Hemp FR8C Enclosure Suggestions

[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

[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.

[seventenths]

...after looking at the pic, all I can say is

" HOLY CR*P ! "

What a great excuse to try a SoFH.


7/10

[planet10]

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

[Pano]

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).

[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

[planet10]

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.

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.

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

[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

[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

[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.