KM, I think you are right regarding the sensation of pressure, Earl Geddes explained it to me, it confuses the issue though that people like Siegfried Linkwitz and and John k Offerings refer to room pressurisation.
I don't understand the addition of the resistor in the output of the wideband amp, what does that do?
I sit about four feet from the rear wall, I think the arrangement I have in the room at the moment is near to ideal considering it's size
I don't understand the addition of the resistor in the output of the wideband amp, what does that do?
I sit about four feet from the rear wall, I think the arrangement I have in the room at the moment is near to ideal considering it's size
stereo is best because it is possible to have effects in only one channel.
this is especially true if the sound system is used for video.
while you cannot determine direction of base easily from two channels it is fairly easy to determine direction when only one source is playing at a time.
this does not work with vinyl but it is easy to do in digital.
this is especially true if the sound system is used for video.
while you cannot determine direction of base easily from two channels it is fairly easy to determine direction when only one source is playing at a time.
this does not work with vinyl but it is easy to do in digital.
Sometimes there is a mismatch between the sub amplifier and the main speaker amplifier. If this was the case, they would work quite well together on one specific volume setting, but when changing the volume you would get audible differences. If you have applied some eq to the subs, it may be that the difference gets even greater.
In some cases, taking the high level signal from the main speakers and feeding it into line-in of the sub amp (through some resistors ofcourse), can help reduce this problem.
I do not know what your issue with room modes can be. Having had some sets of OB speakers, but not experienced any room mode issues worth mentioning during my OB escapades, I am just shooting blind as to what your actual problem may be. I always assume there can be several possible answers to any one problem.
In some cases, taking the high level signal from the main speakers and feeding it into line-in of the sub amp (through some resistors ofcourse), can help reduce this problem.
I do not know what your issue with room modes can be. Having had some sets of OB speakers, but not experienced any room mode issues worth mentioning during my OB escapades, I am just shooting blind as to what your actual problem may be. I always assume there can be several possible answers to any one problem.
The amps are identical other than the PSUs. I can understand there being a problem if the gains were different, if that's what you're saying. Anyhow, to be clear, I don't have a major issue with room modes, mainly a large peak at 40Hz which I cut. I'm just trying to find out if mono was the way to go when it comes to optimising the set-up. OB certainly helps but it still excites the longitudinal mode
If a peak at 40hz is your only worry, and it is being brought out by the length of the room. I would just do a notch dip on it and be happy. Run the subs stereo, cross higher, maybe 180hz.
I cross at 220hz myself.
OB can be very fun, and many people like it, it is not for me, and it is not a magical solution that solves all room problems.
If you want to solve it by location of subs, in mono, it might be better to break them up in 4 instead lf 2 like others here have suggested. Place them around the room. It may be that you need some individual eq'ing on each and every sub to get it right, and also possibillity of individually adjusting delay.
I cross at 220hz myself.
OB can be very fun, and many people like it, it is not for me, and it is not a magical solution that solves all room problems.
If you want to solve it by location of subs, in mono, it might be better to break them up in 4 instead lf 2 like others here have suggested. Place them around the room. It may be that you need some individual eq'ing on each and every sub to get it right, and also possibillity of individually adjusting delay.
Bingo.
Bingo again.
Fellas,
One needs to define what frequencies entail “bass.” What frequencies entail “midbass.” And finally how are MOST recordings recorded. Talk to a recording engineer. A great majority of recordings have the bass recorded in summed mono. A few are in stereo, and of those few, they are overwhelmingly classical pieces. So personal preference of music plays a part here.
Bass to me is less than 50 Hz. Midbass is 50-250Hz. All my subs get a summed (L+R) mono signal.
It has to be done right though with measurements and only measurements. When done right I “perceive” bass and midbass from only area. That is from my main speakers.
Here is a good discussion (pages 1-3): Dipole bass vs multisub monopole bass
Best,
Anand.
In regards to recording/mastering standards.
I think every single record sounds different, sometimes there can be quite big variations in terms of Mastering on one album even.
If one recording engineer tells me that every single album or recording under this sun should be following a specific set of standards, my reply would be: then why is it they all sound completely different?
Not a big expert on this topic, but I have been to some smaller recording rooms, and talked to some people regarding this, most just follow various "absolute level" standards and stick to them. Mastering is mostly dependent of how well, or poorly, the engineer in question has set up his playback system. And some change components too frequently to properly adjust them. Chasing rainbows.
There are some very good recording studios, with people that are incredibly skilled at what they do. But not all my music come from those.
If you have a personal definition of everything below 50hz = bass. It would seem that you have a likely affinity towards 3-4way setups.
OP's system consists of a single "Fullrange" unit (Jordan Eikona in a TL?), and 2 x 12" for low frequency duty, per channel. His definition of bass would probably be: Whatever lower frequencies the FR unit can/should not reproduce.
Edit:
Scott: What are you using for xo? Could it be the TL's that excite this specific room mode?
I think every single record sounds different, sometimes there can be quite big variations in terms of Mastering on one album even.
If one recording engineer tells me that every single album or recording under this sun should be following a specific set of standards, my reply would be: then why is it they all sound completely different?
Not a big expert on this topic, but I have been to some smaller recording rooms, and talked to some people regarding this, most just follow various "absolute level" standards and stick to them. Mastering is mostly dependent of how well, or poorly, the engineer in question has set up his playback system. And some change components too frequently to properly adjust them. Chasing rainbows.
There are some very good recording studios, with people that are incredibly skilled at what they do. But not all my music come from those.
If you have a personal definition of everything below 50hz = bass. It would seem that you have a likely affinity towards 3-4way setups.
OP's system consists of a single "Fullrange" unit (Jordan Eikona in a TL?), and 2 x 12" for low frequency duty, per channel. His definition of bass would probably be: Whatever lower frequencies the FR unit can/should not reproduce.
Edit:
Scott: What are you using for xo? Could it be the TL's that excite this specific room mode?
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I will edit my comment in saying that all my subs have different crossover frequencies, phase, slope, etc...and some play as high as 200Hz or so to allow for proper blending. The single most important factor was the measurement and the parameters I look at have been amplitude and the waterfall. The amplitude (FR) particularly without any smoothing/gating/etc so I can see where the problem areas are. Waterfalls to watch for any ringing. We, as humans seem to be very sensitive in the midbass (50-250Hz). This prevents me from going in circles and conjuring theories on why my low frequencies doesn’t sound “right.” If the OP hasn’t done systematic and didactic measurements then it can be quite a frustrating experience. Reading up on Toole’s Sound Reproduction and Geddes’ recommendations as well as those by Paul Spencer (Hifizine) were incredibly useful.
I played with OB as well. Both U-frame (John K’s designs) and H-frames. Multiple subs consisting of OB and monopole, as well as of each type alone. In each case, I was able to achieve a response curve that was very flat and sonically inviting. But the all monopole combination was superior in SPL, freedom from compression,etc...while still providing a very clean and tight midbass (>50Hz-250Hz) we ascribe to OB designs. This was an eye opener.
I would never do any of this by “ear” alone. The ear is helpful in discerning changes in the low frequencies but is not helpful in telling you why they occurred or didn’t occur. The only place I use my “ear” is in setting a target curve. I have found that if 20Hz is about +6dB higher relative to the 100-200Hz area (which we will label as 0 dB), that is sonically the most “pleasurable.” But the FR from 250Hz down to the lower frequencies (20Hz in my case) needs to be free of ripple (+/- 2dB). As a matter of fact, my mains only extend to 50-60Hz or so. That’s it.
Best,
Anand.
I played with OB as well. Both U-frame (John K’s designs) and H-frames. Multiple subs consisting of OB and monopole, as well as of each type alone. In each case, I was able to achieve a response curve that was very flat and sonically inviting. But the all monopole combination was superior in SPL, freedom from compression,etc...while still providing a very clean and tight midbass (>50Hz-250Hz) we ascribe to OB designs. This was an eye opener.
I would never do any of this by “ear” alone. The ear is helpful in discerning changes in the low frequencies but is not helpful in telling you why they occurred or didn’t occur. The only place I use my “ear” is in setting a target curve. I have found that if 20Hz is about +6dB higher relative to the 100-200Hz area (which we will label as 0 dB), that is sonically the most “pleasurable.” But the FR from 250Hz down to the lower frequencies (20Hz in my case) needs to be free of ripple (+/- 2dB). As a matter of fact, my mains only extend to 50-60Hz or so. That’s it.
Best,
Anand.
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Thanks, I found that interesting. I was reminded, while reading, that I wondered if a dipole sub could also be thought of as two for the price of one.
It is the vented transmission line (VTL) cab but when I built it I made the rear panel removable, this is how I'm using it. I don't define bass, I always use Hz in discussions. I was using an analogue active LR4 125Hz crossover, recently I bought a DCX2496 so have been experimenting with that, at the moment I'm using LR8 at 100Hz.
Anand: it seems then, we had similar experiences from OB. I had to try several variations of OB to really appreciate a good box, so to speak.
Edit:
Scott: I also prefer a strict hz kind of thing, easy to get carried away on opinions if not.
Steep filters are quite useful, do not know if you've tried 2nd order bessel? Was quite useful for me in my last OB setup. Anyway, fun to experiment with filter types and orders.
Edit:
Scott: I also prefer a strict hz kind of thing, easy to get carried away on opinions if not.
Steep filters are quite useful, do not know if you've tried 2nd order bessel? Was quite useful for me in my last OB setup. Anyway, fun to experiment with filter types and orders.
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I've tried a number, it's handy that I don't have to worry about over exerting the Jordans. The high order is killing the cavity resonance better than 24dB. From what I've read using steep filters at such a low frequency can do more good than harm. Also, since they are separate cabinets the sharp cut off allows me more flexibility in positioning, that's my thinking anyway.
What frequency is the cavity resonance, and what does it sound like?
Seems your U baffles are too small to have any real resonant behaviour under several hundred hz. Do you have/have you tried a divider between the upper/lower woofer?
I've played a bit with 1-20 order filters, quite interesting to try chebychev, bessel, butterworth, elliptic, cascading different types. So easy now, just playing around in a program.
Seems your U baffles are too small to have any real resonant behaviour under several hundred hz. Do you have/have you tried a divider between the upper/lower woofer?
I've played a bit with 1-20 order filters, quite interesting to try chebychev, bessel, butterworth, elliptic, cascading different types. So easy now, just playing around in a program.
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It's at about 160Hz, it sounds like a peak using sine waves. The U frames are 12" deep, yes there is a complete shelf between them. There is a description here about calculating cavity resonance on page 3 http://www.quarter-wave.com/OBs/U_and_H_Frames.pdf
I see.
Read that some years ago. I've never had that problem, kept the baffles "shorter".
Edit:
Though Martin does mention the bump works well together with 2nd order filters, and somewhat extends flat response to a higher frequency. See page 5, crossover design.
That may explain why I landed on using 2nd order bessel eventually. There was a mismatch between xo frequencies, 4th order LR HP + 2nd order Bessel LP worked for me. Playing around works well.
Read that some years ago. I've never had that problem, kept the baffles "shorter".
Edit:
Though Martin does mention the bump works well together with 2nd order filters, and somewhat extends flat response to a higher frequency. See page 5, crossover design.
That may explain why I landed on using 2nd order bessel eventually. There was a mismatch between xo frequencies, 4th order LR HP + 2nd order Bessel LP worked for me. Playing around works well.
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Hah!
So you'd rather argue that there is resonant behaviour you do not like, and refuse to utilize it on the basis of it being resonant. :-D
I like you, and you get victory points from stubborn-ness alone. I must admit I'd rather work with resonance than against. Like my wife, who was using a hydraulic splitter to make firewood, all of a sudden there was a loud thump, then silence, she came inside quite dizzy with a black lip, tried splitting wood the wrong way, "sideways". "But dear, you should split wood WITH the grain, we have gone through this, I showed you before." At least she remembers now.
What about you? You have resonant behaviour at some frequencies. Your house, having room modes, is better left alone, better to move outside and live in a tent in the garden. People stop by asking: "is your house under pest control? Why do you not live inside it?" You reply: "No, it just has resonant behaviour, room modes and whatnot."
So you'd rather argue that there is resonant behaviour you do not like, and refuse to utilize it on the basis of it being resonant. :-D
I like you, and you get victory points from stubborn-ness alone. I must admit I'd rather work with resonance than against. Like my wife, who was using a hydraulic splitter to make firewood, all of a sudden there was a loud thump, then silence, she came inside quite dizzy with a black lip, tried splitting wood the wrong way, "sideways". "But dear, you should split wood WITH the grain, we have gone through this, I showed you before." At least she remembers now.
What about you? You have resonant behaviour at some frequencies. Your house, having room modes, is better left alone, better to move outside and live in a tent in the garden. People stop by asking: "is your house under pest control? Why do you not live inside it?" You reply: "No, it just has resonant behaviour, room modes and whatnot."
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