# Dayton/BMS Speakers



## carmaniac13 (Jan 3, 2011)

Hello all. Here's a summary of a set of speakers I'm just finishing up for myself.

First the background info. Eventually, I plan to build myself an "ultimate" pair of speakers, consisting of a Synergy horn that'll do ~300Hz up, and most likely a horn loaded bass bin with two 12"s to handle below 300Hz. I've started playing around with modeling for that, and arrived at a BMS 4550 compression driver, as yet undecided midranges (either two or four per speaker), and two Dayton Audio PA310-8 woofers per speaker. I'm finishing up college right now, so that project is on the back-burner until I graduate in May.

Over this past summer, I bought the two tweeters, and the four woofers. I decided to whip up a pair of PA speakers to use in my apartment, for parties and such. I ordered some Dayton Audio H812 horns for the tweeters. I basically just wanted to get the cheapest horn that would bolt up to the BMS's. This was my first venture into designing full range speakers from the ground up, so I wanted to get my toes wet before I tackle the Synergies. I've designed and built quite a few subwoofers in the past, and built speakers not of my own design.









The enclosures didn't require too much modelling. I was gonna do ported, but got really lazy and made them sealed. They're trapezoidal, to help cut down on standing waves, and to not occupy too much room. There's one brace parallel to the top and bottom of the enclosure, which sits between the woofer and horn, and has a bunch of 2" holes cut out. I do all my enclosure design in Solidworks, so all the dimensions came together there.









Then I built the enclosures.




































The top and bottom are inset 1/4", because I plan on carpeting these, so that's where all my seams will go.

Then I took individual driver measurements in REW with both drivers mounted in the enclosures. I took measurements from 1m, and every 11degrees from 0deg to 55deg. Measurements weren't exactly ideal. They were taken in my living room, with plenty of reflective surfaces, furniture, etc...

Then I set out to design the crossover. I used the Passive Crossover Designer 7 spreadsheet for this. I came up with a crossover of around 1200Hz. The woofer is a 2nd order low-pass. The tweeter has a third order high pass, L-pad attenuation (about 14dB if I remember correctly. Those BMS's are LOUD :yikes: ), and contour to keep the tweeter flat. The contour is the 5.6uF cap, and it gradually raises response as frequency increases.









No build pics of the crossovers. The components are hot glued to a small piece of MDF.

Then here's the speakers set up with the rest of the system. Like I said, they'll be getting black carpet as a finish. I'm considering building stands for them, to match my TV stand. The TV stand, subwoofer, and black speakers in the back were all built by me also. The TV stand is poplar with a Minwax Colonial Maple stain. The sub is MDF, with poplar veneer, and the same finish as the TV stand.









I finished installing the crossover around Thanksgiving, but I just finally measured them today. Did the same thing as for the individual drivers: 1m, 0deg to 55deg in 11deg increments.

Here's the 0deg measurement with THD data.









Worth noting, SPL data for any of my measurements isn't calibrated. The woofers are rated at 97dB sens. I believe, so these speakers probably fall somewhere near that. The tweeters peak out around 113dB sens, so they needed quite a bit of padding. As you can see, the response is pretty flat to 60Hz, which is actually much better than I was anticipating, especially since they're sealed.

The woofers are rated for 400W+, and my HK3490 has 150W+ to offer, so I've got enough juice on tap for my apartment haha. These things get STUPID loud. :devil: The tweeters are so padded, they'll never see more than 5W or so at these levels. Those BMS drivers are good for 133dB output at max power, so they'll have no trouble dealing with my shenanigans.

As you can see, there's a bit of a dip in response around the crossover region, and a significant dip around 800Hz. It's not too bad, and to be honest, I don't trust my measurements/environment enough to blame that entirely on the crossover. But I think the crossover is causing some phase issues in that area. The phase plot/group delay is a bit of a mess in that region.

Overall, I'm very pleased with the results. These things sound amazing! Female voices, and string instruments just sound like they're in the room with you. With the volumes I like to play at on occasion, I don't think I'll ever be going back to wimpy little dome tweeters any time soon. Compression drivers are just so effortless, and I've got endless headroom.

Thanks for reading, hope you enjoyed!


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## vann_d (Apr 7, 2009)

Looks like an awesome project! I'd like to see your polars if you have them.

When you get around to your "ultimate" build, I'd seriously consider Acoustic Elegance for the midrange/midbass.


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## carmaniac13 (Jan 3, 2011)

Here's an overlay of my polars. This is on an exponential horn, so it can be a bit beamy. This is also my first foray into horn speakers, so I'm not quite sure what polars would look like for a more constant directivity horn.










I read that polar plotting capabilities are in the works for REW! I'll keep my fingers crossed for that.

I'll have to look into Acoustic Elegance. Right now I'm eyeing the Eminence Alpha 6" sealed mids, which model quite well. Four of them on the horn would give me around 105dB sens from 220Hz-1500Hz roughly. But that was just playing around a bit. I'll get much more serious about that design come summer time. I'm closely following Paul Spencer's work on Redspade Audio, and I believe he uses Misco mids, which are hard to get without a group buy it sounds like.

Playing around with the bass bin, it seems I can get about 109dB sens from two of those 12's Daytons in a moderate sized enclosure. Right now I'm thinking it'll end up something like a Klipsch Jubilee bass bin. Then I can wire the 12s in series to pad them down to the ~105dB I'm aiming for overall.


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## natehansen66 (Feb 20, 2011)

Cool! How did you do your measurements? You'd get a better picture of your response from 600 or so up if you gated the impulse with the speaker on a stand midway between the floor and ceiling. You can change the gate time in Preferences/Analysis or the IR Windows button at the top in REW. Depending on where the speaker is in relation to room boundaries the first reflection comes around 3-4 ms. You want to set the gate before that. The gated measurement will also show the phase accurately through the crossover region.

I'm excited to see what happens when you get rolling on the Synergys! I just built a variation of the Synergy and they are really cool......FYI Paul is using 4" Celestion mids (I got in on the group buy, they work very well). I think you can get the 5" Misco, but you have to order a whole box. 16 in a box if I remember right.


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## fusseli (May 1, 2007)

Awesome build! You plan on serving a concert venue in your living room, I see :bigsmile: Definitely whip up some stands for these guys!

Other than what you point out the measurements look pretty nice. In PCD, how did you model your z-offsets? I'm trying to think of causes for your unplanned dips. Can you post your PCD file showing the top window and include summed response, both sections (not raw driver output), and phase of both sections? What made you decide to pad the tweeter with the parallel resistor? In terms of amp power that's not the most efficient way to go. I wonder if you could get the same performance with a series resistor instead, and tweaks in your contour to compensate (play with placement before vs. after the crossover).


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## carmaniac13 (Jan 3, 2011)

Yea, my measurement process wasn't close to ideal unfortunately. I had the speaker sitting on the floor, with the mic 1m away, and fairly close to the couch, a wall, and the TV stand. I just wanted to get a general sense of the response. Good testing will have to wait until I'm back at home after the semester. The measurements I posted were all with the default windowing. I was mostly interested in the frequency response, simply because I can't get good measurements right now to expect reliable phase data. I may play around a bit with the windowing and see if I can cut out the room reflections. Don't know how successful I'll be though.

My individual driver measurements were taken under the same conditions. So when I designed the crossovers, I knew my phase data was unreliable and virtually useless, so they were designed mostly with magnitude in mind. I'm checking my PCD file, and my geometry data didn't seem to save. (I know I entered XYZ values for the drivers though when designing.) I don't remember what I used for the Z value of the tweeter. I wasn't sure where it would be with a horn: at the throat, at the mouth, or somewhere in between.

Looking at my raw driver measurements again, and the PCD file, the 800Hz dips are in the raw woofer response, so that explains those away. Might be floor bounce. The 1-2k dip is also kind of there in the predictions from PCD. I suppose I should have compared my measurements to the PCD predictions first haha. They're fairly close.

As for the tweeter crossover design, part of the issue was that I didn't have impedance data for the BMS's, and I haven't built an impedance test rig yet. The 8ohm and 2.2ohm resistors form the L-pad for the tweeter, which both attenuates, and helps keep the impedance constant to the left of that point in the circuit. This allows the actual high-pass section to not be as dependent on the impedance of the driver, since the total impedance seen by the HPF will more closely approximate a resistive load with the full L-pad in place.

I figured power loss wouldn't be too bad, since the L-pad only sees the output of the HPF, and there isn't nearly as much energy in this region as there is down low. As far as amp power, it should pretty much just look like an 8ohm load the whole way through. And my receiver is good for 4ohm loads as well, so it's not sweating. I also knew that these speaker won't be seeing any real PA duty, and so I wasn't worried about excessive heat from those resistors. But in any case, they're rated for 20W, which neither of them should ever see.

These speakers are meant to just be a bridge point until the Synergies, so I didn't want to do any trial and error and voicing with the x-over, just a one-and-done approach.

When I do the Synergy speakers, efficiency will be the name of the game, so I wouldn't run that parallel resistor. But by then I'll also have measured the driver impedance data, and will be able to work around that, instead of treating it like a black box.


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## fusseli (May 1, 2007)

I'm smellin' what you're steppin' in. I am in no means questioning your design! Really, it looks awesome. The only thing I'd suggest would be to see what changes having x,y,z in PCD would make to your as-built crossover. I believe that Z measurements should be taken from the top of the voicecoil, so the base of the throat would be a good place for the horn driver. Those driver offsets are pretty critical for acoustic phase alignment of the HP and LP sections...


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## carmaniac13 (Jan 3, 2011)

What kind of rough window settings would you guys recommend to isolate driver response and help cut out room response? I don't see any data in the negative time of the impulse response, which is normally where reflection data is located, correct? I normalized the IR to t=0, and it zeros out by -0.5ms or so.

And yes, I enjoy my music loud sometimes. But there's no sense in trying to play loud if all you get is distortion. These speakers don't disappoint, and I also don't have to worry about stressing them out when I turn things up, because even then, they're still just loafing around and nowhere near their limits.

The pipe speakers I have sitting next to the TV I've run through the ringer. I bent a voicecoil former on one of the woofers when the cone got thrown too far and exited the gap haha. Luckily those woofers have a pretty open basket design and I was able to get in there and bend the former back so it wouldn't scrape against the yoke. I've also taken the tweeters apart before, and removed what I can only assume to be bits of congealed ferrofluid off the coil. My guess would be from them overheating. So these PAs are a welcome upgrade, in terms of sound quality, volume, and reliability.


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## natehansen66 (Feb 20, 2011)

carmaniac13 said:


> I don't see any data in the negative time of the impulse response, which is normally where reflection data is located, correct? I normalized the IR to t=0, and it zeros out by -0.5ms or so.


No, negative time would be before your speaker actually makes sound 

Once I have enough posts I'll post up a link to a good article describing the process to doing good gated measurements......unless somebody beats me to it.


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## natehansen66 (Feb 20, 2011)

OK I'm legit now :devil:

Here's the gated measurements article: http://www.hifizine.com/2011/03/refining-a-4-way-open-baffle-speaker-minidsp-2x4/


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## carmaniac13 (Jan 3, 2011)

Thanks for the article! I gated my close mic measurement, which helped clear up the phase issues a lot. But given the test circumstances, I still don't trust the measurements, as they're contaminated with floor bounce still. Since the path length difference is so small, I'm pretty sure the reflection is buried in the line of sight impulse.

Once I build my better speakers though, I'll be back home, and can take good measurements with the speakers elevated outside. I live in a rural area, so I don't have much background noise to contend with. (Or neighbors to tell me to stop making alien noises, for that matter haha)

The phase right around the crossover jumps about 180deg, but overall, the woofer and tweeter are roughly 90deg out of phase. I may try un-inverting the tweeter and see if that clears up the crossover region.


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## fusseli (May 1, 2007)

90 deg out of phase, you say? Did you intend on non-summing odd order (butterworth) slopes, or summing even order? This is one of the reasons why I wanted to see your main PCD window...


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## carmaniac13 (Jan 3, 2011)

I just tried to get the magnitude responses where I wanted. My phase data was garbage, so I had no goals for phase alignment. To be perfectly honest, I've upgraded my friend's Klipsch RF-7 crossovers, and they were 2nd order LPF, and 3rd order HPF, with an inverted tweeter, so I figured that would be a good base point. For those that don't know, those are 2 10" woofers and a horn tweeter, crossed around 1800Hz I believe. Then I just tweaked the values to suit my needs.


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## carmaniac13 (Jan 3, 2011)

I finally got around to putting the black carpet finish on these. My photography skills don't do them justice. They look awesome in person. The black carpet absorbs a lot of light, and these appear much darker than in the pictures, which I really like.


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