You're saying Fs needs to be closer to 20 for it to work in the Digger8? I'd take Fs
being off for a B4 as being compliance error and just try it in the simulator. I don't
think that the JBL 860 had the correct Fs either but it worked just fine.
Oh, and I was planning to tune higher anyway, probably 25 Hz.
Maybe 25 for music and 20 for HT.
Brings back memories of the EBS discussion, what? 20 years ago on the Bass List.
being off for a B4 as being compliance error and just try it in the simulator. I don't
think that the JBL 860 had the correct Fs either but it worked just fine.
Oh, and I was planning to tune higher anyway, probably 25 Hz.
Maybe 25 for music and 20 for HT.
Brings back memories of the EBS discussion, what? 20 years ago on the Bass List.
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No need to spend any time on it, just thinking out loud here.
Your measurements seem to show little if any slot/pipe resonances or are they
outside the measurement range?
It's not just Fs , but the combo of F's and Qts. The 860 has a higher Qts, which means it cab achieve a lower F3 for the same Fb in a vented alignment.
In designing a vented alignment for these drivers, I'd keep an eye on group delay as well, though that probably won't matter much below 35Hz and below, when the room begins to dominate.
The sim suggests a minor resonance around 200Hz and larger ones above 300Hz but those introduce dips, not peaks in the overall response, so they should be less noticeable. The resonance above 300Hz are outside the measurement range and the passband that this subwoofer is being used to cover.
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It wouldn't really be a fair comparison. The THs I built were designed with greater efficiency and a higher Fb, and they used larger drivers. The only definitive difference I feel comfortable pointing out is that the "Boom Unit" suffers from a little port compression at the upper limits of its theoretical linear SPL capability and the THs did not.
Based on the few that I've built so far, the THs seem to have an "effortless" sound to them. Played back at any level, I'm left with the impression that they can be driven at a higher SPL level if I wanted to. And when properly matched with tops via DSP, the result sounds very, very good.
I've got a bigger "Boom Unit" design on paper that uses the same PA310 I used for the original POC3 TH, that should produce a simliar low-frequency cutoff, albeit at a lower SPL, but in a smaller box. I'm really tempted to build it to see if a TH alignment with the same driver does sound better.
so Boom Unit for PA310 vs POC #3 about like so ? (might have confused something as flu-ish) - its difficult to pass up such a nice 12 for $59
Yup. The POC3 is a bit more efficient, but the PA310 Boom Unit is a simpler build with a wider passband in a smaller box. The vents are large enough to minimize vent compression effects too. The PA310 Boom Unit would be small enough that you can just put a handle on the top of it and hand carry it without difficulty. The POC3 OTOH needs wheels or two sets of hands if you want to carry it more than a few feet
.
COOL! - a couple of dB should not be missed in trade for something easy to carry and build.
regarding "BVR" with positive flare vents, those generally don't give much "gain" the way they are sized ?? They were popular in the early 1950's then with musical instrument speaker applications later on.
(sorry for the sanitized BVR graph - hit the mask button)
regarding "BVR" with positive flare vents, those generally don't give much "gain" the way they are sized ?? They were popular in the early 1950's then with musical instrument speaker applications later on.
(sorry for the sanitized BVR graph - hit the mask button)
The "positive flare" vents will give some gain at higher frequencies, at the expense of a higher Fb. It really depends on what type of music you expect to be playing back through it. I like to aim for an Fb no higher than about 42 Hz for "subwoofer" duty, even if it's down a few dB by that point. Above Fb I can treat the passband with EQ, but Fb basically defines the lowest frequency the subwoofer should be used at.
Interestingly enough your BVR design is only 60L. Both of my "Boom Unit" designs for the PA310 check in at around 75L, slightly bigger
IIRC, "bass" at a reasonably low level from pure sine starts sounding fat around 50Hz - guess we are geared so 1/3 octave down from there sounds pretty deep. The introduction of round wound bass guitar strings added a lot of overtones (and chewed up frets). I'm not fond of bass guitar sounds which resemble bad subwoofer..
No need to - the "Guides" sheet in the workbook for the Boom Unit gives the locations for the guidelines to be traced on the side panels for the position of panel E and the other panels.
Hi Brian,
I keep coming back to this after you shared it in another thread; I really like the profile and how small this is and would love to build something mighty with a small 8 inch driver. Even more fun is that it's an inexpensive driver. Would you mind entertaining some questions? Forgive my green gills. The front baffle, does it have to be recessed? Was that done for internal volume and spacing or for aesthetic? The angled shelf inside, what angle is that measured to? I tried to model it in Hornresp but didn't see this part. The rest of the folds look straight forward, I think. I may try this with 3/4th inch Birch ply that I have on hand. Was thinking of something small, skinny with an 8" driver that can competently do 30hz ~ 80hz on low power.
Very best,
I keep coming back to this after you shared it in another thread; I really like the profile and how small this is and would love to build something mighty with a small 8 inch driver. Even more fun is that it's an inexpensive driver. Would you mind entertaining some questions? Forgive my green gills. The front baffle, does it have to be recessed? Was that done for internal volume and spacing or for aesthetic? The angled shelf inside, what angle is that measured to? I tried to model it in Hornresp but didn't see this part. The rest of the folds look straight forward, I think. I may try this with 3/4th inch Birch ply that I have on hand. Was thinking of something small, skinny with an 8" driver that can competently do 30hz ~ 80hz on low power.
Very best,
The baffle does not need to be recessed. I did that primarily to protect the driver. Keeping the layout and removing the recess will move Fb up, but I think the change is going to be very small.
I don't know offhand what the angle of the internal panel is, as I used the guidelines generated by the workbook to position it inside the box. If you're going to use 3/4 ply, you're going to need to use the workbook to adjust the dimensions accordingly and then you can follow the guidelines suggested in the workbook to properly locate the internal panel.
I don't know offhand what the angle of the internal panel is, as I used the guidelines generated by the workbook to position it inside the box. If you're going to use 3/4 ply, you're going to need to use the workbook to adjust the dimensions accordingly and then you can follow the guidelines suggested in the workbook to properly locate the internal panel.