What the guys said above. I seem to spend my life designing variations on ML Horns (tapped horns, aka Voigt pipes) and other types of QW & horn enclosures; in your circumstances, that's far from a huge mistake. This design was never about hyper-precision -witness the number of wildly different drivers people have rammed into it over the years. Believe me [us] -that, and room, amplifier output impedance &c variations will all have a much larger effect than what is a relatively small difference for a fairly loose pipe design, and completely swamp it.
Ok then. I'm looking around for screws i can use to mount the speakers, probably use wood screws like what they originally used, but this time they will screw into the speakers and not the chipboard so they'll need to be a size larger. for handiness sake i could let the wires feed out through the bottom port.
but on the other hand all i need do is cut out a square like you all mentioned and use heavy bolts on an outside bracket. then i have no problem mounting and i can turn the square upside down to reposition the speaker close to optimum.
The speaker originally was about half ways down the front pane so if i want it half ways again all i need to do is cut the square plate 3.2cm longer, because that is half of the 6.4cm error.
i could use snap ties or sheep wire though the speaker holes.
but on the other hand all i need do is cut out a square like you all mentioned and use heavy bolts on an outside bracket. then i have no problem mounting and i can turn the square upside down to reposition the speaker close to optimum.
The speaker originally was about half ways down the front pane so if i want it half ways again all i need to do is cut the square plate 3.2cm longer, because that is half of the 6.4cm error.
i could use snap ties or sheep wire though the speaker holes.
I guess that if I were in your shoes I'd want to try attaching the wooden baffle with a thin layer of soft polyurethane adhesive.
don't have much of that around but i've lots of paper to make gaskets. If i have a 2 inch wing outside the hole then there will be lots of contact area to seal it. I'll make it work.
I'm not entirely confident that the metal enclosure isn't going to cause sonic issues. There is no damping what so ever. If this was my project, I would make a pair of small sealed or BR speakers of a known design with inexpensive drivers to test the concept before making a pair of big boys. Just a thought.
The reason I'm skeptical is a subwoofer I built last year. It was conventional ply construction, but the bracing was entirely made from riveted aluminum angle. It had modes that sounded like a steel drum. I was able to save the project with a fair amount of plumbers putty stuffed in the angles.
The reason I'm skeptical is a subwoofer I built last year. It was conventional ply construction, but the bracing was entirely made from riveted aluminum angle. It had modes that sounded like a steel drum. I was able to save the project with a fair amount of plumbers putty stuffed in the angles.
You'll need stuffing, to give your speakers a fair shot. Polyester batting from the inside of a pillow will work. Fiberglass insulation from inside the wall of your home would work.
The amount you stuff up in there - above the speaker - is a variable too. You'll probably want to make your speaker mounting such that you can remove and remount a few times, without it falling apart.
How much? We always start with all of it. Just kidding! They have specs like "0.5lb per cu ft", so you'll need to know the appx volume up there and a scale to weigh it, that can do ounces resolution. Otherwise just eyeball it. Half a pillow? Whole pillow? Something to start with... Dont just mount the speakers in the enclosures "empty" and expect them to work right.
The amount you stuff up in there - above the speaker - is a variable too. You'll probably want to make your speaker mounting such that you can remove and remount a few times, without it falling apart.
How much? We always start with all of it. Just kidding! They have specs like "0.5lb per cu ft", so you'll need to know the appx volume up there and a scale to weigh it, that can do ounces resolution. Otherwise just eyeball it. Half a pillow? Whole pillow? Something to start with... Dont just mount the speakers in the enclosures "empty" and expect them to work right.
Last edited:
That'll work for cabs made of conventional materials. Stuffing had no effect on mitigating the steel-drum effect on my subwoofer project. Making metal cabs, I suspect one need to think in terms of adding mass & damping to the walls themselves (like plumber's putty). I don't think stuffing alone will cut it. This is Hifi bridging into car audio territory.
Right, I've mostly used cheap self sticking linoleum floor tiles or adding a flexible mastic back to [used/scrap/free] ceramic tiles when a lot of damping is required such as a sheet metal sealed sub needs; stuffing is for damping pipe modes and due to sheet metal's much stronger modes, acoustic fiberglass panels [OC 700 series] or extra dense [thick] attic insulation.
edit: http://www.bobgolds.com/AbsorptionCoefficients.htm
edit: http://www.bobgolds.com/AbsorptionCoefficients.htm
Last edited:
We are not concerned with damping the steel itself. It should ring at a frequency that will never get excited by music. The tet will be connecting a speaker and listenng to it.
The damping we are talking about tames the quarter wave resonance, using it to extend the bass.
If the box itself does ring, then startegic panel damping may be called for… maybe even something external wraped around to make it prettier?
dave
The damping we are talking about tames the quarter wave resonance, using it to extend the bass.
If the box itself does ring, then startegic panel damping may be called for… maybe even something external wraped around to make it prettier?
dave
I must say thats weird story. My turntable is full of aluminium and some most critical parts like headshell dont have any damping. I never experienced any "metal" sound.
Maybe that aluminium bracings wasnt attached properly to plywood shell, so you had some sort of rattling between them.
Yes, sufficient air-space damping should deal with the small one.
It is the lower quarterwave modes above the fundemental that is the biggest worry. Dealing with that shoud swamp any issue swith the above.
dave
It is the lower quarterwave modes above the fundemental that is the biggest worry. Dealing with that shoud swamp any issue swith the above.
dave
Yes, rattling is not the best word but point is aluminium is very common material in vibration sensitive audio gear. Turntables, cartridges, microphones, speaker baskets even cones. And it wont turn them into drums.
Its a construction problem, not aluminium that caused such violent interaction between materials.
Its a construction problem, not aluminium that caused such violent interaction between materials.
I know aluminum fairly well. I design machines for it daily.
A harmonic system depend on geometry, mass, stiffness, damping and boundary conditions. To compare the engineered application of aluminum in turntables and microphones to the use of metals in speaker cabinets is absurd. Particularly with no first hand experience.
A harmonic system depend on geometry, mass, stiffness, damping and boundary conditions. To compare the engineered application of aluminum in turntables and microphones to the use of metals in speaker cabinets is absurd. Particularly with no first hand experience.
I think same laws of physics applies for both.
Maybe plywood and aluminium just dont match well.
Maybe plywood and aluminium just dont match well.
I was taking a look at the frugel horn plans and it looks like a folded voigt pipe to me. apart from the addition of the rear horn how is it that it works any better than the latter would.
I dont have experience with Frugels but agree with you its kinda hybrid Voigt construction.
Thats why you should finish that Voigt project, so you could evaluate the bass and decide is it suit your taste.
Thats why you should finish that Voigt project, so you could evaluate the bass and decide is it suit your taste.
It's all about that "back door". You can have just an aperture, a slug of air in a volume or a horn. These will all behave different, in the sound that comes out, how it effects the speaker "as a system", which will of course effect how the cabinet sounds.
The horn is like putting a piece of wood between your hammer and whatever it is you're hitting; it's going to distribute that strike force across a wider area. So when the "puff" of sound squirts out that throat at the bottom, the horn part distributes it evenly across the opening.
This probably has something to do with why the FH cabinets tolerate a wider range of drivers, than some other cabinet using just an aperture port or an air mass load via a (tube or rectangular) volume. I really dont know - that would be my guess.
I'd say that the best cabinet for a beginner DIY is one that tolerates the widest range of drivers and still sounds good. Why? More fun! You can experiment with different speaker drivers without doing so many builds. Which sounds like something you'd want in a cabinet.
The horn is like putting a piece of wood between your hammer and whatever it is you're hitting; it's going to distribute that strike force across a wider area. So when the "puff" of sound squirts out that throat at the bottom, the horn part distributes it evenly across the opening.
This probably has something to do with why the FH cabinets tolerate a wider range of drivers, than some other cabinet using just an aperture port or an air mass load via a (tube or rectangular) volume. I really dont know - that would be my guess.
I'd say that the best cabinet for a beginner DIY is one that tolerates the widest range of drivers and still sounds good. Why? More fun! You can experiment with different speaker drivers without doing so many builds. Which sounds like something you'd want in a cabinet.
Last edited:
It is not a voigt. A oigt as a conical expension the FHs are much more complex.[/QUOTE]
dave