bodcaw boy Posted November 8, 2006 Share Posted November 8, 2006 Roy, Can you clarify where you would add the foam, are you talking about on the front that faces into the room? Rigma yes sir....... boy!! Quote Link to comment Share on other sites More sharing options...
Deang Posted November 8, 2006 Share Posted November 8, 2006 A lot of great info over the last couple of pages, thankfully most of it is easy to digest. Quote Link to comment Share on other sites More sharing options...
chops Posted November 8, 2006 Share Posted November 8, 2006 Speaking of alternative designs, has anyone ventured into doing an open baffle design at all with dual 15's per channel? With the right drivers, one can easily match the sensitivity ( <105dB 1w/1m) of the squawker, get excellent, clean midrange up to 600Hz and natural, ultra-fast and dynamic bass to an extent before implementing active EQ'ing to compensate for the dipole roll-off in the lowest octaves. This is exactly what I have in the works at the moment. I'm doing some research just to "freshen up" before jumping in head first. This ought to be some fun times coming up soon! [] what kind of directivity (coverage angle) are you going to go with? I'm not sure I follow. If you're referring to the "sweet spot", dipole loudspeakers generally have a broader area rather than just a "spot". well every direct radiator has a characteristic coverage pattern. usually about from low freq to high, it starts off wide dispersion that narrows down to about 120 degree for a certain bandwidth then beams down to about 90 degrees over a certain bandwidth and then starts to collapse. where it starts to collapse is determined by the voice coil diameter. so say you are going to use 15". it is 120 degree from about 300 to about 600 then 90 degrees from 600 to about 1400 hz for a 3" voice coil. this is all approximate since i have slept since then. putting the woofers one on top of another with literally not much space between the frames means that the woofers will create a bubble (d'appolito) that resembles a coverage pattern of about 90 to 70 degrees at about 900 hz. so you could essentially have 90 degrees to about 300 hz. now take a cabinet without a back and whose sides, top and bottom are about 40" deep and you should be able to start dipole action about 300-400 hz. now you could extend the 90 degree coverage pattern well below 100 hz as long as you can keep the amplitude up. is that what you meant about open baffle? or are you going to mount dual 15" on the back as well to make a dipole in an box? boy!! Hi Roy, This is what I mean by dipole (open baffle)... The drivers being used will most likely have a 2.5" VC. They will be crossed over at 600Hz to the 511B/902-8B and will be augmented on the bottom by an EQ to compensate for the dipole roll-off. it is open back... okay here is my guess with the yellow speaker above. the woof coverage pattern is probably the equivalent of 50 degrees vertical from about 900 hz down to about 500 or 400 Hz and in the horizontal, the dipole effect will probably start at about 400 hz and get to 90 degrees. do you know how much boost will be required at about 50 Hz? just curious because of the amount of displacement the woofers will have to experience. boy!! Roy, Depending on the baffle size and the Fs of the drivers used, I'll probably have to start boosting right around 50Hz or so to a MAX anywhere between +5 to +12dB at 20-30Hz. Which with my Behringer DEQ1024, I have a selectable boost range of -6 to +6dB, -12 to +12dB and 0 to +24dB. And on my Rane AC 22B, I can adjust the time delay of the woofers. I'm not too sure how concerned I would be with the coverage pattern since I only listen to my system in the "sweet spot". If I'm not in THAT spot, then I'm in another room so the coverage still doesn't matter at that point. At least, not to me. BTW, after a little more driver research, depending on funds at the time, I may even try going with four Selenium 18" drivers just for a little added oomph! They have slightly less Qts (0.46), but they have quite a bit more surface area, better frequency response (35-3000Hz), lower Fs (33Hz), and just a little bit more Xmax (3.75mm). Quote Link to comment Share on other sites More sharing options...
bodcaw boy Posted November 8, 2006 Share Posted November 8, 2006 Speaking of alternative designs, has anyone ventured into doing an open baffle design at all with dual 15's per channel? With the right drivers, one can easily match the sensitivity ( <105dB 1w/1m) of the squawker, get excellent, clean midrange up to 600Hz and natural, ultra-fast and dynamic bass to an extent before implementing active EQ'ing to compensate for the dipole roll-off in the lowest octaves. This is exactly what I have in the works at the moment. I'm doing some research just to "freshen up" before jumping in head first. This ought to be some fun times coming up soon! [] what kind of directivity (coverage angle) are you going to go with? I'm not sure I follow. If you're referring to the "sweet spot", dipole loudspeakers generally have a broader area rather than just a "spot". well every direct radiator has a characteristic coverage pattern. usually about from low freq to high, it starts off wide dispersion that narrows down to about 120 degree for a certain bandwidth then beams down to about 90 degrees over a certain bandwidth and then starts to collapse. where it starts to collapse is determined by the voice coil diameter. so say you are going to use 15". it is 120 degree from about 300 to about 600 then 90 degrees from 600 to about 1400 hz for a 3" voice coil. this is all approximate since i have slept since then. putting the woofers one on top of another with literally not much space between the frames means that the woofers will create a bubble (d'appolito) that resembles a coverage pattern of about 90 to 70 degrees at about 900 hz. so you could essentially have 90 degrees to about 300 hz. now take a cabinet without a back and whose sides, top and bottom are about 40" deep and you should be able to start dipole action about 300-400 hz. now you could extend the 90 degree coverage pattern well below 100 hz as long as you can keep the amplitude up. is that what you meant about open baffle? or are you going to mount dual 15" on the back as well to make a dipole in an box? boy!! Hi Roy, This is what I mean by dipole (open baffle)... The drivers being used will most likely have a 2.5" VC. They will be crossed over at 600Hz to the 511B/902-8B and will be augmented on the bottom by an EQ to compensate for the dipole roll-off. it is open back... okay here is my guess with the yellow speaker above. the woof coverage pattern is probably the equivalent of 50 degrees vertical from about 900 hz down to about 500 or 400 Hz and in the horizontal, the dipole effect will probably start at about 400 hz and get to 90 degrees. do you know how much boost will be required at about 50 Hz? just curious because of the amount of displacement the woofers will have to experience. boy!! Roy, Depending on the baffle size and the Fs of the drivers used, I'll probably have to start boosting right around 50Hz or so to a MAX anywhere between +5 to +12dB at 20-30Hz. Which with my Behringer DEQ1024, I have a selectable boost range of -6 to +6dB, -12 to +12dB and 0 to +24dB. And on my Rane AC 22B, I can adjust the time delay of the woofers. I'm not too sure how concerned I would be with the coverage pattern since I only listen to my system in the "sweet spot". If I'm not in THAT spot, then I'm in another room so the coverage still doesn't matter at that point. At least, not to me. BTW, after a little more driver research, depending on funds at the time, I may even try going with four Selenium 18" drivers just for a little added oomph! They have slightly less Qts (0.46), but they have quite a bit more surface area, better frequency response (35-3000Hz), lower Fs (33Hz), and just a little bit more Xmax (3.75mm). well i understand about the sweet spot and not being interested in the coverage pattern but unless the reflection surfaces in the room are a great enough distance away to make reflected energy amplitudes small, coverage pattern will make a big difference in what you will listen. we call that the power response of the speaker. the power response of the speaker takes into account all the acoustic energy a speaker spews into space. in an open field with the speaker mounted up high, the power response of a speaker will very little to say about how a speaker "sounds". it will mostly all dependent on the direct energy that comes from being on axis. in other words, the only thing a listener will hear is what comes directly from the drivers to the ears of the listener. start to put boundaries are the speaker and then the reflected energy starts to add to how the speaker sounds. the total opposite is when you have a totally reverberant room and the off axis energy is just as dominate as the on axis stuff. now what you are actually listening to is the power response of the speaker. in this case, i would guess that you will have to boost the bass significantly in order to "compensate" for the bass section being more directive than the mid and tweeter so that the speaker sounds balanced. from coverage angle perspective, you are have tighter control in the bass region with wider dispersion in the mid and top end. from a power response perspective, you will have to boost bass to make the power reponse "flat". that is why i think that it might actually make some sense to use horns with your dipole woofs. just guessing though..... boy!! 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chops Posted November 8, 2006 Share Posted November 8, 2006 that is why i think that it might actually make some sense to use horns with your dipole woofs. just guessing though..... boy!! Use horns with the dipoles? As in bass horns? That would defeat the purpose of going with dipoles in the first place. Quote Link to comment Share on other sites More sharing options...
sfogg Posted November 8, 2006 Share Posted November 8, 2006 Chops, If you are interested in dipole bass spend a lot of time reading the various articles on this site: http://www.linkwitzlab.com/ The speaker you posted a picture of above looks like a ripoff of the Orion from that site above. Shawn Quote Link to comment Share on other sites More sharing options...
bodcaw boy Posted November 8, 2006 Share Posted November 8, 2006 that is why i think that it might actually make some sense to use horns with your dipole woofs. just guessing though..... boy!! Use horns with the dipoles? As in bass horns? That would defeat the purpose of going with dipoles in the first place. no use mid and tweet horns with the dipole bass section..... Quote Link to comment Share on other sites More sharing options...
chops Posted November 8, 2006 Share Posted November 8, 2006 Chops, If you are interested in dipole bass spend a lot of time reading the various articles on this site: http://www.linkwitzlab.com/ The speaker you posted a picture of above looks like a ripoff of the Orion from that site above. Shawn Hey Shawn, I have news for you, I've been writing Siegfried for quite some time now. We spoke a lot when I was planning my dipole subs several years back, and now with my current project as well. Trust me, I nearly lived on his site for a while. LOL And as for this speaker, it is the Jamo R 909. As far as I know, no one makes anything like it, at least not that kind of styling. Also, Legay has been making the Whisper for years now, and it has always been an open baffle (dipole) design, however using FOUR 15" drivers per channel. Quote Link to comment Share on other sites More sharing options...
chops Posted November 8, 2006 Share Posted November 8, 2006 that is why i think that it might actually make some sense to use horns with your dipole woofs. just guessing though..... boy!! Use horns with the dipoles? As in bass horns? That would defeat the purpose of going with dipoles in the first place. no use mid and tweet horns with the dipole bass section..... Oh! Well yes, I plan on using my Altec 511B/902-8B combo with the dipole bass section. Quote Link to comment Share on other sites More sharing options...
Duke Spinner Posted November 9, 2006 Share Posted November 9, 2006 where's the 4th 15" in that speaker ...?? Quote Link to comment Share on other sites More sharing options...
chops Posted November 9, 2006 Share Posted November 9, 2006 where's the 4th 15" in that speaker ...?? Actually, that one you see in the middle on the rear panel is just a 12" passive radiator to help absorb the back wave that bounces off the back wall. The 15's are compound loaded, or isobaric (one behind the other). There's two up top and two on the bottom. Like this... Quote Link to comment Share on other sites More sharing options...
sfogg Posted November 9, 2006 Share Posted November 9, 2006 Yeah, the Whisper is a very cool design. That is a speaker I'd love to own but don't have the right room for them. I've never seen the crossover design on the Whisper but I sort of think the rear pair of woofers is actually not simply in phase with the more forward woofers. I am guessing Legacy runs them out of phase at a reduced level to try to control the directivity in the bass more as that is one of the big deals they make about the Whisper in that it is very directional full range. That is just a theory of mine though. Why do you want to try dipolar in the bass range? Reduced room influence? A bass horn (if it is still fairly directional) would reduce the rooms influence as well compared to a conventional direct radiator. Shawn Quote Link to comment Share on other sites More sharing options...
chops Posted November 9, 2006 Share Posted November 9, 2006 Why do you want to try dipolar in the bass range? Reduced room influence? A bass horn (if it is still fairly directional) would reduce the rooms influence as well compared to a conventional direct radiator. Shawn Hi Shawn, The reason I want a dipole bass bin is because I had a pair of dipole subs before, and absolutely nothing compares to them, at least not from 20Hz on up anyway. With dipole bass, nothing influences nothing, meaning there's no room interaction, there's no box interaction, no hallow, boomy, boxy sound, the bass is extremely fast, tight and precise, and they always seem to integrate well into the music. You're not limited by box tuning, port tuning, horn tuning, room position, port noise, enclosure resonances, etc, etc... The only limiting factor really is the driver chosen. You really have to be able to hear a pair of dipole woofers to truely understand what I'm trying to describe here. And the bass quality... It sounds REAL. There's no other way of putting it, other than REAL sounding. Quote Link to comment Share on other sites More sharing options...
sfogg Posted November 9, 2006 Share Posted November 9, 2006 " meaning there's no room interaction" That is not true. It is reduced by a dipole (by about 5dB) but certainly not eliminated. Measure your bass indoors then outdoors, it won't measure the same even with a dipole. Therefor the room is interacting with it. "You really have to be able to hear a pair of dipole woofers to truely understand what I'm trying to describe here. " I have heard dipolar bass. Shawn Quote Link to comment Share on other sites More sharing options...
chops Posted November 9, 2006 Share Posted November 9, 2006 " meaning there's no room interaction" That is not true. It is reduced by a dipole (by about 5dB) but certainly not eliminated. Measure your bass indoors then outdoors, it won't measure the same even with a dipole. Therefor the room is interacting with it. "You really have to be able to hear a pair of dipole woofers to truely understand what I'm trying to describe here. " I have heard dipolar bass. Shawn They don't interact the same way as a typical "box" speaker does. They DON'T excite the room modes like a box speaker does. The side walls and floor only act as an extension of the baffles to lower the bass roll-off of the baffle, but they do NOT reinforce the bass already present in the music. Quote Link to comment Share on other sites More sharing options...
sfogg Posted November 9, 2006 Share Posted November 9, 2006 "They DON'T excite the room modes like a box speaker does." They excite them by about 5dB less as I have already said. I know a guy with the Orion's. He uses the Lexicon MC-12s Room EQ function to help reduce room resonances (room modes) even with the Orions. Measure your room sometime with a dipolar. You will still see room modes, just they will be about 5dB lower in level then a comparable 'box' woofer at the same SPL. Don't get me wrong, 5dB lower is a big deal. But that is not to say the room has no influence on dipolar bass. Why does a dipolar need 'breathing room' away from the front wall? Because the room influences its response. "The directional response of the ideal dipole is obtained with open baffle speakers at low frequencies. Note, that to obtain the same on-axis sound pressure level as from a monopole, a dipole needs to radiate only 1/3rd of the monopole's power into the room. This means 4.8 dB less contribution of the room's acoustic signature to the perceived sound." Siegfried Linkwitz: http://www.linkwitzlab.com/rooms.htm Shawn Quote Link to comment Share on other sites More sharing options...
mas Posted November 9, 2006 Share Posted November 9, 2006 " They DON'T excite the room modes like a box speaker does." Acoustic energy excites room modes which are dependent upon the geometry of the room. The idea that you can avoid this by a particular enclosure design is incorrect. The Q of the speaker is not a critical factor here. Dipoles are in interesting topology viewed in isolation from their surroundings. But in small rooms they present some very imposing problems, with the reflections and the 180 degree out of phase signal reintroduced into the same space. Especially in the mid and upper frequency passbands...Can we say "comb filtering"!? Note: And a 5dB decrease is insufficient and still extremely audible! A minimum of 10dB decrease in a standing wave is considered acceptable from an aubible perspective. And the superposition of the 180 degree signal, although less pronounced than in the mid-high frequencies, is still a problem. My suggestion, if you like 'dipoles' for subs, go IB and isolate the back wave![] (I know Duke will shoot me for this [] ), but even scoops are infamous for the 120 Hz dip due to the presence of the out of phase superposition of the direct radiator signal with the out of phase horn component. Quote Link to comment Share on other sites More sharing options...
seti Posted November 9, 2006 Share Posted November 9, 2006 Quit hijacking a Jubilee thread! Start another for dipole : ) hehehehe Cool website chops! Quote Link to comment Share on other sites More sharing options...
Deang Posted November 9, 2006 Share Posted November 9, 2006 O.K. Anyone ever thought about a pair of Jubilees with some dipole arrays on top? Quote Link to comment Share on other sites More sharing options...
seti Posted November 9, 2006 Share Posted November 9, 2006 O.K. Anyone ever thought about a pair of Jubilees with some dipole arrays on top? LOL LOL I'll just go take my medications : ) They look cool but where are the horns ? Quote Link to comment Share on other sites More sharing options...
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