Definitive Technology (Def Tech) BP7006/BP7004/BP7002 - BP8954MOD

[Everett T]

I am unsure why I would want a high pass filter on the sub in these. I have a sub out feeding the amp that current has a low pass filter so the only thing I am sending the subs is 120hz or below.

I planned on buying two Dayton Audio DSPs and tune it with iWoofer but I though for sure it appears to be odd that without pushing them hard, I was getting radiator clapping. It’s possible that the cross over in these had some special stuff to make the two radiators work well in the cabinet but I’m still perplexed as to what the actual wattage wattage is.

HP filter is to protect the driver from over excursion. Personally I wouldn't over invest in powering those..

 

[Stu Pidasso]

In the OEM circuit, there is a limiter which begins to kick in at 28.28vrms and goes into full clamp mode at 77v peak - if the input voltage is higher than 2.9956vrms when using the RCA input. 28.28v rms into 4 ohms is 200 watts. There is a high pass filter at 24db per octave at 28.46hz, an EQ bump at 35hz Q-3, 8.465db, phase adjustment is also present. From 50hz to 150hz we have a shelf with a q of .784, D=1.2755, 4.771db. We also have a low pass filter at 150hz which is strange as it's 18db per octave.

 

[Everett T]

In the OEM circuit, there is a limiter which begins to kick in at 28.28vrms and goes into full clamp mode at 77v peak - if the input voltage is higher than 2.9956vrms when using the RCA input. 28.28v rms into 4 ohms is 200 watts. There is a high pass filter at 24db per octave at 28.46hz, an EQ bump at 35hz Q-3, 8.465db, phase adjustment is also present. From 50hz to 150hz we have a shelf with a q of .784, D=1.2755, 4.771db. We also have a low pass filter at 150hz which is strange as it's 18db per octave.

My guess at the HP was was basically the same frequency but never would have guessed the bump at 35. My guess on the LP is one the 5" woofers is passed off 1st order, but that's just a guess. Great info, thanks for sharing.

 

[kaminsbm]

Hello All, new here and also a new owner of 2 BP7006s. Thanks Stu for the schematic, here is the schematic of the 300W sub amp module. Surprised and thankful this thread is still active.

For my pair, they were not working when I bought them. One was too quiet, the other was silent. I found some bad caps, and replaced all the electrolytic capacitors on the boards (including the sub amp which had 2 non polarized caps), and also found/fixed at least one tin whisker under the hot glue, which was a short to -15V. These speakers were designed to be plugged in all the time, and were the early years of lead-free solder, so over years the power supply rails could grow whiskers to nearby pins with a different voltage.

Both amp boards seem to be working well. I will run mine on a triggered power strip so they only turn on when the main system is powered on - avoid future tin whiskers. Thanks for this post, and maybe this schematic is helpful to others.

 

[protohyp]

Hello All, new here and also a new owner of 2 BP7006s. Thanks Stu for the schematic, here is the schematic of the 300W sub amp module. Surprised and thankful this thread is still active.

For my pair, they were not working when I bought them. One was too quiet, the other was silent. I found some bad caps, and replaced all the electrolytic capacitors on the boards (including the sub amp which had 2 non polarized caps), and also found/fixed at least one tin whisker under the hot glue, which was a short to -15V. These speakers were designed to be plugged in all the time, and were the early years of lead-free solder, so over years the power supply rails could grow whiskers to nearby pins with a different voltage.

Both amp boards seem to be working well. I will run mine on a triggered power strip so they only turn on when the main system is powered on - avoid future tin whiskers. Thanks for this post, and maybe this schematic is helpful to others.

would you happen to have the specs on the Caps you replaced?

 

[kaminsbm]

I replaced using all radial leaded caps, while some on the board are aluminum surface mount style. Note that #8 is a non-polarized electrolytic for the sub amp module.
Mouser.com
1 RoHS15985-85-80V6800; 380LX682M080K052; 6800uF 80V SNAP CAP; 4; 6.950 27.80
2 RoHS1710-860080675015; 860080675015; WCAP-ATLI 220uF 50V; 4; 0.590 2.36
3 RoHS1667-EEU-FS1H270; EEU-FS1H270; 50VDC 27uF 5000H 5x1; 10; 0.282 2.82
4 RoHS1667-EEU-FR1H100; EEU-FR1H100; 50VDC 10uF 20% L/S=2; 12; 0.267 3.20
5 RoHS1667-EEU-FR1H4R7; EEU-FR1H4R7; 50VDC 4.7uF 20% L/S=; 2; 0.390 0.78
6 RoHS1232-200LLE4R7MEFC63X; 200LLE4R7MEFC6.3X11; LONG LIFE ELECTROLYT; 2; 0.560 1.12
7 RoHS1232-35YXF470MEFC10X2; 35YXF470MEFC10X20; LOW IMPEDANCE ELECTR; 2; 0.710 1.42
8 RoHS1598-106BPS100M; 106BPS100M; 10uF 100V 20%; 4; 0.740 2.96

 

[protohyp]

I replaced using all radial leaded caps, while some on the board are aluminum surface mount style. Note that #8 is a non-polarized electrolytic for the sub amp module.
Mouser.com
1 RoHS15985-85-80V6800; 380LX682M080K052; 6800uF 80V SNAP CAP; 4; 6.950 27.80
2 RoHS1710-860080675015; 860080675015; WCAP-ATLI 220uF 50V; 4; 0.590 2.36
3 RoHS1667-EEU-FS1H270; EEU-FS1H270; 50VDC 27uF 5000H 5x1; 10; 0.282 2.82
4 RoHS1667-EEU-FR1H100; EEU-FR1H100; 50VDC 10uF 20% L/S=2; 12; 0.267 3.20
5 RoHS1667-EEU-FR1H4R7; EEU-FR1H4R7; 50VDC 4.7uF 20% L/S=; 2; 0.390 0.78
6 RoHS1232-200LLE4R7MEFC63X; 200LLE4R7MEFC6.3X11; LONG LIFE ELECTROLYT; 2; 0.560 1.12
7 RoHS1232-35YXF470MEFC10X2; 35YXF470MEFC10X20; LOW IMPEDANCE ELECTR; 2; 0.710 1.42
8 RoHS1598-106BPS100M; 106BPS100M; 10uF 100V 20%; 4; 0.740 2.96

thank you very much. your symptoms wasn't humming was it? it was not functioning although you had the red power light?

 

[kaminsbm]

One was humming at one point, due to a bad filter cap on the + or - 15V. Before that it was not functioning, it had a tin whisker short on the board that I found and removed.

 

[Doodski]

One was humming at one point, due to a bad filter cap on the + or - 15V. Before that it was not functioning, it had a tin whisker short on the board that I found and removed.

Tin whiskers are a pain in the butt. I can't count the amount of PCB I've sprayed with isopropyl and then scrubbed thoroughly with a toothbrush and after the unit(s) worked fine. Not saying all of them where tin whiskers but some probably where.

NASA Goddard Tin Whisker Homepage

Photo Gallery: Parts with Tin Whiskers

 

[protohyp]

curious if you can re-weight the passive radiators to prevent clapping? I'm going to make an attempt at this using a different mono board. I guess I'd really have to treat these as woofers and not subwoofers to prevent bass cancellation with my actual subwoofers. maybe place them under my couch for some feeling.

 

[protohyp]

Hey Guys.

So I was able to bring my tower back to life without ANY ground noise. Does it sound as good as the original? its debatable.

So here is what I did.

I ordered a TDA8954TH Large Power Digital Audio Amplifier Board A+D Class 420W Amp AC 24V from eBay. You can search it. They're pretty well made except that some of the caps needed to be resoldered but I think thats to be expected coming from China. It runs off 24-0-24 AC so its a perfect match for the transformer.

Then I ordered a 2.1 Preamp module with phase switch and frequency and volume controls on amazon. You can run it either AC or DC

Here is where I think I may have solved the ground loop problem. Basically I took the HI/LO input board off a DT Supercube iii that had blown up on me and used that as my input to the preamp board so I'm not using LFE for the signal. I think these BP models weren't really designed for sub frequencies anyway. The HI/LO board is passive so no need to power it but my guess is you can use any Line Converter to bring the signal into the Pre-amp.

So again I'm sort of new to this so please tell me if I'm going to burn down the house and I've done this semi correctly. I figure this is what the preamp/amp board on the original amp was doing anyway so I rebuilt it the same way. To my ears it sounds great and if it comes close to busting out the radiators I just dial down on the pre amp controls to hit the sweet spot. But beyond that absolutely NO ground noise. I'll see if I can get some pictures of the layout.

​

 

[protohyp]

I also decided to turn them into atmos speakers.

 

[beagleman]

no worries, i respect your opinion on the matter. my opinion is that all of what you are talking about is likely bypassed when using the RCA-in. anyway, i dont have the speakers anymore to provide some tests and measurements, nor did i ever have a working amp. so i'd have to rely on someone willing to give it a shot. until then, you hold your opinion, i hold mine. its ok. you are welcome to provide some measurements and proof of yours and i'd be happy to change mine



congrats bud, glad i could help

as for the crossover freq, if you have a mic and rew, run a sweep with just the upper array connection, it should be fairly obvious when it rolls off. or even use your phone with an SPL app. again only the upper array, play 200hz, note the reading, play 190hz, note...etc all the way down to like 80hz. while it may not be accurate in terms of actual SPL, it will be relative to one another, so it will work just fine for this use case. you'll then be able to see where it rolls off. when you've reached a -3 to -5db, should give you a good enough indicator what the crossover point should be

once you set it, you can then flip the phase back and forth and see which one gives you the better reading on the mic as well

You are actually wrong. (not trying to just argue, but I reviewed the schematics and dealt with this speaker first hand)
This is a VERY typical circuitry used in most all Retail subwoofer amps, and powered tower "Subs".
The Deep Bass EQ, is very commonly used due to the Small box size causing low frequency "Roll off".

The EQ, High Pass filter and limiting and so on that Stu mentions are used in the amp, and both inputs go to the amp.
Speaker level inputs, go to the SAME amp and same circuits that the RCA inputs go to.

Picture a "Y" letter, and both inputs go into the top, RCA and Speaker, the bottom of the "Y" is into the amp.

The only difference, speaker level inputs change the impedance, to get to the same ideal impedance of the RCA inputs.

 

[beagleman]

I think you may be missing the point. Look at the schematic and you'll understand what's going on. The LF filter is simply tuning the woofer in it's enclosure for the designers desired response when mated with the upper speaker drivers. These woofers are NOT subwoofers. They are bass drivers and do not begin to cover proper LFE spectrum response.

Agree! Super common "Sub" amp design. All brands use a very similar design.

Some Velodynes I measured do all this also, but with simply different figures for the low frequency "Boost"
My one Velodyne was +6.5 db at 32Hz

With a normal amp, sure it will work, sure it will have bass, but it will be lacking a good bit in the bottom octave.

I have done the exact thing he mentions, (but with a stand alone shelf mounted amp) and while you do get a working speaker, the bass roll off is quite different and Deep bass lacks noticeably compared to the stock built in amp.

The best "Fix" I found that keeps a similar bass response was a Dayton audio sub amp with a selectable 6db boost at 35Hz. Not quite stock sound, but close enough IMHO
Close to ideal sound wise, but not dimensions wise.

Home

Dayton Audio SPA250 250 Watt Subwoofer Plate AmplifierDayton Audio SPA250 250 Watt Subwoofer Plate AmplifierEngineered to provide flexibility, ample power, and reliabilityThe Dayton Audio SPA250 subwoofer amplifier produces 250 watts of clean power output, and combines with a host of flexible...

www.parts-express.com

 

[beagleman]

curious if you can re-weight the passive radiators to prevent clapping? I'm going to make an attempt at this using a different mono board. I guess I'd really have to treat these as woofers and not subwoofers to prevent bass cancellation with my actual subwoofers. maybe place them under my couch for some feeling.

Combo of Two things most likely.

1. No high pass filter on your amp. Therefore letting bass frequencies below the tuning frequency over excursion drivers and passives.

2. Simply running it too loudly overall. These are not a high powered party speaker exactly.

Your comment about preventing bass cancellation with your "actual" subwoofers, not sure what you mean honestly.

The Towers are actual subs, not the biggest or most high output but should go well into the upper 20s Hertz bass wise easily, IF using the stock high pass and bass eq built into the stock amp design.

 

[protohyp]

Combo of Two things most likely.

1. No high pass filter on your amp. Therefore letting bass frequencies below the tuning frequency over excursion drivers and passives.

2. Simply running it too loudly overall. These are not a high powered party speaker exactly.

Your comment about preventing bass cancellation with your "actual" subwoofers, not sure what you mean honestly.

The Towers are actual subs, not the biggest or most high output but should go well into the upper 20s Hertz bass wise easily, IF using the stock high pass and bass eq built into the stock amp design.

I think what everyone was doing was bypassing everything from the amp and letting the signal from the receiver for Left and Right go directly to the crossovers for the highs and mid's. Thats what I did.

I then got a Class D amp board and put a cheap sub preamp to cover the woofer. It actually sounds pretty good. Since I can control the volume as well as the frequency I'm not getting any clap from the radiators.

What I meant about bass cancellation is that Towers sit right next to my 12" dedicated subwoofers for the entire system running off LFE. Mind you I haven't run room correction yet nor sub walk because I built the boxes myself and they're HUGE so they should just stay where they are.

I'm a newb at theater setup so my focus really has been trying to get the towers up and running because when they were working they sounded amazing

 

[datrumole]

You are actually wrong. (not trying to just argue, but I reviewed the schematics and dealt with this speaker first hand)
This is a VERY typical circuitry used in most all Retail subwoofer amps, and powered tower "Subs".
The Deep Bass EQ, is very commonly used due to the Small box size causing low frequency "Roll off".

The EQ, High Pass filter and limiting and so on that Stu mentions are used in the amp, and both inputs go to the amp.
Speaker level inputs, go to the SAME amp and same circuits that the RCA inputs go to.

Picture a "Y" letter, and both inputs go into the top, RCA and Speaker, the bottom of the "Y" is into the amp.

The only difference, speaker level inputs change the impedance, to get to the same ideal impedance of the RCA inputs.

yeah, just went back and reviewed all the details @Stu Pidasso provided

so if this is accurate, then doing LFE is the worst possible way to use these speakers with their stock board it seems?

the 'woofer' on spkr level input have a LPF at 180hz to blend better with the upper array, however LFE never really contains over 120hz, and often ARVs have another LPF at 120hz, wouldnt that then put the 'woofer' out of phase? and also create a dip in the speaker from 120-180 on using spkr vs LFE input since LFE doesnt contain that frequency range?

on the other side, i suppose we dont have to worry about the subsonic filter at 20hz since there is no real chance of any of these drivers hitting that low. however, i do believe avrs have a subsonic filter at or around 20hz, which would then again be a double filter potentially affecting phase?

lastly, with the mod, there is a likely chance your respective avr's room correction would account for the now missing EQ portions of the stock board, so i don't know if i'm totally worried there. heck, it's possible that with the stock board, that the AVR correction pulled those stock-pre-amp adjustments down, nullifying their existence. so them not being around post-mod seems lower on my list of concerns that stu mentioned

 

[MrGadget]

Glad this thread is still active. I inherited0 FOUR BP7006 units and one BP7002 unit. With some help from another forum (AVForums), I replaced the SMT caps in the ±15V power supply section, which eliminated the infamous hum. But one of the units exhibited additional / sporadic humming and scratchy noises. I nearly gave up, until the suggestion about "tin whiskers" convinced me to clean both PCBs better. I removed lots of old glue from around the U4 integrated circuit, and cleaned the entire DS300 Amp Board with a toothbrush and alcohol (after removing the heat sink). I used a toothpick to clean between the contacts of the integrated circuit, which were gummed up with old glue (which some have suggested might become conductive as it ages). Tried to be gentle since some of the PCB traces are very small and delicate. Sure enough, the noises stopped (fingers crossed).

Unfortunately, I'm having additional troubles with two of the units. On one, the bass level potentiometer raises/lowers the bass level only slightly. Even if I short circuit the pot to zero-resistance, the bass level is lower than the other speakers. Maybe there's a faulty Op Amp somewhere in the amplification pipeline. Or maybe "tin whiskers" or old/hardened (electrically-conductive?) glue are shorting something. I'll try cleaning its PCBs. On the other unit, the bass level jumps dramatically when the pot is turned slightly above minimum. I'll try some tuner cleaner on the pot. More to come on these problems.

Thanks to everyone for their thoughts and comments. I was on the verge of replacing the amps (the main topic of this thread), but the warning about losing the equalization boost (@35Hz) convinced me to keep trying to fix the original amps. Also, the cost of replacing the amps was easily over $100 per speaker since each required an amp board, a pre-amp (with volume & crossover adjustments), a Line Output Converter (to accept speaker-level inputs), and some harnesses, mounting hardware, and lots of work.

Even if I get these units all repaired, they're too "boom-y" for my taste. The bass isn't as tight and deep as my home-made subwoofer. Oddly, these Def Techs don't have a pot to adjust the crossover frequency. Maybe Datrumole is right about the crossover frequency being high to blend with the upper speakers ... higher than normal for a subwoofer (and hence someone's comment that these aren't really subwoofers, but rather just woofers). So, once the repairs are complete, maybe I can sell them to a local buyer (they're too big to ship), else maybe I'll donate them to my local Habitat-for-Humanity "ReStore". The wife gives me funny looks when she envisions me cluttering the house with four more tower speakers!

 

[datrumole]

Thanks to everyone for their thoughts and comments. I was on the verge of replacing the amps (the main topic of this thread), but the warning about losing the equalization boost (@35Hz) convinced me to keep trying to fix the original amps. Also, the cost of replacing the amps was easily over $100 per speaker since each required an amp board, a pre-amp (with volume & crossover adjustments), a Line Output Converter (to accept speaker-level inputs), and some harnesses, mounting hardware, and lots of work.

Even if I get these units all repaired, they're too "boom-y" for my taste. The bass isn't as tight and deep as my home-made subwoofer. Oddly, these Def Techs don't have a pot to adjust the crossover frequency. Maybe Datrumole is right about the crossover frequency being high to blend with the upper speakers ... higher than normal for a subwoofer (and hence someone's comment that these aren't really subwoofers, but rather just woofers). So, once the repairs are complete, maybe I can sell them to a local buyer (they're too big to ship), else maybe I'll donate them to my local Habitat-for-Humanity "ReStore". The wife gives me funny looks when she envisions me cluttering the house with four more tower speakers!

yeah, this thread/mod isn't a drop in replacement for what is there, it simply fills the gap cheaply to get the speakers in a usable state

if you were using the speaker level inputs, this was never meant to fix that input mechanism as it obviously doesnt address that ability

if you were using the LFE input, this should actually provide a potentially better solution TBH. the existing onboard input apparently has both a HP and LP filter, paired with the existing HP and LP filter on you AVR and likely introducing phase issues. also, using LFE doesnt have any info above 120hz, or at least its not supposed to, so you already created a gap to the upper array by simply using LFE. (the speaker level input crossed at 180hz)

however addressing the EQ on the existing board, it's very likely that the AVR room correction will potentially nullify it anyway. so even though it has a 35hz boost and a shelf filter, when the room correction gets to it, it will tweak it anyway. so it being there is inconsequential unless you were ever running them without room correction

so none of this is perfect, compromises will have to be made. perhaps adding a minidsp into this chain (depending on your equipment) could fill some of the gaps. pending you had pre-outs on your AVR, you could send LR to a minidsp, then the L1 and R1 to something like an A07, and L2 and R2 to this mod, and you can tweak at your hearts delight

finally, if you can find a buddy who is wood-handy, my Tarkus speakers absolutely destroy these speakers in every way. so if you are nearing 300ish dollars for this fix, new speakers are within reach

 

[bmfkai]

I'm about to give this mod a shot, when wiring it all back up there were 2 additional leads from the speaker RCA inputs that connected to the OEM amp. I'm assuming this is what you meant by losing the ability to power through just the speaker line inputs? So my configuration would have to be speaker line inputs plus LFE?