thread you were referring to. Also, if you search my previous posts, you will come upon designs for the RS150 using either the Seas H1212 or the Bohlender Graebener Neo3PDR. These have both been well received at DIY events and built by others, so I can confidently recommend either. CJD has designs using the Seas 27 TDFC or Dayton RS28A (not sure about with or without ferrofluid, though). As Thomas notes, these designs are not as completely documented as some others, but we can help you through the process if you choose to go that route. Paul (Undefinition) also does quality work, so his design might be an option as he appears to have been going for a near-wall solution. Mine should work for that also as long as you stuff the rear port or build it sealed.

[JonP]

Thanks for the suggestions guys.

I had a look at the "ZBM4" from Zaph and I agree that those might be better suited for what I need right now. Also, being my first attempt at speaker building (apart from car audio stuff), it might be a better idea to start with a smaller project.

I had been looking at the Modula's for a long time and kind of had my heart set on them, but I just don't have the room for them right now (~600 sq ft. condo), maybe when I move into a bigger place...

I can say from experience that the ZBM4's are pretty eye opening. (I actually have a pair of Modula MT's as well...) The ZBM4's are much smaller, of course. That might help with doing what they or any other speaker really need for best performance, i.e. putting them on stands a bit out and away from that TV/ent. center.

The caveats for the '4 are.. lower overall volume capability... but they do get fairly loud, and you have a smaller room... and greater need to be crossed over to a sub or two.

I would also agree that the RS150 based design would have more range, and should be able to go louder, if you need that.

Either will probably fit on the little surround stands that PE has, (the 4's of course do) they're pretty nice for $40... I like those a lot.