, 05-27-2011 at 04:37 PM (5056 Views)
After a few months of listening, tweaking and evaluating the original Apaches design I began to notice many things I didn't care for. The bass was very bloated which I'm sure had to do with the room they were in. Something about the lower mid bass was prevalent and they had a sweet spot about the size of a dime. The mid bass issue was likely due to bandpass gain around 200-300 Hz and as the drivers broke in more and more it became much more obvious. The sweet spot issue was probably due to the tweeters not being offset and sharp edges on the baffles. Bottom line was, my initial impressions were due to the "OMGitsanewprojectanditmustsoundgreat!!" theory.
Anywho...I have decided to scrap the vast majority of that project. Vast majority being everything but the D8.8+ woofers I had. I had to wait 6 months for them and they are just too darn nice I couldn't part with them. I decided to go with a mid bass I hadn't used, the HiVi D5G, but something that is similar to its other siblings using the the Kevlar cone that I love the sound of. Due to the limited upper end of this driver I had to use a stout tweeter that would work well with a low crossover point, so I chose the well regarded Usher 9950. I will update again when I proceed with measurements.
Cabinet construction will be similar to the originals, only this time they will be just under 9" wide from top to bottom and everything will be sealed. there will be separate mid-bass/tweeter cabinets as before but the bottom enclosures will house the side fired D8.8+ woofers and will be self powered each with an SA100. As of now the cabinets are in the finishing phase and you can see them in raw form here. This is the sketchup version with the bracing shown, actual bracing resembles this perfectly.
These also have a 1-1/8" round over on the front edges and offset tweeters allowing the smoothest possible response. A targeted crossover point of ~1,800 Hz should allow a smooth transition and make the center to center spacing less of a problem. I should be getting holes cut in the baffles this evening which means I can get measurements by the end of the week.
Cabs are just about to the staining phase. I need to put veneer on the backs of both bottom enclosures, and the back and top of one of the upper enclosures. This shouldn't take more than an hour. All holes are cut and I should be able to get some listening impressions in tomorrow. The crossover I will voice first will be third order electrical on both at 1,800 Hz. After measuring in the lab, the woofers play clean to 2k and drop like a rock. You can hear 2k, but not 2,100. A simple zobel on the woofer is needed in the modeling, we will see what changes will be made after listening for a few days. The tweeter is also third order electrical and needs a simple L-pad to bring it down to the woofer level. Both work out to be third order butterworth acoustic targets. The phase is centered right at the crossover frequency and the reverse null is 30 dB down. Impedance doesn't drop below 5 ohms and everything seems to be within +/- 2 dB of reference. I will update in a week or so. I'm not soldering these together until I KNOW I wont make changes. Can't wait to hear these babies!
Finally got them home and hooked up for the first listening session. I listened to a large assortment of music for about 6 straight hours. The first thing I noticed was the amount of crisp bass provided by the D8.8+ woofers. I new room gain would help my situation but these actually gave me goose bumps when I heard them the first time. They modeled with a fairly high F3 of about 66 Hz in the provided enclosure, but in room they easily hit 30Hz with nice impact and authority. A huge improvement from the last ported version. I made probably 10 tweaks on the SA100 amps throughout the evening, I'm sure this will continue for another few days.
The sound stage is huge, these just disappear in the room. I remember somebody once saying how certain speakers didn't do anything for him, they just sounded like speakers playing music. These opened my eyes to what he meant. There seemed to be just a slight bit of excess sibilance but nothing that was fatiguing, I thought a dB or so of additional tweeter attenuation would do the trick. I was going to pick up a few resistors today to play around with this, and when I loaded everything into PCD with the tested values I noticed I made a huge mistake when I wired everything up last night. I accidentally put the 25 uF cap first in line with the tweeter, followed by the 9.2 uF This would explain the ssssibilance I was getting, it also totally screwed my phase. Additional padding may not be needed. I will swap these as soon as I get home and listen some more, hopefully things will only improve, I really don't want to lose that sound stage. I can't believe now good these sounded even with those caps swapped, and I also can't believe I made the mistake in the first place. Of course, now I can't wait to get home and this day is only going to drag on longer now!! I will update tomorrow after another listening session.
Wow. After being very anxious to get home and fix my stupidity I got another couple hours of listening in. I still need to pad the tweeters just a touch, but now they sing better than ever. No harshness at any frequency and the sound stage grew even bigger. I think I finally built something that I can be proud of and look forward to hearing for a long time. Time will tell of course. I will update again tomorrow after a padding tweak.
Todays post is to prove how valuable voicing sessions really are, and why my last project failed. After tweaking for a few days and not really making any progress (backward if any) I decided to pull out the Omnimic and see where I was. I could tell I was missing a lot of upper midbass but couldn't tell where, and none of my PCD sims fixed anything. My in room response was a mess which I expected so I decided to measure individual drivers in room. I re simmed everything using these measurements, I was able to eliminate the zobel on the D5's and surprisingly the L-Pad on the tweeters to achieve a flat response with the exception of a slight 2-3 dB dip due to baffle diffraction on the tweeter between 2-4kHz. I also modified the plate amplifiers and removed the high-pass output so now it is a simple pass through which really helped with blending the woofers together.
A slight ear infection in my left ear came a great time so now certain frequencies are very shrill which makes voicing a pain. Hopefully I will get over this soon so I can finalize these things and start staining.
They're done!! Finally almost over the ear infection, after having it for so long I learned what to ignor in my left ear. Ended up only needing seven components in each crossover, second order on the woofer, third on the tweeter with a simple L-pad. The system measures flat in room but sims a little off. I suppose this is to be expected. I must say, they certainly look better than the originals. When it comes to sound, only one thing describes it: "Three Dimensional". I've never heard speakers dissappear like this. No big fan fair this time, everyone thinks their newest speakers are the best sounding speakers they ever heard so take that and run with it.
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