From making speakers for fellow enthusiasts c.1974-79, Impulse Loudspeakers became renowned as champions of horn-loading, at a time when horns were deeply unfashionable and insensitive stand-mount designs in the ascendancy. Following the apparent demise of the company c.1998 further information is hard to come by, so here is the fanboy tribute page the internet so obviously needs Typically designed around a truncated, modified exponential horn with the mouth facing the floor, Impulse garnered Design Council awards for what is usually an unwieldy form of enclosure. Yet appearances are the least part of the mix: these speakers boast a wonderfully tactile and incredibly well-controlled sound, capable of startling dynamics yet avoiding the stereotypical colourations of horn speakers. All models are considerably more sensitive than is typical in domestic hifi, which breathes life into the Impulse presentation of music. Though easy to drive they tend to be terribly revealing of partnering sources and amplification; more on this to follow. This page is in three parts: Model information, Driver/spares information and a request: if you have any information we can add to this page for the benefit of others interested in these fabulous speakers, please contact Martin. To start with, here's a brief history of horn speaker design Big and Low by Brian Taylor, designer of the Impulse range of speakers. Published in HiFi Answers, July 1989: Page 1 Page 2 Page 3 (GIF format, 150K per page)

Model Range: As far as we can determine, and in chronological order, speaker models produced were: HT1 H2a (and H2b, the 'pro' variant) H3 H1 H2 H4 H5 H6 H7 Ta'us Lali Kora Maya

2006:Brian Taylor has a new venture: Aspara Acoustics

IMPULSE models:

	Impulse HT1: The original monster Impulse speaker. A complex bifurcated, folded 'corner horn' Folded exponential bass horn, tractrix midhorn with driver open to rear and separate tweeter on sub-baffle. Sensitivity not given, but 10W given as an 'adequate for domestic use'. Drivers: 10" Peerless bass; 4" Isophon mid; 1" Coles dome tweeter. Multi-element series crossover (crossover points not given); 8ohm impedance Size: 36" H x 17" W x 19" D (900mm x 425mm x 500mm approx.) Finishes: Black grile, hessian, choice of 12 cloth inserts. Power handling 30W max.(!) Available 1982 - ? References: Brochure; Cover of HifI Answers March 1982 (JPEG format, 140K per page)
	Impulse H2a: The follow-up to the HT1. Folded bass horn, tractrix midhorn and tweeter loading. Sensitivity 96dB/W, 8ohms. A variant, the H2b, was available with higher power handling for studio and other professional use Drivers: not given; bandwidth 30Hz - 20Khz +/-5dB (dependant on location in room) Size: 45" H x 17" W x 20" D (1150mm x 425mm x 500mm approx.) Finishes: Mahogany, or others to order. Price: £1400; available 1982 - ? References: Advertisement; Brochure; Brief review in HifI Answers September 1982 (JPEG format, 150K per page)
	Impulse H3: A follow-up to the H2a, and a slight oddball. 3-way based on Seas drivers, with a sealed bass alignment, horn-loaded midrange arranged with mouth vertical, and tweeter at the top of a tall cabinet. Approx 91dB/W, 8ohms. Drivers: 8" Seas bass; 4.5" Seas mid; Seas plastic dome tweeter Crossover ponts: 400Hz; 4Khz Size: 1080mm H x 255mm W x 380mm D Weight: approx 36KG / 80lb each. Finishes: Teak, Walnut, Black Ash or Colourcore laminate (2 pairs made, 1 yellow, 1 blue) Available: 1985 - ?; List price £950 - 1150 depending on finish. Reviews:Jimmy Hughes in HiFi Answers, September 1985. Page 1 Page 2 (GIF format, 260K per page) Update (Jul 09): The Banana Splits, Impulse's own yellow review pair, still live! Andrew Hockley kindly forwarded some pictures of these, with the drivers now restored and sounding very good. H3 Front; H3 back; H3 crossover . Thanks, Andrew.
	Impulse H1: The big hit, and an evolution from the HT1, H2a and H3 models to the archectypal 'Impulse' truncated horn design. Folded exponential bass horn, tractrix midhorn with driver open to rear. Sensitivity 94dB/W, 8ohms. Drivers: 8.5" Seas bass; 4.5" Seas mid; Focal TD90K tweeter. Crossover ponts: 800Hz; 4Khz; 2nd order summed response. Size: 1100mm H x 350mm W x 685mm D Finishes/ cost: Approx. £2,800: built to order, customer-specified veneer with cloth inserts. Weight: if you have to ask... Available 1988 - ? Reviews:Jimmy Hughes in HiFi Answers, February 1989. It's a bit of an odd review, for a rave write-up... Page 1 Page 2 Page 3 Page 4 (GIF format, 120-220K per page)
	Impulse H2: Arguably the best of the lot. A derivative of the H1 which appears to have superceded it. Mostly handmade cabinet, same driver complement as H1, but a simplified bass horn folding leads to reduced cabinet volume with negligible loss of sensitivity and extension. Capable of stupendous bass quality and extension - although specified for cutoff at 40Hz, in-room measurements at home show extension flat down to 30Hz, -6dB at c.27Hz. Positioning close to the rear wall is recommended, but this speaker is remarkably unfussy about siting. Tractrix midhorn with driver open to rear and top, inverted-dome tweeter Sensitivity 95dB/W, 8ohm Drivers: 8.5" Seas bass; 4.5" Seas mid; Focal tweeter. Crossover ponts: 800Hz; 4Khz; 2nd order summed response. Size: 1160mm H x 270mm W x 480mm D Finishes: Rosewood or Oak with cloth inserts Weight: approx 65KG / 140lb each. Available: 1991-1996(?); list price c.£2,300 Reviews: 3 raves to pick from! (note these are all large images - 1024 pixels wide, GIF format, c. 250Kb) Jimmy Hughes in the Audiophile, June 1991:Page 1 Page 2 (B&W photo) What Hifi?, April 1992: Page 1 Page 2 What Hifi?, Summary: May 1992: May 92
	Impulse Ta'us: Effectively the H2 mk.2, this model had a curved front baffle which oversails the rest of the cabinet, making it slightly wider and taller than its predecessor although retaining the same driver complement. The rear of the mid-horn is enclosed in a sealed chanber stuffed with absorbant, a change from the H2. 94dB/W, 8ohm Drivers: 8.5" Seas bass; 4.5" Seas mid; Focal TD90K tweeter. Crossover ponts: 800Hz; 4.5Khz; 2nd order summed response. Size: 1210mm H x 300mm W x 480mm D Finishes: Painted cabinet with maple / Beech front baffle Weight: approx 65KG / 140lb each. Available: 1995-97; list price c.£3,000 Reviews: Cyberfi magazine, 1995 ; also see VMX.com online at http://www.vxm.com/21R.88.html
	Impulse H4: The replacement for the H3, re-styled to match the H1. 3-way based Seas and Focal drivers; bass loading unknown, but retained horn-loaded midrange with new Focal tweeter. Sensitivity unknown. Available: 1987-?; Built to order, £1100 Reviews:Jimmy Hughes in HiFi Answers, June 1987 H4 review (GIF format, 184K)
	Impulse H5: A 2-way based on lessons learned from the H1. 8.5" bass driver essentially shares its horn enclosure with the H2 design. 1" dome tweeter, horn-loaded. Drivers: 8.5" Seas bass; Searola tweeter. Crossover: - Size: 970mm H x 266mm W x 470mm D Weight: - Finish: Nextel Available: Not sure - but rare! Reviews: none available.
	Impulse H6: A compact two-way floorstander, and probably the most popular in the range - for good reasons! Punch well above their weight, and sound best a little way off the back wall. Drivers: 6.5" Seas bass; Focal TD90K tweeter. Crossover ponts: 4.5Khz, first order Size: 930mm H x 180mm W x 350mm D Weight: approx 25KG / 60lb each. Finishes: Painted; veneers available to special order Available: 1992-?; list price £1250 Reviews: Malcolm Steward and Jimmy Hughes in Audiophle, July 1992. Page 1 Page 2 Page 3 Page 4 Picture: H6 and H7 models, B&W advertisement , from Audiophile April 1994.
	Impulse H7: The very smallest horn incarnation! Tiny drivers in tiny-for-a-ho° cabinet, and some problems in crossover range means this is the least succesful of the Impulse designs. Small driver size leads to inevitably low sensitivity: 86dB/W, nominally 8ohms, but actually rather hard to drive - impedance dips to just 2ohms through midrange. Drivers: 3.5" bass; 1" metal dome tweeter. Crossover: ? Size: tiny! Weight: ? Available: 1994-? list price £785 Reviews: Paul Messenger in HiFi Choice, July 1994: H7 review
	Impulse Maya: A departure for Impulse, a 2-way sealed-box standmount. Following a change of leadership at Impulse, the company looked to diversify its speaker lineup. The Maya was the first, and possibly last, move in this direction. Approx 89dB/W, 8ohms, Drivers: Seas doped-paper bass/midrange; Seas metal-dome tweeter. Crossover: 'first order' Size: Standmount Weight: ? Finishes: Black ash with blond ash, cherry or rose front and top panels Available: 1998: 'under £700' Reviews: Jimmy Hughes, February 1998: Page 1 Page 2 Page 3
	Impulse Kora; Impulse Lali As the Ta'us is to the H2, the Kora and Lali are Mark 2 versions of the H7 and H6 respectively. Again, these models have a curved front baffle which oversails the rest of the cabinet, making them slightly wider and taller than its predecessor. Driver compliment and other information similar to H7 & H6, but updated crossovers and cabinet finishes. Kora: No reviews available - can you help?. Lali: Reviews: Chris Beeching in HifiNews & Record Review, October 1995. Page 1 Page 2

Driver information

Impulse used very high-quality SEAS and Focal drivers and here are the datasheets for the parts I have been able to verify. Should replacements ever be required, it gives a guide to use when looking for substitutes. Fortunately, although all these units have been superceded, newer models from SEAS and Focal which may be suitable will in all cases drop straight into the Impulse chassis cutouts - the driver chassis profiles and fixing PCDs are identical!

Bass: H1, H2, Ta'us
Seas 21F-WBX: 8.5" diecast magnesium chassis, coated paper cone 21 F-WBX.pdf (944K)
Note replacements, if required, should have Qts <0.3, Fs <35hz, sensitivity of 93dB (i.e as high as possible!). Suitable drop-in replacements such as the SEAS H333 (CA21REX) are unfortunately no longer in current production, though you might find a fairly close match from Vifa for the 215mm chassis. However - the GOOD NEWS- these units can easily have the foam surround replaced, and you can do it yourself as shown on the the H1/H2/Ta'us bass driver re-foam page

Bass: H5, H6
Seas part H3310: 6.5" diecast magnesium chassis, coated paper cone. No further info available.

Midrange: H2, Ta'us, probably H1 also
Seas 11F-M: 4.5" doped paper cone, diecast magnesium chassis. 11F-M.pdf (136K) otherwise known as the H143.pdf (136K)
Replacements, if required, should have Qts around 0.7 and sensitivity of 89-90dB. Using a higher sensitivity will require padding-down with a low-value series resistor owing to high sensitivity contributed by the Tractrix horn loading. Using a driver with significantly lower sensitivity will lead to a recessed midrange - there is no scope for raising the output of the midrange crossover (i.e. no existing series resistor in the crossover to remove).

Drop-in replacement is the SEAS MCA11, no longer in production (as of 2012) but occasionally found online as new-old-stock. However Good Hifi.nl can provide replacement surrounds for the SEAS 10F and 11F-M however, so refurbishment is practical - and you can do it yourself similar to the process shown on the the H1/H2/Ta'us bass driver re-foam page

Tweeter: H1, H2, Ta'us, H5
Focal TC90K: 1.35T magnet, kevlar inverted dome. TC90K.pdf (116K)
Well, not quite: The kevlar dome the Impulses used was a custom build using the kevlar/glassfibre dome in a 120-sized magnet and faceplate... which is 120 x 120mm, rather than the 90 x90mm of a TC90.
So - there is an easy replacement & upgrade for owners of speakers using this tweeter - substitute the Focal TC120TD5.pdf (136K) - if you can find them now that Focal has stopped supplying the aftermarket! This may require adjusting/adding an L-pad to reduce the treble level - the '120 is 2dB more sensitive than the '90K - try 1ohm resistor in series, with 22-ohm R across the 120s terminals, to begin with.

More information on cabinet construction and crossovers to follow.

If you have anything we can add to this page for the benefit of anyone interested in these fabulous speakers, please contact Martin.

www.acoustica.org.uk (opens new window) i>24.03.13: bass and midrange driver info corrected including refurbishment options