# DIY MTM Speakers in bookshelves - Choice Questions



## ctf (Sep 25, 2011)

Hello,

I have been reading posts here for a while and have learned a ton of valuable information.
I built speakers a long time ago, and was very happy with the results, I would like to do that again.

I understand that speakers are usually better placed away from the back and side walls.
Unfortunately, my current setup (and to help with the WAF) does not allow for that, and I have to put the front and center channels into built-in cabinets.
I have attached a picture so that this is all clearer.

The TV is a 65" JVC DILA TV (12" deep) and the speakers around it are Vandersteen 2CE.
There is also, under the TV, a VCC Vandersteen center channel.

The spaces where the Vandersteen front are currently located are 47"H x 18"W and 12" Deep.
I cannot install the speakers into the next bookshelves, as we have books coming to line these up.
(Some books show already on the bottom of each side)

I would like to build speakers that can mostly fill the space on each side of the TV, and sound great.
The Vandersteen are great speakers, but cannot be used in these conditions therefore I will sell them.

I am thinking MTM designs would be good and allow for some great speakers with ample power.
I usually like to listen fairly loud (neighbors are not an issue since this is a house).
This will be used to listen to music (all sorts) and as a home theater speaker set. (5.1)

Last but not least, I will have to redo a center channel.
I can put it on the bottom, or immediately above the TV. (Vertical space is 6")

Can someone please help me understand which designs would work well for these conditions?
The speakers will be against the back of the bookshelves, and will be "enclosed" on each side as well.
I am not sure which speakers will work best in these conditions.

I truly appreciate all the expertise that is available on this forum and look forward to hearing your suggestions.

Thank you.
Arno


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## lcaillo (May 2, 2006)

It is a shame to have to sell the Vs as they are fine speakers. The placement will limit what you can do, but I am sure you will find some good advice here.


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## ctf (Sep 25, 2011)

I agree.
I wish I could keep them as I have all Vandersteen including the surrounds, but this placement really does not do them justice...

I feel that I will be able to build speakers that will sound better than these in that location.

Cordially,
Arno


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## GranteedEV (Aug 8, 2010)

the #1 and #2 issues with cabinet mounting are

1) Baffle Step _Over_compensation
2) Diffraction artifacts.


There won't be much you can do about the increase diffraction. A waveguide loaded tweeter will help to some extent but ultimately diffraction is what it is. A perfect speaker would be 3-4ft away from any objects, and a round, probably teardrop curve towards the back. Most of us deal with some level of diffraction in our speakers anyways since they don't really fit the above criteria and for WAF type reasonings. Just know that if the speaker sounds harsh or bright, it may be because of cabinet diffraction, not the design you picked. If you can modify the cabinet at all, aggressively rounding over any sharp edges near the speakers could have a positive effect.

The baffle step issue can be rectified though. If it's going to be in a cabinet, it's probably going to not need any BSC (or only 1db or so if it does... nothing to fret over). So the goal will be to pick a design modified for zero baffle step compensation. The positive side to that is that it will reduce the load on your amplifier to drive the speakers, at least.

The first no-BSC MTM I thought of is the Zaph Audio ZA5.3iw - scroll down near the bottom to find it

http://www.zaphaudio.com/za5/

The tweeter used is an excellent value, and the midwoofer used, the ZA14W08 is just outstanding. In an in-wall (er in-cabinet) MTM box (sealed?) crossed over to a subwoofer, it should really impress you with its clarity and low distortion. It's a great driver.

The center will be difficult though. I've never been big on MTM center channels. That said, the ZA5.3C center channel also in the link above, also has reduced baffle step compensation.


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## ctf (Sep 25, 2011)

The Zaph kits seem interesting.
I am concerned however that the woofers are a bit small.
I have 8 and 10" woofers in the Vs, and I am used to a "big" sound.
Furthermore, I tend to listen fairly loud.

Would these kits disappoint in that respect?

Thank you.
Arno


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## GranteedEV (Aug 8, 2010)

ctf said:


> The Zaph kits seem interesting.
> I am concerned however that the woofers are a bit small.
> I have 8 and 10" woofers in the Vs, and I am used to a "big" sound.
> Furthermore, I tend to listen fairly loud.
> ...


You will need to cross it over to a pair of good subwoofers at 100hz (assuming you're sealing it). That will take the strain away from the woofer from moving too much to produce output. 

Bare in mind that if you're mounting so close to a wall, you basically gain (more specifically, "Don't Lose") an extra 3 to 4db of sensitivity. The result is that where 100db might be more like 104db as seen by the driver when far away from a wall, 100db is 100db to the driver when in the wall. That difference is pretty significant.

A pair of these midwoofers can produce about 107db in 2pi space based on their xmax, which I suspect is very accurately given. You would need an amp capable of clean 300w dynamic bursts into 4 ohms to do so A THX subwoofer crossover at 100hz means the mains will be 6db down below listening level. So if you cross over at 100hz (you will want quality subwoofers that can play up high and not be localized) that means you can hit a max SPL of about 113db. AT about 10ft away that's around 103db.

A bit optimistic in real world conditions, but around 100db ain't too shabby IMO. The key is the subwoofer crossover at 100hz. You'd lose about 4db of max output power if you crossed at 80hz, and a poor integration either way (these drivers are about 6db down at 80hz which means with a typical receiver crossover they'd be 9db down while the sub is only 6db down)

The ZA5.5tt tower with four 5.25" drivers probably has the same sensitivity 4-5ft away from a wall that the the ZA5.3 does in a wall. I'd personally prefer the tall tower for the higher max output BUT near a wall it will require some external EQ as below around 6-700hz it will have a slow rise in output if mounted in a wall. This is because the top and bottom woofers are used specifically for baffle step compensation, which shouldn't be compensated for if there is no baffle step (IE in a wall)


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## ctf (Sep 25, 2011)

I will definitely do some new subs.
I currently have an old (but efficient) Velodyne 15" servo.
Any good suggestions?
I would like to put the speaker boxes behind the couch, against the back wall if this is not too bad.

I will need to look more into these ZA5 then.
It seems that they may work well after all.

Can I make a speaker box wider, but shallower and conserve the same settings otherwise?
I have 18" avallable on each side of the TV.
While I may not want to go all the way, 12 to 14" would be nice.
I also have 47" in height, which could be used if needed to compensate for the shallower box.

Thank you,
Arno


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## GranteedEV (Aug 8, 2010)

ctf said:


> Can I make a speaker box wider, but shallower and conserve the same settings otherwise?
> 
> 
> > While you'll have _some_ leeway, changing the baffle width can have adverse affects. Less so for a minimal BSC design than for a high BSC design, though.


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## Jstslamd (Nov 30, 2010)

GranteedEV 

Do you think another option he may want to look at may be something like the Dayton rs722 mtm kits ?


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## GranteedEV (Aug 8, 2010)

Depends how much baffle step compensation is built into them. 

The average speaker has 3 to 5db of BSC.

A speaker for his application really wants maybe 1db, 2db at most, and 0db is probably perfectly acceptable.


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## ctf (Sep 25, 2011)

The Dayton kit seems nice.

Is there a way to see if a crossover has any BSC built-in from schematics?
I am not familiar with crossover design unfortunately.
Thank you.
Arno


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## GranteedEV (Aug 8, 2010)

ctf said:


> The Dayton kit seems nice.
> 
> Is there a way to see if a crossover has any BSC built-in from schematics?
> I am not familiar with crossover design unfortunately.
> ...


Pretty much every good crossover for a box speaker will have BSC built in. Some 3db, some 4db, some 5db, some a full 6db. If a crossover doesn't have much BSC, it's either intented for an in wall or in cabinet install, or the designer was incompetent.


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## Owen Bartley (Oct 18, 2006)

You will definitely have some obstacles to overcome by building (or placing) inside a cabinet, as mentioned above. There are ways to get around this though, at least to an extent, and to build a speaker that will sound much better in that location.

Check out Kyle's thread here for some possible inspiration. He built the Natalie P MTM with the BSC version of the crossover. There are a few versions of this crossover I think, and I can't say which one would be best for you, but I bet someone can help you with that. The Natalie P speakers were generally very well received and I'm thinking about building some myself. There are a few CCs that have been used with them, including the CJD MTM RS150, Modula MTM CC, or the Modula NeoD CC. You might have to play with the sizes to get them to fit where you want, but I think they're worth a look.


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## fusseli (May 1, 2007)

ctf said:


> The Dayton kit seems nice.
> 
> Is there a way to see if a crossover has any BSC built-in from schematics?
> I am not familiar with crossover design unfortunately.
> ...


It depends on how the BSC is implemented. A good DIY design should explicitly say how much BSC is present and/or have a couple Xover versions for various applications. Quite often a desired level of BSC is integrated into the rest of the filters in the Xover and you can't tell by looking at the components. The less accurate way to do BSC is with a series shelving RL filter prior to the rest of the Xover, but that doesn't acheive as flat of an FR since the rest of the system is not going to have a flat impedance about 99% of the time.

Hope that helps.


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## ctf (Sep 25, 2011)

> Check out Kyle's thread here


This is really awesome, thank you for this link.
It is very similar with what I would like to do.

I will need to check this out more in details.

Arno


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## ctf (Sep 25, 2011)

fusseli said:


> It depends on how the BSC is implemented. A good DIY design should explicitly say how much BSC is present and/or have a couple Xover versions for various applications. Quite often a desired level of BSC is integrated into the rest of the filters in the Xover and you can't tell by looking at the components. The less accurate way to do BSC is with a series shelving RL filter prior to the rest of the Xover, but that doesn't acheive as flat of an FR since the rest of the system is not going to have a flat impedance about 99% of the time.
> Hope that helps.


I think that I need to stay with proven designs, which have the right crossovers for my application.
This will prevent issues down the line. 
Thank you.
Arno


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