hypex ncore

[Sam Lord]

Originally Posted by StigErik

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.

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.

Originally Posted by Immelman

No, very impressive! And with your comments, puts a stamp on the notion that to achieve ultra low OB bass in a home setting is nearly impossible. I didn't believe it before. Thanks.

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.

[StigErik]

Originally Posted by Sam Lord

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.

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.

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.

[OllBoll]

Originally Posted by StigErik

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.

[StigErik]

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.

[Sam Lord]

StigErik, thank you for explaining your design, would love to hear it someday.
Cheers, Sam

[Julf]

Originally Posted by StigErik

Sure, a 15" can work well down to 40 Hz or so, but never to 20 Hz.

But two of them in a 3 m x 2 m x 1.5 m steel-reinforced-concrete folded horn works pretty well...

[StigErik]

I was talking about Open Baffle .... not horns.

[waltzingbear]

Originally Posted by StigErik

Front wall is near-anechoic as you suspected.

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

[StigErik]

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.

[StigErik]

Originally Posted by pieter t

But I also like larger scale (symphonic) music, and in that respect I too often miss that very last bit of weight; the feeling of "pressure" at bass attacks as can be experienced in the concert hall is just not quite there with the OB bass.
For me it works OK for 80%, but I want that last bit too; it looks like I will extend OB down as much as possible, but will try a low tuned bass reflex for the lowest two octaves, up to 80 Hz or so.

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..? )