Flemke, the DD auto setup is a good starting point that can be refined considerably using manual utilities. I believe the auto setup also requires 2.0 software.
Dgw7000, the Bag End ELF sub is intriguing & I hope to hear one someday. From what I read in the reviews, the design entails the unusual choice of a resonant frequency above the operating range of the sub. As a negative result, there is significant roll-off at low frequencies, requiring compensation from the amp that may limit headroom and increase distortion. But in return one gains the advantage of negligible phase shift throughout the sub's operating range. Sorry you don't care for servo controlled subs. The DD servo is variable and user-controlled and the servo is essential-- particularly with large-diameter, hi-mass cones-- to achieve the very low distortion measurement referenced by Flemke. As one reduces servo control on the DD, the bass gets warmer, looser, and less delineated--perhaps delivering more charge to the room, but short on the articulation and speed that I prefer in a high-quality 2CH system. As has been observed, most listeners (particularly in the showroom) tend to favorably perceive high distortion in the bass region as warmth and musicality. Very few systems offer the alternative of clean, extended bass, and this quality can be a little underwhelming at first. But once you get used to it you won't go back.
Dave |
The DD-15 has 1/2 of 1 percent of distortion.
The setup is very simple and anyone who owns one should press the auto button. It's that simple. |
The dd18 at the hifi house may not be set up right!!! and I bet over 60% of all people that own the dd18 do not have them set up correcty. That's just another thing that makes the infra sub 18 so great, it's easy to get great sound in any room. The servo chip and eq circuit rob the dd18 from fine detail of music, to much money went into the development of this. Servo's on subs in my view hurt instead of helping the sound. The signal is split apart so many times befor it gets to part of the sub that makes sound "the woofer".
The bagend sub extends to 8hz, even though you can't here it, it allows the sub with it's 400 watt class a/b amp enough headroom a full octave up to handle 16 hz pipe organ. Bagend uses ELF "extended low frequency'. It just works better by getting out of it's own way!!! |
As a DD-15 owner with a 2ch system, I'm with Flemke that the Vel was probably not set up correctly in the showroom. Few systems ever are, and this is particularly important with a sub. The DD has great setup utilities, but it still takes time & experimentation and a careful choice of connections & cabling to get it right. At this high level of performance, I'd bet that setup variables account for more variations in listening sessions than the choice of sub manufacturer.
As an extreme example, I was at a Magnolia the other day watching a couple listen to a demo of DSOTM through a basic REL sub. The setup was so bad that the sub was bloated horribly and way out-of-time with the main speakers to the point of laughter. But the customer & the salesman both seemed impressed, and the salesman just kept repeating "REL makes the best sub." Of course we are more discerning...
It's interesting how much passion gets into the sub debate regarding which hi-end piece to buy. I suspect that with fewer options to choose from (relative to the dizzying array of manufacturers building main speakers) the mind comfortably polarizes (ergo the tiresome REL vs. Velodyne debate). Much like in our presidential election, where the country polarizes with all its passions around a simple choice between two candidates at the top of our political system-- either of which will in fact probably end up business as usual.
Dave |
Greetings Dgw;
Your sure to stir up some heated debate in your assessment of the Bag Ends comparative performance, yet Ill consider your remarks valid based on your previous equipment, all high quality stuff, money not being the issue.
I must also confess not to care to be misleading in my comments about products to other posters looking in however, that being said, I concur that the Infra 18 is a sealed {not tuned} enclosure that is both time and phase coherent that delivers bass information that's very controlled, detailed with excellent timing and pitch, just does its job and gets out of the way of the important mid range while disappearing into the stage when no low bass information is there, totally integrated into my system yet never, ever, letting you know its position --geographically speaking.
This really is a reference product that should be on anyone's short list for those seeking a low bass frequency specialist sub that has seamless integration, effortless speed, extremely low frequency output, ie. thinking about how realistic the huge pipe organ music with sustained continuous low frequency shuddering/energy is utterly and effortlessly reproduced not to mention stand up acoustic bass like that from the Ray Brown trio or Michael Arnopold from Patricia Barbers catalogue etc.. that's done seemingly with nadda missing, not a note!
Just wanted to add in that last little comment about the sense of spaciousness this sub imparts to better recordings, its almost the same sort of dimensionality tube seekers enjoy in their playback, my thoughts as to whats causing this is perhaps this sub picks up reverberation trails or echoes in studios and venues that most other subs seem to miss, thus contributing one more subtle spatial cue that will greatly enhance the visual glimpse into recorded performances-- most surprising in addition to the terrific bass . " other writers have also commented on this effect in professional reviews"
In my unbiased opinion - YES - one of the very best.
Regards /// Tim W... |
Dgw7000
I would have to say the local hifi house did not have the Velodyne subs setup correctly. They should call tech. support and get them running the right way.
Tim |
Yes, I have heard both the dd 15 and 18 at my local hifi house, I feel the Velodyne is great for HT. I like the dd-18 much better than the dd-15, but for 2 channel the bagend with it's time alignment just becomes part of the music. The infra sub 18 blends so well with anying speaker, your speakers just open up and the bass is just there, so tight so controlled. When you turn off the bagend you say to yourself holly shit!!! This is what really good bass is all about, the music becomes very real. I would say the bagend is the most musical sub I have ever heard. The Vel. to me is one notey!!! Not Musical, but I love the way the Vel. looks!!! The sound is what really matters though!!
I also like 2 REL strada's, which at one point I had in my system. In the end the 18 inch bagend is the only way to go, if you can get it past your wife as your lugging in the room!!! |
Dgw7000
Did you hear the DD-15 or 18? What do mean when you say "does not compare"?
Tim |
Bagend is the only way to go, the bagend infra sub 18 is not a sub you look at and say that's a great looking sub. The velodyne is a looker, but in sound!! does not compare to bagend. When you put one or two in your system you will "here" why it is so special. Dave |
Good day folks; I also am running two Bag End Infrasubs using my Plinius M8 preamps dual rca outs at line level. My system goals were to augment a full range speaker with a seemless blending full range fast, tight response along with left to right drum kit recreation.I also use Plinius SA102s in xlr dual mono with Mirage OM6s with a claimed response of 18 htz +-3db, Im running lots of power across my front two channels and with a Plinius P8 on my center channel another 400 watts through the use of my transparent ultras and splitter.Now while some may claim overkill Ive found all this power is not corrupting anything in my listening,actually quite the opposite as my significant other listened for nearly four hours one evening when we played Fleetwood Macs "The Dance" among others and Mics use of the kickdrum was recreated through my Bagends wonderfully with my Mirages midrange reponse and lower dual eightinchers recreating the drum kit, the Bagends are so seemless that the only time you know there on is if you unplug them, then instantly ambient spatial cues just disapeer and the stage becomes noticably more less real, somehow they impart a realism to the recorded event that allow one to "see" into the recording.Also a great reproducer of pipe recordings as listening to Saint Saens Boston Symphony on Living Stereo SACDs the shudder of the organs albeit very subtle again imparts that reality to recordings that get lost with just about any single full range speaker. I also have a Mirage BPS400 for huge .1 effects and yes all subs working in 5.1 dolby and dialed in low prefering to use my ear although I have measuring devices that assist I prefer my own ears when dialing in system. So most of my need for my Bagends were simply to augment my Mirages full range response and help provide more subtle spatial cues; that surpisingly found when adding my second sub.Its my belief that theyre are many great and badly designed products out theyre and this is one of the best for musicality purposes, hence the BPS400 is likewise in the effects camp, choose wisely and enjoy. Regards Tim W. |
Porschecab: I have to agree that two subs do sound better than one if you can afford it and can place them. Two subs smooth the room response, that is why big line array speakers also provide the same benifit.
Otherwise your suggestion about one properly calibarted (aka Velodyne or other mic/eq sub) makes the most sense. But for Home Theater I would love to have two DD18's but my 2 channel takes priority and buying another Wilson Watch Dog is out of my budget right now.
Chris |
Truthseeker -
Funny comment:
"My gosh, I had to buy TWO gas masks for all the BS I smell in this thread. Talk of stereo bass, need for numerous 18" subs, small Velodynes as toys. The word NEWBIE is written all over this thread"
Kinda feel that is pointed directly at me since I am the one commenting on using a pair of DD-18s. You picked Velodyne why? You picked a DD-12 and then a DD-15, why?
You picked your main speakers, why? You picked you preamp, why? You picked you cables, why? You picked your transport, why? You picked your power conditioning, why?
I will give you the simple answer: Because you prefered it over another. This is no different than why I personally run a pair of DD-18s.
So many folks say bass is non-directional. Right. While this may be true below a certain point, 20hZ or whatever it is, a sub going from 60hZ (or whatever one has it crossed to) to 20hZ or less is directional and I personally can hear poiint out where it is coming from. Now, if I had a 30,000 sq ft auditorium, there is a much great chance of not being able to do so. Unfortunately, such a thing here in CA is about +$20M, albeit not much more than a home!
When properly set up and calibrated a pair will always sound better than a single.
Dan |
Oh yeah, I forgot to mention the some folks use two subs in order to attempt to smooth out some of the peaks and nulls in the listening environment. Takes lots of time, practice, and measuring equipment to accomplish this effectively. |
My gosh, I had to buy TWO gas masks for all the BS I smell in this thread. Talk of stereo bass, need for numerous 18" subs, small Velodynes as toys. The word NEWBIE is written all over this thread. For the umteenth time, it really boils down to just a VERY few things;
What size is your room?
How loud do you like to listen ON AVERAGE?
*if I asked most of you, you would have no clue (we're talking spl's here).
Is the sub capable of low distortion output?
That's all you need to know...period.
Will a larger DD-18 be able to play as well as a 15,12,10 etc. at lower levels? Duh: Of course. Will those other subs have the same low frequency extension as the 18"? Of course not.
As a general rule..according to Velodyne;
2 DD-10's will have slightly more output than a single DD-12, but also slightly less extension. (this extension thing can get a bit complex to explain)
2 DD-12's will have slightly more output than a single DD-15, but with less extension.
2 DD-15's will have slightly more output than a single DD-18, but with less extension.
As for the use of dual subs, there's really only one reason to do this, and that's usually because there's not enough output from a single. And actually, it almost always makes more sense to just get the next size up in subs. I had a DD-10 in my 3500 ft³ condo living room and it did just fine for both music AND movies. No, the low end did NOT have the impact that an 18" would, but damned well did just fine for living in a condo.
I recently moved up to a DD-12, and I couldn't wish nor ask for more. It produces MORE than enough ground shake and special effects for my needs...and I'm an experienced listener.
Like I said, it all depends on how loud you listen to your material. Most folks on these forums (and even folks from Velo) will convince you that you need massive amounts of subwoofing power, but once you get over the initial goofing around/testing it out/demos for your buddies, I guarantee you that you will very likely just "SET IT AND FORGET IT". Trust me, if you're making the most out of dual 18" subs in even a LARGE living room, you're probably doing damage to your hearing with your main speakers.
My buddy has had both a DD-15 and a DD-18 in his 4000 ft³ space and although he's kept the DD-18, he acknowledges that the DD-15 was MORE than enough for his room. He just happens to be the type of guy that needs to have the biggest, baddest, toy of ANY kind. Perhaps he's compensating for something else? :)
The smartest thing that any potential buyer can do is borrow any sub he's interested in and take it hope and play with it a little. Properly calibrate it to your mains and listen to all kinds of material, from music to HT. I'd be shocked if anybody in a 4000 ft³ space absolutely feels the need for 2 DD-18's, much less one. If I could tolerate the size, I know for a fact that a DD-15 would be the max I'd ever desire for MY room, but with my DD-12, I don't even feel the need for that. Then again, I don't listen to loud organ music.
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If you want to hear a musical sub, give a listen to the Bag End Infra-Sub 18. I've heard and owned many subs including NHT Sub Two[stereo pair] with four 10", and Vandersteen with three 8", B&K 15", A stereo pair of Onkyo THX from a $3000.00 speaker system[CRAP] and for 2 channel nothing comes close!!! Although its protection circuitry will shut it down if played loud for any length of time but IÂ’m talking 115 db of dense bass |
I am interested in getting DD12. DO you guys use the speaker level or the line level input? And if using line input, is there benefit in using the line output back to the amp? ( increase dynamics vs lost in trnasparency)
Thanks |
El -- OK, I'm in for your centre SW. Driven left+right into one.
I would raise the added drivers called a SW -- to two, open baffle. What do you say? |
Gregm...I'll see your two SW, and raise you one center SW. I also have SW drivers for the rears, but haven't got around to putting them in enclosures.
I think that every speaker system should be flat to near 20 Hz, and that usually means you need to add another driver, called a SW. |
Eldartford -- agreed. How 'bout two subs then, driven from line level:) |
No slouch,
I too listened to a DD-12 at a local dealer over the weekend, and while it did a credible job in a moderately large home theater room, it didn't provide the tactile shudder of an 18" sub. Like you, I'm going to go with the DD-18. Still thinking about 2 of them? I suppose you won't know until yours arrives. |
Gregm..."VERY difficult", perhaps, but to simulate a point source to the left or the right with a center speaker is downright impossible. I agree that the Velodyne 18 incher is a good product and will no doubt work well. |
Is it a non-contested fact that multiple 12" subwoofers could match or best a single 18" subwoofer in terms of quality of low bass? In theory you can do it. In practise it is VERY difficult to simulate a single point source (the 18") with many 12". You'll be happy with yr DD-18; it's a very good product. |
Thanks everyone for your comments.
I put in an order for a black DD-18 subwoofer. Originally I thought I wanted the maple, but I really liked the gloss finish on the black.
In total, I listened to the DD-12, DD-18, BagEnd Infra18, Rel Stadium III, B&W800 and 850. My impression was that an 18" subwoofer could be played well at low volume. I had never heard a home subwoofer before, and was amazed at what it added to movies and HT, hence I decided to get the biggest one I could. Although the Velodyne retail salesperson and various other people on this forum and elsewhere have assured me that the smaller 12" and 15" subwoofers should work about as well in smaller rooms (they said that room size should be my only consideration), I didn't have the chance to test this. In the small to mid-sized showrooms (250-400 sq feet?), and sitting at a close distance to the subwoofers, I found it hard to believe any number of 12" subwoofers could ever match an 18" subwoofer. The 12" ones didn't seem to have authoritative impact, and in fact I didn't really like the 'punchy' bass they put out- I see why someone might call them a toy, no offense intended to anybody. Is it a non-contested fact that multiple 12" subwoofers could match or best a single 18" subwoofer in terms of quality of low bass? It seemed so hard to believe in the store.
Also, a reviewer for a hifi magazine was in the store that afternoon, and I got to listen in for his review of the 1812 subwoofer for about 45 minutes of home theater, and I decided I wanted to get as close to what i heard there as possible
The DD-18 will arrive in about 2-3 weeks at my apartment, I'll try and post a follow-up around then. |
Sean...What are we looking for? I thought it was a variation of sensitivity (dB/volt or dB/watt) as a function of SPL, particularly evidence of a reduction at low SPL. That's what I looked for. |
El: I never said that i doubted your test results, so why would i bother trying to duplicate them? What i'm saying is that this is probably not the most appropriate manner to try and ascertain the type of information that we are looking for. Sean
> |
Sean..."the manner in which the tests were conducted may not be revealing enough". The test SPL values went down into the inaudible range. What would you like?
Again I say, go make some measurements. I can see that, like St Thomas, you won't believe until you see it for yourself. |
DC of any given amplitude will have a constant RMS value. AC does not, especially when using non-symmetrical waveforms like that of music.
DC of any given amplitude does not have a duty cycle. AC does not, especially when using non-symmetrical waveforms like that of music.
I didn't suggest that your test results were based upon false data. I said that the manner in which the tests were conducted may not be revealing enough to explain the criteria that i mentioned. Assuming that such data was all that one needed to formulate theories that were set in stone would be nothing less than incorrect and / or misleading to the general public. As i publicly stated, i appreciated the fact that you were willing to conduct such tests. Sean
> |
Sean...A loudspeaker driver is EXACTLY a linear version of a rotary PM DC motor, where force (torque) is proportional to applied voltage. The applied voltage is variable DC. What do you think would happen if you had a DC-coupled power amp (like my Kenwood LO7M) and applied a staircase voltage, 0.2, 0.4, 0.6, 0.8...1.0....etc? (The cone would move out in steps determined by the suspension elasticity).
The AC motor, induction or synchronous, develops low torque at low RPM basically because of inefficient
commutation. (A synchronous motor has zero torque when stopped, and requires either a mechanical spin, or auxillary windings to get it going. Sometimes, as with the motors used to spin gyro wheels of inertial instruments, a periodic overvoltage is applied to the motor so as to get it to "lock in" to synchronous opearation).
Your suggestion that my test hid the effect that you theorize is a cop out. Truth is my test would be INCAPABLE of hiding it. Do you suggest that I reported false data? Why don't you try it for yourself? |
El: How is it possible for the motor structure of a loudspeaker, which is fed a non-steady state AC based musical signal, which varies quite drastically in both amplitude and duration, to operate anything like a DC motor?
After thinking about the above question and coming to a logical conclusion, look at your own quote here: "Perhaps you are thinking of AC motors, which do not develop much torque at low rpm."
Perhaps i am. The fact that we are feeding AC into a magnetic motor structure could have something to do with my thinking that. The fact that you acknowledge that such a system doesn't develop a linear torque curve, and is "weaker" at lower drive levels, is exactly what i stated above.
Like i said, the testing that you performed may not have been specific enough to reveal these problems. Making comparisons to different motor designs and modes of operation, which an AC motor or voice coil is to a DC motor, just because it fits a specific set of test results, doesn't make it so. It just means that the tests performed weren't capable of revealing what is really going on. The fact that you already knew the answer pertaining to AC motor operation as demonstrated by the above quote, but adjusted your train of thought to support your later test results and twist the comparison around, is neither consistent or scientific. Sean
> |
Sgr,
I wish my room could accomodate 4 subs, but there's really only one workable corner. I could put 2 smaller subs under my front screen, with a 3rd in the back. Ideally I'd like to get by with one great sub if possible, especially since the reasons for replacing the horn sub are space considerations and room aesthetics.
What do you think about three Velodyne DD-12's -stereo for 2-ch listening and the trio for HT? I'm assuming they can be connected for audio and HT simultaneously like the REL? Would three 12" subs equate to two 15"?
I've read good reviews of the Revel B-15, although it came in middle of the pack in the recent Sterophile Guilde to HT review. I've not read much on the Sub 30 though. How would you compare the two?
I really like your listening room. I wish my wife would allow me to treat the ceiling the way you have. Lately I've been thinking about going with a TACT TCS that would provide digital equalization rather than treating the room. But I think that's more dreaming than reality. |
Kenl,
With that monster sub you own now, I'd want either two 15 inch subs or two 18 inch. I'm going with two Revel Sub 30s having heard one B-15 that sounded incredible. Everything I've read reinforces my belief that two subs are better than one, and if you go to Revels site and look at their white papers, 4 subs are the best, one in each corner of the room. This gives the smoothest response no set up headaches according to Harman Specialty Group testing. |
Thanks guys. If you click on my system and view the pic of my current horn sub, you'll have an idea of where I'm coming from. It works wonderfully, but at 42"x42"x22", it's a monster.
I had a 9' sofa sitting on top of it acting as a 22" riser for the second row of my HT. Out of sight it provided not only great bass, but acted as a huge butt-shaker. Now that it's out in the open, my wife says it has to go. Thus my looking at Velodyne and Aerial subs, and my quandary of whether to go with one 18" or two 12". |
Dialing in a pair of subs is quite tough, and I have not been able to figure it out quite yet. In some respects, using a single, dialed in correctly can be much more accurate than two, not so dialed in!
I run a pair of DD-18s and they seem to be pretty close to dialed. Not being a professional, I am sure there is alot of room (sorry for the pun) for correction. I will be trying to locate a JBL Synthesis professional to EQ my room with the SDEC, which should help a bit.
The DD-12 are incredible. I know several folks that run electrostats that use the DD-12. Slouch? Well, I suppose that depends on who/what you compare it to. The DD-15 and DD-18, for output levels and impact, sure. To a midfi levels of Paradigm, Sunfire (sorry guys, it doesn't compare, imo) and just about every B&W sub (I do like the older ASW-800) The DD-12 rips for 2 channel and HT.
Now, onto Aerial. I have owned / lived with Aerial SW-12 subs at least three times. Each time I used a pair as I have not felt a single can give me what the Velodyne subs can, so I ran them in pairs. The SW-12 is one of the best 3-4 subs I have had experience with. (Velo, Aerial, Rel, ATC, Earthquake (nice sleeeper here), Talon, and the others like Sunfire, Paradigm, Energy, HSU, M&K, etc)
My issue with the SW-12s are that in large passages (be it an organ or explosion) the excursion of the 11.7" driver is so much that the ports BLOW ME. On hot summer nights, it is a nice feeling, but the port shaffing noise and air does bother me. Now, at any other time, I love, love, love the Aerial. If they made an SW-15 or SW-18 I would be in as THE SUB!
One gets alot with the DD series subs. Ability to dial them in, they are incredibly quick, output levels unmatched, and their shape is much more appealing (though, in my case, 18's in any cabinet are imposing) than the older HGS series.
I am having Sound Anchors make the first Aerial SW-12 like stand for a DD-18 so they will have the platform in about 2-3 weeks. I will set the DD-18s on the stand and place a very heavy piece of custom black granite on the tops. This is the single largest improvement I have heard with subs. Placing something very heavy on top. Not sure why, but it has made a nice addition, appearance improved as well and when my cats use the top as a catapult, it doesn't ruin the finish (sm!).
Dan
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Just so you Know I run a Velodyne F1800X behind my couch in a HT setup and now I don't need bass shakers in the couch because it moves the couch plus it doesn't have to be quite as loud, you must crossover at 80hz or below becuase it is in the back of the room. So under my screen is now uncluttered! For movies go for the single 18", if it was music dual small subs but the Electronics will take care of the room problems. |
The guy from Velodyne is old school. He is a hoot to talk with. He rminds me of Tom Port from better records. I was also thinking about two DD-15's. For me it's just overkill. My DD-15 is set to 4. |
Kenl....I suppose you could go back and forth forever adjusting the two Subwoofers. The suggestion from the Velodyne guy seems reasonable.
I am glad that I don't have to decide between two 12 inch and one 18 inch. I guess I would go with the two 12 inch.
FWIW, my subwoofer system consists of three 15 inch and three 12 inch drivers, in huge enclosures embedded in the wall. |
Eldartford -
Your explanation of the set-up of dual subs makes sense. However, isn't there then a chance that by making a second adjustment to sub #1, it could change a resonance that sub #2 originally saw and compensated for, but is now not needed. It almost seems like chicken and egg to me. Am I missing something?
I agree with your opinion of 12" subs. IYHO, forgetting space considerations, am I right in assuming you would opt for one DD-18 over two DD-12's?
Thanks. |
Although I like the idea of large LF drivers, I do not think that the 12 inch Velodyne can be described as a "toy". If space or budget constraints must the recognized the 12 inch units are a good choice.
About the 3 step equalization process...The second SW may null out a room resonance that the first SW saw, and corrected. So in the end that correction by the first SW is not needed, and the second-time-around equalization gets it right. |
No slouch,
Thanks for your input. I'm assuming step #2 as was described by Velodyne makes gross adjustments to the 2nd sub, while step #3 fine-tunes the combined subs. Just my guess.
I'm surprised that a Velodyne rep would disparage their smaller subs by calling them toys. Aerial's sub is in the 12" category, and it's anything but a toy. Some think it may be the best under $8k sub.
I'm very much interested in your impression of the DD-18. Let us know your impressions. If possible, try and listen to the DD-12 & DD-15 if they are also available. I'd be curious as to how they compare.
Thanks. |
Kenl,
Both of your questions were addressed by the Velodyne rep with whom I spoke.
1) He said that equalization with 2 subs is a 'bit tricky'. First you need to play subwoofer A by itself and do the equalization for that sub alone, then you need to play subwoofer B by itself and do the equalization for that sub alone. Finally, you play both subwoofers, and do the equalization for sub A. I didn't quite understand the logic of the second step....
2) The velodyne rep said that 2 DD-15s are equal to 1 DD-18, and 4 DD-15s are equal to 2 DD-18s. He said that the DD-12 is a 'toy', which seemed to implyt that no combination of DD-12s would match even a DD-15.
I listened to the Bag End Infra 18 subwoofer today, and I am certain that the 18" inch subwoofer is suitable for low-volume playing without disturbing the neighbors. It seems to sound subtler than the 15" B&W I demoed, although it does seem a bit slow, as Porschecab mentioned (but its the first time I heard an 18" subwoofer outside of a club, so I'm not sure it's a fair perception). I will listen to the DD-18 tomorrow, and make a decision then.. |
I've followed this thread with great interest, as I'm now trying to decide on one Velo DD-18 or two DD-12's. My room houses 2 separate systems, 2-ch & HT. Due to furnishings and construction, I can place one DD-18 in the right rear corner, next to the 2nd row sofa; or 2 DD-12's in the front of the room flanking the center channel speaker under the front projection screen.
My question for those familiar with the Velodyne DD series is:
When adjusting the built-in equalization using 2 subs, how does the 2nd sub take the effects of the 1st sub into consideration? Is the entire system playing when these calculations are made, or just the subwoofer that's being equalized?
And now back to the original question. If 2 subs are better than one, specifically concerning the Velo DD series, would two DD-12's be as good as one DD-18 for both 2-ch & HT? I'm particularly concerned with HT, since I'm sure 2 DD-12's would be great stereo subs for 2-ch.
Thanks for your opinions and advice. |
Sean...A speaker (driver) is most like a PM DC motor. Except for static friction, (if any) which causes a "deadband" for plus/minus a small voltage, the torque constant (KT) of such a DC motor is completely constant over its useful range. We used a servo motor with more than 400 inch oz of torque capability to measure gimbal bearing friction of about two inch oz, and gimbal unbalance to an accuracy of better than a tenth of an inch oz. Perhaps you are thinking of AC motors, which do not develop much torque at low rpm. And, BTW, the DC motors in the PWM gimbal servos that I worked with "changed direction" (when commanded) at 300Hz...not exactly tweeters, but certainly comparable to woofers.
Apart from broadband sensitivity, frequency response might vary with SPL. I can do that test too! |
El: Thanks for taking the time to perform this second set of tests. I would only comment that a loudspeaker works much like an inductive electrical motor i.e. voltage is fed into a coil and the resultant fluctuations in magnetic field create motion of varying speeds.
Think about that aspect of operation and what is required to bring the motor up to a linear operating speed and you'll have a better idea of what happens to a speaker too. The fact that a speaker also has to deal with the mechanical / thermal losses of the suspension increases the variables involved and the linearity of operation. On top of that, motors typically don't change direction at a rapid rate of speed and / or change loading characteristics as signal is varied.
There's a lot going on here that may / may not show up on an SPL meter. Sean
> |
MORE DATA
Signal..SPL
..NONE...40 to 55 background noise
..-80....42
..-75....46
..-70....50
..-65....53
..-60....58
..-55....63
..-50....68
..-45....73
..-40....78
..-35....83
..-30....88
..-25....93
..-20....98
..-15....103
..-10....108
The signal was white noise, as before, but limited to frequencies below 400 Hz, and reproduced by my subwoofer system. (Easy to do. I just muted the HF and adjusted the X/O frequency up to 400 Hz). From prior experience I know that the warble tone would have rattled things. The mic was positioned about one foot from the 15 inch driver.
This time I set the signal level using the preamp volume control, and read the resulting SPL. When reading the SPL for the range below about 60 dB I took the lowest of rms indications over about 30 seconds, which corresponded to a lull in the traffic (background noise). For the higher SPL readings I took the average, as before.
Plot the data and you will see that there is almost no suggestion of decreased sensitivity at low SPL, which I attribute to the greater care that I took to minimize error due to background noise. And anyway, the SPL range where the data is not perfectly linear (for whatever reason) is so low as to be almost inaudible, so it wouldn't matter anyway. I am particularly happy to see no compression for high SPL, which would be a worse problem.
All of this is for my speakers :-). Maybe yours are different :-( |
I loved that Audio Control Richter Scale and the sweep it can do I use to use it to shake apartment rooms like 4-8 apartments away and no one could tell where the shaking was coming from.. College was great fun! |
If you are going to test a sub, try to get the meter as close as possible to try and eliminate room nodes. Otherwise, the linearity that you measured last time will be thrown out the window. The room itself will have a "knee in the curve" in terms of the excitability of nodes, etc... Sean
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Sean....I did not get to rerun the test last night when background noise was low. Maybe tonight. I am quite sure that the background noise is the reason that the plot becomes nonlinear at low level. By the way, the data looks too perfect over much of the range, and you might be suspicious, but that is exactly what I read from the instruments. It surprised me.
Per you suggestion I will run a test using only the dynamic cone subwoofer with a warble tone as a signal. This will cover the range 22.5 to 250. The warble will come from an Audio Control Richter Scale equalizer, and it is only as good as it is. One problem I anticipate here is that if I go to any loud SPL all the windows and doors are going to rattle, and screw up the measurements. |
El: Thanks for taking the time to not only perform the testing that you did, but for sharing the results with us. I look forward to your confirming both your earlier test results and my prior comments in your next post : ) Sean
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PS... Try a bandwidth limited signal for greater accuracy. The larger / heavier / less efficient the driver, the more apparent the variances in drive levels will be until the threshold or "knee" in the curve is reached. After that, the input / output ratio should remain relatively consistent until driver compression comes into play. As can be seen by your initial testing, this is exactly what took place and what i said would happen. |
SOME DATA
Signal......SPL
..-67.......50
..-52.......55
..-45.......60
..-40.......65
..-35.......70
..-30.......75
..-25.......80
..-20.......85
..-15.......90
Both the electrical signal and the SPL were measured, in units of dB, using my two Behringer DEQ2496. The SPL at 60 and 80 were crosschecked with my Radio Shack meter, and agreed within 1dB. The signal was white noise from a DVD player (used for channel balance). The measurements were RMS. Because this bounces around a bit, some estimation was necessary to get an average value. I set the SPL using the preamp volume control, and then read the associated electrical signal. The speaker measured was one MG1.6 backed up with a subwoofer, and the mic was about 4 feet from the MG1.6. I could not go higher than 90 dB because my preamp volume control maxed out using the DVD player signal. 90 dB RMS is pretty loud, and there is no indication of compression.
A plot of the data shows that at low volume below 60dB the SPL does not increase as steeply as it does over the rest of the range. However, I do not think that this reflects the kind of low SPL inefficiency which Sean suggests, because the background noise of the room ranges between 45 and 55 dB, as a function of traffic on the road outside. This background noise is pulling up the SPL data for the lowest two points. Late tonight, when background noise is low, I will make some more measurements. |
Sean...Mechanical losses are actually thermal in nature, like the electrical loss in the voice coil. In neither case is there any mechanism for a "threshold" to be overcome. But rather than debate, I will make some measurements. |
