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Thanks for the reminder about the heavy power demands EQ in the bass can make.My work-in-progress - budget - system will use two biggish stereo power amps to drive two pairs (IE 4) of stereo subs in an arc under and to the side of QUAD 63s. The QUADs amp is filtered at 150Hz 1st order.)
The subs amps are filtered at 3rd order, to match. One amp is a 380 WPwpc RMS (mimimum) serviced Perraux 6000C, and t'other amp is a HK 870. Which has a 60 amp peak output capability, and 100WPC into 8 ohms. The Perreaux has gain controls and so do the two eq'rs.
Both amps will see about a 4 ohms load.
Each bass channel, L&R will be Eq'd using rebuilt 1/3rd octave Eqs. Why not DSP? I'm a pensioner. Maybe, one day!?
Remember that this is a distributed 'Storm' array ala Duke's proven ideas. I might NOT need much Eq for the room's peaks, but for dips? ...
BUT, the Eq to get down real low, mostly from the sealed boxes, could chew up quite a bit of power.
I will have to suck it and see.
I am going to obtain a length of those strong 'raised flat triangle section' plastic channels to run all the wires under!! and reduce trip hazards, for ME?!
I was going to use the Perreaux to drive the QUADs but I then lucked onto a Fostex 300 power amp (150wpc/8) which was blue-printed, and it is guaranteed to cope with 'stats.
Two of the subs are large DIY sealed & stuffed push-pull driver items (one with 10s 88db/w and one with 12s 90db/w) and will sit under the 63s. The other two will be EBShelf rb enclosures and will sit on the inside of each the Quads. Ports and drivers facing the floor via pucks / cones.
Any thoughts?
Two of the sealed boxes are built, but not stuffed, and one EBS box built and driver mounted. Once I am fit enough to lift big boxes I should have the remaining 3 boxes built and installed in a few months.
Finish on the subs? I hope to get the subs coated / painted to match the black mesh QUADs.
In the interim I do have 4 35-30Hz capable spkrs for interim duty, one pair of which are able to be stands for the QUADS. So I'll be doing a good bit of learning about Eq and power demands.
I will report back.
Maybe I'll need to find a second Perreaux 6OOOC! One per L & R bass channels but into two boxes per channel.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Edits: 05/04/17Follow Ups:
I suggest using a multi band parametric equalizer rather than a 1/3r octave equalizer. That gives more versatility, and one channel equalizers are relatively inexpensive. IMO electronics quality is less an issue when only EQing bass. Also suggest only cutting down peaks, as dips tend to occur due to standing wave cancellation effects and are better addressed by moving the subwoofers or the listening position.
I have a single dipole subwoofer with ESL57s, but I did the crossover much lower, around 63 Hz, with a passive roll-off to the Quads and a 4th order active to the subwoofers, approximating a Linkwitz-Riley crossover (the Quads plus 6 dB/octave approximate 24 db/octave in combination. YMMV.
before servicing costs, and I am on a quite limited budget.Smallish room and near-field distances. QUADs at about 1/3rd from the 'front wall' and angled in to give a 'cozy' two-person-wide listening seat. Side walls into those front corners will contain two large solid timber bookshelves full of music books magazines, scores, librettos, and audio mags.
Immediately behind the QUADs will be the existing large tall fabric covered diff-sorber panels. To absorb some of the back-wave from the QUAD's slight inward angling.
I will stick with asymmetric odd order slopes, and a stereo feed - to an arc of 4 subs at the same distance from us under the QUAD 63s, and just outside their inner edges.
The asymmetric crossover slopes and frequency (150Hz) will allow me to play the system a good deal louder than a lower frequency would, while retaining some of the 63s bass clarity.
I understand that it is more suitable to omnipole / box subs, when added to dipoles.
And, I will at least have time coherence overall, and retain time and phase coherence from the QUADs.
I will be using a pair of spherical enclosure (8"2-ways 35Hz) and a pair of Jamo 3-ways ( <30Hz) under the 63s and will be able to do a lot of learning.
It's our L-shaped lounge-dining room and is not exactly 'mine'. So, with the final array I may end up putting the two inner subs (tall Rbs) on their sides / on rollers, for when I'm not listening. Thus leaving a passage-way for guests.
I've had a pair of 63s run FR up on stands in this room for a few months, so I know that this positioning will work very well, and the thirds spacing won't hurt with the subs, either.
I am hoping that the swarm array will fill in some of the shallower notches and dips, and smooth out the peaks a bit.
Putting the movable RBs ports and drivers up top may also help with smoothing.
We shall see.
I expect it will be < a year until I have settled on positioning and finished building the three subs, making 4 with the Rb sub I already have.
In the longer term I will either buy / build two mono bass-range 10-150Hz parametric equaliser boxes. My learning and RTA graphs will tell me how many FR range | <-> | and Q knobs I will need, except below 30 Hz.
OR I'll go with FR DSP and room Eq.
I'm not yet persuaded that DSpeaker/s single clever little box is transparent enough. Even WITH a dedicated high-end ADC (a kit of course) after the analogue sources' pre-amp. High-end commercial ADCs are not common.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Edits: 05/13/17 05/13/17 05/13/17
Here is my take.Over the years I have set up lots of budget systems, sometimes using things for pre-amps and amps most 'philes would not consider (or tolerate).
The 6000C seems to be a decent choice for running (2) four ohm subs in stereo. 500WPC into 4 ohms stereo and at 55 pounds, one can probably assume this amp has some good damping factor characteristics (aka, good size supply rail capacitors and transformers, which are important for Class AB amplifiers like that. (Class D amps can weighing 10 pounds can delivery 1000W..)
The push pull amps use 10" drivers and are 88db 1w/1m sensitive?
What is the impedance of each driver in the box and how are they connected?If you provided the specs (or at least model) of each driver, someone could better help getting the most out of that specific combination of amps and boxes.
To figure this out you want to try and estimate the maximum power output of each box and how much input power is required to get there. This will help you decide which amp to run on which boxes.
The HK is a good amp, but remember that 60A peak power (likely total, and not per channel else they would have said so) at 8 ohms is 240watts per channel peak. Not as impressive sounding... This is not rated for four ohms (no specs given) but is four-ohms capable.
So what's the plan here? Put the larger amp on the more efficient boxes to maximize output? Or put the bigger amp on the less efficient box to try and have some sort of level matching this way? The HK probably does about 150W/ch at 4 ohms... maybe 175. It won't double with a damping factor of 150. You need to get into 750+ numbers to do that. (Also, this damping factor could be averaged over a range of the spectrum... this is often done. An amp with a damping factor of 500 at 250Hz can be below 100 at 50Hz.)
Next calculation is to see, for each connection option, which unit bottoms out first in each case. I bet the 6000C could drive either pair of subs to full excursion, possibly without even clipping. In the case of the HK, I would bet the amp starts to suffer first, with the PS rail voltage getting dragged down considerably during heavy bass power surges. This can lead to the kind of distortion that can cook woofer coils, or cause excessive heating in the amp, but worst of all, distorted uncontrolled bass. The opposite of tight, clean bass. (Once you've heard super-powered amps and high quality woofers that don't "thump" but can actually pound and *hit*, when you hear loose distorted bass it makes your skin crawl.
There is really one question here: given the type/nature of each sub box and each amp, is there a way to best match them up, OR is using both pairs and both amps not going to be an optimal solution anyways?
Do you have separate circuits to the room? If both sub amps are on the same circuit, I would not have the HK and the less sensitive box dragging down the AC supply voltage if only delivering a smaller chunk of the over-all SPL.
I suppose the "multiple subs for smoother response" will be a factor in this, but I have a feeling the HK amp will be a limiting factor and possibly even do more harm than good depending on how your audio room is circuited.
Cheers,
Presto
Edits: 05/07/17
With push-pull you are looking at -3db so actually 87db/w. These may need an Rb enclosure.The 12s are 93db/w and 8 ohms, 23Hz. So sealed p-p gives around 90db/watt.
The big rb Sub is an old design but IIRC is about 90db/w, 8 ohms, and ran happily off a 100 watt amp with hard use.
Its partner will use a new Canton 26cm woofer which is 3.5 ohms and 91db/w, and can handle 100watts. Similar box size and port.
I'm hoping that both Rb subs will get down to their Fbs without needing heaps of power and that's why I will use the HK 870 for them, to start with.
I will be sitting down with a box-plotter for all three box builds and make sure I'm getting down low enough before the EQ is added. I do have all 5 driver's TS's to do that with.
The room does give room gain > ing as f falls, but it's not a concrete room!
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Edits: 05/08/17
Timbo:
I think you should try the HK as you have planned and see how it goes. See how "tight" the bass seems... of course, there is more to it than just response. Just look for signs the HK is struggling... one is distortion the other is excessive heat.
I read your other post... you have lots of copper going into that room so voltage drop should not be too much of a problem. Running big amps on their own circuits is always a good move. I suppose it could be fun to switch amps and boxes to see how things sound. It is tempting to put more power behind the drivers that have higher xmax... but it's also important to know if there are any potential issues with "unloading" of the sub driver, aka where a subsonic filter should be used. Super-lows just rob amp power and move the subs voice coil out of it's sweet spot, as far as it's B-L curve is concerned.
I am not aware if you have a preliminary plan for placement. There are theoretical "optimal zones" to put subs in multi-sub applications for the flattest response (most even excitation of different room modes).
For two subs, I think it was one in a corner and one on the center-line of a given wall. My understanding is that mirror image location of subs is *not* necessarily an optimal layout.
Cheers,
Presto
One is used to power the sources and pre-amp.So that leaves 4,800 watts of mains power available to run:
i) the Fostex SS amp OR the 40wpc strapped LEAK St20s, and
ii)the two stereo sub amps,
iii) active HP filter and
iv) the two Eqr's.Even with the slight inefficiency of SS circuits, and even with the valve amps draw of 200watts each in Winter - I don't think those two circuits will sag.
Feeding panels across the entire roof space there are two redundant 2.4KVA heating panel circuits. Some professional work would be required to redirect their cabling, and remove their timers on the mains power breaker box.
I would then have 4 x 2.4 KVA circuits to feed the power amps with!
Given all that spare capacity I have thought about going with balanced AC mains.
But I would prefer to do that first for the sources and pre-amp, using the existing 240V 10 AMP unbalanced circuit. It may be that an isolating mains transformer that also does balanced AC might be the best solution for the system's front-end.
Then there would be the task of dragging two or more big traffos into position under the house, and re-cabling to the wall outlets. Special wall outlets to meat safety laws and special wall sockets and differing plugs.
LBNL the various systems in that room have never been prone to mains-borne noise. Maybe I'd hear a lower noise floor but would it be worth > $Au2k?
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Edits: 05/07/17 05/07/17
I will have to suck it and see.
There may be a 6000B around.
That would be ideal.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Used this amp to drive two built in 10" drivers, would rattle my neighbors windows lol. Stable into 2ohms, rated 300watts/channel 8ohms, 400watts/4ohms, doubles down when bridged making 800watts, this amp never breaks a sweat and will run any load BWAAAAAA HA HA HA HA HA, he laughs his evil laugh.Martin
Edits: 05/07/17
;-)!But, I will keep hanging out for a Perreaux 6000B or C!
Lots of power and individual-channel gain controls.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Edits: 05/08/17
The four subs will be in arc at the same distance as the QUAD 63s are from the listening seat. 2 cosy people wide.
The cones/Ports will be as far from each other as possible ~ 4 feet apart.
Initially I'll be borrowing an RTA, mike and using Stereophile's test CDs, with the graphic Eq's.
RTA SW for my android tablet and a decent mike is going to go on the savings budget.
I will try switching one of the subs to OOP to see what happens, and back in phase, then the next, and so on.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
A SubHenge. Sweet! That works and works well, in my experience.
If you have the ability to adjust phase, you might try putting the two subs on the left in "phase quadrature" (90 degrees of phase shift) relative to the two subs on the right. This technique was suggested by David Griesinger as a way to synthesize hall ambience from a source whose bass has been summed to mono.
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
I will try all of them.
Most of the recordings I care about will be classical and made with a stereo base at least.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
So I'll be doing a good bit of learning about Eq and power demands.
Nulls are effectively black holes in terms of trying to correct via EQ. While I get remarkably smooth response upstairs in my treated room, the HT suffers from nulls at 40 and 80 hz. I just attenuate the peaks around them and live with the results. :)
"Nulls are effectively black holes in terms of trying to correct via EQ."
A big +1 10-4 on that!
It's not possible to use a frequency/level domain "solution" (whether graphic, parametric, or digital) to fix what is fundamentally a time domain problem.
Peaks can be tamed a bit, but only at the expense of the direct sound source quality. With nulls, you're pretty much screwed without making physical changes to the room.
:)
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