Hi,
I need to bring down the level of the tweeter & the mids in an MTMW config. For the mids should the imp. be considered as 4 or 8 ohms (nominal, for arguments sake) when designing a Zobel, since there are 2 units.
Will the sensitivity of the mids be 91 db ?
Cheers,
sunil
I need to bring down the level of the tweeter & the mids in an MTMW config. For the mids should the imp. be considered as 4 or 8 ohms (nominal, for arguments sake) when designing a Zobel, since there are 2 units.
Will the sensitivity of the mids be 91 db ?
Cheers,
sunil
Sorry, I meant to say L-pad, not Zobel. I want to smoothen the impedance, so, do I need to consider the value as 8 or 4 (hypothetical) in a MTM config.
In an MTM where the tweeter is 91 db & mids are 88 db each, will paralleling them give a sensitivity of 91 db.
In an MTM where the tweeter is 91 db & mids are 88 db each, will paralleling them give a sensitivity of 91 db.
Sunil said:
Damn good question. And I'm talking about a Zobel here. Since the zobel is before the two drivers and if they're in parallel they'll present (for 2 x 8ohm drivers) a 4ohm load to the amp, then the zobel network must be calculated for a 4 ohm load? Huh?
Mos
Damn good question. And I'm talking about a Zobel here. Since the zobel is before the two drivers and if they're in parallel they'll present (for 2 x 8ohm drivers) a 4ohm load to the amp, then the zobel network must be calculated for a 4 ohm load? Huh?
Mos
Sunil,
When you put two 88dB mids in parallel, your theoretical sensitivity increases to 94dB, a gain of 6dB. As Mos said, use 4 ohms when you calculate values for your zobel.
When you put two 88dB mids in parallel, your theoretical sensitivity increases to 94dB, a gain of 6dB. As Mos said, use 4 ohms when you calculate values for your zobel.
I'm confused here. If there is a gain of 6db how much should I attenuate the mids because my tweeter is 91db
Tweeter: XT25 - 91 db
Mids: P13WH - 88 db x 2= 94 db
Would it be an attenuation of 3 db ?
I always thought that putting it this way would match up the mids with the tweeters.
Tweeter: XT25 - 91 db
Mids: P13WH - 88 db x 2= 94 db
Would it be an attenuation of 3 db ?
I always thought that putting it this way would match up the mids with the tweeters.
Sunil,
As I said...the theoretical gain is 6dB. It may not be quite that in actuality. There are a couple of things you need to keep in mind as you proceed with your speaker. The first is that in many cases, a speaker sounds more natural when the tweeter is a bit less sensitive than the mid/woofer, so given the theoretical numbers, I would say that depending on your taste, you probably won't need to pad the mids down a full 3 dB.
Secondly, in a three way, you will likely experience some gain in the mids due to the woofer and tweeter overlap into the midrange depending on your crossover choice. This will need to be compensated for by using a high DCR coil and/or a series resistor on the mid.
As I said...the theoretical gain is 6dB. It may not be quite that in actuality. There are a couple of things you need to keep in mind as you proceed with your speaker. The first is that in many cases, a speaker sounds more natural when the tweeter is a bit less sensitive than the mid/woofer, so given the theoretical numbers, I would say that depending on your taste, you probably won't need to pad the mids down a full 3 dB.
Secondly, in a three way, you will likely experience some gain in the mids due to the woofer and tweeter overlap into the midrange depending on your crossover choice. This will need to be compensated for by using a high DCR coil and/or a series resistor on the mid.
Delwon,
The Mids to Woofer crossover will be active. I'm not considering the rolloff & am just going for a 4th order.
Correct me if I'm wrong but the series resistor brings the level down, right. I'm thinking of using an L-pad (a series/parallel resistor). What does the "high DCR coil" do ?
The woofer is a P21WO from Vifa, spec'd at 88db.
Since I have no way to test & measure the drivers, I'm going totally by theory & the spec sheets provided by the vendor.
What do you think it'll sound like with the MTM at 91db approx & the Woofer at 88db ? I'm not looking at massive amounts of low bass since I have a smallish room.
STRANGE !
The Mids to Woofer crossover will be active. I'm not considering the rolloff & am just going for a 4th order.
Correct me if I'm wrong but the series resistor brings the level down, right. I'm thinking of using an L-pad (a series/parallel resistor). What does the "high DCR coil" do ?
The woofer is a P21WO from Vifa, spec'd at 88db.
Since I have no way to test & measure the drivers, I'm going totally by theory & the spec sheets provided by the vendor.
What do you think it'll sound like with the MTM at 91db approx & the Woofer at 88db ? I'm not looking at massive amounts of low bass since I have a smallish room.
STRANGE !
Sunil,
I don't have measuring capability either except for an RS spl meter so don't feel too badly! Anyway...you're right, the series resistor would bring down the level of the mids. A high DCR coil is sometimes used in order to avoid use of that series resistor. Of course, my elementary understanding of active xovers would tell me that should you decide that you need to pad down the mids, you will have to add some resistance.
With respect to the difference in sensitivity between the mids and woofer, there are a couple of possible scenarios. I don't know whether or not you plan to put a high pass on the mids, but if you don't plan to do so, your speaker will in effect be a 2.5 way in which case the woofer will act as compensation of sorts for baffle step.
If you are going to high pass the mids and you plan on ending up with 91dB for the mids and 88dB for the bass...depending on where you plan to cross them, it might sound okay particularly since you say your room is smallish because you'll probably have a good amount of room gain to reinforce the bass.
I'd say just go do it and tweak along the way.
I don't have measuring capability either except for an RS spl meter so don't feel too badly! Anyway...you're right, the series resistor would bring down the level of the mids. A high DCR coil is sometimes used in order to avoid use of that series resistor. Of course, my elementary understanding of active xovers would tell me that should you decide that you need to pad down the mids, you will have to add some resistance.
With respect to the difference in sensitivity between the mids and woofer, there are a couple of possible scenarios. I don't know whether or not you plan to put a high pass on the mids, but if you don't plan to do so, your speaker will in effect be a 2.5 way in which case the woofer will act as compensation of sorts for baffle step.
If you are going to high pass the mids and you plan on ending up with 91dB for the mids and 88dB for the bass...depending on where you plan to cross them, it might sound okay particularly since you say your room is smallish because you'll probably have a good amount of room gain to reinforce the bass.
I'd say just go do it and tweak along the way.
Delwon,
Thanx for all that.
I'll be crossing the mids at 150hz. Since it will be a 4th order L/R,
I think the problems will be minimal.
I've decided not to complicate the thing too much as it is my first try. I'm going for a simple M/T with a side-firing woofer. Hopefully 150 should be low enough not to spoil the imaging too much.
Regarding baffle step, the M/T will have the narrowest front-profile I can manage, maybe a cm or less from the edges. How I'm going to achieve this, hmmmmm..
The woofer should fill in just about the right amount of bass.
Since the XT25 is 91db I'll probably pad it down by 2.5 to 3db.
The active cross will have a volume control (attenuation only) so I can adjust the level of the Woofer & the M/T separately.
Thanx for all that.
I'll be crossing the mids at 150hz. Since it will be a 4th order L/R,
I think the problems will be minimal.
I've decided not to complicate the thing too much as it is my first try. I'm going for a simple M/T with a side-firing woofer. Hopefully 150 should be low enough not to spoil the imaging too much.
Regarding baffle step, the M/T will have the narrowest front-profile I can manage, maybe a cm or less from the edges. How I'm going to achieve this, hmmmmm..
The woofer should fill in just about the right amount of bass.
Since the XT25 is 91db I'll probably pad it down by 2.5 to 3db.
The active cross will have a volume control (attenuation only) so I can adjust the level of the Woofer & the M/T separately.
my floor speakers i'm STILL working on sound a bit like urs:
1 x 1inch dome tweeter
2 x 5inch midrange
1 x 8inch, side firing
in mtmw config. i've also attenuated the tweeter, but have no need to do so on the mids.
the cabinets are 160mm x 340mm x 1200mm externally. with those kinda dimensions, they look so mean 🙂
i've crossed the m/t at 3.5khz, 2nd order. left it bi-amped, but will run an external passive crossover when they are finished at around 150Hz due to lack of amps. i tested them with multiple amps crossed over actively at 110Hz and it sounded great, the 5inches really can take a heap above around 100Hz, and so going higher doesn't seem all that necessary.
1 x 1inch dome tweeter
2 x 5inch midrange
1 x 8inch, side firing
in mtmw config. i've also attenuated the tweeter, but have no need to do so on the mids.
the cabinets are 160mm x 340mm x 1200mm externally. with those kinda dimensions, they look so mean 🙂
i've crossed the m/t at 3.5khz, 2nd order. left it bi-amped, but will run an external passive crossover when they are finished at around 150Hz due to lack of amps. i tested them with multiple amps crossed over actively at 110Hz and it sounded great, the 5inches really can take a heap above around 100Hz, and so going higher doesn't seem all that necessary.
Hi, Phreeky
I was looking at a similiar design (with all passive crossovers).
How did you find the sidefiring woofer for imaging? Do you think it was any different from a front firing woofer? And were they firing in or out?
Also, I see you're in Aussie. Where have you sourced your drivers from?
Mos
I was looking at a similiar design (with all passive crossovers).
How did you find the sidefiring woofer for imaging? Do you think it was any different from a front firing woofer? And were they firing in or out?
Also, I see you're in Aussie. Where have you sourced your drivers from?
Mos
Hi,
Some of the best systems have a side-firing woofer with a very narrow front profile best for imaging.
Mission Pilastro
Canton Ref. 2DC
Audio Physic
Sonus Faber
If the mids can be made to go low enough so that the frequencies handled by the woofer don't interfere with the imaging, I don't see why not.
Bass or low freq. is supposed to be omni-directional, so we could all be right.
I'm still undecided about the MTMW or MTW. What would be the difference between them where power is concerned. I'm going to be using separate power amps acitively crossed at 100-150.
Theory says it should get loud enough, but maybe you experienced builders can shed some light on WHAT ACTUALLY HAPPENS ?
Another thing, how have you handled the corners for the front profile, curved or wedged ?
Mos,
For drivers, check out www.mass.com.au.
They have fantastic deals.
I'm buying mine from them.
Some of the best systems have a side-firing woofer with a very narrow front profile best for imaging.
Mission Pilastro
Canton Ref. 2DC
Audio Physic
Sonus Faber
If the mids can be made to go low enough so that the frequencies handled by the woofer don't interfere with the imaging, I don't see why not.
Bass or low freq. is supposed to be omni-directional, so we could all be right.
I'm still undecided about the MTMW or MTW. What would be the difference between them where power is concerned. I'm going to be using separate power amps acitively crossed at 100-150.
Theory says it should get loud enough, but maybe you experienced builders can shed some light on WHAT ACTUALLY HAPPENS ?
Another thing, how have you handled the corners for the front profile, curved or wedged ?
Mos,
For drivers, check out www.mass.com.au.
They have fantastic deals.
I'm buying mine from them.
i'm using all jaycar response drivers, but thinking of changing to vifa tweeters in future (or another tweeter available as magnetically shielded, to match a center)
i have a single response dome tweeter, two 5" 4ohm shielded response woofers and 1 response 8" 8ohm woofer
i only tested a single cabinet temporarily constructed, and all corners at the time were square. i found myself relocating the speaker around the room, as i ran sine wave sweeps, ensuring i wasn't missing any frequencies. the imaging is fine with the side firing woofer, something i was also originally worried about. but of course that will depend on your crossover.
i found that the 5"s take plenty of power when the crossover was at 100-110Hz. the active crossover was built into an amp, therefore i'm unsure of the order, but appears very steep - probably 4th. i don't know much at all about active crossovers tho.
the whole lot is sealed, 5"s using 6.4L of volume (shared), and the 8" using approx 30L. i'm very happy with the 8", playing nicely down to 40Hz, but unfortunately peaking around 35 (around the driver resonant f). i'll probably be running a 12" for everything that low anyway, we'll see.
i crossed the m/t at 3.5KHz, although i could have gone quite a bit higher, as the mids response goes quite high (seems good up to 7KHz)
i'm not very experienced at this, being my first diy project (other than my sub). if u want any more info, maybe a picture (tho it'll be webcam quality), let me know. i myself will appreciate any info of use to me. happy diy-ing
i have a single response dome tweeter, two 5" 4ohm shielded response woofers and 1 response 8" 8ohm woofer
i only tested a single cabinet temporarily constructed, and all corners at the time were square. i found myself relocating the speaker around the room, as i ran sine wave sweeps, ensuring i wasn't missing any frequencies. the imaging is fine with the side firing woofer, something i was also originally worried about. but of course that will depend on your crossover.
i found that the 5"s take plenty of power when the crossover was at 100-110Hz. the active crossover was built into an amp, therefore i'm unsure of the order, but appears very steep - probably 4th. i don't know much at all about active crossovers tho.
the whole lot is sealed, 5"s using 6.4L of volume (shared), and the 8" using approx 30L. i'm very happy with the 8", playing nicely down to 40Hz, but unfortunately peaking around 35 (around the driver resonant f). i'll probably be running a 12" for everything that low anyway, we'll see.
i crossed the m/t at 3.5KHz, although i could have gone quite a bit higher, as the mids response goes quite high (seems good up to 7KHz)
i'm not very experienced at this, being my first diy project (other than my sub). if u want any more info, maybe a picture (tho it'll be webcam quality), let me know. i myself will appreciate any info of use to me. happy diy-ing
mind the step
Due to step diffraction you need to eq your mid freqs about 4dB down from 200Hz to 1KHz gradually. (6dB anechoic)
This robs 96 dB down to 92 dB. Some DCR loss in your woofers coil and usual oversensitivity of tweeters when measured on a baffle will get you 91dB spot on. No padding needed!
Due to step diffraction you need to eq your mid freqs about 4dB down from 200Hz to 1KHz gradually. (6dB anechoic)
This robs 96 dB down to 92 dB. Some DCR loss in your woofers coil and usual oversensitivity of tweeters when measured on a baffle will get you 91dB spot on. No padding needed!
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