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In Reply to: RE: Help needed with BMS compression driver horn experiment posted by kurt s on June 18, 2007 at 09:55:29
hm..
well.. i'm not an expert-- but to my knowledge, to run a horn out to it's limit is going to end up compromising sound. an octave above it's lowest point is, best i know, the rule of thumb. besidedly-- running ANY driver full range over 8 octaves, and any horn the same amount.. that's a lot to ask!
my knowledge of the 4592 is in a system that crosses in the 500-1000 hz range over an onken with two altec 515s.. doesn't seem too compromised, honestly! and regardless of it's more than single point source-- it doesn't seem to suffer or get harsh.
my personal experience with a BMS 4552 (which is just a single 1.5" driver) is fraught with coping with harshness- but primarily due to an incorrectly implemented crossover. THAT took a bit of tweakery-- but in the end-- it's not the driver, it was me and my lack of measurement capacities!
what is your current crossover topology? are you using an active, or a passive?
i wouldn't get too hung up on single point source or crossover points as concepts-- they're nice ideals-- but that ain't the problem, i'd suspect. most bass drivers'll get your north of 500hz (although i'm not certain as to what you're using), to my knowledge, and crossovers aren't necessarily evil either! even if you're running a bass driver up 'that high'-- it's sonic penalties can't be any worse than running a compression driver 'that low'!
throw out to the forum what you have-- maybe there's an amenable answer to be found, if not 'nirvana'.
yrs
d.
Follow Ups:
> what is your current crossover topology? are you using an active, or a passive? <
After a lot of messing around, here is the present condition of this system:
I have an active biamped system between the bassbins and the horn. The bass amp receives an active crossover of 3rd order at about 400 Hz (the frequency is dial-able by a pot.) This bassbin is only about 90 dB sensitive and is powered by 100W of SS power. Gain is adjusted to match the horn's output.
The horn assembly receives its power from an active-filtered HF tube amp, from 400 Hz on up, 2nd order. Within the horn assembly is a first order crossover somewhere below 250 Hz to the mid driver and then passively crosses over to the tweeter driver at about 6.5 KHz. This assembly with its own passive crossover is an unknown beyond that since it is sealed up and is proprietary to BD-Design.
There is a mismatch between the low frequency direct radiator and the horn in two respects. The horn loading or lack thereof and the type of amp that is driving it. The higher this crossover goes, the worse the sound is at low volume levels due to this lack of matching. At 250 Hz it's not as bad as 400 Hz. Now the midband is starting to be heard directly from the SS powered woofer which is simply not as clean, dynamic, nor detailed as the horn with tube amplification.
> i wouldn't get too hung up on single point source or crossover points as concepts-- they're nice ideals-- but that ain't the problem, i'd suspect. most bass drivers'll get your north of 500hz (although i'm not certain as to what you're using), to my knowledge, and crossovers aren't necessarily evil either! even if you're running a bass driver up 'that high'-- it's sonic penalties can't be any worse than running a compression driver 'that low'! <
I'm not hung up on the point source issue at all which is why I thought of midrange horn plus tweeter horn separately as the solution to making a clean high SPL system. I was thinking bassbin 30 - 300 Hz or maybe 30 - 400 Hz, then compression midrange horn 300 Hz? - 6 KHz, then bullet tweeter 6 KHz - 20 KHz. The bassbins would be either 3rd or 4th order low pass. The midrange would be maybe 4th order high pass to 1st order low pass, and the tweeter 2nd order high pass.
Then the question would be what drivers? I don't want to buy too expensive drivers yet and I don't want to buy another expensive horn to replace the one I have. The one I have is a good round 250 Hz horn with good wideband response and no honkiness.
> throw out to the forum what you have-- maybe there's an amenable answer to be found, if not 'nirvana'. <
Well, there you have it. I hope someone can be creative in thinking up a solution that's appropriate and will work. I think what I propose is a decent start, if not the ultimate. The bass is the weakness here IMO. I also am space constrained and that's why this "Onken" is a small cheap 10" Vifa paper cone woofer. It can go to higher frequencies and all that, but when you're listening to solid state on the bottom to low mids and single-ended tube on the low mids on up, it's definitely another compromise in terms of "seamlessness".
This system used to be a 150 Hz horn for a Lowther driver which made for a very full range horn and the bassbins were truly just for bass. It's creeping up to be for bass and low mids.
Kurt
> > > bass is the weakness here IMO. I also am space constrained and that's why this "Onken" is a small cheap 10" Vifa paper cone woofer. It can go to higher frequencies and all that, but when you're listening to solid state on the bottom to low mids and single-ended tube on the low mids on up, it's definitely another compromise in terms of "seamlessness". < < <
Hi kurt,If size constraint s a real concern maybe the low Vas Deltalite 10" from Eminence or the BassLite Hemp 10" MI woofers would be a good solution when ss driven... Try MLTL enclosures.
http://www.eminence.com/guitar_speaker_detail.asp?model=BASSLITECH2010&speaker_size=10&SUB_CAT_ID=5
http://www.eminence.com/proaudio_speaker_detail.asp?web_detail_link=DELTALITEII2510&speaker_size=10&SUB_CAT_ID=3
usspeaker.com has them on sale.
I dunno what dims you used for the 'Onkened' Vifa, but high Vas drivers would work well in an MLTL enclosure if designed to be used with high ouput Z amps (tube), ergo you can get away with smaller bassbin dims and placement near wall/s for adequate room gain bass lift. As someone told me before. it's a 'classic vintage' implementation that works well. Of course, you would have to change amps for 'seamlessness', something like 5-7W tube. IIRC, you used to have PP45 amps. That might be good compromise if you dont mind going fullrange passive and not bi-amp. Or maybe even go higher power Eimac valve SE. I want to try PP45's mself but not IT coupled, instead plan is for L-splitter parafeed using an SE input stage.
fred
it sounds like you're definitely compromising in the bass bin-- which for a 2 way might be it's undoing!
i don't know if you can come up with a good compromise with your current configuration that'd be seamless-- it just sounds like a monumental shift in tonalities! it sounds like one way or another, you're going to need either a much more efficient low/mid driver that's capable of a wider range (in which case you have to deal with the compromise of imperfection in the midbass and low bass..) or you're going to have to have some sort of infill midbass driver by itself.. which is a whole other can o' worms..
honestly.. i think your vifa woof/solid state onken setup is really the issue-- on top of driving the 4592 too low for the horn.. and probably too low for the driver-- which despite the claims of 'going to 300 hz'-- sounds a little too optimistic.
i've heard a b-d design XO on a gainclone, and it had some very strange problems-- i don't know if it was just the person's implementation-- but it sounded like a subwoofer and a full range-- but they never met in the middle anywhere- so i don't know if you've got the same setup. definitely worth experimenting though. you COULD always try the tweet on top- but i don't think it would necessarily fix your problem.
any chance that you could either put together a bass/midbass box with a wider range 12 or 15" driver with higher efficiency and run them both off the same amplifier? it isn't perfect, for certain-- but budgetarily-- it may suit you better- as you're definitely caught in a bad place with what you have!
just a thought--
yrs
d.
> any chance that you could either put together a bass/midbass box with a wider range 12 or 15" driver with higher efficiency and run them both off the same amplifier? it isn't perfect, for certain-- but budgetarily-- it may suit you better- as you're definitely caught in a bad place with what you have! <
This is where it also gets compromised, yet again. There's only so much of a footprint I can accommodate for the bassbins at the bottom. Large 15" high efficiency drivers need big cabinets to get any bass. That's one of the problems.
The next problem is let's say you do get a good 15" woofer to work in the system and I go to single-amp it. Then I need to PAD down the horns from 112 dB sensitivity to about 100 dB sensitivity to match up with the woofer. I now have to go from my 1W/ch flea power high quality SET amp to something that is around 10W/ch. I now need another new amplifier. That's not too far out, I can DIY one up in a few weeks, depending on speed of parts getting to me. But it will be a 300B or 6C33C SET or something like that and not a 45 anymore, and that's potentially a big downgrade in my opinion. Well, some people really think highly of those tubes.
And even still, with a 7W/ch 300B SET amp and 100 dB sensitive speakers, it's still a little short on my goal for high SPL's, but at least this time when it overloads it will be much more pleasant when it happens (those amps overload gracefully). And the bass will be more bloated now, and the bass extension less deep.
Maybe that is the compromise that's required. I'll ponder that over. Thanks for the ideas.
I can see that for uncompromised horn systems it requires a lot of real estate and time and money. I don't have all those things. Maybe the time. I was thinking about how Avantgarde designed their speakers for a small footprint. I used to have DUOs. The subs went low and up to 200 Hz, if I remember correctly. Those subs as I later found out, weren't all that good sounding - pretty slow and muddy compared to my simple Vifa woofer. They should have used just a woofer IMO, not a SUBwoofer. Also, they used their own built-in compression driver in the midrange horn that was really large, like 7" or so diameter. It was integral with the horn which meant it sounded like some vibrating plastic as it compressed the plastic compression chamber. It was so big and had large enough tolerances in there that there was no need for a crossover, it ran full range and only crossed over mechanically by the horn's own cutoffs, not electrically. And that's why it was not as clean as these other compression drivers we're using. And also why it was not as efficient (104 dB vs 112 dB).
At any rate, the Orphean system sounds better than any other horn I've heard so far, except I wished I could play it as loud as those Avantgardes. The standard Orpheans do have plans for a 15" woofer to go with it that isn't horribly expensive and big. But they weren't really meant to go much over 250 Hz, either.
Well, it's fun to think about all the design constraints and what to do about them. Physics is a bitch. It just doesn't let me bend them.
Kurt
sounds like you're ready for a big old horn array, but don't have the space!
i know the rigamarole, man.. i'm pinched into a teeny bungalow, and went with little bass reflex boxes and 500hz horns. it's not a perfect marriage-- but unfortunately-- until i either add a substantial addition to my house or populate the woodshop downstairs as a listening room (in which case all my experiments have to end... noplace else to make things!).. and neither is likely!
well-- good luck-- maybe others have better recommendations!
yrs
d.
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