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David Ketley
03-20-2011, 08:36 AM
I run an active 4 way system using Ashley 4001 and there 31 channel Eq but want to time align the speakers. I can do two physically but not the Urei coax unit and horn loaded bass.
Is there a simple stand alone unit that would do this without all the hassle and complexity of going digital?

Dave

loach71
03-20-2011, 05:00 PM
There are many analog active crossovers that feature "all-pass" filters that allow user selectable time delays. Even some of the el-cheapo units like Behringer have that feature.

David Ketley
03-20-2011, 05:27 PM
Anything that would give the same quality as the ashley?


Dave

Allanvh5150
03-20-2011, 09:59 PM
Keep your eye on ebay for Brook Siren crossovers. Easy to change frequencies, time alignment and they can also adjust the phase at the crossover point. They also have built in limiting as well.

Allan.

yggdrasil
03-21-2011, 04:01 AM
I have been looking into all-pass filter for time delay, and I simply cannot understand that it will work as intended.

It is my understanding that an all-pass filter shifts phase, and a phase shift will give different time delay at different frequencies. To me that means that the all-pass filter will delay a 20KHz half as much as a 10KHz tone, and the delay will be 1/10 compared to a 2KHz tone.

Don't know if this makes any sense, or if it is correct understanding of the all-pass filter. If it is wrong, please try to educate me!

Johnny

grumpy
03-21-2011, 06:49 AM
if the phase shift were able to be fixed at one value, then yes, one would
see a linear relationship between frequency and delay. If the all-pass filter
is designed to have a linear relationship between frequency and phase shift,
then the delay can made to be constant (over a reasonable frequency bandwidth).

One described fully-passive example (many other topologies exist
including active [still analog]):

http://en.wikipedia.org/wiki/Bridged_T_delay_equaliser

Note in the article that 33uS of delay is accomplished with one such filter stage
when a 15kHz bandwidth is required. More delay can be introduced (per stage)
if the maximum frequency is reduced (such as in a low pass filtered crossover).

1audiohack
03-21-2011, 10:39 AM
In short you only get up to one rotation or up to one wave length of delay per all-pass stage right? One would first have to determine if that would even be useful.

Charlie Hughes has a couple of good papers on all-pass uses including the demystifying of all-pass crossovers on his Excelsior Audio website, look in the publications pages, when I get near a computer I will post a link.

Allanvh5150
03-21-2011, 11:46 PM
In the late 70's and early 80's everyone was hell bent on time alignment. All very nice doing so but after the various frequencies propogate, they will be further and further out of phase. They sure start off in phase but after that it becomes abig jumble. IMO spend your money on some improvements that you can hear.

Allan.

Mr. Widget
03-22-2011, 05:51 PM
In the late 70's and early 80's everyone was hell bent on time alignment. All very nice doing so but after the various frequencies propogate, they will be further and further out of phase. They sure start off in phase but after that it becomes abig jumble. IMO spend your money on some improvements that you can hear.I agree 100%.

I would put it in a slightly different way though: After you have addressed everything else, experiment with time alignment. The effects are both measurable and audible, however improving the system with time alignment isn't plain or simple.


Widget

David Ketley
03-23-2011, 02:47 PM
Well I suppose Ive solved my own problem. Im running a 4 way system using A Heil tweeter crossing at 5000hz down to a JBL 2344 bi-radial horn down 1.2hz to a Urei 801 (its the stunning mid unit out of my 813Bs) down to 1850 horn loaded bass 120hz. All run through an Ashley 4001 analogue active crossover with 4 Musical Fidelity amps.
Everything but the 1850 horn is moveable and it is just incredible the difference speaker placement makes. I have spent many days trying things in different configurations and in the end have ended up with everything stacked vertically on top of the horn lying on its side except for the Heil tweeter which is alongside the JBL 2344. So everything is aligned vertically but the Heil tweeter and of course I have aligned the speakers as near as possible to get the voice coils in line. When its right the sound becomes quite ethereal with the speakers just disappearing. Time align does matter. I think there is a lot of confusion mixing time align and phase shift my understsnding is they are not the same.
Dave

Mr. Widget
03-23-2011, 04:34 PM
When its right the sound becomes quite ethereal with the speakers just disappearing. Time align does matter. I think there is a lot of confusion mixing time align and phase shift my understsnding is they are not the same.I am glad that you got a sound that is working for you... I'd love to hear it and I bet it sounds great, but I doubt that if you measured the impulse response that you would have anything close to the singular pulse of an actually time aligned speaker system.

I am not suggesting that you are wrong about what does or does not sound good, but based on my experience, getting a four way to be actually time aligned and not using test equipment and DSP to get it there is a near impossibility. I would suggest that you consider making your next system upgrade in your crossover. I have used the Ashly and it is good, but if you are going to this level of care, you would very likely hear the improvements in using a Marchand or one of the other really great crossovers.


Widget

David Ketley
03-23-2011, 04:55 PM
Iím sure your right Wigit I was reading somewhere its possible to get near to perfect using a signal generator at the crossover points and checking the response and moving the speakers . I donít have access to test equipment but brought the Ashley crossover as one highly thought of by the Forum but we always seem to be trying to hit a moving target in this obsession with music!
Is the Marchand analogue or digital? Im really trying to keep things as simple as possible
using the Heil tweeter allowed me to get the EQ out of the signal path I was trying various JBL horns with EQ but the Heil just sounds right.

Dave

Mr. Widget
03-23-2011, 10:31 PM
...the Ashley crossover as one highly thought of by the Forum but we always seem to be trying to hit a moving target in this obsession with music!I bought and used the Ashly several years ago but as I tried better equipment I felt the need to change it out of the system. I am sure some people do play follow the leader, believe the latest reviews and itch to get something newer and "better". For me it is always a matter of what sounds better. I have been lucky enough to be in a position to borrow a lot of gear and I have found that at a certain level cost and how new something is do not always correlate to better sound. I have a fairly pedestrian system, but I think it sounds pretty darned good and the core hasn't changed in a few years, the speakers came along last year and have settled in nicely. I am currently looking for the right preamp. (The right preamp is the most transparent one I can afford. :))


Is the Marchand analogue or digital? Im really trying to keep things as simple as possible...Marchand makes quite a few different models. I believe they are all analog. I really like their top tube model.

I agree, no EQ is the best EQ... but your system and room need to cooperate. I haven't used an EQ in quite a few years. I do still have a pair of Whites in storage, but I'd only bring them out if I decided to revisit a 43XX system.

Widget

David Ketley
03-24-2011, 03:23 AM
I try and keep the signal path as simple as possible I use a SPL 2602 Volume 2 Volume control after the DAC to the Ashley and direct to the power amps. Its a surprise to most people that a volume control can be an relatively expensive piece of equipment and itself can have a profound influence on the sound.



Now I have got the speakers to my liking Iím looking at the signal going in after all rubbish in rubbish out!


Dave

richluvsound
03-24-2011, 04:08 AM
David,

not such a bad idea for what your trying to do . You are getting pre-DAC , crossover , etc.etc in one box. It is hard work at first , but you do learn fast . If I can get my head around it ,anyone can .

Rich

Mr. Widget
03-24-2011, 10:51 AM
I try and keep the signal path as simple as possible I use a SPL 2602 Volume 2 Volume control after the DAC to the Ashley and direct to the power amps. Its a surprise to most people that a volume control can be an relatively expensive piece of equipment and itself can have a profound influence on the sound.I have used a couple of different passive volume controls... they are theoretically a great solution, but they need to be carefully impedance matched to your source and load or they will very markedly change your frequency response. I have never been able to make one work for me as well as a good active line stage. Even when the response wasn't rolled off there was a lack of punch and immediacy... in your system you seem to have gotten it to work for you. Changing your crossover or other gear will change this delicate balance.

As for DEQX... it is fussy but powerful. I think it is a fantastic tool for designing and playing around in the DIY world, but short of using their digital in and out model with outboard A to D and DAC it isn't as good as a better all analog system. Their new HD versions are better (anecdotally, I have no personal experience) but there are other DEQX issues... for the right person I'd recommend them, but in general I'd go in that direction with caution.


Widget

pos
03-24-2011, 09:07 PM
The SPL volume2 is an active volume control.
I am using the volume8 (8 channels version) in my setup and like it a lot. But on the other hand all my amps (old yamaha pro amps) also have a passive volume attenuator...

grumpy
03-24-2011, 09:51 PM
Thanks for posting that ... Looks like a nice unit with
several applications... Some of which would be otherwise
difficult or messy... particularly the 8ch tracking.

Mr. Widget
03-24-2011, 10:24 PM
The SPL volume2 is an active volume control.So is it a unity gain line stage without input selection capabilities?

Widget

pos
03-25-2011, 02:38 AM
I don't think it is strictly unity gain. There are no input selectors.

http://spl.info/hardware/monitor-controllers/volume8/rear-panel-specifications-measurements.html

One thing I will check is the matching between channels at different positions.

grumpy
03-25-2011, 11:11 AM
(Noting that I have a particular application in mind... but only peripherally related
to time-alignment)

To do much 'better' (e.g., 8ch balanced active with stepped attenuators) would be
-much- more costly. SPL may be converting to SE internally (fewer potentiometers)
then back to balanced, but I expect (opinion warning here) that this type of box
would be good or better than using an A/V receiver's 7.1 inputs to throttle multi-channel
DAC outputs before going into an active 4-way speaker system... a third alternative being
to reduce the DAC systems gain digitally (or A/D/A input level); which seems like a
non-optimum path to go down.

pos
03-25-2011, 11:18 AM
yes it goes to unbalanced using custom made circuits (they do have very low CMR), and then throug an ALPS potentiometer.

here is a photo of the internals of the 2 chanels version :
http://www.6moons.com/audioreviews/spl/open.jpg

the input/output cards are on the top left.

the 8 channels version is very simlilar, only with 8 of these cards and a longer potentiometer

David Ketley
06-13-2011, 03:00 PM
Another upgrade that's proved very cost affective using the Musical Fidelity USB V-link bypasses the sound card and gives a very clean signal to the DAC. All digital volume controls on max as it seems to affect the sound?
CD still sound best ripped to hard drive then played rather than direct not sure why? I run 4 Musical fidelity power amps direct with no pre in circuit hence the SPL Volume2.