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Here are the Schlafmutze Mini MT’s! 
This speaker design is still in progress. As things get closer to the end I will update this thread and put all the relevant, permanent details into these first few posts. For now here is the start of the project and where the progress is at, currently.
Introduction and Design Goals:
This project came about from my wanting to have some very nice speakers in my office, on the shelves above my desks. So the cabinets will have to be as small as possible and yet have enough bass to reach a sub. Also I favor designs with low distortion.
The major design goals here are:
-A cabinet size as small as possible
-Plays down to 80 Hz for good crossover to a sub.
-Low distortion
Working within those constraints we will come up with the best speaker possible, considering the cabinet design, driver choice, and crossover design. I will be placing these speakers up against a wall (on the shelves) so one crossover will likely have decreased no baffle step compensation (BSC). But I will also provide a second crossover option in case anyone wants to place the speakers on a stand, away from walls, in the normal placement for speakers.
The first woofer that I am using is the nice looking, low distortion, deep bass output Seas W16. It looks great on paper, but it is quite expensive ($256 each). So I decided to also make a cheaper version of the speakers using the Seas ER15 ($82). You know, to give back to everyone out there who has helped me. In case someone wants to build these and needs something cheaper. Both versions will be available for on wall and in room placement. That means that we will have four different versions of these speakers:
-Schlafmutze Deluxe On Wall
Uses the expensive Seas W16 woofer and the crossover will be made using measurements taken with the speaker pushed right up to a wall. I do not have the crossover designed yet, but let’s take a preliminary guess of roughly $1,000 per pair for drivers and crossover parts.
-Schlafmutze Deluxe In Room
Same as above, but the crossover will be developed from measurements of a more typical in room placement, on speaker stands, in the middle of a room at least 3 feet/1 meter away from walls.
-Schlafmutze Basic On Wall
Here we have the cheaper version with the ER15 woofer, designed to be placed right up against a wall. Again, the crossover is not done and any cost estimate is only a guess. I’ll put that guess at $600 per pair for driver and crossover parts.
-Schlafmutze Basic In Room
Same as above, but for more typical in room placement, away from walls.
Here is a photo showing both flavors. The Schlafmutze Basics are on the left, dressed in dramatic black. The Deluxes are on the right, sporting their fashionable copper phase plugs.
Cabinet size- Keeping it small:
To get an idea of how small these speakers are, note the CD case in the top photo. Smaller speakers than these certainly exist. Heck, there are 3” full range driver designs that fit into a cube not much bigger than the drivers. But here we want to have solid bass down to almost 80 Hz so that we can meet a subwoofer. We want a tweeter to have good highs. The tweeter will be a small flange one due to the size target. And we will be using low distortion drivers. Given these constraints the speakers are just about the smallest that they can be.
The width of 6.5” was dictated by the minimum wood needed around the woofer. The height of 10.5” was almost the minimum needed to have the woofer, tweeter, and facets for baffle diffraction control. Maybe 1/2” could have been shaved off the top dimension but the cabinet build was a little less daunting with a little extra wood above to provide some room for errors. The depth of 8.5” resulted from the minimum volume needed for the woofer to play down to reach the subwoofer without any gap in response between the speakers and the sub.
Along the way there were many times when the size could have creeped up- using a regular sized (i.e., larger) flanged tweeter, using a smaller woofer but then porting it for more bass but then needing a larger cabinet, enlarging and/or porting the cabinet for more bass, using a larger woofer, etc. But I stuck with small as a constraint as much as I could. If you think about a regular, “small” hi fi speaker like the much loved Modula MT, for example, it’s really too big to have in an office. And getting much smaller is not super easy. Comparing the dimensions of the Modula MT’s to the Schalfmutze MT’s, externally 7 Schlafmutzes could fit into the volume of 1 Modula. Internally it’s almost 2.5 Schlafmatuzes into 1 Modula. Maybe those numbers and the photo below of the Schlafmutzes next to the Modulas and the floorstanding Spassvogels will help provide an idea of the scale.
Image not available
Potential applications for these speakers:
At the end of the day, I am not aware of too many very low distortion, small speakers able to play down to 80 Hz. So these speakers could be good for any situation where a small speaker is needed. Maybe as true “bookshelf speakers,” actually sitting on a bookshelf. In an office. Or as the rear/surround speakers in a home theater setup, where there is less space for the speakers and they are placed up against a wall. Maybe you live in a small space. Or if you just want nice, clean sounding speakers that are small. With the on wall and in room crossover options, there should be flexibility for most situations. Very likely you will want to pair the speakers with a sub.
“Near field monitors”
Owing to how this project started, I made them for the purpose of sitting close to the speakers, almost at arm’s length. A while ago we discussed design considerations for near field speakers:
In the end, I don’t think the “near field” constraint means much. We often take in-cabinet driver measurements from 1 meter away anyways. Well, maybe there are a few relevant points: Like keeping the radiating area of the drivers (e.g., top of the tweeter to the bottom of the woofer) as small as possible for best integration. Anyways, these speakers will qualify as “near field” but they’re going to be just as good (or bad!
) as speakers you would listen to 12 feet away.
Meet the drivers:
Tweeter: Scanspeak D3004/602010, $131
To keep the cabinet small we need a small flanged tweeter. This one was the lowest distortion small-flanged tweeter that I could find. It can be crossed somewhat low, which provides a little flexibility with the crossover design. The distortion does rise below 2,000 Hz so we will keep that in mind. You need teeny Groups screws to mount this tweeter. Bonus: The grill keeps curious fingers away from the tweeter.
Deluxe woofer: Seas Excel W16NX-001 (E0049-08 ), $256
A magnesium cone ~5.5” woofer from Seas. The distortion is low and it likes a small box. Excellent for our purposes here. The distortion does not look quite as low as the Scanspeak 15W but the Scanspeak would need a box ~4 times larger for the same bass output. The Seas W16 works better in a smaller box than the venerable W15. Distortion does rise above 1,000 Hz- something else to be kept in mind for the crossover. The metal cone gets floppy above 4,000 Hz so we will avoid that. Bonus: Many people love the Seas Excel drivers so I get to play with one here. Another bonus: The copper phase plug and this woofer, in general, look cool.
Basic woofer: Seas ER15RLY (H1455), $82
In making a cheaper version of the speaker, I needed a woofer that would fit into the cabinet built for the W16 woofers. And I wanted to keep this woofer under $100. Some of the options, all from Seas, were the MCA15RCY, the L15RLY/P, the CA15RLY, and the ER15RLY. The MCA15 and the CA15 look to be older and I want to use drivers that will be around as long as possible, so all the design work here is useful for a while. The ER15 looks to be a decent, all around performer and it may be the newest of the bunch. Seems like a safe choice here.
Cabinet design- Faceted and Slanted:
For a prior project I made a small collection of test cabinets in various configurations to see the influence of cabinet shape on baffle diffraction. I came away thinking that one of the better cabinet configurations is to have facets cut into the cabinet and also have the front baffle slanted. If you want to see the measurements, the link is here:
Start at post Firmware news... and then read onto the following page.
A general discussion on methods for cutting facets can be found here:
I’ll show details of how I cut the facets on my table saw for these mini MT’s. The smaller cabinet really made things much easier than the larger cabinets I tried earlier. If you want to try your hand at a faceted cabinet I recommend starting with something small.
Here is a side view photo showing the angle of it all.
Bass tuning and options:
The sealed cabinets I made have an internal volume of 303 cubic inches or 5 liters before we subtract out the volume of the drivers and crossovers. I used WinISD to get a rough idea of bass output. No, it doesn’t provide a terribly accurate picture of what is really going on, especially when room interactions are there. But it’s a rough place to start. The F3 (-3 dB) point for the W16 in a cabinet of this small volume is at 80 Hz. Couple these with a sub and a prepro/receiver crossed at 80 Hz (or lower) and you will not be missing any output.
If you want more bass extension out of these speakers, the W16 woofer can certainly provide it. Increase the volume or port them with increased volume. According to WinISD, you could get an F3 of 45 Hz from these if you roughly double the volume and add a port. I have no idea how realistic that is. But if you do want to increase the cabinet volume you can either add volume below the woofer, make them deeper, or even try both. However you must keep the front baffle exactly as shown. The facets, slant, width, height above the woofer, and tweeter position should not be changed. I will provide all of these details as the project progresses.
Which speaker should I build?
Some thoughts on the Deluxe (W16 woofer) versus the Basic (ER15 speakers).
-I really do prefer the deluxes. The difference is not subtle. But both speakers came out well. Both sound very good. For me, I like the extra clarity, low distortion, and tighter bass that the W16 woofer offers. It’s a noticable difference. Although the ER15 is supposed to be pretty good. At ~$82 each it’s a driver in the high value range. I probably should have listened to the basics before the deluxes. So as not to be so spoiled. If you don’t hear the deluxes first, you might be OK. When I first heard the basics, I was underwhelmed. But then with the voicing, I brought them to life. They do sing well now.
-The deluxes are going to be maybe $300-350 more per pair. (Specifics to follow, in the future.) That’s a lot. So don’t build the deluxes if it’s going to mean that your kids go hungry or you can’t make the rent.
-The ER15 and the W16 woofers fit into the exact same cabinet hole. So you could start with the ER15’s and, some day, upgrade to the W16’s with the same cabinets. But the crossover changes, too.
-The deluxes are easier for an amp to run, I found. When playing through a receiver, the deluxes played fine. As did the basics. But when the volume was turned up high, the basics shut down the receiver, putting it into protection mode. The deluxes did not do that. You might want to consider what you are using to drive the speakers before deciding on basics versus deluxe.
-Bass extension. For these cabinets, the W16 modeled to reach deeper, solid to 80 Hz. The ER15 modeled to not go as deep, maybe only to 95 Hz or so. But I think that the near field measurements I took in the cabinets look as though both woofers hit 80 Hz prior to any roll off. I’ll post those plots overlayed with typical sub crossovers some day. For the moment, I would not let bass extension factor in to a basics versus deluxe decision.
Project name- The Schlafmutze Mini MT’s:
In keeping with my last project, the Spassvogels (a person who jokes around a lot, literally “joke bird”), we’ll go with another German nickname that my gal uses for me. When you wake up in the morning and look, ummm, not fully alive, in the US we might call you a “sleepy head.” In Germany they might call you a “Schlafmutze.” Translated literally it’s “sleep cap.” Caps are small, as are these speakers. So “Schlafmutze” is is.
Here is another beauty shot of the Schalfmutze Basics, just for fun.
OK, that’s the basic idea of the project. The cabinets are built. Measurements and crossover work are in progress, then voicing. I’ll post progress as it happens. So far, it's a really fun little project.
This speaker design is still in progress. As things get closer to the end I will update this thread and put all the relevant, permanent details into these first few posts. For now here is the start of the project and where the progress is at, currently.
Introduction and Design Goals:
This project came about from my wanting to have some very nice speakers in my office, on the shelves above my desks. So the cabinets will have to be as small as possible and yet have enough bass to reach a sub. Also I favor designs with low distortion.
The major design goals here are:
-A cabinet size as small as possible
-Plays down to 80 Hz for good crossover to a sub.
-Low distortion
Working within those constraints we will come up with the best speaker possible, considering the cabinet design, driver choice, and crossover design. I will be placing these speakers up against a wall (on the shelves) so one crossover will likely have decreased no baffle step compensation (BSC). But I will also provide a second crossover option in case anyone wants to place the speakers on a stand, away from walls, in the normal placement for speakers.
The first woofer that I am using is the nice looking, low distortion, deep bass output Seas W16. It looks great on paper, but it is quite expensive ($256 each). So I decided to also make a cheaper version of the speakers using the Seas ER15 ($82). You know, to give back to everyone out there who has helped me. In case someone wants to build these and needs something cheaper. Both versions will be available for on wall and in room placement. That means that we will have four different versions of these speakers:
-Schlafmutze Deluxe On Wall
Uses the expensive Seas W16 woofer and the crossover will be made using measurements taken with the speaker pushed right up to a wall. I do not have the crossover designed yet, but let’s take a preliminary guess of roughly $1,000 per pair for drivers and crossover parts.
-Schlafmutze Deluxe In Room
Same as above, but the crossover will be developed from measurements of a more typical in room placement, on speaker stands, in the middle of a room at least 3 feet/1 meter away from walls.
-Schlafmutze Basic On Wall
Here we have the cheaper version with the ER15 woofer, designed to be placed right up against a wall. Again, the crossover is not done and any cost estimate is only a guess. I’ll put that guess at $600 per pair for driver and crossover parts.
-Schlafmutze Basic In Room
Same as above, but for more typical in room placement, away from walls.
Here is a photo showing both flavors. The Schlafmutze Basics are on the left, dressed in dramatic black. The Deluxes are on the right, sporting their fashionable copper phase plugs.
Cabinet size- Keeping it small:
To get an idea of how small these speakers are, note the CD case in the top photo. Smaller speakers than these certainly exist. Heck, there are 3” full range driver designs that fit into a cube not much bigger than the drivers. But here we want to have solid bass down to almost 80 Hz so that we can meet a subwoofer. We want a tweeter to have good highs. The tweeter will be a small flange one due to the size target. And we will be using low distortion drivers. Given these constraints the speakers are just about the smallest that they can be.
The width of 6.5” was dictated by the minimum wood needed around the woofer. The height of 10.5” was almost the minimum needed to have the woofer, tweeter, and facets for baffle diffraction control. Maybe 1/2” could have been shaved off the top dimension but the cabinet build was a little less daunting with a little extra wood above to provide some room for errors. The depth of 8.5” resulted from the minimum volume needed for the woofer to play down to reach the subwoofer without any gap in response between the speakers and the sub.
Along the way there were many times when the size could have creeped up- using a regular sized (i.e., larger) flanged tweeter, using a smaller woofer but then porting it for more bass but then needing a larger cabinet, enlarging and/or porting the cabinet for more bass, using a larger woofer, etc. But I stuck with small as a constraint as much as I could. If you think about a regular, “small” hi fi speaker like the much loved Modula MT, for example, it’s really too big to have in an office. And getting much smaller is not super easy. Comparing the dimensions of the Modula MT’s to the Schalfmutze MT’s, externally 7 Schlafmutzes could fit into the volume of 1 Modula. Internally it’s almost 2.5 Schlafmatuzes into 1 Modula. Maybe those numbers and the photo below of the Schlafmutzes next to the Modulas and the floorstanding Spassvogels will help provide an idea of the scale.
Image not available
Potential applications for these speakers:
At the end of the day, I am not aware of too many very low distortion, small speakers able to play down to 80 Hz. So these speakers could be good for any situation where a small speaker is needed. Maybe as true “bookshelf speakers,” actually sitting on a bookshelf. In an office. Or as the rear/surround speakers in a home theater setup, where there is less space for the speakers and they are placed up against a wall. Maybe you live in a small space. Or if you just want nice, clean sounding speakers that are small. With the on wall and in room crossover options, there should be flexibility for most situations. Very likely you will want to pair the speakers with a sub.
“Near field monitors”
Owing to how this project started, I made them for the purpose of sitting close to the speakers, almost at arm’s length. A while ago we discussed design considerations for near field speakers:
In the end, I don’t think the “near field” constraint means much. We often take in-cabinet driver measurements from 1 meter away anyways. Well, maybe there are a few relevant points: Like keeping the radiating area of the drivers (e.g., top of the tweeter to the bottom of the woofer) as small as possible for best integration. Anyways, these speakers will qualify as “near field” but they’re going to be just as good (or bad!
) as speakers you would listen to 12 feet away.Meet the drivers:
Tweeter: Scanspeak D3004/602010, $131
To keep the cabinet small we need a small flanged tweeter. This one was the lowest distortion small-flanged tweeter that I could find. It can be crossed somewhat low, which provides a little flexibility with the crossover design. The distortion does rise below 2,000 Hz so we will keep that in mind. You need teeny Groups screws to mount this tweeter. Bonus: The grill keeps curious fingers away from the tweeter.
Deluxe woofer: Seas Excel W16NX-001 (E0049-08 ), $256
A magnesium cone ~5.5” woofer from Seas. The distortion is low and it likes a small box. Excellent for our purposes here. The distortion does not look quite as low as the Scanspeak 15W but the Scanspeak would need a box ~4 times larger for the same bass output. The Seas W16 works better in a smaller box than the venerable W15. Distortion does rise above 1,000 Hz- something else to be kept in mind for the crossover. The metal cone gets floppy above 4,000 Hz so we will avoid that. Bonus: Many people love the Seas Excel drivers so I get to play with one here. Another bonus: The copper phase plug and this woofer, in general, look cool.
Basic woofer: Seas ER15RLY (H1455), $82
In making a cheaper version of the speaker, I needed a woofer that would fit into the cabinet built for the W16 woofers. And I wanted to keep this woofer under $100. Some of the options, all from Seas, were the MCA15RCY, the L15RLY/P, the CA15RLY, and the ER15RLY. The MCA15 and the CA15 look to be older and I want to use drivers that will be around as long as possible, so all the design work here is useful for a while. The ER15 looks to be a decent, all around performer and it may be the newest of the bunch. Seems like a safe choice here.
Cabinet design- Faceted and Slanted:
For a prior project I made a small collection of test cabinets in various configurations to see the influence of cabinet shape on baffle diffraction. I came away thinking that one of the better cabinet configurations is to have facets cut into the cabinet and also have the front baffle slanted. If you want to see the measurements, the link is here:
Start at post Firmware news... and then read onto the following page.
A general discussion on methods for cutting facets can be found here:
I’ll show details of how I cut the facets on my table saw for these mini MT’s. The smaller cabinet really made things much easier than the larger cabinets I tried earlier. If you want to try your hand at a faceted cabinet I recommend starting with something small.
Here is a side view photo showing the angle of it all.
Bass tuning and options:
The sealed cabinets I made have an internal volume of 303 cubic inches or 5 liters before we subtract out the volume of the drivers and crossovers. I used WinISD to get a rough idea of bass output. No, it doesn’t provide a terribly accurate picture of what is really going on, especially when room interactions are there. But it’s a rough place to start. The F3 (-3 dB) point for the W16 in a cabinet of this small volume is at 80 Hz. Couple these with a sub and a prepro/receiver crossed at 80 Hz (or lower) and you will not be missing any output.
If you want more bass extension out of these speakers, the W16 woofer can certainly provide it. Increase the volume or port them with increased volume. According to WinISD, you could get an F3 of 45 Hz from these if you roughly double the volume and add a port. I have no idea how realistic that is. But if you do want to increase the cabinet volume you can either add volume below the woofer, make them deeper, or even try both. However you must keep the front baffle exactly as shown. The facets, slant, width, height above the woofer, and tweeter position should not be changed. I will provide all of these details as the project progresses.
Which speaker should I build?
Some thoughts on the Deluxe (W16 woofer) versus the Basic (ER15 speakers).
-I really do prefer the deluxes. The difference is not subtle. But both speakers came out well. Both sound very good. For me, I like the extra clarity, low distortion, and tighter bass that the W16 woofer offers. It’s a noticable difference. Although the ER15 is supposed to be pretty good. At ~$82 each it’s a driver in the high value range. I probably should have listened to the basics before the deluxes. So as not to be so spoiled. If you don’t hear the deluxes first, you might be OK.
When I first heard the basics, I was underwhelmed. But then with the voicing, I brought them to life. They do sing well now.-The deluxes are going to be maybe $300-350 more per pair. (Specifics to follow, in the future.) That’s a lot. So don’t build the deluxes if it’s going to mean that your kids go hungry or you can’t make the rent.
-The ER15 and the W16 woofers fit into the exact same cabinet hole. So you could start with the ER15’s and, some day, upgrade to the W16’s with the same cabinets. But the crossover changes, too.
-The deluxes are easier for an amp to run, I found. When playing through a receiver, the deluxes played fine. As did the basics. But when the volume was turned up high, the basics shut down the receiver, putting it into protection mode. The deluxes did not do that. You might want to consider what you are using to drive the speakers before deciding on basics versus deluxe.
-Bass extension. For these cabinets, the W16 modeled to reach deeper, solid to 80 Hz. The ER15 modeled to not go as deep, maybe only to 95 Hz or so. But I think that the near field measurements I took in the cabinets look as though both woofers hit 80 Hz prior to any roll off. I’ll post those plots overlayed with typical sub crossovers some day. For the moment, I would not let bass extension factor in to a basics versus deluxe decision.
Project name- The Schlafmutze Mini MT’s:
In keeping with my last project, the Spassvogels (a person who jokes around a lot, literally “joke bird”), we’ll go with another German nickname that my gal uses for me. When you wake up in the morning and look, ummm, not fully alive, in the US we might call you a “sleepy head.” In Germany they might call you a “Schlafmutze.” Translated literally it’s “sleep cap.” Caps are small, as are these speakers. So “Schlafmutze” is is.
Here is another beauty shot of the Schalfmutze Basics, just for fun.
OK, that’s the basic idea of the project. The cabinets are built. Measurements and crossover work are in progress, then voicing. I’ll post progress as it happens. So far, it's a really fun little project.
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