You could also make it a flat baffle with a part that can be bolted on that holds the tweeter and mid, with a fixed size cabinet size behind it that is part of the structure. Make a double front pannel where there is a cut out for the treble section, and a panel that is a bit larger so you can bolt it on the woofer cabinet a the inside panel of the front bafle. Look at how Neumann does it with the KH420 today. the removable front panel is bigger than the hole in the 20nd panel of the front baffle so they got material to connect it. Both panels could be 15mm ply (so 30mm in total) while the rest of the cabinet is 18mm ply. (just an example. In between you use a rubber or other air sealent. A bit like in this schematic drawing where the dotted line is the insde cut out and the full line is the outside cut out.
It's early, but have you determined a range for this effect and derived a baffle configuration to achieve it? Have you or someone else you've studied done this previously?
Yes this is broadly the idea but there are details to sort out. If the removable panel is to contain different drivers and waveguides and the half baffle is passively isolated how to stop the internal pressure from the woofer moving the half baffle around. A custom second panel for each configuration could likely work but that is reducing the flexibility.
Do you know if the KH420 has passively isolated the tweeter/midrange assembly. My (lack of) browsing skills have so far failed to find a useful picture or diagram. Has anyone got a link to a parts diagram, service manual or a photo with the waveguide assembly off? The user manual provided a bit of information but not enough.
I installed a few of those as hifi speaker, and no, the mid/tweeter cabinet is not seperate from the woofer cabinet. It's only the front baffle that is removable. This is a picture of the front baffle removed and the woofer removed. (source)
These are dome drivers, a dome tweeter and dome mid so no need for a seperate cabinet.
These are dome drivers, a dome tweeter and dome mid so no need for a seperate cabinet.
Not sure I am wholly following. The point of the task is to quantify how much could be gained from controlling the crossover region precisely rather than approximately with analogue filters. FIR filter design has been around for a long time, is well developed, widely understood and there is plenty of open software and documentaton around to help. I was taught the basics 45 years ago in class (forgotten much of it) but haven't used it to develop crossovers for waveguides before. There is plenty of applied signal processing going on in the forums and I am familiar with signal processing and filter design. Has this addressed your concern?
This is what our esteemed German -now silent?- member FollGott a number of years ago built and described. Not unlike the OSMC, but quite a bit cheaper back in the day.
Good stuff. I can see a foam gasket that the assembly sits on. Can you recall if the assembly was torqued down to compress the foam flat (rigidly mounted) or to form an air seal with partially compressed foam (likely passively isolated)? The rear appears to be wholly open to the internal air pressure which is good to know (if passively isolated) given K&H/Neumann speakers tend to be well engineered. My concern about the effects of internal air pressure may be misplaced but it still ought to be checked. Encouraging.
Who is this speaker for? What is its intended purpose -- as a DIY build and as a final product?
Nostalgia suggests a middle age or older target audience.
Can you really consider a range of volume size from 50 liters to 100 liters? Is this realistic? The former can probably be accommodated by lots of folks; the latter only a few. Very few younger people have the space in their homes for speakers >50 liters.
Can a "monitor speaker" really play the role of a "party speaker" as well as a high resolution modern speaker with controlled directivity? Especially if you consider the studio monitor role with the emphasis on absolute fidelity (ie, flat FR far from Harman curve).
If a nostalgic appeal is part of the equation, vinyl play has to be a serious requirement, and sealed speakers handle the low frequency grunge far better than ported.
Are the active participants of this thread the intended users of these speakers? Aside from the OP, it seems safe to say mostly no. Most are sophisticated DIY speaker builders who have already built multiple speakers that far exceed the intended performance of this speaker.
If the design is intended for others less capable or demanding to build or use, then why not focus on something they would want and can practically use: smaller, without complexities like moveable parts, easy to place, easy to drive, easy to build, and both better than (or at least as good as) and less expensive than the seemingly capable modern $2000 JBL & Sony party speakers @tktran303 pointed out a few posts ago.
My 2 cents.
Nostalgia suggests a middle age or older target audience.
Can you really consider a range of volume size from 50 liters to 100 liters? Is this realistic? The former can probably be accommodated by lots of folks; the latter only a few. Very few younger people have the space in their homes for speakers >50 liters.
Can a "monitor speaker" really play the role of a "party speaker" as well as a high resolution modern speaker with controlled directivity? Especially if you consider the studio monitor role with the emphasis on absolute fidelity (ie, flat FR far from Harman curve).
If a nostalgic appeal is part of the equation, vinyl play has to be a serious requirement, and sealed speakers handle the low frequency grunge far better than ported.
Are the active participants of this thread the intended users of these speakers? Aside from the OP, it seems safe to say mostly no. Most are sophisticated DIY speaker builders who have already built multiple speakers that far exceed the intended performance of this speaker.
If the design is intended for others less capable or demanding to build or use, then why not focus on something they would want and can practically use: smaller, without complexities like moveable parts, easy to place, easy to drive, easy to build, and both better than (or at least as good as) and less expensive than the seemingly capable modern $2000 JBL & Sony party speakers @tktran303 pointed out a few posts ago.
My 2 cents.
it's torqued and the manual says how much, but you will feel it also. It needs to be airtight beause it's also the cabinet of the woofer. You will also need to have it sealed off with some rubber gasket (i used window sealing gaskets for this before) and torque it hard enough to make it airtight.
But they use dome drivers for mid and tweeter so both are isolated by the driver itself from the box behind it. If you use a cone driver it needs it's own sealed compartiment or you will have the woofer resonate trough the (light) cone. The mid can't conquer that with it's way lighter magent. You need to compartiment the total cabinet in at least 2 chambres, on for the mid and one for the woofer.
But they use dome drivers for mid and tweeter so both are isolated by the driver itself from the box behind it. If you use a cone driver it needs it's own sealed compartiment or you will have the woofer resonate trough the (light) cone. The mid can't conquer that with it's way lighter magent. You need to compartiment the total cabinet in at least 2 chambres, on for the mid and one for the woofer.
Most who like this kind of speaker want something in between, like a JBL L100 originally was. Not to expsneive, to big, but goes loud, relative low (i think for this 40hs F3 is good) and sounds good without dsp or other technicalities with any amplifier that has enough power. For absolute perfection you have other type of speakers, and cheap partyboxes are so cheap from asia now that it has no use to build one yourself. If you could keep the total building cost under 2K and the dificulty to build reasonable, it will be popular.
Thanks for the link. Nice project with a lot in common with what is being proposed. Looking forward to reading the write up.
Yes but what are the bolts torquing down against. If you press the tweeter/waveguide assembly from the front does it move slightly or is it rigid?
I found it interesting as an acoustic exercise. It's kind of like a variable line array, although with Keele involved it's probably been extended to three dimensional arrays.
It's a while ago but i remember it's rigid, it's bolted against a panel like i explained in the drawing above. The cabinet is mdf with a polyutherane layer on top (the outside), the waveguide is all polyutherane i thought and rigid. in between is a rubber(like) seal gasket.
If the group wants to challenge themselves then how about a three way 10/12” monkey box that only has 1st order electrical crossover (plus the odd Lpad and notch filters I guess). Always wondered what an Dynaco/Seas A25/26 would be like with a mid dome added.
I am not sure where the idea of a party speaker crept into the requirements... I think Andy has been pretty clear about the requirements (now in post #1) and the list of commercially available speakers which he strives to emulate.
For a party speaker, I would not build, I would buy something like this. Keep it stored in the garage and bring it out for parties. Striving for good sound at parties is a waste of time.
https://www.sweetwater.com/store/de...-eurolive-b115d-1000w-15-inch-powered-speaker
Thanks for the input. If the tweeter/midrange assembly is rigidly mounted then the internal air pressure on the rear is unlikely to move the assembly in any significant way. It would largely behave like a single baffle in terms of vibration.
In my opinion, even with a fairly soft gasket material (i.e. a Shore A rating of 10 or 20), the large surface area of the gasket will exert a substantial force on the MT baffle, and it will seem rigid. It may provide damping at higher frequencies (200 Hz and up), but I am very skeptical that there would be any flexing at low frequencies (50 Hz and below)
I mount recessed tweeters with this kind of soft gasket, so I can compress the gasket to achieve an exact flush mounting. The tweeter case is fully exposed to the woofer internal SPL, and I have never found any tweeter flange motion during testing or with music.
If the tweeter/mid assembly is (effectively) passively isolated it will have a resonant frequency on the baffle a decade or more below the woofer/midrange crossover frequency. Such a soft spring would be apparent if pressed so it seems unlikely passive isolation is being used. The cabinet likely handles vibration by using a load carrying material with significant internal damping (e.g. whatever LRIM^TM is) plus strategically placed lumps of damping for the modes that are too large. This is likely to be plan B if plan A to make the woofer cabinet stiff isn't working well enough with a large cabinet and heavy woofer.
Agreed. Maybe we could have a moderator delete every reference to "party speaker" in the thread. 😂😂 (Just kidding, mods)