# Biketronics BT2250 Prototype Review - Modified BT2180 [email protected]



## 2010hummerguy (Oct 7, 2009)

After months of deliberation, misguided attention, unrelated delays, etc., I was finally able to install the BT2250 prototype that Biketronics recently built for me. The team at Biketronics and myself had been kicking this idea around for quite some time after the overwhelming success I've had with the BT4180 amp powering my front stage. I needed either a medium-power two channel or a big mono amp to drive one or two of my Stereo Integrity BM MKIV 12" subs and thus the idea for this amp was born.

For anyone unfamiliar with Biketronics, they are a small family owned and operated electronics company based in Moscow, Idaho. They specialize in making aftermarket electronics for Harley Davidsons, including high-end audio equipment. You can view their website here: Biketronics Inc

Biketronics builds their amplifiers using Hypex Class-D amp modules, a design many of you know I absolutely love thanks to their tiny size, big power, class-leading efficiency, and Class-A frontend. Biketronics builds their own DSP controlled preamp boards as well as the specialized power supply which converts 12v to the necessary high voltage required by the Hypex modules. They also build their own metal enclosures which are a cool understated black box with silver logo on front and employee signatures in silver on the back. Very cool that, aside from the Hypex modules, everything in these amps is soldered and assembled in their small Idaho location, meaning they are truly “Made in the USA”.

The standard BT2180 and BT4180 amps use two and four Hypex UcD180OEM amp modules each, respectively, which provides a very substantial amount of power in such a tiny package. However, the team at BT mentioned to me that a more powerful UcD250LPOEM module is nearly identical in size to the UcD180OEM so two could easily be installed in a BT2180 chassis. We had also kicked around ideas for a single UcD400OEM or UcD700OEM module in the BT2180 or BT4180 chassis but the stereo UcD250LPOEM design would require the least amount of modification to the power supply and enclosure.

Another reason why I love Hypex amps is how linear they perform with varying impedances. Though existing documentation from Hypex does not report 2 ohm performance, reading up on the UcD250LPOEM modules and using various testing sources, we concluded these amps should make ~400w RMS per channel at 2 ohms which is a great match for the SI BM MKIV. Furthermore, analysis of the max current these amps are capable of yields max output at 2ohms with some losses at 1ohm, though fully stable. Though 20% less RMS power than my Vibe Litebox Bass 1 mono Class D amp which is rated for 500w RMS at 2 ohms, I was gaining a second channel at roughly 1/3 the size. This smaller footprint meant I could stuff the modded BT amp next to the BT4180 in the factory amp location and then I could reinstall the plastic cover for the rear interior of my truck's cab which also doubles as sound dampening. It's a win-win, assuming the 2250 can perform well. For reference, here is Hypex’s datasheet for the UcD250LPOEM: http://www.hypex.nl/docs/UcD250LPOEM_datasheet.pdf

A regular BT2180 on the outside:









Picture of the internals, including the UcD250LPOEM modules:









It’s also interesting to note other companies that use Hypex modules which includes some Genesis home amps, 10+ boutique high end makers including Channel Islands, and specific to this application, Rythmik Audio and GR Research for their wide array of subwoofer amps. This is especially interesting because Hypex amps typically have flat output/response down to 0hz, making them a great option for driving subs. My Rythmik FV15HP in my home theater is a BEAST with one 15” GR Research driver powered by a 550w Hypex amp and the FV15HP is routinely tested with substantial output to nearly 10hz, driver limited. Insane!

Fast forward to last night, I was locked and loaded to take my new Nikon D500 camera out kayaking for some wildlife photos; there are at least six Bald Eagles taking spring refuge in the local wetland and on my bucket list this year is to photograph one from water level catching a fish. However, I had been laboring over yard work all weekend and I knew if I spent 2-3 hours on the water, I would be anything but physically functional for my day job on Monday. So, instead, I decided to go kayaking after work on Monday and use the pleasantly warm 75 degree Sunday evening to install the BT2250 amp that had been sitting in my office for the past few weeks.

Now installing these amps can be a little tedious because they are meant to be installed in a Harley motorcycle. Normally these amps have a ~45hz high pass filter to keep bike owners from blowing their speakers when cranking Def Leppard at 80mph on a Harley Ultra Classic which means their power draw on a bike is going to be much less than an amp used for sub duty. The BT2180 is usually shipped with ~12-14ga. power/ground wires but I wanted to make sure I’d have enough wire gauge for subwoofer power demand. I went to the BCAE system power wire calculator which I highly recommend you save to your favorites: http://www.bcae1.com/images/swfs/systemdesignassistant2.swf

16oz. Aquafina for scale:









A quick calculation showed that I needed at least 10 ga. power wire between my distribution block and the BT2250 amp to avoid melting any wire, assuming 400wrms output at 90% efficiency. When I add the second SI sub I will need to upgrade from 10ga. to at least 6ga. according to this calculator. Stuffing 10ga. into the factory BT2250 terminal was not an easy task so I’ll need to research some options when the sub expansion happens. 

Together at last, BT4180 and BT2250 squeeze 1520wrms into the factory Hummer amp footprint:









So, about 9:45pm last night everything was ready for initial testing. I fired up my P99 and with my iPhone plugged in, I navigated to Spotify which is now my music source for 95% of my listening. I’d been rocking out to Flo Rida most of the day on my headphones while mowing the lawn and weed whacking so I immediately pressed play for “My House”. It has a nice subtle drum kick in the intro verse before transitioning to a deep bass line during the chorus. This bass line gets pretty intense when you crank it up and the BT2250 was certainly putting the BM MKIV through its paces. Next, I played Jane XØ’s “Hard To Forget” which has some intense deep bass typical of current EDM fare. Holy smokes this thing is FULL. What’s more interesting is that I’m noticing control of the sub that was never present with the Vibe amp. What?! I must be delirious from the heat and exhaustion. Plus, it is now 10pm and I probably shouldn’t be cranking my system in my driveway, time for bed.

Monday mornings are always a gamble because my biggest client has 90% of their IT staff located overseas and by the time I’m logging in, they’re already done with the work day. So when I open my email inbox at 8am, it can be anywhere from “nothing-went-wrong-over-the-weekend” and I’m off to other projects or, more likely, things went sideways during a Saturday change window and I’m about to spend most of my week organizing resources to get things back on track. To my pleasant surprise, zero issues had happened and so it was business as usual. Which meant a lunch hour listening session!

After a very restful 8 hours of deep sleep and a very productive morning of work, my wits about me; I was ready to attack the perception I’d developed the night before. No way was the sub sounding “more controlled”. To me, a sub amp either works or it doesn’t; there isn’t much in-between. I was expecting some trade-off in output which would hopefully be made up by adding the second BM MKIV powered by the extra channel from the BT2250. I always enjoyed the sound of my system using the Vibe Litebox Bass 1 but I also always felt I was missing out on some output. I must admit that now I do not feel this way and the single BM MKIV may be all that I will ever need.

Another thing to note, with the Vibe amp I always felt like I was reaching the maximum excursion of the BM MKIV at the P99’s 45 volume level using some of my bass heavier tracks. However, using these same songs I was getting MORE output at lower levels and with less cone movement. Now I know this is pretty hard to claim without specific measurements but the difference seemed exceptional; otherwise I would not include this observation. So with that, I played the following demos for further investigation:

Vic Mensa w/Skrillex – “No Chill” – I have NEVER heard the BM MKIV fill the cab of my truck this much and because of this song I will be measuring SPL when I get the chance this week. I was cranking the P99 to volume level 50 and still not quite reaching maximum excursion of the BM MKIV. I am suddenly realizing I may not need the second BM MKIV that’s been sitting in my garage since inception…WOW!
Skrillex w/Zhu and They – “Working for It” – Similar experience as “No Chill”, whether or not you like Skrillex and his “trendy” haircuts, his bass lines are legendary and no contest for rigorous subwoofer duty. Once again, the BM MKIV was articulating everything well below maximum excursion. Could this be a damping factor issue?

Vibe does not publish a damping factor for the Litebox Bass 1 nor does Hypex for the UcD250LPOEM. I did find documentation that listed the UcD180HG with a damping factor of 400 which is probably close to the 250, given the very similar design and components. However, this is a stretch without clear specs for the Litebox Bass 1. Time to send the Vibe amp to Biketronics for a go on the Audio Precision Analyzer and also testing for the 250 modules so that we can determine actual output at 2ohms as well as with both channels driven to really put the modified PSU through its paces. We’re headed back to Idaho for a wedding in about a month so I’ll bring the Vibe with me for bench testing, can’t wait!

Back to the subjective listening test, I wanted to switch things up from bass-head tracks to some rock to see how well this new combo handles more sensitive source material.

Foo Fighters – “The Pretender” – A very laid back kick drum and full realism without overpowering. Just perfect.

The White Stripes – “Seven Nation Army” – If Foo Fighter’s kick drum in “The Pretender” is understated, “Seven Nation Army” has a bass guitar and kick drum that are about as in your face as it gets. Huge and enveloping, on my dash and in my chest. I freaking love this song and the new combo make it all that much better.

Alt-J – “Hunger of the Pines”, “Bloodflood pt. II”, and “The Gospel of John Hurt” – Alt-J has a way with instruments that I haven’t quite experienced before with any other artist, except for possibly Audioslave. Their usage of unorthodox time signatures is risky yet rewarding but easily muddied with a poorly setup subwoofer. No issues here, the offset beats are clear and articulate, just as they were meant to be heard.

Okay, time to get back to work (and to write this review between work emails). Plus, the moms dropping their kids off at the home daycare across the street are starting to look at me funny. I’ll be adding more thoughts to this review as the week progresses as I’m able to get more listening time in during driving. And stay tuned for technical testing details in a little over a month when we put one of these and one of my Vibe amps on the AP tester. Until then, thanks for reading!


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## claydo (Oct 1, 2012)

Ok......great review!.....so how soon are the biketronics peoples gonna have this thing in production?


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## 2010hummerguy (Oct 7, 2009)

Hopefully soon, the hardest part will be scaling the updated power supply and addressing the power terminals.

What's cool is these are already weather sealed so they're perfect for marine use. I'd love a boat full of Hypex amps


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## edouble101 (Dec 9, 2010)

I think these are great amps but very limited in their output configurations. At least limited for car audio applications. 

I'd love to see a high power 6 channel and a 1500 watt mono amp.


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## 2010hummerguy (Oct 7, 2009)

edouble101 said:


> I think these are great amps but very limited in their output configurations. At least limited for car audio applications.
> 
> I'd love to see a high power 6 channel and a 1500 watt mono amp.


I bet a UcD700OEM on a beefed up BT4180 PSU would get pretty close to 1500wrms at 2 ohms. I know we've spoken in PM but refresh my memory, what speakers/subs are you using? I bet a 4250 or 6250 are pretty realistic configurations as [email protected]/[email protected] would probably have pretty decent output


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## deeppinkdiver (Feb 4, 2011)

Great review Emet! These amps sure are calling my name for an audition..


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## Babs (Jul 6, 2007)

Awesome stuff!! 

Man, I'd love to do a head-to-head with one of their 4's to something like a JL XD or my PDX's. Wouldn't that be the shiznit if they equaled or even bettered some 'namebrand' usual suspect reputable class-D's, being kinda apples to apples. 

I think I'm also intrigued by these also because I have a huge place in my heart for small U.S. business.
And no junk.. no crossovers and shhtuff that 'power user' folks with DSP capability don't want and wish wasn't there.
Man if it had 10 or 8 awg crimp-downs, it'd be the perfect tiny-space amp.

Makes me start thinking about some glassed engine-guard mounted "pods" for my Hard-Ball (the "better" American cruiser).. No fairing on the cross-roads bikes, alas. Put one of these in one of the cavernous bags nice and tidy with some kind of iphone DAC/preamp driving it.


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## 2010hummerguy (Oct 7, 2009)

deeppinkdiver said:


> Great review Emet! These amps sure are calling my name for an audition..


Duuuuuuude, how've you been?! Yeah you gotta hear these, I know you have some NICE speakers that would love the fat amount of power these monsters put out.



Babs said:


> Awesome stuff!!
> 
> Man, I'd love to do a head-to-head with one of their 4's to something like a JL XD or my PDX's. Wouldn't that be the shiznit if they equaled or even bettered some 'namebrand' usual suspect reputable class-D's, being kinda apples to apples.
> 
> ...


BT does some pretty cool stuff with saddlebag subwoofers and they also have a custom 7.1" coaxial that HAT made just for them. I believe Bill at BT is running four of these as subwoofers in his Maxima and he loves how they sound.

I am going to tinker with the terminals from inside the chassis to see if I can manually run some 4-6ga. directly to the PSU when I test it with the second SI sub. I've never had a JL amp in my truck but I know Hypex modules handle impedance at high frequencies far better, no tweeter issues here. I'd love to compare with some other high end Class D amps like the Alpine PDX, Sinfoni Presto, Audison Prima, etc.


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## Babs (Jul 6, 2007)

Yeah I'm certainly not in the "they all sound the same" camp. When I swapped out the clone amps (NVX like PPI) for the PDX V9 and F4 it was an instant "holy crap that's an improvement big time all around" moment. 


Sent from iPhone using Tapatalk


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## deeppinkdiver (Feb 4, 2011)

Architect7 said:


> Duuuuuuude, how've you been?! Yeah you gotta hear these, I know you have some NICE speakers that would love the fat amount of power these monsters put out.



Ive been good bud! Busy busy as always.. I may have to pick up one or two of these amps this year to play with. My Sinfoni Grandioso speakers will be driven by the La Prima set up, Prestigio, Prodigio and Desiderio.. I am also a firm believer in all amps DO NOT sound the same, not even close. Im running the SI subs also, times 4. Was going to mention I never did use that E3io if you know anyone with intrest in it- need to post it.

Glad your trucks coming together man, seems like a very simple and rewarding set up!


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## knever3 (Mar 9, 2009)

Make it and I will buy it!


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## teldzc1 (Oct 9, 2009)

I might have missed it in the review, but this amp isn't bridge able right?


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## 2010hummerguy (Oct 7, 2009)

teldzc1 said:


> I might have missed it in the review, but this amp isn't bridge able right?


The UcD modules can be bridged, though stepping up a module size yields more power per dollar. Obviously not an option if you already have the amp and need the extra power right away. I seem to remember there were current limitations with bridging the modules, I think it's in a post of mine in the 4180 review. Let me see if I can find it, I'll be right back...

Edit, found it including the full discussion on Diyaudio:



Architect7 said:


> Yes, bridging must be done internally but easy to do. Though I am not sure there is much benefit, sounds like they are amperage limited and operating a single unit at 2ohm would yield better results than bridging two units at 2ohms (or even bridged at 4ohms):
> 
> bridging ucd amps - diyAudio
> 
> For more power, a user would be better off swapping to UcD400OEM or UcD700OEM modules. This would require a custom Frankenstein amp and the current power supplies have not been tested to support this but in theory a BT4180 PSU would support a pair of UcD400OEM modules or a single UcD700OEM module.


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## knever3 (Mar 9, 2009)

Any updates on this amp or anything else in the works?


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## 05stisilver (Mar 9, 2016)

I have been trading emails back and forth with Biketronics and they seemed interested in making a sub amp with the UCD700 and another amp with the UCD400 module. But they said right now is the peak of their season (summertime) so they wouldn't be able to put something together until later in the year.


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## knever3 (Mar 9, 2009)

So it's nearing the end of the riding season, hopefully they are starting back on the sub amp because I would be one happy customer if so!!


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## KillerBox (Jan 7, 2011)

I gave up on them & bought 2 class D Arc Audio 1200.6


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## 2010hummerguy (Oct 7, 2009)

I am a bit late but the production BT2360 is now available:

BT2360 Two-Channel Xtra High Power Amp (XHPA) - Biketronics Inc

Still loving mine!


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## knever3 (Mar 9, 2009)

I see that the power input hasn't changed, will that allow you to run both channels without melting the wire? You had mentioned that you wanted to have a way of increasing size. Did you get a chance to test your vibe litebox against this amp when you were in Idaho?

Does this work at 2 ohms? I wanted to get a 10" sub DVC so I can make the best of the amp because it's not bridgeable. If I shop for a sub I want to make sure I get either a dual 4 ohm or a dual 2 ohm sub. If I remember right the Biketronics website says 8 ohms or 4 ohms. I would love to see this one on the amp dyno to see what impedance it works at and power, current draw etc.


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## Onyx1136 (Mar 15, 2009)

They look like standard xt60 connectors for power and ground. There's no reason why you can't buy a. Ew connector and make your own with larger gauge wire. Although, I'm not sure what the max wire size that those connectors will accommodate is. I would doubt that they'll even handle something as small as 8 gauge wire. But, as long as you keep the distance between the distribution block and the amp really short, you might be ok.

It's odd that they actually make more power at 8 ohms than they do at 4 ohms. Something to do with the stator protection circuitry, I assume?


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## claydo (Oct 1, 2012)

Man, this thing would be awesome for some 8 ohm raw driver midbasses! Not quite the sub amp I was hoping tho.....


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## 2010hummerguy (Oct 7, 2009)

I was wrong, the 2360 is actually a bridged 4180 meant for Harley riders to blast special Hertz speakers designed for max SPL in harsh environments, like riding a Harley. This explains the weirdness of the outputs at 8 ohms vs. lower impedances. The 2250 should also price closer to the 2180, when it releases.

The 2250 is due out any day now; I am catching up with BT on Monday and will report back with any news.


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## 2010hummerguy (Oct 7, 2009)

I've been away from the forum for a while and realized I never followed up on the BT2250. It is now available from Biketronics: BT2250 - 250W RMS X 2 - Biketronics Inc

Still loving mine, it's going on 15k+ miles of heavy usage and never skipped a beat.


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## Heavy Metal (May 23, 2020)

In


Babs said:


> Awesome stuff!!
> 
> Man, I'd love to do a head-to-head with one of their 4's to something like a JL XD or my PDX's. Wouldn't that be the shiznit if they equaled or even bettered some 'namebrand' usual suspect reputable class-D's, being kinda apples to apples.
> 
> ...




I’m running a BT4180 and had a XT60 connector done with 8ga which is now my power wire to the amp cost time and wait and @$15 off eBay


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## NW JLUR (Dec 3, 2018)

There are also XT60 to xT90 adapters if there’s not enough room to solder 8ga onto the XT60


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