I did a simulation for a triangular baffle with 80 cm base and 120 cm to the top. All drivers are at their intended positions on the baffle with their true radiating areas. Individual TSP don't apply of course:
On a flat baffle the 21" driver would have its dipole peak at >300 Hz. You could double the effective baffle width to raise the bass efficiency and lower the dipole peak to your intended Xover of 150 Hz.
The mid has its dipole peak at ~700 Hz. Your intended xover of 1500 Hz is at the position of the first dipole null. Ideally the midrange driver should be smaller (and the baffle at the driver height too), but the W22 looks like a good enough compromise.
The TPL150 may be a great driver, but its baffle dimensions are those of a midrange driver - not a tweeter. This causes the dipole peak to be much below the desired frequency. The falling response at 1800-3800 Hz (on axis) will show up at rising frequencies for rising angles and can't be consistently equalised.
I have added a 20 mm dome tweeter in the top of the triangle - it would theoretically give a much better radiation pattern. For this application I would possibly prefer tweeters like the Visaton SC4 ND (or better ones of same small dimensions) mounted back to back in the top of the OB.
An externally hosted image should be here but it was not working when we last tested it.
On a flat baffle the 21" driver would have its dipole peak at >300 Hz. You could double the effective baffle width to raise the bass efficiency and lower the dipole peak to your intended Xover of 150 Hz.
The mid has its dipole peak at ~700 Hz. Your intended xover of 1500 Hz is at the position of the first dipole null. Ideally the midrange driver should be smaller (and the baffle at the driver height too), but the W22 looks like a good enough compromise.
The TPL150 may be a great driver, but its baffle dimensions are those of a midrange driver - not a tweeter. This causes the dipole peak to be much below the desired frequency. The falling response at 1800-3800 Hz (on axis) will show up at rising frequencies for rising angles and can't be consistently equalised.
I have added a 20 mm dome tweeter in the top of the triangle - it would theoretically give a much better radiation pattern. For this application I would possibly prefer tweeters like the Visaton SC4 ND (or better ones of same small dimensions) mounted back to back in the top of the OB.
Hello Erik,
I love your design, I was looking at something very similar when I first started desgining my dipole. I'm currently using the old 'Great Heil' AMT, but would love something I could mount to a baffle. It would certainly allow me some latitude in the design department. I've had my eye on those Beyma's since they came out.
I had originally looked at some 18's, then 21 inch drivers. Of the 21's I plugged into XLBaffle, I could never get one to model much better than a good 18. I haven't plugged the new Beyma's parameters into that spreadsheet, but do you expect mech better output than the 18's. Also noticed the inductance was a little high, how high up do you plan on running the 21's?
I love your design, I was looking at something very similar when I first started desgining my dipole. I'm currently using the old 'Great Heil' AMT, but would love something I could mount to a baffle. It would certainly allow me some latitude in the design department. I've had my eye on those Beyma's since they came out.
I had originally looked at some 18's, then 21 inch drivers. Of the 21's I plugged into XLBaffle, I could never get one to model much better than a good 18. I haven't plugged the new Beyma's parameters into that spreadsheet, but do you expect mech better output than the 18's. Also noticed the inductance was a little high, how high up do you plan on running the 21's?
Stig Erik?
Did you measure the TPL-150 before you removed the rear chamber?
I would really like to see if their graph are anything near the one Beyma publishes.
I would also like to know the price of a pair in Norway
I own a pair Morel H10.1 drivers i belive could work well together with the TPL-150 in a sealed 2 way setup
Did you measure the TPL-150 before you removed the rear chamber?
I would really like to see if their graph are anything near the one Beyma publishes.
I would also like to know the price of a pair in Norway
I own a pair Morel H10.1 drivers i belive could work well together with the TPL-150 in a sealed 2 way setup
Rudolf said:
Great, thanks a lot!
Our intended baffle is 80 cm side at the bottom. We will make wings (point rearwards) to increase the effective width, the wings can be up to 40 cm long, actually doubling the effective width.
I'm comfortable with the measured performance of the mid, so we'll keep it like that.
Regarding the tweeter... its radiation pattern is not spherical like a dome. How will this affect the simulation? Making the tweeter baffle narrower is almost impossible, as the drivers front plate is 120 mm wide.
FE3T said:
Yes, I have measured it with the chamber, both with a baffle and without baffle. The baffle affects the rear end (below 2-3 kHz) a lot. On a wide (40 cm or more) baffle, the TPL150 measures a lot like Beyma's own measurements.
You can buy these drivers from me for NOK 3000 each plus shipping.
Hi Scott and StigErik,
Scott,
Thanks for the links to the old Adire article on driver speed, I read them with interest years ago after I met Dan at a CES or Denver show about 5 years ago.
I was sad to see the demise of Lambda and Adire.
Dan and John are indeed very clever driver designers and I have great respect for their new Acoustic Elegance drivers, I hope to have a chance to evaluate a pair of TD12M drivers soon.
Interesting that their new flagship drivers (TD 12 M & TD15M ) feature ultra low Mms to high Bl ratio's….!
50g over 17Bl = 2.94 for the TD12M one of the lowest Mms to Bl ratios of ANY Pro 12 inch driver.
Ditto the TD15M 70g over 17 Bl a great figure of 4.1, most 15 inch pro drivers are in the 5 or 6 bracket.
Maybe they have come around to my way of thinking….!
I first published my theory on this subject on my website in Jan 2005….
I am in full agreement with Dan and Nick that the lowest possible inductance is a valuable goal and will reduced stored energy therefore increase speed & lower distortion.
BUT, that is not the whole story, not even the most important chapter...! This is a very important subject, it was in my opinion THE most important issue in driver design until last week when MG sent me his Thermal Compression white paper...!
I don’t want to go off topic on this thread so I will start a new thread on driver design. I will put forward my views on the Mms to Bl ratio, the importance of low VC inductance, thermal compression (hopefully with the help of Michael Gerstgrasser!) aerodynamics, efficiency, power handling and materials.
That should be a good "cat among the pigeons"
StigErik,
The Beyma 18G50 (not the 18G550) is a very fast driver: Mms170g over Bl of 28.8 = 5.9. Great result for an 18 inch power house pro driver.
The 15 inch SM 115 K I am using = 5.1,(17% "better" ) but your 18 inch has 50% greater Sd therefore only has to travel 50% as far for the same Vd so your 18 G50 is actually 33% faster than the smaller and lighter SM115K!
The 18 G50 is a great open baffle driver and I would be Oh so interested to see how the measurements compare and more importantly how the sound quality compares to the 21 inch Beyma driver. Again Plleeeese post the measurements!
My point is that only in a "like for like" ie same Sd for same Sd, the lower the ratio the faster the driver. This assumes all other parameters being equal (Efficiency, Thermal compression, VC Le, etc) which they never are...!
All the best
Derek.
Scott,
Thanks for the links to the old Adire article on driver speed, I read them with interest years ago after I met Dan at a CES or Denver show about 5 years ago.
I was sad to see the demise of Lambda and Adire.
Dan and John are indeed very clever driver designers and I have great respect for their new Acoustic Elegance drivers, I hope to have a chance to evaluate a pair of TD12M drivers soon.
Interesting that their new flagship drivers (TD 12 M & TD15M ) feature ultra low Mms to high Bl ratio's….!
50g over 17Bl = 2.94 for the TD12M one of the lowest Mms to Bl ratios of ANY Pro 12 inch driver.
Ditto the TD15M 70g over 17 Bl a great figure of 4.1, most 15 inch pro drivers are in the 5 or 6 bracket.
Maybe they have come around to my way of thinking….!
I first published my theory on this subject on my website in Jan 2005….
I am in full agreement with Dan and Nick that the lowest possible inductance is a valuable goal and will reduced stored energy therefore increase speed & lower distortion.
BUT, that is not the whole story, not even the most important chapter...! This is a very important subject, it was in my opinion THE most important issue in driver design until last week when MG sent me his Thermal Compression white paper...!
I don’t want to go off topic on this thread so I will start a new thread on driver design. I will put forward my views on the Mms to Bl ratio, the importance of low VC inductance, thermal compression (hopefully with the help of Michael Gerstgrasser!) aerodynamics, efficiency, power handling and materials.
That should be a good "cat among the pigeons"
StigErik,
The Beyma 18G50 (not the 18G550) is a very fast driver: Mms170g over Bl of 28.8 = 5.9. Great result for an 18 inch power house pro driver.
The 15 inch SM 115 K I am using = 5.1,(17% "better" ) but your 18 inch has 50% greater Sd therefore only has to travel 50% as far for the same Vd so your 18 G50 is actually 33% faster than the smaller and lighter SM115K!
The 18 G50 is a great open baffle driver and I would be Oh so interested to see how the measurements compare and more importantly how the sound quality compares to the 21 inch Beyma driver. Again Plleeeese post the measurements!
My point is that only in a "like for like" ie same Sd for same Sd, the lower the ratio the faster the driver. This assumes all other parameters being equal (Efficiency, Thermal compression, VC Le, etc) which they never are...!
All the best
Derek.
It's interesting then that one of the slowest woofers I've heard, got a Mms/BL ratio of just 2,5 (Seas CA25FEY)....
I don't think that its just ONE parameter that affects the subjective impression of "bass speed". This most important in my opinion is the frequency response through the 100-500 Hz range, especially the transition between the woofer and midrange driver, which is the case of our dipole happens at 200 Hz. (we changed it from 150).
Best,
Stig Erik
I don't think that its just ONE parameter that affects the subjective impression of "bass speed". This most important in my opinion is the frequency response through the 100-500 Hz range, especially the transition between the woofer and midrange driver, which is the case of our dipole happens at 200 Hz. (we changed it from 150).
Best,
Stig Erik
Rudolf said:
Rudolph, good and very illustrative sims to get some first feeling for the issues of OB
- just wanted to add that the position of the 20mm dome (proposed as an alternative) here, you assumed to be in the *very* top of the magicians hat.
More or less like a freestanding tweeter on top.
Placed at the same position as the AMT now - sim looks pretty much the same.
Also traces of EDGE usually look slightly too dramatic as the default scale is pretty "zoomed in".
So, I suggest to stay cool and not to overemphasis sim results over Stig's auditioning.
I'd definately would give both shapes a go.
There is also an - not so widely known - alternative to EDGE when it comes to simulation of baffle edge diffraction.
A spread sheet written by John Kreskovsky - more precise in its prediction but also with a slightly steeper lerning curve.
Michael
StigErik said:
If you do a ratio of mass (mms) to force/Ampere (BL) you basically get something equivalent to acceleration of the cone for a given current.
As the SPL depends on the area of the diapragm as well - above makes kind of sense when comparing same size only (as already said).
If you factor in diaphragm area too - you end up with something equivalent to the drivers efficiency.
At that point I have given up to look at mms/BL
Having a closer look at the FR at 100 to 500 seems like a good idea to me - might be that the phase shift in this area plays a role - just a (new) guess.
Michael
Seas driver
Hi StigErik,
I have never used the Seas 10 inch CAF25FEY so I can only guess from a quick look at the spec sheet.
But one look at the 39mm voice coil says it all.... this is a midrange driver not a woofer!
Any serious power below 120Hz ( ish ) will stress the driver and send it into ocillation and severe thermal compression.
This driver will sound like mud in a food blender!
I never bother even testing bass drivers if they dont have at least a 3 inch (75mm) voice coil, all the good ones I have found have 4 inch or 5 inch coils.
Very few "audiophile" drivers can actually handle real bass power.
The Beyma 12LX60 (now discontinued) was my all time favourite bass/ low mid driver. Power speed texture and fast enough to crossover to the Manger at 300Hz, you know cause you heard it in the Encore!!
All the best
Derek.
Hi StigErik,
I have never used the Seas 10 inch CAF25FEY so I can only guess from a quick look at the spec sheet.
But one look at the 39mm voice coil says it all.... this is a midrange driver not a woofer!
Any serious power below 120Hz ( ish ) will stress the driver and send it into ocillation and severe thermal compression.
This driver will sound like mud in a food blender!
I never bother even testing bass drivers if they dont have at least a 3 inch (75mm) voice coil, all the good ones I have found have 4 inch or 5 inch coils.
Very few "audiophile" drivers can actually handle real bass power.
The Beyma 12LX60 (now discontinued) was my all time favourite bass/ low mid driver. Power speed texture and fast enough to crossover to the Manger at 300Hz, you know cause you heard it in the Encore!!
All the best
Derek.
Derek,
Good to hear that you agree with me that there is more to it than just Mms / BL ratio.
Seriously - I've never gotten good quality bass from anything but large powerful PA woofers, so we have the same experience there. I also liked the 12LX60 a lot, but I think the new 12P1000nd is even better.
Back to our speaker again. My friend Lars with whom I am co-building this thing, came for an audition tonight. I've worked somewhat with the XO and EQ since his last audition. His feedback was very positive indeed! He really likes the way it presents the stereo image as well as the fabulous resolution of the Beyma TPL, the tonal balance and bass quality. What we need to work on is a slight lack of "speed" and "attack" in the upper bass. I think the solution is to be found with a much better baffle than our very flimsy pine board. Time will show. I will build a much stiffer MDF baffle, and we will take it from there.... a final design for prototype version two will be ready soon I hope, based on input from several people in this thread.
Good to hear that you agree with me that there is more to it than just Mms / BL ratio.
Seriously - I've never gotten good quality bass from anything but large powerful PA woofers, so we have the same experience there. I also liked the 12LX60 a lot, but I think the new 12P1000nd is even better.
Back to our speaker again. My friend Lars with whom I am co-building this thing, came for an audition tonight. I've worked somewhat with the XO and EQ since his last audition. His feedback was very positive indeed! He really likes the way it presents the stereo image as well as the fabulous resolution of the Beyma TPL, the tonal balance and bass quality. What we need to work on is a slight lack of "speed" and "attack" in the upper bass. I think the solution is to be found with a much better baffle than our very flimsy pine board. Time will show. I will build a much stiffer MDF baffle, and we will take it from there.... a final design for prototype version two will be ready soon I hope, based on input from several people in this thread.
StigErik said:
Hi,
May I suggest the T-bass circuit?
Here:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=130679
If you have some spare time, try the T-bass for yourself, please. All parts can be recycled if regret, nothing is wasted. And you'll have a wonderful experience for the time you spend.
Although some doubts out there, I've seen NO unpleasant response from the real T-bass users. Isn't that interesting?
All tech talks and experience sharings have been posted in that thread, so no repeating here.
Just try it. It's a free and wonderful gift.
Although some doubts out there, I've seen NO unpleasant response from the real T-bass users. Isn't that interesting?
All tech talks and experience sharings have been posted in that thread, so no repeating here.
Just try it. It's a free and wonderful gift.
Question for StigErik
Hi StigErik,
I have a question regarding the TPL-150 (it's somewhat of topic, so if it interferes to much with the thread, then just disregard my question).
I consider using the TPL-150H in an system using active (digital) crossovers all through. My question is the following:
If running the TPL-150(H) actively, would you use a large cap on the TPL for protection, or is it not necessary?
Thanks!
Best regards
Peter
Hi StigErik,
I have a question regarding the TPL-150 (it's somewhat of topic, so if it interferes to much with the thread, then just disregard my question).
I consider using the TPL-150H in an system using active (digital) crossovers all through. My question is the following:
If running the TPL-150(H) actively, would you use a large cap on the TPL for protection, or is it not necessary?
Thanks!
Best regards
Peter
Re: Question for StigErik
a) If your amps blow and/or send DC, you might kill the driver. In such a case you might kill a midrange or even a woofer as well. A series cap will usually protect the tweeter in such cases.
b) If you mess around with the XO and accidentially send full frequency signal at high power to the tweeter, it might blow. This has happened to me once, and its not fun at all.... If you make sure that everything is ok BEFORE you apply signal/music, then you're safe.
c) Never connect tweeters to audio card channels 1/2, as they may be default audio devices in your operating system. Hearing the first second of the Windows startup sound at full power through your tweeters, and then sudden silence is no fun either.
It depends on how cool you are... I dont use protecting caps.pk said:
a) If your amps blow and/or send DC, you might kill the driver. In such a case you might kill a midrange or even a woofer as well. A series cap will usually protect the tweeter in such cases.
b) If you mess around with the XO and accidentially send full frequency signal at high power to the tweeter, it might blow. This has happened to me once, and its not fun at all.... If you make sure that everything is ok BEFORE you apply signal/music, then you're safe.
c) Never connect tweeters to audio card channels 1/2, as they may be default audio devices in your operating system. Hearing the first second of the Windows startup sound at full power through your tweeters, and then sudden silence is no fun either.
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