Jim Posted December 14, 2014 Share Posted December 14, 2014 I am looking to see what the difference in sound will be with using speakers with a passive radiator vs. ported. I am narrowing down a tube amp for a dedicated 2 channel system. I am contemplating using RB-15's,25's,35's,(RF-25's if I do my living room), or something along the lines with passive radiators.The amp will most likely have 10 watts per channel. I am still researching and what it looks like is that the passive radiators have a lower HZ rating than ported.Is that correct? Or does it give bass a tighter response? I will most likely have the speakers on my desk (if I don't do the RF-25's), or in a small seating area of about 5-6 feet away. If on my desk, the speakers will be anywhere from 6-12 inches from the wall (rear), and if in a designated seating area about 12-24 inches from the wall(rear).The room is 14 wide and 24 long, and the speakers if not on the desk will be 7-8 feet from the sides. So I don't know if I go ported if I should go rear port, or front port,or if I should go with the passive radiators and call it a day.At this point it will mostly be cd listening as I need to get a new turntable for what vinyl I have left.I do have a bunch of cassettes, but don't know if I should even bother with them,or if I should convert them to digital through my computer. So my thought process is I'm either doing Reference, or KG (anything lower than the 2.5). I don't think doing heritage at this point is doable for me,but maybe in the future. Any help is appreciated. 1 Quote Link to comment Share on other sites More sharing options...
ryanm84 Posted December 14, 2014 Share Posted December 14, 2014 I've had KG4s since 1990. Passive radiator speaker needs corner placement to enhance bass. I would guess you might have slightly more placement options with ports. Especially front ports. 1 Quote Link to comment Share on other sites More sharing options...
jjptkd Posted December 14, 2014 Share Posted December 14, 2014 Passive radiators are ports. Quote Link to comment Share on other sites More sharing options...
Ski Bum Posted December 14, 2014 Share Posted December 14, 2014 Passive radiators and ports are essentially similar. They are both reflex alignments, and share the same behaviors specific to such enclosures. and jjptkd beat me to it. Quote Link to comment Share on other sites More sharing options...
Jim Posted December 14, 2014 Author Share Posted December 14, 2014 So basically the radiators will give a lower response on bass as long as they are set in a corner vs. the open ported speakers, and open ported speakers will give more options on placement with rear ported speakers giving a better response rate than front ported as long as they are placed by a rear wall. I know it's also subjective to ears,so it will vary. Quote Link to comment Share on other sites More sharing options...
moray james Posted December 14, 2014 Share Posted December 14, 2014 passive radiators generate lower distortion than a vent reflex does but they cost more, a lot more. They function the same way as a reflex vent. Make your vents larger they will have lower distortion but they will also be a lot longer so size will kill you at some point. Best regards Moray James. Quote Link to comment Share on other sites More sharing options...
russ69 Posted December 14, 2014 Share Posted December 14, 2014 I find it difficult to make general statements on loudspeaker design. There are many ways to skin a cat, and some executions of designs are better than others. Quote Link to comment Share on other sites More sharing options...
Rivernuggets Posted December 14, 2014 Share Posted December 14, 2014 With what you're looking for, small Reference bookshelves or KG 2.5s or smaller, just pick up a pair here and there as they come down the used market. Compare and keep what you like. It won't break the bank and you'll get to know your preferences. 1 Quote Link to comment Share on other sites More sharing options...
Ski Bum Posted December 14, 2014 Share Posted December 14, 2014 (edited) So basically the radiators will give a lower response on bass as long as they are set in a corner... No. The use of a reflex enclosure is simply a design choice to meet specific goals in terms of bass extension/cab size (deeper bass per cab volume vs. sealed alignment). That's it. A critical thing to note is the steeper inherent roll-off of reflex, as that has ramifications when it comes to corner loading. Here is a good explanation of reflex enclosures. Edited December 14, 2014 by Ski Bum Quote Link to comment Share on other sites More sharing options...
Skelt Posted December 14, 2014 Share Posted December 14, 2014 I took a pair of Tangent 400s (front ports), installed passives from KG4s and plugged the ports. It helped the lower bass responce and extension but the speakers dont image as well as befere the changes. I think there must have been some midrange leaking through the ports. Quote Link to comment Share on other sites More sharing options...
Moderators dtel Posted December 14, 2014 Moderators Share Posted December 14, 2014 I always thought passive radiators were kind of a cross between sealed and ported as far as performance and sound quality goes. Not quite as tight of a bass as sealed but more bass similar to ported. Almost like a bigger cabinet for a sealed box as far as tuning goes............it's what I was thinking, which does not make it correct. ? Quote Link to comment Share on other sites More sharing options...
ClaudeJ1 Posted December 14, 2014 Share Posted December 14, 2014 (edited) Having worked on a ported Jube-like drone, I was testing various options, inclucing a Klipsch 12" Passive Radiator. With a fixed volume in the back chamber, and a 12" diameter to work with, the only variable was mass and stiffness of the passive. That experiment, done outdoors with a close miking technique was quite revealing. You can't just do this sort of thing without instruments and control of parameters, including the driving source (active woofers) characteristics, box volume, etc. It's a lot harder to get right thaN you think. Same is true for horn design. I went throught about 50 differenct bass horn model "tweaks" before I ended up with the Quarter Pie horn, and that was 80% based on an existing Klipsch MWM design after talking to Gary Gillum, the former Klipsch chief engineerco-patent holder with PWK about it. It's hard work and can be rewarding but you will be working for about 10 cents an hour, making a lot of sawdust/firewood, and build a stock of not-so-useful drivers in the process. Especially when you find out that many drivers vAry considerably from their published Thiele Small parameters when you actually measure them. Edited December 15, 2014 by ClaudeJ1 1 Quote Link to comment Share on other sites More sharing options...
Ski Bum Posted December 14, 2014 Share Posted December 14, 2014 I always thought passive radiators were kind of a cross between sealed and ported as far as performance and sound quality goes. Not quite as tight of a bass as sealed but more bass similar to ported. Between sealed and reflex is a weird bird called aperiodic. Aperiodic enclosures are basically a leaky sealed box (and can be modeled as such in those speaker design programs), but the leak/port is stuffed with enough damping material to quell the resonant peak of the port. An example would be those old Dynaco A25. Quote Link to comment Share on other sites More sharing options...
mustang guy Posted December 14, 2014 Share Posted December 14, 2014 (edited) Designing a passive system is a bit more complex since you use the Thiele / Small parameters with the passive as well as the driver. A port can be very precise, but Thiele Small specs on the radiators can vary due to construction differences, just like with drivers. I have not designed an enclosure for a passive speaker for this very reason. I just don't have the time and budget for it. If you are just buying one pre-made, then one consideration not mentioned is that if your passive gets damaged, you might not be able to find a replacement. Edited December 14, 2014 by mustang guy 1 Quote Link to comment Share on other sites More sharing options...
ClaudeJ1 Posted December 14, 2014 Share Posted December 14, 2014 f you are just buying one pre-made, then one consideration not mentioned is that if your passive gets damaged, you might not be able to find a replacement. Good point, which is why I installed grilles over my ex-girlfriend's Fortes (don't ask). Quote Link to comment Share on other sites More sharing options...
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