2-way MT: SB Acoustics SB17NRXC35-8 and Vifa DQ25SC16-04 (Poor Man's High End)

[jkim]

http://techtalk.parts-express.com/attachment.php?attachmentid=9024


Design Goals

Can a poor man own a pair of high-end monitor speakers? Yes, if he can spend $220 on drivers and crossover parts. I'll call this design "Poor Man's High-End Monitor." This design uses relatively inexpensive drive units but will not compromise performance. This is possible thanks to two low-cost, high-performance drivers Zaph recently tested: the SB Acoustics SB17NRXC35-8 and the Vifa DQ25SC16-04. I believe this system's distortion performance is nearly as good as some other, presumably, high-end 2-way designs that use more expensive drive units.


Crossover

http://techtalk.parts-express.com/attachment.php?attachmentid=9019
LR4 crossover at 1.9 kHz


You can order drive units from Madisound or Meniscus Audio. As for the crossover parts, I recommend ordering from Erse Audio (www.erseaudio.com). Their crossover components are of higher quality at lower prices than other retailers'. You'll save money for what you get even with shipping cost added. A BOM is attached to this post below.


http://techtalk.parts-express.com/attachment.php?attachmentid=9020
Predicted system response and individual driver rolloffs


Plots of filter transfer functions and system impedance curve are also attached below.


Enclosure

Net internal volume:
For a vented option, 21 to 25 liters with 34 to 38 Hz port tuning.
Use 2" ID port tube cut to total 5.5" to 7.5". Enclosure can be either front- or rear-ported.

For a sealed option, 12 to 15 liters. This speaker in a sealed enclosure of a volume on a larger side (14 to 15 liters) may provide adequate bass in a small room, but a subwoofer or two will be needed for full range reproduction in a larger room.

Baffle size:
8.5" to 9" wide. Baffle height does not matter though it will somewhat affect midrange tonal balance.

Driver layout on baffle:
Tweeter's center is 3" from the baffle's top edge with no horizontal offset.
Midwoofer's center is 4-7/8" (4.88") below the tweeter's center, which means 7-7/8" (7.88") below the baffle top.
Drivers should be mounted flush with the baffle in recessed cutouts.


Options

Experiment with tweeter padding resistor values (see the schematic for a suggested range).


Listening Impressions

See a builder's review here (http://techtalk.parts-express.com/showthread.php?t=214434).
Also find a couple of short listening impressions from builders of a preliminary version in this (http://techtalk.parts-express.com/showthread.php?t=207805) thread.

http://techtalk.parts-express.com/attachment.php?attachmentid=9025 http://techtalk.parts-express.com/attachment.php?attachmentid=9026
http://techtalk.parts-express.com/attachment.php?attachmentid=9094

[jkim]

:)

[robwest]

Can't go wrong with blue! Man, that's some x-o!

[hectorloshuk]

is it possible to use a 15 silver iris with the tweeter as is and then use a 15" silver iris without the tweeter for more bass in the same speaker. I would assume you would need to make the crossover a 3way. The reason I am asking is I like the SIs but it would be nice to have just a little more bass without adding subamps.

[gr43023]

Thanks very much for sharing this design with us.

Is there any reason why these drivers and crossover wouldn't work in a transmission line design? I've run the woofer specs through a couple of online calculators, and they suggest a folded line in a box about 44 inches high to go with an internal width of 7.5 inches.

My expertise runs to woodworking, not electronics, but my thinking is that the crossover deals mostly with the upper frequency range of the woofer and therefore doesn't 'care' whether the bottom end is managed with a sealed, ported, or other cabinet configuration.

[robertclark]

Paul K. calculated out a MLTL for the SB17 in an earlier post. I was going to attempt it myself for Iowa but I don't know if I'll have the time.

[Ray]

I really like your design, and would like to reproduce your speakers, but I have a couple of questions.

Your posted volume is about .75 to .85 ft^3, Sb-Acoustics recommends .6 ft^3 for this speaker, whats the reasoning behind the larger volume? Or is this the volume with the speaker and port volumes?

What are the dimensions of the speaker you built?

Thanks
Ray

[jkim]

The larger volume was calculated using Zaph's T/S param measurements. Normally, a DIYer's measurements of actual production samples are more reliable than the manufacturer's (often times with prototype samples).

Jay

[Mayhem13]

Nice Jay......another 2way that blows value out of the ballpark!:D

[Taterworks]

I've said it before - I think veneered finishes are passe unless they're especially exotic, and the most cost-effective and visually appealing finish option is a well-executed painted finish. Yours is looking especially nice.

[johnnyrichards]

That is a nice design, and I have to agree with Roy - painted finishes are the cats meow :)

I am buying almost exclusively from Erse Audio now. In fact, a couple months ago I bought a large number of the cheap Mylar caps for prototyping. They don't sound too terrible, either. Then I buy the Pulse-X for final build.

[lunchmoney]

I made the blue ones.

Here's the build thread:

http://techtalk.parts-express.com/showthread.php?t=212718