BD Pipes driver questions

[Carlp]

First time speaker builder here, and I'm playing with a few designs (recently built a test-run Suzy Chang with the Pioneer A11EC80-02F 4.5"). I'm now working on BD Pipes with the same driver, but after getting a dry run completed and wiring it up with the Suzy Chang as the 2nd channel, I'm finding them (both) to be QUITE thin. Not bad mid and upper, but virtually no mid-bass and below. Not measured, just what I hear.

Now, I had trouble with the conversion from metric to inches and ended up with somewhat off measurements (1/2 inch less in depth and an inch or so shorter in height I think), and the bottom port is currently a 1 3/4 inch at about 4-5 inches long (something I had lying around). Thus far there's no damping inside and things aren't fully sealed up yet.

Other builders have reported good bass response so I'm wondering what kinds of things might cause this. The driver seems reasonably close to the Radio Shack 40-1197 that others have used to good effect (see specs below), but could that be the problem? The measurement problems above? Lack of damping and/or sealing? Other problems?

The Pioneer specs from http://www.partsexpress.com/pe/showd...er=290-010are:
Power handling: 20 watts RMS/30 watts max * Voice coil diameter: 1" * Impedance: 8 ohms * Frequency response: 70-15,000 Hz * Magnet weight: 9.3 oz. * Fs: 70 Hz * SPL: 90 dB 1W/1m * Vas: .31 cu. ft. * Xmax: 1.1mm * Qms: 1.40 * Qes: .47 * Qts: .35 *

Thanks a ton,
Carl

[Brisso57]

Originally posted by Carlp
<SNIP>
Now, I had trouble with the conversion from metric to inches and ended up with somewhat off measurements (1/2 inch less in depth and an inch or so shorter in height I think), and the bottom port is currently a 1 3/4 inch at about 4-5 inches long (something I had lying around). Thus far there's no damping inside and things aren't fully sealed up yet.

Other builders have reported good bass response so I'm wondering what kinds of things might cause this.

Thanks a ton,
Carl

Hi Carl,

Port size in a ported design is IMPORTANT.

The BD pipes call for a port of 2.7" diam and 5.15" length.
Fix this first.
Then make sure all other joints (and the speakers) are mounted air-tight.

Then listen again. It should be much improved.

cheers

Doug

[Carlp]

Will do, thanks Doug. I will say I now get the wide (and accurate) soundstage and some of the other benefits of single-driver/fullrange speakers I've read about. Man...

Carl

[nebojsa]

So, Carl how do they sound? Have you made the suggested adjustments?

[porkchop61]

Carl-
I just finished building a pair of the BD pipes, and are very happy with the performance. I put pictures in the gallery a few days ago, so they are near the end of the thread.

I changed my port inside diameter to 2" so I could use standard 2" white PVC pipe.
The new length calculations were done as shown below:

Using the formula L2 = L1*(D2^2/D1^2), and the following port dimensions:
L1=131mm (old port length)
D1=68mm (old port diameter)
D2=50.8mm (2") (new port diameter)

I get a new port length of 73.11mm (2.878")

This worked very well for me.
Good luck!

Glenn

[Carlp]

Haven't made adjustments yet (I have 2 young kids...) but will try to do it this weekend.

[Carlp]

OK, so now I've changed the port to a 2" (inner diameter) white PVC close to the 2.898" length Glenn recommends (as close as my primitive equipment would let me get...) and added damping (polyester fill from Mall Wart at <$2/lb), not stuffed tightly into the smaller half of the TL. Well, that has smoothed things out a tiny bit, and MAYBE boosted the low range a tad, but not much if at all.

I've also tried some other tests, and here's what I know. My commercial system includes a Marsh A200 amp (100w/c) and Vandersteen 1C speakers. That system, not surprisingly, can put out bass that I feel as much as hear (cetain songs that have accentuated bass - no sub needed here!). I've also been using a DIY El Cheapo 8w/c (+/-) push-pull driving Wharfdale Emerald 93C speakers, and that generates much less volume and considerably less bass than the other system, but I can still feel the bass on the same songs, just not as prominent.

Now, I'm not a big bass fan, but what I notice is that both amps with their respective speakers sound nicely full (good balance, full low end, not overbearing mids and highs, etc. etc.). But when I plug in the BD Pipes/Suzy Chang combo, I get nice mid and high end, but still almost nothing on the low end. I tried them on the Marsh and got much fuller overall sound and a hint of bass, but again, a bit anemic overall.

Next I will try sealing the cabinets better and maybe a bigger cross-section port (thanks Glenn for the other post on the port size calculator). But again, I wonder if the driver could be at fault at all. Also, while I stuffed damping in, I haven't yet added felt or other damping to the walls per others' builds.

Or am I just missing the boat here? Is this what I get with such a small fullrange driver? Wish I could hear others' builds.

Carl

[Brisso57]

Hi Carl,

1. Are both L and R equally low on bass?
2. Do you have the Pipes sitting on their natural base (plinth)? or do you have them sitting atop something else. (They are designed to be floorstanders. If you have them raised, you will get less bass.)
3. Do you have L and R in the same phase? Are the speakers' internal connections in consistent phase? Out of phase connections, either internally, or between L and R will cause problems. Worth double-checking.

cheers

Doug

[Carlp]

Thanks again, Doug. I thought about phase, but after I last had them open so didn't check that. I'll try to do that tomorrow. Worth a try anyway.

[Carlp]

Oh, and L and R channels are both equally low. But remember one is BD Pipes, and one is Suzy Chang (in 1/2 ugly old plywood as a prototype build - my first speaker ever!). More soon I hope on the phase question.