ply too - the bonding glue is nasty on the lungs... fyi.
_-_-
PS. Is Debbie coming over to help stand them up??
I was referring to the idea that IF they are an exact fit to the ceiling, then they can't be stood up
because of geometry (unless you blast a hole in the floor or ceiling somewhere to permit them to
stand up first and slide them into place... just wondering about this...
_-_-
PS. Is Debbie coming over to help stand them up??
I was referring to the idea that IF they are an exact fit to the ceiling, then they can't be stood up
because of geometry (unless you blast a hole in the floor or ceiling somewhere to permit them to
stand up first and slide them into place... just wondering about this...
Not sure if you are asking wesayso or myself but floor-ceiling coverage only mean that the array run full height, not necessarely covering each and every inch of available height. Putting them would then as you indicate would prove difficult due to geometry
Wesayso have his placed already at their intended location so he is good I however can completely cover all available height since mine will be placed under soffits that extend 8" below main ceiling
Raise them up under full height and then move them backwards into their final location.wesayso - I have asked for final quotes now from four dealers, two US-based and two in Germany so we'll see how that turns out
And yes, I will post a specific thread for my build when I get to that
I figured that remark was aimed at you Haldor, hence Debbie with: One way or another... I'm sure you'll find a way to place the speakers...
I do agree about the sawdust though, nasty stuff! Better wear protection.
Haldor, what are you going to use EQ wise? Have you figured that out yet?
Good to read you're planning a build thread. Looking forward to that.
I do agree about the sawdust though, nasty stuff! Better wear protection.
Haldor, what are you going to use EQ wise? Have you figured that out yet?
Good to read you're planning a build thread. Looking forward to that.
As far as EQ goes I am pretty much undecided wether to utilize passive or active means to achieve a proper response. Part of that being not knowing what to expect from the full array or the performance in-situ.
Should I value the high end or try making it go deeper, I dont know
I am seriously considering making two simple boxed line arrays first to get experience with the performance prior to making the finished pair, and take it from there. That mean I need to order the speakers soon
I am usually a big fan of keeping things simple, my time is limited (father of 4 and the youngest kid is 4weeks old) so a simple passive solution have appeal. So anything that I can do with wire is quicker...Probably use no EQ whatsoever initally in order to establish a base line. Any input/tips on that matter would be appreciated
Active EQ offer much greater flexibility but I believe I first need to localize the issues first before I decide. In other words, to be determined...
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After a couple of weeks of travel I am back home, got a quick question and hope someone will have the answer
Not specific to LA but since wiring can be done in a multitude of ways and different resistance can be achieved - what would be the determining factor for choosing say 4/6/8ohm nom. resistance? Purely matching resistance to amplifier or are there other contributing factors?
My current amp is 4ohm stable (125W/8ohm and 200/4ohm) so should I aim for 4ohm or perhaps 6? Since resistance isnt constant would my ideal be 6ohm ? Curious
Not specific to LA but since wiring can be done in a multitude of ways and different resistance can be achieved - what would be the determining factor for choosing say 4/6/8ohm nom. resistance? Purely matching resistance to amplifier or are there other contributing factors?
My current amp is 4ohm stable (125W/8ohm and 200/4ohm) so should I aim for 4ohm or perhaps 6? Since resistance isnt constant would my ideal be 6ohm ? Curious
After a couple of weeks of travel I am back home, got a quick question and hope someone will have the answer
Not specific to LA but since wiring can be done in a multitude of ways and different resistance can be achieved - what would be the determining factor for choosing say 4/6/8ohm nom. resistance? Purely matching resistance to amplifier or are there other contributing factors?
My current amp is 4ohm stable (125W/8ohm and 200/4ohm) so should I aim for 4ohm or perhaps 6? Since resistance isnt constant would my ideal be 6ohm ? Curious
Personally would take one of your drivers, build a box that would simulate the same Vb as if in a LA and sweep the impedance curve. Often times this will be lower than expected. Determining this first would lead you down the correct path. Am running a 2Ω stable amp with 8Ω drivers run in parallel. Unlike most the actual impedance of this driver never dips below 8Ω so when paralleled up stay above 4Ω at all times. Am running active with multiple amps and is cheaper than passive, tho was originally designed as passive. Both options cost $$, but the active setup affords a flexibility that no passive can meet just in case you decide to tweak, which we all do in fine tuning and or voicing a speaker without incurring additional cost.
Regarding sweeping to get impedance curve of a speaker. I just figured out how to do it using the fantastic REW software which has that capability built in. You just need to add some cables to connect the line out with two of the line ins on the soundcard with a single ~100 ohm resistor. Here is my first measurement. I have tried with TL and BLH speakers and they produce curves that show if your modeling is correct as there are mulitple peaks that result from the coupling of the enclosure with the driver. If you add mass the driver and repeat the measurement, REW will calculate the T/S params for you. I just saved myself from getting a $100 woofer tester.
Although I have not got hands on experience of line arrays I have noticed one important factor when running two drivers together. They sound better when run in parallel than in series. This is probably due to the entire voice coil of one driver sitting in the path of the other. You run decent quality cable from your amp then several meters of really thin cable of the voice coil. If you have any drivers already, set up a test cabinet to see how big a difference it makes. You do have to be careful in this type of test as the parallel wired will be louder at the same amplifier setting. I would personally go for higher impedance drivers so as to maximize the amount of parallel connections and minimize the series. Ideally dispensed with series wiring completely and use multiple amps.
Niffy
Niffy
Parallel sounds better because it is more efficient (+6dB) for same drive voltage. In series, the efficiency is the same but since impedance doubles, current is halved and I think efficiency stays the same because the increase in Sd is negated by drop in power at same voltage. Cone movement is less with series so potentially less distortion. With lots of drivers you go combo of series/parallel to get impedance back to something the amp can drive. I agree that having a bunch of 16 ohm or 32 ohm drivers in parallel sounds very good. I
3dB electrical gain due to the halving of impedance and 3dB acoustic gain when combining in parallel.
Regarding sweeping to get impedance curve of a speaker. I just figured out how to do it using the fantastic REW software which has that capability built in. You just need to add some cables to connect the line out with two of the line ins on the soundcard with a single ~100 ohm resistor. Here is my first measurement. I have tried with TL and BLH speakers and they produce curves that show if your modeling is correct as there are mulitple peaks that result from the coupling of the enclosure with the driver. If you add mass the driver and repeat the measurement, REW will calculate the T/S params for you. I just saved myself from getting a $100 woofer tester.
I'll have to use that when testing my damping materials! To see where the peak is at...
I followed these directions for REW: http://www.roomeqwizard.com/wizardhelpv5/help_en-GB/html/impedancemeasurement.html
I used two 3.5mm to RCA cables ( had those already) and qnty 3 RCA to solder joint panel jacks (had those already too). This let me plug the 3.5mm jacks into the line out and line in on the soundcard and I soldered a 150 ohm resistor onto 2 of the RCA jacks. Added a jumper to a third RCA jack and added two leads to the driver (with standard quick disconnect crimp connectors compatible with the tab terminals on all my drivers. I soldered another wire with an alligator clip on one end to one side of the resistor and use the other to bypass the resistor when REW asks for shorting the resistor to calibrate. That is it. It is a little tricky to figure out how to calibrate sound card (short resistor) and then you have to calibrate impedance measurement by shorting resistor again.
Works like a charm and provides very high quality low noise data as you can see.
I used two 3.5mm to RCA cables ( had those already) and qnty 3 RCA to solder joint panel jacks (had those already too). This let me plug the 3.5mm jacks into the line out and line in on the soundcard and I soldered a 150 ohm resistor onto 2 of the RCA jacks. Added a jumper to a third RCA jack and added two leads to the driver (with standard quick disconnect crimp connectors compatible with the tab terminals on all my drivers. I soldered another wire with an alligator clip on one end to one side of the resistor and use the other to bypass the resistor when REW asks for shorting the resistor to calibrate. That is it. It is a little tricky to figure out how to calibrate sound card (short resistor) and then you have to calibrate impedance measurement by shorting resistor again.
Works like a charm and provides very high quality low noise data as you can see.
Just a follow up on using REW to measure T/S params: I tested it out to measure an off-spec Eminence Beta 12CX. I used a ring of modeling clay to add mass (used a digital gram scale to weigh a 75.8 gram donut shaped ring). It works really well - very easy to use. You can see the T/S model plotted against the measurement to see that the fit is quite good.
Results:
Results:
Code:
TS Parameters file
Zmin 6.47 ohm
fmin 181 Hz
f3 625 Hz
Le(f3) 1.105 mH
Motional impedance parameters
RES 159.53 ohm
LCES 20.462 mH
CMES 414.3 uF
RAMS 159532.129 mohm
Blocked impedance parameters
RDC 5.50 ohm
dR 0.18 ohm
Re 5.68 ohm
Leb 217.2 uH
Le 2.953 mH
Rss 922.4 ohm
Ke 0.1082 S-H
Thiele-Small parameters
fs 52.8 Hz
Qms 3.178
Qes 0.781
Qts 0.627
Fts 84.2
Mms 34.44 g
Cms 0.264 mm/N
Rms 3.594 kg/s
Vas 112.43 litres
Bl 9.118 Tm
Eta 2.07 %
Lp (1W/1m) 95.31 dB
Dd 26.41 cm
Sd 548.0 cm^2
Added mass 75.80 g
Secondary measurement: Beta12CX Clean+75.8g
Air temperature 20.0 C
Air pressure 1013.25 mB
Air density 1.2041 kg/m^3
Speed of sound 343.2 m/sAttachments
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Passive EQ on a line array would be a disaster. It needs too much boost at both ends of the response, especially the low end, and the impedance of any driver is a long way from flat. You will want to tweek it many times, and it will be a total hassle each time to get what you want with passive EQ.
Active EQ is predictable, accurate and relatively easy to modify later. Behringer has some questionable analog circuits in some of their digital EQs, so I don't recommend Behringer products, but something like that might be best for those who aren't set up to build active analog EQ circuits.
And on the parallel vs series issue, it's not nearly as big a deal as some think. The DC resistance is effectively in series with the driver at any audio frequency, so it's not like you can get rid of that by using all parallel wiring. Yes the lower impedance gets more power out of a given amplifier, but at the expense of amp reliability. I always prefer 8 ohms. It seems like the right set of tradeoffs.
Roger Russel, formerly of McIntosh, offers his IDS-25 Line Array system for about $19000, and it's all series/parallel wiring to get back to 8 ohms as seen by the driving amplifier. He thinks it sounds great. The drivers will be slightly less damped electrically, but it's anyone's guess whether that makes it sound better or worse, or any different at all.
Active EQ is predictable, accurate and relatively easy to modify later. Behringer has some questionable analog circuits in some of their digital EQs, so I don't recommend Behringer products, but something like that might be best for those who aren't set up to build active analog EQ circuits.
And on the parallel vs series issue, it's not nearly as big a deal as some think. The DC resistance is effectively in series with the driver at any audio frequency, so it's not like you can get rid of that by using all parallel wiring. Yes the lower impedance gets more power out of a given amplifier, but at the expense of amp reliability. I always prefer 8 ohms. It seems like the right set of tradeoffs.
Roger Russel, formerly of McIntosh, offers his IDS-25 Line Array system for about $19000, and it's all series/parallel wiring to get back to 8 ohms as seen by the driving amplifier. He thinks it sounds great. The drivers will be slightly less damped electrically, but it's anyone's guess whether that makes it sound better or worse, or any different at all.
I am going to actively EQ the signal for sure, Behringer is easily accessible here in town but I am open to suggestion for other A/D-EQ-units thats worth a look
What kind of impedance I will end up with will be determined later, this is not a critical decision at this time, though my thoughts are circling around 6 or 8 ohm nominally.
What kind of impedance I will end up with will be determined later, this is not a critical decision at this time, though my thoughts are circling around 6 or 8 ohm nominally.
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I am going to actively EQ the signal for sure, Behringer is easily accessible here in town but I am open to suggestion for other A/D-EQ-units thats worth a look
What kind of impedance I will end up with will be determined later, this is not a critical decision at this time, though my thoughts are circling around 6 or 8 ohm nominally.
I use miniDSP (on other speakers) and think that the SQ is very good. I measured the effect of the miniDSP ADC and cannot see any degradation in SQ nor hear it with my speakers and ears. There is also the nanoDIGI variant which lets you use your own DAC if you are picky about DAC SQ. Very easy to use and also gives you potential for XO to use with a sub.