No, you will get the diameter of the driver as baffle! (Cause everything around is absorbing -> like it's not there) This influences a lot.
So you need to take the bothersome step to cut a hole and get some tape at least ;-) or do it properly like @Bmsluite does now with a measurement baffle.
The software sometimes ***** up. I would estimate it freezes on average 2 times the day when I do a crossover development. You have to check if the parameters you set in the main window are saved, sometimes the input jumps to the old setting. I can not choose where to save files and can not load as in every other program on earth. Simply file loading doesn't work as it should, tested on 4 different computers over many versions. You can't save an EQ. You can't save and write a complete setup in the DSP, it takes very long to set up when you also use the EQ settings.
That's not enough to ditch the system cause it's a bunch of smaller things but it's annoying.
I wrote that regularly here - amp modules have a dynamic range of about 125dB(A) but with D/A converter it goes down to 114/116dB(A) (the 3rd HF channel has lower noise). With analog input even a little less.
That's still very good but a pity when you know the quality of the amp. But there are very little HiFi/Homecinema Systems out there which can achieve 115dB(A) S/N and in most use cases (living room and >2m distance) that's easy enough. But not in mine, I can still hear a little sizzle in a 3" midrange dome in 1m distance in a silent studio room.
Alright I'm back!
Calibrated spl at 2.83V coming out of the amplifier
I know its tilted but it was flush mounted for the measurement
Impulse is pretty awesome looking
|
Off axis is what I would have expected
I think I'm looking more towards a 500hz or higher cross with the distortion.
Calibrated spl at 2.83V coming out of the amplifier
I know its tilted but it was flush mounted for the measurement
Impulse is pretty awesome looking
|
Off axis is what I would have expected
I think I'm looking more towards a 500hz or higher cross with the distortion.
Yeah, over 10% THD at 100Hz at only 63dB and near 1% at 500Hz at 85 dB/1m is not too encouraging for a lower crossover point.
Response looks good 500-5kHz.
Is the SPL calibrated too? 85dBSpl sensitivity is pretty low for a dome midrange but going that low for a 2" is great! You have about 6dB fall off at the crossover frequency, 500Hz seem to be very usable.
But do a few measurements at higher level, you need to check how it behaves with more serious load.
But for the price ... a great driver!
But do a few measurements at higher level, you need to check how it behaves with more serious load.
But for the price ... a great driver!
Literally says "spl calibrated" in the post....
Yup, I notice that and I'm OK with it. Mid range's don't need super high sensitivity. They end up high with the other drivers crossing into them. Whatever I cross it with I will be taking normalized spl measurements of so that I get a better baseline accross the drivers spectrum
I don't even listen to music this loud so I'm not going to do that. I don't really care what it sounds like at 105db. Mid domes are never going to be SPL kings.
Mid domes are THE SPL kings!
I have measurements of the Bliesmas at 114dBSpl where they have THD around 1-2%. The 2 12" already showed significant power compression but not the 3". That's a big part of these main studio monitor sound and the reason why 3" domes hold their place in this application - this or horn speakers for main monitoring.
But not every use case needs this dynamics so it's great to have good sounding smaller variants.
When you want to know what your midrange is able to do without distortion of your transients and peaks - raise the level 😎
I didn't consider the transients. Good point. When I get another chance at work I'll run it high and see what happens.
the deep notch may just be a near field effect and typically goes away in a proper far field measurement.
There are potential issues with pushing larger mid domes hard, depending on crossover point and the other drivers complementing it.
The limits of the D7608 are roughly 105 dB crossed at 600 hz at min BW2. 2nd harmonic would be just over -35 dB down. That's about just over 2 percent THD with the majority being 2nd order. Much of the level restriction depends on the baffle size supporting the lower mid output.
If you want more output with lower HD, you'll need another mid running shaded, sharing the load. If you tie both mids into the crossover with a 6.8 - 10 ohm / 20 W resistor in series with each mid, then bypass the series R on the main mid with a cap large enough to linearize the upper mids, it will get you close enough to tweak it flat. You may need to vary each series R to get the lower mids right. You'll find a slightly smaller series R will be needed on the main mid.
Alot of older speaker applications suffer from these limitations simply due to a lack of crossover refinement, but sometimes also due to less durable materials. In the case of the D7608, you'll run into mechanical limits well before the electrical limits are reached.
@Bmsluite Optimally, you'll want to mount the D7608 inset of the baffle with a slight taper for several reasons. The slight horn loading will provide better directivity control matching that of the woofer at crossover, also improving lower mid output and being closer to the woofer's acoustic center. It doesnt have to be perfect, just smooth.
ATC and Bliesma are ready for way more SPL.
This are my measurements with 2x12" and one Bliesma M74A at different SPL. This is a SINE SWEEP at 114dBSpl (very little crest factor) and you get roughly 1% THD. The 1" tweeter is giving up way earlier so I stopped the measurement at 2kHz. While the 12" showed already massive compression at low frequencies there was not even half a dB of power compression for the 3" - they area easy capable of more and some peak power extra.
This are my measurements with 2x12" and one Bliesma M74A at different SPL. This is a SINE SWEEP at 114dBSpl (very little crest factor) and you get roughly 1% THD. The 1" tweeter is giving up way earlier so I stopped the measurement at 2kHz. While the 12" showed already massive compression at low frequencies there was not even half a dB of power compression for the 3" - they area easy capable of more and some peak power extra.
These are measurements of the PMC domes. They have a waveguide built into them
@IamJF
While the M74A is capable of those levels, its moving around too much for my tastes. This is why I chose to use 2 of them per side shaded, even though implementation becomes more difficult to get good vertical polars with softer filter slopes.
Most of you know my stance on driver implementation regarding maximum output potential. I believe each driver should be able to do at least 110 dB under 1% THD in its designated range. Thats a tall order but I'm a firm believer in a good speaker being able to play individual notes as loudly (or close to it) as the complete system's output capability. This removes concerns of crest factor and other little details coming into play.
Anyways, currently for my system I'm looking at 3 LF drivers to choose from used in dual configuration - SB34NRXL, Eminence KL3012LF and CB3010N-8. I'm going to pick the one with the least junk in its CSD and lowest HD up to 800 hz (for filter overlap). They're surprisingly close to each other, with the SB34NRXL having a slight edge (so far).
While the M74A is capable of those levels, its moving around too much for my tastes. This is why I chose to use 2 of them per side shaded, even though implementation becomes more difficult to get good vertical polars with softer filter slopes.
Most of you know my stance on driver implementation regarding maximum output potential. I believe each driver should be able to do at least 110 dB under 1% THD in its designated range. Thats a tall order but I'm a firm believer in a good speaker being able to play individual notes as loudly (or close to it) as the complete system's output capability. This removes concerns of crest factor and other little details coming into play.
Anyways, currently for my system I'm looking at 3 LF drivers to choose from used in dual configuration - SB34NRXL, Eminence KL3012LF and CB3010N-8. I'm going to pick the one with the least junk in its CSD and lowest HD up to 800 hz (for filter overlap). They're surprisingly close to each other, with the SB34NRXL having a slight edge (so far).
Last edited:
@IamJF The HD in the low end is completely fine for my needs based on your sweep with a pair of the SB34NRXL if used with a sub. I'm going to use an 18" per side crossed at 60 - 70 hz below the main LF drivers.
As for the mid distortion, that's a close call for me. I'd like to see lower numbers closer to the MF crossover area (500 hz +). I believe dual M74As will get me there with some careful implementation to avoid vertical issues. I'm still simming this scenario.
As for the mid distortion, that's a close call for me. I'd like to see lower numbers closer to the MF crossover area (500 hz +). I believe dual M74As will get me there with some careful implementation to avoid vertical issues. I'm still simming this scenario.
And BTW, I agree with most here regarding a practical measurement distance of 30 cm to get reliable measurements without much room interference. Same goes for distortion (past a certain range).
The speaker was positioned close to a wall, not complete free standing. But the 12" perform very well, it will be hard to get something better. Maybe the lower sensitivity PHL 12" when you add a sub. THD between 400Hz and 800Hz is mainly H2. And it looks way worse as it is cause of the insane THD levels from 1kHz to 6kHz.
What do you use as tweeter? With your SPL requirements a 1" doesn't cut it I would say?
p.s: I have a pair of M74T on my table and it seems the suspension is a little harder? Membrane weight is also higher when I remember right. Will do measurements probably next week.