DIY Steel Pipe/Cable Stands (PICS!)

The DC Gold Drivers are great! I was measuring them and at a volume of 'loud' (I don't have a db meter to calibrate actual spl) they had a peak distortion of ~1% (in the 8khz+ region), then after some EQ (gonna do a post about that sometime soon) the distortion had fallen to under 0.5%! The distortion level is therefore under -40 db: pretty good considering the speakers are steel tanks! They are 'beamy', considering they are full-range speakers (can't beat physics) however I tend to have one primary 'sweet spot', also, wall reflections are less of an issue when you aren't sending as much sound towards the walls! I also intend to post some measurements made at varying degrees off axis so people can get an idea of the overall frequency response.

On the DC Gold speakers though, it is my intuition that the smaller diameter speaker transducers (N5R) would do better without any equalization, I think the N7R is pushing the limits of cone breakup/dampening when shooting for a response to 20khz. With a good EQ though (I am using Dolby Lake via PLM10000Q amp) they sound amazing - granted, I wouldn't setup any serious system without EQ anyways...

Thanks for the suggestion about the rubber, the cables are coated with vinyl though - and the finish on the speakers is line-x bedliner, so I am more worried about the vinyl getting messed up I was considering the rubber in order to decouple the speaker enclosures from the steel pipe assembly (to prevent ringing) however from the measurements I made testing the distortion levels, I did not find any ringing I could attribute to the pipes... Another idea was to stuff the pipes with rockwool, which is a similar approach to what I did with the speakers.

I remember some of you posts from the original build. Did you use some sort of Dynamat or other damping layer inside the steel pipe? Any stuffing inside at all? I'd use some Bonded Logic if you can find it or other similar material. It is the most effective material for absorbing the rearward radiation of the driver in the enclosure. I use it in all my builds and we also use it extensively in the acoustical treatments at the studio I work for.

I've been curious about the DC Golds for several years, not used as a true full-range drive, but as a wide-range mid. Used from say 150Hz to maybe 3 or 4KHz. I tested out so many drivers before my own project, that I had no more time or patience to order a set of N7Rs. Then I found the BG Neo10 for DIY sale finally and that was the choice. I'm still curious....

I'd be interest to see some frequecy plots. Without your EQ, just the native response of the driver. Wow, you got one of the those killer amp/LAke DSP amps? That's pimp! I saw some channel units on a refurb sale last year and really wanted them, but even on sale it was BIG $$$$!

Thanks again.

Greg

I used 3M undercoating (for underneath a vehicle, basically a rubberized spray coating) on the interior of the speakers, then I put rockwool around the diameter of the inside, however I "packed" it in there, which I believe had the largest effect on dampening any vibrations though the line-x also helps too - I will have to record 'knocking' on the tanks to demonstrate their 'deadness'. I broke my phantom power supply last night, i was trying to calibrate my microphone with an electric spark, and to get the noise floor quieter (6db/oct rolloff from spark sound) I tried hooking it to a battery, it has an 18vac input... it didn't work I should have a new phantom supply in a few days so I will make a recording and do more measurements then.

I did not use anything to dampen any resonances of the pipe... its just the pipe Since the speaker transducers are isolated from the speaker enclosures via sorbothane the already acostically dead enclosures are further isolated from any energy produced by the transducers. THEN, the vinyl-steel cables also seem to not be particularly conductive acoustically, then also, since its 3/4" pipe, thats quite a bit of mass - my point: I have found that any resonances/ringing from the pipe is insignificant. I intend on doing some measurements eventually, and since I like to perfect things, may end up stuffing the pipes with rockwool.

The N7r's should be good to 3-4k, if you can bi-tri amp your system and use a processor that would be optimal of course since you could EQ them a bit and achieve a pretty clean 8k

The amp is awesome. See their site (labgruppen.com) for more info; I got it off ebay, I was very lucky to find it at the price I got it for, they definitely are expensive, however, my setup consists of computer -> spdif cable to amp ->amp ->sub+speakers! so in a sense, you don't have to buy two amps (speakers and sub amp) and also the dsp processing is also included, so yes, expensive, but it really takes care of all but the source and the speakers [transducers], I have the 4 channel model of course.

You are in luck, a few days ago (the 21st) I did some EQ'ing and I have a pre-eq and post-eq measurement saved! The measurement is for the right channel (left and sub muted), on axis, ~6" from the acoustic center of the transducer (I made a 'jig' to consistently position the mic too, I will have to put pics up of that). The EQ'ed measurements are actually *measured* results, not predicted by REW. I was not finished eq'ing... so understand there is some variation in the high frequencies in the eq'ed measurement.

How are you liking the Neo10's I saw those (exist) after I built the N7r's, I want to mess around with planar speakers at some point here

Graphs! - the x-over was set to 48db/oct lin-phase @95 hz I believe... I think I changed the x-over to 62.5 hz for the post-eq stuff
Purple is pre-eq: blue is post-eq <- this hyperlink will take you to the picasa web album of the graphs so you can see full-size

Wow, good info. Thx! I've never seen a weird plateau like that at 500Hz. Distortion tracks all of those peaks perfectly. I would personally bring down the entire range from 2.5KHz - 15KHz by a few more dB. That whole area is too elevated for my tastes. Were these measurements taken in the tube?

I see that harmonic goes down nicely once you EQ out the peaks, but the waterfall looks like there is a lot of overhang up there above 8KHz. Hard to tell though with the scaling on the waterfall plot. Definately usable to 3-4KHz like you said once that plateau it taken down. I only do active with DSP now for state of the art systems. Passive is junk in comparison.

Sounds like you made a great effort to dampen the steel tube both inside and out. Good job.

You need a pair of my subs to match the aesthetic you've got going now!

Greg

I am not sure the cause of the 500hz distortion, the N7R speakers I have were 'rebuilt' after David Chaffey (owner of company) made some changes on the voice coil former, and presumably a few other things: the 500 hz thing was present in the other older measurements too... maybe it has something to do with the steel container OR the way things are mounted with the sorbothane-rear mounting/decoupling system? As I mentioned, the speakers were not done being EQ'ed the blue was with SOME eq applied, but actually measured. The measurements were in front of the speaker (in the manner shown in one of the pictures I first posted).

I am pretty sure the overhang above 8k is due to things not being EQ'ed, once things are 100% where I want them at, I will do a post with before-after measurements. I have everything scaled so there is a 60db range shown from 20-20khz.

You said "I see that harmonic goes down nicely once you EQ out the peaks" - this is a good thing I take it? (wondering the implications of this being the case, if you have any explanations I would love to learn more)

Nice sub! is that sonotube or PVC? I intend on EVENTUALLY (gotta save $$) building 2 TC LMS Ultra 5400 (one per channel, possibly set underneath ech speaker) subwoofers, again, in steel tanks coated with line-x

EDIT/addition: looking at it, I am PRETTY sure that the stuff on the waterfall from 8k+ is due to the noise floor of the recording setup, some sort of ringing which is unrelated to the sound in the room: I am in the process of improving my A/DC setup so shortly I should be able to confirm that being the case If you notice the 60hz hum in the waterfall, it appears to be 'of the same nature' as the artifact in the 8k+ region