New forum member, new OB project

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
I have some OBjection to your magnet mount and that it constitutes an unnecessary "footprint" for the backward air flow.
And also that the mass of the construction is not contra directional to the cone movements.

I recently did a magnet mount of some TD15H woofers in an OB constellation: http://www.diyaudio.com/forums/subwoofers/213323-ob-elegance.html
Perhaps you can get some do's and don't's there.
 
So...I got a little creative over the weekend.

7504903686_8c26513750_z.jpg


It solves the problem of an overly large baffle and high mid and tweeter height. I'll be adding sound deadening panels behind on the ceiling and the walls to try and absorb some of the low freqs and bring the bottom end back up. But even without, I think I only lost a few (2-3) dB as opposed to having the on the floor. I will try and get some measurements done by Sunday night.

Enjoy and happy DIY :)

EDIT: Also - Happy 4th - Enjoy the fireworks!
 
It's been a long time since I've last posted here - lots of things going on. Almost none of which include this project. I have assembled the following baffle albeit without the compression driver (I've decided on the D220Ti). I am using the old Seas H1189 tweeter for now.

7867853994_a757095aee.jpg


I am also using the old 3-way crossover. I disconnected the highpass for the mid and un-attenuated the tweeter section. The x-over freq is around 1.8kHz. A little higher than was I want to end up using.

I took some gated measurements from ~1m and got the following:

7867829420_caef15f308_z.jpg


7867829704_97f349ba35_z.jpg


7867829002_e970f75fb1_z.jpg


The large peak from 500 to 800Hz is definitely noticeable! As it should - around 10db! Yikes! The tweeter is quite a few dB less efficient than the B&C mid, so its level is clearly lower. The 4kHz dip is a little odd - Probably a phase issue? Any ideas here? I can post up the crossover if needed.

Here's a response curve for the 21"ers at the listening position:

7867829276_7a0f3edc19_z.jpg


Not too shabby I'd say - especially when the full system is sampled:

7867829574_754822fec0_z.jpg


I do like my bass on the little heavier side so the bottom end I'm not going to focus on for a while. Also - it seems that the 5kHz dip is gone?

As for the rest - I'll have to find a way to get a notch filter put in for the midrange. I'm also hoping that with the addition of the D220, the tweeter level will be matched a lot better and hopefully not have the null at 4kHz.

Please remember that I'm shooting "in the dark" for the crossover as I'm just reusing my old one. I don't want to modify it too much as it will be reused in a 3-way cabinet later on.

Comments are welcome as always :)
 
More updates :)

The Seleniums came in today! Total surprise as, even according to FedEx, they weren't supposed to be here until tuesday. A welcome thing over a long weekend!

And so I've been working somewhat on these this afternoon, getting them mounted and taking measurements. I do like :D

First pictures of the new baffles - these will soon be moved further off the floor as they are a little bit low at the moment. The tweeter will also be moved a bit further forward to be better time aligned to the midrange.

7908967496_671b38abab_z.jpg


7908980730_4178dd2990_z.jpg


Here's a depiction of the crossover that I've adapted from my old 3-way (Notice that both drivers should be in-phase!):

7908998376_612349b024_z.jpg


Next is the nearfield measurement of the D220Ti:

7908968098_9b9b53333e_z.jpg


The crossover point for the D220 looks to be a bit higher than what it was for the H1189 - remember that I've done no actual crossover designing/building at this point.

I did a 1m gated response for the mid and tweeter (tweeter phase inverted):

7908968672_cdaf40a5be_z.jpg


I saw the big spike at about the tweeter's crossover point and proceeded to change the phase on the D220:

7908968540_88bff4ffd1_z.jpg


Much better :)

Here's a measurement of the listening position with both channels playing (just mids and tweeters):

7908968388_a3b0291049_z.jpg


What a pleasant surprise! Way flatter than I imagined it would be.

Here's a final with the 4 21" MCM woofers (for those of you just catching up, they're running with a 30Hz In-line lowpass before the amp).

7908968794_5f786ee23e_z.jpg


I can turn the gain down a bit to get a much flatter response in the bottom end, however I seem to prefer the extra low end.

I'm happy ... for now :D
 
Last edited:
Thanks!

The B&C came with an M5 threaded hole in the back and I just routered a relief for the D220. It's a snug fit for the D220, however I wanted some extra security.

The only problem that I can tell right now is that my imaging is a little low - when I'm feeling lazy and laying on the couch the image is perfectly centered (to my ears). When sitting up however the image is low and I seem to be able to tell the speakers apart. Thankfully the whole baffle/stand cost me only about $10 ($6 for the 4x4 and a few for the threaded rods). The rest I had laying around the garage from previous builds.

I'm thinking about tilting the whole thing a little and seeing how that comes out. Else I'll have to see how much higher I need to get the drivers - crude eye-balling is ~5 inches or so.

Additionally - the bass from the 21s seems rather well integrated without localization (or at least very very little). I don't know if it's because of the low frequency or because of the nature of OB. Maybe someone else can shed some light on the matter. Without the 21s, the mid/tweeter is seriously bass-less - much contributed by 1) the small baffle and 2) the nature of the woofer itself.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.