InclinedPlane said:
The magnets on the Jamo drivers look small (smaller than the spider - http://www.6moons.com/audioreviews/jamo/detail2.jpg). Additionally the speaker shown in a review as the "prototype" has tiny magnets and thus appears to be very high Q (http://www.6moons.com/audioreviews/jamo/prototype.jpg).
I doubt they are low Q probably mid-high Q --> additionally according to the whitepaper, they use air coils in the crossover which should add ~1 ohm in the bass -- increasing the Q and decreasing sensitivity.
Sean
Godzilla's post (#29) about the Goldwood GW-215/40/8 15" got me thinking. MJK's advice is to choose a woofer, then get a mid/tweet 6 to 10 db less efficient. The Goldwood is rated for 90dB, so we'd need a nice small wide-range of about 84dB or less.
I think I just figured out what the Dayton RS100-4's were intended for! They are rated for 84.2dB, which I thought was disappointing, but now it fits well here. All reports say they're really clean, and OK for OB at upper frequencies. Just need a woofer.
What are your opinions of this idea? At about $125 for drivers, it should be affordable even for me, IF I save for it.
I think I just figured out what the Dayton RS100-4's were intended for! They are rated for 84.2dB, which I thought was disappointing, but now it fits well here. All reports say they're really clean, and OK for OB at upper frequencies. Just need a woofer.
What are your opinions of this idea? At about $125 for drivers, it should be affordable even for me, IF I save for it.
Sure I think you can get some nice sound that way. Just know that any sensitivity rating is an average across all frequencies the speaker is rated to cover. Its sensitivity will fall below 100hz and so the lower you go the lower it will be. Add to that the cancellation losses associated with OB and on top of that the baffle step loss which naturally occurs due to the almost omnidirectional projection of bass.
Fixes for this include
Padding down the fullrange driver
Using more bass helper drivers
Running bass drivers at a lower impedance
Using higher Q bass helper drivers
Adding a baffle step compensator of some kind
Amplifying drivers seperately
Playing bass-heavy music
Fixes for this include
Padding down the fullrange driver
Using more bass helper drivers
Running bass drivers at a lower impedance
Using higher Q bass helper drivers
Adding a baffle step compensator of some kind
Amplifying drivers seperately
Playing bass-heavy music
PKNJ said:
Assuming that we are talking about a high Qts driver, the 6 to 10 dB efficiency difference is definitely true for an OB design where the low frequencies are significantly rolled off by the baffle. For an H frame or U frame design, you can probably get away with a woofer 3 dB more efficient then the full range driver, you will loose a few dB by putting it into the frame but gain some additional low bass frequency output. My statement in post #9 was probably not detailed enough to make that distinction.
As always, my advice is to run some form of simulation before you buy drivers to see what you should expect and avoid as much as possible putting time and money into something that is just not going to work well.
Martin, did you make a listening comparison between the original crossover (second order LR high pass) and the second crossover (fourth order LR high pass) in the Jordan/Goldwood OB system? Or, did you choose the second crossover based soley on the SPL response curves. The peak at 400 Hz is slightly reduced with the second crossover but the high and low pass curves appear to be less symmetrical about the crossover frequency. I wonder what are the differences sonically, if any.
Dean
Dean
dhieber said:
Hi Dean,
I started out with the design crossover and listened to it for a few days. It was OK but something just did not sound right to me, maybe the crossover maybe the room. So I worked with the test data to come up with the alternate crossover settings and it seemed to work better in the simulations. When I switched the active crossover to use the newer settings, the sound did change and I feel it is more balanced and smoother through the crossover frequencies.
dublin78 said:
dublin78,
Yes, my goal is to come up with a passive crossover and try it in my system. I'll start with my favorite set of full range drivers after hearing the different options and see where things go. Unfortunately, it is probably several months off. I have a bunch of other audio/worksheet things I am working on in parallel.
Just the right thread at just the right time .
I got my first real taste of dipole bass when building a variant of MJKs Alpha 15 OBs with an fe83.
My mains are sealed ZD5s, and need some help on the low end. The alpha 15s in OB sound wonderful. As may others have said before, this is the bass I want! The main problem I had with them, however, was that they didnt really have enough room to breathe in my room and the low end rolled off much sooner than I would have liked, presumably because they were too close to a rear wall.
I want to build an H frame sub with an alpha 15 to complement my mains. Level matching won't be an issue as it can be solved by adjusting the gain of the sub amp. The ZD5s are only about 82dB anyway. Now on to a couple of questions...
I'm hoping I can get the H frame sub to go deep without being thwarted by walls by placing it against a wall but with the driver perpendicular to the wall. My thoughts are that this should work fine and could actually go some way to mitigating the "acoustic short circuit" and actually improve the bass response. Am I right?
I was also wondering if theres any way to get them to go deeper? I'm happy to sacrifice even more efficiency for greater extension but playing with MJKs sheets for a minute I couldnt make it happen. I will probably end up leaving the mains running full range and putting an active 4th order LP at around 75Hz on the sub - according to the sheets this should give an approximate 2nd order acoustic rolloff that I hope will integrate nicely with the mains.
Godzilla, please let me know how yours turn out!
Thanks
PS Is there not a decent chance the F120A would work well as a simple drop in replacement for the jordan?
.I got my first real taste of dipole bass when building a variant of MJKs Alpha 15 OBs with an fe83.
My mains are sealed ZD5s, and need some help on the low end. The alpha 15s in OB sound wonderful. As may others have said before, this is the bass I want! The main problem I had with them, however, was that they didnt really have enough room to breathe in my room and the low end rolled off much sooner than I would have liked, presumably because they were too close to a rear wall.
I want to build an H frame sub with an alpha 15 to complement my mains. Level matching won't be an issue as it can be solved by adjusting the gain of the sub amp. The ZD5s are only about 82dB anyway. Now on to a couple of questions...
I'm hoping I can get the H frame sub to go deep without being thwarted by walls by placing it against a wall but with the driver perpendicular to the wall. My thoughts are that this should work fine and could actually go some way to mitigating the "acoustic short circuit" and actually improve the bass response. Am I right?
I was also wondering if theres any way to get them to go deeper? I'm happy to sacrifice even more efficiency for greater extension but playing with MJKs sheets for a minute I couldnt make it happen. I will probably end up leaving the mains running full range and putting an active 4th order LP at around 75Hz on the sub - according to the sheets this should give an approximate 2nd order acoustic rolloff that I hope will integrate nicely with the mains.
Godzilla, please let me know how yours turn out!
Thanks
PS Is there not a decent chance the F120A would work well as a simple drop in replacement for the jordan?
I ran some sims on OB and corner loading, the way i see it with the proper rear deflector you can corner load an OB with the fact of it performing more like the Bo$e 901. This in itself is not a bad thing as the figure 8 response is basically sent to the sides of the rear portion of the baffle. You can even back an OB to a wall with a deflector. The reason i did the sim was the fact of placement in the room , which with an OB demands away from the side and rear walls , which in some applications is not a viable option.
Any ideas or feedback is very welcome.
Thanks
ron
Any ideas or feedback is very welcome.
Thanks
ron
>>> Level matching won't be an issue as it can be solved by adjusting the gain of the sub amp.
That's what i am going to do. I drew out my wood cuts yesterday. All i need to do is get to Home Depot. After the wood is cut i will order the drivers. I have an 18 inch ruler and held it up in front of me to get a better idea how big an 18 inch woofer will be. It looks like it will be huge. I am going to go for two fifteen inchers. Can't wait to play again!
That's what i am going to do. I drew out my wood cuts yesterday. All i need to do is get to Home Depot. After the wood is cut i will order the drivers. I have an 18 inch ruler and held it up in front of me to get a better idea how big an 18 inch woofer will be. It looks like it will be huge. I am going to go for two fifteen inchers. Can't wait to play again!
UK Members: I am ordering some Goldwood GW1858s direct from Goldwood in the US. They will be shipped via surface (longer time but cheaper).
I have had to buy an extra pair to meet a minimum order size, so these are up for grabs if anyone wishes to split costs.
PM me.
If there is a large amount of interest, I may organise a UK group buy.
I have had to buy an extra pair to meet a minimum order size, so these are up for grabs if anyone wishes to split costs.
PM me.
If there is a large amount of interest, I may organise a UK group buy.
valleyman said:
Last question first, yes I think that the F120A will be a good alternative to the Jordan JX92S. My pair pf F120A drivers arrived on Wednesday and I hope to be listening to them over the weekend.
If you do not care about the efficiency of the Alpha 15A in an H frame, you might consider adding some weights to the cone. This will lower fs, raise Qts, and drop the SPL/W/m. I would try the Alpha 15A unmodified first, that should get you down to 30 Hz. Listen and then decide if you want ot add weights.
Room placement of the H frame is an interesting discussion. Remember that the maximum output is on the axis of the driver and the minimum, theoretically zero, is at 90 degrees to the driver. So if you place them flush against a wall and listen off axis I am not sure you will be gaining much. I have mine placed about 3' out from the rear wall and about 4 ' from the side walls and pointed directly at the sweet spot. When considering the sound from the reflections, think of the walls as mirrors and visulaize a phantom H frame on the other side of the wall. When I look at the phantom H frames behind the rear wall and behind the side wall I am looking at the sides of the H frame so not much sound comes from them. The only sound that comes directly at me is the mirror image diagonally through the room corner, but this is not 6 to 10 feet away so its influence is probably not so strong.
So I think that you want the H frame poisnted right at the listening position. I think if you have them 3 to 4 feet out into the room you should do well with the bass freauencies.
>>> So I think that you want the H frame poisnted right at the listening position. I think if you have them 3 to 4 feet out into the room you should do well with the bass freauencies.
Mine will be about 3 to 4 feet in front of the rear wall with a BIB behind each (but with about 2 feet of space in between). I look forward to playing with room placement. Fortunately, i have a dedicated listening room (that has been doubling as an exercise room lately).
Can the depth of the H frame can be made less deep? I am planning on using standard lumber which is 11.25 deep with the 15 inch drivers. Can i do this without losing too much bass?
Mine will be about 3 to 4 feet in front of the rear wall with a BIB behind each (but with about 2 feet of space in between). I look forward to playing with room placement. Fortunately, i have a dedicated listening room (that has been doubling as an exercise room lately).
Can the depth of the H frame can be made less deep? I am planning on using standard lumber which is 11.25 deep with the 15 inch drivers. Can i do this without losing too much bass?
Hello,
do you think that the speaker with the parameters indicated bellow will work fine in H frame instead of Eminence Alpha15?
This is not expensive and easy to buy in Europe.
Thanks
Guglielmo
Italy
Gesamtdurchmesser: 380 mm
Impedanz: 8 Ohm
Leistung: 120 Watt RMS (sinus)
Schalldruck: 96 dB
Frequenzbereich: 30 - 5.500 Hz
Einbautiefe: 160 mm
Lochkreis: 372 mm
Benötigte Lochöffnung: 350 mm
Thiele-Small-Parameter:
FS: 33,2682 Hz
Re: 7,5000 Ohm
Qms: 2,6765
Qes: 1,2554
Qts: 0,8545
Vas: 259,5566 l
Xmax: +- 8mm
No (Ref efficency): 0,7362 %
Sd: 0,7362 sqm
Motor Impedance Parameter:
Levc (Induc at 1 kHz): 0,7550 mH
Levc (Induc at 20 kHz): 0,2449 mH
Krm (Resistance Cons): 2,6781 mOhm
Kxm (Resistance Cons): 20,2016 mH
Rem (Res at 1 kHz): 2,4825 Ohm
Rem (Res at 20 kHz): 25,7773 Ohm
Erm (Resist. Expont): 0,7812
Exm (React Expont): 0,6242
do you think that the speaker with the parameters indicated bellow will work fine in H frame instead of Eminence Alpha15?
This is not expensive and easy to buy in Europe.
Thanks
Guglielmo
Italy
Gesamtdurchmesser: 380 mm
Impedanz: 8 Ohm
Leistung: 120 Watt RMS (sinus)
Schalldruck: 96 dB
Frequenzbereich: 30 - 5.500 Hz
Einbautiefe: 160 mm
Lochkreis: 372 mm
Benötigte Lochöffnung: 350 mm
Thiele-Small-Parameter:
FS: 33,2682 Hz
Re: 7,5000 Ohm
Qms: 2,6765
Qes: 1,2554
Qts: 0,8545
Vas: 259,5566 l
Xmax: +- 8mm
No (Ref efficency): 0,7362 %
Sd: 0,7362 sqm
Motor Impedance Parameter:
Levc (Induc at 1 kHz): 0,7550 mH
Levc (Induc at 20 kHz): 0,2449 mH
Krm (Resistance Cons): 2,6781 mOhm
Kxm (Resistance Cons): 20,2016 mH
Rem (Res at 1 kHz): 2,4825 Ohm
Rem (Res at 20 kHz): 25,7773 Ohm
Erm (Resist. Expont): 0,7812
Exm (React Expont): 0,6242
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