Thanks everyone for the links; it sounds like CARA could be a useful starting point, if the simulations give results resembling reality in any way.
I'm not sure changing the speakers is what I was after - part of the point is that I want a good room which allows me to compare & contrast different speakers; I also make the occasional recording, for which a good room is essential.
I'm also unconvinced about EQ (digital or otherwise) for anything above the lowest frequencies. EQ can correct for mild resonant effects, but it's not going to fix a bad room reverb.
Cheers
IH
I'm not sure changing the speakers is what I was after - part of the point is that I want a good room which allows me to compare & contrast different speakers; I also make the occasional recording, for which a good room is essential.
I'm also unconvinced about EQ (digital or otherwise) for anything above the lowest frequencies. EQ can correct for mild resonant effects, but it's not going to fix a bad room reverb.
Cheers
IH
Nielsio said:
Well, I've been sound engineering one way or another for about 20 years, and I 'started listening to things' some time before that.
Yes, low-frequency EQ can compensate for errors in loudspeaker response; compact PA system manufacturers (Bose, Celestion, EV come to mind) have been doing this for ages, and it basically works. It can also help to fix up the fundamental room resonant modes.
EQ can't, though, prevent unwanted reflections, remove flutter echo or shorten a long room reverb. It just doesn't work in practice and there's lots of good maths which explains why. Controlling room-related problems by fixing the room is what I'm after here.
Cheers
IH
This thread has raised questions in my mind about how to best continue with my hi-fi system development!
I am currently using Goodmans 201's (full-range 12 inch twin-cone drivers) in open baffles and was thinking of adding some di-pole woofers to fill in below 75 Hz.
However, after reading this thread and the links, I am wondering if I would be better spenig money on something like the Behringer first and then adding more drivers later.
Any thoughts/advice on this idea?
I am currently using Goodmans 201's (full-range 12 inch twin-cone drivers) in open baffles and was thinking of adding some di-pole woofers to fill in below 75 Hz.
However, after reading this thread and the links, I am wondering if I would be better spenig money on something like the Behringer first and then adding more drivers later.
Any thoughts/advice on this idea?
My thoughts:
EQing the lower frequencies to a fine balance can be done very nicely with the Behringer. However: don't forget that, in order to get warm and deep bass from such a full-ranger, the excursion will go up quite considerably.
For normal to decent sound volumes this should not form a problem. But if you want to go loud, your Goodmans will have to break a sweat, excursion will go up considerably, and you'll start to wonder if that kind of movement is healthy for speakers who will probably not have a huge linear excursion.
So: if you don't want to worry and / or want to play the occasional movie with boombastic sound, go for the extra driver(s). But if you want to keep your ultra-coherent sound (also because of no filter) and can keep the volume-knob in the green, then Behringer it is!
Thanks Nielso. As I live in a terraced house, volume levels have to be kept 'reasonable' anyway. And at my age, disco parties are not on my social agenda 
It may be a good idea to go with the Behringer first after all!
I have been looking at the Behringer product range but it just baffles me. Which is their best one for home hi-fi use?
It may be a good idea to go with the Behringer first after all!I have been looking at the Behringer product range but it just baffles me. Which is their best one for home hi-fi use?
The popular and well-known digital equalizer is the Ultracurve 8024. There is followup-product, called the DEQ2496
http://www.behringer.com/02_products/prodindex.cfm?id=DEQ2496&lang=eng
This last one has better theoretical quality and also more functionality. I manage fine with the 'old' one however plus the 8024 will probably be cheaper (if you can still find it).
Do realise that:
* Using it is not that easy
* I myself prefer measurements through my computer to be far more insightfull
* The sub-125 hz EQing are >50% done by ear (..in my experience)
http://www.behringer.com/02_products/prodindex.cfm?id=DEQ2496&lang=eng
This last one has better theoretical quality and also more functionality. I manage fine with the 'old' one however plus the 8024 will probably be cheaper (if you can still find it).
Do realise that:
* Using it is not that easy
* I myself prefer measurements through my computer to be far more insightfull
* The sub-125 hz EQing are >50% done by ear (..in my experience)
Nuuk said:Thanks again Nielsio - (much) more reading obviously required. Perhaps one day we can study for a diploma in hi-fi!
If that ever happens, I know many schools will arise (Wang school of Enlightment, The Kapitalistica Multidrivanoefficienca, Watt Factory-X, The Horny Horners, The Sourcerers (source-first), etc)
Konnichiwa,
Well, the 201 on the Baffle should do fine, IF the baffle is large enough. If the baffle is not large enough make it larger. NOTE that folding back wings have surprisingly little effect unless the wings reach back very far and are not folded back entierly - in which case a flat baffle of approximatly the width the entire assembly occupies plus some extra would have done equally well.
If you MUST use a baffle too small, a simple passive shelving RC EQ could be used to boost the bass enough to get subjective flatness down into the 40Hz range. Thanks to the dipole nature of the Speaker room modes will be much less of a problem, so EQ is not really needed for that.
My own experience with original 201's is that they have naturally a pretty nice and pleasant "Tone" not requiring much EQ in the Midrange. Something like our shelving EQ could be used also to boost the treble a little but adding something like a Fostex FT17H is a better solution in my view.
For your own baffle size try a the following (assuming a 50K Volume control for your Amp - otherwise scale to suit the impedance):
Resistor in series with signal = 12k
Resistor in series with capacitor to ground = 9K1 & 0.22uF
For a little treble lift try a 1nF Capacitor (or larger/smaller to taste) in parallel with the 12k Resistor.
Sayonara
Nuuk said:
Well, the 201 on the Baffle should do fine, IF the baffle is large enough. If the baffle is not large enough make it larger. NOTE that folding back wings have surprisingly little effect unless the wings reach back very far and are not folded back entierly - in which case a flat baffle of approximatly the width the entire assembly occupies plus some extra would have done equally well.
If you MUST use a baffle too small, a simple passive shelving RC EQ could be used to boost the bass enough to get subjective flatness down into the 40Hz range. Thanks to the dipole nature of the Speaker room modes will be much less of a problem, so EQ is not really needed for that.
My own experience with original 201's is that they have naturally a pretty nice and pleasant "Tone" not requiring much EQ in the Midrange. Something like our shelving EQ could be used also to boost the treble a little but adding something like a Fostex FT17H is a better solution in my view.
For your own baffle size try a the following (assuming a 50K Volume control for your Amp - otherwise scale to suit the impedance):
Resistor in series with signal = 12k
Resistor in series with capacitor to ground = 9K1 & 0.22uF
For a little treble lift try a 1nF Capacitor (or larger/smaller to taste) in parallel with the 12k Resistor.
Sayonara
The current baffles are 1220mm by 610mm (4 feet by 2 feet). I have tried a cowl on the rear which goes back about 500mm. Now whether it was because the cowl was made of polystyrene or not I don't know, but although bass was slightly better, it removed much of the open-baffle magic - ie it sounded more like a boxed speaker.
I am about to build 'finished' baffles, replacing the chipboard/polystyrene sheet with solid wood and glass so will make them a bit wider as they won't be so noticeable.
Yes, and even more so with mine which were slightly modified during their rebuild by Dave Smith to give them a smoother mid-range.
Hmmm. I have a variety of Gainclones here. The one I use currently has a shunt type attenuator with an impedance ranging from 75K up.
Do these (and the ones for the treble lift) go before or after the volume control and do they affect the LPF on the input of the amp?
"Wooden panels with holes drilled in sounds like a panel absorber for soaking up bass. Apparently you can tune these things to very specific frequencies, by the number of holes and size etc."
This is called the Helmholtz Principle. Similar to blowing across a glass bottle.....different openings and container sizes resonate at different frequencies. F Alton Everest wrote a book called Master Handbook of Acoustics that has alot of good info init if you wanna get into the room tuning thing
This is called the Helmholtz Principle. Similar to blowing across a glass bottle.....different openings and container sizes resonate at different frequencies. F Alton Everest wrote a book called Master Handbook of Acoustics that has alot of good info init if you wanna get into the room tuning thing
Yes, thanks, that is referenced in the book I quoted earlier in the thread. Certainly worth checking the bookshops for...
I am very vaguely aware of this Helmholtz thing, really just from ported speakers, but what I was curious about is how normally its exaggerating a frequency, but here its used to attenuate one.
I don't really want to get into the whole room tuning thing, but my bass quality just isn't good enough at high volumes, and I absolutely cannot afford to start a new speaker project at this moment in time. EQ is expensive too, and I hate the thought of putting extra things in the path.
-Simon
Konnichiwa,
That will be fine.
Before, BUT, you could insert them between buffer and Amp as long as you scale the values to suit the Input impedance of that circuit. However, then the Amp is no longer universal. I used such RC Circuits to compendsate full range speakers (in boxes) many years ago, simply plugged into the tape loop....
Sayonara
Nuuk said:
That will be fine.
Nuuk said:
Before, BUT, you could insert them between buffer and Amp as long as you scale the values to suit the Input impedance of that circuit. However, then the Amp is no longer universal. I used such RC Circuits to compendsate full range speakers (in boxes) many years ago, simply plugged into the tape loop....
Sayonara
Room modes
Simon said:
>>This crappy wall is plaster on 2 sides of a thin wooden frame. I gather many American homes use this kind of construction, and that it creates a very unpleasant ~60-60hz (iirc) resonance. This would be less an absorber, but more a changer/colouriser, from what I gather. Meaning it absorbs sounds, then re-releases them with delay of course, and with a chaneged frequency spectrum. Rather like a metal and glass rack I suppose!<<
Hi Simon;
Sorry, but I was busy last weekend and completely lost track of where we were in this thread LOL!!
I've just lately started to take it serious regarding room acoustics as it seems to be a weak link for good sound reproduction. Speakers are one thing, but acoustics have always been a difficult subject for me. I think I will look into getting a program to help me sort through some of this stuff, at least it will be less boring than reading it in a book LOL. The CARA program seems to be a definate candidate.
It's my understanding that a room with walls made of plaster board is considered a " lossy " room compaired to a room with, lets say brick or cement walls. The theory being that as the sound energy hit's the plaster board, it vibrates, hense it absorbs energy, hense the term lossy. A cement wall dosen't vibrate but reflects most of the energy back into the room.
But then again the plaster board walls release some of that energy back into the room, delayed, and with shifts in frequency, and the whole thing gets very complicated.
I'm going to be investigating all of this stuff in the near future.
I have a great room mode calculator in the form of an Excel spreadsheet, very easy to use. I could email it to you if you are interrested as I can't attach to the postings on this forum. I can't send you a link because I don't remember I got it.
Doug
Simon said:
>>This crappy wall is plaster on 2 sides of a thin wooden frame. I gather many American homes use this kind of construction, and that it creates a very unpleasant ~60-60hz (iirc) resonance. This would be less an absorber, but more a changer/colouriser, from what I gather. Meaning it absorbs sounds, then re-releases them with delay of course, and with a chaneged frequency spectrum. Rather like a metal and glass rack I suppose!<<
Hi Simon;
Sorry, but I was busy last weekend and completely lost track of where we were in this thread LOL!!
I've just lately started to take it serious regarding room acoustics as it seems to be a weak link for good sound reproduction. Speakers are one thing, but acoustics have always been a difficult subject for me. I think I will look into getting a program to help me sort through some of this stuff, at least it will be less boring than reading it in a book LOL. The CARA program seems to be a definate candidate.
It's my understanding that a room with walls made of plaster board is considered a " lossy " room compaired to a room with, lets say brick or cement walls. The theory being that as the sound energy hit's the plaster board, it vibrates, hense it absorbs energy, hense the term lossy. A cement wall dosen't vibrate but reflects most of the energy back into the room.
But then again the plaster board walls release some of that energy back into the room, delayed, and with shifts in frequency, and the whole thing gets very complicated.
I'm going to be investigating all of this stuff in the near future.
I have a great room mode calculator in the form of an Excel spreadsheet, very easy to use. I could email it to you if you are interrested as I can't attach to the postings on this forum. I can't send you a link because I don't remember I got it.
Doug
Hello Doug!
That CARA stuff does look interesting. I often wonder about those big foam absorbers - but I just looked at the most effectively absorbed frequencies, and realised it could make the mid-bass problems even worse by cutting out too much [lowish]upper-bass!
-Simon
That CARA stuff does look interesting. I often wonder about those big foam absorbers - but I just looked at the most effectively absorbed frequencies, and realised it could make the mid-bass problems even worse by cutting out too much [lowish]upper-bass!
Yeh, I'm hearing that. I'm glad it's only 1 wall in my case! Others are breeze blocks. Hmm, the reason I have indisntict bass notes across the mid-bass may be partly due to the re-released energy from this wall - it's RIGHT behind the listening position. This is interesting/worrying!
I'd like that calculator please! I hate the rigmorole of working it out each time
-Simon
Today I tried some EQing for my open baffles with the following circuit.
which I hope accurately portrays what KYW suggested!
I could hear some more pronounced bass but could hardly get any volume!
I have now removed the EQ circuit and notice that even with my volume control at its highest setting the music is no more than comfortably loud. The rest of the amp circuit is as shown on my VBIGC page
The attenuator impedance ranges from 75K-150K. Any ideas?
An externally hosted image should be here but it was not working when we last tested it.
which I hope accurately portrays what KYW suggested!
I could hear some more pronounced bass but could hardly get any volume!
I have now removed the EQ circuit and notice that even with my volume control at its highest setting the music is no more than comfortably loud. The rest of the amp circuit is as shown on my VBIGC page
The attenuator impedance ranges from 75K-150K. Any ideas?
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