First attempt at DIY - small OB's

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The urge finally overcame me. I've been lurking around here for over a year and reading lots of amazing things about the projects that others have developed.

I wanted to start small. After seeing the Parts Express sale on Pioneer BOFU's and reading some positive threads about them, I figured what the heck. P.E. did a heck of job -- ordered on Tuesday and received them on Thursday. I also ordered a pair of Goldwood 1034's to fill in the low end and a small Dayton amp (APA150) to drive the Goldwoods. Keeping with the theme of starting small, I got a 2' x 2' x 3/4" piece of oak ply at Lowe's (wanted birch, but the local stock looked pretty shabby.

My woodworking skills suck, but I cut the baffles 12" x 24" with a 6" radiu round over at the top (and used the cut off corners as feet). The drivers are mounted from the back and sunk in 3/8".

So far, I'm amazed with the sound. I haven't measured anything yet and am playing with the crossover freq. Right now, the low pass on the 10"ers is at 150 and the high pass on the BOFU's is at 200 hz.

Either I don't know how to post pictures or am not allowed to on my first post. I'll try again.

Many thanks for inspiration from Godzilla, Gainphile, Stigerik, MJK, and many others here, and my friend Larry J. at work (who is never too busy to talk speakers and music).

Just a quick update.

With a few hours on the speakers now, I was trying some crude in-room measurements with a Radio Shack sound level meter and some sine wave test tones. As expected given the factory spec.'s on the BOFU's and the narrow baffle width, they run about 4-6 db high around 1kHz. They seem to hold pretty level from 450 down to 50 Hz (keep in mind that this is with spot checks at various frequencies - not continuous sweeps) and drop off significantly (~10 db by 40 Hz).

They have a nice, open sound although there is some of the "cupped hands" characteristic on some vocals that others have mentioned about these Pioneers. Mostly female voices and it seems to vary from barely noticable to prominant depending on the recording. Maybe I'll try removing the dust caps in the future, but right now I'm just enjoying the overall sound.

The Goldwoods seem to do a nice job of filling in the bass. Strings, woodwinds, and pianos sound very realistic. Electric guitars too. Mostly I listen to blues based stuff, singer / songwriter, some jazz, some classical.

That's it for now. More to follow.
Welcome to the forums.

Good to hear that you're enjoying your speakers.
A note on removing the dustcap - you must not rush. At all. If you're in any sort of rush, you're more likely to put the craft knife through the cone (nearly put one through my little speakers, one emerged grazed... - I tried to get it done before school). Apart from that, take it slow. Using a gentle, saw-like motion seems to work okay. Scalpels (with fresh blades) work, they're really sharp so you shouldn't experience any problems. It shouldn't take you long, but the rewards are huge. I strongly recommend it.

I'm familiar with pretty much everything you're running there.

Love the B20s, though my pair was fully P10 modded for me by Dave. They were really good, stock, in OB. They were completely awesome in OB once I cut the dust caps and installed a pair of P10 phase plugs. After the full mod, though, they sounded really odd in OB, I think mainly because the front wave had been so modified and the back not at all that it just didn't match up anymore (of course, they sound ridiculously good in sealed cabs doing HT and music duty in my living room). The lessons I learned were that the B20 sounds weird at certain listening angles if you've cut the dust caps but haven't installed anything (phase plugs I know work great, but you might also try the socket method for something quick, a bit cheaper and easy to source locally, or maybe you can fashion your own plugs somehow; whatever you have to do, its a totally worthwhile upgrade, dollar for dollar), and that wildly modding the front face without doing the same on the rear will likely cut your B20's OB career short. I never had problems with the cupped hand sound, though it would seem with the folk here who report it, the bit of foam or whatnot loosely tucked around behind the whizzer cone pretty reliably helps out.

The APA150 is great for the purpose of being a stereo sub amp. It also gives you lots of flexibility for future experimentation and even a back up stereo amp for any purpose that comes along. I had initially been driving a pair of Dayton RS225-8s with mine (which sounded completely awesome, btw, paired with the even more incredible RS100-8 fullrangers I replaced my B20s with once they got moved to the living room), but they didn't quite have the oomph on OB that I was looking for and then one of them developed a hideous rattle.

At that point, I picked up 4 of the 10" square frame woofers that PE had started carrying at the time (this is like 10 months ago now), partially to play around with a possible cheap OB surround system for my parents' new appartment, but we decided to go another direction so they got added to my RS100s in the office. 1 per side was fine for most music, especially at moderat "work" levels, but were regularly ground out on any DVD content, some more bass agressive music, or even more tame tracks turned up too far. Getting two on a side was going to be problematic height wise, until recently where the desk situation changed to where I've got 1 + RS100 up top around ear level and then a second down below just inches off the floor.

This setup has been very satisfying, low response, higher volume than I can actually listen to in that space, no mechanical distortion. I watch movies, play games, listen to music and even play my guitars (primarily electric bass, no less) over this system. Its not the absolute best I've had in sound quality terms, but its completely capable and reliable to function without any mechanical issues regardless of how I push it, which of course obviously hadn't been the case using just a single 8" per side, regardless of how much higher quality they were.

What that tells me is that with your Goldwoods, you should be able to get similar sound quality to what I have, but you might find yourself hitting some mechanical limits if you're looking for too deep of a response and/or too high output volume. I haven't heard those particular Goldwoods, but just going by the general state of their drivers, specs, etc. I would feel safe in guessing that each one of them is noticeably more robust and capable than one of my square frames, but likely not really close to 2 per side. If you stay within the limits of what the Goldwoods can do, it should sound great.

Other things to note ... You may need to look into a helper tweeter since the B20s don't cover the very top end without some sort of EQ (which may or may not be something you're interested in). Gozilla loves the piezeos (which I haven't tried yet myself) so if you'd like to try one of those, just look up his guidance (you'll need an inductor and a capacitor, both cheap). I've coupled my B20s with very small, inexpensive Datyon domes and with much more expensive B&G Neo3PDR planar drivers (which is what's in the the sealed cases with the B20s in the living room right now), using caps between 2 and 2.5 uF and they always gave immediate gratification and no desire to tweek or upgrade. Also, using the receiver to amp the B20s will probably always give you some hassle or another, the most primary of which is that the sound quality won't ever really let the B20s shine (trust me, I know, having spent like 2 years running them with my old Pio 411, and even my newer and much better sounding Panny X57 with digital amps pulling plows in the living room, there's obviously room for improvement). I'm partial to digital amps, and I have run the B20s with the original Sonic Impact T-amp and then with the second gen one. I could easily recommend giving the Dayton DTA-1 a try since its cheap and should be reasonably similar to the original Sonic Impact its modeled after. Personally I am very interested in trying the newer, higher end and higher powered DTA-100a they have now or maybe something put together from one of their Class T kits. Then if you look around, you'll see lots of commentary from folks with a very nice assortment of tube amps, class A solid state amps, stuff designed by Nelson Pass, and on and on, that could be researched and tried.

Or, and I like this option more and more lately, you can ignore everything I say, and just enjoy the setup you have, because at the end of the day, I know for a fact that it sounds pretty good :)

Thanks for the comments and tips, Kensai. Everything you're saying rings true. I was actually planning to pick up a DTA-100, but they went out of stock just before I placed my order with PE and I didn't want to wait. I will definitely get something else long term. I've been eyeing up an EMP Tek tube / hybrid integrated amp, too. Who knows - it might happen.

I've also thought about mounting tweeters -- maybe the B&G Neo3 with the back cup removed. Some seem to think that the non-PDR is better for OB. What do you think? Also, if it's run dipole, would it be good to get two of the B&G mounting plates per tweet (would that even work) or just perch them naked at the top of the baffle?

What width was / is your OB and were did you cross the B20's to the woofs? Or did you run the B20's full range?

Thanks again. As soon as I get enough posts under my belt, I'll put up a few pictures.
>>> They were completely awesome in OB once I cut the dust caps and installed a pair of P10 phase plugs. After the full mod, though, they sounded really odd in OB...

Hi Kensai, you have been thru so much with tweeking the B20 (or BOFU as many call it). I like mine with the Sonic Impact amp too and also just purchased the black Dayton copy as well as the more expensive and powerful DTA 100... and i have the APA 150 and use it well on a pair of Alpha 15's in H-frames. In fact, if you want powered woofers i can't think of a much better amp setup than a DTA 1 or 100 along with the APA 150 to power the woofers. If i did not have my (expensive) tube amp and was starting fresh this is what i would do... audiophiles be damned! These amps sound excellent! (I will let you know how the more expensive DTA 100 sounds compared to its smaller brother after i listen for a while. I hope it was worth the extra $$$).

As for cutting the dustcap off the BOFU, i had great luck sitting it on top of my desk at work and spinning it while using an Xacto knife. The spinning (rather than sawing) allowed me to drag the tip of the knife along the dustcap over and over until it it was cut off. The circles are nearly perfect! You can put a plug in the hole if you want but that's up to you. I felt the cupped sound was less for sure without the dustcap. I also felt without the dustcap the need for a tweeter was less. If you raise the B20 to ear height and aim them at you they don't need tweeters... If you listen off axis they need tweeters. I have used tweeters firing forwards and backwards with them and really prefer backwards. But i think i like a bit of a mellow sound.

I think the BOFUs are great in open baffle too with bass support. Let us know how much bass is added with the powered Goldwoods. I'm curious how much weight they are adding to the overall sound of the Pioneers.

As for cutting the dustcap off the BOFU, i had great luck sitting it on top of my desk at work and spinning it while using an Xacto knife. The spinning (rather than sawing) allowed me to drag the tip of the knife along the dustcap over and over until it it was cut off. The circles are nearly perfect! You can put a plug in the hole if you want but that's up to you.



Seconded... Probably a better method than the one I suggested.
I've not tried the non-PDR Neo3s, so I can't speak to that, and no, you won't be able to swing 2 faceplates in dipole unless you're using something of perfect (and quite thin) thickness as your baffle, or something compliant (such as a, say, a double thickness of foam core; just throwing that out there ;-p ). I used the surface mount one on all my dipole installs of it, and it sounded really awesome, dollar for dollar better than any domes I've ever heard, but in this case, they're not carrying much of the load, so other than being a dipole driver, might be overkill (I've often thought of mounting a pair of of cheap piezos mounted opposing and as close as possible to creating a dipole point source and seeing if that might shed some light on what is audibly different between monopole and dipole with a supertweeter). Doubt that mounting them free of faceplate or baffle will do anything but make them sound better in this situation (baffles primarily being used in OB to control lower rolloff frequencies, and you're pretty much gonna want your tweeter to be silent before it gets down to 12kHz in this situation).

Zilla, how far away were you sitting from them when you were listening with just the dustcap removed? I was sitting at 3-4' in a desktop situation, and felt very definitely as if I could hear down into the center, a sort of absence. I imagine that at any real distance, that would go away quickly as the sound from all the various points along the driver merge. The phase plug was an immediate upgrade all around for me, and totally worth it, dollar for dollar. The full cone treatment/EnABLing would have been far to expensive to have done and just too much for me to really do myself, so wouldn't have happened if not for Dave's kindness/curiosity at the time. At ~$100 a pair, I don't really know of anything that will get you what B20s+phase plugs will. But at the $300-$400 a fully P10ed pair would go, I think you've got enough other options that will make it alot harder to decide.

I never ran the B20s with any kind of bass augmentation. The APA150 and various bass only drivers only happened after my B20s got EnABLed and them shifted to duty in the big room. At the time, I ran them on baffles that were only 18" wide, and with EQ. I was able to get solid down to about 50Hz, and though my ears were telling me I could only hear up to about 16kHz (which was proven wrong with the advent of my RS100s), I could get way more heat up top than I could possibly want with only modest EQ. For moderate level nearfield duty, a pair of stock B20s, a T-amp, a spare CAT5 cable (or zip style extension cord), a sheet of foam core (or a couple of bamboo cutting boards ;-p ) and whatever various and sundry EQ options you can get from your computer as a source will give you more for $100 or less than basically any amount money can get you trying to buy high end "multi-media" speakers. Trust me, I'm really tired of knowing ;-p

>>> Zilla, how far away were you sitting from them when you were listening with just the dustcap removed? I was sitting at 3-4' in a desktop situation, and felt very definitely as if I could hear down into the center, a sort of absence.

LOL, i just measured... about 6-1/2 feet from the drivers when i listened to them in sealed boxes. When i had them on OB i was maybe double that distance away. I know what you heard but when i sat down to listen i was farther away than you were. Yeah, $100 for a totally tweaked pair of B20s sound like a very good and interesting alternative. I'd cut the dustcaps off again if i got another pair but would like to try a proper phase plug and not the home depot socket wrench... which did not seem to do much imo.

You take the sockets, some wooden christmas light bulbs (from a craft store like Hobby Lobby or Michael's; basically a wooden facsimile of a big bulb from what would these days be thought of as an outdoor set of christmas lights), shave the screw-in portion of the bulb and then take a rubber mallet and drive that into the wrench side of the socket. Did that along time ago with my old Kenwood 6"x9" bicones, and it worked pretty well, though those drivers didn't have anywhere near the potential of the B20s.

If you want to get crazy and try funky shaped plugs (like on Lowthers and such), you just get a length of the proper sized dowel rod and various wood shapes from the craft stores to place on top. I actually still have a pair of wooden balls, somewhat smaller than baseballs that had convenient flat spots on them (so they wouldn't roll away when placed in whatever the heck they had originally been intended for), meaning to make them into plugs for the old Kenwoods, but those plans got completely overrun by the advent of a pair of B20s for Christmas.

I spent quite a bit of time last evening and this morning measuring my speakers with different crossover combinations.

My measurement capabilities are crude, but I found a cool signal generator for the iPod Touch / iPhone / iPad. It's called AudioGen ($1.99). I use that on my Touch to generate sine waves at frequencies of interes. I use a Radio Shack digital SPL meter. Since the accuracy of that meter is questionable, I used an app called SPL Meter on my iPad to verify measurement. The speakers are set up two meters apart and two feet away from the back wall. The speakers are toed in toward a point two meters from each (equilateral triangle). I put the meter at that point and at the height of the B20's.

The room is 9 feet by 12 feet by 9 feet high.

Cutting to the results, the speakers appear to work best with the crossover on the APA150 driving the Goldwoods set at ~85 or 90 Hz (the knob has markings at 50, 100, and 150, so the setting is an estimate) and with the B20's running full range. With these settings, there is strong response down to 50 Hz and reasonable response at 40 Hz. There is a several db peak at 60 - 70 Hz and a nasty room mode spike at 90 Hz. There is a pretty big dip from 200 to 400 Hz and a several db hump from 500 to 1000 associated with the baffle peak.

If I try to raise the crossover on the woofers, it will fill in the hole at 200 a little, but makes the 90 Hz peak worse.

Overall, I really like the sound of these. In this small room, the base is very impressive, though I haven't pushed them much past 80 db yet. My wife, who likes good music but isn't into the whole audio equipment hobby, listened to them and was impressed. She asked how much the parts cost. When I told her $125 plus $150 for the APA150, she said, "Good job."
Thanks for the thoughts, Godzilla. I will try mocking up some wings in cardboard and giving them a try.

In the meantime, I extended the low pass on the woofers up to about 125 Hz to fill in the hole at 200 - 400 somewhat. I decided that sounds better despite the room mode peak at 90 Hz.
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