Open Baffle - Test Bed

[NWCgrad]

Copied from the Open Baffle sticky thread.

Building my first pair of open baffle speakers. For testing I am starting with the following:
1) MarkAudio CHP-70-P Gen 2 Natural
2) JBL Pro PRX700 horn (4" throat)
3) 24" x 48" x .75" plywood
4) JBL Pro 2123H 10" midrange
5) Eminence Delta-10A 10"
6) JBL Pro 2226H 15"
7) Pi Speakers H290C HF horn (1" throat)
8) B&C DE250 compression driver (will remove back for quasi-dipole)

Items 2, 4, 5, 6, 7 and 8 are leftovers from previous builds.

Have played around with Basta program over past few weeks, will see how models compare with reality.

I really like horns, my main home theater speakers have horn HF and Mid, crossed over to a JBL Pro 2242 18" driver for bass. Each speakers weighs around 250 lbs. The Auto-tech horns look really nice, lots of builds with them paired with Lowther drivers. Since no one in the US carries the horns I decided to use a spare JBL midhorn with an inexpensive full range driver.

Here it is so far....

 

[NWCgrad]

Made a few quick REW measurements, driver has been playing at low level since Monday afternoon.

This is without any EQ or XO, REW was set 50 Hz to 20 kHz. Looks pretty good from 200(ish) to 4000(ish).

 

[adason]

yes it does!

 

[NWCgrad]

I wonder if the driver is robust enough to run without a HPF. So far it meets what i am looking for, a single driver that can cover to 300-3000 Hz range.

I added a B&C DE250 compression driver on a Pi Speakers H290C waveguide above the midhorn last night. Using a single 7 mH capacitor is is flat from 2kHz to nearly 20kHz (will post measurements later). The DE250 is 10 dB hotter at 36 in on axis than the Mark Audio driver, using an L-pad I had in my toolbox I was able to level match the two. I need to reduce the driver overlap, I tried many cap values and could not find one that raised the knee of the curve above 2 kHz.

I have an unused Peavey VSX26 digital loudspeaker management system, provides XO and room equalization. I would like to run the mid driver direct from an amp, and only use the Peavey for the HF (4 kHz, BW-6 HPF) and LF (225 Hz, LR-24 LPF) to keep the purity of the wideband driver.

 

[NWCgrad]

I just purchased a MarkAudio Alpair 7P driver, need to start breaking it in and then run measurements. I am hoping it has greater HF extension than the CHP-70-P Gen 2 Natural. Based on native frequency response it should.

 

[NWCgrad]

Here is a rough comparison of the MarkAudio CHP-70-P Gen 2 Natural as measured on a JBL Midhorn via REW and the raw data from the driver spec sheet.

Looks like the HF drops off at 4 kHz vice 6 kHz of the driver data. I should measure at home without it mounted on the JBL Midhorn for better comparison, but I thought it interesting how well they matched.

Here is the data from a B&C DE250 driver on a Wayne Parham H290 waveguide, pretty good for just a single cap for anyone needing a good sounding HF unit from 1200 Hz on up.