Thank you!
Lowering the xo to 2 or 1.8kHz wouldn't be an issue. Right now I cross the 8PE21 to the TPL at 1.1kHz. The TPL is great until about 13kHz, then drops fast. So I would probably later change to another, smaller, ribbon or plannar tweeter, than matches well to the chosen midrange. I do want to go top-notch midrange, though.
How wide of a baffle are you using your PTT6.5M in, and what's the lower xo point you use?
BTW, which AMT tweeter are you using?
I'm using 8x 6.5" woofers per side on a SLOB config, like xrk971 has done in his XSD speaker, which works very well up to 470Hz. Plenty of flexibility to integrate midbas to midrange, I think. The SLOB config works really well. The vibration-canceling effect is not to be minimized, nor the sense of impact the slot loading brings to the table.
I use Mundorf AMT 25D1.1 for tweeter.
I use no baffle for PTT6.5M, instead mounting it to open frame using spring. I borrow the idea from one company in Netherlands. Mounting it in no-baffle help extend the dipole effect to higher frequency.
I use no baffle for PTT6.5M, instead mounting it to open frame using spring. I borrow the idea from one company in Netherlands. Mounting it in no-baffle help extend the dipole effect to higher frequency.
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Great info!
Sid you get to listen to them, how were they different and which sound did you prefer?
I am probably going to use a small baffle. I've done 8PE21 nude but was a bit awkward-looking and I didn't hear much of a difference vs using them on a 30cm wide baffle (what I'm using now).
Nice!
This is actually a a nude design I could live with. Are you using 1, 2, or 4 PTT6.5M per side? And how low do you cross them?
I use only one PTT6.5M for midrange from 350Hz-1800Hz. For 120Hz-350Hz is Scan Speak 26W/4867. For 50Hz-120Hz is 2x Faital Pro 12RS430 in V-Frame like LX521. For frequency from 10-50Hz, there are 2x sealed subwoofers with SB Acoustics SB34SWPL (20-50 Hz). My system is basically a beef-up and no-baffle Linkwitz LX521 and two sealed subs.
But right now I have a plan to revise it to get rid of a dip at 180 Hz due to ground bounce.
But right now I have a plan to revise it to get rid of a dip at 180 Hz due to ground bounce.
Ok I understand better 🙂 Yes you have plenty possibilities to test multiple midrange and find the good one 🙂
@jerome69
Nevertheless, your point about not needing a 6.5" mid is a good one. Trung224 is using the 6.5" from 350Hz nude, so the 5" might work well from 450-ish. But then I wonder about the size of the motor and the backwave behavior, while with the PTT6.5M I can have certainty it works well from work done by others.
Nevertheless, your point about not needing a 6.5" mid is a good one. Trung224 is using the 6.5" from 350Hz nude, so the 5" might work well from 450-ish. But then I wonder about the size of the motor and the backwave behavior, while with the PTT6.5M I can have certainty it works well from work done by others.
I think 5" midrange does not cut it in dipole if you crossed at 450-ish. Linkwitz and John.K used a 4" midrange from 1000 Hz, and Sd of them is around 40 cm2. So, it is ok to use a 6.5" midrange with 132m2 of Sd from 350Hz. A 5" midrange like 120mid_vhe with just 55cm2 of Sd IMHO should not be used at 450Hz on dipole design.
Wow, you cross over a Mundorf AMT 25D1.1 at 1.8 kHz??? That is really using it right to the edge (based on the distortion plots in the datasheet)!
@CharlieLaub : You are right, it is right to the edge. That is still my least satisfying thing in my dipole systems, alongside with a dip due to ground bounce at 180Hz. I use LR4 crossover and a current drive amplifier for it, and it is only still acceptable level for me.
Not on topic, but what do you think a best way to get rid of 180Hz dip? I think try to place the 10" lower mid driver to bottom but have a difficulty of placing the dipole V-Frame on top of it.
Not on topic, but what do you think a best way to get rid of 180Hz dip? I think try to place the 10" lower mid driver to bottom but have a difficulty of placing the dipole V-Frame on top of it.
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Regarding the dip... My most recent designs are 3-way dipole plus sealed subwoofer(s). The dipole part is designed to minimize the floor bounce like this:
I ignore any floor bounce effect from the midrange (I just measure its response in a quasi free field type way, far above the ground). This is because (I believe) that our hearing system is designed to recognize a source at some height above the ground and at higher frequencies and will sort of "compensate" for any floor bounce effect as part of the natural hearing process. This is different at lower frequencies like for the woofer.
This type of driver arrangement seems to integrate very well at most any distance. I like that I can "tune" the sealed subwoofer Q and Fb using a Linkwitz Transform so that the low frequency bass energy sounds correct and I still get the nice low end of a monopole. I think this is not too different from the setup that @Juhazi uses for his speakers, with some differences in how he implements the woofer section.
I will definitely build more speakers using the above concept.
- The woofers are used from 60Hz or 70Hz to 350Hz. I use multiple smaller drivers, typically four 8" or 10". There are two pairs per side. Each pair is in a relatively small baffle, for example for 8" drivers the baffle might measure 12" high by 24" wide. The two pairs are placed (as viewed from the listening location) on the floor and are separated in the front-back direction by about 12-14 inches (see attached pic). By placing the drivers very close to the floor like this the floor bounce cancellation can be moved up in frequency above 350 Hz so that it is out of band. By using four drivers I get more Sd*Xmax swept area. Because the baffle area is not enough for these drivers to deliver high SPL below 40Hz, I use the sealed subwoofer for the lowest notes.
- There is a single midrange operating from 350Hz to as high as I can take it, which is usually no more than about 2kHz. The midrange is used nude, about 30 inches or slightly more above the floor.
- The tweeter (a dipole AMT type) is also used nude and located directly above and as close to the midrange as possible.
I ignore any floor bounce effect from the midrange (I just measure its response in a quasi free field type way, far above the ground). This is because (I believe) that our hearing system is designed to recognize a source at some height above the ground and at higher frequencies and will sort of "compensate" for any floor bounce effect as part of the natural hearing process. This is different at lower frequencies like for the woofer.
This type of driver arrangement seems to integrate very well at most any distance. I like that I can "tune" the sealed subwoofer Q and Fb using a Linkwitz Transform so that the low frequency bass energy sounds correct and I still get the nice low end of a monopole. I think this is not too different from the setup that @Juhazi uses for his speakers, with some differences in how he implements the woofer section.
I will definitely build more speakers using the above concept.
Attachments
I built two planar line array systems that both work very well. One of the systems uses the LM8K, floor to ceiling, the other uses two 600mm long planar drivers per side for a 1.2M line length. Both systems cross below 400Hz to a dipole bass section.
A single small planar driver does not have sufficient displacement to achieve your desired crossover point.