Upgrading Boston Acoustics A200

[whatgive]

I am thinking about upgrading the woofers of my Boston Acoustics A200 with something that would enhance the bass a little more. The crossovers frequencies for these A200 are 450Hz at 6dB/octave and 3000Hz at 6dB and 12dB/octave and they are about 90~91db efficient. Cabinets are sealed design with dimension of 42" x 21" x 6 3/8" (external).

Which of the two woofers here will be a better match for my purpose: Dayton RS270S-8 10" or Dayton ST255-8. Looking at the chart, they are both very flat to 500hz and the ST255-8 is more efficient at 200~500hz from looking at the frequency graph.

Specs of ST255-8: Voice coil diameter: 2-1/2" * Voice coil inductance: 1.23 mH * Nominal impedance: 8 ohms * DC resistance: 6.2 ohms * Frequency response: 35-3,000 Hz * Magnet weight: 56 oz. * Fs: 34 Hz * SPL: 91.7 dB 1W/1m * Vas: 2.78 cu. ft. * Qms: 9.50 * Qes: .33 * Qts: .32 * Xmax: 5.5mm * http://partsexpress.com/pdf/ST255-8_specsheet.pdf

Specs of Dayton RS270S-8: *VCdia: 2" *Le: 1.15 mH *Znom: 8 ohms *Re: 6.9 ohms *Frequency range: 25-1,500 Hz *Fs: 26 Hz *SPL: 90.5 dB 2.83V/1m *Vas: 5.30 cu. ft. *Qms: 1.80 *Qes: .43 *Qts: .35 *Xmax: 6.6 mm - http://partsexpress.com/pdf/RS270S-8_specsheet.pdf

Thanks in advance.

[Chris Roemer]

I am thinking about upgrading the woofers of my Boston Acoustics A200 with something that would enhance the bass a little more. The crossovers frequencies for these A200 are 450Hz at 6dB/octave and 3000Hz at 6dB and 12dB/octave and they are about 90~91db efficient. Cabinets are sealed design with dimension of 42" x 21" x 6 3/8" (external).

Which of the two woofers here will be a better match for my purpose: Dayton RS270S-8 10" or Dayton ST255-8. Looking at the chart, they are both very flat to 500hz and the ST255-8 is more efficient at 200~500hz from looking at the frequency graph.

Specs of ST255-8: Voice coil diameter: 2-1/2" * Voice coil inductance: 1.23 mH * Nominal impedance: 8 ohms * DC resistance: 6.2 ohms * Frequency response: 35-3,000 Hz * Magnet weight: 56 oz. * Fs: 34 Hz * SPL: 91.7 dB 1W/1m * Vas: 2.78 cu. ft. * Qms: 9.50 * Qes: .33 * Qts: .32 * Xmax: 5.5mm * http://partsexpress.com/pdf/ST255-8_specsheet.pdf

Specs of Dayton RS270S-8: *VCdia: 2" *Le: 1.15 mH *Znom: 8 ohms *Re: 6.9 ohms *Frequency range: 25-1,500 Hz *Fs: 26 Hz *SPL: 90.5 dB 2.83V/1m *Vas: 5.30 cu. ft. *Qms: 1.80 *Qes: .43 *Qts: .35 *Xmax: 6.6 mm - http://partsexpress.com/pdf/RS270S-8_specsheet.pdf

Thanks in advance.

The Series II models low 40's in 1.5 cf, ported.
The RS will only reach 50Hz in 2 cf, sealed.
The AurumCantus 10"MKII can do low 40's in 2 cf, sealed.
The AC 10"F1 does low 30's in 2 cf, ported.

You CAN use the RS270 in 2 vented cf. With a 4"d x 15" long rear port, it should do low 40's.
Dayton's "Classic" 10" can reach the mid 30's in 2 cf with that same port.

Chris

[Steve H.]

I am thinking about upgrading the woofers of my Boston Acoustics A200 with something that would enhance the bass a little more. The crossovers frequencies for these A200 are 450Hz at 6dB/octave and 3000Hz at 6dB and 12dB/octave and they are about 90~91db efficient. Cabinets are sealed design with dimension of 42" x 21" x 6 3/8" (external).

Well, changing woofers is an option I guess, but is a lot of work. Chances are very good that you'll need to make modifications to the crossover too. I'd just about guarantee it, unless you get exceedingly lucky.

If the current woofers are in good condition, and the efficiency of these speakers is truly 90-91 dB, then they were made with no (or very little) baffle step compensation. You could try using them very near to the wall they are in front of, or you could use resistors to pad down the midrange and tweeter by a few dB. If you put the resistors *before* the other elements in the tweeter and mid crossovers, it shouldn't change the crossover points much. I'd start with about 2 ohms and see how you like it...

Just an idea.

[whatgive]

Steve and Chris, thanks for your help on this. I was hoping that I can just do an even swap without having to do any mod to the woofers, crossovers or cabinets. As i mentioned, cabinets are sealed and i really like the sound of my speakers, i just wish they can go down a little more; i guess i will just add on a subwoofer to augies the low end. Thanks again.

[Some Guy]

If the current woofers are in good condition, and the efficiency of these speakers is truly 90-91 dB, then they were made with no (or very little) baffle step compensation.

Look at the dimensions of the cabinets again and look up the layout of the A200 series.

The Boston Acoustics A200 series were designed taking into account the "real world listening room" research that Roy Allison had published (which I posted a thread about here several days back.) The Boston Acoustics solution was the extremely shallow cabinet, the low woofer mounting, the wide baffle and the chosen crossover frequencies as opposed to the Allison solution of triangular cabinets.

The woofer is located (for all practical purposes) at the intersection of the floor and wall so it is radiating into 1/4 sphere, not even 2pi space. These baffles are a full 21 inches wide. With the xover to the mid at 450 Hz, and the whole box being only 6 3/8 inches deep to begin with, there is no baffle step of any significant magnitude in need of correction.

You could try using them very near to the wall they are in front of...

The A200 series is designed explicitly for placement against the wall.

On edit...

I'm one of those odd ducks of the opinion that the great majority of loudspeakers in a great majority of home listening environments wind up being placed either against or within a few inches of the wall(s) and that is the condition that the majority of speakers (save those designed for our own explicit speaker locations and listening positions) ought to be designed for when taking the likely end use and resulting acoustic performance into account.

I'm not sure how many folks commonly have dedicated listening or home theatre rooms that are large enough to place speakers at least 3 to 4 feet away from the nearest wall boundary, but I don't know that I have ever walked into a private home and encountered such a thing.

Anyway, the A200 series is designed for floor placement against a wall. Moving them away from that position is going to adversely affect the bass power response and also introduce a steeper notch in that response than would exist when placed in the design location.

[johnastockman]

Just dropping a different woofer into your cabinets has a fairly good chance of sounding worse because the original crossover and box alignment was designed for the specific drivers used. If you like the sound quality of these speakers, your idea of adding a sub is probably the best choice to preserve the sound you now have and are familiar with.

John A.

[Some Guy]

Just dropping a different woofer into your cabinets has a fairly good chance of sounding worse because the original crossover and box alignment was designed for the specific drivers used. If you like the sound quality of these speakers, your idea of adding a sub is probably the best choice to preserve the sound you now have and are familiar with.

With that I concur without reservation.

[whatgive]

"If you like the sound quality of these speakers, your idea of adding a sub is probably the best choice to preserve the sound you now have and are familiar with. "


And I will do just that gentlemen. Thanks.

[johnastockman]

"If you like the sound quality of these speakers, your idea of adding a sub is probably the best choice to preserve the sound you now have and are familiar with. "


And I will do just that gentlemen. Thanks.

Do you have any ideas about a sub? DIY or store-bought? Lot's of options...of course, I recommend a DIY design, what with all those years I spent working at an audio emporium. Better value, better sound quality and a better cabinet. If you don't have a shop/tools/time to build an enclosure, PE has some very nice easy-to-assemble kits that will shame retail units that cost much more. I put together the 15" classic driver with the 240 watt amp kit for a friend. The performance per dollar ratio is amazing.

http://www.partsexpress.com/pe/showd...number=300-770

It's about 19" x 18" x 18.75", so it's not small, but if you need something smaller, there's many plans out there that can fit within your price range and size requirements.

John A.

[rotortiller]

I just replaced the woofers last year and did nothing to the crossover. I simply contacted BA and ordered the woofers. Although they physically fit perfectly they did appear different. However they now actually sound better and tighter than when the A200s were new. I had considered re-foaming the cone but this was easier and not very expensive. Things can be overcomplicated than they need be. Good luck.

RT