i have another 3015lf coming my way, and was going to build an ss15 to sell (cuz its fun, and i figured i could get some $ back for it) buttttttt i was thinking of replacing my 38hz tang band tapped horns with a single large subwoofer.
so could i use the 3015lf for a HT sub? i know its not a true subwoofer, thats why i am asking, will it be able to go low enough? i have a qsc rmx 1450 amp which i will be using as a sub amp. it has a selectable 30hz and 50hz limiter, but its not an active crossover where i can adjust slopes etc.
if i build the box to fit underneath my TV, i will have about 4 feet width, 3 feet depth, and height i would like to keep as short as possible because the subwoofer box would act as a "base" for the TV, raising it up by whatever height the box is. so say 12-15ft^3 to work with.....
and bridged i think the amp does around 700rms into 8 ohms? i forget...
so could i use the 3015lf for a HT sub? i know its not a true subwoofer, thats why i am asking, will it be able to go low enough? i have a qsc rmx 1450 amp which i will be using as a sub amp. it has a selectable 30hz and 50hz limiter, but its not an active crossover where i can adjust slopes etc.
if i build the box to fit underneath my TV, i will have about 4 feet width, 3 feet depth, and height i would like to keep as short as possible because the subwoofer box would act as a "base" for the TV, raising it up by whatever height the box is. so say 12-15ft^3 to work with.....
and bridged i think the amp does around 700rms into 8 ohms? i forget...
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awesome~ how would i go about creating a fold for that? i have seen the various folds people have done for the ss15 and the corresponding sims, but i'm not sure which order they do them in. do they just come up with a folding tecnhique then enter all the "s1,2,3" etc dims into hornresp? or is it the other way around?
Few notes to consider:
1.) Bjorno's prediction seem to be using the old version data of the 3015lf
2.) Since you only have access to 30Hz or 50Hz hi-pass filters, going 20Hz for designing is a waste of efficiency.
3.) In my opinion TH's or TQWT need delay compensation for the tops.
4.) Using the 3015lf below 30Hz has a very bad volume/performance/efficiency/costs ratio.
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hmmm okay...i figured i'd do it because i have the spare driver coming. i guess i could just build another ss15 and sell it or just sell the driver itself for what i paid. i got it from b&h for 214 after tax/shipping etc. so if someone wants it for 214 shipped i'll sell it or i'll just build a new ss15 
Or ask Bjorno to redesign his suggestion for 30Hz with the data from the new version of the 3015lf and don't use delay compensation or put your driver in a oversized basreflex cab tuned to 30Hz.... choices enoughhmmm okay...i figured i'd do it because i have the spare driver coming. i guess i could just build another ss15 and sell it or just sell the driver itself for what i paid. i got it from b&h for 214 after tax/shipping etc. so if someone wants it for 214 shipped i'll sell it or i'll just build a new ss15
Remember using a driver in a oversized basreflex cab with a lower system resonance as the Fs of the loudspeaker is not optimal and limits its power handling. With MDF it's going to be a heavy big beast
But you can try this:
Basreflex volume (including driver and port) = 300litre (10.59 cubic foot)
Port (square for easy building) = 19,05cm x 19,05cm (7.5inch x 7.5inch)
Port Length = 28,41cm (11.19inch)
If you want to use round port(s) and/or flanged end(s) just let me know. Use 2 inch acoustic damping material on the walls. If you want to go more fancy you can find a lot of subjects in DIY about it. You can use (or buy since they come very cheap) an old graphic HiFi eq to use for making up the response if you like. With that amp you will get approx. 113dB@30Hz out of it in 2pi (this is minus pwr compression) but use your ears and eyes to hear/see if the driver feels happy with that kind of power.
But you can try this:
Basreflex volume (including driver and port) = 300litre (10.59 cubic foot)
Port (square for easy building) = 19,05cm x 19,05cm (7.5inch x 7.5inch)
Port Length = 28,41cm (11.19inch)
If you want to use round port(s) and/or flanged end(s) just let me know. Use 2 inch acoustic damping material on the walls. If you want to go more fancy you can find a lot of subjects in DIY about it. You can use (or buy since they come very cheap) an old graphic HiFi eq to use for making up the response if you like. With that amp you will get approx. 113dB@30Hz out of it in 2pi (this is minus pwr compression) but use your ears and eyes to hear/see if the driver feels happy with that kind of power.
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If you really want to use that QSC amp just try to use 1 channel first. I think the 260Watts at 8Ohm is enough to make things rumble. You can use it in bridge if you are careful but remember the QSC's continues average power in bridge is way over the IEC continues power rating of the driver.
Hi,
Why making a from the beginning a bad impulse response to be more worse:There has been posted quite a few misconceptions since I posted yesterday.
I will later be back with comments on all.
b
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I could run the 3015lf in whichever cab I choose and place that in the front of the room powered by one channel of the qsc amp then I can run the tang band horns in the rear of the room on each side of the couch and power those off the other channel of the qsc, ran in series.
I know there may be some cancelation issues with different subs, but I like the idea of distributed bass throughout the room. It can't hurt to try it!
Bjorno please come back and comment when you have time! Thanks!
I know there may be some cancelation issues with different subs, but I like the idea of distributed bass throughout the room. It can't hurt to try it!
Bjorno please come back and comment when you have time! Thanks!
I don't like the dips/peaks of the BR with the inductor at all! I like the response curve of the quarter wave design! Is that peak/dip worse or better because of the inductor? I was under the impression that the inductor would help flatten the response, but it doesn't look like it in this case!
The sims don't accurately show the response of either box, but having tested various boxes with and without large inductors (which are ridiculously expensive for just some copper and iron) I have never seen them do anything like what was shown.
The TQWT sim is about 5 dB down from the ported box at 30 Hz, what is it you like about it's response, which starts low in the bottom and rises in the top ?
Art
Hi Bjorno,
Although I appreciate your efforts and the enormous amounts of predictions you seem to publish I’m afraid I have to agree with Art (for once...again). Comparing two different design concepts purely based on theoretical models (that are not even correct) is very questionable. If it was possible to judge purely on theoretical models from software, no serious PA manufacturer, studio monitoring manufacturer or respectable HiFi manufacturer would invest so much in time, effort and expertise in developing loudspeakers.
Like Art says your prediction from HornResp about the SPL response of the basreflex with an inductor in series, looks anything but realistic. I suppose you added the value of the inductor with the value of the voice coil. Even from a theoretical point of view that would be wrong. I’ll give you a few notes you can consider;
1.) The voice coil is moving in a magnetic field and in the same time creating a magnetic field on its own (try to imagine how many variables that produces)
2.) The voice coil is under influence of relative big temperature changes during loading (change of resistance and induction values).
3.) An external inductor has minimal temperature changes (if the right diameter of the wire and type of construction is chosen)
4.) Since HornResp has no input for room acoustics, cone damping, cone material or pwr compression levels, the impulse behaviour it predicts is just a theoretical indication and will not represent any real life measurement (or sound experience).
5.) Impedance; In your basreflex impedance model the plot shows a little off-set from 30Hz tuning. Besides that minor thing, the impedance peaks of basreflex cabs are not correct. It should have a less high first peak.
5.) The internal standing waves in any cab are nothing more then ½ wave (or bigger) values. The dimensions MrGsR is looking for have standing waves that would fall out the bandpass. Highest frequency I was targeting 120Hz - 1/2WL = 1.43m (4.69 foot). Highest frequency you were targeting was even lower 80Hz – 1/2WL = 2.15 (7 foot).
6.) Quote: “will sound booming and equipped with PA box like artefacts if not heavily cross braced and volume filled with damping material unless low SQ PA sound is targeted….”
- First of all, bracing to prevent panelflex/absorbtion counts for any design made out of wood.
- Secondly your suggestion that internal damping material is even more important for PA drivers is the opposite from reality. Since PA drivers have generally higher electrical and physical damping values then most other drivers is one of the reasons why PA cabs often need less internal damping materials. In your own impulse prediction you can see the reason why a TQWT can even benefit more from internal damping. Besides the fact that HornResp can only 'see' parts of the electrical damping! Therefore your statement has a contradiction in itself and you own graphical prediction shows it.
7) If you read MrGsR his request carefully you could have known he is using a two setting low-cut filter of 30Hz or 50Hz. Therefore designing a cab with lower Fs is not functional and will be at cost of efficiency and extra volume.
Nevertheless, basreflex designs do have their own typical problems and advantages like any other type of design. And yes, there is something to say about other types of designs that can have advantages over the non optimised basreflex as presented (with its lower system Fs than the Fs of the driver in free space and bigger than optimum volume for instance). On the other hand a basreflex design is often judged as more tolerant about building errors and such. However, I don't want to argue for which type MrGsR should choose simply because it's a personal decision based on personal considerations and/or preferences.
Although I appreciate your efforts and the enormous amounts of predictions you seem to publish I’m afraid I have to agree with Art (for once...again
). Comparing two different design concepts purely based on theoretical models (that are not even correct) is very questionable. If it was possible to judge purely on theoretical models from software, no serious PA manufacturer, studio monitoring manufacturer or respectable HiFi manufacturer would invest so much in time, effort and expertise in developing loudspeakers. Like Art says your prediction from HornResp about the SPL response of the basreflex with an inductor in series, looks anything but realistic. I suppose you added the value of the inductor with the value of the voice coil. Even from a theoretical point of view that would be wrong. I’ll give you a few notes you can consider;
1.) The voice coil is moving in a magnetic field and in the same time creating a magnetic field on its own (try to imagine how many variables that produces)
2.) The voice coil is under influence of relative big temperature changes during loading (change of resistance and induction values).
3.) An external inductor has minimal temperature changes (if the right diameter of the wire and type of construction is chosen)
4.) Since HornResp has no input for room acoustics, cone damping, cone material or pwr compression levels, the impulse behaviour it predicts is just a theoretical indication and will not represent any real life measurement (or sound experience).
5.) Impedance; In your basreflex impedance model the plot shows a little off-set from 30Hz tuning. Besides that minor thing, the impedance peaks of basreflex cabs are not correct. It should have a less high first peak.
5.) The internal standing waves in any cab are nothing more then ½ wave (or bigger) values. The dimensions MrGsR is looking for have standing waves that would fall out the bandpass. Highest frequency I was targeting 120Hz - 1/2WL = 1.43m (4.69 foot). Highest frequency you were targeting was even lower 80Hz – 1/2WL = 2.15 (7 foot).
6.) Quote: “will sound booming and equipped with PA box like artefacts if not heavily cross braced and volume filled with damping material unless low SQ PA sound is targeted….”
- First of all, bracing to prevent panelflex/absorbtion counts for any design made out of wood.
- Secondly your suggestion that internal damping material is even more important for PA drivers is the opposite from reality. Since PA drivers have generally higher electrical and physical damping values then most other drivers is one of the reasons why PA cabs often need less internal damping materials. In your own impulse prediction you can see the reason why a TQWT can even benefit more from internal damping. Besides the fact that HornResp can only 'see' parts of the electrical damping! Therefore your statement has a contradiction in itself and you own graphical prediction shows it.
7) If you read MrGsR his request carefully you could have known he is using a two setting low-cut filter of 30Hz or 50Hz. Therefore designing a cab with lower Fs is not functional and will be at cost of efficiency and extra volume.
Nevertheless, basreflex designs do have their own typical problems and advantages like any other type of design. And yes, there is something to say about other types of designs that can have advantages over the non optimised basreflex as presented (with its lower system Fs than the Fs of the driver in free space and bigger than optimum volume for instance). On the other hand a basreflex design is often judged as more tolerant about building errors and such. However, I don't want to argue for which type MrGsR should choose simply because it's a personal decision based on personal considerations and/or preferences.
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MrGsR (btw do you have another more easy spelling name ), for what it is worth I made you some theoretical predictions that speak for themselves. Although they might be theoretical more correct it still doesn't represent any real response of a build cab.
), for what it is worth I made you some theoretical predictions that speak for themselves. Although they might be theoretical more correct it still doesn't represent any real response of a build cab. Attachments
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+ the 3dB that is going to be cut by the filter at 30Hz. To me that looks like 6dB difference in the bandpass 30-90hz besides the fact the wrong data of your 'new version' 3015lf is used. Also look at the max power input Vs max SPL if that suits your goal.
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