Hi Folks,
I have read that there was some interest in the 2 way OB with CSS FR125S and a bass driver (Eminnence Beta 15").
Has anyone tried it? If so, how would the crossover design look?
I was very intrigued by the Visaton Nobox but I already have the Fr125s so maybe I can use those.
Thanks,
Rafal
I have read that there was some interest in the 2 way OB with CSS FR125S and a bass driver (Eminnence Beta 15").
Has anyone tried it? If so, how would the crossover design look?
I was very intrigued by the Visaton Nobox but I already have the Fr125s so maybe I can use those.
Thanks,
Rafal
Any idea on what would be amplification requirements for a 2 way OB (FR125S and 15' Eminnence Beta)? In other words, would a 20w/ch chipamp be ok to drive them?
I know this is a rather hypothetical question, but I just want to get an idea if I will be ok using my cipamp or if I will run into trouble. This chipamp just running the FR125S in OB seems to work fine.
I know this is a rather hypothetical question, but I just want to get an idea if I will be ok using my cipamp or if I will run into trouble. This chipamp just running the FR125S in OB seems to work fine.
Not quite your OB FR125S, but I did a hybrid with a woofer so the information here might give you some ideas.
Your chipamp should be fine as long as you don't go nuts on the volume control
I found the T-amp I have ran out of puff quickly but my chipamps have no problems and they are about 29W.
Your chipamp should be fine as long as you don't go nuts on the volume control
I found the T-amp I have ran out of puff quickly but my chipamps have no problems and they are about 29W.I am also interested in a project such as this. I would consider active amplification with a mono sub amp for the dual bass drivers and and small tube or chip amp for the small fullrangers. crossover as low as possible at least, but i think that this would be great with those CSS FR125S above 150hz and a pair of dayton audio reference 15" for below. keep me posted!
James D, an occasional contributor here, has an interesting way of crossing over two drivers like an Eminence and something else (whatever it happens to be) on OB. As I understand it, the drivers are connected in series, and have the filter components in parallel across them. Should be easy enough to alter for the CSS unit. Don't ask me how it works though -I've no details, and XOs are not my thing.
Hi Scott!
The problem with the eminence and the CCS FR is the large sensitivity difference.... fortunately its the Em that is more sensitive so you can pad it down... which has its own problems..
I would use different drivers - either different bass driver or different fullrange...
Heres a link comparing series and parallel filters x-over filters
James
The problem with the eminence and the CCS FR is the large sensitivity difference.... fortunately its the Em that is more sensitive so you can pad it down... which has its own problems..
I would use different drivers - either different bass driver or different fullrange...
Heres a link comparing series and parallel filters x-over filters
James
Cheers for that James -I really should have thought of that. Eliot Sound is a site I occasionally visit, usually to get a reality check, but I hadn't seen this article before -if it's half as good as his other work, I reckon I'm going to enjoy working my way through it.
Look forward to meeting you at Eggfest
Best
Scott
Look forward to meeting you at Eggfest
Best
Scott
If you cross over low enough, the added efficiency of the Eminence woofer could be used to extend the bass response and might even allow the baffle size to be reduced. Having the bass driver more efficient than the mid-range/full range driver can be a real advantage and traded off in the design process. It depends on the sophistication of the design process to use the added efficiency to its full advantage. A lower or equal efficency woofer in an OB reduces the variables and ties the design diown with fewer options to trade off. I would trade the CSS FR driver and keep the Eminence woofer (or maybe use the Alpha version) if I were doing the design work.
Ummm....
If the bass driver is mounted on an open baffle, either flat or U-shape (like I design) then you cannot extend the drivers frequency response downwards by adding series resistance or using an autoformer to reduce its sensitivity - you can extend the measured response of the system by reducing the higher frequencies to the same sensitivity as the rolled off low end of the bass driver ( which is what the series resistor does...) but it doesn't change the bass drivers response wrt roll off. It does cause the system effective Qes to increase so the bass response becomes peaky and the sound of the system changes - usually (always when I have tried it) for the worse... so I don't like to do this...
Also the baffle response will be strongly influencing the low end response (for any practical domestic baffle) and reducing its size will impact the bass response by lifting the system lf rolloff point in some manner...
Martin - are you suggesting using some lf EQ network, either active or passive to adjust things or is it the pulling down of the rest of the frequency range to match the lf roll off of the driver that you are suggesting?
James
If the bass driver is mounted on an open baffle, either flat or U-shape (like I design) then you cannot extend the drivers frequency response downwards by adding series resistance or using an autoformer to reduce its sensitivity - you can extend the measured response of the system by reducing the higher frequencies to the same sensitivity as the rolled off low end of the bass driver ( which is what the series resistor does...) but it doesn't change the bass drivers response wrt roll off. It does cause the system effective Qes to increase so the bass response becomes peaky and the sound of the system changes - usually (always when I have tried it) for the worse... so I don't like to do this...
Also the baffle response will be strongly influencing the low end response (for any practical domestic baffle) and reducing its size will impact the bass response by lifting the system lf rolloff point in some manner...
Martin - are you suggesting using some lf EQ network, either active or passive to adjust things or is it the pulling down of the rest of the frequency range to match the lf roll off of the driver that you are suggesting?
James
I am not suggesting any EQ.
For example, if you start with the Eminence Alpha 15A, the infinite baffle response is 95 dB/w/m down to 40 Hz and the -6 dB point is below 30 Hz. So if I wanted to mate this with a less efficient mid/full range driver, lets say 90 dB/w/m for example, then I have a few dB to play with in the crossover at the top end of the woofer's useful frequency range and the baffle size at the bottom end of the woofer's useful frequency range. So by designing a smaller baffle which rolls off a bit higher and a low crossover point, between 100 and 200 Hz, the resulting net efficiency for the Eminence woofer would be lowered and closer to the target 90 dB mid/full range driver's efficiency.
This is what I did on my initial Lowther OB project where the combined Dayton woofers had a 106 dB/w/m value compared to the Lowthers 98 dB/w/m. I also put together a few paper designs like this for the Eminence Alpha 15A and a few of the smaller Fostex full range drivers. It is a little tricky to design but can work very well.
For example, if you start with the Eminence Alpha 15A, the infinite baffle response is 95 dB/w/m down to 40 Hz and the -6 dB point is below 30 Hz. So if I wanted to mate this with a less efficient mid/full range driver, lets say 90 dB/w/m for example, then I have a few dB to play with in the crossover at the top end of the woofer's useful frequency range and the baffle size at the bottom end of the woofer's useful frequency range. So by designing a smaller baffle which rolls off a bit higher and a low crossover point, between 100 and 200 Hz, the resulting net efficiency for the Eminence woofer would be lowered and closer to the target 90 dB mid/full range driver's efficiency.
This is what I did on my initial Lowther OB project where the combined Dayton woofers had a 106 dB/w/m value compared to the Lowthers 98 dB/w/m. I also put together a few paper designs like this for the Eminence Alpha 15A and a few of the smaller Fostex full range drivers. It is a little tricky to design but can work very well.
Ok.
This thread just went into the area that I know very little of (crossovers/ baffle step correction and such).
I would like to drive the whole thing from a single chipamp, therefore a passive crossover but crossed very low (100/200 Hz) . Also first Order to keep things simple. Maybe even running the full range driver wide open. I am hoping to keep the baffle relatively small (something like 2.5'x3').
Martin, what you mentioned about matching higher efficiency woofer sounds interesting but I'm wondering / hoping that maybe you could show me some examples that I could just tweak to my application.
Also, would this approach (OB bass driver) have adventages over just adding subwoofer?
I was also looking at this driver which kind of looks promising. what do you think?
http://www.musicsupplycenter.com/ProductDetails.asp?ProductCode=813-021&Show=TechSpecs
This thread just went into the area that I know very little of (crossovers/ baffle step correction and such).
I would like to drive the whole thing from a single chipamp, therefore a passive crossover but crossed very low (100/200 Hz) . Also first Order to keep things simple. Maybe even running the full range driver wide open. I am hoping to keep the baffle relatively small (something like 2.5'x3').
Martin, what you mentioned about matching higher efficiency woofer sounds interesting but I'm wondering / hoping that maybe you could show me some examples that I could just tweak to my application.
Also, would this approach (OB bass driver) have adventages over just adding subwoofer?
I was also looking at this driver which kind of looks promising. what do you think?
http://www.musicsupplycenter.com/ProductDetails.asp?ProductCode=813-021&Show=TechSpecs
MJK,
The flaw in that approach is the 95db at 1w/1m from a single 15 in OB at 40hz. If that is indeed true, which is doubtful, then the 1w also uses up most of the excursion at only 1w, leaving you absent of headroom. While we can do a little better than SL's SPLmax spreadsheet predictions, we are still quite limited by the physics down low.
The flaw in that approach is the 95db at 1w/1m from a single 15 in OB at 40hz. If that is indeed true, which is doubtful, then the 1w also uses up most of the excursion at only 1w, leaving you absent of headroom. While we can do a little better than SL's SPLmax spreadsheet predictions, we are still quite limited by the physics down low.
Martin,
Agreed - that what I said but it doesn't extend the Alpha 15" response at all and that still interacts with the baffle shape and size in exactly the same way i.e. the 30Hz response curve is unchanged in terms of its roll off profile... The system response measures wider for -3dB point because you have pulled the rest of the signal down to the level of the 30Hz response...
I guess its semantics as much as anything and I have had too many people trying to tell me that you can push as driver's bass response below that on its OB response curve just by adding a series resistor - which is a nonsense as you haven't change any of the driver parameters that might accomplish that such as the mass of the cone, the motor inductance, the suspension, the motor strength... i.e you have made no internal change to the driver - just an external change and one that changes the sound of the driver - which I guess might improve it but in my experience never has...
John,
The Eminence 15" drivers all achieve 95dB at 1W, 1m - some will do more. Measured in practice and according to the spec sheet. All of them hit xmax limits of between 10 and 40 W at 40Hz on an OB and all are rated between 150 and 600W per driver... so they are fine for OB use with low power amps - which is what we all tend to use
Still writing my reply to your email - many thanks for that - got distracted by this thread!
Tade,
Bottom line is that it can work and actually it will make the Em match the CCS FR in tems of sound character as it makes the Em dynamics match the CCS FR and your chip amp should drive the combination
James
Agreed - that what I said but it doesn't extend the Alpha 15" response at all and that still interacts with the baffle shape and size in exactly the same way i.e. the 30Hz response curve is unchanged in terms of its roll off profile... The system response measures wider for -3dB point because you have pulled the rest of the signal down to the level of the 30Hz response...
I guess its semantics as much as anything and I have had too many people trying to tell me that you can push as driver's bass response below that on its OB response curve just by adding a series resistor - which is a nonsense as you haven't change any of the driver parameters that might accomplish that such as the mass of the cone, the motor inductance, the suspension, the motor strength... i.e you have made no internal change to the driver - just an external change and one that changes the sound of the driver - which I guess might improve it but in my experience never has...
John,
The Eminence 15" drivers all achieve 95dB at 1W, 1m - some will do more. Measured in practice and according to the spec sheet. All of them hit xmax limits of between 10 and 40 W at 40Hz on an OB and all are rated between 150 and 600W per driver... so they are fine for OB use with low power amps - which is what we all tend to use
Still writing my reply to your email - many thanks for that - got distracted by this thread!
Tade,
Bottom line is that it can work and actually it will make the Em match the CCS FR in tems of sound character as it makes the Em dynamics match the CCS FR and your chip amp should drive the combination
James
James,
It's the "95db/1w/1m at 40hz" to which I take exception as does Eminence http://eminence.com/pdf/alpha-15a.pdf
It's the "95db/1w/1m at 40hz" to which I take exception as does Eminence http://eminence.com/pdf/alpha-15a.pdf
Interesting as the Alpha 15 (not the a) Eminence pdf shows it flat to 40Hz then rolling off... and the T/S parameters are the same inboth cases...
However, I should have been more explicit...
mounted on the baffle that Martin uses or the one that I use and without any EQ the Em Alpha 15 is flat to 45Hz at 94dB/1W/1m measured response in my case. (actually has a +2.5dB hump at 60Hz due to its high Qes (1.52)
The Em Beta 15 on the same baffle is flat and this really is flat to 40Hz at 95dB/1W/1m...
All with no Eq but with mounting of the driver low down on the baffle to take advantage of the floor lift.
James
However, I should have been more explicit...
mounted on the baffle that Martin uses or the one that I use and without any EQ the Em Alpha 15 is flat to 45Hz at 94dB/1W/1m measured response in my case. (actually has a +2.5dB hump at 60Hz due to its high Qes (1.52)
The Em Beta 15 on the same baffle is flat and this really is flat to 40Hz at 95dB/1W/1m...
All with no Eq but with mounting of the driver low down on the baffle to take advantage of the floor lift.
James
Maybe Eminence has their graphs screwed up and not matching up with the right drivers, because the high Q Alpha should do better than their graph shows, although nowhere near 95db at 40hz in IB. Plugging in to SL's SPLmax spreadsheet using a 100m separation distance (IB), the Alpha runs out of excursion at 103db. That means about 7 watts with 95db/1w/1m, and 103db at 40hz with 7 watts doesn't seem right. 100hz sure why not, but not 40. Are you talking about measured responses?
Here's the Beta http://eminence.com/pdf/beta-15a.pdf
Oh and btw, I'm don't doubt that you're getting nice full OB bass without EQ. Using the floor and rear wall can be used to great advantage with OB.
Here's the Beta http://eminence.com/pdf/beta-15a.pdf
Oh and btw, I'm don't doubt that you're getting nice full OB bass without EQ. Using the floor and rear wall can be used to great advantage with OB.
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