Need help selecting driver for hi-efficiency 2-way

[Alien_Shore]

I am a big fan of high-efficiency speakers. My den has Altec Model 14s, and in the man cave, I'm running a large pro audio VOTT-like setup. What I'd like to build is a smallish 2-way speaker using high efficiency drivers and horns; the basic idea is a Geddes Harper clone. I already have the B&C DE250 HF drivers, and am thinking of using the Dayton 8" waveguide with them. The specs for that waveguide recommend crossover point >= 2.2K. For the woofer, I am thinking of an 8" high-efficiency (>90 dB sensitivity) driver, with a good Qts, and minimal breakup in my XO range. Here are the drivers I've looked at so far:

Driver	Price	FR	Sens	Qts	Xmax	EBP	$/Qts
MCM 55-3550	$40	30-8K	92	0.17	1.5	171	$48
Dayton DS215-8	$43	35-4K	90.1	0.34	5.5	90	$65
Eminence Eminator 1508	$35	90-4.4K	93.4	0.59	3.3	112	$85
Celestion TF0818	$50	70-6K	94	0.44	3.5	190	$89
Dayton PA200-8	$41	70-9K	92	0.59	3	100	$100
Eminence Delta Pro-8A	$90	100-3K	97.8	0.22	3	345	$115
Selenium 8PW3-SLF	$43	70-8K	92	0.66	2.4	97	$126
FaitalPro 8FE200	$48	60-5K	95	0.63	4.7	121	$130
Dayton ST210-8	$70	45-3K	90	0.49	5.6	96	$137
PRV 8MB500	$73	62-4K	95	0.52	3.5	110	$152
PRV 8MB600	$75	76-6K	95	0.51	6	141	$153
Beyma 8BR40	$66	35-6K	90	0.57	6	45	$153
B&C 8PS21	$107	70-3K	94	0.33	5	203	$160
Beyma SM-108N	$110	65-6K	95	0.32	4	188	$162
B&C 8NDL51	$117	65-3K	94	0.37	7	161	$186
Dayton PM220-8	$127	43-10K	95	0.34	4.6	123	$192
Aurum Cantus AC200/50C2C	$149	27-4.5K	90	0.26	6	96	$201
B&C 8BG51	$127	50-4K	92	0.4	6.5	124	$212
RCF MB8G200	$149	60-4K	94	0.33	6	205	$222
18Sound 6ND430	$150	63-5.5K	92.5	0.39	5	150	$246
RCF L8S800	$149	50-4K	93	0.41	5.8	130	$253
Beyma 8P300Fe	$170	50-8K	95.4	0.33	6	179	$254
18Sound 8MB500	$150	60-4.5K	95	0.43	6	164	$263

The Dayton designer series looks good for a "best Q for the buck". But my $/Qts ratio isn't a perfect predictor; obviously the Aurum would be a fantastic woofer, but I'd like to keep the price down if the audible differences aren't going to be huge.

[Taran]

Re: Need help selecting driver for hi-efficiency 2-way

There's also the Eminator 8's that might work for you and they are cheap.

[lorenmjones]

Re: Need help selecting driver for hi-efficiency 2-way

Why not just the Fusion 8 at diysoundgroup. Jeff B design, the waveguide is acclaimed, cabinet is .6 cf. 94 db efficiency. It should be just what you were looking for; why reinvent the wheel. You wouldn't get to use your DE250's though. Sell them and it will pay for half the project. The Alpha 8 Minion might be nice too.

http://www.diysoundgroup.com/wavegui...sion8-kit.html

http://www.diysoundgroup.com/wavegui...lpha8-kit.html

[djg]

Re: Need help selecting driver for hi-efficiency 2-way

Geddes and SEOS don't get along.

[donc]

Re: Need help selecting driver for hi-efficiency 2-way

You may check into the 18sound and beyma 8's on usspeaker.com ,18sound also has a great wave guide , sound group's are proven designs and prices are extremely fair
,donc

[greywarden]

Re: Need help selecting driver for hi-efficiency 2-way

The Faital Pro is more efficient than most on the list, has a higher xmax than the others, and also has a smoother response than most, and is also cheaper than most.

[Alien_Shore]

Re: Need help selecting driver for hi-efficiency 2-way

There's also the Eminator 8's that might work for you and they are cheap.

Thanks for the suggestion; that driver does fit my criteria fairly well: 93 dB sens, 90-4.4K FR, 0.59 Qts.

Why not just the Fusion 8 at diysoundgroup. Jeff B design, the waveguide is acclaimed, cabinet is .6 cf. 94 db efficiency. It should be just what you were looking for; why reinvent the wheel. You wouldn't get to use your DE250's though. Sell them and it will pay for half the project. The Alpha 8 Minion might be nice too.

Thanks Loren - I had not seen those designs, and being able to get the CNC baffles is a real plus since I don't have a router (or know how to use one!). The thing is that I really do want the experience of modeling the drivers and the crossovers. I really enjoy designing the crossovers in particular, so am looking forward to trying it for this build. The enclosure design is what I know the least about. I've just started working with WinISD over the last month, so I'm ramping up, but there's a lot of complexity there especially about baffle design that I need to learn.

You may check into the 18sound and beyma 8's on usspeaker.com ,18sound also has a great wave guide , sound group's are proven designs and prices are extremely fair
,donc

Thanks, Don. The Beyma 8P300Fe is interesting. Pricey, but great sensitivity, Qts, and wow a 6 mm Xmax. The only thing that catches my eye is that big dip at 2.8K on the FR curve there. Is that a cone breakup? That would be bad since my XO will be in that area, right?

That 18sound 8MB500 speaker looks good spec-wise as well, and I like the FR curve better. Both speakers are about the same price. Thanks for pointing those out.

The Faital Pro is more efficient than most on the list, has a higher xmax than the others, and also has a smoother response than most, and is also cheaper than most.

How do you think that FaitalPro compares to the Eminator, Beyma, or the 18sound? Certainly looks more affordable!

[fatmarley]

Re: Need help selecting driver for hi-efficiency 2-way

The Faital Pro is more efficient than most on the list, has a higher xmax than the others, and also has a smoother response than most, and is also cheaper than most.

I could be wrong but I swear blind I read somewhere that the Faital pro specs aren't as good as they look on paper.

[[email protected]]

Re: Need help selecting driver for hi-efficiency 2-way

For the woofer, I am thinking of an 8" high-efficiency (>90 dB sensitivity) driver, with a good Qts, and minimal breakup in my XO range. Here are the drivers I've looked at so far:

Another driver from Dayton Audio to add to your table is the PM220-8, if you intend to prioritize maximum efficiency over the extremely high power handling of a pro driver. The PM220-8 has a very high sensitivity that is excellent for use with tube or low power solid state amplification.

Since you are using a horn-loaded HF section, if you are not comfortable with designing around a driver's breakup you should be able to stay well away from the breakup of the PM220-8 cone with your crossover design.

[Mayhem13]

Re: Need help selecting driver for hi-efficiency 2-way

I second the Dayton 220......but not the 8" round waveguide. There's an excellent tractix elliptical from Faital that would allow for a much lower cross through both directivity and a closer C to C spacing. It's now available here on PE and sounds very smooth with no horn honkiness whatsoever. Construction is also top notch.

[Alien_Shore]

Re: Need help selecting driver for hi-efficiency 2-way

Another driver from Dayton Audio to add to your table is the PM220-8, if you intend to prioritize maximum efficiency over the extremely high power handling of a pro driver. The PM220-8 has a very high sensitivity that is excellent for use with tube or low power solid state amplification.

Since you are using a horn-loaded HF section, if you are not comfortable with designing around a driver's breakup you should be able to stay well away from the breakup of the PM220-8 cone with your crossover design.

Added, and thanks for the tip, Rory. Agree that the PM220 looks like a great choice.

I second the Dayton 220......but not the 8" round waveguide. There's an excellent tractix elliptical from Faital that would allow for a much lower cross through both directivity and a closer C to C spacing. It's now available here on PE and sounds very smooth with no horn honkiness whatsoever. Construction is also top notch.

There are a couple of those tractix, an 80x70 and 60x50. And on the usspeaker site, there's tons of them. It's a bewildering amount of choices. How does one go about narrowing down the selection for an ~1CF enclosure with an 8" woofer? Are there reliable performance numbers posted anywhere?

[mdocod]

Re: Need help selecting driver for hi-efficiency 2-way

Allen,

I just went through the same process myself and landed at: Celestion TF0818 (how is this missing from the list!!?): $50!!! (I just had 5 of these, along with a LOT of other goodies show up from PE today so I can start on my cinema speakers).

The number you are looking for is probably not Qts, it's probably EBP. The relationship between Fs and Qes will determine your efficiency/bandwidth trade-off. One thing you will learn playing on the EBP slopes is that, direct radiator sound reproduction really does come down to a simple basic rule of displacement. EBP just defines the transition region from resonant to damped characteristics. High EBP can be perfectly fine with wide bandwidth goals but will require greater equalization or correction, or an increase in acoustic impedance provided by box design, or some combination... The Celestion drivers I am using for my cinema speakers have an EBP of like 190 IIRC. I'm tuning them to 80hz in a reflex box to extend the usable bandwidth without EQ/correction. I have no need for response below 80hz from these so this is a good solution in my application.

This MCM unit is also worth a look: http://www.mcmelectronics.com/produc...-3550-/55-3550

Other contenders: PRV 8MB600 (I don't know anything about PRV but this appears to share a lot in common with drivers at twice the price)
RCF L8S800 (pricey!)
RCF MB8G200 (also pricey!)
Eminence Alpha and Beta 8 series (nothing particularly wrong with either of these options for a build like this)



Keep in mind that you have a lot of drivers in the list whose manufacturers use different methods of determining "Xmax" so be careful... The celestion T0818 has "~5mm" Xmax the way that most other companies determine it.


---------------

Greywarden,

Make sure to compare Xmax apples to apples. The celestion TF0818 has 3.5mm of linear Xmax. The faital pro 8FE200 is rated more, but only has 2mm of linear Xmax. (see gap vs coil length in detailed specs for each driver).

---------------

I picked the celestion T0818 for my similar project because of the following considerations:

1. Highest (linear) Xmax in the "high EBP" class of reasonably priced 8" drivers.
2. Most "fancier" [and much more expensive] 8" pro drivers (RCF, B&C, faital, beyma, etc) listed as having 5-7mm Xmax tend to be basing this on +25-33% gap length calculations, so have very little advantage over the TF0818 for *actual* linear displacement.
2. Bumped and vented motor design
3. Good stamped frame design (as good as it gets for a stamped design IMO, very "open" design).
4. Appears to have smooth response to 3K.
5. Kevlar in the cone for bragging rights. (yea, it's sort of like a B&W speaker, you know, kevlar and stuff! [/sarcasm-off])
6. Double roll surround is common to more expensive drivers, [read: not a "typical" cheap accordion surround common to cheap entry level pro-sound drivers)

[lorenmjones]

Re: Need help selecting driver for hi-efficiency 2-way

You could also check out the 18Sound 6ND430. It is a very high quality 6.5" pro midbass. It's Qts is low and it's EBP is high. Xmax is 5mm linear. 92db sensitivity. 200w AES power handling. I know it's only 6" but it should do over 110 db continuous which is plenty I would think. If I model it in 10 liters tuned to 80hz it gets you an F3 of 75 hz.

http://www.eighteensound.com/index.a...simple&pid=243

Zaph was pretty positive about their performance when he tested them he said "Excellent performing 16 ohm pro midwoofer. Smooth response and an extremely clean midrange. Very usable T/S parameters and excursion though somewhat limited bass extension for what is meant for woofer service. Very sensitive. It would make a fine midrange also. Lightweight neo magnet assembly with cooling fins. A couple of these paired up for an MTM and used with a subwoofer would make a reference level system. High value for this level of performance. Tested August 2008." Here is the link...

http://www.zaphaudio.com/6.5test/

They are around $149 though. They are available in 4,8 and 16 ohm. I am using a pair of the 8 ohm as midranges in my main speakers and they are very very nice. If you want 8" and the price isn't too much then the 18Sound 8MB500 which is 95 db, gives a similar F3 (larger box though). The 8" is also 149 at USSpeaker.

[Alien_Shore]

Re: Need help selecting driver for hi-efficiency 2-way

I just went through the same process myself and landed at: Celestion TF0818 (how is this missing from the list!!?): $50!!! (I just had 5 of these, along with a LOT of other goodies show up from PE today so I can start on my cinema speakers).

The number you are looking for is probably not Qts, it's probably EBP.

Thanks. I added EBP to my chart. If I understand correctly EBP is primarily useful for determining alignment, and not so much of a stand-alone indicator of relative quality or performance, but valuable as an additional parameter to evaluate upon. As far as the Celestion goes, it's a good-looking driver, but the Fs of 95 when then FR range starts at 70 is curious. Do you have an FR plot for this driver? [edit: n/m found it on the vendor spec sheet]

You could also check out the 18Sound 6ND430...I am using a pair of the 8 ohm as midranges in my main speakers and they are very very nice. If you want 8" and the price isn't too much then the 18Sound 8MB500 which is 95 db, gives a similar F3 (larger box though). The 8" is also 149 at USSpeaker.

Thanks for the tip. The list is growing

[mdocod]

Re: Need help selecting driver for hi-efficiency 2-way

Hi Mike,

EBP is a very misunderstood specification. Ask 10 audio hobbyists what it means and 9 will respond with something along the lines of; "it's for determining suitability for sealed or vented."

There is nothing particularly incorrect about that understanding, however, it is an oversimplification that I believe often leads to a greater misunderstanding about drivers that can lead people on endless searches for a mystical driver that appears to be "better" than the rest on paper.. All speaker drivers must adhere to the same physics, so there aren't any drivers out there that cheat something out of a crack in the universe. If you understand what EBP actually means, then you can stop wasting time on an endless journey for a driver that breaks the rules. I'm not sure what the best way to explain it is so I'll give it a go:

The more motor strength in a driver (Qes), the more SPL is produced for a given input when playing a frequency in the drivers resonant pass-band. The same motor strength that buys the additional output in the resonant pass-band, also acts as a stronger dampener when playing below the resonant pass-band. EBP is the frequency where the transition between these 2 behaviors takes place. All things being equal, raising motor strength will increase the transition region (raise EBP). It's common practice to modify the acoustic impedance on a driver in order to extend the resonant behavior of the system down to a lower register. This is accomplished with more sophisticated box design (reflex, transmission line, tapered transmission line, etc etc). In the case of a driver that is already operating with a resonant behavior at a lower register (low EBP drivers), adding additional resonant behavior to the system is not typically desirable, which is why these drivers are often considered best for use in less sophisticated box designs (IB/OB/sealed).

When comparing a bunch of EQUAL size drivers, the drivers with higher EBP should almost always have higher efficiency. Only in cases where there is a substantial difference in mechanical dampening would there be a case where a driver with higher EBP might NOT be more efficient than the driver with lower EBP (this would be rare, and require drivers to be very similar to begin with)...

Drivers can not be effectively compared in a chart like the one you are building unless you standardize/normalize all of the specifications. When you do actually standardize/normalize all of the specifications, you will likely come to a rather bland discovery- that there is no free lunch, that there is ALWAYS a trade-off, and that there is no mystical/magical stuff going on with any of the drivers. If it's "too good" to be true, it probably is. If you were to normalize all of the sensitivity specs to the same standard, you would see a steadily rising efficiency with rising EBP in the chart. No driver would stand out as particularly "special," only "different."

Currently, the list contains sensitivity ratings produced via at least 3 different "methods," as well as Xmax ratings produced via at least 4 different methods. So some drivers "appear" to be doing a lot more than others on paper (I assure you they aren't).

I think you will be best served by picking a bandwidth goal first, then deciding how you want to achieve that bandwidth. High EBP does not mean that a driver can't be used for wide bandwidth (low frequency extension), but it CAN complicate the issue, requiring greater sophistication to implement (box design or EQ/DSP etc). Once you have decided what EBP class you want to tackle in your design to achieve a particular result, THEN you can start comparing the few drivers remaining. This is the point where research about some of the inner details of each driver is worth a look. Different cone materials with different distortion profiles (wonky breakup issues?). Special design in the motor to maximize linearity, etc etc.. Not always the case but often spending more bucks means that the available displacement is usable with less distortion than on cheaper drivers as more care has gone into the design of the motors on the expensive drivers.

Of interesting note is that MCM driver, the cheapest in the list, also has the lowest Qts. What does this tell you about the relationship between Qts and driver "quality?" Having a higher or lower Qts doesn't mean "worse" or "better," it means "different." Note the tradeoff that the MCM driver had to endure to achieve the very high motor strength [very little coil overhang].. If you're really a Qts junky, look for under-hung motor designs that saturate the entire VC inside the gap. Not sure if there are any 8" midbass drivers out there with underhung motors or not but if you find one it might be worth a look just to tickle a curiosity.

Eric




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lornmjones,

The 6ND430, has it's Xmax calculated via (Hc-Hg)/2+Hg/4 method. [see the datasheet].... Is it "linear?" Well.... depends on which standard (if any) we are holding the concept to. Again, apples to apples ;)

On a side note, I have mixed feelings about how 18sound gives their response plots based on an on-box installation rather than on an infinite baffle. This limits the usefulness of the data IMO as it includes diffraction for a specific baffle design. The data would not be useful for designing your own speaker unless it had the same baffle and driver location as they used for their test.