Opinions please:
I have 4 SB Acoustics SB15NRXC30-8 5.5" midwoofers and 2 Seas 27TDFC tweeters to play with.
Time and money are both short.
I have already built a 2-Way sealed monitor using a single midwoofer/tweeter per side. SQ is excellent but output is very low and a little worrying for how hard it is pushing my amplifier.
Impedance is probably about 9-10 ohms above the impedance peak of the woofer.
Designed environment is my new flat, main room about 3.5*7.5*2.5m
Am keen on sealed enclosures for many reasons:
No need to worry about tuning correctly for room
Faster lower distortion on bass
Less bass to travel through walls (I think, would like opinions on that)
Questions as follows:
Will an LCR bypass across the resonance peak of the woofer help open up the amp, will it kill my bass response? I'm wondering if the peak on top of the high impedance is just hard work?
Could it just be that the amp wasn't the best for high impedance loads? (was a Denon AVC A1D 5*150WPC design, previously ran many many high and low end speakers without issue)
Alternatively I could switch to a TMM design (MTM is less likely solely for aesthetic reasons), that would be a sealed floor standing unit.
Raises the following questions:
According to PCD 7 two parallel woofers will greatly increase bass response, is this right? (dB gain below 100Hz seems to be higher than that above)
The obvious design questions are raised regarding balancing response and impedance, and the two woofers are theoretically more efficient than the tweeter. This has been solved with thin-wired inductors and a 4th order electrical crossover. Images of sim attached.
Also, I tried a 4th order electrical on the sealed 2-way but was very unhappy with the results, sound was just... bad (so probably need to re-measure impedance of drivers in enclosure as was working from manufacturer data for that) but this doesn't fill me with confidence for a floor stander...
If I go floor standing crossover costs will be lower, impedance lower, sensitivity higher, xo at 2kHz.
Stay on 2-ways and I'm basically at the finishing gates but unhappy with the sensitivity or performance unless using a 2nd order xo, which sounds bad at high levels due to the peaks in the midwoofer's higher response, and the tweeter is being pushed quite hard due to the 2nd order slope at 1.5kHz...
I have 4 SB Acoustics SB15NRXC30-8 5.5" midwoofers and 2 Seas 27TDFC tweeters to play with.
Time and money are both short.
I have already built a 2-Way sealed monitor using a single midwoofer/tweeter per side. SQ is excellent but output is very low and a little worrying for how hard it is pushing my amplifier.
Impedance is probably about 9-10 ohms above the impedance peak of the woofer.
Designed environment is my new flat, main room about 3.5*7.5*2.5m
Am keen on sealed enclosures for many reasons:
No need to worry about tuning correctly for room
Faster lower distortion on bass
Less bass to travel through walls (I think, would like opinions on that)
Questions as follows:
Will an LCR bypass across the resonance peak of the woofer help open up the amp, will it kill my bass response? I'm wondering if the peak on top of the high impedance is just hard work?
Could it just be that the amp wasn't the best for high impedance loads? (was a Denon AVC A1D 5*150WPC design, previously ran many many high and low end speakers without issue)
Alternatively I could switch to a TMM design (MTM is less likely solely for aesthetic reasons), that would be a sealed floor standing unit.
Raises the following questions:
According to PCD 7 two parallel woofers will greatly increase bass response, is this right? (dB gain below 100Hz seems to be higher than that above)
The obvious design questions are raised regarding balancing response and impedance, and the two woofers are theoretically more efficient than the tweeter. This has been solved with thin-wired inductors and a 4th order electrical crossover. Images of sim attached.
Also, I tried a 4th order electrical on the sealed 2-way but was very unhappy with the results, sound was just... bad (so probably need to re-measure impedance of drivers in enclosure as was working from manufacturer data for that) but this doesn't fill me with confidence for a floor stander...
If I go floor standing crossover costs will be lower, impedance lower, sensitivity higher, xo at 2kHz.
Stay on 2-ways and I'm basically at the finishing gates but unhappy with the sensitivity or performance unless using a 2nd order xo, which sounds bad at high levels due to the peaks in the midwoofer's higher response, and the tweeter is being pushed quite hard due to the 2nd order slope at 1.5kHz...
Attachments
With your current speakers why are you concerned about "how hard it is pushing my amplifier"? Is it because you have the volume knob turned up higher than in your old room? An impedance correction circuit probably won't make an audible difference with a low output impedance solid state amp.
Your new room is a bit big for a single 5" woofer, so your dual woofer idea is a good one. Ruling out an MTM means you should go with a 2.5 way - rolling off the bottom woofer at baffle step frequency.
Speaking of baffle step compensation (BSC), that's why you want to have the raw midwoofer sensitivity a bit higher than your tweeter. Theoretically you need 6 dB more midwoofer sensitivity to provide full baffle step compensation for speakers that will be placed well out in the room. As you get closer to the walls you get some lift and can use less BSC. Your SBs in parallel will allow you to design in 4 dB of BSC if you don't use small gauge coils, etc. to reduce their output. Don't waste it, use the extra sensitivity for baffle step compensation.
As for ported vs. sealed, you will lose almost all bass if you go sealed with those SBs. from Madisound:
So yes, you won't have bass going through the walls because there won't be any, unless you cross to a sub at 120 Hz or higher, but that's not a general characteristic of all sealed boxes. It's a matter of the driver's characteristics.
At the risk of starting a flame war, I don't think bass can be "Fast". I think the term is generally used to describe well damped systems that might be more accurately described as tight(ly controlled). In a highly damped system the output will stop faster than a more resonant one, maybe that's where the "fast bass" comes from.
Whatever you call it, I prefer the sound of sealed boxes when using appropriate drivers to vented. However, the drivers you have call for ported enclosures if you want to get any bass at all.
Your new room is a bit big for a single 5" woofer, so your dual woofer idea is a good one. Ruling out an MTM means you should go with a 2.5 way - rolling off the bottom woofer at baffle step frequency.
Speaking of baffle step compensation (BSC), that's why you want to have the raw midwoofer sensitivity a bit higher than your tweeter. Theoretically you need 6 dB more midwoofer sensitivity to provide full baffle step compensation for speakers that will be placed well out in the room. As you get closer to the walls you get some lift and can use less BSC. Your SBs in parallel will allow you to design in 4 dB of BSC if you don't use small gauge coils, etc. to reduce their output. Don't waste it, use the extra sensitivity for baffle step compensation.
As for ported vs. sealed, you will lose almost all bass if you go sealed with those SBs. from Madisound:
So yes, you won't have bass going through the walls because there won't be any, unless you cross to a sub at 120 Hz or higher, but that's not a general characteristic of all sealed boxes. It's a matter of the driver's characteristics.
At the risk of starting a flame war, I don't think bass can be "Fast". I think the term is generally used to describe well damped systems that might be more accurately described as tight(ly controlled). In a highly damped system the output will stop faster than a more resonant one, maybe that's where the "fast bass" comes from.
Whatever you call it, I prefer the sound of sealed boxes when using appropriate drivers to vented. However, the drivers you have call for ported enclosures if you want to get any bass at all.
TMM has to be a 2.5 way, i.e. the lower woofer needs to be rolled off at around the baffle step frequency, while the upper woofer goes up to the crossover frequency. Remember that a 2.5 way is a full baffle step design.
If you want both woofers summed at every frequency up to the crossover point to the tweeter you have to resort to a MTM because of the C-C involved (both woofer need to be close to the tweeter).
No. Driving two drivers in parallel has a gain of maximum 6dB for every frequency.
Frankly, you shouldn't have any problem in crossing both drivers at around 2KHz with a LR4 acoustic slope - usually with a 2nd order electrical on the woofer and 3rd order electrical on the tweeter. For your bigger room I'd opt for either TMM or MTM, for the gain in sensitivity. Only if you do a baffle step compensation of less than 3dB you'll end up with the woofers more sensitive than the tweeter.
As said by BobEllis, your woofers are meant for a vented enclosure, in no way you could produce bass from those in a sealed box. With two drivers a box of 20-25 L with a 40Hz tuning should provide a good bass that blends easily with the room. If you want the BBC trick (a peak in the 80Hz, so the speaker sounds to have more bass than it really has), then a 15 L with a 50Hz tuning is OK.
This is definitely not true. The bass wrap around the baffle and goes everywhere (full 4PI).
Ralf
You have bought small midwoofers that are designed for ported boxes rather than sealed boxes. A 20 l standard ported box will give you an f3 of 50 Hz with a modest maximum SPL. A stuffed sealed box of 11 l will give you an f3 of a bit below 90 Hz but the maximum SPL below 100 Hz will be significantly limited. With no subwoofer, tiny drivers and a room of significant size there would seem to be little option but to use the output from ports to maintain some output below 100 Hz.
If you want a sealed speaker with bass then you need cone area. Two 5" midwoofers have the efficiency for a midrange and the ability to work down to 200 Hz or so giving flexibility. Of course, there will obviously be significant additional costs associated with suitable woofers and crossover components for woofers so it may not be an option.
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