MJK said:
Martin, is that true? I've been able to model bandpass boxes using your *horn* worksheets; so I wouldn't be surprised if your horn worksheets could to a Jensen Transflex too! Check out this article I wrote, it shows all the details. In a nutshell, a front-loaded-horn and a single-reflex bandpass are very, very similar. With careful attention to the port dimensions, I'll bet that your FLH worksheets would model Transflex too. JOHN
http://home.comcast.net/~j.vanommen/speakers/Single_Reflex_Bandpass_vs_Front_Loaded_Horn.pdf
Hi John,
I really like your article, nice work! I agree with you that the front loaded horn worksheet can be used to model a bandpass enclosure with some creative editting of the detailed input section. Unfortunately I have not upgraded the front loaded horn worksheet to the level of the newer versions of the TL worksheets so it is not available at the moment.
But my understanding of the Jensen Transflex is it loads a TL at both the front and rear of the driver as shown in the picture posted earlier in this thread. There must be some special frequency where the standing wave in the TL is 180 degrees out of phase along the length of the line between the front and rear of the cone and I am not sure what happens at that point. But to date, I don't think any of my MathCad worksheets will simulate this condition accurately. It would require some more theory deriving and some reprogramming in MathCad to simulate this enclosure geometry.
Maybe my understanding of the geometry is not correct.
I really like your article, nice work! I agree with you that the front loaded horn worksheet can be used to model a bandpass enclosure with some creative editting of the detailed input section. Unfortunately I have not upgraded the front loaded horn worksheet to the level of the newer versions of the TL worksheets so it is not available at the moment.
But my understanding of the Jensen Transflex is it loads a TL at both the front and rear of the driver as shown in the picture posted earlier in this thread. There must be some special frequency where the standing wave in the TL is 180 degrees out of phase along the length of the line between the front and rear of the cone and I am not sure what happens at that point. But to date, I don't think any of my MathCad worksheets will simulate this condition accurately. It would require some more theory deriving and some reprogramming in MathCad to simulate this enclosure geometry.
Maybe my understanding of the geometry is not correct.
The new (vented box) bipole sheet is up guys, if you didn't already know. And after playing with it for a few hours, I can safely assert, it's a stunner. Bipoles have gained a lot of interest over the last year or so, so this should become a vital tool for designing them. Easy to use, and amazingly flexible. Nice one, Martin.
MJK said:
Greets!
You got it right, so with no way to adjust 'zdriver' there's no way to even 'kludge' it in the FLH WS.
GM
wow, they keep coming, great! I'll hop over to paypal and finally do what I have been planning to do for some time but have been too lazy...Scottmoose said:
btw: I read in another thread (was it the Thor thread?) that a multiple driver sheet is on the way.. now that would be great!
Paypal
That sounds just like me.
I did the paypal thing on Thursday, then I found out it may take 7 days for the transaction to be completed....I was sooo looking forward to playing with a new toy during the holiday weekend.
That sounds just like me.
I did the paypal thing on Thursday, then I found out it may take 7 days for the transaction to be completed....I was sooo looking forward to playing with a new toy during the holiday weekend.
Ed,
I hate to see a holiday weekend go to waste! I have hooked you up so look in your e-mail for a User ID and password. Have fun.
What a guy!
Imagine my surprise on this Sunday morning to wake (with coffee in hand) to this wonderful news! I "did church" last night, so with the wife's permission (enter the "Jaw's" theme
), I've got a new toy to play with throughout the day. Those smallmouth will just have to wait 'til tomorrow.
I also checked my bank account to see if Paypal had debited the amount. They haven't. So, Martin, you are truly behaving on faith....an admirable trait...one there is too little of.
I'm grateful for all you share with us. 😉
Imagine my surprise on this Sunday morning to wake (with coffee in hand) to this wonderful news! I "did church" last night, so with the wife's permission (enter the "Jaw's" theme
), I've got a new toy to play with throughout the day. Those smallmouth will just have to wait 'til tomorrow.I also checked my bank account to see if Paypal had debited the amount. They haven't. So, Martin, you are truly behaving on faith....an admirable trait...one there is too little of.
I'm grateful for all you share with us. 😉
I trust ya Ed. The mental image of a fellow speaker designer wasting a whole three day weekend just broke my heart. I think the girls are going out shopping later, the minute they leave my son and I are running some new speaker cables. Screw the job list!
This may be redundant...what I think I am seeing is the area under the curve being pushed around by my manipulation of variables: port size, stuffing, volume & location, location, location.
Increasing port length increases restriction & moves the resonant frequency lower. I'm seeing the speaker (drivers & port) response droop ~ 3.5 to 4 dB, however the addition of room gain flattens this. This results in an increase of bass extension.
I am watching the "Woofer and Terminus Far Field Sound Pressure Level Responses" graph. I find that adjusting Zdriver to result in the greatest distance between the intersects with the -180 phase level smooths the combined response at the first reflection point.
For my simulation I have found the point where increasing stuffing begins to diminish low frequency response. I found I was able to decrease the first reflection dip by 5 dB and broaden the curve. Now I'm into the trade-off zone. The remaining dip is ~centered @ 160 hz and ~4.5 dB deep. System response is ~flat to 27 hz.
So I would like to pose this question to all:
From your experience, How significant is the dip? What amount of dip is acceptable?
Back to the toys...
Increasing port length increases restriction & moves the resonant frequency lower. I'm seeing the speaker (drivers & port) response droop ~ 3.5 to 4 dB, however the addition of room gain flattens this. This results in an increase of bass extension.
I am watching the "Woofer and Terminus Far Field Sound Pressure Level Responses" graph. I find that adjusting Zdriver to result in the greatest distance between the intersects with the -180 phase level smooths the combined response at the first reflection point.
For my simulation I have found the point where increasing stuffing begins to diminish low frequency response. I found I was able to decrease the first reflection dip by 5 dB and broaden the curve. Now I'm into the trade-off zone. The remaining dip is ~centered @ 160 hz and ~4.5 dB deep. System response is ~flat to 27 hz.
So I would like to pose this question to all:
From your experience, How significant is the dip? What amount of dip is acceptable?
Back to the toys...
Greets!
The lower in frequency the dip, the greater it can be due to our decreasing hearing acuity and why way too short basshorns with extreme measured TL 'ripple' still 'sound' fine since being amplitude oriented creatures we key in on the loudest fundamentals, so if the peaks yield a ~flat in-room response then you're doing better than the vast majority of folks.
Indeed, due to our hearing curve, a simmed rising 'sub' BW response to offset typical room construction losses is a good plan and enhances organ symphonys, minimally compressed recordings and movie soundtrack special effects. Anyway, my motto is to design for max acoustic gain you're likely to want/need since EQing it lower can only improve overall performance whereas boosting it can only degrade it.
Of more concern is controlling the attendant harmonic 'ringing' and audible out of phase reflections in our acute hearing BW (especially the 'phone BW' of ~250 - 3 kHz), so is what you want to concentrate on IMO and if you can smooth out the low end then it's 'icing on the cake'. That said, the well regarded Onken cab and similar 'big vent' alignments (including TLs) cause audible comb filtering between the vent and driver outputs in this BW, which gets some additional modulation by the room, and this relatively high level of harmonic distortion is deemed by numerous folks as quite natural sounding on many recordings (especially CD), so it's not necessarily desirable to be designed out (billiard table flat FR) if perceived accuracy is more important than a technically more accurate one.
As always though, YMMV.
GM
The lower in frequency the dip, the greater it can be due to our decreasing hearing acuity and why way too short basshorns with extreme measured TL 'ripple' still 'sound' fine since being amplitude oriented creatures we key in on the loudest fundamentals, so if the peaks yield a ~flat in-room response then you're doing better than the vast majority of folks.
Indeed, due to our hearing curve, a simmed rising 'sub' BW response to offset typical room construction losses is a good plan and enhances organ symphonys, minimally compressed recordings and movie soundtrack special effects. Anyway, my motto is to design for max acoustic gain you're likely to want/need since EQing it lower can only improve overall performance whereas boosting it can only degrade it.
Of more concern is controlling the attendant harmonic 'ringing' and audible out of phase reflections in our acute hearing BW (especially the 'phone BW' of ~250 - 3 kHz), so is what you want to concentrate on IMO and if you can smooth out the low end then it's 'icing on the cake'. That said, the well regarded Onken cab and similar 'big vent' alignments (including TLs) cause audible comb filtering between the vent and driver outputs in this BW, which gets some additional modulation by the room, and this relatively high level of harmonic distortion is deemed by numerous folks as quite natural sounding on many recordings (especially CD), so it's not necessarily desirable to be designed out (billiard table flat FR) if perceived accuracy is more important than a technically more accurate one.
As always though, YMMV.
GM
Ed,
Have you considered that flat to cut-off may not be the best solution. Something like a 3-6 dB/octave roll-off starting at 100 Hz or so may give you flat in-room. Speakers that are flat to cut-off often sound boomy in-room. Of course, this all depends on room size, speaker location and all of the other standard caveats.
Bob
Have you considered that flat to cut-off may not be the best solution. Something like a 3-6 dB/octave roll-off starting at 100 Hz or so may give you flat in-room. Speakers that are flat to cut-off often sound boomy in-room. Of course, this all depends on room size, speaker location and all of the other standard caveats.
Bob
GM, Thanks for the reply.
When I posed my question about the depth of the dip, I had yet to fiddle with the distance from the baffle to the back wall. I've run through several sim's and arrived at 0.83 m. This produces 2 dips. One is ~85 hz. The other is just below 200 hz. I chose 0.83 m in order for the dips to have roughly equal depths and area under the curve. I also wanted to stay within a resonable distance from the wall...no need to try to explain to the wife "it just sounds better that way" 🙄
Bob, Thank you as well. You are right on the mark. I found by lengthening the port I could decrease the amplitude and extend the range of the bass response. I refer to the combined response that includes room lift for "flat" response.
When I posed my question about the depth of the dip, I had yet to fiddle with the distance from the baffle to the back wall. I've run through several sim's and arrived at 0.83 m. This produces 2 dips. One is ~85 hz. The other is just below 200 hz. I chose 0.83 m in order for the dips to have roughly equal depths and area under the curve. I also wanted to stay within a resonable distance from the wall...no need to try to explain to the wife "it just sounds better that way" 🙄
Bob, Thank you as well. You are right on the mark. I found by lengthening the port I could decrease the amplitude and extend the range of the bass response. I refer to the combined response that includes room lift for "flat" response.
OK,
I got some bugs worked out on my end and I'm ready to learn some of the finer points in the worksheet.
I'm using the ML-TQWT sheet. I saw that my Port Air Velocity was above the recommended 0.03. So I changed from a 3" port to a 4". The switch requires lengthening the port to ~16". Fitting this length of port into my case requires I turn it 90 degrees and up.
Does the location of the entry of the port inside the case affect the validity of the results?
If the length of the port is included in the path length of the wave, should I include this in my considerations for setting Z (driver or port)?
As the Port Air Velocity I was obtaining was ~0.04, would it be better to retain the smaller (and shorter) port? I plan to flare the port ends, both of them.
Thanks for all.
I got some bugs worked out on my end and I'm ready to learn some of the finer points in the worksheet.
I'm using the ML-TQWT sheet. I saw that my Port Air Velocity was above the recommended 0.03. So I changed from a 3" port to a 4". The switch requires lengthening the port to ~16". Fitting this length of port into my case requires I turn it 90 degrees and up.
Does the location of the entry of the port inside the case affect the validity of the results?
If the length of the port is included in the path length of the wave, should I include this in my considerations for setting Z (driver or port)?
As the Port Air Velocity I was obtaining was ~0.04, would it be better to retain the smaller (and shorter) port? I plan to flare the port ends, both of them.
Thanks for all.
Ed, what sort of speaker are you trying to design? What driver are you using? A 16in port length IMO is excessive in the extreme, and you might be trying to do something with a driver that's better suited to another type of enclosure, or the box will need dramatic resizing.
Best
Scott
Best
Scott
Scott,
I'm trying to place Jon Marsh's Modula MTM in a TL. The modeling is based on the combined parameters of two RS180 mid-bass.
fd = 39 hz
Re = 3.2 ohm
Lvc = 0.375 mH
Bl = 6.62
Sd = 245 cm(cm)
Vad =48.75 liter
Qed = 0.49
Qmd = 1.62
Maybe this is a case of expecting to much from the drivers? Not enough x-max?
L = 43 in
Zdriver = 11
Zport =30
So = 14 x 7.5
Sl= 14 x 7.5
Dens = 0.35
r port = 2.0
Lport = 16
I'm trying to place Jon Marsh's Modula MTM in a TL. The modeling is based on the combined parameters of two RS180 mid-bass.
fd = 39 hz
Re = 3.2 ohm
Lvc = 0.375 mH
Bl = 6.62
Sd = 245 cm(cm)
Vad =48.75 liter
Qed = 0.49
Qmd = 1.62
Maybe this is a case of expecting to much from the drivers? Not enough x-max?
L = 43 in
Zdriver = 11
Zport =30
So = 14 x 7.5
Sl= 14 x 7.5
Dens = 0.35
r port = 2.0
Lport = 16
Greets!
FYI, 5% mach (~17 m/s if it's notated like in Lspcad) is plenty good enough for all but some high SPL prosound apps, with 10% being consider fine for when Fb is either below the intended BW or the speaker will be XO'd to a lower BW system.
GM
FYI, 5% mach (~17 m/s if it's notated like in Lspcad) is plenty good enough for all but some high SPL prosound apps, with 10% being consider fine for when Fb is either below the intended BW or the speaker will be XO'd to a lower BW system.
GM
That would equate to 17/342 = ~ 0.05 in the Port Air Velocity graph. GM, thanks for the reality check.
An externally hosted image should be here but it was not working when we last tested it.
Am I ready to build this? A test enclosure? It is an ML-TQWT. Corrected SPL Response for the System. Baffle step is included. My question is really: What is the greatest problem I have with this response?
The dips @ 105 & 245 hz "toggle" with one another and are related to the distance off the wall. If I raise the response @ 245 the response goes down @ 105 hz. So for this sim I have "balanced" them.
I am concerned for the ~10 dB between 245 & 400 hz and I'm looking for suggestions. Oh yea, this represents an mtm using their center for the driver location.
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