Re. wires, good, I thought so... but honestly I'm shocked at the price you pay for the bass you get. I'm not making a value judgment, but I've built and tweaked many big systems with >10x less LF cancellation than yours, but which had magnificently accurate and extended bass. I've never seen such a setup as yours. The other thing is given the spacing of those cabinets, I would expect time coherence of the direct LF signal to be acceptable at only a tiny position, and the other drivers would need also delayed and alongside the front bass cabinets. Where are the other drivers? You must use a delay for the front cabinets, but that again would wreck any coherence of room reflections. Are your walls nearly anechoic? I am baffled by the lack of baffles. But consider that I dislike D'Appolito layouts (but enjoy some planar systems) for the same reason, they too spread wide the drivers of a channel, so I sit at the opposite end of the field of design. Thank you for sharing.I almost lost count of them woofers myself.
I run four woofers on each NC400, wired in parallel... ....But then the quality of the bass we can get with dipoles is unmatched.
Pardon my ignorance, what is OB? Is it something like ohne(without)-baffle, because that is what I see.
EDIT: Doh, never mind (smacks head). When I've heard that term I always assumed *some* baffle: such thing swork fine when the wavelength is less than the baffle radius...
I still don't know what Erlend is trying to achieve, though I feel less alone in that ignorance.
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OB = Open Baffle ....
The main problem with OB's is extremely low efficiency at low frequencies, because of the massive acoustic cancellation. With an OB, required cone excursion and/or area goes up with a factor of 8 per octave - 20 Hz requires 8 times as much as 40 Hz.
I wanted to get 100 dB @ 20 Hz with less than 1% THD, and to really get that you see how much cone area is required.
Sure, a 15" can work well down to 40 Hz or so, but never to 20 Hz.
Both woofer towers are placed at equal distance from the listening position. The main dipoles are B&G RD-75 ribbons placed in the middle between each pair of woofers. The ribbons are delayed to match with the woofers. It is optimized for a single listening position of course.
Front wall is near-anechoic as you suspected.
One thing I've wondered about is why you don't increase the path difference D to increase the low frequency extension. Since you have so many woofers and they are all active you should be able to turn say two of the arrays into pure subs with very long path difference, say 1-2 m but only play up to say 40 hz.
Increasing the path length will lower the upper usable frequency, and I XO at 200 Hz,which is the absolute maximum for the path length I have here.
An other thing is that I want all woofer towers to play the entire 20-200 Hz range. The reasons are two: 1. I want the woofers to have approx the same height of the wave-front as the main ribbons. 2. With only one woofer tower per channel playing up to 200 Hz, stereo image is affected since the distance between L and R channels will not be the same for the woofers as for the ribbons. Its also easy to hear the location of the bass towers with only one of them playing. With both of them covering the same frequency range, they form a phantom source between them, which is exactly where the ribbons are placed. In other words, the entire frequency range sounds like coming from the same location and with the same height of the wavefront.
An other thing is that I want all woofer towers to play the entire 20-200 Hz range. The reasons are two: 1. I want the woofers to have approx the same height of the wave-front as the main ribbons. 2. With only one woofer tower per channel playing up to 200 Hz, stereo image is affected since the distance between L and R channels will not be the same for the woofers as for the ribbons. Its also easy to hear the location of the bass towers with only one of them playing. With both of them covering the same frequency range, they form a phantom source between them, which is exactly where the ribbons are placed. In other words, the entire frequency range sounds like coming from the same location and with the same height of the wavefront.
But two of them in a 3 m x 2 m x 1.5 m steel-reinforced-concrete folded horn works pretty well...
Stig, you should acquaint yourself with the LEDE work of various studio designers such as Dave Davis if you haven't already.
LEDE = live end dead end
from sweetwater sound site:
LEDE - Live End, Dead End
LEDE is a trademarked term for a particular acoustic design. In an LEDE studio, the area around the monitors is deadened, or made absorbent acoustically. The remainder of the room (behind the listener) is made "live" or reflective. The main principle is that the arrival of reflections at the console is in a specific order: 1. direct sound from the monitors; 2. First studio reflection (from the recording room, through the mics and monitors); 3. First control room reflection (off the back wall, assuming it is 10 feet or so behind the engineer). The idea is that by staggering these arrivals, the control room reflections don't interfere with monitoring recorded studio acoustics.
or
Recording Studio Design, 2nd Edition > Chapter 17 The Live-End, Dead-End approach - Pg. 437: Safari Books Online
There is a lot of previous work in these areas that can be beneficial to know.
Alan Garren
Yup, LEDE is the way I designed the room. However, with a diffusor covering my entire rear wall, there really is no "first control room reflection", as you can see from the ETC below.
An externally hosted image should be here but it was not working when we last tested it.
I found the same thing too, and I almost wanted to accept that OB's could not give the same bass "impact" as boxed woofers, because OB's dont pressurize the room.....
However, when I switched to Ncore amps for my OB woofers, the whole thing changed. Its amazing how much better the Ncore is in the bass range than other amps I've tried (including UcD 400 HG), especially when it comes to transient "attack", overall clarity and control.
( are we back ontopic again now perhaps..?
)However, when I switched to Ncore amps for my OB woofers, the whole thing changed. Its amazing how much better the Ncore is in the bass range than other amps I've tried (including UcD 400 HG), especially when it comes to transient "attack", overall clarity and control.
( are we back ontopic again now perhaps..?
Transient attack and clarity are hallmarks of OB sound, and I don't question that also the Ncore excels in that regard, but overcoming the acoustical limitations of OB bass is a different matter IMO, and it would be the first time for an amplifier to rewrite the laws of physics
.But yes, better go back on topic now.
I found the same thing too, and I almost wanted to accept that OB's could not give the same bass "impact" as boxed woofers, because OB's dont pressurize the room.....
However, when I switched to Ncore amps for my OB woofers, the whole thing changed. Its amazing how much better the Ncore is in the bass range than other amps I've tried (including UcD 400 HG), especially when it comes to transient "attack", overall clarity and control.
( are we back ontopic again now perhaps..?
Could it be that the very high damping factor plays a more important role for OB woofers than boxed (acoustically suspended or resonant) ones?
You also obtain much more modulation distortion due increased cone travel for the same output at low frequencies compared to the same woofer in a box.
Wonder how just two of Erik´s woofers would sound in a well designed bass reflex enclosure (which so very few really masters).
- I bet it would be out of this world in rooms that can handle it
Well, we are OT again. I've had closed box and bass reflex woofers of many kinds, they were all vastly inferior in sound quality compared to any OB I've ever heard. The main reason is how they behave in the room. But the penalty you pay is very very very low efficiency....
I don't think amplifier quality or damping factor is more important with OB's, but the lower coloration of OB's probably makes it easier to hear the difference in sound quality between amps.
I don't think amplifier quality or damping factor is more important with OB's, but the lower coloration of OB's probably makes it easier to hear the difference in sound quality between amps.
You just do not want to understand what I want with the 0,1 ohm. You have a short memory to. The N Core was never for me.
Why don't you open your own thread about what you are (trying to) explain, since it has virtually nothing to do with Ncore....
Sorry about that, I was harsh but mostly to discourage builders from taking your design of OB bass *before* exhausting the vastly simpler and cheaper alternatives. You obviously know what your system does and why, and the details are appreciated. I view it as important experimentation at the extreme of bass design.
Here's my project, FWIW:
I have a pair of very good small monitors (ATC20SL passives) waiting to replace some good but worn-out 2-way minitowers. I plan to buy a couple of Velodyne DD10+ or DD12+ powered subs. I'll have heavy (~20Kg) stone slabs made with the same footprint as the ATCs to act as bases. So, from top to bottom: ATCs, ultra-thin patches of blu-tack or silicone, slab maybe 3" thick, aboiut 1/2" thick sorbothane or heavy foam pad, subwoofer cabinet, Sound Anchor stand, and finally spikes, or bolts which the lock the stand to the floor. I want to strongly isolate the monitors from the subs in the face of the stacked mount.
The ATCs, like all 2-way speakers, are time-coherent along a specific plane. Fortunately that plane for these monitors (mounted vertically) is very close to horizontal. The subs and stand could switch places, but I want all the drivers close. That's a tradeoff, maybe a poor one, since floor reflection will compete with the higher subs' direct radiation; I'll think it over. The stands are custom-made so I'll have to choose the final arrangement before building. The room is narrow and untreated. FWIW, I expect those Velodynes to achieve as low distortion, but *only* in direct radiation, not accounting for the room reflections, as Stig's system...
Here's an area where I differ from the mainstream: I believe that if a rectangular room has reasonable dimensions for audio, ie something not too far from golden ratio LxWxH, then the quality of speakers vastly outweigh room considerations. This assumes speakers are well-placed and also achieve for time coherence at the listening position, AS WELL AS being not-far-from time coherent for first reflections for all of the walls. The ceiling and floor reflections are casualties except in the case of horizontal driver mounting. The need for front- and back-wall coherence is the reason I advocate little or no toe-in on most systems.
OK, back on topic
, I have a pair of Bel Canto S300Es which I intend to vertically biamp. I wish that high-end preamps came with parallel outputs for this to avoid kludgy cable terminations, but never mind. I would like to replace them with ncores biamped the same way. I'd like to hear others' thoughts on cables for the ncores...Cheers
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Then do remind me. But please, in a private message or in a separate thread. It is clear the nCore was never for you - the only thing unclear is why you keep posting in this thread. Unless you are on of these guys:
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