which driver suitable for TL?

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silvershadelynx

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#1
Hi,

I finished my electrostatic loudspeaker and I would like to add a woofer to it for lower frequencies. I think I will use a cross over frequency between 300 and 500 Hz.

I'm not sure what type of enclosure would fit best. I'm considering a transmission line woofer. I'm looking for a not too exepensive woofer, about 100 euro / dollar.

I'm thinking about a 8 inch woofer. Would that be a better choice for this application compared to a 6.5 inch woofer? (more radiating area, lower cone excursion, lower reduction?) Which woofer would be a good choice? These are the woofers I'm considering:

Scanspeak 22W/8534G00 (http://www.scan-speak.dk/datasheet/pdf/22w-4534g00.pdf) Fres = 30 Hz, Qts = 0.39

Seas H1252-08 L22RNX/P (H1252-08 L22RNX/P) Fres = 23 Hz, Qts = 0,32

Seas H1208-08 L22RN4X/P (H1208-08 L22RN4X/P) Fres = 21 Hz, Qts = 0,29

Would any of those drivers be suitable for a TL woofer? I'm not sure what T/S parameters make a good TL driver?
 
#2
You will probably get more than one opinion but assuming the specs you posted for the three woofers are reasonably representative of what your drivers would actually measure, I would much prefer the SS woofer, primarily because its Qts is around 0.4 and, more so, because in my experience low-Qts drivers, like the other two, don't model nearly as well in TLs. That's not to say these won't or that someone else might get better results than I've experienced. More to the point, to design the TL as optimally as possible, you should base it on actual measured T/S values for the drivers you use. If the Qts for the SS woofer is indeed 0.4 and its fS is 30 Hz, or close to those values, the optimum tuning frequency of a TL for it will be right around 30 Hz.
Paul

silvershadelynx said:
Hi,

I finished my electrostatic loudspeaker and I would like to add a woofer to it for lower frequencies. I think I will use a cross over frequency between 300 and 500 Hz.

I'm not sure what type of enclosure would fit best. I'm considering a transmission line woofer. I'm looking for a not too exepensive woofer, about 100 euro / dollar.

I'm thinking about a 8 inch woofer. Would that be a better choice for this application compared to a 6.5 inch woofer? (more radiating area, lower cone excursion, lower reduction?) Which woofer would be a good choice? These are the woofers I'm considering:

Scanspeak 22W/8534G00 (http://www.scan-speak.dk/datasheet/pdf/22w-4534g00.pdf) Fres = 30 Hz, Qts = 0.39

Seas H1252-08 L22RNX/P (H1252-08 L22RNX/P) Fres = 23 Hz, Qts = 0,32

Seas H1208-08 L22RN4X/P (H1208-08 L22RN4X/P) Fres = 21 Hz, Qts = 0,29

Would any of those drivers be suitable for a TL woofer? I'm not sure what T/S parameters make a good TL driver?
Click to expand...
 
#4
Low-Qts drivers can work in a TL but usually IMO they work better in straight-forward vented boxes. Do bear in mind that I'm speaking from my experiences in designing TLs for the last 10-15 years and based on how I want the bass response to model; others might have different experiences and opinions.
Paul

zman01 said:
Question to Paul (pkitt) and hope not too much OT:

There are a number of low-Qts drivers in the market - without generalizing too much, what type of cabinet would you recommend using such drivers?
Click to expand...
 
#6
How large an enclosure for these can you afford, and low do you want this part of the system to dig - i.e. will there be a sub-woofer involved for the heavy lifting below, say 40Hz?

Finding a suitable driver is one thing, but not to dissuade your idea, a TL enclosure design capable of extending very deep could get big - would a simple sealed box work with any of the drivers on your short list?
 
#7
Thanks for your answers. Max. volume would be around 150 liters, preferably less. It would be nice if I can use the same driver in both TL and sealed closure for testing and comparison.

I did some sealed enclosure (Q=.577, max flat delay response) simulations in WinISD and compared the Scanspeak 22W/8534G00 with the Seas H1252-08 L22RNX/P and it seems that f = -3dB is at 52 Hz, 50 liter compared to 67 Hz 59 liter for Scanspeak driver.

There won't be a subwoofer involved. I think sealed enclosure will be the easiest and safest option, but I like the idea of TL because of extended lower frequencies and I enjoyed the sound of my previous 2-way TL.

By the way, I found another Seas driver, CA22RNX H1288-08:

H1288-08 CA22RNX

It has a similar f -3dB as the Seas H1252-08 L22RNX/P, but higher Qts and higher volume enclosure (97 liter).

I found a Peerless HDS-205 driver with Qts = 0.41, Fres = 28 Hz and it has f -3 dB @ 52 Hz, enclosure volume = 61 liter:

Data sheet - 835026 | Loudspeaker freaks

Regards, Jeroen.
 
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#8
I just did a quick model for the CA22NRX, based on the specifications you linked, in a tapered TL 70 inches long with a taper ratio of 14:1 and a line volume of 77 liters. Its predicted f3 was right at 35 Hz. Increasing the line volume, while making no other changes would lower f3. I modeled with a starting area of 9"W x 14"D and an ending area of 9"W x 1" D (the terminus at the end of the line is also 9" x 1"). The woofer's center was located 14" from the beginning of the line, and the first 47" of the line are filled with polyester fiber at a density of 0.75 lb/ft3.
Paul
 
#9
I did a simulation on this one: TangBand-Lautsprecher W8Q-1071
You'll have to look at Tang-Bands pages for correct T/S parameters - the Lautsprechershop ones are wrong.

The woofer needs to be crossed a bit lower than you want, and there's still a bit of fiddling with the design left to remove the first resonance dip at ca 110Hz. The woofer is quite cheap - €119, and has good output capabilities...

The cabinet was about 70 litres.

Johan-Kr
 

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#11
I have done some tweaking of the design, and got better results.

In most living rooms of a bit size, you should shoot for a driver that gives you a tuning about 28-30something Hz. The acoustic rolloff, combined with the room gain will net you a useful response an octave - octave and a half below the tuning frequency. I had a pair of huge T-line subs with a 12" in each, with a tuning of around 26-27Hz. They easily did 15-20Hz in-room. The active filter I used had a HP sub filter at 15Hz.

Oh, and a 6,5" is a silly size woofer, for a 3-way. 8" would be the minimum. The beauty of the 8W-Q1071, is that you get a bigger Sd than a 10" in the cabinet width of an 8"...

Johan-Kr
 
#13
Hi, I decided to go for a sealed enclosure. I'm looking for a (mid) woofer but don't know whether I shoud choose a 6.5 inch or 8 inch driver. I would like to have the option to crossover at 500 Hz, although I expect to use a lower cross over frequency. (300 - 400 Hz) Would a 8 inch woofer suitable for such (500 Hz) a high cross over freqency? (for instance this one: 8" SB23NACS45-8 :: SB Acoustics) Or would it have low performance at higher frequencies?

Or would a 6.5 inch driver more suitable, like Scanspeak 18W/8535-00: http://www.scan-speak.dk/datasheet/archive/18w-8535-00.pdf)
 
#14
Guys, about TL, I have my doubt, PMC MB2 uses Volt RV3143, specs says this MB2 goes down to 20hz, and the fs of this driver is 35hz, so this speaker goes down lower than the fs. This is why I don't trust TL. (Of course we could choose some Scan 13" which fs is samller than 19hz)
 
#15
Keep in mind that when a manufacturer says the response "goes down to XX Hz", that doesn't say anything more than the driver is outputting a signal there, and certainly doesn't tell you how many dB the output is down at XX Hz.
Paul

mtoc said:
Guys, about TL, I have my doubt, PMC MB2 uses Volt RV3143, specs says this MB2 goes down to 20hz, and the fs of this driver is 35hz, so this speaker goes down lower than the fs. This is why I don't trust TL. (Of course we could choose some Scan 13" which fs is samller than 19hz)
Click to expand...
 
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