[danvprod]

Hey All --

I've been refining my OB setup since last I posted about working with the WB Betsy (http://www.audiocircle.com/index.php?topic=118443.0). I've since made some changes in my system, namely:

• I've keep the Eminence Alpha15a in an H-Frame powered by a Rotel RB1050 70w/channel SS amp.
• On top of the H-Frames, I've mounted a U-frame baffle with the new Mark Audio Alpair 10.3
• Finished the speakers flat black and attached the U-frame with the full-range to the H-Frames with some stainless brackets from Home Depot.
• Added rubber washers under the stainless brackets for a little isolation dampening between the woofers and full-ranges.
• MA Alpair 10.3s have been broken in at low levels for about 100 hours or so.
• Added a Decware tube preamp to my system, as well as a VLPS II phono preamp. So signal flow is: Sony TTS 3000a Turntable -> Musical Fidelity VLPS II ->Decware preamp -> MiniDSP.
• Amplification is Rotel 1050b to the pair of H-frames and a pair of 300b 9 watt mono blocks to the full range drivers.

I'm having a bit of a challenge to get these to sound exactly right. I currently have the crossovers set in the MiniDSP to 12 dB/Octave LR asymmetrical rolling the h-frames off at 100 Hz and the MAs at 200 Hz. Bass is a bit boomy right now, just does not feel very tight.

I need to make proper measurements of the setup and see what is going on. I may have time to do that this evening. I'd like to be able to set the preamp trims (as the Decware has separate L and R trims) so that a pink noise signal going into the MiniDSP is at the same level.

I'd also like to do a proper time alignment with the two drivers. I need to experiment with the loopback functionality in HolmImpulse or REW. My plan is to turn the crossovers off, run a 500 Hz - 1000 Hz sweep with a 2ms delay on the MA driver, and see how far the peaks are off of each other to set the time alignment.

I need help with a good strategy to set the crossover points and any equalization in the MiniDSP. I know I may need to equalize the dipole peak, dip and rolloff, and maybe do some work on the LF build-up (which is more than likely room-born). Does anyone have any suggestions about where to do the measurements? Should I do a 1m measurement on one of the speakers to adjust the equalization with a gated measurement?

Any help here would be appreciated. I also found this speaker design -- http://www.enjoythemusic.com/magazine/equipment/0806/bastanis_prometheus_mkII.htm I really like the option of maybe combining an active plate-amp driver sealed box subwoofer with a thin baffle. The MA 10.3 and a Ribbon tweeter may be a real good arrangement in something like this. Just thinking out loud.

Anyways here are some pics of my setup. Open to comments and suggestions. Measurements to come/

[danvprod]

Here are some measurement. Basic workflow was to first feed a 1 kHz tone into my pre and then match the level coming into the miniDSP (as the pre has trim pots on the back), while at the same time not clipping the input, but having enough gain range. I didn't get a chance to crank everything tonight, but I think the range is OK.

Here are some measured results with the woofer alone, full-range alone and combined. I have the woofer rolling off at 100 Hz, and the full-range rolling off at 225 Hz. Both LR12. I notched out a few of the bass issues, added a shelving bass filter to the full-range to counter the dipole roll-off and also notched down the dipole peak.

These were taken from the right speaker at 1m with the mic positioned halfway between the woofer and full-range.

[danvprod]

Much better measurement technique tonight. Found an excellent article that told me I was doing my measurements all wrong.  Good read: http://www.brentbutterworth.com/PDFs/Speaker-Measurements-101.pdf.

Measurements were taken around the listening position, at ear level. 8 measurement positions were used in a 4' x 4' grid around my listening position. Then 1/6 octave smoothing was applied to get a general picture about what was going on.

I used REW to notch out some of the worst offending peaks, but I def. have some modal behavior going around at 50, 100 and 150 Hz. I reduced the level of the subs another 4 dB to balance out the full-range and lowered the cross over of the H-frames to 80 Hz.  I am pretty happy with the way that these are measuring now.

[matevana]

It may be somewhat distorted in the pics, but based on your post it appears that the proportions of the listening triangle may be working against you. Before you do anything else (since it's an easy and free tweak) I strongly suggest increasing the distance between the left & right speaker so it creates more of an equilateral  triangle with your listening position. If this is impractical due to space or aesthetics, you can try swapping the L&R speakers so the HF driver is offset to the outside of the baffle. This will increase the perceived distance between speakers due to the directionality of the HF driver and should help to improve things over a wider listening area.

In mirror imaged pairs, I too tend to start with the HF driver toward the inside, but there is really no right or wrong answer here... whatever works best in your environment.  In my latest build the difference was measurable.     

[danvprod]

Thank you, @matevana! I tried that, and it def. has helped the imaging quite a bit! I also changed the jumper on my MiniDSP to the 2v setting, as my Decware is putting out from 2-4v depending on the volume knob (and up to 6v with the preamp trims cranked all the way!)

I'll need to take another aggregate measurement with the tweeter 'out' vs. 'in'. This is the best the system has sound yet! Still more to do, though.

[danvprod]

The H-Frame Alpha 15a open baffles are so versatile. I've been playing around with this setup with a pair of Kef C55s I picked up for ~ $50. Running the H-Frames up to 125 Hz and the Kef C55s are picking up after that. These sound really great. Much different sound quality and presence vs. the Alpair 10.3s.

The H-Frames add so much to these bookshelf speakers. IMO, this KEF + Alpha 15a system would embarrass much more expensive speaker systems. It's kind of cool

[Poultrygeist]

I've used box speakers with H-frames and liked the results.