Hi there,
I'm relatively new to the world of pro audio. I've built a pair of subs and a pair of kick bins that I absolutely love, but I've been using a pretty ratty pair of Eons as the mid tops. I wanted to change that, and threw together a pair of cabinets using the extra birch I had from the kicks and subs. I've attached an image to give you an idea of what they'll eventually look like.
Each cabinet will contain two Eminence Delta 10A speakers sharing the same enclosure volume of almost exactly one cubic foot (and a compression driver/horn in a separate chamber above). I got a great Ebay deal on these four drivers with the intent of building something comparable to the "Small Vented Cab" described by Eminence here (except with two drivers and roughly twice the enclosure volume): https://www.parts-express.com/pedocs/more-info/290-412--eminence-delta-10a-cabinet-design.pdf
My dilemma is that I can't find anywhere sane to put the two 3" ports! My only real solution would be to mount them in the back of the trapezoid, but I've read that ports shouldn't be behind drivers if you can help it. I've also looked at using up to four 2.5" ports on the baffle, but the length of these would be very short to maintain the 95hz tuning frequency of the box I'm going for, and I've read that air velocity is a concern.
One thing worth noting is that I'm designing these to be high passed at 200hz--I think having them play down to 125hz as is possible in the linked Eminence cabinet design might be nice if I need it (say if I were to pair it with just my subs instead of my subs + kick bins).
Sadly, I don't have a windows machine so I can't get WinISD. I'm hoping someone could kindly help me with modeling port air velocity with the four 2.5" (or even four 2") ports (maintaining a 95hz tuning frequency for the 1 cubic foot box) to see if it's untenable at any point 200hz or above.
Alternatively--since the two deltas will be used chiefly for midrange (and not being able to go down to 125hz wouldn't really be a dealbreaker)--should I consider just leaving their enclosure sealed with a volume of 1 cubic foot? I've seen something similar done in this plan, here: Speakerplans.com
If someone is able to model excursion and frequency response in particular, that would be amazing. I'd also love to hear any general opinions regarding vented vs sealed enclosures for PA midrange.
I'm really thrilled to be building speakers and will be certain to keep this community apprised of my progress!
I'm relatively new to the world of pro audio. I've built a pair of subs and a pair of kick bins that I absolutely love, but I've been using a pretty ratty pair of Eons as the mid tops. I wanted to change that, and threw together a pair of cabinets using the extra birch I had from the kicks and subs. I've attached an image to give you an idea of what they'll eventually look like.
Each cabinet will contain two Eminence Delta 10A speakers sharing the same enclosure volume of almost exactly one cubic foot (and a compression driver/horn in a separate chamber above). I got a great Ebay deal on these four drivers with the intent of building something comparable to the "Small Vented Cab" described by Eminence here (except with two drivers and roughly twice the enclosure volume): https://www.parts-express.com/pedocs/more-info/290-412--eminence-delta-10a-cabinet-design.pdf
My dilemma is that I can't find anywhere sane to put the two 3" ports! My only real solution would be to mount them in the back of the trapezoid, but I've read that ports shouldn't be behind drivers if you can help it. I've also looked at using up to four 2.5" ports on the baffle, but the length of these would be very short to maintain the 95hz tuning frequency of the box I'm going for, and I've read that air velocity is a concern.
One thing worth noting is that I'm designing these to be high passed at 200hz--I think having them play down to 125hz as is possible in the linked Eminence cabinet design might be nice if I need it (say if I were to pair it with just my subs instead of my subs + kick bins).
Sadly, I don't have a windows machine so I can't get WinISD. I'm hoping someone could kindly help me with modeling port air velocity with the four 2.5" (or even four 2") ports (maintaining a 95hz tuning frequency for the 1 cubic foot box) to see if it's untenable at any point 200hz or above.
Alternatively--since the two deltas will be used chiefly for midrange (and not being able to go down to 125hz wouldn't really be a dealbreaker)--should I consider just leaving their enclosure sealed with a volume of 1 cubic foot? I've seen something similar done in this plan, here: Speakerplans.com
If someone is able to model excursion and frequency response in particular, that would be amazing. I'd also love to hear any general opinions regarding vented vs sealed enclosures for PA midrange.
I'm really thrilled to be building speakers and will be certain to keep this community apprised of my progress!
Attachments
This is an awesome suggestion. I'll play with the arrangements a little bit and see where this gets me!
Ports don't have to be circular although I'm not sure how to do the math for an "equivalent" triangular or square port. I've just been using online calculators and am not sure of the math.
I'm kind of asking this as well lol. Will ports help SPLs/driver excursion/anything else at my intended frequency range at all? Or could I just confidently go sealed at this volume?
Ports can be almost any shape as long as the area is the same. So if your ports are 3” diameter, that’s 7 square inches. You could go square at 2.6” x 2.6” or 2” x 3.5” etc.
I said almost any shape because I don’t think it works with really long thin ports, but the ones above will be fine. You should use the same length as the round ones too
Brian
So say, for instance, I got a pair of these ports: Port Tube Triangular
These have a claimed area of 4.5 square inches. If I made them them the same length as two 4.5" circular ports and stuck them in the same box, they'd have roughly the same effect on that box's tuning frequency?
You need to match the area. On the web page:
Port area is 4-1/2 square inches, approximates 2-3/8" diameter port.
Brian
I disagree.
While the ports may be acoustically inactive, they'll still allow airflow for thermal convection. Sealed boxes are bad news for high-power systems.
I'd put two ports on the back, one above the top driver and the other below the bottom driver.
Chris
Ok cool--I was thinking I may want to give the mid tops the ability to go down to ~120 hz to take over work from the kicks (not the subs), but it's really unlikely I'd find myself in that situation now that I think about it.
So generally speaking, ports wouldn't help at all with SPLs at all at higher frequencies?
I'm going to see if I can use a friend's PC to get WinISD up and running and try to model some different scenarios with this given box volume and driver combo.
If I went that route, would it be a problem if any of the cone was visible through either port? I think I read somewhere that you can lose some midrange when this happens.
Actually now that you say it I agree, I was thinking strictly in terms of acoustics. And I like your idea for port locations it would promote some airflow through the cabinet with heat rising off the drivers.
I would second Chris suggestion that ports are needed for cooling, they will have little effect on the response if the box is used far above the tuning frequency. I have been there and done PA with sealed boxes and for the first hour or so its fine but over time the air inside the box gets hot and the magnets get hot which causes a drop in efficiency... which then causes you to up the power.... which causes more heating. Perhaps its fine if your using FLH or another high efficiency alignment but if your going to be approaching the power limits of the driver there are issues.
My other suggestion is you might want to try alternatives to the round metal grills or use more than 4 grill clamps on them as I have found such grills to be an endless source of trouble to the point where I design speakers not to use grills at all as I find fabrication of an effective grill too expensive and difficult. Usually they are made of too thin metal so over time they get pushed in and start to hit the driver cone. Another issue is that they undo themselves over time due to relaxation of the foam or vibration and start to buzz and then when you tighten them they deform and start to hit the cone! it would be better to use perforated metal and build a proper frame for it to sit in although such grills are surprisingly expensive and great care has to be take to avoid buzzing.
My other suggestion is you might want to try alternatives to the round metal grills or use more than 4 grill clamps on them as I have found such grills to be an endless source of trouble to the point where I design speakers not to use grills at all as I find fabrication of an effective grill too expensive and difficult. Usually they are made of too thin metal so over time they get pushed in and start to hit the driver cone. Another issue is that they undo themselves over time due to relaxation of the foam or vibration and start to buzz and then when you tighten them they deform and start to hit the cone! it would be better to use perforated metal and build a proper frame for it to sit in although such grills are surprisingly expensive and great care has to be take to avoid buzzing.
RE Grills:
I don't like the round grills either I think they look a bit ameture... no offence to the OP if that is all he could find. But here on this side of the pond there are other options that aren't that expensive, for example Reliable Hardware will cut and bend the edges(if required) of sheets of expanded metal in various weights producing professional full coverage grills of any dimensions you like.
On smaller cabs I have never had any problem with grills rattling or resonating, on subs yes but adding some rubber isolators in strategic places is enough to bring that under control.
I don't like the round grills either I think they look a bit ameture... no offence to the OP if that is all he could find. But here on this side of the pond there are other options that aren't that expensive, for example Reliable Hardware will cut and bend the edges(if required) of sheets of expanded metal in various weights producing professional full coverage grills of any dimensions you like.
On smaller cabs I have never had any problem with grills rattling or resonating, on subs yes but adding some rubber isolators in strategic places is enough to bring that under control.
Last edited:
if ports are required for convection cooling in high power applications why doesn't a product like this include them?
KF730 - EAW: Eastern Acoustic Works
KF730 - EAW: Eastern Acoustic Works
Dunno. Maybe they found there's enough additional steel (line array rigging) that the cabinets can expel heat via conduction.
Looking at the graphs, the pair of 10" drivers really aren't doing much, especially if a LR24 100Hz highpass was applied, so perhaps they don't see particularly high power levels.
Chris
Looking at the graphs, the pair of 10" drivers really aren't doing much, especially if a LR24 100Hz highpass was applied, so perhaps they don't see particularly high power levels.
Chris
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.