Hi,
I want to build a sealed sub-woofer using a pair old 10" woofers (LO-D L2502) from a Hitachi HS 330 mk2.
Unfortunately I cannot find T/S parameters anywhere on the net. I do have the original cabinets, so I figured I can use those dimensions for the new enclosure. The original box is very a precisely built vented design, but since I want to build a closed one I'm not sure that I can use those sizes (minus the reflex port, xo, mid and tweeter volume) for a sealed box? Also using thicker mdf instead of the original chipboard panels would matter?
cheers
I want to build a sealed sub-woofer using a pair old 10" woofers (LO-D L2502) from a Hitachi HS 330 mk2.
Unfortunately I cannot find T/S parameters anywhere on the net. I do have the original cabinets, so I figured I can use those dimensions for the new enclosure. The original box is very a precisely built vented design, but since I want to build a closed one I'm not sure that I can use those sizes (minus the reflex port, xo, mid and tweeter volume) for a sealed box? Also using thicker mdf instead of the original chipboard panels would matter?
cheers
seal, fit and try.
The worst that can happen is that the hump in the frequency response is too high for your listening preferences.
If it is too high, or rolls off too slowly, you can read up on and implement a Linkwitz transform.
The worst that can happen is that the hump in the frequency response is too high for your listening preferences.
If it is too high, or rolls off too slowly, you can read up on and implement a Linkwitz transform.
Thanks.
I will be using with an active xo. The original xo was somewhere around 900hz for the woofer, but obviously I will set it a lot below that.
I will be using with an active xo. The original xo was somewhere around 900hz for the woofer, but obviously I will set it a lot below that.
Just red through quickly the Linkwitz transform. I see now what you meant. Seems to be a very cool thing, but I hope there will be no need for that.
Yeah, I wish everybody wanted to do the same. Just make a slightly leaky sealed box and you'll be happy (assuming the box isn't too small or the drivers too anemic).
There're no design principles with sealed boxes (or leaky boxes) worth fussing about. That's the simple practical truth.
The art lies in having whatever little output bump-up occur in a freq range that's beneficial and it often will be (see my assumptions above).
Ben
There're no design principles with sealed boxes (or leaky boxes) worth fussing about. That's the simple practical truth.
The art lies in having whatever little output bump-up occur in a freq range that's beneficial and it often will be (see my assumptions above).
Ben
Since this loudspeaker is a precisely engineered vented enclosure (As most are), the EBP is suited to a vented alignment. Simply sealing up the vented enclosure will get you a severely rolled off response getting you a Qtc near to 0.5.....that said, if you put the pair of drivers in an enclosure near to the same volume as ONE enclosure, this will drive up the Qtc closer to 0.7, sealed.
______________________________________________Rick...........
______________________________________________Rick...........
Hi,
Wall thickness makes no difference to internal dimensions.
A pragmatic approach is build it sealed, with opposed
drivers on the left and right walls, well stuffed and go
for 1.5 times the one original box internal volume.
rgds, sreten.
FWIW there is nothing precise about a vented box
you can tell by just looking. You cannot tell whether
it a proper bass alignment or a serious boom box
alignment, the latter often used as cheap BSC.
Wall thickness makes no difference to internal dimensions.
A pragmatic approach is build it sealed, with opposed
drivers on the left and right walls, well stuffed and go
for 1.5 times the one original box internal volume.
rgds, sreten.
FWIW there is nothing precise about a vented box
you can tell by just looking. You cannot tell whether
it a proper bass alignment or a serious boom box
alignment, the latter often used as cheap BSC.
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Thanks for the inputs guys, especially to bjorno for the lovely chart. Got the guidelines, though the optimal result still gonna be a bit of question of luck. Probably I install both drivers into a slightly smaller box size than the original and try to adjust with damping if needed or worth it.
You could use one as a guinea pig. Seal it up and brace larger spanning panels then start adding mdf filler panels in increments until you find a sweet spot. Then you can play with stuffing. Add and subtract whats necessary to double up for a second driver. But what if they are a lot more compliant in an open environment..it might sound like poop.
Sounds like a good plan. If they are more suited for vented (which is quite possible), then I might build one like that. I have those pretty looking, kind of unique woofers so got to use them for something.
Can you explain what your message means?
Then go on to explain what the attachment is telling us?
Hi to all, I am building a 2x18" sealed subwoofer too. With the t/s parameters, all programs gave me the same volume. If you can actually measure the drivers, it would be best. Post some pictures maybe they are identified. Lower box volume means less bass extension, larger box will increase the excursions. @streten : a push-pull, this is what I did, the Vb has to be double the calculated volume, not 1.5 times according to what I read on it. Am I wrong ?
It would be more precise to say, "... they gave me a volume which produced a total output curve for a sealed box that somebody thought looked pretty."
The models do little more than that for sealed boxes that is actually helpful in making a box. (For boxes where wave-lengths and resonances have any significance, these models can help in other ways. But then I am not sure these other kinds of boxes have widespread applicability in home systems.)
What you want is a woofer in your room that sounds pretty in light of the sources you play, room characteristics, gut feel, dispersion, reflections, etc.
If you were to take a model of a sealed box seriously, you'd first have to start with your "house curve" or what you want when done as your criterion of performance. House curves ain't flat.
Ben
The models do little more than that for sealed boxes that is actually helpful in making a box. (For boxes where wave-lengths and resonances have any significance, these models can help in other ways. But then I am not sure these other kinds of boxes have widespread applicability in home systems.)
What you want is a woofer in your room that sounds pretty in light of the sources you play, room characteristics, gut feel, dispersion, reflections, etc.
If you were to take a model of a sealed box seriously, you'd first have to start with your "house curve" or what you want when done as your criterion of performance. House curves ain't flat.
Ben
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All a question of how much effort and detail on sound engineering you would like to spend vs trial and error. For engineered results, I'd suggest to measure your TS parameters using a PC-based free frequency generator program to your liking, a (>1W) power resistor between 20-100 Ohms, your amp, and measure your impedance from 20-120Hz to calculate your fs, f(-3dB), from there your Q's after measuring coil DC resistance with a multi-meter. Possibly, and carefully, with a DC current source for better resolution. Make sure you operate with "small signals" under 1V for small signal parameters. Repeat in 0.1Hz steps around fs and f(-3dB) for accuracy. After measuring in sealed enclosure, repeat measurements in free air, carefully suspending chassis, ie suspended from ladder, calculating Qt. Then repeat measurement with a few pennies taped carefully on top of speaker dust cover, calculate compliance from Vas/Vb. Measure R(0) with Ohmmeter. Now it may not be worth spending a whole weekend on this, but you will know for sure what to expect instead of assuming a large variety of ported alignments that could get you Qb's from the 0.3 (flat) to 1 (boom). For simplicity you can also try stuffing the box with different density until you like it, changes your "effective" volume as seen from the speaker as much as 15%. Or add a Variovent (if they still make those), or consider even a passive radiator. Have a fun filled weekend!
@bentoronto : I agree that everybody should make extensive acoustic measurements of rooms, but do they ? Actually I bought equipment for this, it hasn't arrived yet 🙂 I suppose that you are a user of odeon.dk then, I checked it out, great program. regarding a sealed sub, I opted for it because it fits my setup. The drivers would sound better in a ported box. Fine.
I know my energetic outbursts may leave something to be desired as clear communication. My views are actually more in the school of "do it" like Nike, rather than as you think, getting bogged down on measurements before you start the always messy, highly imprecise task of system building.
I believe models and theories today are wonderfully good, if not quite perfect. My point is that they provide information only up to a point and that point is technically good but, at least for sealed boxes, far from "user experience."
Not sure my term is exactly right as "house curve" but what you want is a nice bass experience. Ordinarily (including fancy movie theatres), this includes some boost in the bass. Ultimately, what you (and movie theatres) really want - should you eventually both to measure your room - is a measurement the rises in the bass.... not flat as the models think.
The models are wrong to suggest their curve is right. Boost is right.
Ben
I believe models and theories today are wonderfully good, if not quite perfect. My point is that they provide information only up to a point and that point is technically good but, at least for sealed boxes, far from "user experience."
Not sure my term is exactly right as "house curve" but what you want is a nice bass experience. Ordinarily (including fancy movie theatres), this includes some boost in the bass. Ultimately, what you (and movie theatres) really want - should you eventually both to measure your room - is a measurement the rises in the bass.... not flat as the models think.
The models are wrong to suggest their curve is right. Boost is right.
Ben
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Hi,
Sometimes push push works better than push pull, its certainly a lot easier to make it look nice, and sometimes push pull is simply not worth the effort to make it look nice. Both can be used in force cancelling mode on opposite faces.
You are misreading my post. For vented you usually double box volume of using the same driver sealed.
Erring on the side of caution, (and FWIW completely disagreeing with Bjorno's guesstimates of the likely driver parameters for such a speaker, way off IMHO), I'm suggesting using 50% more than one of the original cabinets for two sealed drivers, when it should be the same moreorless in theory, and its only a guesstimate.
Sealed and well stuffed IMO it is the best guesstimate, though a simple sealed impedance curve allowing Qbox measurement would remove a lot of the guessing.
The problem is BSC and such speakers typically roll in the midrange above the BSC point, so all BSC applies to the bass unit. Many didn't bother with any electrical BSC, just used a boomy bass to provide some BSC, some used boomy bass and a bit of electrical for BSC, rarely did such speakers use a proper bass alignment and full electrical BSC.
rgds, sreten.
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Hi,
I can't agree with any of your premises in the attachment at all ... sorry.
Though I admit the small port diameter suggests a relatively low tuning
compared to the worst of the type. Driver Fs, Vas and Qts is still very
hard to guess, i.e. any guess is much more likely to be wrong than right.
rgds, sreten.
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