Konnichiwa,
Depends upon you definition of "mid bass". Severe room modes often exist in the 50-100Hz range. If the speaker used still outputs a lot of energy in this range and is well coupled to room modes (due to the invariable near corner placement) you get severe resonances in the range where a lot of "Bass" instruments actually have notes. This overwhelming "one note" Bass will obscure really low stuff unless dealt with (by equalising or using dipoles).
The ceiling to floor mode may be the responsible one, as all other modes should be below the musical range. In a normal room both speaker and listener tend to be near the "null" of the vertical mode, as the rooms are usually 2.5 - 3m High. Make the room much higher and you are asking for trouble with the vertical mode, instead of any of the lateral one.
It is hard to be more specific without doing a full acoustical analysis of the room.
There is a good program and some more resources here:
http://www.rivesaudio.com/CARAquick/CARAframe.html
The Horn mouth must point towards the listener and have enough surface area to retain pattern control at the lowest frequency related to a room mode.
That is entierly possible. However, truely "uncompromised" Horns and Dipoles tend to be structurally of a nature that makes them extremely rare beasties. While I love discussing the absolute, in reality we usually deal with the relative.
And for domestically aceptable structures a "unipole" arrangement is in my view the best LF module, as horns will be too small to be usefull.
Sayonara
paulspencer said:
Depends upon you definition of "mid bass". Severe room modes often exist in the 50-100Hz range. If the speaker used still outputs a lot of energy in this range and is well coupled to room modes (due to the invariable near corner placement) you get severe resonances in the range where a lot of "Bass" instruments actually have notes. This overwhelming "one note" Bass will obscure really low stuff unless dealt with (by equalising or using dipoles).
paulspencer said:
The ceiling to floor mode may be the responsible one, as all other modes should be below the musical range. In a normal room both speaker and listener tend to be near the "null" of the vertical mode, as the rooms are usually 2.5 - 3m High. Make the room much higher and you are asking for trouble with the vertical mode, instead of any of the lateral one.
It is hard to be more specific without doing a full acoustical analysis of the room.
There is a good program and some more resources here:
http://www.rivesaudio.com/CARAquick/CARAframe.html
paulspencer said:
The Horn mouth must point towards the listener and have enough surface area to retain pattern control at the lowest frequency related to a room mode.
paulspencer said:
That is entierly possible. However, truely "uncompromised" Horns and Dipoles tend to be structurally of a nature that makes them extremely rare beasties. While I love discussing the absolute, in reality we usually deal with the relative.
And for domestically aceptable structures a "unipole" arrangement is in my view the best LF module, as horns will be too small to be usefull.
Sayonara
Konnchiwa,
Actually, I'm taking liberties here.... The true "unipole" is a design by wvier audio and combines a dipole and a monopole, with adjustable group delay and levels, so in effect ANY directivity pattern, from dipole over various cardiods to omnipole can be produced.
What I am refering to is perhaps best called "limited unipole".
I detailed it earlier somewhere. My argument is that at very low frequencies (below the lowest room mode) an omnidirectional super/infra-woofer is desirable, with as low a cutoff as attainable. With rising frequency this "omni" woofer should hand over to a dipole woofer.
Now if we design a crossover proper, with (say) 3rd order acoustic slopes we can let our dipole roll out naturally if we select the driver suitably for resonance frequcny and Qt (there may still be a need for some EQ of course). At the nominal crossover our dipole will be 6db down in SPL, as will be our super/infra-woofer.
In other word, the same amount of SPL is generated by a (more or less) co-incidental dipole and monopole, giving a (hyper) cardiod response with in theory full cancellation of any rear output and full doubeling up of the front output, giving a flat spl response.
Using our 3rd order slopes the "transitory" region through which the radiation patter changes from omni to dipole will be around 1 Octave, so perhaps from 35-70Hz centered around 50Hz (as it is currently the case for my own system).
The combination can deliver very powerfull low bass output with excellent speed and control of low notes falling into the room mode region and with the classic "chest crushing" pressure often missing from Dipoles even with a very low cutoff (eg. Carver "Amazing").
I guess I have to call it something else than "unipole", but I can't come up with any better term.
I hope this helps.
Sayonara
paulspencer said:
Actually, I'm taking liberties here.... The true "unipole" is a design by wvier audio and combines a dipole and a monopole, with adjustable group delay and levels, so in effect ANY directivity pattern, from dipole over various cardiods to omnipole can be produced.
What I am refering to is perhaps best called "limited unipole".
I detailed it earlier somewhere. My argument is that at very low frequencies (below the lowest room mode) an omnidirectional super/infra-woofer is desirable, with as low a cutoff as attainable. With rising frequency this "omni" woofer should hand over to a dipole woofer.
Now if we design a crossover proper, with (say) 3rd order acoustic slopes we can let our dipole roll out naturally if we select the driver suitably for resonance frequcny and Qt (there may still be a need for some EQ of course). At the nominal crossover our dipole will be 6db down in SPL, as will be our super/infra-woofer.
In other word, the same amount of SPL is generated by a (more or less) co-incidental dipole and monopole, giving a (hyper) cardiod response with in theory full cancellation of any rear output and full doubeling up of the front output, giving a flat spl response.
Using our 3rd order slopes the "transitory" region through which the radiation patter changes from omni to dipole will be around 1 Octave, so perhaps from 35-70Hz centered around 50Hz (as it is currently the case for my own system).
The combination can deliver very powerfull low bass output with excellent speed and control of low notes falling into the room mode region and with the classic "chest crushing" pressure often missing from Dipoles even with a very low cutoff (eg. Carver "Amazing").
I guess I have to call it something else than "unipole", but I can't come up with any better term.
I hope this helps.
Sayonara
i think there is some apple to oranges comparisons going on here. i have heard multiple interations/generations of magnetar's rigs and i was magnetar's house this last weekend during a "beers & ears" party he was hosting.
when you mention the carver amazing loudspeaker, it is apparent to me that your concept of acceptable output levels are entirely different than magnetar's. just the horn mouth area for his mid to upper bass horns appear to be approx the same surface area as about 3.5 x 18" woofers (and that is a single channel)
his system is really in a different league than what 99% of people have in their homes (i am giving the remaining 1% the benefit of the doubt). i liken it to the best small club sound system available, but with the resolution expected in a high-end, audiophile type speaker. so, when he talks about "live" listening levels, he means it.
i have listened to the martin-logan statements for an hour or so, and they seemed to have the same kind of feeling of unlimited dynamic range, but they were crossing over their dynamic dipole array of 8 x 7" woofers at 60hz to a bipolar/monopole column of 8 x 12".
i have a gut feeling that to reasonably match the output of magnetar's horn rig you would need to go at least with 8 x15" in stacked linkwitz w-baffles and even then i suspect you would have trouble in the 20hz-35hz range.
when you mention the carver amazing loudspeaker, it is apparent to me that your concept of acceptable output levels are entirely different than magnetar's. just the horn mouth area for his mid to upper bass horns appear to be approx the same surface area as about 3.5 x 18" woofers (and that is a single channel)
his system is really in a different league than what 99% of people have in their homes (i am giving the remaining 1% the benefit of the doubt). i liken it to the best small club sound system available, but with the resolution expected in a high-end, audiophile type speaker. so, when he talks about "live" listening levels, he means it.
i have listened to the martin-logan statements for an hour or so, and they seemed to have the same kind of feeling of unlimited dynamic range, but they were crossing over their dynamic dipole array of 8 x 7" woofers at 60hz to a bipolar/monopole column of 8 x 12".
i have a gut feeling that to reasonably match the output of magnetar's horn rig you would need to go at least with 8 x15" in stacked linkwitz w-baffles and even then i suspect you would have trouble in the 20hz-35hz range.
Which is why KWY suggests transitioning to a monopole source (sealed box) below the first room eigenvalue. There is no need for a dipole array to attempt 25Hz reproduction in the size of a typical home's room. You might expect the first mode to be around ~40Hz and above for most people's room sizes, and perhaps ~35hz for a large one. Dipole sub systems capable of prodigous output to 40Hz need not be physically intimidating (at least compared to your suggestion of 16 15" drivers), and sealed enclosures matching the output of even Magnetar's horns at 20Hz and below will seem quaint in size compared to his solution. On this point, I can only agree with KWY emphatically.
The only fly in the ointment is the loss of flat(ish) power response paralleling a flat amplitude response at the listening position (which dipoles provide) below the dipole/monopole transition frequency. With the behavior of rooms in response to pressurization below frequencies in which standing waves can develop, the impact of this shift in power response is unclear. Combined with our reduced hearing acuity, it would not seem to be a problem, but it is an area that I intend to more fully explore.
The only fly in the ointment is the loss of flat(ish) power response paralleling a flat amplitude response at the listening position (which dipoles provide) below the dipole/monopole transition frequency. With the behavior of rooms in response to pressurization below frequencies in which standing waves can develop, the impact of this shift in power response is unclear. Combined with our reduced hearing acuity, it would not seem to be a problem, but it is an area that I intend to more fully explore.
Hello Curtis (it is you isn't it? -- 
I actually have made some progress on the system since Saturday. We were listening yesterday and felt the subhorn to basshorn transition was a bit off -- What I changed was
1) the large tube traps at the intersection of the subhorns/wall/basshorn have been raised from the submouth to where they now meet the ceiling rather than sitting in front of outside horns mouths on the floor.
2) moved the tractrix satellite horns to the OUTSIDE and the bass horns off the side walls to the inside of the satellites.
3) raised the crossover frequency between the sub and bass horns to 50 cycles as opposed to the old 40 cycle point -- the bass horns aren't loaded as well on the very bottom of their range since they aren't coupled to the sidewalls anymore.
The benefits are clearly audible. For one the soundstage opened up even further (well beyond the room walls) where instruments that used to be on the edge of the stage were a bit out of focus now have much clearer focus with 'flesh and bones' and dimension, the 60 cycle hole that was directly behind the sofa has been raised to almost flat, and the transition between the horns is as transparent as I have been able to obtain in my room.
All in All it was worth the 2 hours I spent moving these beasts around -- They really opened up.
I have usesd eight JBL 2235H 15's before in a dipole (as well as infinite baffle and reflex) -- It was good by 'high end' standards but not like this. IE -- pitch, impact, overhang, power, weight, "speed" are better with the horns.
I actually have made some progress on the system since Saturday. We were listening yesterday and felt the subhorn to basshorn transition was a bit off -- What I changed was
1) the large tube traps at the intersection of the subhorns/wall/basshorn have been raised from the submouth to where they now meet the ceiling rather than sitting in front of outside horns mouths on the floor.
2) moved the tractrix satellite horns to the OUTSIDE and the bass horns off the side walls to the inside of the satellites.
3) raised the crossover frequency between the sub and bass horns to 50 cycles as opposed to the old 40 cycle point -- the bass horns aren't loaded as well on the very bottom of their range since they aren't coupled to the sidewalls anymore.
The benefits are clearly audible. For one the soundstage opened up even further (well beyond the room walls) where instruments that used to be on the edge of the stage were a bit out of focus now have much clearer focus with 'flesh and bones' and dimension, the 60 cycle hole that was directly behind the sofa has been raised to almost flat, and the transition between the horns is as transparent as I have been able to obtain in my room.
All in All it was worth the 2 hours I spent moving these beasts around -- They really opened up.
I have usesd eight JBL 2235H 15's before in a dipole (as well as infinite baffle and reflex) -- It was good by 'high end' standards but not like this. IE -- pitch, impact, overhang, power, weight, "speed" are better with the horns.
qxlxp said:i think there is some apple to oranges comparisons going on here. i have heard multiple interations/generations of magnetar's rigs and i was magnetar's house this last weekend during a "beers & ears" party he was hosting.
when you mention the carver amazing loudspeaker, it is apparent to me that your concept of acceptable output levels are entirely different than magnetar's. just the horn mouth area for his mid to upper bass horns appear to be approx the same surface area as about 3.5 x 18" woofers (and that is a single channel)
his system is really in a different league than what 99% of people have in their homes (i am giving the remaining 1% the benefit of the doubt). i liken it to the best small club sound system available, but with the resolution expected in a high-end, audiophile type speaker. so, when he talks about "live" listening levels, he means it.
i have listened to the martin-logan statements for an hour or so, and they seemed to have the same kind of feeling of unlimited dynamic range, but they were crossing over their dynamic dipole array of 8 x 7" woofers at 60hz to a bipolar/monopole column of 8 x 12".
i have a gut feeling that to reasonably match the output of magnetar's horn rig you would need to go at least with 8 x15" in stacked linkwitz w-baffles and even then i suspect you would have trouble in the 20hz-35hz range.
Pitch... hmm... only things that can possibly affect the perception of pitch is doppler distortion (unlikely, since the warble is centered) or harmonic distortion. Doppler distortion Horns have an advantage in, harmonic they do not. Not sure what could have accounted for your perception of inferior "pitch" definition with dipoles.Magnetar said:
Overhang... hmm... horns have measurable inferior transient response. Compared to dipoles, they do have more overhang or ringing. It is a fact.
As for impact, power, weight, and "speed"... well, those are entirely subjective terms that more often than not really have no basis in reality. The "speed" of a subwoofer is nonsensical. Power and impact are defined by SPL capability and power compression attributes. For a given SPL, a dipole sub should have more impact above the room's first eigenmode, perhaps less below, which is why I agree with KWY that transitioning to a monopole below that frequency is advantageous. Perhaps you equate impact with raw SPL output ability? And as for weight, I really can't fathom what that is supposed to convey, but as there is no shortage of audiophile terminology in use I'm sure it has some commonly used definition somewhere.
RHosch said:
HAHAHA you guys spend more time reading and theorizing over your fantasies then building, listening and measuring. Funny thing is once you finally decide what the 'best' way to do bass in your room is you'll build it (maybe!) only to find out it is mearly a toy at reproducing music compared to good horns. Sure you might build something that might sound ok but not real -- not even close. If that is your goal I'm sure it's within reach.
PS_ I'm not going to spend any time arguing or correcting your assumptions - learn on your own - maybe it will seat in that way.
Magnetar said:
I think this is where a little respect and tolerance for each other's preferred approach to our hobby is needed.
Magnetar, you obviously prefer the "learn by doing" approach where you build many different speakers and continually improve. You have build a system that you consider to be the ultimate, and have achieved a lot more than most. But when it comes to discussing the theory, you have made some statements that clearly aren't correct, and if challenged on some point of theory, if your arguement doesn't stand on it's own, then criticising others for not building won't help your argument. What's wrong with saying that you think your system is the ultimate to your ears but you can't prove it from a theoretical point of view?
Many on this forum prefer to discuss and understand the theory behind what we are going to build before we start building. This is the "understand the theory then apply it" approach.
I don't think it is necessary to criticise others for approaching it differently. This forum created in the spirit of learning, discussing, sharing ideas, experience and knowledge.
KWY,
Back to that room I mentioned ... I'd like to put together a dipole woofer for a DIY night at the end of the year as I suspect it may demonstrate that it is possible to get decent bass in that room where the other speakers so far have mostly failed.
Is a dipole likely to be suitable for that room regarding the vertical room modes? What would you consider the best approach? This is also of interest as I would like to build a large HT room in the future which would also have a high ceiling, although in that case I'd be most likely to employ an integrated bass horn.
I'd also like to hear your thoughts on the merits of a H frame vs open back dipole woofer as used in the Nao, both in small to medium rooms as well as that particular room with (probably) vertical modal issues. Obviously it would only be a guess with regards to the room described earlier ...
Back to that room I mentioned ... I'd like to put together a dipole woofer for a DIY night at the end of the year as I suspect it may demonstrate that it is possible to get decent bass in that room where the other speakers so far have mostly failed.
Is a dipole likely to be suitable for that room regarding the vertical room modes? What would you consider the best approach? This is also of interest as I would like to build a large HT room in the future which would also have a high ceiling, although in that case I'd be most likely to employ an integrated bass horn.
I'd also like to hear your thoughts on the merits of a H frame vs open back dipole woofer as used in the Nao, both in small to medium rooms as well as that particular room with (probably) vertical modal issues. Obviously it would only be a guess with regards to the room described earlier ...
a different tack
To take the debate on a different tack forward, what do people think are the best DIY designs in each approach?
In dipoles, the Orion and Phoenix have garnered the most widespread praise.
I’m not so sure about horns, but Tom Danley’s LABhorn bass horn, with the ‘Live Audio Board’; and his Unity seem very good designs, to me at least. (Danley also designed the Contra-bass and Servodrive subs). The Unity (300 Hz and up) IIRC acts as a point source.
Any higher bids?
To take the debate on a different tack forward, what do people think are the best DIY designs in each approach?
In dipoles, the Orion and Phoenix have garnered the most widespread praise.
I’m not so sure about horns, but Tom Danley’s LABhorn bass horn, with the ‘Live Audio Board’; and his Unity seem very good designs, to me at least. (Danley also designed the Contra-bass and Servodrive subs). The Unity (300 Hz and up) IIRC acts as a point source.
Any higher bids?
jeff mai said:
As I understand, transient response inferior to a dipole would apply to all horns. I think this is a fair statement, unless anyone can provide some data to suggest otherwise.
A dipole has a transient response determined purely by the driver itself. The transient response of horns will be affected by the side of the driver that isn't horn loaded (the sealed part), although where the rear of the driver is effectively going into an infinite baffle, this will not be the case. I imagine the horn structure itself will also have a significant effect.
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