| Hardman |
I recently received a pair of Hemp Acoustic FR8C drivers and am looking for suggestions on a box alignment. I think the final goal is a BIB, but I am looking for a simpler build first to get a feel for the driver and confirm it’s ability before I commit to a BIB. Maybe something with an aperiodic vent (BR for this driver is still quite large) or dipole.
Does anyone have experience with this or the previous version of this driver that is willing to share their design?
Thanks - Chris |
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| pjanda1 |
I would aim for the BIB. I presume you've seen the MLTL's a few threads back. But in the mean time, why not build the little BR that Dan Wiggins designed? The Aperto:
http://www.hempacoustics.com/kits.php
I first used mine in 40L BR's. You can find alignments that work if you tune it low. The group delay will be low too, but the downside is more excursion a ways above tuning. Dan Wiggins knows his stuff. I'm sure there are benefits to the tall baffle, as he says. However, you could also just copy the internal volume and vent in whatever aspect looks good to you. I'd lean towards a wide baffle. You sure won't be disappointed with the BR, and later you'll find the BIB to be a whole different world.
pj |
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| Hardman |
PJ,
Thanks for the reply. I saw the 22 liter design on Hemp’s web site, but thought something larger modeled better.
I settled on a BR of about 45 liters or so with a 3” port. I don’t think port noise will be too much of an issue, so I would really like to put the port on the front of the box (box is about 23.5” tall X 14” wide)? I may reuse this box someday for another application which most likely would be wall mounted. Is there any foreseeable issue with a port on the front of the enclosure? What size port did your 40 liter box use? Suggestions on stuffing/enclosure lining would be helpful too.
I am crossing my fingers, as I have a small SE OTL amp that I hope will be able to drive these speakers when finished. |
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| pjanda1 |
As I think about it, it was a 50L enclosure. The port was 2.5" and it didn't chuff (we're only talking 2mm of excursion here!). It was on the back. I was thinking of doing a more permanent BR, and I did plenty of searching for a consensus on port position. If you can do it, rear ported is safer. However, if you put them on a wall, there is no way it will work. The wall should eliminate the need for BSC, so that is a good thing. A front port has some chance of midrange leakage, even if it doesn't chuff. If you are worried about it, you could do side ports I suppose. If you can use MJK's spreadsheets you could model some different port placements. I wouldn't worry about it. Plenty of folks seem to place ports willy nilly without troubles.
I didn't experiment with damping or stuffing as it was a temporary solution. Don't put much of any "stuffing" in there, or you'll mess with the port action. I damped the walls with thick carpet padding (held on with a combination of Super 77 and PL Premium Construction Adhesive). You know the stuff, a bunch of different foam chunks all glued together: cheap and effective. If you want to get fancy, you could use this stuff:
http://www.rawacoustics.com/item__R...ical_1,821.html
or this:
http://www.partsexpress.com/webpage...k=sonic_barrier
This stuff is mainly to damp the cabinet walls, not to tame standing waves. You might start only placing the material on the back, top and one side, as per GM's recommendation. Too much damping can make it sound dead. I put a double layer behind the driver to help damp the backwave. I used more damping than is ideal, as my cabinet was mainly particle board. Build something decent and you can go easy with it.
Tell me about this SE OTL. It sounds like fun. OTL's strongly prefer flat (and high) impedance curves don't they? Instead of the BIB, perhaps something like the Kenobi would be ideal. You could run the toobs on the Hemps and drive the woofer with something else. Then woofer sensitivity wouldn't matter either.
pj |
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| Hardman |
Here is the scoop on the SE OTL http://www.transcendentsound.com/single%20ended.htm . I have had this amp for a few years now. The Transcendent Sound amp is a great “little” amp, but I have yet to find/build a pair of speakers that really works well with this amp. A few years ago I built some 95 db 8 ohm two way line arrays using Tang Band drivers and an AC ribbon, but in the end the speakers still need a little more head room. I guess a horn setup would work nicely, but I have yet to venture down that path.
Anyway, back to the Hemp… did you use any filter with the BR box or BSC? I plan to make the baffle 14” to 15” wide. In the end these speakers will be driven by a different amp and most likely end up in a BIB (these speakers belong to a friend who has solicited me to help him construct the enclosures). Again, a BR is less involved and cost less than constructing a BIB. The BR boxes should hold my friend over until he is able to scrape some additional cash together for the BIB. Besides, I think he is still working on the WAF as the BIBs are quite large. |
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| pjanda1 |
I didn't use any BSC, but it sure wouldn't have hurt. I used 15" wide baffles fairly close to the floor (12", tilted back) and back wall (1-2ft). I initially had them on higher stands (24") without the tilt, but getting them closer to the floor helped the midbass quite a lot. I had them set on cement blocks such that there was a fairly wide surface extending from just behind the baffle to the floor.
pj |
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| traw |
| what values would i need for a bsc? i have the fr8c's in a 50 liter or so box tuned to 45hz. still a touch hot on the top, want to shift the tone a little. |
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| tinitus |
Dave, thats a nice one
Hardman, I reckon you know that your nice "little" OTL should double its output in 15ohm - I guess it will need som impedance smoothing |
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| Hardman |
| quote: | | Hardman, I reckon you know that your nice "little" OTL should double its output in 15ohm - I guess it will need som impedance smoothing |
Yes I am aware of this (amp should be good for about 4 watts at 16 ohm), but have yet to find a speaker project that takes advantage of the wattage gain.
Update – I didn’t ever build the BR boxes for the Hemp driver, but have instead started the BIB. I plan to use a different amp with the BIB too. I hope this thing is worth all the effort... I mean wood. Looks like the Hemp BIB consumes five 4’ X 8’ sheets of wood! |
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| seventenths |
Dave (P-10)
Would the Demetri be suitable for the fe166e ? I'm looking for a less imposing design than the BIB to couple with a small SET.
Darren |
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| planet10 |
| quote: | Originally posted by seventenths
Would the Demetri be suitable for the fe166e ? I'm looking for a less imposing design than the BIB to couple with a small SET.
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Scott?
I don't think FE168 would drop into Demetri... but certainly a similar design could be made. Each of these monoliths starts from a cooresponding Metronome, The 168 Metronome is the same height as the 167/207/FR8 but a fair bit smaller in the other dimensions.
It is pretty quick to rough up a 1st draft -- from there closing in on an appropriate width to depth raio requires further iteration.
dave |
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| planet10 |
| quote: | Originally posted by Hardman
Yes I am aware of this (amp should be good for about 4 watts at 16 ohm), but have yet to find a speaker project that takes advantage of the wattage gain. |
That is about the same power we are using with the FE126/127 boxes we are always playing with. A pair in series (bipoles) would give 16 ohms.
dave |
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| Scottmoose |
| I suspect not to be honest -not without some series resistance anyway as the Q & Vas on the 166 are too low & high respectively for this sort of enclosure to be an ideal match. I'll have a check when I get a spare minute later today though. If you already have the drivers, & want a less imposing design, then either Ron's A166 is the way to go, or if that's too tricky a build, the Factory 168ESigma cabinet should do the job OK with the 166 mounted. |
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| planet10 |
| quote: | Originally posted by planet10
FE168 |
Oops i read 168 instead of 166... no Metronome for that...
dave |
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| tinitus |
| Hardman .... AER and PHY are 12-15ohm, but also expencive with prices starting around 1000USD each - the PHY should work nice in a simple OB ..... and you gain a little more sensitivity |
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| JimmyD |
I have the current model on open baffle the same size as the old
wharfedale sfb 3. Jaw droping midrange bass deep enough for
me. I have had lowthers alnico, tannoy gold, altec voice of theater
these are a steal and to me a better rounded speaker
best regards
James |
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| tinitus |
Thats hard to beat:)
Any idea about the difference between the old and new version - FR looks different |
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| Nanook |
nice to see someone else try the Hemps on an OB. I did and they are jaw dropping. I encouraged Perry to try a set. He told me that he had tried them (after my experiences were emailed to him) and was floored as well. I truly believe that there is something quite special about the SB3/"JELabs" design
New version FR8C uses a different recipe for the pulp in the cone as far as I know. For the $$ I am not sure it can be beaten (but hey, Dave's 127s are about 1/2 the price and are VERY good). Everyone who has stated that OBs need this or that haven't usually experienced these baffles. With my modifications to the "JELabs" baffles, I feel I have a great "all-rounder". But paint em or stain em first, cause you'll never finish them otherwise. |
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| Hardman |
Hello everyone… It’s been a while since I first started this thread so I thought it fitting to report back on our Hemp FR8C experience thus far.
After some thought we (I am building the speaker cabinets for a friend) decided to try the BIB (GM design). This thing is massive and cost a ton to build (three sheets of BB plywood plus one sheet of particle board), but in the end has been somewhat of a disappointment. It is our opinion that bass is lacking even with such a large cabinet (transient response). Therefore we see little reason to devote so much real estate to such a large enclosure.
Stuffing this speaker has proven to be our biggest challenge. I am unable to eliminate the horn colorations (echo effect). I would love to hear from other Hemp BIB builder’s that are satisfied with the design. There is always that possibility that we did something wrong.
Don’t get me wrong, I am not completely giving up on the Hemp FR8C, but finding a suitable enclosure is a must. One thing for sure, the dynamics are amazing and I was really surprised by how little the FR8C beams. I was also surprised by how much I like the upper end of the driver once it had some time to break in.
Nanook’s proposal for a JELabs open baffle is tempting, but my understanding is this design requires specific room placement and I am not sure this will bode well with my friends listen room/family room.
Planet10‘s Demetri is looking more and more like a possibility. What are the benefits of this design vs. an MLTL or BR enclosure?
I am convinced the bass level my friend is looking for is not going to be obtainable with the Hemp driver alone regardless of design, so finding something that will mate well with a subwoofer or large 15” pro driver is a must (we prefer the sub idea over the 15” pro driver approach).
I am tempted to build a simple sealed enclosure and see what type of results we get and then maybe try to incorporate an aperiodic vent. Anyone tried this route?
So what should we try next? I am open to any suggestion, I just want to be sensitive to the fact that my friend has already spent a good amount of money already on wood that hopefully we will be able to salvage somewhat.
On a side note, the BIB/Hemp speaker work with my SE OTL amp (not to ear piercing levels, but doable). In fact, this was really the first time I was able to hear a difference between this amp and my solid state amp. With this speaker the tube amp was by far the better choice. If only those PHY speakers weren’t so expensive (I know others who have my amp that use this driver)…
Thanks – Chris |
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| seventenths |
wierd... I would think that bass would be a non-issue with BiBs and the hemp-8. My fostex 166e units have considerable bass (I play quite a bit of dub/bassy music). Interesting... Hemp-8s are lined up for my next large speaker project, so I'll stay tuned in to this thread to see what the experts suggest.
good luck
7/10 |
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| Hardman |
I guess I had better clarify my above Hemp BIB comments a little more. Don’t get me wrong the BIB design is able to produce bass. In fact, when the Hemp driver first arrived I built a small baffle for each driver and then mounted them and had a listen. There was no bass at all, and the overall sound was not that good (this was a very small baffle, about 12” square). The comparison between the BIB and small open baffle is like night and day.
Maybe we have unrealistic expectations. Most of our experience has been with the more traditional closed/ported speaker designs. One of the end goals is a stronger, transient, bass response. You know… the kind that hits you in the chest. Bass aside, the driver has a bunch of other aspects that we both really like and so the search for a new cabinet design.
Here is a photo of the BIB next to a Jordan MLTL. As you can see the Jordan is quite a bit smaller and less efficient, but at similar SPL levels is able to match the bass output of the Hemp BIB design.
In the end it really isn’t the bass that is pushing us to look for another design, but rather the cabinet colorations of the horn. Maybe we just don’t like horn speaker or maybe we still need to play around with stuffing. I don’t really know, this is my first attempt at a horn speaker. One thing for sure I don’t really want to climb inside this speaker again (yes that is right; the Hemp BIB is so big I am able to fit inside the cabinet).
I guess with any speaker design there are tradeoffs. As stated above, I may try a sealed box just to see what effect it has on the sound coming from the Hemp. If I am able to keep the dynamics of the BIB and lose the “echo”, then we will be getting somewhere. |
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| seventenths |
...after looking at the pic, all I can say is
" HOLY CR*P ! "
What a great excuse to try a SoFH.
7/10 |
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| planet10 |
| quote: | Originally posted by Hardman
One of the end goals is a stronger, transient, bass response. You know… the kind that hits you in the chest.
In the end it really isn’t the bass that is pushing us to look for another design, but rather the cabinet colorations of the horn. Maybe we just don’t like horn speaker or maybe we still need to play around with stuffing. |
For chest thumping bass, you really need to move some air... a couple CSS 12 or 15" Subductions would do the job. Scott & i have done a couple designs for the 12" that would make your BIBs look like your Jordans size wise :) The bif 15" boxes should be even bigger.
The ripple i heard in the BIBs was what inspired Karlson slot in the iBIBk -- some people are sensitive the ripple (me. you & your buddy it sounds like) and some aren't. In terms of horns, the BIB is pretty crude, so don't judge all horns by it.
dave |
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| panomaniac |
Well I've been banging my head againt a pair of FR8c on open baffle for over a week. It's a "Lampizator" style baffle. About 15" wide, 46" tall. Active bass on the bottom.
Yeah, the FR8 does beam less than I expected, but it does beam, just like any 8"FR is going to. But I'm comparing it to an Altec 811 horn, which is much wider.
On the 15x45" baffle, the FR8c has NO low end, none. A lot like the 12" square baffle that Hardman mentions. I had hoped for more, but it rolls off fast under 300 Hz, which leaves it sounding much too bright.
Been doing "Jedi mind tricks" on it to tilt the response down a bit. Simple inductors or an RL parallel shelving filter. So far it's good, but not great.
Maybe I'll have to try the JELabs baffle. On the tall, thin baffle I get no joy (yet). |
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| Hardman |
Dave - Thanks for the reply. Good to hear that not all horn speakers sound like the BIB. My faith in other designs has been restored. To be honest I didn’t really read much about the BIBs before building them. Most of the research was done by my friend. I mainly provide the shop and a second set of hands for assembly. I have always wanted to try something horn like so this was a good learning experience if nothing else. There were many plusses offered by the BIB design, but the above mentioned “extras” proved too much for our liking.
Do you think a sealed box is going to lose some of the dynamics offered by the BIB? If so what other type of a design do you propose? Above you suggested the Demetri, still leaning this direction?
What is an IBIBK? I assume it is an offshoot of a BIB?
I too have played around with the CSS subwoofers and really like them. I have both drivers currently. Just need to find some time to put them into a box. I know you are a fan of push-push enclosures, any designs for the SD12 or SDX15 (I guess if I weren’t so lazy I could just look on your site)?
Thanks,
Chris |
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| planet10 |
| quote: | Originally posted by Hardman
Do you think a sealed box is going to lose some of the dynamics offered by the BIB? If so what other type of a design do you propose? Above you suggested the Demetri, still leaning this direction? |
Demetri might suit... it seems to want a big room. It was designed to be "compact and go againt a wall) Bruce (or a Chang variation) is where my mind goes 1st.
| quote: | | What is an IBIBK? I assume it is an offshoot of a BIB? |
i for inverted, k for Karlson slot. This one was for FE127/126 so inverting it to floor load the mouth had some big advantages, and the Karlson slot was a shoy at smoothing out the ripple.
Besides the big BIB thread it has its own thread. A couple have been built. It hasn't got to the top of our queue yet.
| quote: | | I too have played around with the CSS subwoofers and really like them. I have both drivers currently. Just need to find some time to put them into a box. I know you are a fan of push-push enclosures, any designs for the SD12 or SDX15 (I guess if I weren’t so lazy I could just look on your site)? |
I haven't posted any push-push designs yet. I just finished drawing up a set of sealed p-p SD12 (customer wants a stereo pair), and i have the data to do the small SDX15 push-push TL (~33 ft"3). I have a place to put a stereo pair of those. Have to rent a drywall lifter to get them up to the ceiling of my shop (which has a common wall with the hifi/living room space.
dave |
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| Scottmoose |
A Chang version? :) This should work. Chamber is basically the MLTL I did a week or so back for the FR8C, slightly shortened. Internal dims. Chamber 42in x 10.5in x 14in (HxWxD). Driver positioned in the middle of the front baffle. It'll need some bracing, & that useful triangle on the rear panel. Slot vents at the back of the top & bottom panels, 15mm deep, 102mm long, firing into two 15in tall flared vents. As far as I can tell from MathCad (keeping the software limitations in mind), it looks like it should do pretty well. Chamber needs lining -top, bottom, one sidewall & the back (keeping the vents clear).
Re the other boxes, Dimitri scores over the MLTLs if you like a wide baffle, & TQWT always sound subjectively a little different to a straight pipe, even though FR plots might look similar -seems to be mostly in the midbass where they seem to have a little more punch, at the price of a touch more ripple.
I'm surprised you didn't find the BIBs giving great LF -they should kill most cabinets in this respect. How did you damp them? Admittedly, they're not for everyone -some people are sensitive to the ripple, as Dave says.
Scott |
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| pjanda1 |
I, too, am surprised that you don't find the quantity of bass from the Hemp/BIB to your liking. I wish I could give a little of my bass away. Different rooms, different strokes. I still haven't gotten mine outside to finish.
Just a couple of days ago I was pondering hauling them out and cutting a K-slot in them for a change. Dave or Scott, am I right in thinking that a K-slot could diminish LF gain a bit and reduce ripple? I don't find the ripple that objectionable, but I am overloading my room. A K-slot would look cool too.
pj |
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| Scottmoose |
| Right. How much of a ripple reduction it'll give, your guess is as good as mine, as no-one's ever figured out a formula for accurately sizing Karlson slots. But it certainly should help a bit. Plus, as you say, they do look good. :) |
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| GM |
Greets!
Well, this sucks! Apparently the pipe's 3rd harmonic dip is a bit much and combined with the driver's published broadband lead guitar 'shout', even a BIB's prodigious bass sounds weak, so at minimum some BSC is required, though a series notch filter to tame the ~1.5 - 15 kHz 'shout' would be my first choice and dial in a bit more damping as required to flatten the in-room response.
WRT the hollow sound, read mine and Lonnie's responses in the BIB thread about how he damped his: http://www.diyaudio.com/forums/sear...chid=1163318712 If you can't make this work combined with the filter and/or some BSC, then regrettably a BIB system isn't going to work for ya'll.
FWIW, here's my take on a MLTL based on published specs, though it will need the notch filter and much more BSC than the BIB or it will sound like it has no bass at all based on your stated listening impressions:
L = 57.5"
CSA = ~113"^2 (recommend 13.5" W x 8.375" D)
zdriver = 20.875"
zport = 45"
vent = 4" dia. x 0.75"
density = 0.2 lbs/ft^3
GM |
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| Scottmoose |
Love that tickled up bass Greg. :)
I must be some kind of idiot! I'd clean forgotten the rising response of the hempster. Still, assuming there's some room-gain going on, you'd think that it'd balance out as that monster you came up with is ~flat (or as much as these things ever can be) down to 30Hz.
BTW -a Zdriver position of 0.2 line length rather than 0.217 seems to reduce the depth of the 3rd harmonic null somewhat. |
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| GM |
Thanks!
As smoothed as the factory plot is, I'm betting it's got some spikes in our acute hearing BW that only a lead Heavy Metal guitarist would like and I assume Chris has way over-damped the BIBs trying to rid it of its major resonances judging by his perception of the little Jordan pipe being ~its equal WRT bass reproduction.
You've mentioned this before, so have you actually compared the two in-room? I must admit I'm skeptical since this is a ~zero throat area pipe that I've found require gross driver position changes to notice any obvious difference one way or another, at least in the large mass loaded variants I've experimented with where Av = ~Sd regardless of Sm used. |
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| peterbrorsson |
Dave, Scott GM,
Don't you think these huge panels would create resonances also?
I made the "hand clap test" in the driver opening when they were undamped. Of course you get echo when undamped. But this got me thinking of my spare room that was unfurbished for a while. Hand clap effect prominent here. Now there's shelves for the childrens toys on one wall. Guess what, echo is gone, despite not much of soft material in the room.
In my naivity I ask, would it work in a BIB without change of other physical properties of the horn. Of course I'm talking of smaller sections of different lengths of shelves in the horn path.
Cheers |
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| Alethos |
I guess I had better chime in while the chiming's good and since i'm the other half of Hardman's posts. Let me 1st put you into my frame of ear.
Almost 2 years ago I approached Hardman about building some speakers. He asked if i'd be willing to guinea pig a design he'd read much about and was interested in. I consented and we built Jim Girffin's Bipole ML-TL (based on GM ML-TL) for the CSS FR125S. I can't explain the euphoria I felt when we hooked those puppies up. The bass that came from blew me away regardless of driver / cab size. Not only was it there, but it was there in spades...and not the muddy bass I had heard all my life from Circuit City (and the ilk) listening rooms but clean, full, rich, warm, and...flowing bass. To my ears, they were the best speakers I had ever heard. Some complain about the top end being a bit lackasidasical. I've always been overly sensitive to high frequencies so I didin't mind (or notice much for that matter). What they lacked in frequency response was more than compensated for with what they offered. I loved them with one caveat. They didn't play loud enough. Fast forward to now.
I chose the Hemps for the fact that since I found out about them I had often read how great they were supposed to be with rock (probably what I listen to most), boogy-ing with an unprecedented "organic" sound...I just had to try them. As for the enclosure the BIB seemed like the perfect fit. I chose it with the hopes of acheiving the same (or very near) bass of the FR125S set but with much higher SPLs available at my disposal plus a peerless natural sound. Here's what I told a friend what I thought about the sound once we built them...
"Hardman and I first put the hemps in an open baffle setup...they sounded pretty terrible. Once the BIBs were together we were surprised at how frickin awesome they sound...with a couple of caveats. The lf extension, while there and also loud at times, is anemic compared to the other freqs being produced. Certain higher freqs are harsh, Hardman and I chalk that up to 2 things, the driver itself and also probably reflections from the direct backside of the speaker. The final thing is there is an echo-y-ness about them that is hard to describe. Colorations (we think) inherently produced by the cabinet. Without spending countless hours getting the stuffing exact I don't think that problem is going to go away. If even then. On the plus side, certain mids sound better than I think I've ever heard. There is an open and natural sound to these drivers that is unmatched."
That's the best way I can describe the bass...there but anemic. Add to that the colorations and I'm afraid these cabinets are going to have to go. I'm glad we built the BIBs but like Hardman said...expensive endeavor that we were disappointed in.
Sorry for my drawn out post but I wanted to give those in the know an idea of where I was coming from, what it is I'm looking for and where I'm at right now. So my question is...with the hemps (because i do believe i'm sold on their sound sans the colorations these BIBs are producing) how do I achieve that bass I'm looking for? Ultimatley I'll probably try the OB design but I can't afford a sub right now (space or money) so how do i milk these dudes for all their LF worth? I'm rather drawn to the Demitri as opposed to a simple BR design simply based on the success of the previous MLTL we tried but like Hardman said (and as demsonstrated by simply building the hemp BIBs) I'm open to suggestions. |
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| GM |
Greets!
Nothing you've said changes my opinions/suggested solutions and the perceived harshness, etc. just confirms to my satisfaction that the driver needs some form of serious EQing regardless of box alignment, though multiple drivers and/or true BLH loading would somewhat reduce the amount required.
Bottom line, like most FR drivers it's basically a wide BW mids driver that needs a sub and super tweeter system for the type of max performance you desire from it.
GM |
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| Scottmoose |
| quote: | Originally posted by GM
As smoothed as the factory plot is, I'm betting it's got some spikes in our acute hearing BW that only a lead Heavy Metal guitarist would like and I assume Chris has way over-damped the BIBs trying to rid it of its major resonances judging by his perception of the little Jordan pipe being ~its equal WRT bass reproduction. |
Yeah, that makes sense about the plots. Be interesting to see some unsmoothed measurements. I'm betting these things must be crammed with material if the Jordan's are apparantly matching them for extension.
| quote: | | Originally posted by GM You've mentioned this before, so have you actually compared the two in-room? I must admit I'm skeptical since this is a ~zero throat area pipe that I've found require gross driver position changes to notice any obvious difference one way or another, at least in the large mass loaded variants I've experimented with where Av = ~Sd regardless of Sm used. [/B] |
Nothing that I'd call a proper test. I knocked together a couple of MDF test boxes last year to try a few things out & this was one of them. There seemed to be a small difference. They were only in the garage though, rather than properly sited in the house. It's more an observation based on the 1/2 space sims that the nulls seemed to be better controlled, especially the 3rd harmonic, which seems to be ~ 3-4db less with the 1/5 line length placement. Whether that'd be audible in-room or not when damping's in place I don't know. You're probably right Greg, but anything that might help's worth a shot, right?
Something's just occured to me -exactly which driver are we talking about here? The FR8? Or the new FR8C? The published specs are different. Assuming both are accurate (I'll believe that when I see it) the old driver had a lower Vas 88 litres, rather than the new unit's 95.5-odd. Motor seems the same, but the old unit's (equally smoothed out) response looks like it has slightly less of a rise. 2KHz: new unit ~99db. Old unit ~95db. Cone material's changed too. |
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| planet10 |
| quote: | Originally posted by Alethos
Here's what I told a friend what I thought about the sound once we built them... |
Your description seems to jive pretty good with GM's theoretical analysis. The bass is lacking because most everything is plateaued up.
This plateau can only be EQed out... this is a standard trick that goes back to at least to Henry Kloss (at least the 1st time i encountered it). Add a parallel RLC shelving filter. The L controls where the LF are let loose, the C where the top is. The size of the R determines how much the mids are shelved down. (with your sensitivity to the top you may get away without the C, in which case it becomes what we know today as a BSC filter). I will go to great lengths to avoid passive filters, but sometimes you just have to bend. An added filter like this turned the Blue & Yellow specials i built from a table radio type sound to kick-*** (and made them happier with the Pioneer AV receiver they are being used with -- my godson (& his mother) love them)
As to the ripple, since you are prepared to abandon the box, cutting a k-slot would be a beneficial experiment to the entire community.
The only was to really deal with any spikes in the FR (the stuff the heavy metal guys like), is likely going to be cone treatment, and that is unreversible and at this point approachable only in very broad, generalized, non-specific strokes.
dave |
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| planet10 |
| quote: | Originally posted by GM
FWIW, here's my take on a MLTL based on published specs |
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| planet10 |
| quote: | Originally posted by Scottmoose
A Chang version? :) |
For Hemp Acoustics FR8c. Then it must be Tommy Chang :)
Drawing underway. Will post once some details to make the flared vents fit into the box are settled.
dave |
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| Hardman |
| quote: | Originally posted by Scottmoose
Something's just occured to me -exactly which driver are we talking about here? The FR8? Or the new FR8C? The published specs are different. Assuming both are accurate (I'll believe that when I see it) the old driver had a lower Vas 88 litres, rather than the new unit's 95.5-odd. Motor seems the same, but the old unit's (equally smoothed out) response looks like it has slightly less of a rise. 2KHz: new unit ~99db. Old unit ~95db. Cone material's changed too. |
We are using the new Hemp driver - FR8C.
| quote: | Originally posted by planet10
Add a parallel RLC shelving filter. The L controls where the LF are let loose, the C where the top is. The size of the R determines how much the mids are shelved down. (with your sensitivity to the top you may get away without the C, in which case it becomes what we know today as a BSC filter). |
For kicks I think I will apply some BSC and see what effect it has on the speaker. I have a Vidsonix crossover box that should enable rough BSC for one speaker (mono). I am only going to be able to get the L value for the circuit from the crossover box. I have a few resistors that hopefully I will be able to series/parallel to get the correct value. If someone is feeling helpful, a double check on my BSC math would be welcomed. Baffle = 16.25" and Re according to Hemp’s specs is 6.2 ohm.
dB - R - L
1 - 0.8 - 0.4
2 - 1.6 - 0.9
3 - 2.6 - 1.4
4 - 3.6 - 2.0
5 - 4.8 - 2.7
6 - 6.2 - 3.5
| quote: | | As to the ripple, since you are prepared to abandon the box, cutting a k-slot would be a beneficial experiment to the entire community. |
I would love to give back to the community. What modifications do we need to make to the existing cabinet? |
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| Alethos |
Thanks for all your guys' input. No harm in trying some BSC before we disassemble (hahaha more like trash?) the BIBs also, passive filtering and K slot? Sure, I'd love to give back to the community in any way I can.
Tommy Chang...hehehe |
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| panomaniac |
OK, my 2 cents worth.
A simple LR shelving filter does not work well on these drivers. Why? Rising impedance. You will need a Zobel circuit to tame it. Otherwise all you do is dish out the mids - I know, I've tried.
I have built a variable BSC filter for the FR8c. So far values of about 15R+1mH sounds best on my open baffles, but it's not ideal. No Zobel on this one.
As for the rise seen in the new FR chart, who knows? The grapevine tells me that whizzer cone drivers are notoriously hard to measure, so who knows what was done to that graph or how it was measured. My measurements do not show that rise at all on OB. Just a 2.5K peak that may be voice coil related. Otherwise pretty flat out to about 14K. But I do not have an ideal measurement set up, so I could be all wet.
So far, I've been able to make the driver sound good, but never great. As Greg says, it's a wide BW mid that needs help at the top and the bottom. That's what I'm trying to do, but it ain't easy. :( |
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| fred76 |
| quote: | Originally posted by Hardman
We are using the new Hemp driver - FR8C.
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Hmm, if the older FR8's parameters significantly deviates from the new FR8C's then it might also add to the anomalies you're hearing. The design on Zillaspeak is for the older Hemp driver. |
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| planet10 |
Tommy Chang
up on Frugal-horn.com (as soon as tidy the web page a bit more)
SketchUp uploaded to the warehouse
dave |
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| planet10 |
| quote: | Originally posted by Hardman
I too have played around with the CSS subwoofers and really like them. I have both drivers currently. Just need to find some time to put them into a box. I know you are a fan of push-push enclosures, any designs for the SD12 or SDX15 (I guess if I weren’t so lazy I could just look on your site)? |
I just added ShadowSD12 plans to the Spawns page -- an excellent companion woofer for Tommy Chang (here a pic with Curvy Chang)
dave |
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| planet10 |
| quote: | Originally posted by Hardman
I would love to give back to the community. What modifications do we need to make to the existing cabinet? |
1st you need to choose to add a single Karlson Slot on the back or 2 -- 1/2 slots on the sides (this seems to make most sense. Then download the excel Karlson Slot calculator and play with some slots
http://melhuish.org/audio/download/?C=N;O=D (K-Slot.xls)
Not a lot is known about the proper sizing so you guys are in an ideal opportunity to 1st/ see how well it works, 2nd/ get a bit of a handle on sizing. (i'd start small and grow the slot until it is too much -- then you can burn the boxes :))
dave |
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| GM |
Greets!
Thanks for the drawing Dave! I take it you have quite a library of designs to choose from to make them quickly now. Cool!
GM |
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| GM |
| quote: | Originally posted by panomaniac
A simple LR shelving filter does not work well on these drivers. Why? Rising impedance. You will need a Zobel circuit to tame it. Otherwise all you do is dish out the mids - I know, I've tried.
As for the rise seen in the new FR chart, who knows? The grapevine tells me that whizzer cone drivers are notoriously hard to measure, so who knows what was done to that graph or how it was measured. My measurements do not show that rise at all on OB. Just a 2.5K peak that may be voice coil related. Otherwise pretty flat out to about 14K. |
Greets!
Good to know!
A previous version of this driver had a very low measured Le, so it seemed safe to assume the new model would have the same basic motor, but if this measured rise is due mainly to inductance, then yes, a zobel is required before any BSC or notch filter design be calc'd.
Hmm, on axis hasn't been a problem for me, but off axis is another matter altogether, so the driver ideally needs to be on a swivel to get repeatable results. Still, this doesn't account for yours not having the rising response and the BIB would tend to have too much bass in-room if his were ~flat to 14 kHz.
GM |
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| GM |
| quote: | Originally posted by planet10
Not a lot is known about the proper sizing so you guys are in an ideal opportunity to 1st/ see how well it works, 2nd/ get a bit of a handle on sizing. |
Well, if the early adopters got it right, then ~half of the sides tapered all the way to the bottom needs to be cut out: http://home.planet.nl/~ulfman/files/poppe_kcoupler.pdf |
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| Hardman |
Looks like the Tommy Chang is 73" tall. No reusing BIB parts in this desing. We have one full sheet of 4' X 8' BB left, but it will take two to pull this design off. Hummm.
| quote: | | Originally posted by planet10 I just added ShadowSD12 plans to the Spawns page -- an excellent companion woofer for Tommy Chang (here a pic with Curvy Chang)dave |
Ok, I am signing up for this one! I am a little hesitant going horn again, but willing to give it a shot. Back around the first of the year I built an SD12 sealed (.57 or so Qtc) sub for another friend. I liked this sub so much I ordered a driver for myself. I have been sitting on the driver for a while waiting for such a design as this to come along. I like a tight transient bass response, and dislike the bass boom from ported designs. My limited experience with MLTL has been positive. What will Shadow sound like?
| quote: | Originally posted by planet10
1st you need to choose to add a single Karlson Slot on the back or 2 -- 1/2 slots on the sides (this seems to make most sense. Then download the excel Karlson Slot calculator and play with some slots
http://melhuish.org/audio/download/?C=N;O=D (K-Slot.xls)
Not a lot is known about the proper sizing so you guys are in an ideal opportunity to 1st/ see how well it works, 2nd/ get a bit of a handle on sizing. (i'd start small and grow the slot until it is too much -- then you can burn the boxes :))
dave |
This K slot thing is starting to sound like work :eek: :confused: .
Chris |
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| planet10 |
| quote: | Originally posted by Hardman
I am a little hesitant going horn again, but willing to give it a shot....I liked this sub so much I ordered a driver for myself. |
Keep in ming that a BVR is really a bass reflex done up in horn-like clothing. Also note that anyone who wants the Subduction drivers i can supply (and discuss a forum break)
dave |
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| panomaniac |
| quote: | Originally posted by salas FR8C parametres measured by me.
... |
Thanks! My meter says 0.5mH as opposed to your 0.35
I think my meter measures at 400Hz, I'll check.
Will try to do some T/S measurements here tomorrow. |
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| salas |
| Mine is Woofer Tester II digital interface I-source thing. It has proved reliable by now. |
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| bigdh31 |
I have been listening to the FR8 for 8 months and have been enjoying them. I just built a 78 liter box with a 4 inch wide by 3 inch port tube.
They do sound bright and at times irritating for the first 100 hours or so. After that they sound more balanced and the bass becomes pretty decent. If you are evaluating an enclosure and/or BSC circuit you need to burn in the driver well first.
I have been driving them with a 41hz Amp6 and am very satisfied with the combo. I did end up using a rear mounted fill tweeter to bleed a little energy out of the FR8 above 10k and to help with the beaming issue. I just put a 1 mfd capacitor in series with the tweeter. I did not use any BSC circuit with them. |
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| planet10 |
| quote: | Originally posted by bigdh31
I have been listening to the FR8 for 8 months and have been enjoying them. |
So you have the old version then? I don't think FR8c has been out that long.
dave |
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| Nanook |
My set are the "C" version, and I got em at Christmas (er "holiday" time) '06 for review. I bought the test samples.
I must agree that they do sound a little shrill initially, but smooth out after 100 hrs+.
The c37 has helped (I think) as have the phase plugs. My super secret reversible EnABLed speakers sound quite excellent driven by my Amp 6 Basic :) |
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| planet10 |
| quote: | Originally posted by Nanook
My super secret reversible EnABLed speakers sound quite excellent driven by my Amp 6 Basic :) [/B] |
You've EnABLed them?
dave |
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| Nanook |
I did a reversible physical mod that results in what I believe to be the EnABL process. Can't afford to mod drivers (unless the results are completely known), but can modify their environment ;)
As the EnABL process or result effectively minimizes cone/surround defraction problems...I shared my idea with BudP and am still "testing" |
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| panomaniac |
Hmmm... Well I did break them in for several days running tones on the workbench. I guess they are ready to go. They have a number of hours on them after that, but I didn't count. :)
Will keep working on them. |
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| bigdh31 |
| quote: | Originally posted by planet10
So you have the old version then? I don't think FR8c has been out that long.
dave |
Yes, they are not the "C" version. They must not be that different. The floor stander plan on the Hemp Acoustics web site is not that different from what I did. They went taller and narrower than my design. Mine ended up 40 inches tall, 16 inches wide and 12 inches deep. The front panel is doubled. I used the Boxy CAD spread sheet to come up with the design. |
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| Scottmoose |
'Must not...' don't bet on it. ;) Odd things happen.
All of this seems to confirm GM's suspicion that these new units in particular need their response from about 1.5KHz or so shelving with some form of Eq, be it active or a RLC circuit, plus a zobel, if they're going to sound balanced in a back-loaded cabinet. |
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| GM |
| quote: | Originally posted by panomaniac
Thanks! My meter says 0.5mH as opposed to your 0.35
I think my meter measures at 400Hz, I'll check.
Will try to do some T/S measurements here tomorrow. |
Greets!
You need to calc the zobel based on the inductance at the XO point, which for a FR is ~20 kHz, so measure its impedance (Zxo) at 20 kHz (Fxo), then calc its inductance:
Le (mH) = ((Zxo^2 - Re^2)^0.5/(2*pi*Fxo))*1000
Hopefully this will allow you to use a simple R/C shelving network.
GM |
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| panomaniac |
OK guys,
I've been looking at a ML-TQWT for the Hemp FR8c.
There is one over in the Aperto thread. that's a straight box.
So I have a few questions:
Using Martin's ML-TQWT model, the FR8c models pretty well with a line length of ~60 to 70". Can this be folded?
MJK's model is for mass loaded straight pipe, but does it matter if it's folded?
The ML-TQWT design around the 'net seem to all be straight pipes. Why?
So it's really 2 questions. - Can the ML-TQWT be folded?
- Can the mass loading and round port be used with the folded line?
If so, it looks (on paper) like the FR8c could work well in a box no taller than 35", which would be great. Any ideas? |
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| Scottmoose |
An MLTL is a straight, untapered pipe with mass-loading. An ML TQWT is a pipe that tapers toward the throat, with mass-loading. The latter is sometimes useful as it gives some extra gain, but it needs to be longer than a stright pipe for the same Fp (pipe tuning). In most cases, a stright pipe gives as good, or better, results, but the TQWT is still a useful card to play for those units that don't suit a straight line as well, or if you have a particular goal in mind.
A tapered pipe can indeed be folded if an unfolded line isn't possible in your room, and yes, you can still apply the mass-loading. |
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| vinylkid58 |
| quote: | Originally posted by panomaniac
If so, it looks (on paper) like the FR8c could work well in a box no taller than 35", which would be great. Any ideas? |
Check out Demetri in the Planet_10 box library.
Jeff |
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| panomaniac |
Thank you, Mr. Moose!
I should be careful in my use of "straight pipe." I meant "not folded" as opposed to "straight walls. " Will use "folded" or "not folded" from now on. Even a straight TL could be folded, I've seen it done.
So... Using Martin's ML-TQWT calculations, no worries about folding it. And use the same stuffing and port, right?
The folded pipe would have much less leeway in port placement, unless the port was at the back or side.
| quote: | | Check out Demetri in the Planet_10 box library. |
I have, and it's a little bigger than I'd like. What got me thinking is that a smaller box models just as well, so where's the catch? |
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| Scottmoose |
Right -damping and vent remain the same.
Why use a larger cabinet? Better sonics. Even if the FR looks similar, bigger is better; it will sound less strained, and have better dynamics than the smaller volume enclosure -something GM taught me, and he's not kidding. The more air you've got working for you, the bigger, the more effortless and dynamic the sound will be.
Look at it this way: I could get 350bhp out of a 2 litre tubocharged Cosworth engine, no sweat. Would it be as effortless as a 389 V8 with the 3x2 carb option in a MK1 Pontiac GTO (one day, I shall own one), rated at ~the same power? Nope. As a Brit, I'm not supposed to voice such a classic U.S. phrase, but it's fundamentally true: there's no substitute for cubic capacity.
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| panomaniac |
| quote: | Originally posted by Scottmoose
As a Brit, I'm not supposed to voice such a classic U.S. phrase, but it's fundamentally true: there's no substitute for cubic capacity. |
Yes, don't I know it. That's why I love the big Altec boxes and the Onken W. It's always a matter of compromise. Given the room, I'd go big. But my little cottage just doesn't have the room for big boxes. So cheat, I will. Or at least try.
My neighbors had a giant plywood crate delivered, it's still in their yard. Biggest damn plywood box I've ever seen. 8ftx4ftx15ft. HxWxL. That's a 480 cubic foot box. Maybe I can make speakers out of it, and set it right outside my living room windows. :clown: |
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| planet10 |
| quote: | Originally posted by panomaniac
have, and it's a little bigger than I'd like. What got me thinking is that a smaller box models just as well, so where's the catch? |
Mr. Moose did the modeling on that... he has done so many that i just trust him... Demetri started out as a folded ML-V and ended up as a small, folded, mass-loaded BIB.
dave |
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| panomaniac |
| quote: | Originally posted by Nanook
I truly believe that there is something quite special about the SB3/"JELabs" design |
I would not have believed it, but I tried it tonight. It works!
OK, the details:
Whipped up a pair of the Warfdale/JELabs style baffles out of double thickness cardboard. Did it at work where there is plenty of room - maybe too much room.
The amount of low mid the baffle adds is surprising. And they will play loud! Imaging was decent, but not extraordinary. No real low bass, of course, but good solid mid bass. A lot of the shout was gone.
Tonal balance was still mid heavy, but better than I had hear it before on small baffles. What really helped was the loudness button on my Sansui receiver. Pulling down the mids was a big help.
Some caveats:
Huge room. The baffles where at least 15' from the nearest wall. Room is huge. 40x50x22 LxWxH. I've been in smaller barns. :) That can't help room gain.
Cardboard baffle. Sounds like... yeah, cardboard. I think that was the main annoyance. And the cardboard must pass LF like a sieve. Can't help the tonal balance.
So I can see how this driver on a real baffle in a modest size room could sound very good. Better yet would be a 15" or 2x12" drivers for bass with the FR8c for highs and mids. Should be worth a try.
Can anyone who has gone from a cardboard baffle to a wooden baffle tell me what differences you found? |
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| panomaniac |
Part Deux.
Tried them at home before taking them apart. Much too big for my small and crowded living room, but they work much better in the small room.
Bass is better, even though I don't have tons of room gain (open windows and doors). Imaging is also much better with closer walls. In fact imaging is quite good. A little low, but the drivers are almost on the floor. Images seems about 5 feet high. Rear firing tweeter now has some use with wall reflections
They get darn loud with little power! Still a bit shouty, but that's probably the cardboard baffles. If a passive contour filter were needed, there seems to be plenty of sensitivity to trade off.
If you have the room, this baffle with big bass drivers and the FR8 as a mid/high should be killer! Just the FR8 by itself really rocks. |
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| jackinnj |
Here's Vadim's BLH "Horn Project" using the FR8C. A kit is available from E-Speakers and a complete write-up is given at this URL:
http://www.e-speakers.com/Pdf/vadim-infopack.pdf
If someone is going to plug in the values (they can be approximated from the drawings -- they aren't specifically given) it would be interesting to see how it performs on Martin's BLH Mathcad worksheets. |
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| lousymusician |
| quote: | Originally posted by jackinnj
Here's Vadim's BLH "Horn Project" using the FR8C. A kit is available from E-Speakers and a complete write-up is given at this URL:
http://www.e-speakers.com/Pdf/vadim-infopack.pdf
If someone is going to plug in the values (they can be approximated from the drawings -- they aren't specifically given) it would be interesting to see how it performs on Martin's BLH Mathcad worksheets. |
This design was originally offered for the FR810DIY, the predecessor of the current FR8C. The driver parameters in the write-up are for the earlier driver. The newer driver has a larger Vas and lower mms - I don't know how much that will affect the performance of the system.
Bill |
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| jackinnj |
The world according to Martin (MJK):
"While in general higher Qtd drivers are not looked upon as being particularly high fidelity, the use of a higher Qtd driver in a severely compromised back loaded horn may have some real benefits".
You can see the entire article on MJK's website:
http://www.quarter-wave.com/Horns/Back_Horn.pdf |
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