I have been reading 'till my eyes bleed on speaker forums trying to figure out what to do with my old JBL D123 075 combo. Now this forum seems like the place I need to be to ask this question!
I have been carting around these old JBL drivers for several years. They came in enclosures that were too small with crossovers that weren't really right and surprise-surprise, I never liked the sound! The drivers are in decent shape. Just a little dusty. The enclosures I have would need a serious rehab if I were to use them, but I think a better bet is to build new ones. I have already built a copy of a JBL N2400 crossover network to re-try the old speakers in their old enclosures. The drivers sound clean, but they are really lacking any low end in their 2-ish cu-ft, leaky enclosures.
So my question is - what kind of enclosure should I build to bring these old drivers to life? I could go full retro and build something to the period. Those tend to be fairly large and low to the ground. That wouldn't be ideal for my small house. I stumbled into MLTL designs, but I'm not sure they are going to save me any floor space. Should i just build a tall box for the volume and hope for some MLTL effects as a bonus?
My run-in with MLTL designs started by looking at the Zu Audio and Tekton 2-way designs since they have a sort of retro look that would go well with these drivers. They also have good internal volume which I think (or am really hoping) is the major cause of the weak low end in the current setup. I like that they bring the drivers closer to ear level without stands too. I didn't realize until recently that those are technically MLTL designs. I played around with the Accidental MLTL Technique and came up with a box, but it's pretty massive. WinISD spit out a box volume of ~7.3 cu-ft. If the box is 40" high and width is 15", then the depth is 21"!
That's not saving me any floor space! I could really use some help and direction from the experts!
I have been carting around these old JBL drivers for several years. They came in enclosures that were too small with crossovers that weren't really right and surprise-surprise, I never liked the sound! The drivers are in decent shape. Just a little dusty. The enclosures I have would need a serious rehab if I were to use them, but I think a better bet is to build new ones. I have already built a copy of a JBL N2400 crossover network to re-try the old speakers in their old enclosures. The drivers sound clean, but they are really lacking any low end in their 2-ish cu-ft, leaky enclosures.
So my question is - what kind of enclosure should I build to bring these old drivers to life? I could go full retro and build something to the period. Those tend to be fairly large and low to the ground. That wouldn't be ideal for my small house. I stumbled into MLTL designs, but I'm not sure they are going to save me any floor space. Should i just build a tall box for the volume and hope for some MLTL effects as a bonus?
My run-in with MLTL designs started by looking at the Zu Audio and Tekton 2-way designs since they have a sort of retro look that would go well with these drivers. They also have good internal volume which I think (or am really hoping) is the major cause of the weak low end in the current setup. I like that they bring the drivers closer to ear level without stands too. I didn't realize until recently that those are technically MLTL designs. I played around with the Accidental MLTL Technique and came up with a box, but it's pretty massive. WinISD spit out a box volume of ~7.3 cu-ft. If the box is 40" high and width is 15", then the depth is 21"!
That's not saving me any floor space! I could really use some help and direction from the experts!MLTL is a good choice for these. WinISD is giving you the max flat size for a simple BR, and doesn't include any 1/4 wave stub effects, which will strengthen the midbass slightly.
The D123 has a Vas of 4.8 cu ft, and as a practical matter, this is big enough. The designer recommended 4 cu ft. This might be about 12x19x39", depending on wall thickness. My first guess would be to go with 4.8 cu ft though, if the size is acceptable. I'm sure someone will run a sim for you.
If you want to be fashionable and make a box with the front as narrow as possible, you will want to incorporate BSC into the crossover. I prefer wider and shallower boxes myself. Once the box starts getting to be about 20" wide, sometimes BSC can be avoided if they are placed near the back wall, as room gain will start to kick in around this frequency, at least in a smaller room.
The D123 has a Vas of 4.8 cu ft, and as a practical matter, this is big enough. The designer recommended 4 cu ft. This might be about 12x19x39", depending on wall thickness. My first guess would be to go with 4.8 cu ft though, if the size is acceptable. I'm sure someone will run a sim for you.
If you want to be fashionable and make a box with the front as narrow as possible, you will want to incorporate BSC into the crossover. I prefer wider and shallower boxes myself. Once the box starts getting to be about 20" wide, sometimes BSC can be avoided if they are placed near the back wall, as room gain will start to kick in around this frequency, at least in a smaller room.
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I'd like to stay as narrow as I can, but the driver becomes a limitation there. The D123s I have are rear-mount only. I could probably get down to 13" or 14" for internal width. It would almost be a square profile at that point -using 39" internal height. I was thinking of prototyping with 1/2" or 3/4" MDF since the drivers are so heavy.
What is BSC in a crossover? Is that something I can incorporate into the N2400 if I have to?
What is BSC in a crossover? Is that something I can incorporate into the N2400 if I have to?
Baffle step compensation.
The short version is the baffle doesn't support wavelengths below a certain frequency, leading to a thin and bright sound. In the case of 14", it would shelve frequencies below 325Hz down about 4db in room.
BSC could be incorporated into the N2400 theoretically, but requires some technical knowledge and simulations.
The short version is the baffle doesn't support wavelengths below a certain frequency, leading to a thin and bright sound. In the case of 14", it would shelve frequencies below 325Hz down about 4db in room.
BSC could be incorporated into the N2400 theoretically, but requires some technical knowledge and simulations.
I should note that the N2400 crossover was used in speakers with ~14" wide baffles and no BSC, and it was apparently just fine. So you might as well try it that way. That said, in the old days speakers were always placed back against a wall, and often surrounded by bookshelves and/or cabinetry.
Probably the simplest thing would be to use the stock crossover, and EQ any correction as needed with digital EQ (especially if your source is digital).
Probably the simplest thing would be to use the stock crossover, and EQ any correction as needed with digital EQ (especially if your source is digital).
I wasn't aware of that narrow baffle effect. I wonder how all the companies making really narrow towers get away with it. Maybe BSC is already part of their crossover design?
How much or what effects does the rear-mounted driver configuration have? The driver will be recessed by 1/2" - 3/4" depending on what thickness wood is used.
How accurate do I need to be with the volume anyway? If I pick 4.8cf, I know there is some space taken up by the drivers, crossover, bracing, etc... Should I just pick a nominal 5cf and let the rest work itself out, or should I try to calculate the volume of anything that takes away from the cabinet volume? Or if I start with 4.8cf I could end up with a little less but probably still more than the 4cf that the designer liked.
How much or what effects does the rear-mounted driver configuration have? The driver will be recessed by 1/2" - 3/4" depending on what thickness wood is used.
How accurate do I need to be with the volume anyway? If I pick 4.8cf, I know there is some space taken up by the drivers, crossover, bracing, etc... Should I just pick a nominal 5cf and let the rest work itself out, or should I try to calculate the volume of anything that takes away from the cabinet volume? Or if I start with 4.8cf I could end up with a little less but probably still more than the 4cf that the designer liked.
Generally speaking, yeah, BSC will be incorporated into the crossover design, usually by making the low pass inductor bigger. With a series crossover like the 2400, it is more complex, as all the parts interact.
Some companies do simply ignore it, whether through ignorance or inattention.
Slight changes in volume are not that critical WRT to the general loading of the driver. But, when you add a port for tuning, it really should be as precise as possible. The mass of air directly affects the port tuning frequency. You can't guess at this. Perhaps this weekend I'll have some time to run a sim for you, since no one else is volunteering....
I started looking at quick volume calculations and realized how sensitive those really are. I'll try to stick to greater than 4 cu-ft since that seems like a very attainable volume for the design and it should be in a sweet spot for the D123. It seems like the primary function of the MLTL design is the height related to quarter-wave tuning. Am I correct that 39" would be tuned for ~40Hz? I wouldn't mind the driver being up a little higher than that since we have taller furniture in general. It's going in a small house too, so the smaller I can make the footprint, the better.
No hurry on any simulations. I would appreciate it, but it may take a little while before I'm putting blades to wood. I have a few material and design choices I'd like to explore too. Things like Bamboo (or other exotic wood or veneer) sides with leather or high quality vinyl covering MDF on the front, top and back. I have a couple ideas of how to incorporate an access panel to deal with those rear-mount only drivers too.
No hurry on any simulations. I would appreciate it, but it may take a little while before I'm putting blades to wood. I have a few material and design choices I'd like to explore too. Things like Bamboo (or other exotic wood or veneer) sides with leather or high quality vinyl covering MDF on the front, top and back. I have a couple ideas of how to incorporate an access panel to deal with those rear-mount only drivers too.
Alright, I have a couple of ideas for getting around my road blocks.
Turning the D123 into a front mount driver isn't hard. I can use a ring of ~1/8" aluminum or stainless bolted to the mounting surface of the driver's basket to extend the mounting surface outside of the basket diameter. The hole in the baffle just needs to be large enough for the whole basket to go through. There are only four mounting points on the driver, though. If I need to, I could add a clamp system to the back of the baffle and effectively sandwich the driver into the baffle.
If I want to bring the driver height up without effecting the MLTL tuning, there are at least two options. I can always build the cabinet taller and put in a 'bottom' at the tuning height. Or if I want to move the midpoint between the two drivers up, I can mount the 075 tweeter in a separate enclosure on the top. It could look continuous or be as small as I want to make it.
I'd like to use hardwood for the top and sides. I think Bamboo is out. It's interesting and it was effectively a plywood, so it's probably stable. I just want a darker wood with more finishing options. Veneer is out too. The cost seems too high for what it is. It looks like I can go with solid hardwoods for only a little more.
Turning the D123 into a front mount driver isn't hard. I can use a ring of ~1/8" aluminum or stainless bolted to the mounting surface of the driver's basket to extend the mounting surface outside of the basket diameter. The hole in the baffle just needs to be large enough for the whole basket to go through. There are only four mounting points on the driver, though. If I need to, I could add a clamp system to the back of the baffle and effectively sandwich the driver into the baffle.
If I want to bring the driver height up without effecting the MLTL tuning, there are at least two options. I can always build the cabinet taller and put in a 'bottom' at the tuning height. Or if I want to move the midpoint between the two drivers up, I can mount the 075 tweeter in a separate enclosure on the top. It could look continuous or be as small as I want to make it.
I'd like to use hardwood for the top and sides. I think Bamboo is out. It's interesting and it was effectively a plywood, so it's probably stable. I just want a darker wood with more finishing options. Veneer is out too. The cost seems too high for what it is. It looks like I can go with solid hardwoods for only a little more.
I had some time to do a virtual prototype with Solidworks today. The baffle does need to get a bit wide! I ended up with internal dimensions of 39"H x 15"W x 14.25"D.
I placed the drivers and port at arbitrary locations for now.
Here's a view with the baffle made translucent. The baffle will bolt to the rest of the cabinet.
I haven't added any bracing, but I don't see much in this type of box. I was thinking of just bracing the corners and not having other internal framing. I'm not sure what is best with this type of box design.
The back of the baffle.
And all the parts exploded!
That front part that looks like the timing cover on an engine would be aluminum, covered in a high quality, leather-like vinyl. The D123 is the large driver. You recognize the conventional main 3/4" MDF baffle -also likely covered in leather-like vinyl. The hole in the baffle for the D123 is a thru-hole for the entire driver's diameter. Those funny pieces behind the baffle that seem to intersect the D123 are my clamping system. The D123 is a rear-mount-only driver. With this setup the driver would end up recessed by the 1/8" aluminum plus the vinyl thickness, rather than being sunk in by the 3/4" baffle thickness. I have mounts for the 075 tweeter, so I didn't bother modeling the mounting system for that driver.
Any thoughts on this? It seems a little short, but I'm warming up to the idea of some kind of stands.
I placed the drivers and port at arbitrary locations for now.
Here's a view with the baffle made translucent. The baffle will bolt to the rest of the cabinet.
I haven't added any bracing, but I don't see much in this type of box. I was thinking of just bracing the corners and not having other internal framing. I'm not sure what is best with this type of box design.
The back of the baffle.
And all the parts exploded!
That front part that looks like the timing cover on an engine would be aluminum, covered in a high quality, leather-like vinyl. The D123 is the large driver. You recognize the conventional main 3/4" MDF baffle -also likely covered in leather-like vinyl. The hole in the baffle for the D123 is a thru-hole for the entire driver's diameter. Those funny pieces behind the baffle that seem to intersect the D123 are my clamping system. The D123 is a rear-mount-only driver. With this setup the driver would end up recessed by the 1/8" aluminum plus the vinyl thickness, rather than being sunk in by the 3/4" baffle thickness. I have mounts for the 075 tweeter, so I didn't bother modeling the mounting system for that driver.
Any thoughts on this? It seems a little short, but I'm warming up to the idea of some kind of stands.
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Greets!
I've done lots of MLTLs for vintage Altec, JBL, etc., as well as modern drivers for others and ideally we usually want the HF to be at ~seated ear height [or above] plus we want the woofer to be down from the closed end [top] at some odd harmonic of the pipe with ~ 1/3 or 2/5 being the norm for smoothest overall response; ditto the vent up from the open end [bottom] if not at the extreme bottom, so recalculate the cab's internal height based on these criteria with a minimum 48" and preferably 60+" to get good 1/4 WL TL loading of the vent.
This pipe loading effectively lowers [Fb] for a given vent length or allows a shorter vent for a given tuning, often allowing a larger vent to be used for even more acoustic efficiency with these older, high Vas drivers, so often for a low tuning, a much larger vent area than a typical box program calculates is required.
Also, ideally we want the cab's cross sectional area [CSA] to be a golden or acoustic ratio [see room acceptable ratios] to keep internal damping to a minimum for max practical acoustic efficiency.
WRT max net volume [Vb] and Fb, the various sealed, reflex 'rules' don't apply, so having it exceed the driver's Vas is often desirable, especially if Qts is > 0.4; ditto tuned to < Fs is normally desirable if not driven with a high output impedance.
Indeed, my default MLTL design for this driver is 60" high, 28.5" wide [i.d.], ~17.4 ft^3 [gross]/38 Hz with a 10" dia. [or = area slot] vent. Placed very close to a wall, this modestly rolled off, highly damped response will typically handle all but the <32 Hz BW at piano bar levels in a typical HIFI app.
By the same token, if you can use corner loaded, triangular shaped cabs, then net Vb can be reduced considerably and still get the same output.
GM
I've done lots of MLTLs for vintage Altec, JBL, etc., as well as modern drivers for others and ideally we usually want the HF to be at ~seated ear height [or above] plus we want the woofer to be down from the closed end [top] at some odd harmonic of the pipe with ~ 1/3 or 2/5 being the norm for smoothest overall response; ditto the vent up from the open end [bottom] if not at the extreme bottom, so recalculate the cab's internal height based on these criteria with a minimum 48" and preferably 60+" to get good 1/4 WL TL loading of the vent.
This pipe loading effectively lowers [Fb] for a given vent length or allows a shorter vent for a given tuning, often allowing a larger vent to be used for even more acoustic efficiency with these older, high Vas drivers, so often for a low tuning, a much larger vent area than a typical box program calculates is required.
Also, ideally we want the cab's cross sectional area [CSA] to be a golden or acoustic ratio [see room acceptable ratios] to keep internal damping to a minimum for max practical acoustic efficiency.
WRT max net volume [Vb] and Fb, the various sealed, reflex 'rules' don't apply, so having it exceed the driver's Vas is often desirable, especially if Qts is > 0.4; ditto tuned to < Fs is normally desirable if not driven with a high output impedance.
Indeed, my default MLTL design for this driver is 60" high, 28.5" wide [i.d.], ~17.4 ft^3 [gross]/38 Hz with a 10" dia. [or = area slot] vent. Placed very close to a wall, this modestly rolled off, highly damped response will typically handle all but the <32 Hz BW at piano bar levels in a typical HIFI app.
By the same token, if you can use corner loaded, triangular shaped cabs, then net Vb can be reduced considerably and still get the same output.
GM
Well 48" would be easy with a 4'x8' sheet of MDF! Something as big as 60" would be tough, but probably workable. I have a circular saw and a decent straight edge for up to 48" cuts. Home Depot could cut the full length if I went taller than 48". These are going in a house with limited space, though. Keeping the bulk down is a priority.
I like the taller cabinet idea to bring the drivers up! I can put the drivers anywhere at this point. I picked that initial configuration to put the D123 closer to ear level since it does the 'heavy lifting' up to ~2500Hz (with the N2400). It would be easy to flip that orientation with a taller cabinet. I'm not locked in on any particular design at this point. I have the drivers and they sound good, but the cabinets they are in are too small, old and leaky. I put some pictures of the drivers and cabinets in a thread on the Lansing Heritage site a little over a year ago if anyone wants to check those out.
Maybe I need to dive into the math more seriously. I was hoping not to have to go too deep down the rabbit hole since this isn't a primary hobby for me. I must have made a mistake with the numbers that gave me 40Hz at 39". Are we just using a basic wave equation (Speed = Freq x Wavelength), or something more complex here? I have a lot more reading to do, apparently. I found the T/S parameters of the D123 here, from a thread on Audiokarma talking about the same drivers in an MLTL enclosure. Unfortunately that thread fizzled out.
It's funny that you brought up triangluar shaped cabinets. My first thought when I saw 48-60+ inches was that I could reduce the volume by making them a triangluar cross-section.
Thinking about triangluar speakers also brought up another interesting thought about porting. One of my favorite speakers is the Sonus Faber Olympica II. They have some kind of special magic going on that I haven't heard with any other speaker. I think they are considered a bass reflex design, but they use a long skinny vent at the back of the lyre shaped cabinet. With an MLTL, could you create a long, skinny port like that and get some kind of a frequency distilling effect? I'm not sure how it could really be accomplished, but my thought was that shorter wavelengths would load the port at shorter distances, longer wavelengths would load the whole port. More acoustic physics to dig into!
I like the taller cabinet idea to bring the drivers up! I can put the drivers anywhere at this point. I picked that initial configuration to put the D123 closer to ear level since it does the 'heavy lifting' up to ~2500Hz (with the N2400). It would be easy to flip that orientation with a taller cabinet. I'm not locked in on any particular design at this point. I have the drivers and they sound good, but the cabinets they are in are too small, old and leaky. I put some pictures of the drivers and cabinets in a thread on the Lansing Heritage site a little over a year ago if anyone wants to check those out.
Maybe I need to dive into the math more seriously. I was hoping not to have to go too deep down the rabbit hole since this isn't a primary hobby for me. I must have made a mistake with the numbers that gave me 40Hz at 39". Are we just using a basic wave equation (Speed = Freq x Wavelength), or something more complex here? I have a lot more reading to do, apparently. I found the T/S parameters of the D123 here, from a thread on Audiokarma talking about the same drivers in an MLTL enclosure. Unfortunately that thread fizzled out.
It's funny that you brought up triangluar shaped cabinets. My first thought when I saw 48-60+ inches was that I could reduce the volume by making them a triangluar cross-section.
Thinking about triangluar speakers also brought up another interesting thought about porting. One of my favorite speakers is the Sonus Faber Olympica II. They have some kind of special magic going on that I haven't heard with any other speaker. I think they are considered a bass reflex design, but they use a long skinny vent at the back of the lyre shaped cabinet. With an MLTL, could you create a long, skinny port like that and get some kind of a frequency distilling effect? I'm not sure how it could really be accomplished, but my thought was that shorter wavelengths would load the port at shorter distances, longer wavelengths would load the whole port. More acoustic physics to dig into!
I'm having a tough time figuring out where to start with these speakers. This is what stalled me out a year ago and why these drivers have sat unused for ~20 years.
I can make a basic speaker - put drivers in a box and they work. What I'm looking for is guidance on how to get the best effect out of these drivers. Could someone help me out with this?
I can make a basic speaker - put drivers in a box and they work. What I'm looking for is guidance on how to get the best effect out of these drivers. Could someone help me out with this?
I think GM just did give you a detailed recipe for getting the best possible effect...
If that's too big, either 6.8 cuft (max flat) or the originally proposed 4.8 cu ft would be a big improvement over what you have now.
The math for a BR is simple, but the math for an ML-TL is not, and that's why computers are used. Check out quarter-wave.com for additional education. However, understanding what's going on and some decent rules of thumb born from experience go a long way.
Anyhow, the enclosure length does not set the box resonance. Fb is set mostly by the port size and the volume. The pipe action of a column reflex/ML-TL adds some oomph in the midbass region, which can compensate for what would normally be 'too big' for a BR.
If that's too big, either 6.8 cuft (max flat) or the originally proposed 4.8 cu ft would be a big improvement over what you have now.
The math for a BR is simple, but the math for an ML-TL is not, and that's why computers are used. Check out quarter-wave.com for additional education. However, understanding what's going on and some decent rules of thumb born from experience go a long way.
Anyhow, the enclosure length does not set the box resonance. Fb is set mostly by the port size and the volume. The pipe action of a column reflex/ML-TL adds some oomph in the midbass region, which can compensate for what would normally be 'too big' for a BR.
I was getting frustrated by the different suggestions and not feeling like I'm getting sufficient answers on ideas (whether here or what I'm trying to read elsewhere). Some rules of thumb seem to break down with these drivers and my experience is limited, at best. This isn't the first place I have asked about trying to build boxes for these drivers. I guess planning for the volume of a bass reflex box makes the most sense and if I get some MLTL effects because of other design parameters, that will just be a bonus.
So here's where I'll start: I want to keep the drivers up off the floor, so I'm avoiding the typical vintage box designs for these drivers. I don't care if the woofer or tweeter is on top. I know the typical rule of thumb is to keep the tweeter at or slightly above ear level, so that's anywhere from 39-47 inches where these will likely end up (~10'x10' office - height numbers come from sitting in my office chair or futon in the room). Since plywood and MDF comes in 4'x8' sheets, I'll stick with a 48" dimension as a maximum for any one side. I could make the inside 48" high, but I'd like to hide the bottom, so it'll be more like 47.25" internal height.
If I use 1/3 of the height for placing the D123, that's 15.75" from the top of the front panel.
I saw a rule of thumb for spacing drivers on this site that says, "You should also keep the centers of 2 drivers within the length of a wave at the crossover frequency." At 2500 Hz, that is approximately 5.43". The radius of the D123 is greater than that already. Should I stick to some multiple of that number, or just place the 075 at some arbitrary distance above the D123?
I already worked out that I need the front of the speaker baffle to be at least 15" wide. I might be able to tighten that up to 14". I really don't want to go much wider than 15" because of the small room size. That already makes the speaker 16.5" wide if I use 3/4" thick wood.
I'm open to different shapes. A rectangular box is going to be easiest for me to build. Unless there's a really compelling reason not to, I'll probably just build the box with a square cross section. I can always add bracing and batting to combat resonances, right? I'm not sure I can get accurate, repeatable angular cuts with my circular saw or router unless someone can clue me in on a good trick. Then I'd be open to making some kind of trapezoid shape.
I don't know what to do about porting. I'd like to do something different than the typical round tube port. I'm tempted to port out the bottom or do a long slot port on one of the rear sides, just to do something different. How much does it matter, really?
So here's where I'll start: I want to keep the drivers up off the floor, so I'm avoiding the typical vintage box designs for these drivers. I don't care if the woofer or tweeter is on top. I know the typical rule of thumb is to keep the tweeter at or slightly above ear level, so that's anywhere from 39-47 inches where these will likely end up (~10'x10' office - height numbers come from sitting in my office chair or futon in the room). Since plywood and MDF comes in 4'x8' sheets, I'll stick with a 48" dimension as a maximum for any one side. I could make the inside 48" high, but I'd like to hide the bottom, so it'll be more like 47.25" internal height.
If I use 1/3 of the height for placing the D123, that's 15.75" from the top of the front panel.
I saw a rule of thumb for spacing drivers on this site that says, "You should also keep the centers of 2 drivers within the length of a wave at the crossover frequency." At 2500 Hz, that is approximately 5.43". The radius of the D123 is greater than that already. Should I stick to some multiple of that number, or just place the 075 at some arbitrary distance above the D123?
I already worked out that I need the front of the speaker baffle to be at least 15" wide. I might be able to tighten that up to 14". I really don't want to go much wider than 15" because of the small room size. That already makes the speaker 16.5" wide if I use 3/4" thick wood.
I'm open to different shapes. A rectangular box is going to be easiest for me to build. Unless there's a really compelling reason not to, I'll probably just build the box with a square cross section. I can always add bracing and batting to combat resonances, right? I'm not sure I can get accurate, repeatable angular cuts with my circular saw or router unless someone can clue me in on a good trick. Then I'd be open to making some kind of trapezoid shape.
I don't know what to do about porting. I'd like to do something different than the typical round tube port. I'm tempted to port out the bottom or do a long slot port on one of the rear sides, just to do something different. How much does it matter, really?
In theory a larger diameter circular port will have the best Q and lowest noise, but as long as your area is pretty big other shapes will probably work about as well.
The trouble with making systems out of some of these older drivers is that they are way too far removed from modern Thiele/Small designs. I tried doing something with my dads D130 and the Q was so low that you could never do a useful alignment. It was either a larger box and a step down alignment or squeeze it into a compact box for a high cutoff but maximally flat alignment. I suspect the D123 is similar (lots of magnet and a light cone, better for guitar speakers than HiFi woofers).
This might be a place where a vintage flavored system using an old variable damping tube amp might be fun. High output impedance might get you to flatter response.
David
I read somewhere that the D123 was related to a guitar amplifier speaker, but somehow modified for HiFi. You just touched on one of my fears though. Could I build this big box and find out that modern bookshelf speakers will give better quality sound and give deeper bass response? That's the biggest problem with their current configuration. They sound good in the upper frequency range, but they disappear below anything even related to the upper bass range.
It's the internet. Of course you will get answers that are all over the place, especially if you ask on multiple forums. Experience levels vary from weeks to decades. Speaker design isn't trivial and there's lots to it. You can't expect people to educate newbies to the hobby with one post. None of us would have any time left....
Anyhow, it is important that the woofer be at about 1/3 from the top. So put the tweeter on top. The vent shape doesn't make a huge difference in most cases, but circular is most efficient. Vent length is critical.
Slot vents (AKA Fulmer vents) can be helpful in some cases, but I don't see a huge benefit here. At any rate you would make it the same or slightly larger than an equivalent circular cabinet vent. Note that a slot vent is only going to work with an enclosure that is big enough to require only a panel depth vent.
Anyhow, it is important that the woofer be at about 1/3 from the top. So put the tweeter on top. The vent shape doesn't make a huge difference in most cases, but circular is most efficient. Vent length is critical.
Slot vents (AKA Fulmer vents) can be helpful in some cases, but I don't see a huge benefit here. At any rate you would make it the same or slightly larger than an equivalent circular cabinet vent. Note that a slot vent is only going to work with an enclosure that is big enough to require only a panel depth vent.
I can appreciate that. I don't like the newbie position either. I know enough to realize that there are pitfalls in speaker design, but I don't know enough to always know what questions to ask or where to look for the answers, so I end up wasting a lot of time too. I was hoping to leverage some forum knowledge and experience to give me a head start. Or at least get some input on my own design ideas.
I haven't seen a good explanation of how the Zu/Tekton guys get away with woofers at the top of the box in their 2-way designs, rather than 1/3 of the way down.
How about some input on tweeter spacing from the woofer? Is arbitrary okay or is there some relationship I haven't seen yet?
I haven't seen a good explanation of how the Zu/Tekton guys get away with woofers at the top of the box in their 2-way designs, rather than 1/3 of the way down.
How about some input on tweeter spacing from the woofer? Is arbitrary okay or is there some relationship I haven't seen yet?
IMO they don't get away with it.
Like I said I don't mind running a few sims of the proposed systems for you when I have a moment. You said you weren't in a hurry so I didn't rush.
Tweeter to woofer distance - the general guideline is 1/3 or 1/2 wavelength at the crossover frequency, depending on who you ask. This rule is often broken. Put them as close as you can and don't worry about it IMO.
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