Dynaudio BM15 Passive Crossover

[JohnRoberts]

I beg to differ, in that cpas with different charcteristcs can alter the crossover behavior.

"Can" in extreme cases but rarely would. In the vast majority of cases a film cap will make an improvement in every aspect but BOM cost.

JR

 

[kags]

I agree that DSP is a good way to go. I like the Mini DSP idea, but for more turnkey solution, something like a DSP plate amplifier (with chassis) https://www.parts-express.com/Dayto...nel-with-DSP-and-Bluetooth-300-798?quantity=1

Or more DIY: https://www.parts-express.com/Dayto...uetooth-Amp-Board-with-DSP-325-434?quantity=1

Or even the Crown CDi DriveCore power amps (1 unit per speaker) could be configured as amps and DSP, but more expensive than the above solution.

 

[Cqwet Dbdfte]

BM15A and BM15 are totally different animals what comes to crossovers. The passive has 6db/oct filters whereas the active comes with
"1.7 kHz electronic crossover, 5th order phase aligned.
Instrumentation type balanced input section, with input
overload protection." as the user manual puts it.
You can dl service manual from
BM15A service manual

Instead of just swapping components of the passive crossover you might want to build the active crossover with or without the amps in BM15A. They give much steeper slope thus much narrower area in the output of the two drivers where the frequencies are overlapping and causing phase problems and hot spotting, meaning the FR changes when you move away from the sweet spot. So with steeper filters the sweet spot is wider. Also having overload protection is useful. Using DSP (MiniDSP and like) though makes things easier to control and adjust, even for some room eq.

Interesting amp. The output MOSFETS have gain, which is quite uncommon. The drivers for these also have gain. The linearity of MOSFETs is not an easy question, most FETs are designed for switching. Here mfg. specifies IR parts, now Vishay. Datasheet is a bit light on the transfer curve, the part from ST looks promising, after a few ampere idle current .

 

[JohnRoberts]

Interesting amp. The output MOSFETS have gain, which is quite uncommon. The drivers for these also have gain. The linearity of MOSFETs is not an easy question, most FETs are designed for switching. Here mfg. specifies IR parts, now Vishay. Datasheet is a bit light on the transfer curve, the part from ST looks promising, after a few ampere idle current .

The popular MOSFET power amps from back in the day used Lateral MOSFETs (Hitachi). Vertical MOSFETs are more commonly used as on/off switches. I've seen vertical MOSFETs tricked to play nice as compound devices.

JR

 

[RoadrunnerOZ]

Neve used Vertical DMOS Fets for channel direct out drivers in some of their consoles - BD522/512 - superseded by VN0106/VP0206

 

[kidb]

I agree that DSP is a good way to go. I like the Mini DSP idea, but for more turnkey solution, something like a DSP plate amplifier (with chassis) https://www.parts-express.com/Dayto...nel-with-DSP-and-Bluetooth-300-798?quantity=1

Or more DIY: https://www.parts-express.com/Dayto...uetooth-Amp-Board-with-DSP-325-434?quantity=1

Or even the Crown CDi DriveCore power amps (1 unit per speaker) could be configured as amps and DSP, but more expensive than the above solution.

This is a very attractive solution, dsp brings a lot of benefits passive XOs simply can't address. I might have to try that out at some point

 

[KrIVIUM2323]

"Can" in extreme cases but rarely would. In the vast majority of cases a film cap will make an improvement in every aspect but BOM cost.

JR

Sadly no improvement for sound, changing capacitor type from electro to film/foil will 99% of case change the expected results with too much 'brightness', less coherency,... and i know first hand as this is what started my journey into loudspeaker diy land.

This is well known from anyone which have dealt with this before ( and not making change to the pair without going by step modding only one loudspeaker then the other).

To the point i gave up with passive, invested in a serious loudspeaker management system and multiamp setup. No more passive components to deal with which is relief in this field.