# 3.5” Tectonic BMR bookshelf



## 420tabbycat (Dec 23, 2013)

I’ve had the itch to play with the BMR drivers ever since @ErinH reviewed the 2” fullrange with such fond regards. I bought a pair without any real idea what I would do with them and they still sit in the shop. I also bought the 3.5” a few weeks ago and I did have plans to use them as shop speakers in some shape or form. I looked at many amps of various forms, small multi way plates, raw amp boards and little hobby 2 and 2.1 channel. I ended up with a simple 2 channel hobby amp from Amazon.

I let the ideas marinate for two weeks or so while modeling various enclosures. I thought the response in a big bass reflex alignment was the best for my needs. I looked at the knock down enclosures on Parts Express and chose a fully assembled black vinyl two way box. It was perfect for the BMR and a 6.5” radiator. The bmr dropped right in the tweeter spot perfectly and I had to shave about an 1/8” for the Dayton designer series PR. It modeled down to roughly 50hz with a 2-3db hump at 100hz because of the speakers high Q, there is also a few db spike right around tuning.

Yesterday I had all day of mandatory house arrest due to the storm (ian) and got everything together enough to listen to some tunes. It’s pleasantly mild sounding and doesn’t grab one’s attention. The bass is not flat, below the 100hz hump it gently slopes down until the hump at tuning where it comes alive a little. The treble is pretty ok, I’m sure if it had a small neo it would have sparkle but it’s not in the intention of the project to build a reference monitor. These will remain composed up to around the point where it is too loud for casual music enjoyment, at least for me. I’m expecting to dial in the bass a little better when I measure and adjust the pr weight. At the end of the day I believe I could have gotten more from my ~$200 invested from a good budget 2 way bookshelf from the internet but maybe not by a whole lot. I do like the result and may eventually get a Dayton dsp amp board and build a two way active setup.





































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Tectonic TEBM35C10-4 BMR 2" Full-Range Speaker 4 OhmBy combining the benefits of bending-wave technology and pistonic modes of operation, Tectonic's TEBM35C10-4 BMR 2" full-range delivers extended frequency response and extremely wide directivity. The small form-factor is ideally suited for...




www.parts-express.com













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Dayton Audio BR-1CAB BR-1 6-1/2" 2-Way Speaker Cabinet PairDayton Audio BR-1 Cabinet pair. 6-1/2" 2-Way cut-outs. The cabinets are made of 5/8" MDF finished in an unobtrusive "black ash" vinyl laminate and include grills with black cloth, ports, and binding post terminal cups. All driver holes...




www.parts-express.com


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## 1978monte (Aug 16, 2009)

Turned out sweet! 

I built some 2-ways awhile back with the Dayton RS225 and a Peerless Tweet dubbed "beast mode" cause it can play super low and it sounds great. I got them in the garage.

Using a Dayton Dsp-408 and a Pre hdmi Denon with EXT. inputs.. This gives me 6x140 watts bypassing all processing in the Denon so it's operating as just a amplifier.


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## 420tabbycat (Dec 23, 2013)

I’m definitely happy with them, being realistic about their abilities of course. The bmr’s really do have wide dispersion, I’ve no idea how consistent through the passband but I can hear clear treble pretty well off axis. How much space are you giving those 225’s and what kind of enclosure? I have two rs180-4’s lying around but they seem to want more volume ported then the .52cf available and passive radiators fall off too quick to be worth the doing. For sharpening blades and greasing zerks these will be just fine.

Something that has been increasingly on my mind is the Purifi 4.5” drivers. I’ve yet to model them but I’m thinking tiny towers with the matching passive radiators. In all reality I could probably widen the hole where the bmr’s are and just keep the Dayton pr and get down in the 40’s or maybe even lower restricting the amplifier power to casual levels. The smaller Gladen aerospace tweeters would be awesome but now we’re talking about $1,000 speakers that are probably beat by $400 store bought lol, Elac n done 🤔

I’ve been getting frustrated trying to figure out how people run active in home audio. Best I’ve found are some Dayton Audio dsp amplifier boards which are really cool but I’m unsure if they’re up to the task of running Purifi and aerospace with the clarity deserved. And then I’ll have to fabricate a home for the electronics and add remote control preamp, power supply and whatever else. A *much* more cost effective route would be two Dayton tcp 4” per enclosure and the 2” bmr’s. Dayton nd105 4” could be cool if the high qts doesn’t muck up the lower response. Tcp’s seem cheap and effective though. Idk, I still like my little bmr box lol.


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## 1978monte (Aug 16, 2009)

I've got the 225's in 1.25 tuned to 36hz.


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## 420tabbycat (Dec 23, 2013)

1978monte said:


> I've got the 225's in 1.25 tuned to 36hz.
> View attachment 349370
> View attachment 349370
> View attachment 349371


Now that’s what’s up


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## 420tabbycat (Dec 23, 2013)

Wanted to add for anyone interested that I got my Dayton 4x30 dsp amp board dialed in and the 3.5” bmr’s definitely sound pretty good. My opinion is the treble is fine, no air or anything like that but it’s listenable. A build like this would be perfect for an apartment. If I was planning to keep this as is I would probably drill a hole and press a 5/8ths or 3/4” neo tweeter in.

I don’t believe I’ll ever not have an active home setup, or really any non active stereo after this recent endeavor.


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