Can you recommend a good bass driver to pair with Seas coaxial (T18RE) in sealed box?

[JohnDaniel]

Hey friends, I've been lurking here for years and am finally taking the plunge for a build!

I am building a pair of near-field studio monitors. The Seas coax seem like the best solution: flat [enough] response without being too directional. I will not be building the Loki kit, but putting the drivers in a sealed enclosure. I primarily record jazz and produce digital music, which have a lot of lows, so I would like to add a bass driver. Madisound recommended the 9" Morel UW958, but that just breaks the bank. I would need to buy the drivers as a pair. I don't want to have a separate sub; I prefer to capture as much definition from the driver as I can by having it on axis with my ear. I also don't want to port the enclosure and muddy the mid to low spectrum, so that isn't an option either. I believe too much definition is lost in floor subs for applications as critical as mix engineering, so finding a cost-effective pair is my goal.

So I'm looking for accurate, musical, and affordable that would work well in a sealed application. If you have a good suggestion, I would be much obliged!

I'll be happy to provide some pics of the build when it's done!

[RockLeeEV]

If you haven't already ordered the seas coax, I'd strongly consider the KEF Q900 or Q700 drivers instead. They have a lot less diffraction etc going on thanks to the careful surround and phase plug designs.

As for a bass driver, you'll need something to cover the bandwidth from around 300hz to below 80hz for either driver. If box size isn't an issue, then I would consider a Dayton RS270. It is a metal cone driver so you might need to work the crossover a bit, but the result is exceptional.

P.S. a well designed ML-TL will most certainly not "muddy the low end"

[JohnDaniel]

Thanks Rock! I haven't ordered yet, and I'm not set in stone on anything. Those KEF Q900's look like a great option. When I search for them, all I can find is a tower speaker. Are they sold driver-only anywhere?

Space is an issue, I'd like to keep the box as small as I can, but I can build it up if need be. Ideally the monitors will be small enough to fit comfortably on my desk along side my monitor.

Here's a photo with my current speaker configuration (should be public).
https://www.facebook.com/photo.php?f...type=1&theater

[RockLeeEV]

Originally Posted by JohnDaniel

Thanks Rock! I haven't ordered yet, and I'm not set in stone on anything. Those KEF Q900's look like a great option. When I search for them, all I can find is a tower speaker. Are they sold driver-only anywhere?

Yes, there are a few places that sell the stand-alone drivers. Here's one:

KEF Q900

KEF Q100

KEF 4.5" Coaxial

Space is an issue, I'd like to keep the box as small as I can, but I can build it up if need be. Ideally the monitors will be small enough to fit comfortably on my desk along side my monitor.

Then a 10" driver with a large vas probably isn't the best choice. You'll take a bit of a hit on the sensitivity front, but this alpine:

Amazon.com: SWR-823D - Alpine 8" Type-R Dual 2-Ohm Subwoofer: Car Electronics

Will handle the desired frequency range nicely. In about .6 cu ft sealed you'll have an F3 of 52hz and the advanced motor and overall design will ensure excellent performance right up into the lower midrange.

You could probably use a linkwitz transform to extend response all the way to 20hz since it's nearfield. 1m SPL w/ 200w is about 89db @ 20hz (excursion limited), 100db @ 40hz, and 106db @ 100hz+

[JohnDaniel]

Thanks for your response! I've given it some thought, and I like the idea of a Kef coaxial driver. They make a fine product and it seems like a good choice. I've been trying to hear them locally but have been coming up short. I'm sure I'd get a good result with either - but I can't find a spec sheet for the Kef. It seems like I could make a more well-engineered speaker with the Seas coax considering I have all the specs to work with. You seem to know better resources for these things; do you have a spec sheet for the Kef Q900 and/or Q100? I've even tried contacting Kef directly but they do not respond.

One thing has changed, I have purchased a bigger desk to accommodate the recording/production equipment. Box size is no longer an issue and using a 10" bass driver isn't a problem.

I was looking at Zaph Audio and he seems to like SB Acoustics, what do you think of this 10" driver? I was thinking it mayn't handle the 100-300Hz range well, but it looks like those Kef drivers could be crossed over at 100 Hz pretty well. They have a surprisingly low frequency spec on the reconingspeakers project page.

SB Acoustics SB29SWNRX-S75 10" Woofer: Madisound Speaker Store

I don't know how that would stack up to your suggested 8" Alpine or 10" Dayton drivers. I was looking at other 8" drivers and found this Tang Band, a name I see come up from time to time as high quality.

Tang Band W8-1747A 8" Aluminum Cone Subwoofer 264-892

Of course accuracy is the goal, so it's tough to tell since so many woofer-heads go for the high SPLs.

Thanks for any further advice you can offer!

[mdocod]

Dollar for dollar, I think it's very hard to beat the Dayton RS series for your application. Most of them are very usable up into the lower mid-range for flexible x-over options. The very powerful motors, long linear excursion, and high thermal limits translate to a lot of possible box alignments that can either use box size or amplification power to achieve the desired results (with EQ/transform).

[RockLeeEV]

Originally Posted by JohnDaniel

I'm sure I'd get a good result with either - but I can't find a spec sheet for the Kef. It seems like I could make a more well-engineered speaker with the Seas coax considering I have all the specs to work with.

How so? Without measuring any drivers yourself, in your box design, at your altitude and temperature, you won't be setting yourself up for great results. Especially when we're talking about a 3-way.

Spec sheet TS Parameters and response graphs are nice but they are wholely insufficent IMO for building a high fidelity speaker. The resolution on supplied response graphs will never approximate your hearing and TSP are widely known to never be spot on either.

Without the drivers in your hand - whether seas, kef, or TAD... you won't have a great time designing a speaker.

I was looking at Zaph Audio and he seems to like SB Acoustics, what do you think of this 10" driver?

I'll get back to you later on the SB although they are nice drivers.

The number one key to a good bass driver is a good motor and suspension design with faraday sleeves/rings, controlled BL factor, sufficient linear excursion (especially for sealed), and good thermal compression behaviour. For a midbass you really need unrolled off response at least an octave above the crossover point with a controlled Le(x) curve.

Having a good bass driver alone garuntees nothing though in real rooms. SQ in rooms is dominated by frequency response, not harmonic distortion. For good FR you truly need freedom from compression no matter the signal. Going sealed makes this quite the task.

The alpine subwoofers truly are fine drivers with low inductance and lots of linear excursion to match. For sealed alignments it'd be tough finding something more suited. There's lots of nice hifi drivers optimized for vented alignments but few that will work as great sealed.

The daytons are truly sweet as well with triple shorting ring klippel optimized motors. Alpine does have a 10" driver in that same line as well. The Usher 1001b is another choice that you can't go wrong with.

I was thinking it mayn't handle the 100-300Hz range well, but it looks like those Kef drivers could be crossed over at 100 Hz pretty well.

Best results from any coaxial come from aggressively limiting cone motion because the cone is a waveguide. I would cross it at over 300hz. Passive crossovers are not an option below ~300hz anyways because of dcr in air core inductors. If you're doing a line level / active crossover then you get a bit more freedom but still need careful examination of phase and frequency response.

They have a surprisingly low frequency spec on the reconingspeakers project page.

Sure it will dig deep but it's just not necessary if you've got a more suited driver for the task. The less asked of the mid in the bass, the more composed it should stay in the mids and treble. After building a box I would try to roll the mid off near or above the -3db point of the baffle step.

I was looking at other 8" drivers and found this Tang Band, a name I see come up from time to time as high quality.

Tang Band W8-1747A 8" Aluminum Cone Subwoofer 264-892

Ill get back to you on this as well.

[RockLeeEV]

Originally Posted by JohnDaniel

SB Acoustics SB29SWNRX-S75 10" Woofer: Madisound Speaker Store

...I don't know how that would stack up to your suggested 8" Alpine or 10" Dayton drivers. ..

Le = 3mH for a 6 ohm driver = 0.5mH/ohm .. this is visible as an inductance hump and steep rolloff in the frequency response.

How would it stack up?

Well, in comparision,

Dayton RS 270 Le = 0.9 mH for an 8 ohm driver = 0.1125 mH/ohm
Usher 1001b Le = 0.92mH for an 8 ohm driver = 0.115mH/ohm
Alpine 823 Le = 0.87mH for a 4 ohm driver = 0.2175 mH/ohm

To me, those particular drivers seem much more suited for use as actual woofers, and I suspect are more linear drivers on a whole anyways. IMO immediate rolloff in response should be done by air core inductors, not cored inductors (IE voice coils).

And you really want flexibility. a 100hz crossover might be a plausible goal but if you're restricted to it then you're not going to get flexible results.

You really want drivers with very low inductance for use as woofers. For sub < 60hz maybe there's other priorities but for SQ the woofer needs to have very low IMD, FMD, 4HD/5HD, etc.

I can't recommend the SB unit as anything but a subwoofer, and I feel there's some subwoofers that are way better.

Another driver that you should strongly consider, is the CSS SDX-10. The idea of using it as a woofer only occurred to me a few days ago and I made a thread about it. And with 18mm linear xmax, it will reproduce just about anything you can throw at it nearfield. It's a TRUE low distortion subwoofer.

Tang Band W8-1747A 8" Aluminum Cone Subwoofer 264-892

The impedance trace shows a resonance near 110hz that shows up in the frequency response. Dunno the subjective consequences but I'd be iffy on it.

[HYPERTUNE]

Another sub suitable for lower midrange is the seas l26roy. Good efficiency, plenty of excursion and low distortion right up into the midrange. Oh and the colour of the cone looks like it would match the kef also

[bobodioulasso]

I wonder how low mid will sound considering the 107g mms.