Well, it depends on your threshold for compression and distortion. I'm setting a very very high bar that should be well beyond audible. I'm assuming Ryan is using this for professional mixing purposes so I want this to really smash the targets with extra room for error. For home theater use, I would be less stringent and this wouldn't be an issue at all.
I think it's a good idea to set the bar high in this case, but that said, in a way what I really need is an exceptional studio monitor @85-90dB average @1.5M with up to a 30dB crest factor, and a very very good PA at levels higher than that. Ofcourse I desire the PA part to still be exceptional studio monitor up there, but something that could work well as a 3 way for now, with the option of adding a 15" to go between the subs and the mids later would probably be ideal. Is the a rule a rule of thumb regarding CTC spacing and listening distance? IE if you use the standard 13500/CTC rule of thumb does that work at say 1m no matter what? I thought that because the XO on the summa was a above or so close to the 13500/~16 that's what necessitates the ~2m listening distance. If I did say SEOS-18 and a pair of 8" woofers 13500/ 8.5 =1588. With an XO of ~1k shouldn't they come together quite a bit closer? I keep going back to the SEOS 18 with 8's for a super Daniel because it seems that there are a lot more options for a sealed system that could get in room extension down to ~100hz, and there are some mids that are a cross between true mid and mid-woofer. Like B&C 8MD51's for example, considering any sort of complex XO is an option with the W15's (subs will be active no matter what) it seems very doable to match to them while still maintaining very low xmax at the exceptional studio monitor levels. Or am I completely missing something obvious?
I don't recall you mentioning using these for PA duty. That might change the requirements a bit, but not necessarily. What exactly would you use them for in PA use? The dual 6NDL38's will be limited in maximum output especially at long distances. I wouldn't expect them to get past about 120-123db peak @ 1m. Dual 6md38/6nd430 would give you about 3-6db more, but would require a stout 12-15" pro mid woofer below. For PA use it is tough to beat commercial stuff from companies like QSC. The reason closer listening positions require wider null spacing (created through a combination of a lower crossover point and closer CTC spacing) is because the closer you are the shorter the vertical window you have where output is not affected by nulls. For the SEOS-15 with dual 6.5" drivers and a 1200hz xover point I'd estimate a half angle of 45 deg above and below your vertical on-axis for your null centers. If you were only an inch away, the window would be 2 inches. At 1m the window would be 2m. For a SEOS-15 with a single 15" woofer below and a 1200hz xover point, I'd estimate a half angle of 30 deg off-axis for your null centers. If you were 1m away, your window would be approximately 1.1m. The reality is that the window is quite a bit smaller though because you aren't using brickwall filters (or at least you shouldn't even if you could...whole other topic for another day). I generally give a rule of thumb of around 1/2 the calculated window height. So with the dual 6's at 1m you would have about a 1m window of even response. With the 15" woofer, you would have about a .5m window. Could it work with a 1m window at your 2m listening position? Sure, but I'd rather have a good 4m window where you know there is no issue. You could also used these as nearfield monitors up to a point (maybe .75-1m). Closer than that and you want a true NFM that has smaller drivers in even tighter spacing. I'm not sure I see much advantage to the SEOS-18 with dual 8s route. I'm not familiar with the 8MD51 as it is not currently made by B&C. The 6's I mentioned are tested and vetted. The SEOS-18 will cost more and be wider. The main advantage is horizontal directivity control an extra 50-100hz lower. The SEOS-18/dual8s route is possible though, you would just need to test a bunch of woofers until you find one that works as well as the 6ndl38 (or 6md38 or 6ND430 if only used above ~200hz). You might find something, but I simply don't have the data.
Right I think it sounds like either dual 6.5 over 15 or dual 8 over 18 sounds like the best bet, that makes perfect sense. Was just thinking that the move to the 18 + 8's would allow for low Xmax at reasonable levels from the mids, but mids that could mate to the subs in just a 3way. I think I worded the PA thing badly. I don't need an actual PA at all, just trying to say that I only need the exceedingly high standards up to a certain average dB level. Above that it would be OK if it slipped a little, especially if I have the option to add mid-bass drivers later to increase the capacity even more without rebuilding the whole thing. Thanks again though I'm going to read your last post a couple of times! Very helpful-
The SEOS-18/Dual8's setup is certainly possible. I would look at the B&C 8NDL51 or 18Sound 8NMB420. They are both in the $170-180 range. They both employ shorting rings and have good responses on their spec sheets. I don't know of any independent testing, but I'm sure they would perform well. I just can't say with certainty how they would compare to other options without independent testing. I haven't modeled them but I'd guess they would easily get you down to a 120-150hz xover in a sealed cab. Probably a tad better than the 6's. I think I see what you are saying about PA. At 2m I think any of these setups will give you what you need. It will give great on-axis, off-axis, constant directivity, wide vertical nulls, minimal dynamic compression and very low distortion.
Awesome the 8NLD51 looks really good, I found these. https://sites.google.com/site/drivervault/driver-measurements/faitalpro-12pr300/b-c-8ndl51/frequency-response http://s139.beta.photobucket.com/user/augerpro/library/BC%208NDL51?start=all and for the 18sound. http://s139.beta.photobucket.com/user/augerpro/library/18Sound%208NMB420?start=all Here it looks like the ferrite version 8ps21 has a little lower distortion than the neo: http://www.diyaudio.com/forums/multi-way/157137-critique-my-8-pro-audio-woofer-8-waveguide-compression-driver-plans.html Any thoughts on that? Also I know we are getting out of the realm of stuff that you or many people at all have experience with, but if I did go with either of the b&c 8's and a seos 18, would you stick with dna-360 or go with the BA driver or something else like bms 4550?
Also here is this. The desk is close to the dimensions it will be (not a mixing console, it's a desk with rack gear in it), I plan to lower the angled part a little when I re-work it. This is why I was thinking that if the vertical nulls can be tightened in a little bit, it would probably be a good thing to help avoid diffraction coming off the desk. The boxes in this pic would be big enough to hold seos 18 + 8's. I'll upload some real pictures also, thanks again.
the null won't really help with diffraction off the desk, it is only within a relatively narrow band around crossover.
Ok that makes sense, sorry I get the general concepts but don't have a lot of experience with all the details of them. But the narrow-ish vertical directivity of the SEOS would be good right?
I would look for low 3rd harmonic distortion. The 8PS21 looks the best among those 8's. I like to see harmonic distortion better than -60db below fundamental across the pass band. This isn't a rigid requirment, but it usually separates the best from the merely good. There aren't as many good pro 8s as there are 6's it seems. Although I haven't seen it tested, the new B&C 8FW51 looks really good. It has a copper cap like the 8PS21. It has a bit more xmax and is 97db sensitive. I would still use the DNA-360 or 4550. I'm sure the BA is a good driver, but I generally suggest avoiding titanium diaphragms. I know it is treated but given the choice I'd still avoid titanium. Of course, you are going active DSP so you could buy all three and try them to see which one you prefer then sell the others. You wouldn't take much of a hit and swapping CDs is pretty easy.
Thanks! All kinds of stuff, www.conwaysound.com although everything there is really old... jeez I need to update that, most of those bands have whole new albums finished. Also have a pub deal producing mostly poppy stuff, and score corperate vids etc. Have been working on things with some members of One Republic inc Ryan Teddar but all of it is in the wind so far, also Barry Larkin's daughter (Big news coming soon from him...). I've been doing music full time for almost 15 years now (as a pianist and this) so I appreciate the variety. So looking at those charts I don't know if they are apples to apples but it looks like the 8ps21 maintains 60dB over the 3rd harm more so than the 6md38, right? Looks like ~120hz and up, which would be more or less perfect for this project. The 8FW21 looks good too, It seems unless it had much better disto, the 8ps21 will go a little lower in a sealed box... Something like this might be worth experimenting with: http://www.diyaudio.com/forums/multi-way/195870-el-cuerno.html any thoughts on how it would work with 2 mid drivers? Also yeah I feel the same way about the Ti, especially because I'll be listening to them 40+ hrs a week. Thanks again-
That's certainly a very good number, but it seems that distortion is usually given for 90 dB SPL or so. Any idea what it is at the 30 - 40 dB higher peak levels?
Hey Noah- Not to speak for anyone else but I'm guessing the presumption is that the one that is lower at 90dB will be proportionality lower at higher spls. I don't know if that is always the case so you make a good point. None the less if we are going by the data that is available that's about all there is to go from. So, hmm looking at the graphs for the SEOS's it appears the 18 is not as smooth as the 15 or the 12. The 12 really looks the best no? Any experience on that from users? That combined with the possibility of the cardiod woofer setup (which also looks pretty easy to build) has me thinking that going to even the seos 12 with maybe a pair of the new 5mnd38's or seos-15 with 6md38's and maybe a 15fw76 or similiar might make the most sense. Haha, right back to where you were trying to steer me coctostan (for good reasons I see). Aside from lowering IMD it also seems it would leave huge overlaps to work with where I might even be able to get away with all 1st order filters and possibly some notches for the cone breakups (and maybe an addl cap to protect the CD). hmmm....
The SEOS-18 would present some advantages with better vertical control being the primary difference. FR smoothness between the 12, 15 and 18 are basically a wash IMO. I believe you can the SEOS-15 in solid surface which is a good compromise on price while allowing for lower horizontal directivity control. The SEOS-15 or SEOS-18 with dual 8PS21s or 8FW51's would push the budget a bit more, but would be amazing performers. Using the 8s would increase headroom a tiny bit over the dual 6s. The differences between these configurations is going to be tiny and short of trying them back to back it would be very hard to determine a winner. Cardioid is a possibility, but it is not something I have actual experience with. There was a post on AVS about doing this with dual 8s and the SEOS-18: http://www.avsforum.com/t/1291022/hey-guys-we-need-a-little-rallying-here/6180_60#post_22698423 Getting controlled moderately narrow directivity down to 300-400hz would be pretty exceptional for your mastering. It would be hard to further minimize your room's influence and get a "purer" response. Cardioid is definitely something you can experiment with on test boxes. It will take some tweaking to get right. You will also need to measure outdoors to see what it is doing to directivity as you tweak the side output. You could build sealed to start and experiment with cardioid later. It looks like you have a nice business going. I think any of these monitor configurations will work well for you.