Hi folks
No experience with speaker design (though lots with woodworking!), and I want to build a set of speakers into a console / cabinet.
I am planning to use a kit - probably the Samba MT Bookshelf kit from parts express. However, because of the dimensions of the console, I will have to adapt the enclosure size for the speakers, and move the port.
My questions are:
1. The kit includes a port which is on the rear of the kit enclosure. My console will be wall-mounted so I cannot do this. What are the implications of moving the port to the front baffle of the speaker? What about the bottom?
2. Can I adjust the dimensions of the enclosure as long as I retain the same internal volume as the kit enclosure? The kit enclosure is 0.56 cu ft internally. The woofer (Dayton Audio RS180P-4) says it is rated for 0.27 cu ft sealed and 0.64 cu ft "vented" (which presumably means ported?). How much leeway do I have with these measurements? Is it going to sound dreadful if it's in a 0.8 cu ft box or a 0.5 cu ft box?
3. The kit enclosure is mdf. My cabinet will be solid wood, but I could always line the speaker enclosures with mdf if it would be beneficial? Or is solid wood OK when lined with damping foam?
Thanks very much!!!
Charliefreak
No experience with speaker design (though lots with woodworking!), and I want to build a set of speakers into a console / cabinet.
I am planning to use a kit - probably the Samba MT Bookshelf kit from parts express. However, because of the dimensions of the console, I will have to adapt the enclosure size for the speakers, and move the port.
My questions are:
1. The kit includes a port which is on the rear of the kit enclosure. My console will be wall-mounted so I cannot do this. What are the implications of moving the port to the front baffle of the speaker? What about the bottom?
2. Can I adjust the dimensions of the enclosure as long as I retain the same internal volume as the kit enclosure? The kit enclosure is 0.56 cu ft internally. The woofer (Dayton Audio RS180P-4) says it is rated for 0.27 cu ft sealed and 0.64 cu ft "vented" (which presumably means ported?). How much leeway do I have with these measurements? Is it going to sound dreadful if it's in a 0.8 cu ft box or a 0.5 cu ft box?
3. The kit enclosure is mdf. My cabinet will be solid wood, but I could always line the speaker enclosures with mdf if it would be beneficial? Or is solid wood OK when lined with damping foam?
Thanks very much!!!
Charliefreak
Any chance you could draw a rough picture of what you want to do? When you say "wall mount" and "built in" I'm wondering if you'd be better off with speakers that don't have baffle step compensation (bsc for short). Because the inside of a car is an infinite baffle, car speakers don't need any bsc, so they may be more suitable.
Thanks for the reply. It's will look something like this, but instead of the legs on this the whole rectangular unit will be mounted on the wall.
So there is space / room for a speaker box on each end, but it will be completely tight against the wall at the back.
So there is space / room for a speaker box on each end, but it will be completely tight against the wall at the back.
If you are going to put it against the wall, you might want to consider sealed instead of ported. Bass won't extend quite as low, but it will be a lot tighter and cleaner. Then a smaller cabinet, .27 cu. ft. instead .64, is all that you need and port placement issues all go away.
Also, the design you show looks to be essentially square in the front and close to a cube overall. Not really the best ratio of dimensions. Better for them to be different ratios instead of 1:1:1.
How much all of this is going to matter depends on what your expectations are for this unit. Obviously aesthetics are a big part of this and it might still satisfy your music needs even if not optimal.
I wouldn't worry about not using MDF. There are some of us who never use it and believe that plywood is a much better material anyhow.
(P.S. I don't allow MDF into my shop for anything. Period. It is a terrible material to work with. I usually use Baltic Birch plywood for speaker cabinets. Not sure how much sonic difference there would be to use solid wood instead.)
Also, the design you show looks to be essentially square in the front and close to a cube overall. Not really the best ratio of dimensions. Better for them to be different ratios instead of 1:1:1.
How much all of this is going to matter depends on what your expectations are for this unit. Obviously aesthetics are a big part of this and it might still satisfy your music needs even if not optimal.
I wouldn't worry about not using MDF. There are some of us who never use it and believe that plywood is a much better material anyhow.
(P.S. I don't allow MDF into my shop for anything. Period. It is a terrible material to work with. I usually use Baltic Birch plywood for speaker cabinets. Not sure how much sonic difference there would be to use solid wood instead.)
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Changing the dimensions of the box, and keeping a similar volume, can be done. The more significant concerns in this case would IMO be room and wall interaction.
Interaction with the wall behind involves a step, which can lead to some unwanted resonances. A larger front panel for example might increase the support of that panel to reduce wall interaction. It would also bring the panel closer to the wall with the reduced box depth. This can be better and worse at the same time.
Interaction with the wall behind involves a step, which can lead to some unwanted resonances. A larger front panel for example might increase the support of that panel to reduce wall interaction. It would also bring the panel closer to the wall with the reduced box depth. This can be better and worse at the same time.
There are a few more issues with that enclosure design.
The recessed baffle with the large cabinet edges extending out front past it on all four sides is going to result in a significant amount of diffraction and lots of extraneous peaks at various frequencies. In short, it won't be a very flat frequency response. Some people go to length and use a large radius or bevels on the cabinet edges to eliminate the diffraction problem. This design goes entirely in the opposite direction and will worsen it.
Also, the two enclosures appear to be fairly close to each other. It looks like only about 2 to 3 feet separating them. So if you want good imagining you will have to sit pretty close to the wall with the speakers on it. Generally you want to have speakers separated more and further out in the room away from the wall.
So you are probably not going to be able to have the best in sound quality and imaging with this design. However, it may still be very enjoyable as long as you're not expecting very high end results.
The recessed baffle with the large cabinet edges extending out front past it on all four sides is going to result in a significant amount of diffraction and lots of extraneous peaks at various frequencies. In short, it won't be a very flat frequency response. Some people go to length and use a large radius or bevels on the cabinet edges to eliminate the diffraction problem. This design goes entirely in the opposite direction and will worsen it.
Also, the two enclosures appear to be fairly close to each other. It looks like only about 2 to 3 feet separating them. So if you want good imagining you will have to sit pretty close to the wall with the speakers on it. Generally you want to have speakers separated more and further out in the room away from the wall.
So you are probably not going to be able to have the best in sound quality and imaging with this design. However, it may still be very enjoyable as long as you're not expecting very high end results.
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my remarks
Best is to keep the tweeter and woofer on one horizontal line, otherwise the sound image may be off.
Reces the drivers so the front of the frame with the driver is flush with the panel
Don recess the front baffle so you don't have those side sticking out.
And make sure the cabinet is not a square box, height, depth and width should all be different dimensions to avoid standing waves.
But it can be done, and even this plan may sound quiet decent, but not as good as the original kit form due to the points mentioned above (by me and others).
Best is to keep the tweeter and woofer on one horizontal line, otherwise the sound image may be off.
Reces the drivers so the front of the frame with the driver is flush with the panel
Don recess the front baffle so you don't have those side sticking out.
And make sure the cabinet is not a square box, height, depth and width should all be different dimensions to avoid standing waves.
But it can be done, and even this plan may sound quiet decent, but not as good as the original kit form due to the points mentioned above (by me and others).
Well, looking at the pic you are very likely to end up with one big boom box if that is mounted on the wall. First off you would need to recess that tweeter at the very least.
This is an old trick which may or may not work in your case, that is to raise the mid/woofer off the front baffle with a brass washer under each of the screws, this is fitted between the baffle and the frame of the driver.
This leakage of air detunes the box somewhat and allows the driver to work at its natural resonance, but, you would have to experiment with the width of the gap to get the most desirable result. Also block off that port and half fill the cabinet with sound absorbent material, you will also have to experiment with the quantity to get the most pleasing result.
You could also obtain a large value non-polar electrolytic capacitor ( say a 220uF) and wire it in series with + wire of the speaker cable, this will help taper of the bass response of the speaker to compensate for the close wall position. The boundary effect could boost the bass from anything up to 9 db. Better still, if your amplifier has tone controls that will allow the bass to be trimmed, by all means use that first before any other measures.
In this hobby, trial and error plays a big part in what we do to gain the necessary knowledge in refining our abilities for future challenges, and other waffle such as that.
C.M
This is an old trick which may or may not work in your case, that is to raise the mid/woofer off the front baffle with a brass washer under each of the screws, this is fitted between the baffle and the frame of the driver.
This leakage of air detunes the box somewhat and allows the driver to work at its natural resonance, but, you would have to experiment with the width of the gap to get the most desirable result. Also block off that port and half fill the cabinet with sound absorbent material, you will also have to experiment with the quantity to get the most pleasing result.
You could also obtain a large value non-polar electrolytic capacitor ( say a 220uF) and wire it in series with + wire of the speaker cable, this will help taper of the bass response of the speaker to compensate for the close wall position. The boundary effect could boost the bass from anything up to 9 db. Better still, if your amplifier has tone controls that will allow the bass to be trimmed, by all means use that first before any other measures.
In this hobby, trial and error plays a big part in what we do to gain the necessary knowledge in refining our abilities for future challenges, and other waffle such as that.
C.M
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Thanks for all the help and feedback folks.
I'm curious about a couple of things (and I know nothing about speaker design so not questioning, just want to learn more).
1. The speaker baffle will be about 2 feet from the wall (the depth of the cabinet). Will the speaker still interact with the wall strongly, even if it has a front-firing port (or no port at all)? Is this interaction caused by the energy from the front of the speaker or vibrations in the box itself (and if the latter, can I damp them somehow). In my current hifi setup my speakers are actually closer to a wall than this.
2. A couple of comments about how the recessed baffle will cause diffraction. I had planned to recess the baffle because I want the grilles to be flush with the front of the cabinet when installed. I'm curious about how the recessed baffle is any different from adding a speaker grille? When I add the speaker grilles to my normal hifi speakers I am effectively putting about a 1/2" border around all the front edges of the speaker, exactly like the recessed baffle in the picture (though admittedly it's more in the picture)?
I should add that the pic isn't my actual design or dimensions - was just to illustrate the rough idea.
Thanks again
I'm curious about a couple of things (and I know nothing about speaker design so not questioning, just want to learn more).
1. The speaker baffle will be about 2 feet from the wall (the depth of the cabinet). Will the speaker still interact with the wall strongly, even if it has a front-firing port (or no port at all)? Is this interaction caused by the energy from the front of the speaker or vibrations in the box itself (and if the latter, can I damp them somehow). In my current hifi setup my speakers are actually closer to a wall than this.
2. A couple of comments about how the recessed baffle will cause diffraction. I had planned to recess the baffle because I want the grilles to be flush with the front of the cabinet when installed. I'm curious about how the recessed baffle is any different from adding a speaker grille? When I add the speaker grilles to my normal hifi speakers I am effectively putting about a 1/2" border around all the front edges of the speaker, exactly like the recessed baffle in the picture (though admittedly it's more in the picture)?
I should add that the pic isn't my actual design or dimensions - was just to illustrate the rough idea.
Thanks again
1. Low frequencies have wave lengths that are much greater than the size of the speaker. Ergo, the speaker itself disappears and acts more like a small point source. With the speaker well out into the room the bass frequencies are omnidirectional, wrap completely around the cabinet, and eventually reflect off of the walls behind and to the side of the speaker. This gives you lots of options for moving the speakers into the best room location. When you put them against the wall they effectively become semi-directional, or sometime referred to as half-space (2Pi), which can sound boomy. And it also prevents you from positioning the speakers for optimum bass performance in other parts of the room.
2. Any perturbations on the front of the baffle are going to cause diffraction. It doesn’t matter whether they are there due to a recessed baffle of the added frame of a grill covering. That’s why you will see that most of the speakers appearing in this forum don’t have any grills at all.
3. As I have mentioned before, your design of a single cabinet with rather close speaker to speaker spacing is already creating many compromises in the sound. Particularly compared to separate speaker cabinets what can be placed well out into the room and located where they need to be for optimum sound quality. So I’m not sure it really pays that much to sweat the details in this case. Especially if this is for casual listening rather than sitting in one precise spot and wanting the ultimate in sound quality.
2. Any perturbations on the front of the baffle are going to cause diffraction. It doesn’t matter whether they are there due to a recessed baffle of the added frame of a grill covering. That’s why you will see that most of the speakers appearing in this forum don’t have any grills at all.
3. As I have mentioned before, your design of a single cabinet with rather close speaker to speaker spacing is already creating many compromises in the sound. Particularly compared to separate speaker cabinets what can be placed well out into the room and located where they need to be for optimum sound quality. So I’m not sure it really pays that much to sweat the details in this case. Especially if this is for casual listening rather than sitting in one precise spot and wanting the ultimate in sound quality.