Out of interest, where did you get the Volt files from? The manufacturer FR graph seems to show baffle step - whereas the one you provided is more or less "flat" from 100Hz and up.
i.e. manufacturer @ 100Hz = 87dB and climbs to 500 Hz. Whereas your data file has 100Hz = 91dB and is more or less flat upwards in frequency from there.
I'm just trying to work out a net system target sensitivity. I'm thinking 85dB would be good here and provide ~ 3 dB of baffle step compensation.
i.e. manufacturer @ 100Hz = 87dB and climbs to 500 Hz. Whereas your data file has 100Hz = 91dB and is more or less flat upwards in frequency from there.
I'm just trying to work out a net system target sensitivity. I'm thinking 85dB would be good here and provide ~ 3 dB of baffle step compensation.
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Here's a "quick and dirty sim" using your data, my seas 27tbfc/g using Steve's crossover.
Caveats:
This is the raw data files for both drivers - your baffle and driver position has not been factored
I'm not confident the Volt data you provided is correct (based on my comment above). i.e. the output should be less at 100Hz given manufacturer data
I guessed a driver offset of 1.8" for the volt
I have assumed the phase data is correct.
Analysis:
Tuning needed if an LR target is desired - not a very good reverse null
The 27tbfc/g has a rising response. Conventional L-Pad should help here
the 2KHz hump needs work - caused by the Volt driver. This may not be present (i.e. remember this isn't simmed using your baffle), but if it is present, this will be audible and needs fixing.
Caveats:
This is the raw data files for both drivers - your baffle and driver position has not been factored
I'm not confident the Volt data you provided is correct (based on my comment above). i.e. the output should be less at 100Hz given manufacturer data
I guessed a driver offset of 1.8" for the volt
I have assumed the phase data is correct.
Analysis:
Tuning needed if an LR target is desired - not a very good reverse null
The 27tbfc/g has a rising response. Conventional L-Pad should help here
the 2KHz hump needs work - caused by the Volt driver. This may not be present (i.e. remember this isn't simmed using your baffle), but if it is present, this will be audible and needs fixing.
Attachments
That explains it - I was looking at the wrong driver - lol
This one?
Volt Loudspeakers | B220.2 (8″)
This one?
Volt Loudspeakers | B220.2 (8″)
Now I'm really confused. We seem to have 3 flavours
1. The BM220.2
Volt Loudspeakers | B220.2 (8″)
2. The BM228.8
Volt Loudspeakers | BM228.8 (8″)
3. The BM220.8 PDF you posted in your last reply is no where on the website and has a different dustcap size / profile.
Can you please confirm which driver you are planning to use out of #1, #2 and #3 above?
It's a BM220.8, isn't it? An old driver.
I got something just like your result with the SPL trace of the driver. But it might just be measured in a middling box. That seems to get something I can tie in with the 2mH/4.7uF kit value.
Which I don't like much, as it goes. This is a high inductance woofer, and you usually need some resistance in the bass shunt.
That's about there, I reckon. 1.5mH bass coil and a 0.15mH tweeter shunt. The 0.33mH could disappear altogether, or be upped to about 0.5mH with little real difference. Should work for a 91dB tweeter. It's the old third order Celestion tweeter filter really. Personally I'd wire it up and have a listen. We don't have a better idea.
I got something just like your result with the SPL trace of the driver. But it might just be measured in a middling box. That seems to get something I can tie in with the 2mH/4.7uF kit value.
Which I don't like much, as it goes. This is a high inductance woofer, and you usually need some resistance in the bass shunt.
That's about there, I reckon. 1.5mH bass coil and a 0.15mH tweeter shunt. The 0.33mH could disappear altogether, or be upped to about 0.5mH with little real difference. Should work for a 91dB tweeter. It's the old third order Celestion tweeter filter really. Personally I'd wire it up and have a listen. We don't have a better idea.
I have improvements I'd like to make. Firstly in the modelled on axis response. I can apply appropriate baffle diffraction and step to get a much better idea of any peaks and troughs to work those in. I can't sim off axis sadly. I forgot to post up system impedance too.
Nigel - are you planning on using a nominal 8, 6 or 4 ohm stable amplifier with these?
Nigel - are you planning on using a nominal 8, 6 or 4 ohm stable amplifier with these?
I haven't done any of the things I said, but here's a quick tune of Steve's crossover.
Lowered the crossover point slightly (~ 2,500Hz). I know Steve hates lower crossover points, but I think with an 8" driver beaming may cause some dips here off-axis as we are asking that 8" driver to play up quite high.
Impedance is a healthy min 6.0 ohms throughout.
Lowered the crossover point slightly (~ 2,500Hz). I know Steve hates lower crossover points, but I think with an 8" driver beaming may cause some dips here off-axis as we are asking that 8" driver to play up quite high.
Impedance is a healthy min 6.0 ohms throughout.
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Isn't this all just getting a bit confused? 8 ohm amps, MTM, reverse nulls, I just don't care.
All we are after is a simple bass circuit that will get this 91dB bass working. Seems like all that is different is it rolls off a bit more at crossover than a paper cone. Also bass heavy in the high inductance driver.
I'm feeling happy with what I am seeing here. All makes sense. Needs a loud 91dB tweeter to play nicely, but the basic electrical rolloff looks good. Which means it sounds good.
This below seems a good point of departure. That's 35L of 40Hz tuned reflex. Coils, of course, are easy to unwind for lesser values. We can go into all that. Box could have a removeable baffle for maximum flexibility. The old "cracked bell". See how it goes would be my approach.
All we are after is a simple bass circuit that will get this 91dB bass working. Seems like all that is different is it rolls off a bit more at crossover than a paper cone. Also bass heavy in the high inductance driver.
I'm feeling happy with what I am seeing here. All makes sense. Needs a loud 91dB tweeter to play nicely, but the basic electrical rolloff looks good. Which means it sounds good.
This below seems a good point of departure. That's 35L of 40Hz tuned reflex. Coils, of course, are easy to unwind for lesser values. We can go into all that. Box could have a removeable baffle for maximum flexibility. The old "cracked bell". See how it goes would be my approach.
Attachments
Isn't this all just getting a bit confused? 8 ohm amps, MTM, reverse nulls, I just don't care.
All we are after is a simple bass circuit that will get this 91dB bass working. Seems like all that is different is it rolls off a bit more at crossover than a paper cone. Also bass heavy in the high inductance driver.
I'm feeling happy with what I am seeing here. All makes sense. Needs a loud 91dB tweeter to play nicely, but the basic electrical rolloff looks good. Which means it sounds good.
This below seems a good point of departure. That's 35L of 40Hz tuned reflex. Coils, of course, are easy to unwind for lesser values. We can go into all that. Box could have a removeable baffle for maximum flexibility. The old "cracked bell". See how it goes would be my approach.
Hi Steve, the baffle will be removable and the box will be 35L. i intend to use a seas H1212 tweeter which as you know is 91.5db. this gives me a starting point and I am grateful. if ever you visit Birmingham give me a shout and I will buy you a beer. That goes for you too Dave.
Although I've got four 8" Drivers I'm going MT and will be building two Pairs of speakers.
Isn't this all just getting a bit confused? 8 ohm amps, MTM, reverse nulls, I just don't care.
Oh yes you do you big softy
Nigel had originally said 4 woofers and I had remembered something about MTM - so was just cautioning ... as this would change the crossover considerably as you know.
Your 8 ohm amp (assuming solid state due to impedance change) will have no problem driving these.
If these drivers have been customised to suit an OEM speaker maker, then there could be subtle differences that if you want to optimise will require measurement. When I say optimise, we may be only talking a few % different. Would you be able to hear the difference? Hard to say.
But - you have to get seriously into the hobby if you are going to start doing that. Not that it is hard, but requires reasonable gear being:
1. Measurement PC with hard wired / on board sound card (don't bother with USB devices if you want actual measured phase as I find the timing is all over the place with a USB device)
2. Measurement mic (condenser type)
3. Mic pre-amp - with +15 - +48 v phantom power (depending on mic requirements)
4. XLR cabling (mic - pre-amp for noise elimination). I run a 10 metre cable and no problem
5. Software - a few free options
6. Jig - so you can switch between loopback (calibration), impedance and acoustic measurements (FR, distortion etc...)
Oi Vey, microphone, schmicrophone! This, who needs?
I can't be turning my little apartment into speaker workshop. Wires and tools everywhere. I have to live here!
No. No. Simple speaker. Nothing hard about it. All been done before.
Well, actually, this is clever, IMO:
My current bit of fun.
I have a couple of 8" speakers. Different bass filters but same acoustic response, pretty much the same tweeter filter. Model it till you're blue in the face, if you end up with 1.5mH coil and 4.7uF, that's it.
I was unwinding coils this weekend. Not hard. Take about 20 turns off a 100 turn 0.22mH and you get 0.15mH. It's a square root relationship. Because higher the tweeter crossover, higher order the filter, better it sounds, IMO.
I can't be turning my little apartment into speaker workshop. Wires and tools everywhere. I have to live here!
No. No. Simple speaker. Nothing hard about it. All been done before.
Well, actually, this is clever, IMO:
My current bit of fun.
I have a couple of 8" speakers. Different bass filters but same acoustic response, pretty much the same tweeter filter. Model it till you're blue in the face, if you end up with 1.5mH coil and 4.7uF, that's it.
I was unwinding coils this weekend. Not hard. Take about 20 turns off a 100 turn 0.22mH and you get 0.15mH. It's a square root relationship. Because higher the tweeter crossover, higher order the filter, better it sounds, IMO.
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