Mark K's Speaker Pages

...when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the state of Science...Lord Kelvin


NC DIY AUDIO group budget collaboration
1/2010

 

 

Update 1

I've done some basic measurement and come up with a simple, round one crossover. It needs more baffle step compensation, and could be a bit smoother, although you can only go so far given flush mounting, minimal roundovers, and a very small baffle. See what you can come up with.

The raw curves look like--

The xover circuit and modeled response looks like

 

And the initial measured response is below. Note this is a 1 meter, slightly smoothed flex window (gives a more realistic low end) fairly short window measurement.

 

 

Introduction

Charlie Laub, who you can find over at www.ncdiyaudio.com  has been working on a group buy, budget buster. Below you'll find information on the cabinets, drivers and testing. This is currently a work in progress. So stay tuned for updates.

The boxes are very well made, with nice maple veneer. You have to work around the existing cutouts. One nice feature is that the cabinets have built in threads on the back, so you can easily stant or wall mount. (Yes, not uber audiophile, but makes wall mounting, HT use, etc very convenient!

 

You can find more information about this project on the PE board, at the following thread link--

http://techtalk.parts-express.com/showthread.php?t=214873

 

Driver selection

Woofer- Peerless 850443. Left over NHT stock, $10 a piece. It's being sold off by Jack Hidley. See the PE thread for details. Charlie chose these as they are a ridiculously low priced, high quality woofer. Last I checked, there were over 200 left to purchase. When they're gone, they are gone. Buy now if you're interested. Note the $80 minimum order. See the PE thread for other workarounds.

He brought two by and I went ahead and measured the impedance curves, as well as TS parameters

 

Both units match exceedingly well, both measured free air and in my 4.7 liter test box. Some minor impedance wiggles, but not until 2k, and really, the main one at 3k.

Below, you'll see my TS parameters.

 

They match up well with the small signal TS parameters listed by Jack Hidley found below

http://home.comcast.net/~jhidley/Klippel_reports/11-081-1_LSI_Detailed.htm

As well as Zaph's tests, found currently in his blog. Zaph wipes his blog periodically, so this link will likely vanish after a while.

I haven't modeled them yet. As you can see, since they do ~85 Hz F3 in my somewhat undersized test box (Q=0.8), you should be able to get ~80Hz sealed F3 with a Q~0.75. Ported box modeling to come. Or, do it yourself.

The nearfield curves are below. The Peerless is a bit smoother at 1-2k, but I suspect there is a little more irregularity around 1-2k where the cone is developing modes for the paper cone.

 

 Some limited nonlinear distortion numbers are below.

First up, a 5 tone nonlinear distortion graph. Well, the Peerless, in black, is marginally better than the RS150.

 

Next up, at 400 hz. It's a close call. The RS150 may be ahead, although there really isn't a statistical difference.  What you don't see is the RS150 had better 2,3 order. Again, kind of a dead heat.

 

 

Next up, 1k 3 tone. It's a little difficult to tell here as well. In the first graph, the Peerless is in black. Any excess red is RS150 excess distortion.

 

Since that only shows half the story, I've reversed the curves. Now the RS150 is in black. Any excess red is excess Peerless distortion.

 

So, to summarize the woofer performance, It's as good as the RS150, more or less. Maybe better performance below 100 hz, and marginally worse at 1k. Overall and excellent woofer for $10. Remember, this is really a $40 woofer except it's a buyout, so to speak.

 

 

The tweeter is the vifa DQ25SC16-04.  You can find more about this tweeter at Zaph's site, in his tweeter mismash.

This tweeter is a well known budget champ. I made fun of it over at HTguide, but I didn't really mean to. It's a winner from a distortion standpoint.

At 2k,

 

At 3k,

 

These numbers are excellent. They have moderate second order distortion and are excellent with higher order products. They rival tweeters that are 5-10 times the price. Now, they probably don't go much below 2k, and require a steeper filter. And, the FR curve is a little ragged. But they are excellent for the money.

 

For less than $50 in drivers, and hopefully under $150 total, you get a very, very low distortion small 2 way. 5 of these, sealed, would make an excellent modest spl HT system.

Next up, FR measurements.