Is it feasible to begin with a proven pre-existing sealed-box loudpeaker design and reconfigure the enclosure dimensions so that the depth is no more than 6" while making sure that the internal volume of the enclosure is maintained?
I have been studying various books and internet material regarding the design of various enclosures.
What I would like to do is to begin with a proven sealed box crossover/driver/enclosure design and simply reshape the cabinet so that it fits more snuggly against the wall (spousal request) while maintaining a good, warm tonal quality. I have been very interested in Vienna Acoustics Waltz speaker concept (but am not married to it). Some of my thoughts have been along a shallow tower design which can be hidden in many ways using existing room furniture.
Could anyone comment on my assumptions?
I have been studying various books and internet material regarding the design of various enclosures.
What I would like to do is to begin with a proven sealed box crossover/driver/enclosure design and simply reshape the cabinet so that it fits more snuggly against the wall (spousal request) while maintaining a good, warm tonal quality. I have been very interested in Vienna Acoustics Waltz speaker concept (but am not married to it). Some of my thoughts have been along a shallow tower design which can be hidden in many ways using existing room furniture.
Could anyone comment on my assumptions?
I've seen and heard a very impressive design called the Bandor Picture. This used a single Bandor 2" full-range drive unit and the enclosure was just 2" deep. The other dimensions were chosen to make the internal volume up to the necessary 1.5 to 2 litres.
There's no reason that this couldn't be done using two or four Bandor drivers to increase the SPL - I've considered doing this myself.
I can't think why you couldn't make your 6" design with conventional drive units.
Steve
There's no reason that this couldn't be done using two or four Bandor drivers to increase the SPL - I've considered doing this myself.
I can't think why you couldn't make your 6" design with conventional drive units.
Steve
My understanding is that the volume of air in a sealed enclosure is supposed to provide an "air spring" that is tuned for the particular driver that is mounted. The same for the various vented enclosures, except that the volume needs to be tuned to some frequency instead of some spring rate.
Theoretically, with a perfect fluid, no turbulence or a size that doesn't change due to the moving driver, only the volume and not the shape determines the tuning.
My view is that, at a practical level, the effects of shape are negligible. Otherwise, the various internal features such as braces, corners, ports, stuffing and even the driver cage would be "audible" to the well-eared.
I've also noticed that many commercially available transmission lines would be extremely thin when unfolded. Other than tuning the length of the line to right frequency, it appears that the critical dimensions are for the area of the profile. It might be possible to create a TL so thin that the driver magnet (almost) touches the back wall and making it sufficiently wide to maintain the appropriate profile area over the length. The wall could also be the sub.
Hmmm......
ensen.
Theoretically, with a perfect fluid, no turbulence or a size that doesn't change due to the moving driver, only the volume and not the shape determines the tuning.
My view is that, at a practical level, the effects of shape are negligible. Otherwise, the various internal features such as braces, corners, ports, stuffing and even the driver cage would be "audible" to the well-eared.
I've also noticed that many commercially available transmission lines would be extremely thin when unfolded. Other than tuning the length of the line to right frequency, it appears that the critical dimensions are for the area of the profile. It might be possible to create a TL so thin that the driver magnet (almost) touches the back wall and making it sufficiently wide to maintain the appropriate profile area over the length. The wall could also be the sub.
Hmmm......
ensen.I just became a member for this post...
and YES, box shape DOES have an affect on sound when the box is made to extreme dimensions as you have described. With a box only being 6 inches deep, you don't leave much room for mounting depth of bigger subs and it affects sound alot, I can't remember the "Golden Rule" but I'm sure alot of you know it...
and YES, box shape DOES have an affect on sound when the box is made to extreme dimensions as you have described. With a box only being 6 inches deep, you don't leave much room for mounting depth of bigger subs and it affects sound alot, I can't remember the "Golden Rule" but I'm sure alot of you know it...
I will make a HUGE recommendation, that you put a deflex panel directly behind the driver on the opposing wall of the enclosure, this will rid you of any immediate problems with reflections off the back of the cabinet. I have a pair of the 6 1/2" Seas coaxes with the cocentric mounted tweeter in tiny custom fiberglass enclosures in my car. Adding a deflex panel to the back of each enclosure cleaned up the midrange a TREMENDOUS amount! I cannot recommend this enough!!!! I think you can get them from Parts Express now.
I am right now using a pair of Spirit Absolute 2 studio monitors, (6.5" midbass - 45hz bottom, 1" silk tweeter, yummy) and they're wonderful, but the footprint is a bit large. If you made them 6" deep, with the current volume and porting, it would be.... strange to look at. Perhaps it would make more sense in a home-theatre setting.
If you'd like, I will get you the dimensions of everything and some pictures, but understand that driver / crossover choice is going to be tough, because these are completely custom drivers...
If you'd like, I will get you the dimensions of everything and some pictures, but understand that driver / crossover choice is going to be tough, because these are completely custom drivers...
The ratio of the dimensions in your cabinet do very much play a role in how your speaker sounds. The issue with a shallow speaker is that the reflection off the back wall of the cabinet is sooner, and has not had as much chance to be attenuated by any damping, so there is a much greater chance of this reflection being transmitted thru the cone and causing a noticeable time-smear. This can be minimized with serious absorbant or a relective surface that redirects the impinging wave away from the back of the cone (i believe this is what the deflex does).
dave
dave
That's because it's no longer on the market. Bandor have always been a drive unit company and various completed cabinets that they have put out from time to time have come and gone. The Picture was one of those.zcab911 said:
Imagine a cabinet 2" deep, with a width of about 10" and a height of about 14". The front was ceramic with a single 2" Bandor driver.
If you go for a design with Bandor drivers, I can certainly help you and, if the cabinet really is so shallow, bracing the panels wouldn't be so difficult.
If you go for another design that you wish to "flatten", can you give us specifics such as internal volume required or the dimensions of an equivalent cabinet? That way we can look at actual dimensions and have a better idea of the real life difficulties of panel bracing and the other issues mentioned.
I'm of the view that you can achieve a narrow cabinet with good sound.
Steve
PS: Dave, if you can get me sufficiently inebriated from where you are, I might be tempted to describe a 2" thick, transmission line speaker based on the Picture concept described. Then again, by the time I've finished typing this out, you will probably have already figured out three variants on the concept.
If the cabinet does not have to be snug against the wall an option that does not really depend on cabinet size is the dipole. If you have the exact same driver, and I am talking about something like the little TB 3" full range drivers, you mount one on the back side of the cabinet out of phase with the one in front. The internal volume is not a real issue because since one speaker moves out while the other moves in there is no air compression involved. Doing a small tower with multiple drivers on the front and the back makes for great voicing. Build another box for a woofer and think of a tuned transmission line with a long thin but wide tube that you could possibly lay along the floor behind an entertainment system if you have one. If you own your own place you could also build your pipe in between the studs in your wall and get most of the speaker completely out of site.
Just something to tickle your thoughts
Just something to tickle your thoughts
planet10 said:
Knew you wouldn't disappoint. Also, you could put the driver centrally and have the line going round the outside - saves on bends.
Good ideas Thatch_Ear. Just out of interest, what is the minimum distance from the wall for a dipole? I was recently planning to put a TL in my loft (attic) with driver and port holes through the floor. You can also do clever things with cupboards in adjacent rooms. I'm sure if we were to explore Dave's house we'd find more tunnels than Colditz.
By the way Dave, if you did that design in 1975 then judging from your photo (which I naturally assume is recent) you must have been about 3 years old. I'm envious - I was only building basic ported designs at that age.
Steve
Boston Acoustics' first designs were quite shallow. The A100 was aprox. 20" wide x 30" high x 8" deep. Tthe A700(?) was about 50% larger while retaining the 8" depth.
Even more radical was an early Duntech design, the PCL-somethingorother. It was ~ 12H x 24W x 3D, and was designed to be hung on a wall...great sounding little speaker.
In both cases, the designers pointed out the elimination of early reflections as one of the main design goals.
Even more radical was an early Duntech design, the PCL-somethingorother. It was ~ 12H x 24W x 3D, and was designed to be hung on a wall...great sounding little speaker.
In both cases, the designers pointed out the elimination of early reflections as one of the main design goals.
Many of the comments confirmed some of my own concerns. I have had satellites for a while (Polk RM 2000), and was never satisfied with the sound (actually, they suck). Some people like it that way, but I always thought the satellites were too small, and that they separated out musical elements a bit too much between the sub and sats.
The main reason for the posting was my concern about the reflections in such a short distance from the rear panel. I also considered and simulated a vented solution with the hope of bass extension, but am afraid that this could worsen things. Think I will stick with sealed box for tightness. Good suggestion on the deflex. I will check into it.
I will also take planet10’s advice and move away from square to more of a pentagon shape. I have thought about a rounder shape, but am concerned about rattle creeping in over time should I need to use a multiple thin layer laminate type enclosure construction technique as suggested in http://users.tpg.com.au/users/gradds/Concept_HT.html, though this may actually be a bit more spousally acceptable. Other than the complexities of volume calculation and bracing concerns, are there any other pitfalls I should watch for?
A couple of notes… the Vienna-Accoustics speaker (www.vienna-acoustics.com) Waltz is my prototype. I noticed that the "Low end" of these speakers bottom at 70Hz. I think this would work great as a pair in a conversation room, but would require a sub in my home entertainment setting. Seeing as I am building for both rooms in our house… (yes, that would be six of these puppies, plus a sub in the entertainment area)… I think I will have time to dial this in, and at $700 per for vienna’s system
, toasting a few sheets of MDF isn’t the worst thing in the world.
Oh, and I am also pretty sure the spouse would not truly appreciate the starkness of that cookie sheet idea… unless I throw a Picasso print in the bag with it. Wonder how that might affect the acoustics, though?
The main reason for the posting was my concern about the reflections in such a short distance from the rear panel. I also considered and simulated a vented solution with the hope of bass extension, but am afraid that this could worsen things. Think I will stick with sealed box for tightness. Good suggestion on the deflex. I will check into it.
I will also take planet10’s advice and move away from square to more of a pentagon shape. I have thought about a rounder shape, but am concerned about rattle creeping in over time should I need to use a multiple thin layer laminate type enclosure construction technique as suggested in http://users.tpg.com.au/users/gradds/Concept_HT.html, though this may actually be a bit more spousally acceptable. Other than the complexities of volume calculation and bracing concerns, are there any other pitfalls I should watch for?
A couple of notes… the Vienna-Accoustics speaker (www.vienna-acoustics.com) Waltz is my prototype. I noticed that the "Low end" of these speakers bottom at 70Hz. I think this would work great as a pair in a conversation room, but would require a sub in my home entertainment setting. Seeing as I am building for both rooms in our house… (yes, that would be six of these puppies, plus a sub in the entertainment area)… I think I will have time to dial this in, and at $700 per for vienna’s system
, toasting a few sheets of MDF isn’t the worst thing in the world.Oh, and I am also pretty sure the spouse would not truly appreciate the starkness of that cookie sheet idea… unless I throw a Picasso print in the bag with it. Wonder how that might affect the acoustics, though?
zcab911 said:
Just a quick tip on the volume calculation point:
There's a free download of a pretty good CAD program at the link below. If you draw the shape of the cross-section of the cabinet, you can get the program to calculate the area. From this the volume calculation is easy.
TurboCAD® Learning Edition - Free Download
Steve
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